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Sample records for allosteric signal transmission

  1. Detection of allosteric signal transmission by information-theoretic analysis of protein dynamics

    PubMed Central

    Pandini, Alessandro; Fornili, Arianna; Fraternali, Franca; Kleinjung, Jens

    2012-01-01

    Allostery offers a highly specific way to modulate protein function. Therefore, understanding this mechanism is of increasing interest for protein science and drug discovery. However, allosteric signal transmission is difficult to detect experimentally and to model because it is often mediated by local structural changes propagating along multiple pathways. To address this, we developed a method to identify communication pathways by an information-theoretical analysis of molecular dynamics simulations. Signal propagation was described as information exchange through a network of correlated local motions, modeled as transitions between canonical states of protein fragments. The method was used to describe allostery in two-component regulatory systems. In particular, the transmission from the allosteric site to the signaling surface of the receiver domain NtrC was shown to be mediated by a layer of hub residues. The location of hubs preferentially connected to the allosteric site was found in close agreement with key residues experimentally identified as involved in the signal transmission. The comparison with the networks of the homologues CheY and FixJ highlighted similarities in their dynamics. In particular, we showed that a preorganized network of fragment connections between the allosteric and functional sites exists already in the inactive state of all three proteins.—Pandini, A., Fornili, A., Fraternali, F., Kleinjung, J. Detection of allosteric signal transmission by information-theoretic analysis of protein dynamics. PMID:22071506

  2. Detection of allosteric signal transmission by information-theoretic analysis of protein dynamics.

    PubMed

    Pandini, Alessandro; Fornili, Arianna; Fraternali, Franca; Kleinjung, Jens

    2012-02-01

    Allostery offers a highly specific way to modulate protein function. Therefore, understanding this mechanism is of increasing interest for protein science and drug discovery. However, allosteric signal transmission is difficult to detect experimentally and to model because it is often mediated by local structural changes propagating along multiple pathways. To address this, we developed a method to identify communication pathways by an information-theoretical analysis of molecular dynamics simulations. Signal propagation was described as information exchange through a network of correlated local motions, modeled as transitions between canonical states of protein fragments. The method was used to describe allostery in two-component regulatory systems. In particular, the transmission from the allosteric site to the signaling surface of the receiver domain NtrC was shown to be mediated by a layer of hub residues. The location of hubs preferentially connected to the allosteric site was found in close agreement with key residues experimentally identified as involved in the signal transmission. The comparison with the networks of the homologues CheY and FixJ highlighted similarities in their dynamics. In particular, we showed that a preorganized network of fragment connections between the allosteric and functional sites exists already in the inactive state of all three proteins. PMID:22071506

  3. Molecular Dynamics Investigation of a Mechanism of Allosteric Signal Transmission in Ribosomes.

    PubMed

    Makarov, G I; Golovin, A V; Sumbatyan, N V; Bogdanov, A A

    2015-08-01

    The ribosome is a molecular machine that synthesizes all cellular proteins via translation of genetic information encoded in polynucleotide chain of messenger RNA. Transition between different stages of the ribosome working cycle is strictly coordinated by changes in structure and mutual position both of subunits of the ribosome and its ligands. Therein, information regarding structural transformations is transmitted between functional centers of the ribosome through specific signals. Usually, functional centers of ribosomes are located at a distance reaching up to several tens of angstroms, and it is believed that such signals are transduced allosterically. In our study, we attempted to answer the question of how allosteric signal can be transmitted from one of the so-called sensory elements of ribosomal tunnel (RT) to the peptidyl transferase center (PTC). A segment of RT wall from the E. coli ribosome composed of nucleotide residues A2058, A2059, m(2)A2503, G2061, A2062, and C2063 of its 23S rRNA was examined by molecular dynamics simulations. It was found that a potential signal transduction pathway A2058-C2063 acted as a dynamic ensemble of interdependent conformational states, wherein cascade-like changes can occur. It was assumed that structural rearrangement in the A2058-C2063 RT segment results in reversible inactivation of PTC due to a strong stacking contact between functionally important U2585 residue of the PTC and nucleotide residue C2063. A potential role for the observed conformational transition in the A2058-C2063 segment for regulating ribosome activity is discussed. PMID:26547073

  4. Intramolecular signal transmission in enterobacterial aspartate transcarbamylases II. Engineering co-operativity and allosteric regulation in the aspartate transcarbamylase of Erwinia herbicola.

    PubMed

    Cunin, R; Rani, C S; Van Vliet, F; Wild, J R; Wales, M

    1999-12-17

    The aspartate transcarbamylase (ATCase) from Erwinia herbicola differs from the other investigated enterobacterial ATCases by its absence of homotropic co-operativity toward the substrate aspartate and its lack of response to ATP which is an allosteric effector (activator) of this family of enzymes. Nevertheless, the E. herbicola ATCase has the same quaternary structure, two trimers of catalytic chains with three dimers of regulatory chains ((c3)2(r2)3), as other enterobacterial ATCases and shows extensive primary structure conservation. In (c3)2(r2)3 ATCases, the association of the catalytic subunits c3 with the regulatory subunits r2 is responsible for the establishment of positive co-operativity between catalytic sites for the binding of aspartate and it dictates the pattern of allosteric response toward nucleotide effectors. Alignment of the primary sequence of the regulatory polypeptides from the E. herbicola and from the paradigmatic Escherichia coli ATCases reveals major blocks of divergence, corresponding to discrete structural elements in the E. coli enzyme. Chimeric ATCases were constructed by exchanging these blocks of divergent sequence between these two ATCases. It was found that the amino acid composition of the outermost beta-strand of a five-stranded beta-sheet in the effector-binding domain of the regulatory polypeptide is responsible for the lack of co-operativity and response to ATP of the E. herbicola ATCase. A novel structural element involved in allosteric signal recognition and transmission in this family of ATCases was thus identified. PMID:10600394

  5. Signal peptides are allosteric activators of the protein translocase.

    PubMed

    Gouridis, Giorgos; Karamanou, Spyridoula; Gelis, Ioannis; Kalodimos, Charalampos G; Economou, Anastassios

    2009-11-19

    Extra-cytoplasmic polypeptides are usually synthesized as 'preproteins' carrying amino-terminal, cleavable signal peptides and secreted across membranes by translocases. The main bacterial translocase comprises the SecYEG protein-conducting channel and the peripheral ATPase motor SecA. Most proteins destined for the periplasm and beyond are exported post-translationally by SecA. Preprotein targeting to SecA is thought to involve signal peptides and chaperones like SecB. Here we show that signal peptides have a new role beyond targeting: they are essential allosteric activators of the translocase. On docking on their binding groove on SecA, signal peptides act in trans to drive three successive states: first, 'triggering' that drives the translocase to a lower activation energy state; second, 'trapping' that engages non-native preprotein mature domains docked with high affinity on the secretion apparatus; and third, 'secretion' during which trapped mature domains undergo several turnovers of translocation in segments. A significant contribution by mature domains renders signal peptides less critical in bacterial secretory protein targeting than currently assumed. Rather, it is their function as allosteric activators of the translocase that renders signal peptides essential for protein secretion. A role for signal peptides and targeting sequences as allosteric activators may be universal in protein translocases. PMID:19924216

  6. AIM for Allostery: Using the Ising Model to Understand Information Processing and Transmission in Allosteric Biomolecular Systems

    PubMed Central

    LeVine, Michael V.; Weinstein, Harel

    2015-01-01

    In performing their biological functions, molecular machines must process and transmit information with high fidelity. Information transmission requires dynamic coupling between the conformations of discrete structural components within the protein positioned far from one another on the molecular scale. This type of biomolecular “action at a distance” is termed allostery. Although allostery is ubiquitous in biological regulation and signal transduction, its treatment in theoretical models has mostly eschewed quantitative descriptions involving the system's underlying structural components and their interactions. Here, we show how Ising models can be used to formulate an approach to allostery in a structural context of interactions between the constitutive components by building simple allosteric constructs we termed Allosteric Ising Models (AIMs). We introduce the use of AIMs in analytical and numerical calculations that relate thermodynamic descriptions of allostery to the structural context, and then show that many fundamental properties of allostery, such as the multiplicative property of parallel allosteric channels, are revealed from the analysis of such models. The power of exploring mechanistic structural models of allosteric function in more complex systems by using AIMs is demonstrated by building a model of allosteric signaling for an experimentally well-characterized asymmetric homodimer of the dopamine D2 receptor. PMID:26594108

  7. Modular architecture of protein structures and allosteric communications: potential implications for signaling proteins and regulatory linkages

    PubMed Central

    del Sol, Antonio; Araúzo-Bravo, Marcos J; Amoros, Dolors; Nussinov, Ruth

    2007-01-01

    Background Allosteric communications are vital for cellular signaling. Here we explore a relationship between protein architectural organization and shortcuts in signaling pathways. Results We show that protein domains consist of modules interconnected by residues that mediate signaling through the shortest pathways. These mediating residues tend to be located at the inter-modular boundaries, which are more rigid and display a larger number of long-range interactions than intra-modular regions. The inter-modular boundaries contain most of the residues centrally conserved in the protein fold, which may be crucial for information transfer between amino acids. Our approach to modular decomposition relies on a representation of protein structures as residue-interacting networks, and removal of the most central residue contacts, which are assumed to be crucial for allosteric communications. The modular decomposition of 100 multi-domain protein structures indicates that modules constitute the building blocks of domains. The analysis of 13 allosteric proteins revealed that modules characterize experimentally identified functional regions. Based on the study of an additional functionally annotated dataset of 115 proteins, we propose that high-modularity modules include functional sites and are the basic functional units. We provide examples (the Gαs subunit and P450 cytochromes) to illustrate that the modular architecture of active sites is linked to their functional specialization. Conclusion Our method decomposes protein structures into modules, allowing the study of signal transmission between functional sites. A modular configuration might be advantageous: it allows signaling proteins to expand their regulatory linkages and may elicit a broader range of control mechanisms either via modular combinations or through modulation of inter-modular linkages. PMID:17531094

  8. Backbone NMR reveals allosteric signal transduction networks in the β1-adrenergic receptor.

    PubMed

    Isogai, Shin; Deupi, Xavier; Opitz, Christian; Heydenreich, Franziska M; Tsai, Ching-Ju; Brueckner, Florian; Schertler, Gebhard F X; Veprintsev, Dmitry B; Grzesiek, Stephan

    2016-02-11

    G protein-coupled receptors (GPCRs) are physiologically important transmembrane signalling proteins that trigger intracellular responses upon binding of extracellular ligands. Despite recent breakthroughs in GPCR crystallography, the details of ligand-induced signal transduction are not well understood owing to missing dynamical information. In principle, such information can be provided by NMR, but so far only limited data of functional relevance on few side-chain sites of eukaryotic GPCRs have been obtained. Here we show that receptor motions can be followed at virtually any backbone site in a thermostabilized mutant of the turkey β1-adrenergic receptor (β1AR). Labelling with [(15)N]valine in a eukaryotic expression system provides over twenty resolved resonances that report on structure and dynamics in six ligand complexes and the apo form. The response to the various ligands is heterogeneous in the vicinity of the binding pocket, but gets transformed into a homogeneous readout at the intracellular side of helix 5 (TM5), which correlates linearly with ligand efficacy for the G protein pathway. The effect of several pertinent, thermostabilizing point mutations was assessed by reverting them to the native sequence. Whereas the response to ligands remains largely unchanged, binding of the G protein mimetic nanobody NB80 and G protein activation are only observed when two conserved tyrosines (Y227 and Y343) are restored. Binding of NB80 leads to very strong spectral changes throughout the receptor, including the extracellular ligand entrance pocket. This indicates that even the fully thermostabilized receptor undergoes activating motions in TM5, but that the fully active state is only reached in presence of Y227 and Y343 by stabilization with a G protein-like partner. The combined analysis of chemical shift changes from the point mutations and ligand responses identifies crucial connections in the allosteric activation pathway, and presents a general experimental

  9. Global Low Frequency Protein Motions in Long-Range Allosteric Signaling

    NASA Astrophysics Data System (ADS)

    McLeish, Tom; Rogers, Thomas; Townsend, Philip; Burnell, David; Pohl, Ehmke; Wilson, Mark; Cann, Martin; Richards, Shane; Jones, Matthew

    2015-03-01

    We present a foundational theory for how allostery can occur as a function of low frequency dynamics without a change in protein structure. Elastic inhomogeneities allow entropic ``signalling at a distance.'' Remarkably, many globular proteins display just this class of elastic structure, in particular those that support allosteric binding of substrates (long-range co-operative effects between the binding sites of small molecules). Through multi-scale modelling of global normal modes we demonstrate negative co-operativity between the two cAMP ligands without change to the mean structure. Crucially, the value of the co-operativity is itself controlled by the interactions around a set of third allosteric ``control sites.'' The theory makes key experimental predictions, validated by analysis of variant proteins by a combination of structural biology and isothermal calorimetry. A quantitative description of allostery as a free energy landscape revealed a protein ``design space'' that identified the key inter- and intramolecular regulatory parameters that frame CRP/FNR family allostery. Furthermore, by analyzing naturally occurring CAP variants from diverse species, we demonstrate an evolutionary selection pressure to conserve residues crucial for allosteric control. The methodology establishes the means to engineer allosteric mechanisms that are driven by low frequency dynamics.

  10. Allosteric and Biased G Protein-Coupled Receptor Signaling Regulation: Potentials for New Therapeutics

    PubMed Central

    Khoury, Etienne; Clément, Stéphanie; Laporte, Stéphane A.

    2014-01-01

    G protein-coupled receptors (GPCRs) are seven-transmembrane proteins that participate in many aspects of the endocrine function and are important targets for drug development. They transduce signals mainly, but not exclusively, via hetero-trimeric G proteins, leading to a diversity of intracellular signaling cascades. Ligands binding at the hormone orthosteric sites of receptors have been classified as agonists, antagonists, and/or inverse agonists based on their ability to mainly modulate G protein signaling. Accumulating evidence also indicates that such ligands, alone or in combination with other ones such as those acting outside the orthosteric hormone binding sites (e.g., allosteric modulators), have the ability to selectively engage subsets of signaling responses as compared to the natural endogenous ligands. Such modes of functioning have been variously referred to as “functional selectivity” or “ligand-biased signaling.” In this review, we provide an overview of the current knowledge regarding GPCR-biased signaling and their functional regulation with a focus on the evolving concept that receptor domains can also be targeted to allosterically bias signaling, and discuss the usefulness of such modes of regulation for the design of more efficient therapeutics. PMID:24847311

  11. Differential pathway coupling efficiency of the activated insulin receptor drives signaling selectivity by xmeta, an allosteric partial agonist antibody

    Technology Transfer Automated Retrieval System (TEKTRAN)

    XMetA, an anti-insulin receptor (IR) monoclonal antibody, is an allosteric partial agonist of the IR. We have previously reported that XMetA activates the “metabolic-biased” Akt kinase signaling pathway while having little or no effect on the “mitogenic” MAPK signaling pathwayof ERK 1/2. To inves...

  12. Allosteric β-propeller signalling in TolB and its manipulation by translocating colicins

    PubMed Central

    Bonsor, Daniel A; Hecht, Oliver; Vankemmelbeke, Mireille; Sharma, Amit; Krachler, Anne Marie; Housden, Nicholas G; Lilly, Katie J; James, Richard; Moore, Geoffrey R; Kleanthous, Colin

    2009-01-01

    The Tol system is a five-protein assembly parasitized by colicins and bacteriophages that helps stabilize the Gram-negative outer membrane (OM). We show that allosteric signalling through the six-bladed β-propeller protein TolB is central to Tol function in Escherichia coli and that this is subverted by colicins such as ColE9 to initiate their OM translocation. Protein–protein interactions with the TolB β-propeller govern two conformational states that are adopted by the distal N-terminal 12 residues of TolB that bind TolA in the inner membrane. ColE9 promotes disorder of this ‘TolA box' and recruitment of TolA. In contrast to ColE9, binding of the OM lipoprotein Pal to the same site induces conformational changes that sequester the TolA box to the TolB surface in which it exhibits little or no TolA binding. Our data suggest that Pal is an OFF switch for the Tol assembly, whereas colicins promote an ON state even though mimicking Pal. Comparison of the TolB mechanism to that of vertebrate guanine nucleotide exchange factor RCC1 suggests that allosteric signalling may be more prevalent in β-propeller proteins than currently realized. PMID:19696740

  13. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation.

    PubMed

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-09-18

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  14. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

    PubMed Central

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-01-01

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  15. Allosteric modulation of metabotropic glutamate receptor 4 activates IDO1-dependent, immunoregulatory signaling in dendritic cells

    PubMed Central

    Volpi, Claudia; Mondanelli, Giada; Pallotta, Maria T.; Vacca, Carmine; Iacono, Alberta; Gargaro, Marco; Albini, Elisa; Bianchi, Roberta; Belladonna, Maria L.; Celanire, Sylvain; Mordant, Céline; Heroux, Madeleine; Royer-Urios, Isabelle; Schneider, Manfred; Vitte, Pierre-Alain; Cacquevel, Mathias; Galibert, Laurent; Poli, Sonia-Maria; Solari, Aldo; Bicciato, Silvio; Calvitti, Mario; Antognelli, Cinzia; Puccetti, Paolo; Orabona, Ciriana; Fallarino, Francesca; Grohmann, Ursula

    2016-01-01

    Metabotropic glutamate receptor 4 (mGluR4) possesses immune modulatory properties in vivo, such that a positive allosteric modulator (PAM) of the receptor confers protection on mice with relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE). ADX88178 is a newly-developed, one such mGluR4 modulator with high selectivity, potency, and optimized pharmacokinetics. Here we found that application of ADX88178 in the RR-EAE model system converted disease into a form of mild—yet chronic—neuroinflammation that remained stable for over two months after discontinuing drug treatment. In vitro, ADX88178 modulated the cytokine secretion profile of dendritic cells (DCs), increasing production of tolerogenic IL-10 and TGF-β. The in vitro effects required activation of a Gi-independent, alternative signaling pathway that involved phosphatidylinositol-3-kinase (PI3K), Src kinase, and the signaling activity of indoleamine 2,3-dioxygenase 1 (IDO1). A PI3K inhibitor as well as small interfering RNA targeting Ido1—but not pertussis toxin, which affects Gi protein-dependent responses—abrogated the tolerogenic effects of ADX88178-conditioned DCs in vivo. Thus our data indicate that, in DCs, highly selective and potent mGluR4 PAMs such as ADX88178 may activate a Gi-independent, long-lived regulatory pathway that could be therapeutically exploited in chronic autoimmune diseases such as multiple sclerosis. PMID:26522434

  16. Biased signalling and allosteric machines: new vistas and challenges for drug discovery.

    PubMed

    Kenakin, Terry P

    2012-03-01

    Seven transmembrane receptors (7TMRs) are nature's prototype allosteric proteins made to bind molecules at one location to subsequently change their shape to affect the binding of another molecule at another location. This paper attempts to describe the divergent 7TMR behaviours (i.e. third party allostery, receptor oligomerization, biased agonism) observed in pharmacology in terms of a homogeneous group of allosteric behaviours. By considering the bodies involved as a vector defined by a modulator, conduit and guest, these activities can all be described by a simple model of functional allostery made up of the Ehlert allosteric model and the Black/Leff operational model. It will be shown how this model yields parameters that can be used to characterize the activity of any ligand or protein producing effect through allosteric interaction with a 7TMR. PMID:22023017

  17. The condensed chromatin fiber: an allosteric chemo-mechanical machine for signal transduction and genome processing

    NASA Astrophysics Data System (ADS)

    Lesne, Annick; Bécavin, Christophe; Victor, Jean–Marc

    2012-02-01

    Allostery is a key concept of molecular biology which refers to the control of an enzyme activity by an effector molecule binding the enzyme at another site rather than the active site (allos = other in Greek). We revisit here allostery in the context of chromatin and argue that allosteric principles underlie and explain the functional architecture required for spacetime coordination of gene expression at all scales from DNA to the whole chromosome. We further suggest that this functional architecture is provided by the chromatin fiber itself. The structural, mechanical and topological features of the chromatin fiber endow chromosomes with a tunable signal transduction from specific (or nonspecific) effectors to specific (or nonspecific) active sites. Mechanical constraints can travel along the fiber all the better since the fiber is more compact and regular, which speaks in favor of the actual existence of the (so-called 30 nm) chromatin fiber. Chromatin fiber allostery reconciles both the physical and biochemical approaches of chromatin. We illustrate this view with two supporting specific examples. Moreover, from a methodological point of view, we suggest that the notion of chromatin fiber allostery is particularly relevant for systemic approaches. Finally we discuss the evolutionary power of allostery in the context of chromatin and its relation to modularity.

  18. Allosteric signalling in the outer membrane translocation domain of PapC usher

    PubMed Central

    Farabella, Irene; Pham, Thieng; Henderson, Nadine S; Geibel, Sebastian; Phan, Gilles; Thanassi, David G; Delcour, Anne H; Waksman, Gabriel; Topf, Maya

    2014-01-01

    PapC ushers are outer-membrane proteins enabling assembly and secretion of P pili in uropathogenic E. coli. Their translocation domain is a large β-barrel occluded by a plug domain, which is displaced to allow the translocation of pilus subunits across the membrane. Previous studies suggested that this gating mechanism is controlled by a β-hairpin and an α-helix. To investigate the role of these elements in allosteric signal communication, we developed a method combining evolutionary and molecular dynamics studies of the native translocation domain and mutants lacking the β-hairpin and/or the α-helix. Analysis of a hybrid residue interaction network suggests distinct regions (residue ‘communities’) within the translocation domain (especially around β12–β14) linking these elements, thereby modulating PapC gating. Antibiotic sensitivity and electrophysiology experiments on a set of alanine-substitution mutants confirmed functional roles for four of these communities. This study illuminates the gating mechanism of PapC ushers and its importance in maintaining outer-membrane permeability. DOI: http://dx.doi.org/10.7554/eLife.03532.001 PMID:25271373

  19. Investigating the allosteric reverse signalling of PARP inhibitors with microsecond molecular dynamic simulations and fluorescence anisotropy.

    PubMed

    Marchand, Jean-Rémy; Carotti, Andrea; Passeri, Daniela; Filipponi, Paolo; Liscio, Paride; Camaioni, Emidio; Pellicciari, Roberto; Gioiello, Antimo; Macchiarulo, Antonio

    2014-10-01

    The inhibition of the poly(ADP-ribose) polymerase (PARP) family members is a strategy pursued for the development of novel therapeutic agents in a range of diseases, including stroke, cardiac ischemia, cancer, inflammation and diabetes. Even though some PARP-1 inhibitors have advanced to clinical setting for cancer therapy, a great deal of attention is being devoted to understand the polypharmacology of current PARP inhibitors. Besides blocking the catalytic activity, recent works have shown that some PARP inhibitors exhibit a poisoning activity, by trapping the enzyme at damaged sites of DNA and forming cytotoxic complexes. In this study we have used microsecond molecular dynamics to study the allosteric reverse signalling that is at the basis of such an effect. We show that Olaparib, but not Veliparib and HYDAMTIQ, is able to induce a specific conformational drift of the WGR domain of PARP-1, which stabilizes PARP-1/DNA complex through the locking of several salt bridge interactions. Fluorescence anisotropy assays support such a mechanism, providing the first experimental evidence that HYDAMTIQ, a potent PARP inhibitor with neuroprotective properties, is less potent than Olaparib to trap PARP-1/DNA complex. PMID:25062913

  20. The allosteric behavior of Fur mediates oxidative stress signal transduction in Helicobacter pylori.

    PubMed

    Pelliciari, Simone; Vannini, Andrea; Roncarati, Davide; Danielli, Alberto

    2015-01-01

    The microaerophilic gastric pathogen Helicobacter pylori is exposed to oxidative stress originating from the aerobic environment, the oxidative burst of phagocytes and the formation of reactive oxygen species, catalyzed by iron excess. Accordingly, the expression of genes involved in oxidative stress defense have been repeatedly linked to the ferric uptake regulator Fur. Moreover, mutations in the Fur protein affect the resistance to metronidazole, likely due to loss-of-function in the regulation of genes involved in redox control. Although many advances in the molecular understanding of HpFur function were made, little is known about the mechanisms that enable Fur to mediate the responses to oxidative stress. Here we show that iron-inducible, apo-Fur repressed genes, such as pfr and hydA, are induced shortly after oxidative stress, while their oxidative induction is lost in a fur knockout strain. On the contrary, holo-Fur repressed genes, such as frpB1 and fecA1, vary modestly in response to oxidative stress. This indicates that the oxidative stress signal specifically targets apo-Fur repressed genes, rather than impairing indiscriminately the regulatory function of Fur. Footprinting analyses showed that the oxidative signal strongly impairs the binding affinity of Fur toward apo-operators, while the binding toward holo-operators is less affected. Further evidence is presented that a reduced state of Fur is needed to maintain apo-repression, while oxidative conditions shift the preferred binding architecture of Fur toward the holo-operator binding conformation, even in the absence of iron. Together the results demonstrate that the allosteric regulation of Fur enables transduction of oxidative stress signals in H. pylori, supporting the concept that apo-Fur repressed genes can be considered oxidation inducible Fur regulatory targets. These findings may have important implications in the study of H. pylori treatment and resistance to antibiotics. PMID:26347726

  1. Allosteric Activation of the RNF146 Ubiquitin Ligase by a Poly(ADP-ribosyl)ation Signal

    PubMed Central

    DaRosa, Paul A.; Wang, Zhizhi; Jiang, Xiaomo; Pruneda, Jonathan N.; Cong, Feng; Klevit, Rachel E.; Xu, Wenqing

    2014-01-01

    Protein poly(ADP-ribosyl)ation (PARylation) plays a role in diverse cellular processes such as DNA repair, transcription, Wnt signaling, and cell death1–6. Recent studies have shown that PARylation can serve as a signal for the polyubiquitination and degradation of several critical regulatory proteins, including Axin and 3BP2 (refs 7–9). The RING-type E3 ubiquitin ligase RNF146 (a.k.a. Iduna) is responsible for PARylation-dependent ubiquitination (PARdU)10–12. Here we provide a structural basis for RNF146 catalyzed PARdU and how PARdU specificity is achieved. First, we show that iso-ADPr, the smallest internal poly(ADP-ribose) (PAR) structural unit, binds between the WWE and RING domains of RNF146 and functions as an allosteric signal that switches the RING domain from a catalytically inactive state to an active one. In the absence of PAR, the RING domain is unable to efficiently bind and activate an E2. Binding of PAR/iso-ADPr induces a major conformational change that creates a functional RING structure. Thus RNF146 represents a new mechanistic class of RING E3 ligases whose activities are regulated by non-covalent ligand binding, which may provide a template for designing inducible protein-degradation systems. Second, we found that RNF146 directly interacts with the PAR polymerase tankyrase (TNKS). Disruption of the RNF146/TNKS interaction inhibits turnover of the substrate Axin in cells. Thus, both substrate PARylation and PARdU are catalyzed by enzymes within the same protein complex, and PARdU substrate specificity may be primarily determined by the substrate-TNKS interaction. We propose that maintenance of unliganded RNF146 in an inactive state may serve to maintain the stability of the RNF146-TNKS complex, which in turn regulates the homeostasis of PARdU activity in the cell. PMID:25327252

  2. Image signal transmission with Airy beams.

    PubMed

    Liang, Yi; Hu, Yi; Song, Daohong; Lou, Cibo; Zhang, Xinzheng; Chen, Zhigang; Xu, Jingjun

    2015-12-01

    We propose and demonstrate an approach for image signal transmission based on self-accelerating Airy beams. The spatial information is encoded in the Fourier space through a 4-f telescope system, which can circumvent obstacles to realize a self-bending signal transmission. Furthermore, the information can be retrieved from the Airy beams after propagation through a disordered scattering medium. Our experimental results agree well with theoretical predictions. PMID:26625082

  3. Differential pathway coupling efficiency of the activated insulin receptor drives signaling selectivity by XMetA, an allosteric partial agonist antibody

    Technology Transfer Automated Retrieval System (TEKTRAN)

    XMetA, an anti-insulin receptor (IR) monoclonal antibody, is an allosteric partial agonist of the IR. We have previously reported that XMetA activates the “metabolic-biased” Akt kinase signaling pathway while having little or no effect on the “mitogenic” MAPK signaling pathwayof ERK 1/2. To inves...

  4. A negative allosteric modulator modulates GABAB-receptor signalling through GB2 subunits.

    PubMed

    Sun, Bing; Chen, Linhai; Liu, Lei; Xia, Zhixiong; Pin, Jean-Philippe; Nan, Fajun; Liu, Jianfeng

    2016-03-15

    An γ-aminobutyric acid type B (GABAB)-receptor mediates slow and prolonged synaptic inhibition in the central nervous system, which represents an interesting target for the treatment of various diseases and disorders of the central nervous system. To date, only one activator of the GABAB-receptor, baclofen, is on the market for the treatment of spasticity. Inhibitors of the GABAB-receptor, such as antagonists, show anti-absence seizure activity and pro-cognitive properties. In a search for allosteric compounds of the GABAB-receptor, although several positive allosteric modulators have been developed, it is only recently that the first negative allosteric modulator (NAM), CLH304a (also named Compound 14), has been reported. In the present study, we provide further information on the mechanism of action of CLH304a, and also show the possibility of designing more NAMs, such as CLH391 and CLH393, based on the structure of CLH304a. First we show that CLH304a inhibits native GABAB-receptor activity in cultured cerebellar granular neurons. We then show that CLH304a has inverse agonist properties and non-competitively inhibits the effect of agonists, indicating that it binds at a different site to GABA. The GABAB-receptor is a mandatory heterodimer made of GB1 subunits, in which agonists bind, and GB2 subunits, which activate G-proteins. By using various combinations made up of wild-type and/or mutated GB1 and GB2 subunits, we show that CLH304a acts on the heptahelical domain of GB2 subunits. These data revealed the possibility of designing innovative NAMs acting in the heptahelical domain of the GB2 subunits, offering novel possibilities for therapeutic intervention based on GABAB-receptor inhibition. PMID:26772870

  5. Mapping Cannabinoid 1 Receptor Allosteric Site(s): Critical Molecular Determinant and Signaling Profile of GAT100, a Novel, Potent, and Irreversibly Binding Probe.

    PubMed

    Laprairie, Robert B; Kulkarni, Abhijit R; Kulkarni, Pushkar M; Hurst, Dow P; Lynch, Diane; Reggio, Patricia H; Janero, David R; Pertwee, Roger G; Stevenson, Lesley A; Kelly, Melanie E M; Denovan-Wright, Eileen M; Thakur, Ganesh A

    2016-06-15

    One of the most abundant G-protein coupled receptors (GPCRs) in brain, the cannabinoid 1 receptor (CB1R), is a tractable therapeutic target for treating diverse psychobehavioral and somatic disorders. Adverse on-target effects associated with small-molecule CB1R orthosteric agonists and inverse agonists/antagonists have plagued their translational potential. Allosteric CB1R modulators offer a potentially safer modality through which CB1R signaling may be directed for therapeutic benefit. Rational design of candidate, druglike CB1R allosteric modulators requires greater understanding of the architecture of the CB1R allosteric endodomain(s) and the capacity of CB1R allosteric ligands to tune the receptor's information output. We have recently reported the synthesis of a focused library of rationally designed, covalent analogues of Org27569 and PSNCBAM-1, two prototypic CB1R negative allosteric modulators (NAMs). Among the novel, pharmacologically active CB1R NAMs reported, the isothiocyanate GAT100 emerged as the lead by virtue of its exceptional potency in the [(35)S]GTPγS and β-arrestin signaling assays and its ability to label CB1R as a covalent allosteric probe with significantly reduced inverse agonism in the [(35)S]GTPγS assay as compared to Org27569. We report here a comprehensive functional profiling of GAT100 across an array of important downstream cell-signaling pathways and analysis of its potential orthosteric probe-dependence and signaling bias. The results demonstrate that GAT100 is a NAM of the orthosteric CB1R agonist CP55,940 and the endocannabinoids 2-arachidonoylglycerol and anandamide for β-arrestin1 recruitment, PLCβ3 and ERK1/2 phosphorylation, cAMP accumulation, and CB1R internalization in HEK293A cells overexpressing CB1R and in Neuro2a and STHdh(Q7/Q7) cells endogenously expressing CB1R. Distinctively, GAT100 was a more potent and efficacious CB1R NAM than Org27569 and PSNCBAM-1 in all signaling assays and did not exhibit the inverse

  6. Substrate-Modulated Thermal Fluctuations Affect Long-Range Allosteric Signaling in Protein Homodimers: Exemplified in CAP

    PubMed Central

    Toncrova, Hedvika; McLeish, Tom C.B.

    2010-01-01

    Abstract The role of conformational dynamics in allosteric signaling of proteins is increasingly recognized as an important and subtle aspect of this ubiquitous phenomenon. Cooperative binding is commonly observed in proteins with twofold symmetry that bind two identical ligands. We construct a coarse-grained model of an allosteric coupled dimer and show how the signal can be propagated between the distant binding sites via change in slow global vibrational modes alone. We demonstrate that modulation on substrate binding of as few as 5–10 slow modes can give rise to cooperativity observed in biological systems and that the type of cooperativity is given by change of interaction between the two monomers upon ligand binding. To illustrate the application of the model, we apply it to a challenging test case: the catabolite activator protein (CAP). CAP displays negative cooperativity upon association with two identical ligands. The conformation of CAP is not affected by the binding, but its vibrational spectrum undergoes a strong modification. Intriguingly, the first binding enhances thermal fluctuations, yet the second quenches them. We show that this counterintuitive behavior is, in fact, necessary for an optimal anticooperative system, and captured within a well-defined region of the model's parameter space. From analyzing the experimental results, we conclude that fast local modes take an active part in the allostery of CAP, coupled to the more-global slow modes. By including them into the model, we elucidate the role of the modes on different timescales. We conclude that such dynamic control of allostery in homodimers may be a general phenomenon and that our model framework can be used for extended interpretation of thermodynamic parameters in other systems. PMID:20483341

  7. Allosterism in human complement component 5a ((h)C5a): a damper of C5a receptor (C5aR) signaling.

    PubMed

    Rana, Soumendra; Sahoo, Amita Rani; Majhi, Bharat Kumar

    2016-06-01

    The phenomena of allosterism continues to advance the field of drug discovery, by illuminating gainful insights for many key processes, related to the structure-function relationships in proteins and enzymes, including the transmembrane G-protein coupled receptors (GPCRs), both in normal as well as in the disease states. However, allosterism is completely unexplored in the native protein ligands, especially when a small covalent change significantly modulates the pharmacology of the protein ligands toward the signaling axes of the GPCRs. One such example is the human C5a ((h)C5a), the potent cationic anaphylatoxin that engages C5aR and C5L2 to elicit numerous immunological and non-immunological responses in humans. From the recently available structure-function data, it is clear that unlike the mouse C5a ((m)C5a), the (h)C5a displays conformational heterogeneity. However, the molecular basis of such conformational heterogeneity, otherwise allosterism in (h)C5a and its precise contribution toward the overall C5aR signaling is not known. This study attempts to decipher the functional role of allosterism in (h)C5a, by exploring the inherent conformational dynamics in (m)C5a, (h)C5a and in its point mutants, including the proteolytic mutant des-Arg(74)-(h)C5a. Prima facie, the comparative molecular dynamics study, over total 500 ns, identifies Arg(74)-Tyr(23) and Arg(37)-Phe(51) "cation-π" pairs as the molecular "allosteric switches" on (h)C5a that potentially functions as a damper of C5aR signaling. PMID:26212097

  8. Prolyl Isomerization as a Molecular Memory in the Allosteric Regulation of the Signal Adapter Protein c-CrkII

    PubMed Central

    Schmidpeter, Philipp A. M.; Schmid, Franz X.

    2015-01-01

    c-CrkII is a central signal adapter protein. A domain opening/closing reaction between its N- and C-terminal Src homology 3 domains (SH3N and SH3C, respectively) controls signal propagation from upstream tyrosine kinases to downstream targets. In chicken but not in human c-CrkII, opening/closing is coupled with cis/trans isomerization at Pro-238 in SH3C. Here, we used advanced double-mixing experiments and kinetic simulations to uncover dynamic domain interactions in c-CrkII and to elucidate how they are linked with cis/trans isomerization and how this regulates substrate binding to SH3N. Pro-238 trans → cis isomerization is not a simple on/off switch but converts chicken c-CrkII from a high affinity to a low affinity form. We present a double-box model that describes c-CrkII as an allosteric system consisting of an open, high affinity R state and a closed, low affinity T state. Coupling of the T-R transition with an intrinsically slow prolyl isomerization provides c-CrkII with a kinetic memory and possibly functions as a molecular attenuator during signal transduction. PMID:25488658

  9. Prolyl isomerization as a molecular memory in the allosteric regulation of the signal adapter protein c-CrkII.

    PubMed

    Schmidpeter, Philipp A M; Schmid, Franz X

    2015-01-30

    c-CrkII is a central signal adapter protein. A domain opening/closing reaction between its N- and C-terminal Src homology 3 domains (SH3N and SH3C, respectively) controls signal propagation from upstream tyrosine kinases to downstream targets. In chicken but not in human c-CrkII, opening/closing is coupled with cis/trans isomerization at Pro-238 in SH3C. Here, we used advanced double-mixing experiments and kinetic simulations to uncover dynamic domain interactions in c-CrkII and to elucidate how they are linked with cis/trans isomerization and how this regulates substrate binding to SH3N. Pro-238 trans → cis isomerization is not a simple on/off switch but converts chicken c-CrkII from a high affinity to a low affinity form. We present a double-box model that describes c-CrkII as an allosteric system consisting of an open, high affinity R state and a closed, low affinity T state. Coupling of the T-R transition with an intrinsically slow prolyl isomerization provides c-CrkII with a kinetic memory and possibly functions as a molecular attenuator during signal transduction. PMID:25488658

  10. NOVEL SIGNAL PROCESSING WITH NONLINEAR TRANSMISSION LINES

    SciTech Connect

    D. REAGOR; ET AL

    2000-08-01

    Nonlinear dielectrics offer uniquely strong and tunable nonlinearities that make them attractive for current devices (for example, frequency-agile microwave filters) and for future signal-processing technologies. The goal of this project is to understand pulse propagation on nonlinear coplanar waveguide prototype devices. We have performed time-domain and frequency-domain experimental studies of simple waveguide structures and pursued a theoretical understanding of the propagation of signals on these nonlinear waveguides. To realistically assess the potential applications, we used a time-domain measurement and analysis technique developed during this project to perform a broadband electrodynamics characterization in terms of nonlinear, dispersive, and dissipative effects. We completed a comprehensive study of coplanar waveguides made from high-temperature superconducting thin-film YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} electrodes on nonlinear dielectric single-crystal SrTiO{sub 3} substrates. By using parameters determined from small-signal (linear) transmission characteristics of the waveguides, we develop a model equation that successfully predicts and describes large-signal (nonlinear) behavior.

  11. Allosteric proteins as logarithmic sensors

    PubMed Central

    Olsman, Noah; Goentoro, Lea

    2016-01-01

    Many sensory systems, from vision and hearing in animals to signal transduction in cells, respond to fold changes in signal relative to background. Responding to fold change requires that the system senses signal on a logarithmic scale, responding identically to a change in signal level from 1 to 3, or from 10 to 30. It is an ongoing search in the field to understand the ways in which a logarithmic sensor can be implemented at the molecular level. In this work, we present evidence that logarithmic sensing can be implemented with a single protein, by means of allosteric regulation. Specifically, we find that mathematical models show that allosteric proteins can respond to stimuli on a logarithmic scale. Next, we present evidence from measurements in the literature that some allosteric proteins do operate in a parameter regime that permits logarithmic sensing. Finally, we present examples suggesting that allosteric proteins are indeed used in this capacity: allosteric proteins play a prominent role in systems where fold-change detection has been proposed. This finding suggests a role as logarithmic sensors for the many allosteric proteins across diverse biological processes. PMID:27410043

  12. Amyloid-β peptides act as allosteric modulators of cholinergic signalling through formation of soluble BAβACs

    PubMed Central

    Kumar, Rajnish; Nordberg, Agneta

    2016-01-01

    amyloid-β interacts readily in an apolipoprotein-facilitated manner with butyrylcholinesterase, forming highly stable and soluble complexes, BAβACs, which can be separated in their native states by sucrose density gradient technique. Enzymological analyses further evinced that amyloid-β concentration dependently increased the acetylcholine-hydrolyzing capacity of cholinesterases. In silico biomolecular analysis further deciphered the allosteric amino acid fingerprint of the amyloid-β-cholinesterase molecular interaction in formation of BAβACs. In the case of butyrylcholinesterase, the results indicated that amyloid-β interacts with a putative activation site at the mouth of its catalytic tunnel, most likely leading to increased acetylcholine influx into the catalytic site, and thereby increasing the intrinsic catalytic rate of butyrylcholinesterase. In conclusion, at least one of the native physiological functions of amyloid-β is allosteric modulation of the intrinsic catalytic efficiency of cholinesterases, and thereby regulation of synaptic and extrasynaptic cholinergic signalling. High apolipoprotein-E may pathologically alter the biodynamics of this amyloid-β function. PMID:26525916

  13. Identification of C-terminal motifs responsible for transmission of inhibition by ATP of mammalian phosphofructokinase, and their contribution to other allosteric effects.

    PubMed Central

    Martínez-Costa, Oscar H; Hermida, Carmen; Sánchez-Martínez, Cristina; Santamaría, Belén; Aragón, Juan J

    2004-01-01

    Systematic deletions and point mutations in the C-terminal extension of mammalian PFK (phosphofructokinase) led us to identify Leu-767 and Glu-768 of the M-type isoform (PFK-M) as the motifs responsible for the role of this region in inhibition by MgATP. These amino acids are the only residues of the C-terminus that are conserved in all mammalian isoforms, and were found to have a similar function in the C-type isoenzyme. Both residues in PFK-C and Leu-767 in PFK-M were also observed to be critical for inhibition by citrate, which is synergistic with that by MgATP. Binding studies utilizing titration of intrinsic protein fluorescence indicated that the C-terminal part of the enzyme participates in the signal transduction route from the MgATP inhibitory site to the catalytic site, but does not contribute to the binding of this inhibitor, whereas it is essential for the binding of citrate. Mutations of the identified structural motifs did not alter either the action of other allosteric effectors that also interact with MgATP, such as the inhibitor phosphoenolpyruvate and the strong activator fructose 2,6-bisphosphate, or the co-operative effect of fructose 6-phosphate. The latter data provide evidence that activation by fructose 2,6-bisphosphate and fructose 6-phosphate co-operativity are not linked to the same allosteric transition as that mediating inhibition by MgATP. PMID:12974670

  14. Dynamics of Mechanical Signal Transmission through Prestressed Stress Fibers

    PubMed Central

    Hwang, Yongyun; Barakat, Abdul I.

    2012-01-01

    Transmission of mechanical stimuli through the actin cytoskeleton has been proposed as a mechanism for rapid long-distance mechanotransduction in cells; however, a quantitative understanding of the dynamics of this transmission and the physical factors governing it remains lacking. Two key features of the actin cytoskeleton are its viscoelastic nature and the presence of prestress due to actomyosin motor activity. We develop a model of mechanical signal transmission through prestressed viscoelastic actin stress fibers that directly connect the cell surface to the nucleus. The analysis considers both temporally stationary and oscillatory mechanical signals and accounts for cytosolic drag on the stress fibers. To elucidate the physical parameters that govern mechanical signal transmission, we initially focus on the highly simplified case of a single stress fiber. The results demonstrate that the dynamics of mechanical signal transmission depend on whether the applied force leads to transverse or axial motion of the stress fiber. For transverse motion, mechanical signal transmission is dominated by prestress while fiber elasticity has a negligible effect. Conversely, signal transmission for axial motion is mediated uniquely by elasticity due to the absence of a prestress restoring force. Mechanical signal transmission is significantly delayed by stress fiber material viscosity, while cytosolic damping becomes important only for longer stress fibers. Only transverse motion yields the rapid and long-distance mechanical signal transmission dynamics observed experimentally. For simple networks of stress fibers, mechanical signals are transmitted rapidly to the nucleus when the fibers are oriented largely orthogonal to the applied force, whereas the presence of fibers parallel to the applied force slows down mechanical signal transmission significantly. The present results suggest that cytoskeletal prestress mediates rapid mechanical signal transmission and allows

  15. Allosteric Modulation of the Calcium-sensing Receptor Rectifies Signaling Abnormalities Associated with G-protein α-11 Mutations Causing Hypercalcemic and Hypocalcemic Disorders*

    PubMed Central

    Babinsky, Valerie N.; Hannan, Fadil M.; Gorvin, Caroline M.; Howles, Sarah A.; Nesbit, M. Andrew; Rust, Nigel; Hanyaloglu, Aylin C.; Hu, Jianxin; Spiegel, Allen M.; Thakker, Rajesh V.

    2016-01-01

    Germline loss- and gain-of-function mutations of G-protein α-11 (Gα11), which couples the calcium-sensing receptor (CaSR) to intracellular calcium (Ca2+i) signaling, lead to familial hypocalciuric hypercalcemia type 2 (FHH2) and autosomal dominant hypocalcemia type 2 (ADH2), respectively, whereas somatic Gα11 mutations mediate uveal melanoma development by constitutively up-regulating MAPK signaling. Cinacalcet and NPS-2143 are allosteric CaSR activators and inactivators, respectively, that ameliorate signaling disturbances associated with CaSR mutations, but their potential to modulate abnormalities of the downstream Gα11 protein is unknown. This study investigated whether cinacalcet and NPS-2143 may rectify Ca2+i alterations associated with FHH2- and ADH2-causing Gα11 mutations, and evaluated the influence of germline gain-of-function Gα11 mutations on MAPK signaling by measuring ERK phosphorylation, and assessed the effect of NPS-2143 on a uveal melanoma Gα11 mutant. WT and mutant Gα11 proteins causing FHH2, ADH2 or uveal melanoma were transfected in CaSR-expressing HEK293 cells, and Ca2+i and ERK phosphorylation responses measured by flow-cytometry and Alphascreen immunoassay following exposure to extracellular Ca2+ (Ca2+o) and allosteric modulators. Cinacalcet and NPS-2143 rectified the Ca2+i responses of FHH2- and ADH2-associated Gα11 loss- and gain-of-function mutations, respectively. ADH2-causing Gα11 mutations were demonstrated not to be constitutively activating and induced ERK phosphorylation following Ca2+o stimulation only. The increased ERK phosphorylation associated with ADH2 and uveal melanoma mutants was rectified by NPS-2143. These findings demonstrate that CaSR-targeted compounds can rectify signaling disturbances caused by germline and somatic Gα11 mutations, which respectively lead to calcium disorders and tumorigenesis; and that ADH2-causing Gα11 mutations induce non-constitutive alterations in MAPK signaling. PMID:26994139

  16. Data Transmission Signal Design and Analysis

    NASA Technical Reports Server (NTRS)

    Moore, J. D.

    1972-01-01

    The error performances of several digital signaling methods are determined as a function of a specified signal-to-noise ratio. Results are obtained for Gaussian noise and impulse noise. Performance of a receiver for differentially encoded biphase signaling is obtained by extending the results of differential phase shift keying. The analysis presented obtains a closed-form answer through the use of some simplifying assumptions. The results give an insight into the analysis problem, however, the actual error performance may show a degradation because of the assumptions made in the analysis. Bipolar signaling decision-threshold selection is investigated. The optimum threshold depends on the signal-to-noise ratio and requires the use of an adaptive receiver.

  17. Allosteric Modulation of Chemoattractant Receptors

    PubMed Central

    Allegretti, Marcello; Cesta, Maria Candida; Locati, Massimo

    2016-01-01

    Chemoattractants control selective leukocyte homing via interactions with a dedicated family of related G protein-coupled receptor (GPCR). Emerging evidence indicates that the signaling activity of these receptors, as for other GPCR, is influenced by allosteric modulators, which interact with the receptor in a binding site distinct from the binding site of the agonist and modulate the receptor signaling activity in response to the orthosteric ligand. Allosteric modulators have a number of potential advantages over orthosteric agonists/antagonists as therapeutic agents and offer unprecedented opportunities to identify extremely selective drug leads. Here, we resume evidence of allosterism in the context of chemoattractant receptors, discussing in particular its functional impact on functional selectivity and probe/concentration dependence of orthosteric ligands activities. PMID:27199992

  18. Efficient signal transmission by synchronization through compound chaotic signal

    NASA Astrophysics Data System (ADS)

    Murali, K.; Lakshmanan, M.

    1997-07-01

    The idea of synchronization of chaotic systems is further extended to the case where all the drive system variables are combined suitably to obtain a compound chaotic signal. An appropriate feedback loop is constructed in the response system to achieve synchronization among the variables of the drive and response systems. We apply this approach to transmit both analog and digital data signals in which the quality of the recovered signal is higher and the encoding is more secure.

  19. Mechanisms of cytoskeleton-mediated mechanical signal transmission in cells

    PubMed Central

    Hwang, Yongyun; Gouget, Cecile L.M.; Barakat, Abdul I.

    2012-01-01

    Recent experiments have demonstrated very rapid long-distance transmission of mechanical forces within cells. Because the speed of this transmission greatly exceeds that of reaction-diffusion signaling, it has been conjectured that it occurs via the propagation of elastic waves through the actin stress fiber network. To explore the plausibility of this conjecture, we recently developed a model of small amplitude stress fiber deformations in prestressed viscoelastic stress fibers subjected to external forces. The model results demonstrated that rapid mechanical signal transmission is only possible when the external force is applied orthogonal to the stress fiber axis and that the dynamics of this transmission are governed by a balance between the prestress in the stress fiber and the stress fiber's material viscosity. The present study, which is a follow-up on our previous model, uses dimensional analysis to: (1) further evaluate the plausibility of the elastic wave conjecture and (2) obtain insight into mechanical signal transmission dynamics in simple stress fiber networks. We show that the elastic wave scenario is likely not the mechanism of rapid mechanical signal transmission in actin stress fibers due to the highly viscoelastic character of these fibers. Our analysis also demonstrates that the time constant characterizing mechanical stimulus transmission is strongly dependent on the topology of the stress fiber network, implying that network organization plays an important role in determining the dynamics of cellular responsiveness to mechanical stimulation. PMID:23336020

  20. Peptide Inhibitors Disrupt the Serotonin 5-HT2C Receptor Interaction with Phosphatase and Tensin Homolog to Allosterically Modulate Cellular Signaling and Behavior

    PubMed Central

    Anastasio, Noelle C.; Gilbertson, Scott R.; Bubar, Marcy J.; Agarkov, Anton; Stutz, Sonja J.; Jeng, Yowjiun; Bremer, Nicole M.; Smith, Thressa D.; Fox, Robert G.; Swinford, Sarah E.; Seitz, Patricia K.; Charendoff, Marc N.; Craft, John W.; Laezza, Fernanda M.; Watson, Cheryl S.; Briggs, James M.; Cunningham, Kathryn A.

    2013-01-01

    Serotonin (5-hydroxytryptamine; 5-HT) signaling through the 5-HT2C receptor (5-HT2CR) is essential in normal physiology, whereas aberrant 5-HT2CR function is thought to contribute to the pathogenesis of multiple neural disorders. The 5-HT2CR interacts with specific protein partners, but the impact of such interactions on 5-HT2CR function is poorly understood. Here, we report convergent cellular and behavioral data that the interaction between the 5-HT2CR and protein phosphatase and tensin homolog (PTEN) serves as a regulatory mechanism to control 5-HT2CR-mediated biology but not that of the closely homologous 5-HT2AR. A peptide derived from the third intracellular loop of the human 5-HT2CR [3L4F (third loop, fourth fragment)] disrupted the association, allosterically augmented 5-HT2CR-mediated signaling in live cells, and acted as a positive allosteric modulator in rats in vivo. We identified the critical residues within an 8 aa fragment of the 3L4F peptide that maintained efficacy (within the picomolar range) in live cells similar to that of the 3L4F peptide. Last, molecular modeling identified key structural features and potential interaction sites of the active 3L4F peptides against PTEN. These compelling data demonstrate the specificity and importance of this protein assembly in cellular events and behaviors mediated by 5-HT2CR signaling and provide a chemical guidepost to the future development of drug-like peptide or small-molecule inhibitors as neuroprobes to study 5-HT2CR allostery and therapeutics for 5-HT2CR-mediated disorders. PMID:23345234

  1. Allosteric function and dysfunction of the prion protein.

    PubMed

    Linden, Rafael; Cordeiro, Yraima; Lima, Luis Mauricio T R

    2012-04-01

    Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases associated with progressive oligo- and multimerization of the prion protein (PrP(C)), its conformational conversion, aggregation and precipitation. We recently proposed that PrP(C) serves as a cell surface scaffold protein for a variety of signaling modules, the effects of which translate into wide-range functional consequences. Here we review evidence for allosteric functions of PrP(C), which constitute a common property of scaffold proteins. The available data suggest that allosteric effects among PrP(C) and its partners are involved in the assembly of multi-component signaling modules at the cell surface, impose upon both physiological and pathological conformational responses of PrP(C), and that allosteric dysfunction of PrP(C) has the potential to entail progressive signal corruption. These properties may be germane both to physiological roles of PrP(C), as well as to the pathogenesis of the TSEs and other degenerative/non-communicable diseases. PMID:21984610

  2. Autocrine signal transmission with extracellular ligand degradation

    NASA Astrophysics Data System (ADS)

    Muratov, C B; Posta, F; Shvartsman, S Y

    2009-03-01

    Traveling waves of cell signaling in epithelial layers orchestrate a number of important processes in developing and adult tissues. These waves can be mediated by positive feedback autocrine loops, a mode of cell signaling where binding of a diffusible extracellular ligand to a cell surface receptor can lead to further ligand release. We formulate and analyze a biophysical model that accounts for ligand-induced ligand release, extracellular ligand diffusion and ligand-receptor interaction. We focus on the case when the main mode for ligand degradation is extracellular and analyze the problem with the sharp threshold positive feedback nonlinearity. We derive expressions that link the speed of propagation and other characteristics of traveling waves to the parameters of the biophysical processes, such as diffusion rates, receptor expression level, etc. Analyzing the derived expressions we found that traveling waves in such systems can exhibit a number of unusual properties, e.g. non-monotonic dependence of the speed of propagation on ligand diffusivity. Our results for the fully developed traveling fronts can be used to analyze wave initiation from localized perturbations, a scenario that frequently arises in the in vitro models of epithelial wound healing, and guide future modeling studies of cell communication in epithelial layers.

  3. High bandwidth magnetically isolated signal transmission circuit

    NASA Technical Reports Server (NTRS)

    Repp, John Donald (Inventor)

    2005-01-01

    Many current electronic systems incorporate expensive or sensitive electrical components. Because electrical energy is often generated or transmitted at high voltages, the power supplies to these electronic systems must be carefully designed. Power supply design must ensure that the electrical system being supplied with power is not exposed to excessive voltages or currents. In order to isolate power supplies from electrical equipment, many methods have been employed. These methods typically involve control systems or signal transfer methods. However, these methods are not always suitable because of their drawbacks. The present invention relates to transmitting information across an interface. More specifically, the present invention provides an apparatus for transmitting both AC and DC information across a high bandwidth magnetic interface with low distortion.

  4. Oscillation-induced signal transmission and gating in neural circuits.

    PubMed

    Jahnke, Sven; Memmesheimer, Raoul-Martin; Timme, Marc

    2014-12-01

    Reliable signal transmission constitutes a key requirement for neural circuit function. The propagation of synchronous pulse packets through recurrent circuits is hypothesized to be one robust form of signal transmission and has been extensively studied in computational and theoretical works. Yet, although external or internally generated oscillations are ubiquitous across neural systems, their influence on such signal propagation is unclear. Here we systematically investigate the impact of oscillations on propagating synchrony. We find that for standard, additive couplings and a net excitatory effect of oscillations, robust propagation of synchrony is enabled in less prominent feed-forward structures than in systems without oscillations. In the presence of non-additive coupling (as mediated by fast dendritic spikes), even balanced oscillatory inputs may enable robust propagation. Here, emerging resonances create complex locking patterns between oscillations and spike synchrony. Interestingly, these resonances make the circuits capable of selecting specific pathways for signal transmission. Oscillations may thus promote reliable transmission and, in co-action with dendritic nonlinearities, provide a mechanism for information processing by selectively gating and routing of signals. Our results are of particular interest for the interpretation of sharp wave/ripple complexes in the hippocampus, where previously learned spike patterns are replayed in conjunction with global high-frequency oscillations. We suggest that the oscillations may serve to stabilize the replay. PMID:25503492

  5. Oscillation-Induced Signal Transmission and Gating in Neural Circuits

    PubMed Central

    Jahnke, Sven; Memmesheimer, Raoul-Martin; Timme, Marc

    2014-01-01

    Reliable signal transmission constitutes a key requirement for neural circuit function. The propagation of synchronous pulse packets through recurrent circuits is hypothesized to be one robust form of signal transmission and has been extensively studied in computational and theoretical works. Yet, although external or internally generated oscillations are ubiquitous across neural systems, their influence on such signal propagation is unclear. Here we systematically investigate the impact of oscillations on propagating synchrony. We find that for standard, additive couplings and a net excitatory effect of oscillations, robust propagation of synchrony is enabled in less prominent feed-forward structures than in systems without oscillations. In the presence of non-additive coupling (as mediated by fast dendritic spikes), even balanced oscillatory inputs may enable robust propagation. Here, emerging resonances create complex locking patterns between oscillations and spike synchrony. Interestingly, these resonances make the circuits capable of selecting specific pathways for signal transmission. Oscillations may thus promote reliable transmission and, in co-action with dendritic nonlinearities, provide a mechanism for information processing by selectively gating and routing of signals. Our results are of particular interest for the interpretation of sharp wave/ripple complexes in the hippocampus, where previously learned spike patterns are replayed in conjunction with global high-frequency oscillations. We suggest that the oscillations may serve to stabilize the replay. PMID:25503492

  6. Transmission of RF Signals Over Optical Fiber for Avionics Applications

    NASA Technical Reports Server (NTRS)

    Slaveski, Filip; Sluss, James, Jr.; Atiquzzaman, Mohammed; Hung, Nguyen; Ngo, Duc

    2002-01-01

    During flight, aircraft avionics transmit and receive RF signals to/from antennas over coaxial cables. As the density and complexity of onboard avionics increases, the electromagnetic interference (EM) environment degrades proportionately, leading to decreasing signal-to-noise ratios (SNRs) and potential safety concerns. The coaxial cables are inherently lossy, limiting the RF signal bandwidth while adding considerable weight. To overcome these limitations, we have investigated a fiber optic communications link for aircraft that utilizes wavelength division multiplexing (WDM) to support the simultaneous transmission of multiple signals (including RF) over a single optical fiber. Optical fiber has many advantages over coaxial cable, particularly lower loss, greater bandwidth, and immunity to EM. In this paper, we demonstrate that WDM can be successfully used to transmit multiple RF signals over a single optical fiber with no appreciable signal degradation. We investigate the transmission of FM and AM analog modulated signals, as well as FSK digital modulated signals, over a fiber optic link (FOL) employing WDM. We present measurements of power loss, delay, SNR, carrier-to-noise ratio (CNR), total harmonic distortion (THD), and bit error rate (BER). Our experimental results indicate that WDM is a fiber optic technology suitable for avionics applications.

  7. MRI dynamic range and its compatibility with signal transmission media

    NASA Astrophysics Data System (ADS)

    Gabr, Refaat E.; Schär, Michael; Edelstein, Arthur D.; Kraitchman, Dara L.; Bottomley, Paul A.; Edelstein, William A.

    2009-06-01

    As the number of MRI phased array coil elements grows, interactions among cables connecting them to the system receiver become increasingly problematic. Fiber optic or wireless links would reduce electromagnetic interference, but their dynamic range (DR) is generally less than that of coaxial cables. Raw MRI signals, however, have a large DR because of the high signal amplitude near the center of k-space. Here, we study DR in MRI in order to determine the compatibility of MRI multicoil imaging with non-coaxial cable signal transmission. Since raw signal data are routinely discarded, we have developed an improved method for estimating the DR of MRI signals from conventional magnitude images. Our results indicate that the DR of typical surface coil signals at 3 T for human subjects is less than 88 dB, even for three-dimensional acquisition protocols. Cardiac and spine coil arrays had a maximum DR of less than 75 dB and head coil arrays less than 88 dB. The DR derived from magnitude images is in good agreement with that measured from raw data. The results suggest that current analog fiber optic links, with a spurious-free DR of 60-70 dB at 500 kHz bandwidth, are not by themselves adequate for transmitting MRI data from volume or array coils with DR ˜90 dB. However, combining analog links with signal compression might make non-coaxial cable signal transmission viable.

  8. Allosteric Modulation of Muscarinic Acetylcholine Receptors

    PubMed Central

    Gregory, Karen J; Sexton, Patrick M; Christopoulos, Arthur

    2007-01-01

    Muscarinic acetylcholine receptors (mAChRs) are prototypical Family A G protein coupled-receptors. The five mAChR subtypes are widespread throughout the periphery and the central nervous system and, accordingly, are widely involved in a variety of both physiological and pathophysiological processes. There currently remains an unmet need for better therapeutic agents that can selectively target a given mAChR subtype to the relative exclusion of others. The main reason for the lack of such selective mAChR ligands is the high sequence homology within the acetylcholine-binding site (orthosteric site) across all mAChRs. However, the mAChRs possess at least one, and likely two, extracellular allosteric binding sites that can recognize small molecule allosteric modulators to regulate the binding and function of orthosteric ligands. Extensive studies of prototypical mAChR modulators, such as gallamine and alcuronium, have provided strong pharmacological evidence, and associated structure-activity relationships (SAR), for a “common” allosteric site on all five mAChRs. These studies are also supported by mutagenesis experiments implicating the second extracellular loop and the interface between the third extracellular loop and the top of transmembrane domain 7 as contributing to the common allosteric site. Other studies are also delineating the pharmacology of a second allosteric site, recognized by compounds such as staurosporine. In addition, allosteric agonists, such as McN-A-343, AC-42 and N-desmethylclozapine, have also been identified. Current challenges to the field include the ability to effectively detect and validate allosteric mechanisms, and to quantify allosteric effects on binding affinity and signaling efficacy to inform allosteric modulator SAR. PMID:19305798

  9. Compression and Transmission of RF Signals for Telediagnosis

    NASA Astrophysics Data System (ADS)

    Seko, Toshihiro; Doi, Motonori; Oshiro, Osamu; Chihara, Kunihiro

    2000-05-01

    Health care is a critical issue nowadays. Much emphasis is given to quality care for all people. Telediagnosis has attracted public attention. We propose a new method of ultrasound image transmission for telediagnosis. In conventional methods, video image signals are transmitted. In our method, the RF signals which are acquired by an ultrasound probe, are transmitted. The RF signals can be transformed to color Doppler images or high-resolution images by a receiver. Because a stored form is adopted, the proposed system can be realized with existent technology such as hyper text transfer protocol (HTTP) and file transfer protocol (FTP). In this paper, we describe two lossless compression methods which specialize in the transmission of RF signals. One of the methods uses the characteristics of the RF signal. In the other method, the amount of the data is reduced. Measurements were performed in water targeting an iron block and triangular Styrofoam. Additionally, abdominal fat measurement was performed. Our method achieved a compression rate of 13% with 8 bit data.

  10. Structure and Dynamics of the Integrin LFA-1 I-Domain in the Inactive State Underlie its Inside-Out/Outside-In Signaling and Allosteric Mechanisms

    PubMed Central

    Kukic, Predrag; Alvin Leung, Hoi Tik; Bemporad, Francesco; Aprile, Francesco A.; Kumita, Janet R.; De Simone, Alfonso; Camilloni, Carlo; Vendruscolo, Michele

    2015-01-01

    Summary Lymphocyte function-associated antigen 1 (LFA-1) is an integrin that transmits information in two directions across the plasma membrane of leukocytes, in so-called outside-in and inside-out signaling mechanisms. To investigate the structural basis of these mechanisms, we studied the conformational space of the apo I-domain using replica-averaged metadynamics simulations in combination with nuclear magnetic resonance chemical shifts. We thus obtained a free energy landscape that reveals the existence of three conformational substates of this domain. The three substates include conformations similar to existing crystallographic structures of the low-affinity I-domain, the inactive I-domain with an allosteric antagonist inhibitor bound underneath α helix 7, and an intermediate affinity state of the I-domain. The multiple substates were validated with residual dipolar coupling measurements. These results suggest that the presence of three substates in the apo I-domain enables the precise regulation of the binding process that is essential for the physiological function of LFA-1. PMID:25773142

  11. A 16-channel flex circuit for cryogenic microwave signal transmission

    NASA Astrophysics Data System (ADS)

    McGarey, Patrick; Mani, Hamdi; Wheeler, Caleb; Groppi, Christopher

    2014-07-01

    Heterodyne focal plane arrays used in the terahertz (THz) regime currently require a discrete set of rigid coaxial cables for the transmission of individual intermediate frequency (IF) signals. Consequently, the size of an array is limited to ~10s of pixels due to limited physical space and the complexity of assembly. In order to achieve an array with ~1000 pixels or greater, new interconnections must be developed capable of carrying multiple IF signals on a single carrier which is flexible, robust to noise, and terminated with a high density RF connector. As an intermediate step to the development of a ~1000 pixel heterodyne focal plane array, the Kilopixel Array Pathfinder Project (KAPPa) has developed a 16 channel IF flex circuit. Initially, design simulations were performed to evaluate various means of high-frequency (1~10 GHz) signal transmission, including microstrip, stripline and coplanar waveguides. The method allowing for the closest signal spacing and greatest resistance to radio frequency interference (RFI) was determined to be stripline. Designs were considered where stripline transitioned to microstrip in order to terminate the signal. As microstrip transmission lines are sensitive to RFI, a design featuring just stripline was evaluated. In both the stripline-to-microstrip and stripline-only designs, a three-layer copper-coated polyimide substrate was used. Signal transitions were accomplished by a signal carrying "hot" via passing through a series of three conductive pads, similar to work by Leib et al. (2010). The transition design essentially mimics a coaxial line, where the radial distance between the pads and the ground plane is optimized in order to achieve desired impedances. In simulation, 50 Ohm impedances were achieved throughout, with crosstalk and return loss limited to -30dB. Terminations are made via an array of Corning Gilbert G3PO blind mate connectors, which are small enough to match the 6mm pixel pitch of the KAPPa focal plane unit

  12. Differential Modulation of Functional Dynamics and Allosteric Interactions in the Hsp90-Cochaperone Complexes with p23 and Aha1: A Computational Study

    PubMed Central

    Blacklock, Kristin; Verkhivker, Gennady M.

    2013-01-01

    Allosteric interactions of the molecular chaperone Hsp90 with a large cohort of cochaperones and client proteins allow for molecular communication and event coupling in signal transduction networks. The integration of cochaperones into the Hsp90 system is driven by the regulatory mechanisms that modulate the progression of the ATPase cycle and control the recruitment of the Hsp90 clientele. In this work, we report the results of computational modeling of allosteric regulation in the Hsp90 complexes with the cochaperones p23 and Aha1. By integrating protein docking, biophysical simulations, modeling of allosteric communications, protein structure network analysis and the energy landscape theory we have investigated dynamics and stability of the Hsp90-p23 and Hsp90-Aha1 interactions in direct comparison with the extensive body of structural and functional experiments. The results have revealed that functional dynamics and allosteric interactions of Hsp90 can be selectively modulated by these cochaperones via specific targeting of the regulatory hinge regions that could restrict collective motions and stabilize specific chaperone conformations. The protein structure network parameters have quantified the effects of cochaperones on conformational stability of the Hsp90 complexes and identified dynamically stable communities of residues that can contribute to the strengthening of allosteric interactions. According to our results, p23-mediated changes in the Hsp90 interactions may provide “molecular brakes” that could slow down an efficient transmission of the inter-domain allosteric signals, consistent with the functional role of p23 in partially inhibiting the ATPase cycle. Unlike p23, Aha1-mediated acceleration of the Hsp90-ATPase cycle may be achieved via modulation of the equilibrium motions that facilitate allosteric changes favoring a closed dimerized form of Hsp90. The results of our study have shown that Aha1 and p23 can modulate the Hsp90-ATPase activity

  13. Blind Channel Shortening for Block Transmission of Correlated Signals

    NASA Astrophysics Data System (ADS)

    Miyajima, Teruyuki; Watanabe, Yoshihisa

    In block transmission systems, blind channel shortening methods are known to be effective to reduce the influence of interblock interference which degrades the performance when the length of a channel impulse response is extremely long. Conventional methods assume that the transmitted signal is uncorrelated; however, this assumption is invalid in practical systems such as OFDM with null carriers and MC-CDMA. In this paper, we consider blind channel shortening methods for block transmissions when the transmitted samples within a block are correlated. First, the channel shortening ability of a conventional method is clarified. Next, a new method which exploits the fact that the transmitted samples in different blocks are uncorrelated is introduced. It is shown that the proposed method can shorten the channel properly under certain conditions. Finally, simulation results of OFDM and MC-CDMA systems are shown to verify the effectiveness of the proposed method compared with a conventional one.

  14. Transmission of multiplexed video signals in multimode optical fiber systems

    NASA Technical Reports Server (NTRS)

    White, Preston, III

    1988-01-01

    Kennedy Space Center has the need for economical transmission of two multiplexed video signals along multimode fiberoptic systems. These systems must span unusual distances and must meet RS-250B short-haul standards after reception. Bandwidth is a major problem and studies of the installed fibers, available LEDs and PINFETs led to the choice of 100 MHz as the upper limit for the system bandwidth. Optical multiplexing and digital transmission were deemed inappropriate. Three electrical multiplexing schemes were chosen for further study. Each of the multiplexing schemes included an FM stage to help meet the stringent S/N specification. Both FM and AM frequency division multiplexing methods were investigated theoretically and these results were validated with laboratory tests. The novel application of quadrature amplitude multiplexing was also considered. Frequency division multiplexing of two wideband FM video signal appears the most promising scheme although this application requires high power highly linear LED transmitters. Futher studies are necessary to determine if LEDs of appropriate quality exist and to better quantify performance of QAM in this application.

  15. Mechanistic insight into the conserved allosteric regulation of periplasmic proteolysis by the signaling molecule cyclic-di-GMP

    PubMed Central

    Chatterjee, Debashree; Cooley, Richard B; Boyd, Chelsea D; Mehl, Ryan A; O'Toole, George A; Sondermann, Holger

    2014-01-01

    Stable surface adhesion of cells is one of the early pivotal steps in bacterial biofilm formation, a prevalent adaptation strategy in response to changing environments. In Pseudomonas fluorescens, this process is regulated by the Lap system and the second messenger cyclic-di-GMP. High cytoplasmic levels of cyclic-di-GMP activate the transmembrane receptor LapD that in turn recruits the periplasmic protease LapG, preventing it from cleaving a cell surface-bound adhesin, thereby promoting cell adhesion. In this study, we elucidate the molecular basis of LapG regulation by LapD and reveal a remarkably sensitive switching mechanism that is controlled by LapD's HAMP domain. LapD appears to act as a coincidence detector, whereby a weak interaction of LapG with LapD transmits a transient outside-in signal that is reinforced only when cyclic-di-GMP levels increase. Given the conservation of key elements of this receptor system in many bacterial species, the results are broadly relevant for cyclic-di-GMP- and HAMP domain-regulated transmembrane signaling. DOI: http://dx.doi.org/10.7554/eLife.03650.001 PMID:25182848

  16. Mechanistic insight into the conserved allosteric regulation of periplasmic proteolysis by the signaling molecule cyclic-di-GMP.

    PubMed

    Chatterjee, Debashree; Cooley, Richard B; Boyd, Chelsea D; Mehl, Ryan A; O'Toole, George A; Sondermann, Holger

    2014-01-01

    Stable surface adhesion of cells is one of the early pivotal steps in bacterial biofilm formation, a prevalent adaptation strategy in response to changing environments. In Pseudomonas fluorescens, this process is regulated by the Lap system and the second messenger cyclic-di-GMP. High cytoplasmic levels of cyclic-di-GMP activate the transmembrane receptor LapD that in turn recruits the periplasmic protease LapG, preventing it from cleaving a cell surface-bound adhesin, thereby promoting cell adhesion. In this study, we elucidate the molecular basis of LapG regulation by LapD and reveal a remarkably sensitive switching mechanism that is controlled by LapD's HAMP domain. LapD appears to act as a coincidence detector, whereby a weak interaction of LapG with LapD transmits a transient outside-in signal that is reinforced only when cyclic-di-GMP levels increase. Given the conservation of key elements of this receptor system in many bacterial species, the results are broadly relevant for cyclic-di-GMP- and HAMP domain-regulated transmembrane signaling. PMID:25182848

  17. Power and signal transmission for mobile teleoperated systems

    SciTech Connect

    Morris, A.C. Jr.; Hamel, W.R.

    1985-01-01

    Appropriate means must be furnished for supplying power and for sending controlling commands to mobile teleoperated systems. Because a sizable number of possibilities are available for such applications, methods used in designing both the power and communications systems built into mobile vehicles that serve in radiological emergencies must be carefully selected. This paper describes a number of umbilical, on-board, and wireless systems used in tranmitting power that are available for mobile teleoperator services. The pros and cons of selecting appropriate methods from a list of possible communication systems (wired, fiber optic, and radio frequency) are also examined. Moreover, hybrid systems combining wireless power transmissions with command-information signals are also possible.

  18. Cerasomes: Soft Interface for Redox Enzyme Electrochemical Signal Transmission.

    PubMed

    Qiao, Yun; Tahara, Keishiro; Zhang, Qian; Song, Xi-Ming; Kikuchi, Jun-ichi

    2016-01-22

    Anionic cerasomes, which consist of a liposomal lipid bilayer and a ceramic surface, were used as a soft interface for the construction of an integrated modified electrode to achieve the transmission of chemical information from a redox enzyme through electrical signals. The morphological properties of the cerasomes were systematically compared with those of two structural analogues, namely, liposomes and silica nanoparticles. The results indicated that the cerasomes combined the advantages of liposomes and silica nanoparticles. The lipid bilayer gave excellent biocompatibility, as in the case of liposomes, and high structural stability, similar to that of silica nanoparticles, was derived from the silicate framework on the cerasome surface. The performance at the electrochemical interface created by means of a combination of cerasomes and horseradish peroxidase on a glassy carbon electrode was much better than those achieved with liposomes or silica nanoparticles instead of cerasomes. The potential use of cerasomes in the construction of supramolecular devices for mediator-free biosensing was evaluated. PMID:26671064

  19. The structural basis of ATP as an allosteric modulator.

    PubMed

    Lu, Shaoyong; Huang, Wenkang; Wang, Qi; Shen, Qiancheng; Li, Shuai; Nussinov, Ruth; Zhang, Jian

    2014-09-01

    Adenosine-5'-triphosphate (ATP) is generally regarded as a substrate for energy currency and protein modification. Recent findings uncovered the allosteric function of ATP in cellular signal transduction but little is understood about this critical behavior of ATP. Through extensive analysis of ATP in solution and proteins, we found that the free ATP can exist in the compact and extended conformations in solution, and the two different conformational characteristics may be responsible for ATP to exert distinct biological functions: ATP molecules adopt both compact and extended conformations in the allosteric binding sites but conserve extended conformations in the substrate binding sites. Nudged elastic band simulations unveiled the distinct dynamic processes of ATP binding to the corresponding allosteric and substrate binding sites of uridine monophosphate kinase, and suggested that in solution ATP preferentially binds to the substrate binding sites of proteins. When the ATP molecules occupy the allosteric binding sites, the allosteric trigger from ATP to fuel allosteric communication between allosteric and functional sites is stemmed mainly from the triphosphate part of ATP, with a small number from the adenine part of ATP. Taken together, our results provide overall understanding of ATP allosteric functions responsible for regulation in biological systems. PMID:25211773

  20. The Structural Basis of ATP as an Allosteric Modulator

    PubMed Central

    Wang, Qi; Shen, Qiancheng; Li, Shuai; Nussinov, Ruth; Zhang, Jian

    2014-01-01

    Adenosine-5’-triphosphate (ATP) is generally regarded as a substrate for energy currency and protein modification. Recent findings uncovered the allosteric function of ATP in cellular signal transduction but little is understood about this critical behavior of ATP. Through extensive analysis of ATP in solution and proteins, we found that the free ATP can exist in the compact and extended conformations in solution, and the two different conformational characteristics may be responsible for ATP to exert distinct biological functions: ATP molecules adopt both compact and extended conformations in the allosteric binding sites but conserve extended conformations in the substrate binding sites. Nudged elastic band simulations unveiled the distinct dynamic processes of ATP binding to the corresponding allosteric and substrate binding sites of uridine monophosphate kinase, and suggested that in solution ATP preferentially binds to the substrate binding sites of proteins. When the ATP molecules occupy the allosteric binding sites, the allosteric trigger from ATP to fuel allosteric communication between allosteric and functional sites is stemmed mainly from the triphosphate part of ATP, with a small number from the adenine part of ATP. Taken together, our results provide overall understanding of ATP allosteric functions responsible for regulation in biological systems. PMID:25211773

  1. Bombyx mori prothoracicostatic peptide receptor is allosterically activated via a Gα(i/o)-protein-biased signalling cascade by Drosophila sex peptide.

    PubMed

    He, Xiaobai; Zang, Jiashu; Yang, Huipeng; Huang, Haishan; Shi, Ying; Zhu, Chenggang; Zhou, Naiming

    2015-03-01

    In insects, molting and metamorphosis are strictly regulated by ecdysteroids. Ecdysteroid synthesis is positively or negatively controlled by several neuropeptides. The prothoracicostatic peptide (PTSP) BmPTSP (Bombyx mori prothoracicostatic peptide), isolated from the larval brain of B. mori, has been demonstrated to inhibit ecdysteroid synthesis in the prothoracic glands (PGs) [Hua et al. (1999) J. Biol. Chem. 274, 31169-31173]. More recently, the newly recognized B. mori receptor for Drosophila melanogaster sex peptide (DmSP) has been identified as a receptor for BmPTSP. However, details on the signalling pathways and physiological functions of this receptor have remained elusive. In the present paper, we report the functional characterization of the BmPTSP receptor (BmPTSPR)/sex peptide (SP) receptor (SPR) using both mammalian and insect cells. Synthetic DmSP shows the potential to inhibit forskolin (FSK) or adipokinetic hormone (AKH)-induced cAMP-response element (CRE)-driven luciferase (Luc) activity in a manner comparable with synthetic BmPTSP1. However, DmSP displayed a much lower activity in triggering Ca²⁺ mobilization and internalization than did BmPTSP1. Additionally, 6-carboxy-fluorescein fluorophore (FAM)-labelled DmSP and BmPTSP3 were found to bind specifically to BmPTSPR/SPR. The binding of FAM-DmSP was displaced by unlabelled DmSP, but not by unlabelled BmPTSP1 and, vice versa, the binding of FAM-BmPTSP3 was blocked by unlabelled BmPTSP3, but not by unlabelled DmSP. Moreover, internalization assays demonstrated that BmPTSP1, but not DmSP, evoked recruitment of the Bombyx non-visual arrestin, Kurtz, to the activated BmPTSPR/SPR in the plasma membrane. This was followed by induction of internalization. This suggests that BmPTSP1 is probably an endogenous ligand specific for BmPTSPR/SPR. We therefore designate this receptor BmPTSPR. In contrast, DmSP is an allosteric agonist that is biased towards Gα(i/o)-dependent cAMP production and away from Ca

  2. Signal transmission within the P2X2 trimeric receptor.

    PubMed

    Keceli, Batu; Kubo, Yoshihiro

    2014-06-01

    P2X2 receptor channel, a homotrimer activated by the binding of extracellular adenosine triphosphate (ATP) to three intersubunit ATP-binding sites (each located ∼50 Å from the ion permeation pore), also shows voltage-dependent activation upon hyperpolarization. Here, we used tandem trimeric constructs (TTCs) harboring critical mutations at the ATP-binding, linker, and pore regions to investigate how the ATP activation signal is transmitted within the trimer and how signals generated by ATP and hyperpolarization converge. Analysis of voltage- and [ATP]-dependent gating in these TTCs showed that: (a) Voltage- and [ATP]-dependent gating of P2X2 requires binding of at least two ATP molecules. (b) D315A mutation in the β-14 strand of the linker region connecting the ATP-binding domains to the pore-forming helices induces two different gating modes; this requires the presence of the D315A mutation in at least two subunits. (c) The T339S mutation in the pore domains of all three subunits abolishes the voltage dependence of P2X2 gating in saturating [ATP], making P2X2 equally active at all membrane potentials. Increasing the number of T339S mutations in the TTC results in gradual changes in the voltage dependence of gating from that of the wild-type channel, suggesting equal and independent contributions of the subunits at the pore level. (d) Voltage- and [ATP]-dependent gating in TTCs differs depending on the location of one D315A relative to one K308A that blocks the ATP binding and downstream signal transmission. (e) Voltage- and [ATP]-dependent gating does not depend on where one T339S is located relative to K308A (or D315A). Our results suggest that each intersubunit ATP-binding signal is directly transmitted on the same subunit to the level of D315 via the domain that contributes K308 to the β-14 strand. The signal subsequently spreads equally to all three subunits at the level of the pore, resulting in symmetric and independent contributions of the three

  3. Signal transmission within the P2X2 trimeric receptor

    PubMed Central

    Kubo, Yoshihiro

    2014-01-01

    P2X2 receptor channel, a homotrimer activated by the binding of extracellular adenosine triphosphate (ATP) to three intersubunit ATP-binding sites (each located ∼50 Å from the ion permeation pore), also shows voltage-dependent activation upon hyperpolarization. Here, we used tandem trimeric constructs (TTCs) harboring critical mutations at the ATP-binding, linker, and pore regions to investigate how the ATP activation signal is transmitted within the trimer and how signals generated by ATP and hyperpolarization converge. Analysis of voltage- and [ATP]-dependent gating in these TTCs showed that: (a) Voltage- and [ATP]-dependent gating of P2X2 requires binding of at least two ATP molecules. (b) D315A mutation in the β-14 strand of the linker region connecting the ATP-binding domains to the pore-forming helices induces two different gating modes; this requires the presence of the D315A mutation in at least two subunits. (c) The T339S mutation in the pore domains of all three subunits abolishes the voltage dependence of P2X2 gating in saturating [ATP], making P2X2 equally active at all membrane potentials. Increasing the number of T339S mutations in the TTC results in gradual changes in the voltage dependence of gating from that of the wild-type channel, suggesting equal and independent contributions of the subunits at the pore level. (d) Voltage- and [ATP]-dependent gating in TTCs differs depending on the location of one D315A relative to one K308A that blocks the ATP binding and downstream signal transmission. (e) Voltage- and [ATP]-dependent gating does not depend on where one T339S is located relative to K308A (or D315A). Our results suggest that each intersubunit ATP-binding signal is directly transmitted on the same subunit to the level of D315 via the domain that contributes K308 to the β-14 strand. The signal subsequently spreads equally to all three subunits at the level of the pore, resulting in symmetric and independent contributions of the three

  4. Baseband signal transmission experiment for intra-brain communication with implantable image sensor.

    PubMed

    Sasagawa, Kiyotaka; Yokota, Shogo; Matsuda, Takashi; Davis, Peter; Zhang, Bing; Li, Keren; Kobayashi, Takuma; Noda, Toshihiko; Tokuda, Takashi; Ohta, Jun

    2012-01-01

    We demonstrate image signal transmission for wireless intra-brain communication. As a preliminary experiment, transmission characteristics of the brain phantom were measured. The baseband output signal from an implantable complementary metal-oxide-semiconductor (CMOS) image sensor is transmitted through the phantom. The image was successfully reproduced from the received signal. PMID:23367299

  5. Model for a neural network structure and signal transmission

    NASA Astrophysics Data System (ADS)

    Kotsavasiloglou, C.; Kalampokis, A.; Argyrakis, P.; Baloyannis, S.

    1997-10-01

    We present a model of a neural network that is based on the diffusion-limited-aggregation (DLA) structure from fractal physics. A single neuron is one DLA cluster, while a large number of clusters, in an interconnected fashion, make up the neural network. Using simulation techniques, a signal is randomly generated and traced through its transmission inside the neuron and from neuron to neuron through the synapses. The activity of the entire neural network is monitored as a function of time. The characteristics included in the model contain, among others, the threshold for firing, the excitatory or inhibitory character of the synapse, the synaptic delay, and the refractory period. The system activity results in ``noisy'' time series that exhibit an oscillatory character. Standard power spectra are evaluated and fractal analyses performed, showing that the system is not chaotic, but the varying parameters can be associated with specific values of fractal dimensions. It is found that the network activity is not linear with the system parameters, e.g., with the numbers of active synapses. The details of this behavior may have interesting repercussions from the neurological point of view.

  6. INSTRUMENTATION FOR SURVEYING ACOUSTIC SIGNALS IN NATURAL GAS TRANSMISSION LINES

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-09-01

    In the U.S. natural gas is distributed through more than one million miles of high-pressure transmission pipelines. If all leaks and infringements could be detected quickly, it would enhance safety and U.S. energy security. Only low frequency acoustic waves appear to be detectable over distances up to 60 km where pipeline shut-off valves provide access to the inside of the pipeline. This paper describes a Portable Acoustic Monitoring Package (PAMP) developed to record and identify acoustic signals characteristic of: leaks, pump noise, valve and flow metering noise, third party infringement, manual pipeline water and gas blow-off, etc. This PAMP consists of a stainless steel 1/2 inch NPT plumbing tree rated for use on 1000 psi pipelines. Its instrumentation is designed to measure acoustic waves over the entire frequency range from zero to 16,000 Hz by means of four instruments: (1) microphone, (2) 3-inch water full range differential pressure transducer with 0.1% of range sensitivity, (3) a novel 3 inch to 100 inch water range amplifier, using an accumulator with needle valve and (4) a line-pressure transducer. The weight of the PAMP complete with all accessories is 36 pounds. This includes a remote control battery/switch box assembly on a 25-foot extension chord, a laptop data acquisition computer on a field table and a sun shield.

  7. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, Jeffrey D.

    1997-01-01

    A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion.

  8. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, J.D.

    1997-05-06

    A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion. 3 figs.

  9. Allosteric modulation of caspases.

    PubMed

    Häcker, Hans-Georg; Sisay, Mihiret Tekeste; Gütschow, Michael

    2011-11-01

    Caspases are proteolytic enzymes mainly involved in the induction and execution phases of apoptosis. This type of programmed cell death is an essential regulatory process required to maintain the integrity and homeostasis of multicellular organisms. Inappropriate apoptosis is attributed a key role in many human diseases, including neurodegenerative disorders, ischemic damage, autoimmune diseases and cancer. Allosteric modulation of the function of a protein occurs when the regulatory trigger, such as the binding of a small effector or inhibitor molecule, takes place some distance from the protein's active site. In recent years, several caspases have been identified that possess allosteric sites and binding of small molecule to these sites resulted in the modulation of enzyme activities. Regulation of caspase activity by small molecule allosteric modulators is believed to be of great therapeutic importance. In this review we give brief highlights on recent developments in identifying and characterizing natural and synthetic allosteric inhibitors as well as activators of caspases and discuss their potential in drug discovery and protein engineering. PMID:21807025

  10. Optical signal monitoring in phase modulated optical fiber transmission systems

    NASA Astrophysics Data System (ADS)

    Zhao, Jian

    Optical performance monitoring (OPM) is one of the essential functions for future high speed optical networks. Among the parameters to be monitored, chromatic dispersion (CD) is especially important since it has a significant impact on overall system performance. In this thesis effective CD monitoring approaches for phase-shift keying (PSK) based optical transmission systems are investigated. A number of monitoring schemes based on radio frequency (RF) spectrum analysis and delay-tap sampling are proposed and their performance evaluated. A method for dispersion monitoring of differential phase-shift keying (DPSK) signals based on RF power detection is studied. The RF power spectrum is found to increase with the increase of CD and decrease with polarization mode dispersion (PMD). The spectral power density dependence on CD is studied theoretically and then verified through simulations and experiments. The monitoring sensitivity for nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) and return-to-zero differential phase-shift keying (RZ-DPSK) based systems can reach 80ps/nm/dB and 34ps/nm/dB respectively. The scheme enables the monitoring of differential group delay (DGD) and CD simultaneously. The monitoring sensitivity of CD and DGD can reach 56.7ps/nm/dB and 3.1ps/dB using a bandpass filter. The effects of optical signal-to-noise ratio (OSNR), DGD, fiber nonlinearity and chirp on the monitoring results are investigated. Two RF pilot tones are employed for CD monitoring of DPSK signals. Specially selected pilot tone frequencies enable good monitoring sensitivity with minimum influence on the received signals. The dynamic range exceeding 35dB and monitoring sensitivity up to 9.5ps/nm/dB are achieved. Asynchronous sampling technique is employed for CD monitoring. A signed CD monitoring method for 10Gb/s NRZ-DPSK and RZ-DPSK systems using asynchronous delay-tap sampling technique is studied. The demodulated signals suffer asymmetric waveform distortion if

  11. Development of a high throughput screen for allosteric modulators of melanocortin-4 receptor signaling using a real time cAMP assay.

    PubMed

    Pantel, Jacques; Williams, Savannah Y; Mi, Dehui; Sebag, Julien; Corbin, Jackie D; Weaver, C David; Cone, Roger D

    2011-06-11

    The melanocortin MC(4) receptor is a potential target for the development of drugs for both obesity and cachexia. Melanocortin MC(4) receptor ligands known thus far are orthosteric agonists or antagonists, however the agonists, in particular, have generally exhibited unwanted side effects. For some receptors, allosteric modulators are expected to reduce side-effect profiles. To identify allosteric modulators of the melanocortin MC(4) receptor, we created HEK293 cell lines coexpressing the human melanocortin MC(4) receptor and a modified luciferase-based cAMP sensor. Monitoring luminescence as a readout of real-time intracellular cAMP concentration, we demonstrate that this cell line is able to report melanocortin agonist responses, as well as inverse agonist response to the physiological AgRP peptide. Based on the MC4R-GLO cell line, we developed an assay that was shown to meet HTS standards (Z'=0.50). A pilot screen run on the Microsource Spectrum compound library (n=2000) successfully identified 62 positive modulators. This screen identified predicted families of compounds: β(2)AR agonists - the β(2)AR being endogenously expressed in HEK293 cells, an adenylyl cyclase activator and finally a distribution of phosphodiesterase (PDE) inhibitors well characterized or recently identified. In this last category, we identified a structural family of coumarin-derived compounds (imperatorin, osthol and prenyletin), along with deracoxib, a drug in veterinary use for its COX2 inhibitory properties. This latter finding unveiled a new off-target mechanism of action for deracoxib as a PDE inhibitor. Overall, these data are the first report of a HTS for allosteric modulators for a Gs protein coupled receptor. PMID:21296065

  12. Development of a high throughput screen for allosteric modulators of melanocortin-4 receptor signaling using a real time cAMP assay

    PubMed Central

    Pantel, Jacques; Williams, Savannah Y.; Mi, Dehui; Sebag, Julien; Corbin, Jackie D.; Weaver, C. David; Cone, Roger D.

    2011-01-01

    The melanocortin MC4 receptor is a potential target for the development of drugs for both obesity and cachexia. Melanocortin MC4 receptor ligands known thus far are orthosteric agonists or antagonists, however the agonists, in particular, have generally exhibited unwanted side effects. For some receptors, allosteric modulators are expected to reduce side-effect profiles. To identify allosteric modulators of the melanocortin MC4 receptor, we created HEK293 cell lines coexpressing the human melanocortin MC4 receptor and a modified luciferase-based cAMP sensor. Monitoring luminescence as a readout of real-time intracellular cAMP concentration, we demonstrate this cell line is able to report melanocortin agonist responses, as well as inverse agonist response to the physiological AgRP peptide. Based on the MC4R-GLO cell line, we developed an assay that was shown to meet HTS standards (Z’=0.50). A pilot screen run on the Microsource Spectrum compound library (n= 2,000) successfully identified 62 positive modulators. This screen identified predicted families of compounds: β2AR agonists –the β2AR being endogenously expressed in HEK293 cells-, an adenylyl cyclase activator and finally a distribution of phosphodiesterase (PDE) inhibitors well characterized or recently identified. In this last category, we identified a structural family of coumarin-derived compounds (imperatorin, osthol and prenyletin), along with deracoxib, a drug in veterinary use for its COX2 inhibitory properties. This latter finding unveiled a new off-target mechanism of action for deracoxib as a PDE inhibitor. Overall, these data are the first report of an HTS for allosteric modulators for a Gs protein coupled receptor. PMID:21296065

  13. 47 CFR 11.51 - EAS code and Attention Signal Transmission requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false EAS code and Attention Signal Transmission requirements. 11.51 Section 11.51 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EMERGENCY ALERT SYSTEM (EAS) Emergency Operations § 11.51 EAS code and Attention Signal Transmission requirements. (a) Analog and digital broadcast...

  14. 47 CFR 11.51 - EAS code and Attention Signal Transmission requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false EAS code and Attention Signal Transmission requirements. 11.51 Section 11.51 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EMERGENCY ALERT SYSTEM (EAS) Emergency Operations § 11.51 EAS code and Attention Signal Transmission requirements. (a) Analog and digital broadcast...

  15. 47 CFR 11.51 - EAS code and Attention Signal Transmission requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false EAS code and Attention Signal Transmission requirements. 11.51 Section 11.51 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EMERGENCY ALERT SYSTEM (EAS) Emergency Operations § 11.51 EAS code and Attention Signal Transmission requirements. (a) Analog and digital broadcast...

  16. Mapping of the Allosteric Site in Cholesterol Hydroxylase CYP46A1 for Efavirenz, a Drug That Stimulates Enzyme Activity.

    PubMed

    Anderson, Kyle W; Mast, Natalia; Hudgens, Jeffrey W; Lin, Joseph B; Turko, Illarion V; Pikuleva, Irina A

    2016-05-27

    Cytochrome P450 46A1 (CYP46A1) is a microsomal enzyme and cholesterol 24-hydroxylase that controls cholesterol elimination from the brain. This P450 is also a potential target for Alzheimer disease because it can be activated pharmacologically by some marketed drugs, as exemplified by efavirenz, the anti-HIV medication. Previously, we suggested that pharmaceuticals activate CYP46A1 allosterically through binding to a site on the cytosolic protein surface, which is different from the enzyme active site facing the membrane. Here we identified this allosteric site for efavirenz on CYP46A1 by using a combination of hydrogen-deuterium exchange coupled to MS, computational modeling, site-directed mutagenesis, and analysis of the CYP46A1 crystal structure. We also mapped the binding region for the CYP46A1 redox partner oxidoreductase and found that the allosteric and redox partner binding sites share a common border. On the basis of the data obtained, we propose the mechanism of CYP46A1 allostery and the pathway for the signal transmission from the P450 allosteric site to the active site. PMID:27056331

  17. Hidden data transmission using time delay for separating useful signals from masking oscillations

    NASA Astrophysics Data System (ADS)

    Kal'Yanov, Er. V.

    2009-03-01

    A new method of hidden data transmission based on the use of time delay for the separation of useful signals from masking noise-like (chaotic or stochastic) oscillations is described. Mathematical models involving a source of chaotic oscillations have been studied using numerical methods. The transmission of a masked non-encoded signal and the pulsed data transmission using 0/1 bit code are considered.

  18. Controlling allosteric networks in proteins

    NASA Astrophysics Data System (ADS)

    Dokholyan, Nikolay

    2013-03-01

    We present a novel methodology based on graph theory and discrete molecular dynamics simulations for delineating allosteric pathways in proteins. We use this methodology to uncover the structural mechanisms responsible for coupling of distal sites on proteins and utilize it for allosteric modulation of proteins. We will present examples where inference of allosteric networks and its rewiring allows us to ``rescue'' cystic fibrosis transmembrane conductance regulator (CFTR), a protein associated with fatal genetic disease cystic fibrosis. We also use our methodology to control protein function allosterically. We design a novel protein domain that can be inserted into identified allosteric site of target protein. Using a drug that binds to our domain, we alter the function of the target protein. We successfully tested this methodology in vitro, in living cells and in zebrafish. We further demonstrate transferability of our allosteric modulation methodology to other systems and extend it to become ligh-activatable.

  19. Signal transmission in a Y-shaped one-way chain

    NASA Astrophysics Data System (ADS)

    Liang, Xiaoming; Tang, Ming; Lü, Huaping

    2013-12-01

    It has been found that noise plays a key role to improve signal transmission in a one-way chain of bistable systems [Zhang et al., Phys. Rev. E 58, 2952 (1998)]. We here show that the signal transmission can be sharply improved without the aid of noise, if the one-way chain with a single source node is changed with two source nodes becoming a Y-shaped one-way chain. We further reveal that the enhanced signal transmission in the Y-shaped one-way chain is regulated by coupling strength, and that it is robust to noise perturbation and input signal irregularity. We finally analyze the mechanism of the enhanced signal transmission by the Y-shaped structure.

  20. A study on Data Transmission Scheme for High Functional Railway Signaling System

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryo; Sano, Minoru; Mochizuki, Hiroshi; Nakamura, Hideo

    Railway signaling systems that transmit control information via rails have been deployed in many applications, for example, digital automatic train control (ATC) systems for controlling train speed. Since the performance of digital ATC systems depends on the signal transmission speed, recently there have been many studies aimed at realizing high-speed data transmission. However, it is difficult to increase the transmission speed because rails have strong attenuation in proportion to an increase of the frequency. In this paper, we aimed to increase the transmission speed by improving the modulation scheme to overcome these limitations. We proposed CDMA-QAM method that is combined code-division multiple access (CDMA) and quadrature amplitude modulation (QAM). And we evaluated in a field trial the CDMA-QAM rail transmission device developed using DSP. On the other hand, an analog ATC based on an amplitude modulation (AM) is still employed in some railway lines. It is difficult for their lines to introduce the digital signal due to track circuit configurations and interoperability conditions. So we studied a data transmission scheme that makes it possible to mix an analog signal and a digital signal, and evaluated the influence given to both signals using a developed device that generates the mixed signal of analog and digital signal.

  1. Batteryless wireless transmission system for electronic drum uses piezoelectric generator for play signal and power source

    NASA Astrophysics Data System (ADS)

    Nishikawa, H.; Yoshimi, A.; Takemura, K.; Tanaka, A.; Douseki, T.

    2015-12-01

    A batteryless self-powered wireless transmission system has been developed that sends a signal from a drum pad to a synthesizer. The power generated by a piezoelectric generator functions both as the “Play” signal for the synthesizer and as the power source for the transmitter. An FM transmitter, which theoretically operates with zero latency, and a receiver with quick-response squelch of the received signal were developed for wireless transmission with a minimum system delay. Experimental results for an electronic drum without any connecting wires fully demonstrated the feasibility of self-powered wireless transmission with a latency of 900 μs.

  2. Method and apparatus for low-loss signal transmission

    NASA Technical Reports Server (NTRS)

    Siegel, Peter (Inventor); Yeh, Cavour (Inventor); Shimabukuro, Fred (Inventor); Fraser, Scott (Inventor)

    2008-01-01

    The present invention relates to the field of radio-frequency (RF) waveguides. More specifically, the present invention pertains to a method and apparatus that provides ultra-low-loss RF waveguide structures targeted between approximately 300 GHz and approximately 30 THz. The RF waveguide includes a hollow core and a flexible honeycomb, periodic-bandgap structure surrounding the hollow core. The flexible honeycomb, periodic-bandgap structure is formed of a plurality of tubes formed of a dielectric material such as of low-loss quartz, polyethylene, or high-resistivity silicon. Using the RF waveguide, a user may attach a terahertz signal source to the waveguide and pass signals through the waveguide, while a terahertz signal receiver receives the signals.

  3. Coherent Terahertz Wireless Signal Transmission Using Advanced Optical Fiber Communication Technology

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Kuri, Toshiaki; Morohashi, Isao; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Kitayama, Ken-ichi

    2015-02-01

    Coherent terahertz signal transmission with multilevel modulation and demodulation is demonstrated using an optical sub-harmonic IQ mixer (SHIQM), which consists of optical components in advanced optical fiber communication technologies. An optical-frequency-comb-employed signal generator is capable of vector modulation as well as frequency tunability. Digital signal processing (DSP) adopted from the recently developed optical digital coherent communication can easily demodulate multi-level modulated terahertz signals by using electrical heterodyning for intermediate-frequency (IF) down conversion. This technique is applicable for mobile backhauling in the next-generation mobile communication technology directly connected to an optical fiber network as a high-speed wireless transmission link.

  4. Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

    2009-01-01

    Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

  5. Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

    2008-01-01

    Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

  6. Allosteric Mechanisms in Chaperonin Machines.

    PubMed

    Gruber, Ranit; Horovitz, Amnon

    2016-06-01

    Chaperonins are nanomachines that facilitate protein folding by undergoing energy (ATP)-dependent movements that are coordinated in time and space owing to complex allosteric regulation. They consist of two back-to-back stacked oligomeric rings with a cavity at each end where protein substrate folding can take place. Here, we focus on the GroEL/GroES chaperonin system from Escherichia coli and, to a lesser extent, on the more poorly characterized eukaryotic chaperonin CCT/TRiC. We describe their various functional (allosteric) states and how they are affected by substrates and allosteric effectors that include ATP, ADP, nonfolded protein substrates, potassium ions, and GroES (in the case of GroEL). We also discuss the pathways of intra- and inter-ring allosteric communication by which they interconvert and the coupling between allosteric transitions and protein folding reactions. PMID:26726755

  7. Simulation of the coherent MDM transmission using principal modes of the optical fiber as signal carriers

    NASA Astrophysics Data System (ADS)

    Lyubopytov, Vladimir S.; Zakirov, Robert A.; Vinogradova, Irina L.; Sultanov, Albert K.

    2015-03-01

    In this paper we demonstrate computer simulation results obtained for the coherent mode division multiplexed (MDM) 5x5 QPSK transmission using principal modes (PMs) of the stepped-index few-mode fiber (FMF) as a basis of independent signal carriers. The output signal recovering and the fiber propagation matrix determination are considered to be carried out in optical domain by means of reconfigurable multibranch diffractive optical elements (DOEs). Both the cases of Gaussian and Nyquist raised-cosine pulse shaping are considered for optical signal modulation. The simulation results show, that the transmission in the basis of PMs in strong coupling regime allows the reliability of the coherent MDM system to be fundamentally improved. As a result, utilization of the optical signal processing for MDM transmission could minimize substantially the DSP circuit complexity required for the real-time recovering of the transmitted signal.

  8. Vector 8QAM signal generation and transmission based on optical carrier suppression

    NASA Astrophysics Data System (ADS)

    Xiao, Jiangnan; Zhang, Zirang; Li, Xingying; Xu, Yuming; Chen, Long; Yu, Jianjun

    2015-11-01

    We experimentally demonstrate how to generate photonic eight quadrature amplitude modulation (M-QAM) vector signal by using only one Mach-Zehnder modulator (MZM). Because of the 'square-law' characteristic of the photodetector (PD), the amplitudes and the phase of the driving radio-frequency (RF) signal are changed after detection. The pre-coding for the amplitudes and the phase of the driving radio-frequency (RF) signal before they drive the MZM will take the advantages of restoring the driving precoding signal to regular signal after PD. The transmission performance with different date rates at 1, 2, and 3-Gbaud over single-mode fiber (SMF) transmission is experimentally demonstrated. The bit-error ratios (BERs) of the transmission system are less than the forward-error-correction (FEC) threshold of 3.8×10-3.

  9. Dendritic signal transmission induced by intracellular charge inhomogeneities

    NASA Astrophysics Data System (ADS)

    Lazarevich, Ivan A.; Kazantsev, Victor B.

    2013-12-01

    Signal propagation in neuronal dendrites represents the basis for interneuron communication and information processing in the brain. Here we take into account charge inhomogeneities arising in the vicinity of ion channels in cytoplasm and obtain a modified cable equation. We show that charge inhomogeneities acting on a millisecond time scale can lead to the appearance of propagating waves with wavelengths of hundreds of micrometers. They correspond to a certain frequency band predicting the appearance of resonant properties in brain neuron signaling. We also show that membrane potential in spiny dendrites obeys the modified cable equation suggesting a crucial role of the spines in dendritic subthreshold resonance.

  10. Paired SSB optical OFDM channels for high spectral efficient signal transmission over DWDM networks

    NASA Astrophysics Data System (ADS)

    Chicharro, Francisco I.; Ortega, Beatriz; Mora, José

    2016-07-01

    A new high spectral efficient SSB-OOFDM DWDM transmission system has been experimentally demonstrated. The proposed transmitter employs paired optical channels consisting of two SSB modulated OFDM signals using opposite sidebands in order to allow an efficient use of the spectrum with optical carriers separation under 10 GHz. Moreover, different paired channels are multiplexed into the 25 GHz grid DWDM fiber transmission link. Optical carrier spacing of 8.75 GHz in paired channels has been demonstrated allowing 40.8 Gb/s signal transmission rate over a 25 GHz paired channel bandwidth.

  11. Allosterism at muscarinic receptors: ligands and mechanisms.

    PubMed

    Birdsall, N J M; Lazareno, S

    2005-06-01

    The evaluation of allosteric ligands at muscarinic receptors is discussed in terms of the ability of the experimental data to be interpreted by the allosteric ternary complex model. The compilation of useful SAR information of allosteric ligands is not simple, especially for muscarinic receptors, where there are multiple allosteric sites and complex interactions. PMID:15974931

  12. Efficient Sparse Signal Transmission over a Lossy Link Using Compressive Sensing

    PubMed Central

    Wu, Liantao; Yu, Kai; Cao, Dongyu; Hu, Yuhen; Wang, Zhi

    2015-01-01

    Reliable data transmission over lossy communication link is expensive due to overheads for error protection. For signals that have inherent sparse structures, compressive sensing (CS) is applied to facilitate efficient sparse signal transmissions over lossy communication links without data compression or error protection. The natural packet loss in the lossy link is modeled as a random sampling process of the transmitted data, and the original signal will be reconstructed from the lossy transmission results using the CS-based reconstruction method at the receiving end. The impacts of packet lengths on transmission efficiency under different channel conditions have been discussed, and interleaving is incorporated to mitigate the impact of burst data loss. Extensive simulations and experiments have been conducted and compared to the traditional automatic repeat request (ARQ) interpolation technique, and very favorable results have been observed in terms of both accuracy of the reconstructed signals and the transmission energy consumption. Furthermore, the packet length effect provides useful insights for using compressed sensing for efficient sparse signal transmission via lossy links. PMID:26287195

  13. Electronic post-compensation of WDM transmission impairments using coherent detection and digital signal processing.

    PubMed

    Li, Xiaoxu; Chen, Xin; Goldfarb, Gilad; Mateo, Eduardo; Kim, Inwoong; Yaman, Fatih; Li, Guifang

    2008-01-21

    A universal post-compensation scheme for fiber impairments in wavelength-division multiplexing (WDM) systems is proposed based on coherent detection and digital signal processing (DSP). Transmission of 10 x 10 Gbit/s binary-phase-shift-keying (BPSK) signals at a channel spacing of 20 GHz over 800 km dispersion shifted fiber (DSF) has been demonstrated numerically. PMID:18542162

  14. Secure chaotic transmission of electrocardiography signals with acousto-optic modulation under profiled beam propagation.

    PubMed

    Almehmadi, Fares S; Chatterjee, Monish R

    2015-01-10

    Electrocardiography (ECG) signals are used for both medical purposes and identifying individuals. It is often necessary to encrypt this highly sensitive information before it is transmitted over any channel. A closed-loop acousto-optic hybrid device acting as a chaotic modulator is applied to ECG signals to achieve this encryption. Recently improved modeling of this approach using profiled optical beams has shown it to be very sensitive to key parameters that characterize the encryption and decryption process, exhibiting its potential for secure transmission of analog and digital signals. Here the encryption and decryption is demonstrated for ECG signals, both analog and digital versions, illustrating strong encryption without significant distortion. Performance analysis pertinent to both analog and digital transmission of the ECG waveform is also carried out using output signal-to-noise, signal-to-distortion, and bit-error-rate measures relative to the key parameters and presence of channel noise in the system. PMID:25967617

  15. Transmission characteristics of a TEM waveguide for transient signals by the use of a damped sinusoidal

    NASA Astrophysics Data System (ADS)

    Briest, N.; Garbe, H.; Potthast, S.

    2015-11-01

    This article broaches the issue of the propagation of transient signals in gigahertz transverse electromagnetic (GTEM) cells. As a representative for transient signals a damped sinusoidal (DS) is used with three different mid-band frequencies. The signal transmission of the DS in the GTEM1250 is qualified and discussed on the basis of the Pearson correlation coefficient (Pcc). The Pcc gives an overview of the signal transmission quality for all measuring points within the testvolume and signal distortions can be identified. A 100 MHz DS is weakly distorted in several measuring points. The Pcc at those points decreases and a signal shape variance can be assumed. Furthermore inhomogeneities of the GTEM1250 caused by the cell door can be identified.

  16. Architecture and implementation for high-bandwidth real-time radar signal transmission and computing application

    NASA Astrophysics Data System (ADS)

    Cho, Yoong-Goog; Chandrasekar, V.; Jayasumana, Anura P.; Brunkow, David

    2002-06-01

    he design, architecture, and implementation for the high-throughput data transmission and high-performance computing,which are applicable for various real-time radar signal transmission applications over the data network, are presented. With a client-server model, the multiple processes and threads on the end systems operate simultaneously and collaborately to meet the real-time requirement. The design covers the Digitized Radar Signal (DRS) data acquisition and data transmission on the DRS server end as well as DRS data receiving, radar signal parameter computation and parameter transmission on the DRS receiver end. Generic packet and data structures for transmission and inter-process data sharing are constructed. The architecture was successfully implemented on Sun/Solaris workstations with dual 750 MHz UltraSPARC-III processors containing Gigabit Ethernet card. The comparison in transmission throughput over gigabit link between with computation and without computation clearly shows the importance of the signal processing capability on the end-to-end performance. Profiling analysis on the DRS receiver process shows the work-loaded functions and provides guides for improving computing capabilities.

  17. Activation and Allosteric Modulation of Human μ Opioid Receptor in Molecular Dynamics.

    PubMed

    Bartuzi, Damian; Kaczor, Agnieszka A; Matosiuk, Dariusz

    2015-11-23

    Allosteric protein modulation has gained increasing attention in drug design. Its application as a mechanism of action could bring forth safer and more effective medicines. Targeting opioid receptors with allosteric modulators can result in better treatment of pain, depression, and respiratory and immune disorders. In this work we use recent reports on negative modulators of μ opioid receptor as a starting point for identification of allosteric sites and mechanisms of opioid receptor modulation using homology modeling and docking and molecular dynamics studies. An allosteric binding site description is presented. Results suggest a shared binding region for lipophilic allosteric ligands, reveal possible differences in the modulation mechanism between cannabinoids and salvinorin A, and show ambiguous properties of the latter. Also, they emphasize the importance of native-like environment in molecular dynamics simulations and uncover relationships between modulator and orthosteric ligand binding and receptor behavior. Relationships between ligands, transmission switch, and hydrophobic lock are analyzed. PMID:26517559

  18. Multi-line transmission in medical imaging using the second-harmonic signal.

    PubMed

    Prieur, Fabrice; Dénarié, Bastien; Austeng, Andreas; Torp, Hans

    2013-12-01

    The emergence of three-dimensional imaging in the field of medical ultrasound imaging has greatly increased the number of transmissions needed to insonify a whole volume. With a large number of transmissions comes a low image frame rate. When using classical transmission techniques, as in two-dimensional imaging, the frame rate becomes unacceptably low, prompting the use of alternative transmission patterns that require less time. One alternative is to use a multi-line transmission (MLT) technique which consists of transmitting several pulses simultaneously in different directions. Perturbations appear when acquiring and beamforming the signal in the direction of one pulse because of the pulses sent in other directions. The edge waves from the pulses transmitted in a different direction add to the signal transmitted in the direction of interest, resulting in artifacts in the final image. Taking advantage of the nonlinear propagation of sound in tissue, the second-harmonic signal can be used with the MLT technique. The image obtained using the second-harmonic signal, compared with an image obtained using the fundamental signal, should have reduced artifacts coming from other pulses transmitted simultaneously. Simulations, backed up by experiments imaging a wire target and an in vivo left ventricle, confirm that the hypothesis is valid. In the studied case, the perturbations appear as an increase in the signal level around the main echo of a point scatterer. When using the fundamental signal, the measured amplitude level of the perturbations was approximately -40 dB compared with the maximum signal amplitude (-27 dB in vivo), whereas it was around -60 dB (-45 dB in vivo) for the second-harmonic signal. The MLT technique encounters limitations in the very near field where the pulses overlap and the perturbation level also increases for images with strong speckle and low contrast. PMID:24297034

  19. 37 CFR 258.3 - Royalty fee for secondary transmission of analog signals of broadcast stations by satellite...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... transmission of analog signals of broadcast stations by satellite carriers. 258.3 Section 258.3 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.3 Royalty fee for secondary transmission of analog signals of broadcast stations by satellite carriers....

  20. 37 CFR 258.3 - Royalty fee for secondary transmission of analog signals of broadcast stations by satellite...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... transmission of analog signals of broadcast stations by satellite carriers. 258.3 Section 258.3 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.3 Royalty fee for secondary transmission of analog signals of broadcast stations by satellite carriers....

  1. 37 CFR 258.4 - Royalty fee for secondary transmission of digital signals of broadcast stations by satellite...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... transmission of digital signals of broadcast stations by satellite carriers. 258.4 Section 258.4 Patents... RULES AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.4 Royalty fee for secondary transmission of digital signals of broadcast stations by satellite carriers....

  2. 37 CFR 258.4 - Royalty fee for secondary transmission of digital signals of broadcast stations by satellite...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... transmission of digital signals of broadcast stations by satellite carriers. 258.4 Section 258.4 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.4 Royalty fee for secondary transmission of digital signals of broadcast stations by satellite carriers....

  3. 37 CFR 258.4 - Royalty fee for secondary transmission of digital signals of broadcast stations by satellite...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... transmission of digital signals of broadcast stations by satellite carriers. 258.4 Section 258.4 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.4 Royalty fee for secondary transmission of digital signals of broadcast stations by satellite carriers....

  4. 37 CFR 258.3 - Royalty fee for secondary transmission of analog signals of broadcast stations by satellite...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... transmission of analog signals of broadcast stations by satellite carriers. 258.3 Section 258.3 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.3 Royalty fee for secondary transmission of analog signals of broadcast stations by satellite carriers....

  5. 37 CFR 258.3 - Royalty fee for secondary transmission of analog signals of broadcast stations by satellite...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... transmission of analog signals of broadcast stations by satellite carriers. 258.3 Section 258.3 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.3 Royalty fee for secondary transmission of analog signals of broadcast stations by satellite carriers....

  6. 37 CFR 258.4 - Royalty fee for secondary transmission of digital signals of broadcast stations by satellite...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... transmission of digital signals of broadcast stations by satellite carriers. 258.4 Section 258.4 Patents... AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.4 Royalty fee for secondary transmission of digital signals of broadcast stations by satellite carriers....

  7. 37 CFR 258.3 - Royalty fee for secondary transmission of analog signals of broadcast stations by satellite...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... transmission of analog signals of broadcast stations by satellite carriers. 258.3 Section 258.3 Patents... RULES AND PROCEDURES ADJUSTMENT OF ROYALTY FEE FOR SECONDARY TRANSMISSIONS BY SATELLITE CARRIERS § 258.3 Royalty fee for secondary transmission of analog signals of broadcast stations by satellite carriers....

  8. Immune response and insulin signalling alter mosquito feeding behaviour to enhance malaria transmission potential.

    PubMed

    Cator, Lauren J; Pietri, Jose E; Murdock, Courtney C; Ohm, Johanna R; Lewis, Edwin E; Read, Andrew F; Luckhart, Shirley; Thomas, Matthew B

    2015-01-01

    Malaria parasites alter mosquito feeding behaviour in a way that enhances parasite transmission. This is widely considered a prime example of manipulation of host behaviour to increase onward transmission, but transient immune challenge in the absence of parasites can induce the same behavioural phenotype. Here, we show that alterations in feeding behaviour depend on the timing and dose of immune challenge relative to blood ingestion and that these changes are functionally linked to changes in insulin signalling in the mosquito gut. These results suggest that altered phenotypes derive from insulin signalling-dependent host resource allocation among immunity, blood feeding, and reproduction in a manner that is not specific to malaria parasite infection. We measured large increases in mosquito survival and subsequent transmission potential when feeding patterns are altered. Leveraging these changes in physiology, behaviour and life history could promote effective and sustainable control of female mosquitoes responsible for transmission. PMID:26153094

  9. An allosteric role for receptor activity-modifying proteins in defining GPCR pharmacology

    PubMed Central

    J Gingell, Joseph; Simms, John; Barwell, James; Poyner, David R; Watkins, Harriet A; Pioszak, Augen A; Sexton, Patrick M; Hay, Debbie L

    2016-01-01

    G protein-coupled receptors are allosteric proteins that control transmission of external signals to regulate cellular response. Although agonist binding promotes canonical G protein signalling transmitted through conformational changes, G protein-coupled receptors also interact with other proteins. These include other G protein-coupled receptors, other receptors and channels, regulatory proteins and receptor-modifying proteins, notably receptor activity-modifying proteins (RAMPs). RAMPs have at least 11 G protein-coupled receptor partners, including many class B G protein-coupled receptors. Prototypic is the calcitonin receptor, with altered ligand specificity when co-expressed with RAMPs. To gain molecular insight into the consequences of this protein–protein interaction, we combined molecular modelling with mutagenesis of the calcitonin receptor extracellular domain, assessed in ligand binding and functional assays. Although some calcitonin receptor residues are universally important for peptide interactions (calcitonin, amylin and calcitonin gene-related peptide) in calcitonin receptor alone or with receptor activity-modifying protein, others have RAMP-dependent effects, whereby mutations decreased amylin/calcitonin gene-related peptide potency substantially only when RAMP was present. Remarkably, the key residues were completely conserved between calcitonin receptor and AMY receptors, and between subtypes of AMY receptor that have different ligand preferences. Mutations at the interface between calcitonin receptor and RAMP affected ligand pharmacology in a RAMP-dependent manner, suggesting that RAMP may allosterically influence the calcitonin receptor conformation. Supporting this, molecular dynamics simulations suggested that the calcitonin receptor extracellular N-terminal domain is more flexible in the presence of receptor activity-modifying protein 1. Thus, RAMPs may act in an allosteric manner to generate a spectrum of unique calcitonin receptor

  10. Demonstration of optical steganography transmission using temporal phase coded optical signals with spectral notch filtering.

    PubMed

    Hong, Xuezhi; Wang, Dawei; Xu, Lei; He, Sailing

    2010-06-01

    A novel approach is proposed and experimentally demonstrated for optical steganography transmission in WDM networks using temporal phase coded optical signals with spectral notch filtering. A temporal phase coded stealth channel is temporally and spectrally overlaid onto a public WDM channel. Direct detection of the public channel is achieved in the presence of the stealth channel. The interference from the public channel is suppressed by spectral notching before the detection of the optical stealth signal. The approach is shown to have good compatibility and robustness to the existing WDM network for optical steganography transmission. PMID:20588368

  11. Signal processing algorithm for transmission-type Fabry-Pérot interferometric optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Lee, Jung-Ju; Kwon, Dong-Soo

    2001-08-01

    The recently developed transmission-type extrinsic Fabry-Pérot interferometric (TEFPI) optical fiber sensor can simply and effectively compensate for the difficult distinction of the measured direction of conventional EFPI optical fiber sensors. The TEFPI optical fiber sensor signal is composed of fringes and signal level variations, which correspond to the measured quantity and measured directions, respectively. In this paper, the signal processing algorithm, the fringe tracking method, is presented for TEFPI optical fiber sensors with a signal that differs from conventional interferometric sensors. The algorithm is verified by application to simulated and experimental sensor signals from strain measurements. The algorithm successfully processed TEFPI optical fiber sensor signals by finding the correct positions of peaks, valleys and signal levels, and by calculating the exact measured quantity and directions.

  12. Pathways of allosteric regulation in Hsp70 chaperones.

    PubMed

    Kityk, Roman; Vogel, Markus; Schlecht, Rainer; Bukau, Bernd; Mayer, Matthias P

    2015-01-01

    Central to the protein folding activity of Hsp70 chaperones is their ability to interact with protein substrates in an ATP-controlled manner, which relies on allosteric regulation between their nucleotide-binding (NBD) and substrate-binding domains (SBD). Here we dissect this mechanism by analysing mutant variants of the Escherichia coli Hsp70 DnaK blocked at distinct steps of allosteric communication. We show that the SBD inhibits ATPase activity by interacting with the NBD through a highly conserved hydrogen bond network, and define the signal transduction pathway that allows bound substrates to trigger ATP hydrolysis. We identify variants deficient in only one direction of allosteric control and demonstrate that ATP-induced substrate release is more important for chaperone activity than substrate-stimulated ATP hydrolysis. These findings provide evidence of an unexpected dichotomic allostery mechanism in Hsp70 chaperones and provide the basis for a comprehensive mechanical model of allostery in Hsp70s. PMID:26383706

  13. Effect of second order signal-noise interactions in nonlinearity compensated optical transmission systems.

    PubMed

    Al-Khateeb, Mohammad A Z; McCarthy, Mary; Sánchez, Christian; Ellis, Andrew

    2016-04-15

    In this Letter, we theoretically and numerically analyze the performance of coherent optical transmission systems that deploy inline or transceiver based nonlinearity compensation techniques. For systems where signal-signal nonlinear interactions are fully compensated, we find that beyond the performance peak the signal-to-noise ratio degradation has a slope of 3  dBSNR/dBPower suggesting a quartic rather than quadratic dependence on signal power. This is directly related to the fact that signals in a given span will interact not only with linear amplified spontaneous emission noise, but also with the nonlinear four-wave mixing products generated from signal-noise interaction in previous (hitherto) uncompensated spans. The performance of optical systems employing different nonlinearity compensation schemes were numerically simulated and compared against analytical predictions, showing a good agreement within a 0.4 dB margin of error. PMID:27082361

  14. The Second Extracellular Loop of the Adenosine A1 Receptor Mediates Activity of Allosteric Enhancers

    PubMed Central

    Kennedy, Dylan P.; McRobb, Fiona M.; Leonhardt, Susan A.; Purdy, Michael; Figler, Heidi; Marshall, Melissa A.; Chordia, Mahendra; Figler, Robert; Linden, Joel

    2014-01-01

    Allosteric enhancers of the adenosine A1 receptor amplify signaling by orthosteric agonists. Allosteric enhancers are appealing drug candidates because their activity requires that the orthosteric site be occupied by an agonist, thereby conferring specificity to stressed or injured tissues that produce adenosine. To explore the mechanism of allosteric enhancer activity, we examined their action on several A1 receptor constructs, including (1) species variants, (2) species chimeras, (3) alanine scanning mutants, and (4) site-specific mutants. These findings were combined with homology modeling of the A1 receptor and in silico screening of an allosteric enhancer library. The binding modes of known docked allosteric enhancers correlated with the known structure-activity relationship, suggesting that these allosteric enhancers bind to a pocket formed by the second extracellular loop, flanked by residues S150 and M162. We propose a model in which this vestibule controls the entry and efflux of agonists from the orthosteric site and agonist binding elicits a conformational change that enables allosteric enhancer binding. This model provides a mechanism for the observations that allosteric enhancers slow the dissociation of orthosteric agonists but not antagonists. PMID:24217444

  15. Transmission line galloping image monitoring system based on digital signal processor

    NASA Astrophysics Data System (ADS)

    Ren, Hai Peng; Ma, Zhan Feng

    2011-06-01

    An embedded image monitoring system based on TMS320DM642 Digital Signal Processor (DSP) is proposed for the transmission line monitoring. The system can detect galloping, ice or snow covering, and other abnormal status of the transmission line in a real time mode. The image detection algorithms are compared using the controlled experiment under the complex weather environment, thereby, a set of image processing algorithms is proposed for transmission lines image monitoring. The DSP/BOIS multi-threaded programming techniques are used to realize the algorithm in the DSPs' embedded software. A wireless communication based on General Packet Radio Service (GPRS) module is designed to transmit the detection results and the changed information of the image to the monitoring center, so that the operators can get the real time status of the transmission line. The application of the system will play an important role in the condition-based maintenance of power transmission lines and improve the reliability of power delivery system. Transmission line; Status monitoring; Complex weather factor; Image filtering and sharpening; Image segment; Morphological filtering; Wireless communication; Digital signal processor; Multi-threaded programming.

  16. 47 CFR 90.317 - Fixed ancillary signaling and data transmissions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Fixed ancillary signaling and data transmissions. 90.317 Section 90.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz...

  17. 47 CFR 90.317 - Fixed ancillary signaling and data transmissions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Fixed ancillary signaling and data transmissions. 90.317 Section 90.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz...

  18. 47 CFR 90.317 - Fixed ancillary signaling and data transmissions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Fixed ancillary signaling and data transmissions. 90.317 Section 90.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz...

  19. 47 CFR 90.317 - Fixed ancillary signaling and data transmissions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Fixed ancillary signaling and data transmissions. 90.317 Section 90.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz...

  20. 47 CFR 90.317 - Fixed ancillary signaling and data transmissions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Fixed ancillary signaling and data transmissions. 90.317 Section 90.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz...

  1. Power-efficient method for IM-DD optical transmission of multiple OFDM signals.

    PubMed

    Effenberger, Frank; Liu, Xiang

    2015-05-18

    We propose a power-efficient method for transmitting multiple frequency-division multiplexed (FDM) orthogonal frequency-division multiplexing (OFDM) signals in intensity-modulation direct-detection (IM-DD) optical systems. This method is based on quadratic soft clipping in combination with odd-only channel mapping. We show, both analytically and experimentally, that the proposed approach is capable of improving the power efficiency by about 3 dB as compared to conventional FDM OFDM signals under practical bias conditions, making it a viable solution in applications such as optical fiber-wireless integrated systems where both IM-DD optical transmission and OFDM signaling are important. PMID:26074605

  2. Allosteric inhibition of Epac: computational modeling and experimental validation to identify allosteric sites and inhibitors.

    PubMed

    Brown, Loren M; Rogers, Kathleen E; Aroonsakool, Nakon; McCammon, J Andrew; Insel, Paul A

    2014-10-17

    Epac, a guanine nucleotide exchange factor for the low molecular weight G protein Rap, is an effector of cAMP signaling and has been implicated to have roles in numerous diseases, including diabetes mellitus, heart failure, and cancer. We used a computational molecular modeling approach to predict potential binding sites for allosteric modulators of Epac and to identify molecules that might bind to these regions. This approach revealed that the conserved hinge region of the cyclic nucleotide-binding domain of Epac1 is a potentially druggable region of the protein. Using a bioluminescence resonance energy transfer-based assay (CAMYEL, cAMP sensor using YFP-Epac-Rluc), we assessed the predicted compounds for their ability to bind Epac and modulate its activity. We identified a thiobarbituric acid derivative, 5376753, that allosterically inhibits Epac activity and used Swiss 3T3 and HEK293 cells to test the ability of this compound to modulate the activity of Epac and PKA, as determined by Rap1 activity and vasodilator-stimulated phosphoprotein phosphorylation, respectively. Compound 5376753 selectively inhibited Epac in biochemical and cell migration studies. These results document the utility of a computational approach to identify a domain for allosteric regulation of Epac and a novel compound that prevents the activation of Epac1 by cAMP. PMID:25183009

  3. A biologically motivated signal transmission approach based on stochastic delay differential equation

    NASA Astrophysics Data System (ADS)

    Xu, Mingdong; Wu, Fan; Leung, Henry

    2009-09-01

    Based on the stochastic delay differential equation (SDDE) modeling of neural networks, we propose an effective signal transmission approach along the neurons in such a network. Utilizing the linear relationship between the delay time and the variance of the SDDE system output, the transmitting side encodes a message as a modulation of the delay time and the receiving end decodes the message by tracking the delay time, which is equivalent to estimating the variance of the received signal. This signal transmission approach turns out to follow the principle of the spread spectrum technique used in wireless and wireline wideband communications but in the analog domain rather than digital. We hope the proposed method might help to explain some activities in biological systems. The idea can further be extended to engineering applications. The error performance of the communication scheme is also evaluated here.

  4. Transmission of multi-polarization-multiplexed signals: another freedom to explore?

    PubMed

    Chen, Zhiyu; Yan, Lianshan; Pan, Wei; Luo, Bin; Guo, Yinghui; Jiang, Hengyun; Yi, Anlin; Sun, Yafei; Wu, Xiaoxia

    2013-05-01

    We propose a configuration of signal multiplexing with four polarization states, and investigate its transmission performance over single-mode-fiber links. Assisted by coherent detection and digital signal processing (DSP), the demodulation of four-polarization multiplexed (4PM) on-off-keying (OOK) and phase-shift-keying (PSK) signals are achieved. We then discuss the impact of the crosstalk from polarization mode dispersion (PMD) on 4PM systems. The transmission distance is extended from ~50-km to ~80 km by employing feedback-decision-equalizers. We also compare the back-to-back characteristics of the 40-Gbit/s 4PM-OOK system and 40-Gbit/s PDM-QPSK system with the same spectral efficiency. The results show that the performance of 4PM systems is comparable to that of PDM-QPSK systems, which indicates that the proposed scheme is a potentially promising candidate for future optical networks. PMID:23670016

  5. 29 CFR 1926.1420 - Signals-radio, telephone or other electronic transmission of signals.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CONSTRUCTION Cranes and Derricks in Construction § 1926.1420 Signals—radio, telephone or other electronic... must be through a dedicated channel, except: (1) Multiple cranes/derricks and one or more signal persons may share a dedicated channel for the purpose of coordinating operations. (2) Where a crane...

  6. 29 CFR 1926.1420 - Signals-radio, telephone or other electronic transmission of signals.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CONSTRUCTION Cranes and Derricks in Construction § 1926.1420 Signals—radio, telephone or other electronic... must be through a dedicated channel, except: (1) Multiple cranes/derricks and one or more signal persons may share a dedicated channel for the purpose of coordinating operations. (2) Where a crane...

  7. 29 CFR 1926.1420 - Signals-radio, telephone or other electronic transmission of signals.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... CONSTRUCTION Cranes and Derricks in Construction § 1926.1420 Signals—radio, telephone or other electronic... must be through a dedicated channel, except: (1) Multiple cranes/derricks and one or more signal persons may share a dedicated channel for the purpose of coordinating operations. (2) Where a crane...

  8. 29 CFR 1926.1420 - Signals-radio, telephone or other electronic transmission of signals.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... CONSTRUCTION Cranes and Derricks in Construction § 1926.1420 Signals—radio, telephone or other electronic... must be through a dedicated channel, except: (1) Multiple cranes/derricks and one or more signal persons may share a dedicated channel for the purpose of coordinating operations. (2) Where a crane...

  9. Doing justice to allosteric regulation.

    PubMed

    Keller, Evelyn Fox

    2015-06-01

    Jacques Monod gave us not only our first regulatory system, but also our first smart molecules - i.e., he gave us allosteric proteins. But both of these contributions hung in a certain tension with his primary commitments. In particular, I focus here on the ways in which his ontological commitments constrained his thinking about the power of allostery. Although he wrote that "so far as regulation through allosteric interaction is concerned, everything is possible", for him, not everything was conceivable. In particular, what was not conceivable was a challenge to the primacy of DNA. PMID:25908117

  10. Signal transmission through the CXC chemokine receptor 4 (CXCR4) transmembrane helices.

    PubMed

    Wescott, Melanie P; Kufareva, Irina; Paes, Cheryl; Goodman, Jason R; Thaker, Yana; Puffer, Bridget A; Berdougo, Eli; Rucker, Joseph B; Handel, Tracy M; Doranz, Benjamin J

    2016-08-30

    The atomic-level mechanisms by which G protein-coupled receptors (GPCRs) transmit extracellular ligand binding events through their transmembrane helices to activate intracellular G proteins remain unclear. Using a comprehensive library of mutations covering all 352 residues of the GPCR CXC chemokine receptor 4 (CXCR4), we identified 41 amino acids that are required for signaling induced by the chemokine ligand CXCL12 (stromal cell-derived factor 1). CXCR4 variants with each of these mutations do not signal properly but remain folded, based on receptor surface trafficking, reactivity to conformationally sensitive monoclonal antibodies, and ligand binding. When visualized on the structure of CXCR4, the majority of these residues form a continuous intramolecular signaling chain through the transmembrane helices; this chain connects chemokine binding residues on the extracellular side of CXCR4 to G protein-coupling residues on its intracellular side. Integrated into a cohesive model of signal transmission, these CXCR4 residues cluster into five functional groups that mediate (i) chemokine engagement, (ii) signal initiation, (iii) signal propagation, (iv) microswitch activation, and (v) G protein coupling. Propagation of the signal passes through a "hydrophobic bridge" on helix VI that coordinates with nearly every known GPCR signaling motif. Our results agree with known conserved mechanisms of GPCR activation and significantly expand on understanding the structural principles of CXCR4 signaling. PMID:27543332

  11. The allosteric communication pathways in KIX domain of CBP

    PubMed Central

    Palazzesi, Ferruccio; Barducci, Alessandro; Tollinger, Martin; Parrinello, Michele

    2013-01-01

    Allosteric regulation plays an important role in a myriad of biomacromolecular processes. Specifically, in a protein, the process of allostery refers to the transmission of a local perturbation, such as ligand binding, to a distant site. Decades after the discovery of this phenomenon, models built on static images of proteins are being reconsidered with the knowledge that protein dynamics plays an important role in its function. Molecular dynamics simulations are a valuable tool for studying complex biomolecular systems, providing an atomistic description of their structure and dynamics. Unfortunately, their predictive power has been limited by the complexity of the biomolecule free-energy surface and by the length of the allosteric timescale (in the order of milliseconds). In this work, we are able to probe the origins of the allosteric changes that transcription factor mixed lineage leukemia (MLL) causes to the interactions of KIX domain of CREB-binding protein (CBP) with phosphorylated kinase inducible domain (pKID), by combing all-atom molecular dynamics with enhanced sampling methods recently developed in our group. We discuss our results in relation to previous NMR studies. We also develop a general simulations protocol to study allosteric phenomena and many other biological processes that occur in the micro/milliseconds timescale. PMID:23940332

  12. Structural mechanism for signal transduction in RXR nuclear receptor heterodimers

    PubMed Central

    Kojetin, Douglas J.; Matta-Camacho, Edna; Hughes, Travis S.; Srinivasan, Sathish; Nwachukwu, Jerome C.; Cavett, Valerie; Nowak, Jason; Chalmers, Michael J.; Marciano, David P.; Kamenecka, Theodore M.; Shulman, Andrew I.; Rance, Mark; Griffin, Patrick R.; Bruning, John B.; Nettles, Kendall W.

    2015-01-01

    A subset of nuclear receptors (NRs) function as obligate heterodimers with retinoid X receptor (RXR), allowing integration of ligand-dependent signals across the dimer interface via an unknown structural mechanism. Using nuclear magnetic resonance (NMR) spectroscopy, x-ray crystallography and hydrogen/deuterium exchange (HDX) mass spectrometry, here we show an allosteric mechanism through which RXR co-operates with a permissive dimer partner, peroxisome proliferator-activated receptor (PPAR)-γ, while rendered generally unresponsive by a non-permissive dimer partner, thyroid hormone (TR) receptor. Amino acid residues that mediate this allosteric mechanism comprise an evolutionarily conserved network discovered by statistical coupling analysis (SCA). This SCA network acts as a signalling rheostat to integrate signals between dimer partners, ligands and coregulator-binding sites, thereby affecting signal transmission in RXR heterodimers. These findings define rules guiding how NRs integrate two ligand-dependent signalling pathways into RXR heterodimer-specific responses. PMID:26289479

  13. Call Transmission Efficiency in Native and Invasive Anurans: Competing Hypotheses of Divergence in Acoustic Signals

    PubMed Central

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2–5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a

  14. Call transmission efficiency in native and invasive anurans: competing hypotheses of divergence in acoustic signals.

    PubMed

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2-5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a less

  15. Computational quest for understanding the role of astrocyte signaling in synaptic transmission and plasticity

    PubMed Central

    De Pittà, Maurizio; Volman, Vladislav; Berry, Hugues; Parpura, Vladimir; Volterra, Andrea; Ben-Jacob, Eshel

    2012-01-01

    The complexity of the signaling network that underlies astrocyte-synapse interactions may seem discouraging when tackled from a theoretical perspective. Computational modeling is challenged by the fact that many details remain hitherto unknown and conventional approaches to describe synaptic function are unsuitable to explain experimental observations when astrocytic signaling is taken into account. Supported by experimental evidence is the possibility that astrocytes perform genuine information processing by means of their calcium signaling and are players in the physiological setting of the basal tone of synaptic transmission. Here we consider the plausibility of this scenario from a theoretical perspective, focusing on the modulation of synaptic release probability by the astrocyte and its implications on synaptic plasticity. The analysis of the signaling pathways underlying such modulation refines our notion of tripartite synapse and has profound implications on our understanding of brain function. PMID:23267326

  16. Transmission and reception of PDM dual-subcarrier coherent 16QAM-OFDM signals

    NASA Astrophysics Data System (ADS)

    Li, Fan; Zhang, Junwen; Yu, Jianjun; Li, Xinying

    2015-12-01

    In this paper, 16-Gbaud polarization-division-multiplexed (PDM) dual-subcarrier coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission and reception are successfully demonstrated without overhead. The in-phase and quadrature (I/Q) components of dual-subcarrier 16-ary quadrature amplitude modulation (QAM) OFDM signal are both seven-level signals in time domain, and thus can be equalized like a 49 QAM signal in time domain with cascaded multi-modulus algorithm (CMMA) equalization method. The experimental results show that there is no power penalty observed between optical back to back (OBTB) and after 80-km single-mode fiber-28 (SMF-28) with time domain CMMA equalization method. A 0.4 dB optical signal to noise ratio (OSNR) penalty in OBTB is observed when the bandwidth of channel is set at 26 GHz at the BER of 2.0 × 10-2.

  17. Optical radio-photonic channel for transmission of a coherent narrowband analog signal

    NASA Astrophysics Data System (ADS)

    Zhuk, D. I.; Denisyuk, I. Yu.; Fokina, M. I.

    2015-10-01

    The channel of an optical transmission line of coherent narrowband analog signal consisting of a continuous-wave laser, an electro-optic modulator, and a vector phase rotator based on electrically controlled fiber-optical 1 × 2 splitter and fixed delay lines is analyzed. The scheme is constructed from commercially available components used in digital optical communication systems. The applicability of components for analog and small-signal circuits is determined. Variation of radio signal phase in the range from 0° to 170° for radio signal frequencies between 1 and 2 GHz is demonstrated experimentally. It is shown that phase variation is a linear function of frequency in this range.

  18. SETI: The transmission rate of radio communication and the signal's detection

    NASA Astrophysics Data System (ADS)

    Fridman, P. A.

    2011-11-01

    The transmission rate of communication between radio telescopes on Earth and extraterrestrial intelligence (ETI) is here calculated up to distances of 1000 light years. Both phase-shift keying (PSK) and frequency-shift keying (FSK) modulation schemes are considered. It is shown that M-ary FSK is advantageous in terms of energy. Narrow-band pulses scattered over the spectrum sharing a common drift rate can be the probable signals of ETI. Modern SETI spectrum analyzers are well suited to searching for these types of signals. Such signals can be detected using the Hough transform which is a dedicated tool for detecting patterns in an image. The time-frequency plane representing the power output of the spectrum analyzer during the search for ETI gives an image from which the Hough transform (HT) can detect signal patterns with frequency drift.

  19. Optical diversity transmission using WDM signal and phase-conjugate lights through multi-core fiber.

    PubMed

    Koga, Masafumi; Moroi, Mitsuki; Takara, Hidehiko

    2016-05-01

    This paper proposes a maximum-ratio combining (MRC) scheme for a WDM signal and phase-conjugate pair (PCP) diversity transmission to cancel nonlinear phase-shift. A transfer function approximation for nonlinear phase-shift cancellation is formulated. It shows, with the help of a numerical calculation, that span-by-span chromatic dispersion compensation is more effective than the lumped equivalent at the receiver. This is confirmed in a 2-core diversity 5 channel WDM transmission experiment over 3-spans of 60km MCF with 25 Gbit/s-QPSK PCP. The peak Q-value was enhanced by 3.6dB through MRC, resulting in superior bitrate-distance product and optical power density limit, compared to twice the single core transmission. PMID:27137550

  20. Functional anatomy of an allosteric protein

    NASA Astrophysics Data System (ADS)

    Purohit, Prasad; Gupta, Shaweta; Jadey, Snehal; Auerbach, Anthony

    2013-12-01

    Synaptic receptors are allosteric proteins that switch on and off to regulate cell signalling. Here, we use single-channel electrophysiology to measure and map energy changes in the gating conformational change of a nicotinic acetylcholine receptor. Two separated regions in the α-subunits—the transmitter-binding sites and αM2-αM3 linkers in the membrane domain—have the highest ϕ-values (change conformation the earliest), followed by the extracellular domain, most of the membrane domain and the gate. Large gating-energy changes occur at the transmitter-binding sites, α-subunit interfaces, the αM1 helix and the gate. We hypothesize that rearrangements of the linkers trigger the global allosteric transition, and that the hydrophobic gate unlocks in three steps. The mostly local character of side-chain energy changes and the similarly high ϕ-values of separated domains, both with and without ligands, suggest that gating is not strictly a mechanical process initiated by the affinity change for the agonist.

  1. Transmission Experiment of 80-Gbit/s-Based WDM Signals Using an OPGW in the Field and In-service Chromatic Dispersion Monitering through Envelope Modulated WDM Signals

    NASA Astrophysics Data System (ADS)

    Yamashita, Ikuo; Oro, Kyoichi; Seikai, Shigeyuki

    A field experiment on transmission of 80-Gbit/s-based wavelength division multiplexing (WDM) signals is successfully carried out. In order to keep good transmission quality, technique of an in-service dispersion monitoring and an adaptive control of the chromatic dispersion are proposed. Difference of the propagation delay between channels caused by the chromatic dispersion of the transmission line is detected using signals superimposed on the envelope of the WDM pulses. Dispersion alteration of the transmission line is estimated from the measured delay in real-time. Accuracy of the method is clarified through a transmission experiment using wound fibers in an oven changing their temperature. The field experiment on 80Gbit/s × 8WDM transmission using an OPGW with 60km × 2spans is carried out and fine BER performances are obtained in all channels. Transmission properties are found to be stable owing to the dispersion control techniques throughout the field trial.

  2. Heaviside revisited: Distortionless signal transmission through lossy media with application to precision clock synchronization

    NASA Astrophysics Data System (ADS)

    Flake, Robert H.

    2016-02-01

    A recently discovered non-sinusoidal, non-periodic electrical signal in the form of an exponentially rising pulse achieves distortionless propagation at constant velocity through lossy, passive transmission media. This unique property is derived theoretically in the framework of the telegrapher's equation analyzed by Heaviside and confirmed experimentally in propagation of such a pulse along serially connected sections of telephone cable. The utility of the distortion-free pulse within the field of time-domain reflectometry is demonstrated in precise time-of-flight measurement of the reflected signal, with the prospect of enhancing the accuracy of protocols for synchronization of spatially separated clocks.

  3. Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

    NASA Astrophysics Data System (ADS)

    Garba, Aminata A.; Yim, Raymond M. H.; Bajcsy, Jan; Chen, Lawrence R.

    2005-12-01

    We present performance limits of the optical code-division multiple-access (OCDMA) networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD) is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless) case, and extend this analysis to the case when additive white Gaussian noise (AWGN) is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and[InlineEquation not available: see fulltext.]-ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences) with good bit error rate system performance.

  4. Signal transmission techniques for large-scale nuclear fuel reprocessing applications

    SciTech Connect

    Herndon, J.N.; Bible, D.W.

    1985-01-01

    The RCE is currently developing a prototypic microwave-based signal transmission system for reprocessing cell applications. This system, being developed for use in the Advanced Integrated Maintenance System (AIMS), will operate in the 10-GHz frequency range. Provisions are being made for five real-time video channels, three bidirectional data channels at one megabaud data rate each, and two audio channels. The basic utility of the concept has been proven in a laboratory demonstration using gallium arsenide gunn diode transmitter/receivers with horn antennas. Unidirectional transmission of one real-time video channel over a distance of 200 ft was demonstrated. No evidence of multipath interference was detected even when the transmission path was surrounded by metallic reflectors. The microwave signal transmission system for the AIMS application is in final design. Fabrication in the ORNL instrument shops will begin in October 1985, and the system should be operational in the Maintenance Systems Test Area (MSTA) at ORNL in the latter half of 1986.

  5. Long-distance signal transmission and regulation of photosynthesis in characean cells.

    PubMed

    Bulychev, A A; Komarova, A V

    2014-03-01

    Photosynthetic electron transport in an intact cell is finely regulated by the structural flexibility of thylakoid membranes, existence of alternative electron-transport pathways, generation of electrochemical proton gradient, and continuous exchange of ions and metabolites between cell organelles and the cytoplasm. Long-distance interactions underlying reversible transitions of photosynthetic activity between uniform and spatially heterogeneous distributions are of particular interest. Microfluorometric studies of characean cells with the use of saturating light pulses and in combination with electrode micromethods revealed three mechanisms of distant regulation ensuring functional coordination of cell domains and signal transmission over long distances. These include: (1) circulation of electric currents between functionally distinct cell domains, (2) propagation of action potential along the cell length, and (3) continuous cyclical cytoplasmic streaming. This review considers how photosynthetic activity depends on membrane transport of protons and cytoplasmic pH, on ion fluxes associated with the electrical excitation of the plasmalemma, and on the transmission of photoinduced signals with streaming cytoplasm. Because of signal transmission with cytoplasmic flow, dynamic changes in photosynthetic activity can develop far from the point of photostimulus application and with a long delay (up to 100 s) after a light pulse stimulus is extinguished. PMID:24821454

  6. Enhanced GABA Transmission Drives Bradykinesia Following Loss of Dopamine D2 Receptor Signaling.

    PubMed

    Lemos, Julia C; Friend, Danielle M; Kaplan, Alanna R; Shin, Jung Hoon; Rubinstein, Marcelo; Kravitz, Alexxai V; Alvarez, Veronica A

    2016-05-18

    Bradykinesia is a prominent phenotype of Parkinson's disease, depression, and other neurological conditions. Disruption of dopamine (DA) transmission plays an important role, but progress in understanding the exact mechanisms driving slowness of movement has been impeded due to the heterogeneity of DA receptor distribution on multiple cell types within the striatum. Here we show that selective deletion of DA D2 receptors (D2Rs) from indirect-pathway medium spiny neurons (iMSNs) is sufficient to impair locomotor activity, phenocopying DA depletion models of Parkinson's disease, despite this mouse model having intact DA transmission. There was a robust enhancement of GABAergic transmission and a reduction of in vivo firing in striatal and pallidal neurons. Mimicking D2R signaling in iMSNs with Gi-DREADDs restored the level of tonic GABAergic transmission and rescued the motor deficit. These findings indicate that DA, through D2R activation in iMSNs, regulates motor output by constraining the strength of GABAergic transmission. PMID:27196975

  7. The Mechanism of Allosteric Inhibition of Protein Tyrosine Phosphatase 1B

    PubMed Central

    Lu, Shaoyong; Huang, Wenkang; Geng, Lv; Shen, Qiancheng; Zhang, Jian

    2014-01-01

    As the prototypical member of the PTP family, protein tyrosine phosphatase 1B (PTP1B) is an attractive target for therapeutic interventions in type 2 diabetes. The extremely conserved catalytic site of PTP1B renders the design of selective PTP1B inhibitors intractable. Although discovered allosteric inhibitors containing a benzofuran sulfonamide scaffold offer fascinating opportunities to overcome selectivity issues, the allosteric inhibitory mechanism of PTP1B has remained elusive. Here, molecular dynamics (MD) simulations, coupled with a dynamic weighted community analysis, were performed to unveil the potential allosteric signal propagation pathway from the allosteric site to the catalytic site in PTP1B. This result revealed that the allosteric inhibitor compound-3 induces a conformational rearrangement in helix α7, disrupting the triangular interaction among helix α7, helix α3, and loop11. Helix α7 then produces a force, pulling helix α3 outward, and promotes Ser190 to interact with Tyr176. As a result, the deviation of Tyr176 abrogates the hydrophobic interactions with Trp179 and leads to the downward movement of the WPD loop, which forms an H-bond between Asp181 and Glu115. The formation of this H-bond constrains the WPD loop to its open conformation and thus inactivates PTP1B. The discovery of this allosteric mechanism provides an overall view of the regulation of PTP1B, which is an important insight for the design of potent allosteric PTP1B inhibitors. PMID:24831294

  8. Segmented silicon MZM for PAM-8 transmissions at 114 Gb/s with binary signaling.

    PubMed

    Simard, A D; Filion, B; Patel, D; Plant, D; LaRochelle, S

    2016-08-22

    We experimentally demonstrate PAM-8 generation from binary electrical signals driving a silicon multi-electrode Mach-Zehnder modulator acting as an optical digital-to-analog converter. Measured BER in back-to-back configuration is used to evaluate signal quality. We demonstrate 38 GBd PAM-8 transmission below the forward error correction (FEC) threshold using minimum mean square error (MMSE) equalization. The results show that modulators with segmented phase shifters can be advantageously used to eliminate the need for high bandwidth electronic digital-to-analog converters in the generation of multilevel signals. These modulators, that can be designed and fabricated with standard CMOS compatible tools and processes, are of high interest for short range high-speed data links. PMID:27557224

  9. The Effect of Habitat Acoustics on Common Marmoset Vocal Signal Transmission

    PubMed Central

    MORRILL, RYAN J.; THOMAS, A. WREN; SCHIEL, NICOLA; SOUTO, ANTONIO; MILLER, CORY T.

    2013-01-01

    Noisy acoustic environments present several challenges for the evolution of acoustic communication systems. Among the most significant is the need to limit degradation of spectro-temporal signal structure in order to maintain communicative efficacy. This can be achieved by selecting for several potentially complementary processes. Selection can act on behavioral mechanisms permitting signalers to control the timing and occurrence of signal production to avoid acoustic interference. Likewise, the signal itself may be the target of selection, biasing the evolution of its structure to comprise acoustic features that avoid interference from ambient noise or degrade minimally in the habitat. Here, we address the latter topic for common marmoset (Callithrix jacchus) long-distance contact vocalizations, known as phee calls. Our aim was to test whether this vocalization is specifically adapted for transmission in a species-typical forest habitat, the Atlantic forests of northeastern Brazil. We combined seasonal analyses of ambient habitat acoustics with experiments in which pure tones, clicks, and vocalizations were broadcast and rerecorded at different distances to characterize signal degradation in the habitat. Ambient sound was analyzed from intervals throughout the day and over rainy and dry seasons, showing temporal regularities across varied timescales. Broadcast experiment results indicated that the tone and click stimuli showed the typically inverse relationship between frequency and signaling efficacy. Although marmoset phee calls degraded over distance with marked predictability compared with artificial sounds, they did not otherwise appear to be specially designed for increased transmission efficacy or minimal interference in this habitat. We discuss these data in the context of other similar studies and evidence of potential behavioral mechanisms for avoiding acoustic interference in order to maintain effective vocal communication in common marmosets. PMID

  10. Light-activated DNA binding in a designed allosteric protein

    SciTech Connect

    Strickland, Devin; Moffat, Keith; Sosnick, Tobin R.

    2008-09-03

    An understanding of how allostery, the conformational coupling of distant functional sites, arises in highly evolvable systems is of considerable interest in areas ranging from cell biology to protein design and signaling networks. We reasoned that the rigidity and defined geometry of an {alpha}-helical domain linker would make it effective as a conduit for allosteric signals. To test this idea, we rationally designed 12 fusions between the naturally photoactive LOV2 domain from Avena sativa phototropin 1 and the Escherichia coli trp repressor. When illuminated, one of the fusions selectively binds operator DNA and protects it from nuclease digestion. The ready success of our rational design strategy suggests that the helical 'allosteric lever arm' is a general scheme for coupling the function of two proteins.

  11. Allosteric Modulation of Muscarinic Acetylcholine Receptors

    PubMed Central

    Jakubík, Jan; El-Fakahany, Esam E.

    2010-01-01

    An allosteric modulator is a ligand that binds to an allosteric site on the receptor and changes receptor conformation to produce increase (positive cooperativity) or decrease (negative cooperativity) in the binding or action of an orthosteric agonist (e.g., acetylcholine). Since the identification of gallamine as the first allosteric modulator of muscarinic receptors in 1976, this unique mode of receptor modulation has been intensively studied by many groups. This review summarizes over 30 years of research on the molecular mechanisms of allosteric interactions of drugs with the receptor and for new allosteric modulators of muscarinic receptors with potential therapeutic use. Identification of positive modulators of acetylcholine binding and function that enhance neurotransmission and the discovery of highly selective allosteric modulators are mile-stones on the way to novel therapeutic agents for the treatment of schizophrenia, Alzheimer’s disease and other disorders involving impaired cognitive function.

  12. Corticomuscular Transmission of Tremor Signals by Propriospinal Neurons in Parkinson's Disease

    PubMed Central

    Hao, Manzhao; He, Xin; Xiao, Qin; Alstermark, Bror; Lan, Ning

    2013-01-01

    Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD). But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN) in C3–C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG) of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA) model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the neuromuscular dynamics

  13. Terabit Nyquist PDM-32QAM signal transmission with training sequence based time domain channel estimation.

    PubMed

    Zhang, Fan; Wang, Dan; Ding, Rui; Chen, Zhangyuan

    2014-09-22

    We propose a time domain structure of channel estimation for coherent optical communication systems, which employs training sequence based equalizer and is transparent to arbitrary quadrature amplitude modulation (QAM) formats. Enabled with this methodology, 1.02 Tb/s polarization division multiplexed 32 QAM Nyquist pulse shaping signal with a net spectral efficiency of 7.46 b/s/Hz is transmitted over standard single-mode fiber link with Erbium-doped fiber amplifier only amplification. After 1190 km transmission, the average bit-error rate is lower than the 20% hard-decision forward error correction threshold of 1.5 × 10(-2). The transmission distance can be extended to 1428 km by employing intra-subchannel nonlinear compensation with the digital back-propagation method. PMID:25321810

  14. Multiplex transmission system for gate drive signals of inverter circuit using surface acoustic wave filters

    NASA Astrophysics Data System (ADS)

    Suzuki, Akifumi; Ueda, Kensuke; Goka, Shigeyoshi; Wada, Keiji; Kakio, Shoji

    2016-07-01

    We propose and fabricate a multiplexed transmission system based on frequency-division multiple access (FDMA) with surface acoustic wave (SAW) filters. SAW filters are suitable for use in wide-gap switching devices and multilevel inverters because of their capability to operate at high temperatures, good electrical isolation, low cost, and high reliability. Our proposed system reduces the number of electrical signal wires needed to control each switching device and eliminates the need for isolation circuits, simplifying the transmission system and gate drive circuits. We successfully controlled two switching devices with a single coaxial line and confirmed the operation of a single-phase half-bridge inverter at a supply voltage of 100 V, and the total delay time to control the switching devices was less than 2.5 µs. Our experimental results validated our proposed system.

  15. Low power wireless ultra-wide band transmission of bio-signals

    NASA Astrophysics Data System (ADS)

    Gabrielli, A.; Bastianini, S.; Crepaldi, M.; D'Amen, G.; Demarchi, D.; Lax, I.; Motto Ros, P.; Zoccoli, G.

    2014-12-01

    The paper shows the design of microelectronic circuits composed of an oscillator, a modulator, a transmitter and an antenna. Prototype chips were recently fabricated and tested exploiting commercial 130 nm [1] and 180 nm [2,3] CMOS technologies. Detected signals have been measured using a commercial Ultra-Wide-Band amplifier connected to custom designed filters and a digital demodulator. Preliminary results are summarized along with some waveforms of the transmitted and received signals. A digital Synchronized On-Off Keying (S-OOK) was implemented to exploit the Ultra-Wide-Band transmission. In this way, each transmitted bit is coded with a S-OOK protocol. Wireless transmission capabilities of the system have been also evaluated within a one-meter distance. The chips fit a large variety of applications like spot radiation monitoring, punctual measurements of radiation in High-Energy Physics experiments or, since they have been characterized as low-power components, readout of the system for medical applications. These latter fields are those that we are investigating for in-vivo measurements on small animals. In more detail, if we refer to electromyographic, electrocardiographic or electroencephalographic signals [4], we need to handle very small signal amplitudes, of the order of tens of μV, overwhelmed with a much higher (white) noise. In these cases the front-end of the readout circuit requires a so-called amplifier for instrumentation, here not described, to interface with metal-plate sensor's outputs such those used for electrocardiograms, to normal range of amplitude signals of the order of 1 V. We are also studying these circuits, to be also designed on a microelectronic device, without adding further details since these components are technically well known in the literature [5,6]. The main aim of this research is hence integrating all the described electronic components into a very small, low-powered, microelectronic circuit fully compatible with in

  16. In-band simultaneous transmission of baseband and broadcast signals in wavelength reused bidirectional passive optical network

    NASA Astrophysics Data System (ADS)

    Choudhury, Pallab K.

    2015-11-01

    Reflective semiconductor optical amplifier (RSOA) based bidirectional wavelength division multiplexing passive optical network (WDM-PON) is proposed and analyzed for broadcasting services along with conventional baseband signal. The downstream baseband signal is spectrally shaped for in-band transmission of broadcast signal, which ensures effective utilization of transmission bandwidth. The modulated downstream optical signal is further reused for upstream data modulation and transmitted over the same fiber with suppressed re-modulation and rayleigh backscattering noises. The proposed WDM-PON is successfully demonstrated for 10 Gb/s downstream baseband signal, 100 Mb/s 16-QAM (quadrature amplitude modulation) in-band broadcast signal and wavelength reused 1.25 Gb/s upstream signal. Error free operation for both the baseband signals as well as low value of error vector magnitude (EVM) for broadcast data are simultaneously achieved in acceptable receiver sensitivity.

  17. Modulator bias control based on dither signal in 40Gb/s RZ optical transmission system

    NASA Astrophysics Data System (ADS)

    Zhang, Jianyong; Wang, Muguang; Fu, Yongjun; Cao, Jihong; Qin, Xi; Zhang, Feng; Jian, Shuisheng

    2008-11-01

    The bias drift effect in the packaged LiNbO3 modulator is investigated. The Bessel expansion of the dithered clock shows that the harmonic component equal to the dither frequency can be synchronously demodulated to get the bias drift and avoid the random phase difference between the clock or data and the dither signal. By using the time division control method one control system can track two modulator bias drift in 40Gb/s RZ optical transmission system because the optimum bias point changes very slowly.

  18. Wnt signaling pathway improves central inhibitory synaptic transmission in a mouse model of Duchenne muscular dystrophy.

    PubMed

    Fuenzalida, Marco; Espinoza, Claudia; Pérez, Miguel Ángel; Tapia-Rojas, Cheril; Cuitino, Loreto; Brandan, Enrique; Inestrosa, Nibaldo C

    2016-02-01

    The dystrophin-associated glycoprotein complex (DGC) that connects the cytoskeleton, plasma membrane and the extracellular matrix has been related to the maintenance and stabilization of channels and synaptic receptors, which are both essential for synaptogenesis and synaptic transmission. The dystrophin-deficient (mdx) mouse model of Duchenne muscular dystrophy (DMD) exhibits a significant reduction in hippocampal GABA efficacy, which may underlie the altered synaptic function and abnormal hippocampal long-term plasticity exhibited by mdx mice. Emerging studies have implicated Wnt signaling in the modulation of synaptic efficacy, neuronal plasticity and cognitive function. We report here that the activation of the non-canonical Wnt-5a pathway and Andrographolide, improves hippocampal mdx GABAergic efficacy by increasing the number of inhibitory synapses and GABA(A) receptors or GABA release. These results indicate that Wnt signaling modulates GABA synaptic efficacy and could be a promising novel target for DMD cognitive therapy. PMID:26626079

  19. Add/drop multiplexing and TDM signal transmission in an optical CDMA ring network

    NASA Astrophysics Data System (ADS)

    Chen, Biao; Guo, Changjian; Chen, Jiajia; Zhang, Linjian; Jiang, Qiong; He, Sailing

    2007-08-01

    It is shown that a ring topology is better than a star topology for an optical-code-division multiple access (OCDMA) network as an optical metropolitan or local area network in terms of security and capacity. Each node in an OCDMA ring network requires an OCDMA add/drop multiplexer. We present what we believe to be a novel OCDMA add/drop multiplexer that can simultaneously add and drop multiple code channels, and a proof-of-feasibility experiment is demonstrated. An OCDMA ring may also adapt code channels for time domain multiplexing and other digital signal transmission systems. An experiment for the synchronized digital hierarchy (SDH) signal over a OCDMA link is demonstrated.

  20. Gigabit Ethernet signal transmission using asynchronous optical code division multiple access.

    PubMed

    Ma, Philip Y; Fok, Mable P; Shastri, Bhavin J; Wu, Ben; Prucnal, Paul R

    2015-12-15

    We propose and experimentally demonstrate a novel architecture for interfacing and transmitting a Gigabit Ethernet (GbE) signal using asynchronous incoherent optical code division multiple access (OCDMA). This is the first such asynchronous incoherent OCDMA system carrying GbE data being demonstrated to be working among multi-users where each user is operating with an independent clock/data rate and is granted random access to the network. Three major components, the GbE interface, the OCDMA transmitter, and the OCDMA receiver are discussed in detail. The performance of the system is studied and characterized through measuring eye diagrams, bit-error rate and packet loss rate in real-time file transfer. Our Letter also addresses the near-far problem and realizes asynchronous transmission and detection of signal. PMID:26670529

  1. Metabotropic glutamate receptors depress vagal and aortic baroreceptor signal transmission in the NTS.

    PubMed

    Liu, Z; Chen, C Y; Bonham, A C

    1998-11-01

    We sought to determine whether metabotropic glutamate receptors contribute to frequency-dependent depression of vagal and aortic baroreceptor signal transmission in the nucleus of the solitary tract (NTS) in vivo. In alpha-chloralose-anesthetized rabbits, we determined the number of extracellular action potentials synaptically evoked by low (1 Hz)- or high-frequency vagal (3-20 Hz) or aortic depressor nerve (ADN) (6-80 Hz) stimulation and postsynaptically evoked by the ionotropic glutamate receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The metabotropic glutamate receptor agonist (2S,1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I) attenuated NTS responses monosynaptically evoked by 1-Hz vagus stimulation by 34% (n = 25; P = 0.011), while augmenting AMPA-evoked responses by 64% (n = 17; P = 0.026). The metabotropic glutamate receptor antagonist alpha-methyl-4-phosphonophenylglycine (MPPG) did not affect NTS responses to low-frequency vagal stimulation (n = 11) or AMPA (n = 10) but augmented responses to high-frequency stimulation by 50% (n = 25; P = 0.0001). MPPG also augmented NTS responses to high-frequency ADN stimulation by 35% (n = 9; P = 0.048) but did not affect responses to low-frequency stimulation (n = 9) or AMPA (n = 7). The results suggest that metabotropic glutamate receptors, presumably at presynaptic sites, contribute to frequency-dependent depression of vagal and aortic baroreceptor signal transmission in NTS. PMID:9815076

  2. Progressive and Error-Resilient Transmission Strategies for VLC Encoded Signals over Noisy Channels

    NASA Astrophysics Data System (ADS)

    Jégou, Hervé; Guillemot, Christine

    2006-12-01

    This paper addresses the issue of robust and progressive transmission of signals (e.g., images, video) encoded with variable length codes (VLCs) over error-prone channels. This paper first describes bitstream construction methods offering good properties in terms of error resilience and progressivity. In contrast with related algorithms described in the literature, all proposed methods have a linear complexity as the sequence length increases. The applicability of soft-input soft-output (SISO) and turbo decoding principles to resulting bitstream structures is investigated. In addition to error resilience, the amenability of the bitstream construction methods to progressive decoding is considered. The problem of code design for achieving good performance in terms of error resilience and progressive decoding with these transmission strategies is then addressed. The VLC code has to be such that the symbol energy is mainly concentrated on the first bits of the symbol representation (i.e., on the first transitions of the corresponding codetree). Simulation results reveal high performance in terms of symbol error rate (SER) and mean-square reconstruction error (MSE). These error-resilience and progressivity properties are obtained without any penalty in compression efficiency. Codes with such properties are of strong interest for the binarization of[InlineEquation not available: see fulltext.]-ary sources in state-of-the-art image, and video coding systems making use of, for example, the EBCOT or CABAC algorithms. A prior statistical analysis of the signal allows the construction of the appropriate binarization code.

  3. Electrical signal transmission in a bone cell network: the influence of a discrete gap junction

    NASA Technical Reports Server (NTRS)

    Zhang, D.; Weinbaum, S.; Cowin, S. C.

    1998-01-01

    A refined electrical cable model is formulated to investigate the role of a discrete gap junction in the intracellular transmission of electrical signals in an electrically coupled system of osteocytes and osteoblasts in an osteon. The model also examines the influence of the ratio q between the membrane's electrical time constant and the characteristic time of pore fluid pressure, the circular, cylindrical geometry of the osteon, and key simplifying assumptions in our earlier continuous cable model (see Zhang, D., S. C. Cowin, and S. Weinbaum. Electrical signal transmission and gap junction regulation in a bone cell network: A cable model for an osteon. Ann. Biomed. Eng. 25:379-396, 1997). Using this refined model, it is shown that (1) the intracellular potential amplitude at the osteoblastic end of the osteonal cable retains the character of a combination of a low-pass and a high-pass filter as the corner frequency varies in the physiological range; (2) the presence of a discrete gap junction near a resting osteoblast can lead to significant modulation of the intracellular potential and current in the osteoblast for measured values of the gap junction coupling strength; and (3) the circular, cylindrical geometry of the osteon is well simulated by the beam analogy used in Zhang et al.

  4. Cross-inhibition of NMBR and GRPR signaling maintains normal histaminergic itch transmission.

    PubMed

    Zhao, Zhong-Qiu; Wan, Li; Liu, Xian-Yu; Huo, Fu-Quan; Li, Hui; Barry, Devin M; Krieger, Stephanie; Kim, Seungil; Liu, Zhong-Chun; Xu, Jinbin; Rogers, Buck E; Li, Yun-Qing; Chen, Zhou-Feng

    2014-09-10

    We previously showed that gastrin-releasing peptide receptor (GRPR) in the spinal cord is important for mediating nonhistaminergic itch. Neuromedin B receptor (NMBR), the second member of the mammalian bombesin receptor family, is expressed in a largely nonoverlapping pattern with GRPR in the superficial spinal cord, and its role in itch transmission remains unclear. Here, we report that Nmbr knock-out (KO) mice exhibited normal scratching behavior in response to intradermal injection of pruritogens. However, mice lacking both Nmbr and Grpr (DKO mice) showed significant deficits in histaminergic itch. In contrast, the chloroquine (CQ)-evoked scratching behavior of DKO mice is not further reduced compared with Grpr KO mice. These results suggest that NMBR and GRPR could compensate for the loss of each other to maintain normal histamine-evoked itch, whereas GRPR is exclusively required for CQ-evoked scratching behavior. Interestingly, GRPR activity is enhanced in Nmbr KO mice despite the lack of upregulation of Grpr expression; so is NMBR in Grpr KO mice. We found that NMB acts exclusively through NMBR for itch transmission, whereas GRP can signal through both receptors, albeit to NMBR to a much lesser extent. Although NMBR and NMBR(+) neurons are dispensable for histaminergic itch, GRPR(+) neurons are likely to act downstream of NMBR(+) neurons to integrate NMB-NMBR-encoded histaminergic itch information in normal physiological conditions. Together, we define the respective function of NMBR and GRPR in itch transmission, and reveal an unexpected relationship not only between the two receptors but also between the two populations of interneurons in itch signaling. PMID:25209280

  5. CGP7930: a positive allosteric modulator of the GABAB receptor.

    PubMed

    Adams, C L; Lawrence, A J

    2007-01-01

    CGP7930 (3-(3',5'-Di-tert-butyl-4'-hydroxy)phenyl-2,2-dimethylpropanol) is a positive allosteric modulator of the metabotropic GABAB receptor. CGP7930 has been found to modulate the GABAB receptor in the open, or high affinity, state increasing agonist affinity for the receptor and signal transduction efficacy following agonist stimulation. The GABAB heteromeric subunit B2, involved in signal transduction but not ligand binding, seems to be the site of action of CGP7930 and similar allosteric modulators. When administered alone in naïve animals, CGP7930 acts as an anxiolytic in rodents without other overt behavioral effects and has also been demonstrated to reduce self-administration of nicotine, cocaine, or alcohol in rodents, suggesting that "fine tuning" of the GABAB receptor by positive allosteric modulators may be able to regulate abuse of these drugs. Baclofen, the GABAB agonist, is currently finding use in treating addiction and various other disorders, but this can result in off-target effects and tolerance. CGP7930 when co-administered with baclofen enhances its potency, which could in theory minimize deleterious effects. Further study of CGP7930 is required, but this compound, and others like it, holds potential in a clinical setting. PMID:17894647

  6. Allosteric regulation of pentameric ligand-gated ion channels

    PubMed Central

    Taly, Antoine; Hénin, Jérôme; Changeux, Jean-Pierre; Cecchini, Marco

    2014-01-01

    Pentameric ligand-gated ion channels (pLGICs) play a central role in intercellular communications in the nervous system by converting the binding of a chemical messenger—a neurotransmitter—into an ion flux through the postsynaptic membrane. They are oligomeric assemblies that provide prototypical examples of allosterically regulated integral membrane proteins. Here, we present an overview of the most recent advances on the signal transduction mechanism based on the X-ray structures of both prokaryotic and invertebrate eukaryotic pLGICs and on atomistic Molecular Dynamics simulations. The present results suggest that ion gating involves a large structural reorganization of the molecule mediated by two distinct quaternary transitions, a global twisting and the blooming of the extracellular domain, which can be modulated by ligand binding at the topographically distinct orthosteric and allosteric sites. The emerging model of gating is consistent with a wealth of functional studies and will boost the development of novel pharmacological strategies. PMID:25478624

  7. Allosteric Inhibitors at the Heterodimer Interface of Imidazole Glycerol Phosphate Synthase

    NASA Astrophysics Data System (ADS)

    Snoeberger, Ning-Shiuan Nicole

    Imidazole glycerol phosphate synthase (IGPS) from Thermotoga maritima is a heterodimeric enzyme composed of the HisH and HisF proteins. It is attractive as a pathological target since it is absent in mammals but found in plant and opportunistic human pathogens. IGPS was experimentally determined to be a V-type allosteric enzyme that is involved in an essential biosynthetic pathway of microorganisms. The enzyme catalyzes the hydrolysis of glutamine to form NH3 in the HisH protein, followed by cyclization of NH3 with N'-[(5'-phosphoribulosyl)imino]-5-aminoimidazole-4-carboxamide-ribonucleotide (PRFAR) in the HisF subunit, forming imidazole glycerol phosphate (IGP) and 5-aminoimidazole-4-carboxamide ribotide (AICAR) that enter the histidine and purine biosynthetic pathways. Allosteric motions induced upon the binding of the effector PRFAR to HisF propagate through the non-covalent HisH/HisF interface and synchronize catalytic activity at the two distant active sites. However, the nature of the allosteric pathway and the feasibility of manipulating signal transduction by using allosteric drug-like molecules remain to be established. Molecular docking studies of commercial drugs at the HisH/HisF interface were used to identify stable candidates with a potential allosteric effect on the reaction mechanism. Molecular dynamic simulations and calculations of NMR chemical shifts were combined to elucidate the allosteric pathway of IGPS.

  8. Structure-Based Statistical Mechanical Model Accounts for the Causality and Energetics of Allosteric Communication

    PubMed Central

    Guarnera, Enrico; Berezovsky, Igor N.

    2016-01-01

    Allostery is one of the pervasive mechanisms through which proteins in living systems carry out enzymatic activity, cell signaling, and metabolism control. Effective modeling of the protein function regulation requires a synthesis of the thermodynamic and structural views of allostery. We present here a structure-based statistical mechanical model of allostery, allowing one to observe causality of communication between regulatory and functional sites, and to estimate per residue free energy changes. Based on the consideration of ligand free and ligand bound systems in the context of a harmonic model, corresponding sets of characteristic normal modes are obtained and used as inputs for an allosteric potential. This potential quantifies the mean work exerted on a residue due to the local motion of its neighbors. Subsequently, in a statistical mechanical framework the entropic contribution to allosteric free energy of a residue is directly calculated from the comparison of conformational ensembles in the ligand free and ligand bound systems. As a result, this method provides a systematic approach for analyzing the energetics of allosteric communication based on a single structure. The feasibility of the approach was tested on a variety of allosteric proteins, heterogeneous in terms of size, topology and degree of oligomerization. The allosteric free energy calculations show the diversity of ways and complexity of scenarios existing in the phenomenology of allosteric causality and communication. The presented model is a step forward in developing the computational techniques aimed at detecting allosteric sites and obtaining the discriminative power between agonistic and antagonistic effectors, which are among the major goals in allosteric drug design. PMID:26939022

  9. Structure-Based Statistical Mechanical Model Accounts for the Causality and Energetics of Allosteric Communication.

    PubMed

    Guarnera, Enrico; Berezovsky, Igor N

    2016-03-01

    Allostery is one of the pervasive mechanisms through which proteins in living systems carry out enzymatic activity, cell signaling, and metabolism control. Effective modeling of the protein function regulation requires a synthesis of the thermodynamic and structural views of allostery. We present here a structure-based statistical mechanical model of allostery, allowing one to observe causality of communication between regulatory and functional sites, and to estimate per residue free energy changes. Based on the consideration of ligand free and ligand bound systems in the context of a harmonic model, corresponding sets of characteristic normal modes are obtained and used as inputs for an allosteric potential. This potential quantifies the mean work exerted on a residue due to the local motion of its neighbors. Subsequently, in a statistical mechanical framework the entropic contribution to allosteric free energy of a residue is directly calculated from the comparison of conformational ensembles in the ligand free and ligand bound systems. As a result, this method provides a systematic approach for analyzing the energetics of allosteric communication based on a single structure. The feasibility of the approach was tested on a variety of allosteric proteins, heterogeneous in terms of size, topology and degree of oligomerization. The allosteric free energy calculations show the diversity of ways and complexity of scenarios existing in the phenomenology of allosteric causality and communication. The presented model is a step forward in developing the computational techniques aimed at detecting allosteric sites and obtaining the discriminative power between agonistic and antagonistic effectors, which are among the major goals in allosteric drug design. PMID:26939022

  10. Excess signal transmission with dimming control pattern in indoor visible light communication systems

    NASA Astrophysics Data System (ADS)

    Chen, Jian; You, Xiaodi; Zheng, Huanhuan; Yu, Changyuan

    2014-10-01

    In traditional dimming control system using pulse width modulation (PWM) combined with M-QAM OFDM scheme, OFDM signal is only transmitted during "on" period. To guarantee the communication quality, reduction of duty cycle will cause increased symbol rate or added LED power. This means system BER performance degradation and power consumption. In order to solve the defects of the traditional dimming scheme, we propose a new dimming control scheme in indoor visible light communication, which combines OFDM signal and multi-pulse position modulation (MPPM) light pulse well with each other. By means of dividing traditional PWM pulses into MPPM pulses with the same duty cycle, the pattern effect of MPPM pulses is utilized, which makes excess signal transmission possible. Simulation results show that when reducing the brightness of LED the achievable symbol rate using dimming control patterns is not higher than the traditional PWM scheme and the LED power is also reduced, which satisfies both system reliability and energy effectiveness under constant high data rate and BER less than 10-3.

  11. Integration of radio-frequency transmission and radar in general software for multimodal battlefield signal modeling

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kenneth K.; Reznicek, Nathan J.; Wilson, D. Keith

    2013-05-01

    The Environmental Awareness for Sensor and Emitter Employment (EASEE) software, being developed by the U. S. Army Engineer Research and Development Center (ERDC), provides a general platform for predicting sensor performance and optimizing sensor selection and placement in complex terrain and weather conditions. It incorporates an extensive library of target signatures, signal propagation models, and sensor systems. A flexible object-oriented design supports efficient integration and simulation of diverse signal modalities. This paper describes the integration of modeling capabilities for radio-frequency (RF) transmission and radar systems from the U. S. Navy Electromagnetic Propagation Integrated Resource Environment (EMPIRE), which contains nearly twenty different realistic RF propagation models. The integration utilizes an XML-based interface between EASEE and EMPIRE to set inputs for and run propagation models. To accommodate radars, fundamental improvements to the EASEE software architecture were made to support active-sensing scenarios with forward and backward propagation of the RF signals between the radar and target. Models for reflecting targets were defined to apply a target-specific, directionally dependent reflection coefficient (i.e., scattering cross section) to the incident wavefields.

  12. High-frequency signal transmission through single-atom contacts of Au and Pt

    SciTech Connect

    Aoyama, Shodai; Kurokawa, Shu; Sakai, Akira

    2015-03-23

    Signal transmission through atom-sized contacts of Au and Pt has been studied at room temperature for frequencies from 9 kHz to 1 GHz and for conductances (1−10)G{sub 0} (G≡2e{sup 2}/h is the quantum unit of conductance). We measured the frequency spectrum of S parameter S{sub 21}=|S{sub 21}|e{sup iθ} and found θ∼0 up to 1 GHz for all contacts irrespective of their conductance. Our observations directly prove that the atom-sized contacts of Au and Pt, including their single-atom contacts, behave as a pure resistance in the RF regime.

  13. A Physiological Signal Transmission Model to be Used for Specific Diagnosis of Cochlear Impairments

    NASA Astrophysics Data System (ADS)

    Saremi, Amin; Stenfelt, Stefan

    2011-11-01

    Many of the sophisticated characteristics of human auditory system are attributed to cochlea. Also, most of patients with a hearing loss suffer from impairments that originate from cochlea (sensorineural). Despite this, today's clinical diagnosis methods do not probe the specific origins of such cochlear lesions. The aim of this research is to introduce a physiological signal transmission model to be clinically used as a tool for diagnosis of cochlear losses. This model enables simulation of different bio-mechano-electrical processes which occur in the auditory organ of Corti inside the cochlea. What makes this model different from many available computational models is its loyalty to physiology since the ultimate goal is to model each single physiological phenomenon. This includes passive BM vibration, outer hair cells' performances such as nonlinear mechanoelectrical transduction (MET), active amplifications by somatic motor, as well as vibration to neural conversion at the inner hair cells.

  14. A Signal Transmission Technique for Stability Analysis of Multivariable Non-Linear Control Systems

    NASA Technical Reports Server (NTRS)

    Jackson, Mark; Zimpfer, Doug; Adams, Neil; Lindsey, K. L. (Technical Monitor)

    2000-01-01

    Among the difficulties associated with multivariable, non-linear control systems is the problem of assessing closed-loop stability. Of particular interest is the class of non-linear systems controlled with on/off actuators, such as spacecraft thrusters or electrical relays. With such systems, standard describing function techniques are typically too conservative, and time-domain simulation analysis is prohibitively extensive, This paper presents an open-loop analysis technique for this class of non-linear systems. The technique is centered around an innovative use of multivariable signal transmission theory to quantify the plant response to worst case control commands. The technique has been applied to assess stability of thruster controlled flexible space structures. Examples are provided for Space Shuttle attitude control with attached flexible payloads.

  15. Allosteric indicator displacement enzyme assay for a cyanogenic glycoside.

    PubMed

    Jose, D Amilan; Elstner, Martin; Schiller, Alexander

    2013-10-18

    Indicator displacement assays (IDAs) represent an elegant approach in supramolecular analytical chemistry. Herein, we report a chemical biosensor for the selective detection of the cyanogenic glycoside amygdalin in aqueous solution. The hybrid sensor consists of the enzyme β-glucosidase and a boronic acid appended viologen together with a fluorescent reporter dye. β-Glucosidase degrades the cyanogenic glycoside amygdalin into hydrogen cyanide, glucose, and benzaldehyde. Only the released cyanide binds at the allosteric site of the receptor (boronic acid) thereby inducing changes in the affinity of a formerly bound fluorescent indicator dye at the other side of the receptor. Thus, the sensing probe performs as allosteric indicator displacement assay (AIDA) for cyanide in water. Interference studies with inorganic anions and glucose revealed that cyanide is solely responsible for the change in the fluorescent signal. DFT calculations on a model compound revealed a 1:1 binding ratio of the boronic acid and cyanide ion. The fluorescent enzyme assay for β-glucosidase uses amygdalin as natural substrate and allows measuring Michaelis-Menten kinetics in microtiter plates. The allosteric indicator displacement assay (AIDA) probe can also be used to detect cyanide traces in commercial amygdalin samples. PMID:24123550

  16. Computational approaches to detect allosteric pathways in transmembrane molecular machines.

    PubMed

    Stolzenberg, Sebastian; Michino, Mayako; LeVine, Michael V; Weinstein, Harel; Shi, Lei

    2016-07-01

    Many of the functions of transmembrane proteins involved in signal processing and transduction across the cell membrane are determined by allosteric couplings that propagate the functional effects well beyond the original site of activation. Data gathered from breakthroughs in biochemistry, crystallography, and single molecule fluorescence have established a rich basis of information for the study of molecular mechanisms in the allosteric couplings of such transmembrane proteins. The mechanistic details of these couplings, many of which have therapeutic implications, however, have only become accessible in synergy with molecular modeling and simulations. Here, we review some recent computational approaches that analyze allosteric coupling networks (ACNs) in transmembrane proteins, and in particular the recently developed Protein Interaction Analyzer (PIA) designed to study ACNs in the structural ensembles sampled by molecular dynamics simulations. The power of these computational approaches in interrogating the functional mechanisms of transmembrane proteins is illustrated with selected examples of recent experimental and computational studies pursued synergistically in the investigation of secondary active transporters and GPCRs. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. PMID:26806157

  17. Conformationally selective RNA aptamers allosterically modulate the β2-adrenoceptor.

    PubMed

    Kahsai, Alem W; Wisler, James W; Lee, Jungmin; Ahn, Seungkirl; Cahill Iii, Thomas J; Dennison, S Moses; Staus, Dean P; Thomsen, Alex R B; Anasti, Kara M; Pani, Biswaranjan; Wingler, Laura M; Desai, Hemant; Bompiani, Kristin M; Strachan, Ryan T; Qin, Xiaoxia; Alam, S Munir; Sullenger, Bruce A; Lefkowitz, Robert J

    2016-09-01

    G-protein-coupled receptor (GPCR) ligands function by stabilizing multiple, functionally distinct receptor conformations. This property underlies the ability of 'biased agonists' to activate specific subsets of a given receptor's signaling profile. However, stabilizing distinct active GPCR conformations to enable structural characterization of mechanisms underlying GPCR activation remains difficult. These challenges have accentuated the need for receptor tools that allosterically stabilize and regulate receptor function through unique, previously unappreciated mechanisms. Here, using a highly diverse RNA library combined with advanced selection strategies involving state-of-the-art next-generation sequencing and bioinformatics analyses, we identify RNA aptamers that bind a prototypical GPCR, the β2-adrenoceptor (β2AR). Using biochemical, pharmacological, and biophysical approaches, we demonstrate that these aptamers bind with nanomolar affinity at defined surfaces of the receptor, allosterically stabilizing active, inactive, and ligand-specific receptor conformations. The discovery of RNA aptamers as allosteric GPCR modulators significantly expands the diversity of ligands available to study the structural and functional regulation of GPCRs. PMID:27398998

  18. Transmission of Predictable Sensory Signals to the Cerebellum via Climbing Fiber Pathways Is Gated during Exploratory Behavior

    PubMed Central

    Lawrenson, Charlotte L.; Watson, Thomas C.

    2016-01-01

    Pathways arising from the periphery that target the inferior olive [spino-olivocerebellar pathways (SOCPs)] are a vital source of information to the cerebellum and are modulated (gated) during active movements. This limits their ability to forward signals to climbing fibers in the cerebellar cortex. We tested the hypothesis that the temporal pattern of gating is related to the predictability of a sensory signal. Low-intensity electrical stimulation of the ipsilateral hindlimb in awake rats evoked field potentials in the C1 zone in the copula pyramidis of the cerebellar cortex. Responses had an onset latency of 12.5 ± 0.3 ms and were either short or long duration (8.7 ± 0.1 vs 31.2 ± 0.3 ms, respectively). Both types of response were shown to be mainly climbing fiber in origin and therefore evoked by transmission in hindlimb SOCPs. Changes in response size (area of field, millivolts per millisecond) were used to monitor differences in transmission during rest and three phases of rearing: phase 1, rearing up; phase 2, upright; and phase 3, rearing down. Responses evoked during phase 2 were similar in size to rest but were smaller during phases 1 and 3, i.e., transmission was reduced during active movement when self-generated (predictable) sensory signals from the hindlimbs are likely to occur. To test whether the pattern of gating was related to the predictability of the sensory signal, some animals received the hindlimb stimulation only during phase 2. Over ∼10 d, the responses became progressively smaller in size, consistent with gating-out transmission of predictable sensory signals relayed via SOCPs. SIGNIFICANCE STATEMENT A major route for peripheral information to gain access to the cerebellum is via ascending climbing fiber pathways. During active movements, gating of transmission in these pathways controls when climbing fiber signals can modify cerebellar activity. We investigated this phenomenon in rats during their exploratory behavior of rearing

  19. Mutual design of overhead transmission lines and railroad communications and signal systems. Volume 2. Appendixes. Final report

    SciTech Connect

    Taflove, A.; Umashankar, K.R.

    1983-10-01

    Objective was to develop mutual design methods and criteria for overhead ac transmission lines and adjacent railroad systems. This project has addressed basic engineering issues which govern the operation of railroad communications and signal (C and S) systems under conditions of interference from nearby transmission lines. Data and techniques have been compiled and developed to contribute to the achievement of electromagnetic compatibility in a manner that is acceptable to both the power and railroad industries.

  20. Pin1-dependent signalling negatively affects GABAergic transmission by modulating neuroligin2/gephyrin interaction

    PubMed Central

    Antonelli, Roberta; Pizzarelli, Rocco; Pedroni, Andrea; Fritschy, Jean-Marc; Del Sal, Giannino; Cherubini, Enrico; Zacchi, Paola

    2014-01-01

    The cell adhesion molecule Neuroligin2 (NL2) is localized selectively at GABAergic synapses, where it interacts with the scaffolding protein gephyrin in the post-synaptic density. However, the role of this interaction for formation and plasticity of GABAergic synapses is unclear. Here, we demonstrate that endogenous NL2 undergoes proline-directed phosphorylation at its unique S714-P consensus site, leading to the recruitment of the peptidyl-prolyl cis–trans isomerase Pin1. This signalling cascade negatively regulates NL2’s ability to interact with gephyrin at GABAergic post-synaptic sites. As a consequence, enhanced accumulation of NL2, gephyrin and GABAA receptors was detected at GABAergic synapses in the hippocampus of Pin1-knockout mice (Pin1−/−) associated with an increase in amplitude of spontaneous GABAA-mediated post-synaptic currents. Our results suggest that Pin1-dependent signalling represents a mechanism to modulate GABAergic transmission by regulating NL2/gephyrin interaction. PMID:25297980

  1. A dynamically coupled allosteric network underlies binding cooperativity in Src kinase

    NASA Astrophysics Data System (ADS)

    Foda, Zachariah H.; Shan, Yibing; Kim, Eric T.; Shaw, David E.; Seeliger, Markus A.

    2015-01-01

    Protein tyrosine kinases are attractive drug targets because many human diseases are associated with the deregulation of kinase activity. However, how the catalytic kinase domain integrates different signals and switches from an active to an inactive conformation remains incompletely understood. Here we identify an allosteric network of dynamically coupled amino acids in Src kinase that connects regulatory sites to the ATP- and substrate-binding sites. Surprisingly, reactants (ATP and peptide substrates) bind with negative cooperativity to Src kinase while products (ADP and phosphopeptide) bind with positive cooperativity. We confirm the molecular details of the signal relay through the allosteric network by biochemical studies. Experiments on two additional protein tyrosine kinases indicate that the allosteric network may be largely conserved among these enzymes. Our work provides new insights into the regulation of protein tyrosine kinases and establishes a potential conduit by which resistance mutations to ATP-competitive kinase inhibitors can affect their activity.

  2. A dynamically coupled allosteric network underlies binding cooperativity in Src kinase

    PubMed Central

    Foda, Zachariah H.; Shan, Yibing; Kim, Eric T.; Shaw, David E.; Seeliger, Markus A.

    2015-01-01

    Protein tyrosine kinases are attractive drug targets because many human diseases are associated with the deregulation of kinase activity. However, how the catalytic kinase domain integrates different signals and switches from an active to an inactive conformation remains incompletely understood. Here we identify an allosteric network of dynamically coupled amino acids in Src kinase that connects regulatory sites to the ATP- and substrate-binding sites. Surprisingly, reactants (ATP and peptide substrates) bind with negative cooperativity to Src kinase while products (ADP and phosphopeptide) bind with positive cooperativity. We confirm the molecular details of the signal relay through the allosteric network by biochemical studies. Experiments on two additional protein tyrosine kinases indicate that the allosteric network may be largely conserved among these enzymes. Our work provides new insights into the regulation of protein tyrosine kinases and establishes a potential conduit by which resistance mutations to ATP-competitive kinase inhibitors can affect their activity. PMID:25600932

  3. A dynamically coupled allosteric network underlies binding cooperativity in Src kinase.

    PubMed

    Foda, Zachariah H; Shan, Yibing; Kim, Eric T; Shaw, David E; Seeliger, Markus A

    2015-01-01

    Protein tyrosine kinases are attractive drug targets because many human diseases are associated with the deregulation of kinase activity. However, how the catalytic kinase domain integrates different signals and switches from an active to an inactive conformation remains incompletely understood. Here we identify an allosteric network of dynamically coupled amino acids in Src kinase that connects regulatory sites to the ATP- and substrate-binding sites. Surprisingly, reactants (ATP and peptide substrates) bind with negative cooperativity to Src kinase while products (ADP and phosphopeptide) bind with positive cooperativity. We confirm the molecular details of the signal relay through the allosteric network by biochemical studies. Experiments on two additional protein tyrosine kinases indicate that the allosteric network may be largely conserved among these enzymes. Our work provides new insights into the regulation of protein tyrosine kinases and establishes a potential conduit by which resistance mutations to ATP-competitive kinase inhibitors can affect their activity. PMID:25600932

  4. Horizontal transmission of Thelohania contejeani in the endangered white-clawed (Austropotamobius pallipes) and the invasive signal crayfish (Pacifastacus leniusculus).

    PubMed

    Imhoff, Emily M; Mortimer, Robert J G; Christmas, Martin; Dunn, Alison M

    2012-09-01

    The microsporidian parasite Thelohania contejeani causes porcelain disease and has been implicated in mass mortalities in populations of the endangered European crayfish Austropotamobius pallipes. However, the route of parasite transmission is not known. This paper investigates the horizontal transmission of T. contejeani between A. pallipes hosts as well as its transmissibility to the invasive signal crayfish (Pacifastacus leniusculus). Field collected juvenile A. pallipes and P. leniusculus were assigned to 1 of 3 experimental treatments; fed heavily infected A. pallipes tissue, exposed to water from tanks housing heavily parasitized A. pallipes, and a control group to provide an estimate of the baseline infection levels in the field. After 26 weeks, abdominal muscle samples were screened by PCR for T. contejeani. Infection was significantly higher in the treatment groups (83% in the cannibalism treatment, 42% in the water exposure treatment) than in the control group (4%), providing evidence for horizontal transmission of the parasite between A. pallipes hosts. Cannibalism and scavenging are common amongst crayfish, providing transmission opportunities in the field. The study also provides the first direct evidence for transmission of the parasite from an indigenous European crayfish species to the invasive signal crayfish, with 50% of P. leniusculus in each treatment, and 8% of control animals infected. We discuss the possibility that high density populations of the invasive signal crayfish may serve either as reservoirs or sinks for the parasite. PMID:22814084

  5. Prototype positron emission tomography insert with electro-optical signal transmission for simultaneous operation with MRI

    NASA Astrophysics Data System (ADS)

    Olcott, Peter; Kim, Ealgoo; Hong, Keyjo; Lee, Brian J.; Grant, Alexander M.; Chang, Chen-Ming; Glover, Gary; Levin, Craig S.

    2015-05-01

    The simultaneous acquisition of PET and MRI data shows promise to provide powerful capabilities to study disease processes in human subjects, guide the development of novel treatments, and monitor therapy response and disease progression. A brain-size PET detector ring insert for an MRI system is being developed that, if successful, can be inserted into any existing MRI system to enable simultaneous PET and MRI images of the brain to be acquired without mutual interference. The PET insert uses electro-optical coupling to relay all the signals from the PET detectors out of the MRI system using analog modulated lasers coupled to fiber optics. Because the fibers use light instead of electrical signals, the PET detector can be electrically decoupled from the MRI making it partially transmissive to the RF field of the MRI. The SiPM devices and low power lasers were powered using non-magnetic MRI compatible batteries. Also, the number of laser-fiber channels in the system was reduced using techniques adapted from the field of compressed sensing. Using the fact that incoming PET data is sparse in time and space, electronic circuits implementing constant weight codes uniquely encode the detector signals in order to reduce the number of electro-optical readout channels by 8-fold. Two out of a total of sixteen electro-optical detector modules have been built and tested with the entire RF-shielded detector gantry for the PET ring insert. The two detectors have been tested outside and inside of a 3T MRI system to study mutual interference effects and simultaneous performance with MRI. Preliminary results show that the PET insert is feasible for high resolution simultaneous PET/MRI imaging for applications in the brain.

  6. Prototype positron emission tomography insert with electro-optical signal transmission for simultaneous operation with MRI.

    PubMed

    Olcott, Peter; Kim, Ealgoo; Hong, Keyjo; Lee, Brian J; Grant, Alexander M; Chang, Chen-Ming; Glover, Gary; Levin, Craig S

    2015-05-01

    The simultaneous acquisition of PET and MRI data shows promise to provide powerful capabilities to study disease processes in human subjects, guide the development of novel treatments, and monitor therapy response and disease progression. A brain-size PET detector ring insert for an MRI system is being developed that, if successful, can be inserted into any existing MRI system to enable simultaneous PET and MRI images of the brain to be acquired without mutual interference. The PET insert uses electro-optical coupling to relay all the signals from the PET detectors out of the MRI system using analog modulated lasers coupled to fiber optics. Because the fibers use light instead of electrical signals, the PET detector can be electrically decoupled from the MRI making it partially transmissive to the RF field of the MRI. The SiPM devices and low power lasers were powered using non-magnetic MRI compatible batteries. Also, the number of laser-fiber channels in the system was reduced using techniques adapted from the field of compressed sensing. Using the fact that incoming PET data is sparse in time and space, electronic circuits implementing constant weight codes uniquely encode the detector signals in order to reduce the number of electro-optical readout channels by 8-fold. Two out of a total of sixteen electro-optical detector modules have been built and tested with the entire RF-shielded detector gantry for the PET ring insert. The two detectors have been tested outside and inside of a 3T MRI system to study mutual interference effects and simultaneous performance with MRI. Preliminary results show that the PET insert is feasible for high resolution simultaneous PET/MRI imaging for applications in the brain. PMID:25856511

  7. Tyrosine phosphorylation of RAS by ABL allosterically enhances effector binding

    PubMed Central

    Ting, Pamela Y.; Johnson, Christian W.; Fang, Cong; Cao, Xiaoqing; Graeber, Thomas G.; Mattos, Carla; Colicelli, John

    2015-01-01

    RAS proteins are signal transduction gatekeepers that mediate cell growth, survival, and differentiation through interactions with multiple effector proteins. The RAS effector RAS- and RAB-interacting protein 1 (RIN1) activates its own downstream effectors, the small GTPase RAB5 and the tyrosine kinase Abelson tyrosine-protein kinase (ABL), to modulate endocytosis and cytoskeleton remodeling. To identify ABL substrates downstream of RAS-to-RIN1 signaling, we examined human HEK293T cells overexpressing components of this pathway. Proteomic analysis revealed several novel phosphotyrosine peptides, including Harvey rat sarcoma oncogene (HRAS)-pTyr137. Here we report that ABL phosphorylates tyrosine 137 of H-, K-, and NRAS. Increased RIN1 levels enhanced HRAS-Tyr137 phosphorylation by nearly 5-fold, suggesting that RAS-stimulated RIN1 can drive ABL-mediated RAS modification in a feedback circuit. Tyr137 is well conserved among RAS orthologs and is part of a transprotein H-bond network. Crystal structures of HRASY137F and HRASY137E revealed conformation changes radiating from the mutated residue. Although consistent with Tyr137 participation in allosteric control of HRAS function, the mutations did not alter intrinsic GTP hydrolysis rates in vitro. HRAS-Tyr137 phosphorylation enhanced HRAS signaling capacity in cells, however, as reflected by a 4-fold increase in the association of phosphorylated HRASG12V with its effector protein RAF proto-oncogene serine/threonine protein kinase 1 (RAF1). These data suggest that RAS phosphorylation at Tyr137 allosterically alters protein conformation and effector binding, providing a mechanism for effector-initiated modulation of RAS signaling.—Ting, P. Y., Johnson, C. W., Fang, C., Cao, X., Graeber, T. G., Mattos, C., Colicelli, J. Tyrosine phosphorylation of RAS by ABL allosterically enhances effector binding. PMID:25999467

  8. Self-powered wireless carbohydrate/oxygen sensitive biodevice based on radio signal transmission.

    PubMed

    Falk, Magnus; Alcalde, Miguel; Bartlett, Philip N; De Lacey, Antonio L; Gorton, Lo; Gutierrez-Sanchez, Cristina; Haddad, Raoudha; Kilburn, Jeremy; Leech, Dónal; Ludwig, Roland; Magner, Edmond; Mate, Diana M; Conghaile, Peter Ó; Ortiz, Roberto; Pita, Marcos; Pöller, Sascha; Ruzgas, Tautgirdas; Salaj-Kosla, Urszula; Schuhmann, Wolfgang; Sebelius, Fredrik; Shao, Minling; Stoica, Leonard; Sygmund, Cristoph; Tilly, Jonas; Toscano, Miguel D; Vivekananthan, Jeevanthi; Wright, Emma; Shleev, Sergey

    2014-01-01

    Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply. PMID:25310190

  9. Self-Powered Wireless Carbohydrate/Oxygen Sensitive Biodevice Based on Radio Signal Transmission

    PubMed Central

    Falk, Magnus; Alcalde, Miguel; Bartlett, Philip N.; De Lacey, Antonio L.; Gorton, Lo; Gutierrez-Sanchez, Cristina; Haddad, Raoudha; Kilburn, Jeremy; Leech, Dónal; Ludwig, Roland; Magner, Edmond; Mate, Diana M.; Conghaile, Peter Ó.; Ortiz, Roberto; Pita, Marcos; Pöller, Sascha; Ruzgas, Tautgirdas; Salaj-Kosla, Urszula; Schuhmann, Wolfgang; Sebelius, Fredrik; Shao, Minling; Stoica, Leonard; Sygmund, Cristoph; Tilly, Jonas; Toscano, Miguel D.; Vivekananthan, Jeevanthi; Wright, Emma; Shleev, Sergey

    2014-01-01

    Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply. PMID:25310190

  10. Supramolecular Allosteric Cofacial Porphyrin Complexes

    SciTech Connect

    Oliveri, Christopher G.; Gianneschi, Nathan C.; Nguyen, Son Binh T.; Mirkin, Chad A.; Stern, Charlotte L.; Wawrzak, Zdzislaw; Pink, Maren

    2008-04-12

    Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioether-phosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (Rh{sup I} or Cu{sup I} sites) and two cofacially aligned porphyrins (Zn{sup II} sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, 'condensed' or 'open'. Combining the ether-phosphine ligand with the appropriate Rh{sup I} or Cu{sup I} transition-metal precursors results in 'open' macrocyclic products. In contrast, reacting the thioether-phosphine ligand with RhI or CuI precursors yields condensed structures that can be converted into their 'open' macrocyclic forms via introduction of additional ancillary ligands. The change in cavity size that occurs allows these structures to function as allosteric catalysts for the acyl transfer reaction between X-pyridylcarbinol (where X = 2, 3, or 4) and 1-acetylimidazole. For 3- and 4-pyridylcarbinol, the 'open' macrocycle accelerates the acyl transfer reaction more than the condensed analogue and significantly more than the porphyrin monomer. In contrast, an allosteric effect was not observed for 2-pyridylcarbinol, which is expected to be a weaker binder and is unfavorably constrained inside the macrocyclic cavity.

  11. Allosteric transition and binding of small molecule effectors causes curvature change in central β-sheets of selected enzymes

    PubMed Central

    Tolonen, Ellen; Bueno, Brenda; Kulshreshta, Sanjeev; Cieplak, Piotr; Argáez, Miguel; Velázquez, Leticia

    2014-01-01

    A quantitative description of allosteric transition remains a significant science challenge. Many allosteric enzymes contain a central β-sheet in their catalytic domain. When an allosteric protein undergoes the transition between T (tense) and R (relaxed) allosteric states, this central β-sheet undergoes a conformational change. A traditional method of measuring this change, the root mean square deviation (RMSD), appears to be inadequate to describe such changes in meaningful quantitative manner. We designed a novel quantitative method to demonstrate this conformational transition by measuring the change in curvature of the central β-sheet when enzymes transition between allosteric states. The curvature was established by calculating the semiaxes of a 3-D hyperboloid fitted by least squares to the Cα atomic positions of the β-sheet. The two enzymes selected for this study, fructose 1,6-bisphosphatase (FBPase) from pig kidney and aspartate carbamoyltransferase (ATCase) from E. coli, showed while transitioning between the allosteric states (T ⇔ R) a notable change in β-sheet curvature (∼5%) that results in a large lateral shift at the sheet's edge, which is necessary to convey the signal. The results suggest that the β-sheet participates in storing elastic energy associated with the transition. Establishing a tentative link between the energetics of the β-sheet in different allosteric states provides a more objective basis for the naming convention of allosteric states (tense or relaxed), and provides insight into the hysteretic nature of the transition. The approach presented here allows for a better understanding of the internal dynamics of allosteric enzymes by defining the domains that directly participate in the transition. PMID:20602244

  12. Allosteric transition and binding of small molecule effectors causes curvature change in central β-sheets of selected enzymes.

    PubMed

    Tolonen, Ellen; Bueno, Brenda; Kulshreshta, Sanjeev; Cieplak, Piotr; Argáez, Miguel; Velázquez, Leticia; Stec, Boguslaw

    2011-04-01

    A quantitative description of allosteric transition remains a significant science challenge. Many allosteric enzymes contain a central β-sheet in their catalytic domain. When an allosteric protein undergoes the transition between T (tense) and R (relaxed) allosteric states, this central β-sheet undergoes a conformational change. A traditional method of measuring this change, the root mean square deviation (RMSD), appears to be inadequate to describe such changes in meaningful quantitative manner. We designed a novel quantitative method to demonstrate this conformational transition by measuring the change in curvature of the central β-sheet when enzymes transition between allosteric states. The curvature was established by calculating the semiaxes of a 3-D hyperboloid fitted by least squares to the Cα atomic positions of the β-sheet. The two enzymes selected for this study, fructose 1,6-bisphosphatase (FBPase) from pig kidney and aspartate carbamoyltransferase (ATCase) from E. coli, showed while transitioning between the allosteric states (T ⇔ R) a notable change in β-sheet curvature (∼5%) that results in a large lateral shift at the sheet's edge, which is necessary to convey the signal. The results suggest that the β-sheet participates in storing elastic energy associated with the transition. Establishing a tentative link between the energetics of the β-sheet in different allosteric states provides a more objective basis for the naming convention of allosteric states (tense or relaxed), and provides insight into the hysteretic nature of the transition. The approach presented here allows for a better understanding of the internal dynamics of allosteric enzymes by defining the domains that directly participate in the transition. PMID:20602244

  13. Hydrogen peroxide produced inside mitochondria takes part in cell-to-cell transmission of apoptotic signal.

    PubMed

    Pletjushkina, O Yu; Fetisova, E K; Lyamzaev, K G; Ivanova, O Yu; Domnina, L V; Vyssokikh, M Yu; Pustovidko, A V; Alexeevski, A V; Alexeevski, D A; Vasiliev, J M; Murphy, M P; Chernyak, B V; Skulachev, V P

    2006-01-01

    In monolayer of HeLa cells treated with tumor necrosis factor (TNF), apoptotic cells formed clusters indicating possible transmission of apoptotic signal via the culture media. To investigate this phenomenon, a simple method of enabling two cell cultures to interact has been employed. Two coverslips were placed side by side in a Petri dish, one coverslip covered with apoptogen-treated cells (the inducer) and another with non-treated cells (the recipient). TNF, staurosporine, or H2O2 treatment of the inducer cells is shown to initiate apoptosis on the recipient coverslip. This effect is increased by a catalase inhibitor aminotriazole and is arrested by addition of catalase or by pre-treatment of either the inducer or the recipient cells with nanomolar concentrations of mitochondria-targeted cationic antioxidant MitoQ (10-(6 -ubiquinolyl)decyltriphenylphosphonium), which specifically arrests H2O2-induced apoptosis. The action of MitoQ is abolished by an uncoupler preventing accumulation of MitoQ in mitochondria. It is concluded that reactive oxygen species (ROS) produced by mitochondria in the apoptotic cells initiate the release of H2O2 from these cells. The H2O2 released is employed as a long-distance cell suicide messenger. In processing of such a signal by the recipient cells, mitochondrial ROS production is also involved. It is suggested that the described phenomenon may be involved in expansion of the apoptotic region around a damaged part of the tissue during heart attack or stroke as well as in "organoptosis", i.e. disappearance of organs during ontogenesis. PMID:16457620

  14. The importance of female choice, male-male competition, and signal transmission as causes of selection on male mating signals.

    PubMed

    Sullivan-Beckers, Laura; Cocroft, Reginald B

    2010-11-01

    Selection on advertisement signals arises from interacting sources including female choice, male-male competition, and the communication channel (i.e., the signaling environment). To identify the contribution of individual sources of selection, we used previously quantified relationships between signal traits and each putative source to predict relationships between signal variation and fitness in Enchenopa binotata treehoppers (Hemiptera: Membracidae). We then measured phenotypic selection on signals and compared predicted and realized relationships between signal traits and mating success. We recorded male signals, then measured lifetime mating success at two population densities in a realistic environment in which sources of selection could interact. We identified which sources best predicted the relationship between signal variation and mating success using a multiple regression approach. All signal traits were under selection in at least one of the two breeding seasons measured, and in some cases selection was variable between years. Female preference was the strongest source of selection shaping male signals. The E. binotata species complex is a model of ecological speciation initiated by host shifts. Signal and preference divergence contribute to behavioral isolation within the complex, and the finding that female mate preferences drive signal evolution suggests that speciation in this group results from both ecological divergence and sexual selection. PMID:20624180

  15. 37 CFR 258.4 - Royalty fee for secondary transmission of digital signals of broadcast stations by satellite...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2010-07-01 2010-07-01 false Royalty fee for secondary transmission of digital signals of broadcast stations by satellite carriers. 258.4 Section 258.4 Patents, Trademarks, and Copyrights COPYRIGHT OFFICE, LIBRARY OF CONGRESS COPYRIGHT ARBITRATION ROYALTY PANEL RULES AND PROCEDURES ADJUSTMENT OF ROYALTY...

  16. Maternal transmission of a rare GABRB3 signal peptide variant is associated with autism

    PubMed Central

    Delahanty, Ryan J.; Kang, Jingqiong; Brune, Camille W.; Kistner, Emily O.; Courchesne, Eric; Cox, Nancy J.; Cook, Edwin H.; Macdonald, Robert L.; Sutcliffe, James S.

    2009-01-01

    Maternal 15q11-q13 duplication is the most common copy number variant in autism, accounting for ∼1-3% of cases. The 15q11-q13 region is subject to epigenetic regulation and genomic copy number losses and gains cause genomic disorders in a parent-of-origin-specific manner. One 15q11-q13 locus encodes the GABAA receptor β3 subunit gene (GABRB3), which has been implicated by several studies in both autism and absence epilepsy, and the co-morbidity of epilepsy in autism is well established. We report that maternal transmission of a GABRB3 signal peptide variant (P11S), previously implicated in childhood absence epilepsy, is associated with autism. Analysis of wild-type and mutant β3 subunit-containing α1β3γ2 GABAA receptors demonstrates reduced whole cell current and decreased β3 subunit protein on the cell surface due to impaired intracellular β3 subunit processing. We thus provide the first evidence for association between a specific GABAA receptor defect and autism, direct evidence that this defect causes synaptic dysfunction that is autism-relevant, and the first maternal risk effect in the 15q11-q13 autism duplication region linked to a coding variant. PMID:19935738

  17. Regulation of ROS in transmissible gastroenteritis virus-activated apoptotic signaling

    SciTech Connect

    Ding, Li; Zhao, Xiaomin; Huang, Yong; Du, Qian; Dong, Feng; Zhang, Hongling; Song, Xiangjun; Zhang, Wenlong; Tong, Dewen

    2013-12-06

    Highlights: •TGEV infection induced ROS accumulation. •ROS accumulation is involved in TGEV-induced mitochondrial integrity impairment. •ROS is associated with p53 activation and apoptosis occurrence in TGEV-infected cells. -- Abstract: Transmissible gastroenteritis virus (TGEV), an enteropathogenic coronavirus, causes severe lethal watery diarrhea and dehydration in piglets. Previous studies indicate that TGEV infection induces cell apoptosis in host cells. In this study, we investigated the roles and regulation of reactive oxygen species (ROS) in TGEV-activated apoptotic signaling. The results showed that TGEV infection induced ROS accumulation, whereas UV-irradiated TGEV did not promote ROS accumulation. In addition, TGEV infection lowered mitochondrial transmembrane potential in PK-15 cell line, which could be inhibited by ROS scavengers, pyrrolidinedithiocarbamic (PDTC) and N-acetyl-L-cysteine (NAC). Furthermore, the two scavengers significantly inhibited the activation of p38 MAPK and p53 and further blocked apoptosis occurrence through suppressing the TGEV-induced Bcl-2 reduction, Bax redistribution, cytochrome c release and caspase-3 activation. These results suggest that oxidative stress pathway might be a key element in TGEV-induced apoptosis and TGEV pathogenesis.

  18. Positive cooperativity of acetylcholine and other agonists with allosteric ligands on muscarinic acetylcholine receptors.

    PubMed

    Jakubík, J; Bacáková, L; El-Fakahany, E E; Tucek, S

    1997-07-01

    affinity, respectively) and between brucine and pentylthio-TZTP on the M2 and brucine and carbachol on the M1 receptors (8-fold increases in affinity). The discovery that it is possible to increase the affinity of muscarinic receptors for their agonists by allosteric modulators offers a new way to subtype-specific pharmacological enhancement of transmission at cholinergic (muscarinic) synapses. PMID:9224827

  19. Opportunities and challenges in the discovery of allosteric modulators of GPCRs for treating CNS disorders

    PubMed Central

    Conn, P. Jeffrey; Lindsley, Craig W.; Meiler, Jens; Niswender, Colleen M.

    2014-01-01

    Novel allosteric modulators of G protein-coupled receptors (GPCRs) are providing fundamental advances in the development of GPCR ligands with high subtype selectivity and novel modes of efficacy that have not been possible with traditional approaches. As new allosteric modulators are advancing as drug candidates, we are developing an increased understanding of the major advantages and broad range of activities that can be achieved with these agents through selective modulation of specific signalling pathways, differential effects on GPCR homodimers versus heterodimers, and other properties. This understanding creates exciting opportunities, as well as unique challenges, in the optimization of novel therapeutic agents for disorders of the central nervous system. PMID:25176435

  20. The allosteric vestibule of a seven transmembrane helical receptor controls G-protein coupling

    PubMed Central

    Bock, Andreas; Merten, Nicole; Schrage, Ramona; Dallanoce, Clelia; Bätz, Julia; Klöckner, Jessica; Schmitz, Jens; Matera, Carlo; Simon, Katharina; Kebig, Anna; Peters, Lucas; Müller, Anke; Schrobang-Ley, Jasmin; Tränkle, Christian; Hoffmann, Carsten; De Amici, Marco; Holzgrabe, Ulrike; Kostenis, Evi; Mohr, Klaus

    2012-01-01

    Seven transmembrane helical receptors (7TMRs) modulate cell function via different types of G proteins, often in a ligand-specific manner. Class A 7TMRs harbour allosteric vestibules in the entrance of their ligand-binding cavities, which are in the focus of current drug discovery. However, their biological function remains enigmatic. Here we present a new strategy for probing and manipulating conformational transitions in the allosteric vestibule of label-free 7TMRs using the M2 acetylcholine receptor as a paradigm. We designed dualsteric agonists as 'tailor-made' chemical probes to trigger graded receptor activation from the acetylcholine-binding site while simultaneously restricting spatial flexibility of the receptor's allosteric vestibule. Our findings reveal for the first time that a 7TMR's allosteric vestibule controls the extent of receptor movement to govern a hierarchical order of G-protein coupling. This is a new concept assigning a biological role to the allosteric vestibule for controlling fidelity of 7TMR signalling. PMID:22948826

  1. Proposed Mode of Binding and Action of Positive Allosteric Modulators at Opioid Receptors.

    PubMed

    Shang, Yi; Yeatman, Holly R; Provasi, Davide; Alt, Andrew; Christopoulos, Arthur; Canals, Meritxell; Filizola, Marta

    2016-05-20

    Available crystal structures of opioid receptors provide a high-resolution picture of ligand binding at the primary ("orthosteric") site, that is, the site targeted by endogenous ligands. Recently, positive allosteric modulators of opioid receptors have also been discovered, but their modes of binding and action remain unknown. Here, we use a metadynamics-based strategy to efficiently sample the binding process of a recently discovered positive allosteric modulator of the δ-opioid receptor, BMS-986187, in the presence of the orthosteric agonist SNC-80, and with the receptor embedded in an explicit lipid-water environment. The dynamics of BMS-986187 were enhanced by biasing the potential acting on the ligand-receptor distance and ligand-receptor interaction contacts. Representative lowest-energy structures from the reconstructed free-energy landscape revealed two alternative ligand binding poses at an allosteric site delineated by transmembrane (TM) helices TM1, TM2, and TM7, with some participation of TM6. Mutations of amino acid residues at these proposed allosteric sites were found to either affect the binding of BMS-986187 or its ability to modulate the affinity and/or efficacy of SNC-80. Taken together, these combined experimental and computational studies provide the first atomic-level insight into the modulation of opioid receptor binding and signaling by allosteric modulators. PMID:26841170

  2. The Concept of Allosteric Interaction and Its Consequences for the Chemistry of the Brain

    PubMed Central

    Changeux, Jean-Pierre

    2013-01-01

    Throughout this Reflections article, I have tried to follow up on the genesis in the 1960s and subsequent evolution of the concept of allosteric interaction and to examine its consequences within the past decades, essentially in the field of the neuroscience. The main conclusion is that allosteric mechanisms built on similar structural principles operate in bacterial regulatory enzymes, gene repressors (and the related nuclear receptors), rhodopsin, G-protein-coupled receptors, neurotransmitter receptors, ion channels, and so on from prokaryotes up to the human brain yet with important features of their own. Thus, future research on these basic cybernetic sensors is expected to develop in two major directions: at the elementary level, toward the atomic structure and molecular dynamics of the conformational changes involved in signal recognition and transduction, but also at a higher level of organization, the contribution of allosteric mechanisms to the modulation of brain functions. PMID:23878193

  3. Modelling the transmission of a 40-Gbit s{sup -1} NRZ-ADPSK signal in 50-GHz networks

    SciTech Connect

    Gurkin, N V; Kapin, Yu A; Nanii, Oleg E; Novikov, A G; Pavlov, V N; Plaksin, S O; Plotskii, A Yu; Treshchikov, V N

    2013-06-30

    We study numerically the effect of linear and nonlinear distortions on the transmission of a 40-Gbit s{sup -1} NRZ-ADPSK signal. The results of the numerical simulation coincide within the measurement accuracy with the experimental data, which indicates the adequacy of the mathematical model of the communication line, transmitter and receiver. We have found experimentally and numerically that in communication systems based on a standard telecommunication fibre negative dispersion (approximately -160 ps nm{sup -1}) introduced into the signal being transmitted provides an increase in the maximum admissible signal power coupled into a span and in the value of the admissible attenuation of the spans at 2 dB. It is established that nonlinear distortions caused by the presence of adjacent channels in a frequency network with a step of 50 and 100 GHz (crosstalks) are insignificant in comparison with the interchannel nonlinear distortions. (optical information transmission)

  4. Parameter design of signal processing for transmission/reflection-type hybrid extrinsic Fabry Perot interferometric optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Lee, Jung-Ju

    2005-02-01

    A transmission/reflection-type hybrid extrinsic Fabry-Perot interferometric (TRHEFPI) optical fiber sensor presents transmission-type and reflection-type sensor signals simultaneously, and measurement directions can be robustly distinguished with the phase lead or lag of the linear combination signal from the original sensor signal. This sensor principle compensates for the ambiguous distinction of the measurement directions and direction changes of conventional interferometric optical fiber sensors, including extrinsic Fabry-Perot interferometric optical fiber sensors, due to the exclusive use of fringe counting in signal processing. Designing a sensor coefficient in the linear combination signal is one of the most important works in signal processing for the TRHEFPI optical fiber sensor because the magnitude of the phase shifts depends on the sensor coefficient. A design method of the sensor coefficient is presented in this research. The method was verified with experimental sensor signals and applied to strain measurement experiments. A method of absolute measurement using the TRHEFPI optical fiber sensor is also presented.

  5. Biased Agonism and Biased Allosteric Modulation at the CB1 Cannabinoid Receptor.

    PubMed

    Khajehali, Elham; Malone, Daniel T; Glass, Michelle; Sexton, Patrick M; Christopoulos, Arthur; Leach, Katie

    2015-08-01

    CB1 cannabinoid receptors (CB1Rs) are attractive therapeutic targets for numerous central nervous system disorders. However, clinical application of cannabinoid ligands has been hampered owing to their adverse on-target effects. Ligand-biased signaling from, and allosteric modulation of, CB1Rs offer pharmacological approaches that may enable the development of improved CB1R drugs, through modulation of only therapeutically desirable CB1R signaling pathways. There is growing evidence that CB1Rs are subject to ligand-biased signaling and allosterism. Therefore, in the present study, we quantified ligand-biased signaling and allosteric modulation at CB1Rs. Cannabinoid agonists displayed distinct biased signaling profiles at CB1Rs. For instance, whereas 2-arachidonylglycerol and WIN55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-napthalenylmethanone] showed little preference for inhibition of cAMP and phosphorylation of extracellular signal-regulated kinase 1/2 (pERK1/2), N-arachidonoylethanolamine (anandamide), methanandamide, CP55940 [2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]-5-(2-methyloctan-2-yl)phenol], and HU-210 [11-hydroxy-Δ(8)-THC-dimethylheptyl] were biased toward cAMP inhibition. The small-molecule allosteric modulator Org27569 [5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)ethyl]amide] displayed biased allosteric effects by blocking cAMP inhibition mediated by all cannabinoid ligands tested, at the same time having little or no effect on ERK1/2 phosphorylation mediated by a subset of these ligands. Org27569 also displayed negative binding cooperativity with [(3)H]SR141716A [5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide]; however, it had minimal effects on binding of cannabinoid agonists. Furthermore, we highlight the need to validate the reported allosteric effects of the endogenous ligands lipoxin A4 and

  6. Structure-Based Ligand Discovery Targeting Orthosteric and Allosteric Pockets of Dopamine Receptors

    PubMed Central

    Lane, J. Robert; Chubukov, Pavel; Liu, Wei; Canals, Meritxell; Cherezov, Vadim; Abagyan, Ruben; Stevens, Raymond C.

    2013-01-01

    Small molecules targeting allosteric pockets of G protein–coupled receptors (GPCRs) have a great therapeutic potential for the treatment of neurologic and other chronic disorders. Here we performed virtual screening for orthosteric and putative allosteric ligands of the human dopamine D3 receptor (D3R) using two optimized crystal-structure–based models: the receptor with an empty binding pocket (D3RAPO), and the receptor complex with dopamine (D3RDopa). Subsequent biochemical and functional characterization revealed 14 novel ligands with a binding affinity of better than 10 μM in the D3RAPO candidate list (56% hit rate), and 8 novel ligands in the D3RDopa list (32% hit rate). Most ligands in the D3RAPO model span both orthosteric and extended pockets and behave as antagonists at D3R, with compound 7 showing the highest potency of dopamine inhibition (IC50 = 7 nM). In contrast, compounds identified by the D3RDopa model are predicted to occupy an allosteric site at the extracellular extension of the pocket, and they all lack the anchoring amino group. Compounds targeting the allosteric site display a variety of functional activity profiles, where behavior of at least two compounds (23 and 26) is consistent with noncompetitive allosteric modulation of dopamine signaling in the extracellular signal-regulated kinase 1 and 2 phosphorylation and β-arrestin recruitment assays. The high affinity and ligand efficiency of the chemically diverse hits identified in this study suggest utility of structure-based screening targeting allosteric sites of GPCRs. PMID:24021214

  7. Retrograde Endocannabinoid Signaling Reduces GABAergic Synaptic Transmission to Gonadotropin-Releasing Hormone Neurons

    PubMed Central

    Farkas, Imre; Kalló, Imre; Deli, Levente; Vida, Barbara; Hrabovszky, Erik; Fekete, Csaba; Moenter, Suzanne M.; Watanabe, Masahiko; Liposits, Zsolt

    2010-01-01

    Cannabinoids suppress fertility via reducing hypothalamic GnRH output. γ-Aminobutyric acid (GABA)A receptor (GABAA-R)-mediated transmission is a major input to GnRH cells that can be excitatory. We hypothesized that cannabinoids act via inhibiting GABAergic input. We performed loose-patch electrophysiological studies of acute slices from adult male GnRH-green fluorescent protein transgenic mice. Bath application of type 1 cannabinoid receptor (CB1) agonist WIN55,212 decreased GnRH neuron firing rate. This action was detectable in presence of the glutamate receptor antagonist kynurenic acid but disappeared when bicuculline was also present, indicating GABAA-R involvement. In immunocytochemical experiments, CB1-immunoreactive axons formed contacts with GnRH neurons and a subset established symmetric synapses characteristic of GABAergic neurotransmission. Functional studies were continued with whole-cell patch-clamp electrophysiology in presence of tetrodotoxin. WIN55,212 decreased the frequency of GABAA-R-mediated miniature postsynaptic currents (mPSCs) (reflecting spontaneous vesicle fusion), which was prevented with the CB1 antagonist AM251, indicating collectively that activation of presynaptic CB1 inhibits GABA release. AM251 alone increased mPSC frequency, providing evidence that endocannabinoids tonically inhibit GABAA-R drive onto GnRH neurons. Increased mPSC frequency was absent when diacylglycerol lipase was blocked intracellularly with tetrahydrolipstatin, showing that tonic inhibition is caused by 2-arachidonoylglycerol production of GnRH neurons. CdCl2 in extracellular solution can maintain both action potentials and spontaneous vesicle fusion. Under these conditions, when endocannabinoid-mediated blockade of spontaneous vesicle fusion was blocked with AM251, GnRH neuron firing increased, revealing an endogenous endocannabinoid brake on GnRH neuron firing. Retrograde endocannabinoid signaling may represent an important mechanism under physiological and

  8. Demonstration of 2.97-Gb/s video signal transmissions in DML-based IM-DDO-OFDM systems

    NASA Astrophysics Data System (ADS)

    Chen, Ming; He, Jing; Deng, Rui; Chen, Qinghui; Zhang, Jinlong; Chen, Lin

    2016-05-01

    To further investigate the feasibility of the digital signal processing (DSP) algorithms (e.g., symbol timing synchronization, channel estimation and equalization, and sampling clock frequency offset (SCFO) estimation and compensation) for real-time optical orthogonal frequency-division multiplexing (OFDM) system, 2.97-Gb/s real-time high-definition video signal parallel transmission is experimentally demonstrated in OFDM-based short-reach intensity-modulated direct-detection (IM-DD) systems. The experimental results show that, in the presence of ∼12 ppm SCFO between transmitter and receiver, the adaptively modulated OFDM signal transmission over 20 km standard single-mode fiber with an error bit rate less than 1 × 10-9 can be achieved by using only DSP-based small SCFO estimation and compensation method without utilizing forward error correction technique. To the best of our knowledge, for the first time, we successfully demonstrate that the video signal at a bit rate in excess of 1-Gb/s transmission in a simple real-valued inverse fast Fourier transform and fast Fourier transform based IM-DD optical OFDM system employing a directly modulated laser.

  9. Neural signal sensing, transmission and functional regeneration on different toads' bodies.

    PubMed

    Shen, Xiaoyan; Wang, Zhigong; Lü, Xiaoying; Jiang, Zhenglin; Li, Wenyuan; Zhao, Xintai; Huang, Zonghao

    2009-01-01

    The presence of neural signals is the most important feature of animals' life. Monitoring, analysis and regeneration of neural signals are important for the rehabilitation of paralyzed patients. In this paper, the neural signal regeneration between the proximal and the distal end of an injured nerve is introduced. In the experiment a microelectronic module is used as a channel bridge. The regeneration of nerve signals is realized from one toad's sciatic nerve to another's. Corresponding neural signals and EMG were recorded and analyzed. It will be a reference to further study on the neural signals and the relationship between a neural signal and the muscle locomotion. PMID:19965066

  10. Functional Consequences of GPCR Heterodimerization: GPCRs as Allosteric Modulators

    PubMed Central

    Haack, Karla K.V.; McCarty, Nael A.

    2011-01-01

    G Protein Coupled Receptors (GPCRs) represent the largest family of membrane proteins in the human genome, are the targets of approximately 25% of all marketed pharmaceuticals, and the focus of intensive research worldwide given that this superfamily of receptors is as varied in function as it is ubiquitously expressed among all cell types. Increasing evidence has shown that the classical two part model of GPCR signaling (one GPCR, one type of heterotrimeric G protein) is grossly oversimplified as many GPCRs can couple to more than one type of G protein, each subunit of the heterotrimeric G protein can activate different downstream effectors, and, surprisingly, other GPCRs can affect receptor behavior in G protein-independent ways. The concept of GPCR heterodimerization, or the physical association of two different types of GPCRs, presents an unexpected mechanism for GPCR regulation and function, and provides a novel target for pharmaceuticals. Here we present a synopsis of the functional consequences of GPCR heterodimerization in both in vitro and in vivo studies, focusing on the concept of GPCRs as allosteric modulators. Typically, an allosteric modulator is a ligand or molecule that alters a receptor's innate functional properties, but here we propose that in the case of GPCR heterodimers, it is the physical coupling of two receptors that leads to changes in cognate receptor signaling.

  11. Kappa-opioid receptor signaling in the striatum as a potential modulator of dopamine transmission in cocaine dependence.

    PubMed

    Trifilieff, Pierre; Martinez, Diana

    2013-01-01

    Cocaine addiction is accompanied by a decrease in striatal dopamine signaling, measured as a decrease in dopamine D2 receptor binding as well as blunted dopamine release in the striatum. These alterations in dopamine transmission have clinical relevance, and have been shown to correlate with cocaine-seeking behavior and response to treatment for cocaine dependence. However, the mechanisms contributing to the hypodopaminergic state in cocaine addiction remain unknown. Here we review the positron emission tomography (PET) imaging studies showing alterations in D2 receptor binding potential and dopamine transmission in cocaine abusers and their significance in cocaine-seeking behavior. Based on animal and human studies, we propose that the kappa receptor/dynorphin system, because of its impact on dopamine transmission and upregulation following cocaine exposure, could contribute to the hypodopaminergic state reported in cocaine addiction, and could thus be a relevant target for treatment development. PMID:23760592

  12. Roles of cell signaling pathways in cell-to-cell contact-mediated Epstein-Barr virus transmission.

    PubMed

    Nanbo, Asuka; Terada, Haruna; Kachi, Kunihiro; Takada, Kenzo; Matsuda, Tadashi

    2012-09-01

    Epstein-Barr virus (EBV), a human gamma herpesvirus, establishes a life-long latent infection in B lymphocytes and epithelial cells following primary infection. Several lines of evidence indicate that the efficiency of EBV infection in epithelial cells is accelerated up to 10(4)-fold by coculturing with EBV-infected Burkitt's lymphoma (BL) cells compared to infection with cell-free virions, indicating that EBV infection into epithelial cells is mainly mediated via cell-to-cell contact. However, the molecular mechanisms involved in this pathway are poorly understood. Here, we establish a novel assay to assess cell-to-cell contact-mediated EBV transmission by coculturing an EBV-infected BL cell line with an EBV-negative epithelial cell line under stimulation for lytic cycle induction. By using this assay, we confirmed that EBV was transmitted from BL cells to epithelial cells via cell-to-cell contact but not via cell-to-cell fusion. The inhibitor treatments of extracellular signal-regulated kinase (ERK) and nuclear factor (NF)-κB pathways blocked EBV transmission in addition to lytic induction. The blockage of the phosphoinositide 3-kinase (PI3K) pathway impaired EBV transmission coupled with the inhibition of lytic induction. Knockdown of the RelA/p65 subunit of NF-κB reduced viral transmission. Moreover, these signaling pathways were activated in cocultured BL cells and in epithelial cells. Finally, we observed that viral replication was induced in cocultured BL cells. Taken together, our data suggest that cell-to-cell contact induces multiple cell signaling pathways in BL cells and epithelial cells, contributing to the induction of the viral lytic cycle in BL cells and the enhancement of viral transmission to epithelial cells. PMID:22718812

  13. Demostration of 520 Gb/s/λ pre-equalized DFT-spread PDM-16QAM-OFDM signal transmission.

    PubMed

    Li, Fan; Yu, Jianjun; Cao, Zizheng; Chen, Ming; Zhang, Junwen; Li, Xinying

    2016-02-01

    In this paper, we successfully transmit 8 × 520 Gb/s pre-equalized DFT-spread PDM-16QAM orthogonal frequency-division multiplexing (OFDM) signal over 840 km SMF with BER under 2.4 × 10(-2). We discuss how to obtain accurate tranceivers' response during pre-equalization for DFT-spread OFDM with coherent detection and we find conventional OFDM symbols training sequences (TSs) outperform DFT-spread OFDM symbols TSs in obtaining channel response for pre-equalization and equalization. Additionally, the optimal IFFT/FFT size is explored for the pre-equalized DFT-spread PDM-16QAM-OFDM transmission systems. It is the first time to realize 400 Gb/s/λ net rate OFDM signal transmission. PMID:26906836

  14. Transmission of three-polarization-multiplexed 25-Gb/s DPSK signals over 300-km fiber link.

    PubMed

    Pan, Yan; Yan, Lianshan; Yi, Anlin; Chen, Zhiyu; Jiang, Lin; Pan, Wei; Luo, Bin; Zou, Xihua; Zhou, Xinyu; Feng, Xia

    2016-04-01

    Polarization is one of the key parameters to be utilized for large capacity and high spectral-efficient optical communication systems, especially the widely deployed polarization-division-multiplexing (PDM) scheme. To break the limitation of only two orthogonal polarization states that could be used for carrying data signals over the same wavelength, we experimentally demonstrate the first transmission of three-polarization-division-multiplexed DPSK signals at a rate up to 3×25  Gb/s over 300-km fiber link by using a single-carrier. PMID:27192302

  15. Designing Allosteric Control into Enzymes by Chemical Rescue of Structure

    SciTech Connect

    Deckert, Katelyn; Budiardjo, S. Jimmy; Brunner, Luke C.; Lovell, Scott; Karanicolas, John

    2012-08-07

    Ligand-dependent activity has been engineered into enzymes for purposes ranging from controlling cell morphology to reprogramming cellular signaling pathways. Where these successes have typically fused a naturally allosteric domain to the enzyme of interest, here we instead demonstrate an approach for designing a de novo allosteric effector site directly into the catalytic domain of an enzyme. This approach is distinct from traditional chemical rescue of enzymes in that it relies on disruption and restoration of structure, rather than active site chemistry, as a means to achieve modulate function. We present two examples, W33G in a {beta}-glycosidase enzyme ({beta}-gly) and W492G in a {beta}-glucuronidase enzyme ({beta}-gluc), in which we engineer indole-dependent activity into enzymes by removing a buried tryptophan side chain that serves as a buttress for the active site architecture. In both cases, we observe a loss of function, and in both cases we find that the subsequent addition of indole can be used to restore activity. Through a detailed analysis of {beta}-gly W33G kinetics, we demonstrate that this rescued enzyme is fully functionally equivalent to the corresponding wild-type enzyme. We then present the apo and indole-bound crystal structures of {beta}-gly W33G, which together establish the structural basis for enzyme inactivation and rescue. Finally, we use this designed switch to modulate {beta}-glycosidase activity in living cells using indole. Disruption and recovery of protein structure may represent a general technique for introducing allosteric control into enzymes, and thus may serve as a starting point for building a variety of bioswitches and sensors.

  16. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids

    PubMed Central

    Reichau, Sebastian; Blackmore, Nicola J.; Jiao, Wanting; Parker, Emily J.

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal. PMID:27128682

  17. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids.

    PubMed

    Reichau, Sebastian; Blackmore, Nicola J; Jiao, Wanting; Parker, Emily J

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal. PMID:27128682

  18. Bithionol Potently Inhibits Human Soluble Adenylyl Cyclase through Binding to the Allosteric Activator Site.

    PubMed

    Kleinboelting, Silke; Ramos-Espiritu, Lavoisier; Buck, Hannes; Colis, Laureen; van den Heuvel, Joop; Glickman, J Fraser; Levin, Lonny R; Buck, Jochen; Steegborn, Clemens

    2016-04-29

    The signaling molecule cAMP regulates functions ranging from bacterial transcription to mammalian memory. In mammals, cAMP is synthesized by nine transmembrane adenylyl cyclases (ACs) and one soluble AC (sAC). Despite similarities in their catalytic domains, these ACs differ in regulation. Transmembrane ACs respond to G proteins, whereas sAC is uniquely activated by bicarbonate. Via bicarbonate regulation, sAC acts as a physiological sensor for pH/bicarbonate/CO2, and it has been implicated as a therapeutic target, e.g. for diabetes, glaucoma, and a male contraceptive. Here we identify the bisphenols bithionol and hexachlorophene as potent, sAC-specific inhibitors. Inhibition appears mostly non-competitive with the substrate ATP, indicating that they act via an allosteric site. To analyze the interaction details, we solved a crystal structure of an sAC·bithionol complex. The structure reveals that the compounds are selective for sAC because they bind to the sAC-specific, allosteric binding site for the physiological activator bicarbonate. Structural comparison of the bithionol complex with apo-sAC and other sAC·ligand complexes along with mutagenesis experiments reveals an allosteric mechanism of inhibition; the compound induces rearrangements of substrate binding residues and of Arg(176), a trigger between the active site and allosteric site. Our results thus provide 1) novel insights into the communication between allosteric regulatory and active sites, 2) a novel mechanism for sAC inhibition, and 3) pharmacological compounds targeting this allosteric site and utilizing this mode of inhibition. These studies provide support for the future development of sAC-modulating drugs. PMID:26961873

  19. The Structure of KinA-Sda Complex Suggests An Allosteric Mechanism of Histidine Kinase Inhibition

    SciTech Connect

    Whitten, A.E.; Jacques, D.A.; Hammouda, B.; Hanley, T.; King, G.F.; Guss, J.Mitchell.; Trewhella, J.; Langley, D.B.; /Sydney U. /NIST, Wash., D.C. /Utah U.

    2007-07-13

    The Bacillus subtilis histidine kinase KinA controls activation of the transcription factor governing sporulation, Spo0A. The decision to sporulate involves KinA phosphorylating itself on a conserved histidine residue, after which the phosphate moiety is relayed via two other proteins to Spo0A. The DNA-damage checkpoint inhibitor Sda halts this pathway by binding KinA and blocking the autokinase reaction. We have performed small-angle X-ray scattering and neutron contrast variation studies on the complex formed by KinA and Sda. The data show that two Sda molecules bind to the base of the DHp dimerization domain of the KinA dimer. In this position Sda does not appear to be able to sterically block the catalytic domain from accessing its target histidine, as previously proposed, but rather may effect an allosteric mode of inhibition involving transmission of the inhibitory signal via the four-helix bundle that forms the DHp domain.

  20. Sensitivity and kinetics of signal transmission at the first visual synapse differentially impact visually-guided behavior

    PubMed Central

    Sarria, Ignacio; Pahlberg, Johan; Cao, Yan; Kolesnikov, Alexander V; Kefalov, Vladimir J; Sampath, Alapakkam P; Martemyanov, Kirill A

    2015-01-01

    In the retina, synaptic transmission between photoreceptors and downstream ON-bipolar neurons (ON-BCs) is mediated by a GPCR pathway, which plays an essential role in vision. However, the mechanisms that control signal transmission at this synapse and its relevance to behavior remain poorly understood. In this study we used a genetic system to titrate the rate of GPCR signaling in ON-BC dendrites by varying the concentration of key RGS proteins and measuring the impact on transmission of signal between photoreceptors and ON-BC neurons using electroretinography and single cell recordings. We found that sensitivity, onset timing, and the maximal amplitude of light-evoked responses in rod- and cone-driven ON-BCs are determined by different RGS concentrations. We further show that changes in RGS concentration differentially impact visually guided-behavior mediated by rod and cone ON pathways. These findings illustrate that neuronal circuit properties can be modulated by adjusting parameters of GPCR-based neurotransmission at individual synapses. DOI: http://dx.doi.org/10.7554/eLife.06358.001 PMID:25879270

  1. 47 CFR 11.51 - EAS code and Attention Signal Transmission requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...) Analog and digital broadcast stations must transmit, either automatically or manually, national level EAS... Message (EOM) codes using the EAS Protocol. The Attention Signal must precede any emergency audio message. After January 1, 1998, the shortened Attention Signal may only be used as an audio alert signal and...

  2. 50th anniversary of the word "allosteric".

    PubMed

    Changeux, Jean-Pierre

    2011-07-01

    A brief historical account on the origin and meaning of the word "allosteric" is presented. The word was coined in an attempt to qualify the chemical mechanism of the feedback inhibition of bacterial enzymes by regulatory ligands. The data lead to the proposal that, at variance with the classical mechanism of mutual exclusion by steric hindrance, the inhibition takes place through an "allosteric" interaction between "no overlapping", stereospecifically distinct, sites for substrate and feedback inhibitor, mediated by a discrete reversible alteration of the molecular structure of the protein. PMID:21574197

  3. Rational design of allosteric regulation of homoserine dehydrogenase by a nonnatural inhibitor L-lysine.

    PubMed

    Chen, Zhen; Rappert, Sugima; Zeng, An-Ping

    2015-02-20

    Allosteric proteins, which can sense different signals, are interesting biological parts for synthetic biology. In particular, the design of an artificial allosteric enzyme to sense an unnatural signal is both challenging and highly desired, for example, for a precise and dynamical control of fluxes of growth-essential but byproduct pathways in metabolic engineering of industrial microorganisms. In this work, we used homoserine dehydrogenase (HSDH) of Corynebacterium glutamicum, which is naturally allosterically regulated by threonine and isoleucine, as an example to demonstrate the feasibility of reengineering an allosteric enzyme to respond to an unnatural inhibitor L-lysine. For this purpose, the natural threonine binding sites of HSD were first predicted and verified by mutagenesis experiments. The threonine binding sites were then engineered to a lysine binding pocket. The reengineered HSD only responds to lysine inhibition but not to threonine. This is a significant step toward the construction of artificial molecular circuits for dynamic control of growth-essential byproduct formation pathway for lysine biosynthesis. PMID:24344690

  4. In-vivo signal transmission using an intra-corporal RF transmitter.

    PubMed

    Just, T; Laqua, D; Husar, P

    2011-01-01

    In clinical routine, measurements of human physiological parameters are very important. In this paper, a study of RF transmission from the inside to the outside of a biological body is described. In the course of this work, an overview of the state of the art of wireless biotelemetry and the basics of biological tissue attenuation are given. In addition, several prototype transmitters were designed and developed with frequencies ranging from 50 to 700 MHz. With these transmitters a study of an in-vivo transmission was run to measure realistic attenuation values of a living biological subject. In the evaluation phase, a prototype transmitter was placed in the esophagus, near the heart, of a narcotized living pig. This allows demonstrating the transmission out of an animal with human-like tissue properties. The results show a possible transmission at 58, 119, 240, 418 and 672 MHz with acceptable loss. PMID:22256113

  5. Sound transmission and the recognition of temporally degraded sexual advertisement signals in Cope's gray treefrog (Hyla chrysoscelis)

    PubMed Central

    Kuczynski, Michael C.; Vélez, Alejandro; Schwartz, Joshua J.; Bee, Mark A.

    2010-01-01

    Acoustic communication signals degrade as they propagate between signalers and receivers. While we generally understand the degrading effects of sound propagation on the structure of acoustic signals, we know considerably less about how receivers make behavioral decisions based on the perception of degraded signals in sonically and structurally complex habitats where communication occurs. In this study of acoustic mate recognition in Cope's gray treefrog, Hyla chrysoscelis (Cope 1880), we investigated how the temporal structure of male advertisement calls was compromised by propagation in a natural habitat and how females responded to stimuli mimicking various levels of temporal degradation. In a sound transmission experiment, we quantified changes in the pulsed structure of signals by broadcasting synthetic calls during active choruses from positions where we typically encountered signalers, and re-recording the signals from positions where we typically encountered potential receivers. Our main finding was that the silent gaps between pulses become increasingly ‘filled in’ by background noise and reverberations as a function of increasing propagation distance. We also conducted female phonotaxis experiments to determine the threshold modulation depth required to elicit recognition of the pulsatile structure of the call. Females were surprisingly tolerant of degraded temporal structure, and there was a tendency for greater permissiveness at lower playback levels. We discuss these results in terms of presumed mechanisms of call recognition in complex environments and the acoustic adaptation hypothesis. PMID:20675554

  6. Signal processing algorithm of newly developed transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Lee, Jung-Ju; Kwon, Il-Bum

    2000-06-01

    The newly developed TEFPI (transmission-type extrinsic Fabry- Perot interferometric) optical fiber sensor can distinguish the direction of measurement more simply and effectively than the conventional reflection-type EFPI optical fiber sensors. The output signal of the TEFPI optical fiber sensor has the characteristics that the signal level of fringes shows a negative slope for a tensile direction and a positive slope for a compressive direction. Based on these characteristics, the direction of measurement of the TEFPI optical fiber sensor can be distinguished with ease. In this paper, the signal processing algorithm adequate to the TEFPI optical fiber sensor was developed. This algorithm can process signal with recognition of the positions of peaks, valleys and signal levels of fringes. Thus this can determine a measurement direction and the positions of direction changes by using the change trend of signal levels. The developed algorithm makes the post-process and real-time process of the signal of the TEFPI optical fiber sensor possible.

  7. Seamless integration of 57.2-Gb/s signal wireline transmission and 100-GHz wireless delivery.

    PubMed

    Li, Xinying; Yu, Jianjun; Dong, Ze; Cao, Zizheng; Chi, Nan; Zhang, Junwen; Shao, Yufeng; Tao, Li

    2012-10-22

    We experimentally demonstrated the seamless integration of 57.2-Gb/s signal wireline transmission and 100-GHz wireless delivery adopting polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) modulation with 400-km single-mode fiber-28 (SMF-28) transmission and 1-m wireless delivery. The X- and Y-polarization components of optical PDM-QPSK baseband signal are simultaneously up-converted to 100 GHz by optical polarization-diversity heterodyne beating, and then independently transmitted and received by two pairs of transmitter and receiver antennas, which make up a 2x2 multiple-input multiple-output (MIMO) wireless link based on microwave polarization multiplexing. At the wireless receiver, a two-stage down conversion is firstly done in analog domain based on balanced mixer and sinusoidal radio frequency (RF) signal, and then in digital domain based on digital signal processing (DSP). Polarization de-multiplexing is realized by constant modulus algorithm (CMA) based on DSP in heterodyne coherent detection. Our experimental results show that more taps are required for CMA when the X- and Y-polarization antennas have different wireless distance. PMID:23187199

  8. Cell speed, persistence and information transmission during signal relay and collective migration.

    PubMed

    McCann, Colin P; Kriebel, Paul W; Parent, Carole A; Losert, Wolfgang

    2010-05-15

    Collective migration is a key feature of the social amoebae Dictyostelium discoideum, where the binding of chemoattractants leads to the production and secretion of additional chemoattractant and the relay of the signal to neighboring cells. This then guides cells to migrate collectively in a head-to-tail fashion. We used mutants that were defective in signal relay to elucidate which quantitative metrics of cell migration are most strongly affected by signal relay and collective motion. We show that neither signal relay nor collective motion markedly impact the speed of cell migration. Cells maintained a preferred overall direction of motion for several minutes with similar persistence, regardless of whether or not they were attracted to moving neighbors, moving collectively in contact with their neighbors, or simply following a fixed exogenous signal. We quantitatively establish that signal relay not only increases the number of cells that respond to a chemotactic signal, but most remarkably, also transmits information about the location of the source accurately over large distances, independently of the strength of the exogenous signal. We envision that signal relay has a similar key role in the migration of a variety of chemotaxing mammalian cells that can relay chemoattractant signals. PMID:20427323

  9. Intersubunit signal transmission in integrins by a receptor-like interaction with a pull spring

    PubMed Central

    Yang, Wei; Shimaoka, Motomu; Salas, Azucena; Takagi, Junichi; Springer, Timothy A.

    2004-01-01

    The function of some multidomain proteins is regulated by interdomain communication. We use second-site suppressor cysteine mutations to test a hypothesis on how the inserted (I)-like domain in the integrin β-subunit regulates ligand binding by the neighboring I domain in the integrin α-subunit [Huth, J. R., Olejniczak, E. T., Mendoza, R., Liang, H., Harris, E. A., et al. (2000) Proc. Natl. Acad. Sci. USA 97, 5231–5236; and Alonso, J. L., Essafi, M., Xiong, J. P., Stehle, T. & Arnaout, M. A. (2002) Curr. Biol. 12, R340–R342]. The hypothesis is that an interaction between the β I-like metal ion-dependent adhesion site (MIDAS) and an intrinsic ligand in the linker following the α I domain, Glu-310, exerts a pull that activates the α I domain. Individual mutation of αL linker residue Glu-310 or β2 MIDAS residues Ala-210 or Tyr-115 to cysteine abolishes I domain activation, whereas the double mutation of αL-E310C with either β2-A210C or β2-Y115C forms a disulfide bond that constitutively activates ligand binding. The disulfide-bonded mutant is resistant to small molecule antagonists that bind to the β I-like domain near its interface with the α I domain and inhibit communication between these domains but remains susceptible to small molecule antagonists that bind underneath the I domain α7-helix and certain allosteric antagonistic antibodies. Thus, the α7-helix and its linker are better modeled as a pull spring than a bell rope. The results suggest that αL residue Glu-310, which is universally conserved in all I domain-containing integrins, functions as an intrinsic ligand for the β I-like domain, and that when integrins are activated, the β I-like MIDAS binds to Glu-310, pulls the spring, and thereby activates the α I domain. PMID:14978279

  10. Allosteric substrate switching in a voltage-sensing lipid phosphatase.

    PubMed

    Grimm, Sasha S; Isacoff, Ehud Y

    2016-04-01

    Allostery provides a critical control over enzyme activity, biasing the catalytic site between inactive and active states. We found that the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), which modifies phosphoinositide signaling lipids (PIPs), has not one but two sequential active states with distinct substrate specificities, whose occupancy is allosterically controlled by sequential conformations of the voltage-sensing domain (VSD). Using fast fluorescence resonance energy transfer (FRET) reporters of PIPs to monitor enzyme activity and voltage-clamp fluorometry to monitor conformational changes in the VSD, we found that Ci-VSP switches from inactive to a PIP3-preferring active state when the VSD undergoes an initial voltage-sensing motion and then into a second PIP2-preferring active state when the VSD activates fully. This two-step allosteric control over a dual-specificity enzyme enables voltage to shape PIP concentrations in time, and provides a mechanism for the complex modulation of PIP-regulated ion channels, transporters, cell motility, endocytosis and exocytosis. PMID:26878552

  11. Dancing through Life: Molecular Dynamics Simulations and Network-Centric Modeling of Allosteric Mechanisms in Hsp70 and Hsp110 Chaperone Proteins

    PubMed Central

    Stetz, Gabrielle; Verkhivker, Gennady M.

    2015-01-01

    Hsp70 and Hsp110 chaperones play an important role in regulating cellular processes that involve protein folding and stabilization, which are essential for the integrity of signaling networks. Although many aspects of allosteric regulatory mechanisms in Hsp70 and Hsp110 chaperones have been extensively studied and significantly advanced in recent experimental studies, the atomistic picture of signal propagation and energetics of dynamics-based communication still remain unresolved. In this work, we have combined molecular dynamics simulations and protein stability analysis of the chaperone structures with the network modeling of residue interaction networks to characterize molecular determinants of allosteric mechanisms. We have shown that allosteric mechanisms of Hsp70 and Hsp110 chaperones may be primarily determined by nucleotide-induced redistribution of local conformational ensembles in the inter-domain regions and the substrate binding domain. Conformational dynamics and energetics of the peptide substrate binding with the Hsp70 structures has been analyzed using free energy calculations, revealing allosteric hotspots that control negative cooperativity between regulatory sites. The results have indicated that cooperative interactions may promote a population-shift mechanism in Hsp70, in which functional residues are organized in a broad and robust allosteric network that can link the nucleotide-binding site and the substrate-binding regions. A smaller allosteric network in Hsp110 structures may elicit an entropy-driven allostery that occurs in the absence of global structural changes. We have found that global mediating residues with high network centrality may be organized in stable local communities that are indispensable for structural stability and efficient allosteric communications. The network-centric analysis of allosteric interactions has also established that centrality of functional residues could correlate with their sensitivity to mutations

  12. Photonic-aided pre-coding QAM signal transmission in multi-antenna radio over fiber system

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Yu, Jianjun; Li, Xinying; Zhu, Ming; Xin, Xiangjun; Chang, Gee-Kung

    2015-11-01

    A novel method has been proposed and experimentally demonstrated to provide photonic-aided pre-coding quadrature amplitude modulation (QAM) signal transmission in multi-antenna radio over fiber system to increase the throughput. For downlink, two different multi-level amplitude-shift-keying (M-ASK) modulated signals, such as 4-ASK signals, are applied on two uncorrelated optical Mach-Zehnder modulators at central office. After photonic-aided pre-coding module and photo-detection process, the received M-ASK mm-waves from two remote access units (RAUs) can be synthesized to a M2-QAM signal in the proposed system. Regardless of forward error correction (FEC) coding overhead, the 4-Gb/s and 8-Gb/s 16-QAM mm-wave signals are obtained from two independent 2-Gb/s and 4-Gb/s 4-ASK 40-GHz channels, respectively. The experimental results show that a doubled bit rate of the original 4-ASK one can be achieved without additional digital signal processing (DSP) in small cell RAUs and mobile users.

  13. VU0477573: Partial Negative Allosteric Modulator of the Subtype 5 Metabotropic Glutamate Receptor with In Vivo Efficacy.

    PubMed

    Nickols, Hilary Highfield; Yuh, Joannes P; Gregory, Karen J; Morrison, Ryan D; Bates, Brittney S; Stauffer, Shaun R; Emmitte, Kyle A; Bubser, Michael; Peng, Weimin; Nedelcovych, Michael T; Thompson, Analisa; Lv, Xiaohui; Xiang, Zixiu; Daniels, J Scott; Niswender, Colleen M; Lindsley, Craig W; Jones, Carrie K; Conn, P Jeffrey

    2016-01-01

    Negative allosteric modulators (NAMs) of metabotropic glutamate receptor subtype 5 (mGlu5) have potential applications in the treatment of fragile X syndrome, levodopa-induced dyskinesia in Parkinson disease, Alzheimer disease, addiction, and anxiety; however, clinical and preclinical studies raise concerns that complete blockade of mGlu5 and inverse agonist activity of current mGlu5 NAMs contribute to adverse effects that limit the therapeutic use of these compounds. We report the discovery and characterization of a novel mGlu5 NAM, N,N-diethyl-5-((3-fluorophenyl)ethynyl)picolinamide (VU0477573) that binds to the same allosteric site as the prototypical mGlu5 NAM MPEP but displays weak negative cooperativity. Because of this weak cooperativity, VU0477573 acts as a "partial NAM" so that full occupancy of the MPEP site does not completely inhibit maximal effects of mGlu5 agonists on intracellular calcium mobilization, inositol phosphate (IP) accumulation, or inhibition of synaptic transmission at the hippocampal Schaffer collateral-CA1 synapse. Unlike previous mGlu5 NAMs, VU0477573 displays no inverse agonist activity assessed using measures of effects on basal [(3)H]inositol phosphate (IP) accumulation. VU0477573 acts as a full NAM when measuring effects on mGlu5-mediated extracellular signal-related kinases 1/2 phosphorylation, which may indicate functional bias. VU0477573 exhibits an excellent pharmacokinetic profile and good brain penetration in rodents and provides dose-dependent full mGlu5 occupancy in the central nervous system (CNS) with systemic administration. Interestingly, VU0477573 shows robust efficacy, comparable to the mGlu5 NAM MTEP, in models of anxiolytic activity at doses that provide full CNS occupancy of mGlu5 and demonstrate an excellent CNS occupancy-efficacy relationship. VU0477573 provides an exciting new tool to investigate the efficacy of partial NAMs in animal models. PMID:26503377

  14. An autonomous battery-less sensor module powered by piezoelectric energy harvesting with RF transmission of multiple measurement signals

    NASA Astrophysics Data System (ADS)

    Ferrari, Marco; Ferrari, Vittorio; Guizzetti, Michele; Marioli, Daniele

    2009-08-01

    An energy-autonomous battery-less sensor module is presented, entirely powered by a piezoelectric energy converter driven by mechanical vibrations from the environment. The module manages and stores the converted energy, interfaces to one or more passive sensors and periodically sends the corresponding measurement signals over a radio-frequency (RF) link. As an additional variant, the module can send a programmable identification (ID) code on the RF carrier, in order to enable module tagging and tracking by the external receiver unit. The module's general architecture is presented and the strategy used for sensor signal conditioning and transmission is illustrated. The architecture and principle have been experimentally validated on a fabricated prototype including a piezoelectric bimorph converter, two passive sensors made by a resistive-capacitive sensor pair and purposely designed electronic circuitry based on low-power off-the-shelf components. In the tested experimental conditions, the prototype features a typical time interval between measurement-and-transmission events of a few tens of seconds, with event durations of the order of tens of milliseconds, corresponding to an operation duty cycle of the order of 0.1%. Peak power consumption during transmission is of the order of 20 mW and operative range is of the order of meters in a laboratory environment. The obtained results show that the proposed approach has attractive characteristics because of the total absence of batteries and, despite the inherent intermittent operation, provides significant measurement performances in terms of achievable sensitivity and resolution.

  15. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    PubMed Central

    Shaddad, R. Q.; Mohammad, A. B.; Al-Gailani, S. A.; Al-Hetar, A. M.

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. PMID:24772009

  16. Shifting Spike Times or Adding and Deleting Spikes-How Different Types of Noise Shape Signal Transmission in Neural Populations.

    PubMed

    Voronenko, Sergej O; Stannat, Wilhelm; Lindner, Benjamin

    2015-12-01

    We study a population of spiking neurons which are subject to independent noise processes and a strong common time-dependent input. We show that the response of output spikes to independent noise shapes information transmission of such populations even when information transmission properties of single neurons are left unchanged. In particular, we consider two Poisson models in which independent noise either (i) adds and deletes spikes (AD model) or (ii) shifts spike times (STS model). We show that in both models suprathreshold stochastic resonance (SSR) can be observed, where the information transmitted by a neural population is increased with addition of independent noise. In the AD model, the presence of the SSR effect is robust and independent of the population size or the noise spectral statistics. In the STS model, the information transmission properties of the population are determined by the spectral statistics of the noise, leading to a strongly increased effect of SSR in some regimes, or an absence of SSR in others. Furthermore, we observe a high-pass filtering of information in the STS model that is absent in the AD model. We quantify information transmission by means of the lower bound on the mutual information rate and the spectral coherence function. To this end, we derive the signal-output cross-spectrum, the output power spectrum, and the cross-spectrum of two spike trains for both models analytically. PMID:26458900

  17. Syncrip/hnRNP Q influences synaptic transmission and regulates BMP signaling at the Drosophila neuromuscular synapse

    PubMed Central

    Halstead, James M.; Lin, Yong Qi; Durraine, Lita; Hamilton, Russell S.; Ball, Graeme; Neely, Greg G.; Bellen, Hugo J.; Davis, Ilan

    2014-01-01

    ABSTRACT Synaptic plasticity involves the modulation of synaptic connections in response to neuronal activity via multiple pathways. One mechanism modulates synaptic transmission by retrograde signals from the post-synapse that influence the probability of vesicle release in the pre-synapse. Despite its importance, very few factors required for the expression of retrograde signals, and proper synaptic transmission, have been identified. Here, we identify the conserved RNA binding protein Syncrip as a new factor that modulates the efficiency of vesicle release from the motoneuron and is required for correct synapse structure. We show that syncrip is required genetically and its protein product is detected only in the muscle and not in the motoneuron itself. This unexpected non-autonomy is at least partly explained by the fact that Syncrip modulates retrograde BMP signals from the muscle back to the motoneuron. We show that Syncrip influences the levels of the Bone Morphogenic Protein ligand Glass Bottom Boat from the post-synapse and regulates the pre-synapse. Our results highlight the RNA-binding protein Syncrip as a novel regulator of synaptic output. Given its known role in regulating translation, we propose that Syncrip is important for maintaining a balance between the strength of presynaptic vesicle release and postsynaptic translation. PMID:25171887

  18. Allosteric and hyperekplexic mutant phenotypes investigated on an α1 glycine receptor transmembrane structure

    PubMed Central

    Moraga-Cid, Gustavo; Sauguet, Ludovic; Huon, Christèle; Malherbe, Laurie; Girard-Blanc, Christine; Petres, Stéphane; Murail, Samuel; Taly, Antoine; Baaden, Marc; Delarue, Marc; Corringer, Pierre-Jean

    2015-01-01

    The glycine receptor (GlyR) is a pentameric ligand-gated ion channel (pLGIC) mediating inhibitory transmission in the nervous system. Its transmembrane domain (TMD) is the target of allosteric modulators such as general anesthetics and ethanol and is a major locus for hyperekplexic congenital mutations altering the allosteric transitions of activation or desensitization. We previously showed that the TMD of the human α1GlyR could be fused to the extracellular domain of GLIC, a bacterial pLGIC, to form a functional chimera called Lily. Here, we overexpress Lily in Schneider 2 insect cells and solve its structure by X-ray crystallography at 3.5 Å resolution. The TMD of the α1GlyR adopts a closed-channel conformation involving a single ring of hydrophobic residues at the center of the pore. Electrophysiological recordings show that the phenotypes of key allosteric mutations of the α1GlyR, scattered all along the pore, are qualitatively preserved in this chimera, including those that confer decreased sensitivity to agonists, constitutive activity, decreased activation kinetics, or increased desensitization kinetics. Combined structural and functional data indicate a pore-opening mechanism for the α1GlyR, suggesting a structural explanation for the effect of some key hyperekplexic allosteric mutations. The first X-ray structure of the TMD of the α1GlyR solved here using GLIC as a scaffold paves the way for mechanistic investigation and design of allosteric modulators of a human receptor. PMID:25730860

  19. Allosteric communication pathways and thermal rectification in PDZ-2 protein: a computational study.

    PubMed

    Miño-Galaz, Germán A

    2015-05-21

    Allosteric communication in proteins is a fundamental and yet unresolved problem of structural biochemistry. Previous findings, from computational biology ( Ota, N.; Agard, D. A. J. Mol. Biol. 2005 , 351 , 345 - 354 ), have proposed that heat diffuses in a protein through cognate protein allosteric pathways. This work studied heat diffusion in the well-known PDZ-2 protein, and confirmed that this protein has two cognate allosteric pathways and that heat flows preferentially through these. Also, a new property was also observed for protein structures: heat diffuses asymmetrically through the structures. The underling structure of this asymmetrical heat flow was a normal length hydrogen bond (∼2.85 Å) that acted as a thermal rectifier. In contrast, thermal rectification was compromised in short hydrogen bonds (∼2.60 Å), giving rise to symmetrical thermal diffusion. Asymmetrical heat diffusion was due, on a higher scale, to the local, structural organization of residues that, in turn, was also mediated by hydrogen bonds. This asymmetrical/symmetrical energy flow may be relevant for allosteric signal communication directionality in proteins and for the control of heat flow in materials science. PMID:25933631

  20. 120 Gbit/s injection-locked homodyne coherent transmission of polarization-multiplexed 64 QAM signals over 150 km.

    PubMed

    Wang, Yixin; Kasai, Keisuke; Yoshida, Masato; Nakazawa, Masataka

    2014-12-15

    We describe an injection-locked 64 QAM homodyne coherent transmission, which is the highest QAM multiplicity realized with an injection locking technique. The frequency locking range of the local oscillator (LO) was as wide as 1 GHz. The phase noise was only 0.2 deg, which is 1/3 of that obtained with our previous OVCO-based OPLL (0.6 deg.). As a result, a 120 Gbit/s polarization-multiplexed 64 QAM signal was successfully transmitted over 150 km with a simple receiver configuration and low DSP complexity. PMID:25607079

  1. Bi-directional transmission of 8x10Gb/s DPSK signals over 80km of SMF-28 Fiber using in-line semiconductor optical amplifier.

    PubMed

    Yu, Jianjun; Yeo, Yong-Kee; Akanbi, Oladeji; Chang, Gee-Kung

    2004-12-13

    We report the bi-directional transmission of 8x10Gb/s signals using an in-line SOA over 80km SMF-28 with matching DCF for the first time. Our results suggest very promising applications for bi-directional transmission in metro and access networks with simple configuration and low cost. PMID:19488266

  2. Optical wireless transmission of 405 nm, 1.45 Gbit/s optical IM/DD-OFDM signals through a 4.8 m underwater channel.

    PubMed

    Nakamura, Kazuhiko; Mizukoshi, Izumi; Hanawa, Masanori

    2015-01-26

    In this paper, we experimentally demonstrate wireless transmission of optical intensity modulation/direct detection-orthogonal frequency division multiplexing (IM/DD-OFDM) signals in an underwater channel using a field programmable gate array based real-time transmitter. The real-time transmission of a 405 nm 1.45 Gbit/s optical OFDM signal through a 4.8 m underwater channel with an error vector magnitude of approximately 10% was successfully achieved. PMID:25835913

  3. Delineation of the functional properties and the mechanism of action of TMPPAA, an allosteric agonist and positive allosteric modulator of 5-HT3 receptors.

    PubMed

    Gasiorek, Agnes; Trattnig, Sarah M; Ahring, Philip K; Kristiansen, Uffe; Frølund, Bente; Frederiksen, Kristen; Jensen, Anders A

    2016-06-15

    We have previously identified a novel class of 5-hydroxytryptamine type 3 receptor (5-HT3R) agonists sharing little structural similarity with orthosteric 5-HT3R ligands (Jørgensen et al., 2011). In the present study we have elucidated the functional characteristics and the mechanism of action of one of these compounds, trans-3-(4-methoxyphenyl)-N-(pentan-3-yl)acrylamide (TMPPAA). In electrophysiological recordings TMPPAA was found to be a highly-efficacious partial agonist equipotent with 5-HT at the 5-HT3A receptor (5-HT3AR) expressed in COS-7 cells and somewhat less potent at the receptor expressed in Xenopus oocytes. The desensitization kinetics of TMPPAA-evoked currents were very different from those mediated by 5-HT. Moreover, repeated TMPPAA applications resulted in progressive current run-down and persistent non-responsiveness of the receptor to TMPPAA, but not to 5-HT. In addition to its direct activation, TMPPAA potentiated 5-HT-mediated 5-HT3AR signalling, and the allosteric link between the two binding sites was corroborated by the analogous ability of 5-HT to potentiate TMPPAA-evoked responses. The agonism and potentiation exerted by TMPPAA at a chimeric α7-nACh/5-HT3A receptor suggested that the ligand acts through the transmembrane domain of 5-HT3AR, a notion further substantiated by its functional properties at chimeric and mutant human/murine 5-HT3ARs. A residue in the transmembrane helix 4 of 5-HT3A was identified as an important molecular determinant for the different agonist potencies exhibited by TMPPAA at human and murine 5-HT3ARs. In conclusion, TMPPAA is a novel allosteric agonist and positive allosteric modulator of 5-HT3Rs, and its aberrant signalling characteristics compared to 5-HT at the 5-HT3AR underline the potential in Cys-loop receptor modulation and activation through allosteric sites. PMID:27086281

  4. Time domain zero-padding based adaptive-PAM signal transmission with high spectral efficiency in IMDD optical communication system

    NASA Astrophysics Data System (ADS)

    Zhang, Fangliu; He, Jing; Deng, Rui; Cheng, Yun; Xiao, Minlei; Chen, Lin

    2016-08-01

    In this paper, an adaptive pulse amplitude modulation (APAM) scheme is proposed and experimentally demonstrated in the intensity-modulation and direct-detection (IMDD) optical communications system. In the proposed scheme, the channel is divided into two sub-channels, and different PAM mapping can be chosen for different sub-channel according to the fading conditions. In addition, the 20-km standard single mode fiber (SSMF) transmission of 24 Gbit/s 16/4-APAM signal with the spectral efficiency (SE) up to 6 bit/s/Hz is experimentally demonstrated. The experiment results show that the bit error rate (BER) of the 16/4-APAM signal can be achieved less than 2.4e-2.

  5. Development of two-dimensional multiwire-type neutron detector system with individual line readout and optical signal transmission

    NASA Astrophysics Data System (ADS)

    Toh, K.; Nakamura, T.; Sakasai, K.; Soyama, K.; Hino, M.; Kitaguchi, M.; Yamagishi, H.

    2013-10-01

    A multiwire-type two-dimensional neutron detector system with a sensitive area of 128×128 mm2 is developed for use in the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex. The system can achieve a short response time and high spatial resolution using the individual line readout method. Optical devices have been incorporated in the system for long-distance signal transmission and insulation between a detector head in the neutron shielding and signal processing circuits in the data acquisition room. The detector system exhibits a pulse-pair resolution of 1 μs, an average spatial resolution of less than 2 mm full width at half-maximum in the sensitive region, and a two-dimensional homogeneity of 8.3% in all pixels.

  6. Enhancing allosteric inhibition in Thermus thermophilus Phosphofructokinase.

    PubMed

    McGresham, Maria S; Reinhart, Gregory D

    2015-01-27

    The coupling between the binding of the substrate Fru-6-P and the inhibitor phospho(enol)pyruvate (PEP) in phosphofructokinase (PFK) from the extreme thermophile Thermus thermophilus is much weaker than that seen in a PFK from Bacillus stearothermophilus. From the crystal structures of Bacillus stearothermophilus PFK (BsPFK) the residues at positions 59, 158, and 215 in BsPFK are located on the path leading from the allosteric site to the nearest active site and are part of the intricate hydrogen-bonding network connecting the two sites. Substituting the corresponding residues in Thermus thermophilus PFK (TtPFK) with the amino acids found at these positions in BsPFK allowed us to enhance the allosteric inhibition by PEP by nearly 3 kcal mol(-1) (50-fold) to a value greater than or equal to the coupling observed in BsPFK. Interestingly, each single variant N59D, A158T, and S215H produced a roughly 1 kcal mol(-1) increase in coupling free energy of inhibition. The effects of these variants were essentially additive in the three combinations of double variants N59D/A158T, N59D/S215H, and A158T/S215H as well as in the triple variant N59D/A158T/S215H. Consequently, while the hydrogen-bonding network identified is likely involved in the inhibitory allosteric communication, a model requiring a linked chain of interactions connecting the sites is not supported by these data. Despite the fact that the allosteric activator of the bacterial PFK, MgADP, binds at the same allosteric site, the substitutions at positions 59, 158, and 215 do not have an equally dramatic effect on the binding affinity and the allosteric activation by MgADP. The effect of the S215H and N59D/A158T/S215H substitutions on the activation by MgADP could not be determined because of a dramatic drop in MgADP binding affinity that resulted from the S215H substitution. The single variants N59D and A158T supported binding but showed little change in the free energy of activation by MgADP compared to the wild

  7. A small animal PET based on GAPDs and charge signal transmission approach for hybrid PET-MR imaging

    NASA Astrophysics Data System (ADS)

    Kang, Jihoon; Choi, Yong; Hong, Key Jo; Hu, Wei; Jung, Jin Ho; Huh, Yoonsuk; Kim, Byung-Tae

    2011-08-01

    Positron emission tomography (PET) employing Geiger-mode avalanche photodiodes (GAPDs) and charge signal transmission approach was developed for small animal imaging. Animal PET contained 16 LYSO and GAPD detector modules that were arranged in a 70 mm diameter ring with an axial field of view of 13 mm. The GAPDs charge output signals were transmitted to a preamplifier located remotely using 300 cm flexible flat cables. The position decoder circuits (PDCs) were used to multiplex the PET signals from 256 to 4 channels. The outputs of the PDCs were digitized and further-processed in the data acquisition unit. The cross-compatibilities of the PET detectors and MRI were assessed outside and inside the MRI. Experimental studies of the developed full ring PET were performed to examine the spatial resolution and sensitivity. Phantom and mouse images were acquired to examine the imaging performance. The mean energy and time resolution of the PET detector were 17.6% and 1.5 ns, respectively. No obvious degradation on PET and MRI was observed during simultaneous PET-MRI data acquisition. The measured spatial resolution and sensitivity at the CFOV were 2.8 mm and 0.7%, respectively. In addition, a 3 mm diameter line source was clearly resolved in the hot-sphere phantom images. The reconstructed transaxial PET images of the mouse brain and tumor displaying the glucose metabolism patterns were imaged well. These results demonstrate GAPD and the charge signal transmission approach can allow the development of high performance small animal PET with improved MR compatibility.

  8. Cross-synaptic synchrony and transmission of signal and noise across the mouse retina.

    PubMed

    Grimes, William N; Hoon, Mrinalini; Briggman, Kevin L; Wong, Rachel O; Rieke, Fred

    2014-01-01

    Cross-synaptic synchrony--correlations in transmitter release across output synapses of a single neuron--is a key determinant of how signal and noise traverse neural circuits. The anatomical connectivity between rod bipolar and A17 amacrine cells in the mammalian retina, specifically that neighboring A17s often receive input from many of the same rod bipolar cells, provides a rare technical opportunity to measure cross-synaptic synchrony under physiological conditions. This approach reveals that synchronization of rod bipolar cell synapses is near perfect in the dark and decreases with increasing light level. Strong synaptic synchronization in the dark minimizes intrinsic synaptic noise and allows rod bipolar cells to faithfully transmit upstream signal and noise to downstream neurons. Desynchronization in steady light lowers the sensitivity of the rod bipolar output to upstream voltage fluctuations. This work reveals how cross-synaptic synchrony shapes retinal responses to physiological light inputs and, more generally, signaling in complex neural networks. PMID:25180102

  9. Compensation of chromatic-dispersion for full-duplex radio-over-fiber links with vector signal transmission using frequency tripling

    NASA Astrophysics Data System (ADS)

    Gao, Chao; Huang, Shanguo; Xiao, Jinghua; Gao, Xinlu; Wang, Qian; Wei, Yongfeng; Zhai, Wensheng; Xu, Wenjing; Gu, Wanyi

    2014-10-01

    This paper demonstrates the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link, and a symmetry theory for compensation. A 60 GHz full-duplex ROF system with vector signal transmission using frequency-tripling modulation (FTM) is also proposed. The simulations for both 5 Gbps and 200 Mbps 16 QAM signal transmission show that the CD-induced CR can be entirely overcome due to the proposed method, and the proposed ROF schedule still maintains good performance even after 500 km of 200 Mbps vector signal transmission. Meanwhile, the central station is significantly simplified and cost-effective since only one 15 GHz local oscillator is needed for both the generation of an optical millimeter-wave signal and the carrier of the downlink intermediate-frequency (IF) signal.

  10. Stable transmission of radio frequency signals on fiber links using interferomectric delay sensing

    SciTech Connect

    Wilcox, Russell B.; Byrd, J.M.; Doolittle, Lawrence; Huang, Gang; Staples, J.W.

    2009-07-29

    The authors demonstrate distribution of a 2850 MHz rf signal over stabilized optical fiber links. For a 2.2 km link they measure an rms drift of 19.4 fs over 60 h, and for a 200 m link an rms drift of 8.4 fs over 20 h. The rf signals are transmitted as amplitude modulation on a continuous optical carrier. Variations in the delay length are sensed using heterodyne interferometry and used to correct the rf phase. The system uses standard fiber telecommunications components.

  11. A system analysis of the 13.3 GHz scatterometer. [antenna patterns and signal transmission

    NASA Technical Reports Server (NTRS)

    Wang, J. R.

    1977-01-01

    The performance of the 13.3 GHz airborne scatterometer system which is used as a microwave remote sensor to detect moisture content of soil is analyzed with respect to its antenna pattern, the signal flow in the receiver data channels, and the errors in the signal outputs. The operational principle and the sensitivity of the system, as well as data handling are also described. The dielectric property of the terrain surface, as far as the scatterometer is concerned, is contained in the assumed forms of the functional dependence of the backscattering coefficient of the incident angle.

  12. A novel optical transmission link with DHT-based constant envelope optical OFDM signal

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Liang, Hao

    2013-07-01

    In this paper, we have proposed a novel optical OFDM transmission link that takes advantages of discrete Hartley Transform (DHT) and constant envelope (CE) modulation, obtaining DHT-based constant envelope optical OFDM. The numerical results show that this design achieves better performance when compared with conventional O-OFDM in terms of bit error rate (BER) and peak-to-average power ratio (PAPR). The impact of phase modulation index (PMI) on both PAPR and noise tolerance is investigated. Since the scheme has simplified design, it is believed to be a cost-effective in the practical implement.

  13. Disruption of Akt signaling decreases dopamine sensitivity in modulation of inhibitory synaptic transmission in rat prefrontal cortex.

    PubMed

    Li, Yan-Chun; Yang, Sha-Sha; Gao, Wen-Jun

    2016-09-01

    Akt is a serine/threonine kinase, which is dramatically reduced in the prefrontal cortex (PFC) of patients with schizophrenia, and a deficiency in Akt1 results in PFC function abnormalities. Although the importance of Akt in dopamine (DA) transmission is well established, how impaired Akt signaling affects the DA modulation of synaptic transmission in the PFC has not been characterized. Here we show that Akt inhibitors significantly decreased receptor sensitivity to DA by shifting DA modulation of GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) in prefrontal cortical neurons. Akt inhibition caused a significant decrease in synaptic dopamine D2 receptor (D2R) levels with high-dose DA exposure. In addition, Akt inhibition failed to affect DA modulation of IPSCs after blockade of β-arrestin 2. β-arrestin 2-mediated interaction of clathrin with D2R was enhanced by co-application of a Akt inhibitor and DA. Taken together, the reduced response in DA modulation of inhibitory transmission mainly involved β-arrestin 2-dependent D2R desensitization. PMID:27163190

  14. Discovery and Development of Small Molecule Allosteric Modulators of Glycoprotein Hormone Receptors

    PubMed Central

    Nataraja, Selvaraj G.; Yu, Henry N.; Palmer, Stephen S.

    2015-01-01

    Glycoprotein hormones, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH) are heterodimeric proteins with a common α-subunit and hormone-specific β-subunit. These hormones are dominant regulators of reproduction and metabolic processes. Receptors for the glycoprotein hormones belong to the family of G protein-coupled receptors. FSH receptor (FSHR) and LH receptor are primarily expressed in somatic cells in ovary and testis to promote egg and sperm production in women and men, respectively. TSH receptor is expressed in thyroid cells and regulates the secretion of T3 and T4. Glycoprotein hormones bind to the large extracellular domain of the receptor and cause a conformational change in the receptor that leads to activation of more than one intracellular signaling pathway. Several small molecules have been described to activate/inhibit glycoprotein hormone receptors through allosteric sites of the receptor. Small molecule allosteric modulators have the potential to be administered orally to patients, thus improving the convenience of treatment. It has been a challenge to develop a small molecule allosteric agonist for glycoprotein hormones that can mimic the agonistic effects of the large natural ligand to activate similar signaling pathways. However, in the past few years, there have been several promising reports describing distinct chemical series with improved potency in preclinical models. In parallel, proposal of new structural model for FSHR and in silico docking studies of small molecule ligands to glycoprotein hormone receptors provide a giant leap on the understanding of the mechanism of action of the natural ligands and new chemical entities on the receptors. This review will focus on the current status of small molecule allosteric modulators of glycoprotein hormone receptors, their effects on common signaling pathways in cells, their utility for clinical application as demonstrated in preclinical models

  15. The apelin receptor inhibits the angiotensin II type 1 receptor via allosteric trans-inhibition

    PubMed Central

    Siddiquee, K; Hampton, J; McAnally, D; May, LT; Smith, LH

    2013-01-01

    Background and Purpose The apelin receptor (APJ) is often co-expressed with the angiotensin II type-1 receptor (AT1) and acts as an endogenous counter-regulator. Apelin antagonizes Ang II signalling, but the precise molecular mechanism has not been elucidated. Understanding this interaction may lead to new therapies for the treatment of cardiovascular disease. Experimental Approach The physical interaction of APJ and AT1 receptors was detected by co-immunoprecipitation and bioluminescence resonance energy transfer (BRET). Functional and pharmacological interactions were measured by G-protein-dependent signalling and recruitment of β-arrestin. Allosterism and cooperativity between APJ and AT1 were measured by radioligand binding assays. Key Results Apelin, but not Ang II, induced APJ : AT1 heterodimerization forced AT1 into a low-affinity state, reducing Ang II binding. Likewise, apelin mediated a concentration-dependent depression in the maximal production of inositol phosphate (IP1) and β-arrestin recruitment to AT1 in response to Ang II. The signal depression approached a limit, the magnitude of which was governed by the cooperativity indicative of a negative allosteric interaction. Fitting the data to an operational model of allosterism revealed that apelin-mediated heterodimerization significantly reduces Ang II signalling efficacy. These effects were not observed in the absence of apelin. Conclusions and Implications Apelin-dependent heterodimerization between APJ and AT1 causes negative allosteric regulation of AT1 function. As AT1 is significant in the pathogenesis of cardiovascular disease, these findings suggest that impaired apelin and APJ function may be a common underlying aetiology. Linked Article This article is commented on by Goupil et al., pp. 1101–1103 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.12040 PMID:22935142

  16. Behavioural innovation and cultural transmission of communication signal in black howler monkeys.

    PubMed

    Briseño-Jaramillo, M; Estrada, A; Lemasson, A

    2015-01-01

    Social traditions based on communication signals are widespread in birds, cetaceans and humans, but surprisingly rare in nonhuman primates known for having genetically-determined vocal repertoires. This study presents the first description of a singular case of behaviour associated with calling (placing a hand in front of the mouth while vocalizing: HFM) in black howler monkeys. We showed, first, that HFM was found only in a subset of the groups observed, at the same geographical location, and was age- and sex-specific. There was an audience effect on HFM, with highest rates when a neighbouring group was visible. HFM was non-randomly combined with audio-visual signals and always performed while roaring. High HFM rates triggered more vocal responses from group members and male neighbours, and HFM signalers temporally synchronized their behaviour in a predictable way. Finally, the positioning of the hand systematically modified the call's auditory structure. Altogether these results support the idea that HFM is an innovated, culturally transmitted communication signal that may play a role in inter-group competition and intra-group cohesion. This study opens new lines of research about how nonhuman primates developed strategies to overcome their constraints in acoustic plasticity very early in the primate lineage. PMID:26303965

  17. Behavioural innovation and cultural transmission of communication signal in black howler monkeys

    PubMed Central

    Briseño-Jaramillo, M.; Estrada, A.; Lemasson, A.

    2015-01-01

    Social traditions based on communication signals are widespread in birds, cetaceans and humans, but surprisingly rare in nonhuman primates known for having genetically-determined vocal repertoires. This study presents the first description of a singular case of behaviour associated with calling (placing a hand in front of the mouth while vocalizing: HFM) in black howler monkeys. We showed, first, that HFM was found only in a subset of the groups observed, at the same geographical location, and was age- and sex-specific. There was an audience effect on HFM, with highest rates when a neighbouring group was visible. HFM was non-randomly combined with audio-visual signals and always performed while roaring. High HFM rates triggered more vocal responses from group members and male neighbours, and HFM signalers temporally synchronized their behaviour in a predictable way. Finally, the positioning of the hand systematically modified the call’s auditory structure. Altogether these results support the idea that HFM is an innovated, culturally transmitted communication signal that may play a role in inter-group competition and intra-group cohesion. This study opens new lines of research about how nonhuman primates developed strategies to overcome their constraints in acoustic plasticity very early in the primate lineage. PMID:26303965

  18. Underwater wireless transmission of high-speed QAM-OFDM signals using a compact red-light laser.

    PubMed

    Xu, Jing; Song, Yuhang; Yu, Xiangyu; Lin, Aobo; Kong, Meiwei; Han, Jun; Deng, Ning

    2016-04-18

    We first study the transmission property of red light in water in terms of extinction coefficient and channel bandwidth via Monte Carlo simulation, with an interesting finding that red light outperforms blue-green light in highly turbid water. We further propose and experimentally demonstrate a broadband underwater wireless optical communication system based on a simple and cost-effective TO56 red-light laser diode. We demonstrate a 1.324-Gb/s transmission at a bit error rate (BER) of 2.02 × 10-3 over a 6-m underwater channel, by using 128-QAM OFDM signals and a low-cost 150-MHz positive-intrinsic-negative photodetector, with a record spectral efficiency higher than 7.32 bits/Hz. By using an avalanche photodetector and 32-QAM OFDM signals, we have achieved a record bit rate of 4.883 Gb/s at a BER of 3.20 × 10-3 over a 6-m underwater channel. PMID:27137249

  19. Root gravitropism: an experimental tool to investigate basic cellular and molecular processes underlying mechanosensing and signal transmission in plants

    NASA Technical Reports Server (NTRS)

    Boonsirichai, K.; Guan, C.; Chen, R.; Masson, P. H.

    2002-01-01

    The ability of plant organs to use gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for gravity sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for gravity sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for gravity perception. Such studies have also allowed the identification of several molecules that appear to function as second messengers in gravity signal transduction and of potential signal transducers. Auxin has been implicated as a probable component of the signal that carries the gravitropic information between the gravity-sensing cap and the gravity-responding EZs. This has allowed the identification and characterization of important molecular processes underlying auxin transport and response in plants. New molecular models can be elaborated to explain how the gravity signal transduction pathway might regulate the polarity of auxin transport in roots. Further studies are required to test these models, as well as to study the molecular mechanisms underlying a poorly characterized phase of gravitropism that is independent of an auxin gradient.

  20. Notch1 Regulates Hippocampal Plasticity Through Interaction with the Reelin Pathway, Glutamatergic Transmission and CREB Signaling

    PubMed Central

    Brai, Emanuele; Marathe, Swananda; Astori, Simone; Fredj, Naila Ben; Perry, Elisabeth; Lamy, Christophe; Scotti, Alessandra; Alberi, Lavinia

    2015-01-01

    Notch signaling plays a crucial role in adult brain function such as synaptic plasticity, memory and olfaction. Several reports suggest an involvement of this pathway in neurodegenerative dementia. Yet, to date, the mechanism underlying Notch activity in mature neurons remains unresolved. In this work, we investigate how Notch regulates synaptic potentiation and contributes to the establishment of memory in mice. We observe that Notch1 is a postsynaptic receptor with functional interactions with the Reelin receptor, apolipoprotein E receptor 2 (ApoER2) and the ionotropic receptor, N-methyl-D-aspartate receptor (NMDAR). Targeted loss of Notch1 in the hippocampal CA fields affects Reelin signaling by influencing Dab1 expression and impairs the synaptic potentiation achieved through Reelin stimulation. Further analysis indicates that loss of Notch1 affects the expression and composition of the NMDAR but not AMPAR. Glutamatergic signaling is further compromised through downregulation of CamKII and its secondary and tertiary messengers resulting in reduced cAMP response element-binding (CREB) signaling. Our results identify Notch1 as an important regulator of mechanisms involved in synaptic plasticity and memory formation. These findings emphasize the possible involvement of this signaling receptor in dementia. Highlights In this paper, we propose a mechanism for Notch1-dependent plasticity that likely underlies the function of Notch1 in memory formation: Notch1 interacts with another important developmental pathway, the Reelin cascade. Notch1 regulates both NMDAR expression and composition. Notch1 influences a cascade of cellular events culminating in CREB activation. PMID:26635527

  1. Investigation of allosteric modulation mechanism of metabotropic glutamate receptor 1 by molecular dynamics simulations, free energy and weak interaction analysis

    PubMed Central

    Bai, Qifeng; Yao, Xiaojun

    2016-01-01

    Metabotropic glutamate receptor 1 (mGlu1), which belongs to class C G protein-coupled receptors (GPCRs), can be coupled with G protein to transfer extracellular signal by dimerization and allosteric regulation. Unraveling the dimer packing and allosteric mechanism can be of great help for understanding specific regulatory mechanism and designing more potential negative allosteric modulator (NAM). Here, we report molecular dynamics simulation studies of the modulation mechanism of FITM on the wild type, T815M and Y805A mutants of mGlu1 through weak interaction analysis and free energy calculation. The weak interaction analysis demonstrates that van der Waals (vdW) and hydrogen bonding play an important role on the dimer packing between six cholesterol molecules and mGlu1 as well as the interaction between allosteric sites T815, Y805 and FITM in wild type, T815M and Y805A mutants of mGlu1. Besides, the results of free energy calculations indicate that secondary binding pocket is mainly formed by the residues Thr748, Cys746, Lys811 and Ser735 except for FITM-bound pocket in crystal structure. Our results can not only reveal the dimer packing and allosteric regulation mechanism, but also can supply useful information for the design of potential NAM of mGlu1. PMID:26887338

  2. Investigation of allosteric modulation mechanism of metabotropic glutamate receptor 1 by molecular dynamics simulations, free energy and weak interaction analysis

    NASA Astrophysics Data System (ADS)

    Bai, Qifeng; Yao, Xiaojun

    2016-02-01

    Metabotropic glutamate receptor 1 (mGlu1), which belongs to class C G protein-coupled receptors (GPCRs), can be coupled with G protein to transfer extracellular signal by dimerization and allosteric regulation. Unraveling the dimer packing and allosteric mechanism can be of great help for understanding specific regulatory mechanism and designing more potential negative allosteric modulator (NAM). Here, we report molecular dynamics simulation studies of the modulation mechanism of FITM on the wild type, T815M and Y805A mutants of mGlu1 through weak interaction analysis and free energy calculation. The weak interaction analysis demonstrates that van der Waals (vdW) and hydrogen bonding play an important role on the dimer packing between six cholesterol molecules and mGlu1 as well as the interaction between allosteric sites T815, Y805 and FITM in wild type, T815M and Y805A mutants of mGlu1. Besides, the results of free energy calculations indicate that secondary binding pocket is mainly formed by the residues Thr748, Cys746, Lys811 and Ser735 except for FITM-bound pocket in crystal structure. Our results can not only reveal the dimer packing and allosteric regulation mechanism, but also can supply useful information for the design of potential NAM of mGlu1.

  3. Discovery, synthesis, and molecular pharmacology of selective positive allosteric modulators of the δ-opioid receptor.

    PubMed

    Burford, Neil T; Livingston, Kathryn E; Canals, Meritxell; Ryan, Molly R; Budenholzer, Lauren M L; Han, Ying; Shang, Yi; Herbst, John J; O'Connell, Jonathan; Banks, Martyn; Zhang, Litao; Filizola, Marta; Bassoni, Daniel L; Wehrman, Tom S; Christopoulos, Arthur; Traynor, John R; Gerritz, Samuel W; Alt, Andrew

    2015-05-28

    Allosteric modulators of G protein-coupled receptors (GPCRs) have a number of potential advantages compared to agonists or antagonists that bind to the orthosteric site of the receptor. These include the potential for receptor selectivity, maintenance of the temporal and spatial fidelity of signaling in vivo, the ceiling effect of the allosteric cooperativity which may prevent overdose issues, and engendering bias by differentially modulating distinct signaling pathways. Here we describe the discovery, synthesis, and molecular pharmacology of δ-opioid receptor-selective positive allosteric modulators (δ PAMs). These δ PAMs increase the affinity and/or efficacy of the orthosteric agonists leu-enkephalin, SNC80 and TAN67, as measured by receptor binding, G protein activation, β-arrestin recruitment, adenylyl cyclase inhibition, and extracellular signal-regulated kinases (ERK) activation. As such, these compounds are useful pharmacological tools to probe the molecular pharmacology of the δ receptor and to explore the therapeutic potential of δ PAMs in diseases such as chronic pain and depression. PMID:25901762

  4. Multiple allosteric sites on muscarinic receptors.

    PubMed

    Birdsall, N J; Lazareno, S; Popham, A; Saldanha, J

    2001-04-27

    Proteins and small molecules are capable of regulating the agonist binding and function of G-protein coupled receptors by multiple allosteric mechanisms. In the case of muscarinic receptors, there is the well-characterised allosteric site that binds, for example, gallamine and brucine. The protein kinase inhibitor, KT5720, has now been shown to bind to a second allosteric site and to regulate agonist and antagonist binding. The binding of brucine and gallamine does not affect KT5720 binding nor its effects on the dissociation of [3H]-N-methylscopolamine from M1 receptors. Therefore it is possible to have a muscarinic receptor with three small ligands bound simultaneously. A model of the M1 receptor, based on the recently determined structure of rhodopsin, has the residues that have been shown to be important for gallamine binding clustered within and to one side of a cleft in the extracellular face of the receptor. This cleft may represent the access route of acetylcholine to its binding site. PMID:11392621

  5. Exploiting protein flexibility to predict the location of allosteric sites

    PubMed Central

    2012-01-01

    Background Allostery is one of the most powerful and common ways of regulation of protein activity. However, for most allosteric proteins identified to date the mechanistic details of allosteric modulation are not yet well understood. Uncovering common mechanistic patterns underlying allostery would allow not only a better academic understanding of the phenomena, but it would also streamline the design of novel therapeutic solutions. This relatively unexplored therapeutic potential and the putative advantages of allosteric drugs over classical active-site inhibitors fuel the attention allosteric-drug research is receiving at present. A first step to harness the regulatory potential and versatility of allosteric sites, in the context of drug-discovery and design, would be to detect or predict their presence and location. In this article, we describe a simple computational approach, based on the effect allosteric ligands exert on protein flexibility upon binding, to predict the existence and position of allosteric sites on a given protein structure. Results By querying the literature and a recently available database of allosteric sites, we gathered 213 allosteric proteins with structural information that we further filtered into a non-redundant set of 91 proteins. We performed normal-mode analysis and observed significant changes in protein flexibility upon allosteric-ligand binding in 70% of the cases. These results agree with the current view that allosteric mechanisms are in many cases governed by changes in protein dynamics caused by ligand binding. Furthermore, we implemented an approach that achieves 65% positive predictive value in identifying allosteric sites within the set of predicted cavities of a protein (stricter parameters set, 0.22 sensitivity), by combining the current analysis on dynamics with previous results on structural conservation of allosteric sites. We also analyzed four biological examples in detail, revealing that this simple coarse

  6. N-Aryl Piperazine Metabotropic Glutamate Receptor 5 Positive Allosteric Modulators Possess Efficacy in Preclinical Models of NMDA Hypofunction and Cognitive Enhancement

    PubMed Central

    Gregory, K.J.; Herman, E.J.; Ramsey, A.J.; Hammond, A.S.; Byun, N.E.; Stauffer, S.R.; Manka, J.T.; Jadhav, S.; Bridges, T.M.; Weaver, C.D.; Niswender, C.M.; Steckler, T.; Drinkenburg, W.H.; Ahnaou, A.; Lavreysen, H.; Macdonald, G.J.; Bartolomé, J.M.; Mackie, C.; Hrupka, B.J.; Caron, M.G.; Daigle, T.L.; Lindsley, C.W.; Conn, P.J.

    2013-01-01

    Impaired transmission through glutamatergic circuits has been postulated to play a role in the underlying pathophysiology of schizophrenia. Furthermore, inhibition of the N-methyl-d-aspartate (NMDA) subtype of ionotropic glutamate receptors (NMDAR) induces a syndrome that recapitulates many of the symptoms observed in patients with schizophrenia. Selective activation of metabotropic glutamate receptor subtype 5 (mGlu5) may provide a novel therapeutic approach for treatment of symptoms associated with schizophrenia through facilitation of transmission through central glutamatergic circuits. Here, we describe the characterization of two novel N-aryl piperazine mGlu5 positive allosteric modulators (PAMs): 2-(4-(2-(benzyloxy)acetyl)piperazin-1-yl)benzonitrile (VU0364289) and 1-(4-(2,4-difluorophenyl)piperazin-1-yl)-2-((4-fluorobenzyl)oxy)ethanone (DPFE). VU0364289 and DPFE induced robust leftward shifts in the glutamate concentration-response curves for Ca2+ mobilization and extracellular signal-regulated kinases 1 and 2 phosphorylation. Both PAMs displayed micromolar affinity for the common mGlu5 allosteric binding site and high selectivity for mGlu5. VU0364289 and DPFE possessed suitable pharmacokinetic properties for dosing in vivo and produced robust dose-related effects in reversing amphetamine-induced hyperlocomotion, a preclinical model predictive of antipsychotic-like activity. In addition, DPFE enhanced acquisition of contextual fear conditioning in rats and reversed behavioral deficits in a mouse model of NMDAR hypofunction. In contrast, DPFE had no effect on reversing apomorphine-induced disruptions of prepulse inhibition of the acoustic startle reflex. These mGlu5 PAMs also increased monoamine levels in the prefrontal cortex, enhanced performance in a hippocampal-mediated memory task, and elicited changes in electroencephalogram dynamics commensurate with procognitive effects. Collectively, these data support and extend the role for the development of novel

  7. [Neuromuscular signal transmission in adulthood. Current facets of acquired and hereditary disorders].

    PubMed

    Abicht, A; Kröger, S; Schoser, B

    2011-06-01

    The availability of early diagnosis and modern effective therapies has reduced mortality and disability linked to late-onset acquired or hereditary neuromuscular transmission disorders. Nevertheless, identification of the pathogenesis of these diseases remains a challenge. In addition to non-specific and fluctuating presenting symptoms current diagnostic work-up strategies include electrophysiology, antibody measurements and less frequently molecular genetics. For differential diagnostic purposes there is an increasing demand for improving awareness concerning late-onset congenital myasthenic syndromes (CMS) which are rare but nevertheless symptomatically treatable diseases. Especially in seronegative myasthenic syndromes, molecular genetic analyses of CMS genes should be integrated into the differential diagnostic work-up. Therefore, some facets of neuromuscular synaptogenesis in the context of seronegative acquired myasthenic syndromes and recently uncovered congenital myasthenic syndromes are reviewed. PMID:21584790

  8. The neurotoxic effects of N-methyl-N-nitrosourea on the electrophysiological property and visual signal transmission of rat's retina

    SciTech Connect

    Tao, Ye; Chen, Tao; Liu, Bei; Yang, Guo Qing; Peng, Guanghua; Zhang, Hua; Huang, Yi Fei

    2015-07-01

    The neurotoxic effects of N-methyl-N-nitrosourea (MNU) on the inner retinal neurons and related visual signal circuits have not been described in any animal models or human, despite ample morphological evidences about the MNU induced photoreceptor (PR) degeneration. With the helping of MEA (multielectrode array) recording system, we gained the opportunity to systemically explore the neural activities and visual signal pathways of MNU administrated rats. Our MEA research identified remarkable alterations in the electrophysiological properties and firstly provided instructive information about the neurotoxicity of MNU that affects the signal transmission in the inner retina. Moreover, the spatial electrophysiological functions of retina were monitored and found that the focal PRs had different vulnerabilities to the MNU. The MNU-induced PR dysfunction exhibited a distinct spatial- and time-dependent progression. In contrast, the spiking activities of both central and peripheral RGCs altered synchronously in response to the MNU administration. Pharmacological tests suggested that gap junctions played a pivotal role in this homogeneous response of RGCs. SNR analysis of MNU treated retina suggested that the signaling efficiency and fidelity of inner retinal circuits have been ruined by this toxicant, although the microstructure of the inner retina seemed relatively consolidated. The present study provided an appropriate example of MEA investigations on the toxicant induced pathological models and the effects of the pharmacological compounds on neuron activities. The positional MEA information would enrich our knowledge about the pathology of MNU induced RP models, and eventually be instrumental for elucidating the underlying mechanism of human RP. - Highlights: • We systemically explored the neural activities and visual signal pathways of MNU administrated retinas. • The focal photoreceptors had different vulnerabilities to the MNU administration.

  9. 110 km transmission of 160 Gbit/s RZ-DQPSK signals by midspan polarization-insensitive optical phase conjugation in a Ti:PPLN waveguide.

    PubMed

    Hu, Hao; Nouroozi, Rahman; Ludwig, Reinhold; Schmidt-Langhorst, Carsten; Suche, Hubertus; Sohler, Wolfgang; Schubert, Colja

    2010-09-01

    We demonstrate 160 Gbit/s return-to-zero (RZ) differential quarternary phase-shift keying (DQPSK) signal transmission over a 110 km single-mode fiber by taking advantage of mid-span optical phase conjugation (OPC). The technique is based on nonlinear wavelength conversion by cascaded second harmonic and difference frequency generation in a Ti:PPLN waveguide. Error-free operation with a negligible optical signal-to-noise ratio penalty for the signal after the OPC transmission without and with polarization scrambling was achieved. The results also show the polarization insensitivity of the OPC system using a polarization diversity scheme. PMID:20808351

  10. Optical phase conjugation by an As(2)S(3) glass planar waveguide for dispersion-free transmission of WDM-DPSK signals over fiber.

    PubMed

    Pelusi, M D; Luan, F; Choi, D-Y; Madden, S J; Bulla, D A P; Luther-Davies, B; Eggleton, B J

    2010-12-01

    We report the first demonstration of optical phase conjugation (OPC) transmission of phase encoded and wavelength-division multiplexed (WDM) signals by the Kerr effect in a planar structured waveguide. The phase conjugated electric field of the signal is produced by four wave mixing pumped by a CW laser during co-propagating with the signal in a highly nonlinear waveguide fabricated in As(2)S(3) glass. Experiments demonstrate the capability of the device to perform dispersion-free transmission through up to 225 km of standard single mode fiber for a 3 × 40 Gb/s WDM signal, with its channels encoded as return-to-zero differential phase shift keying and spaced either 100 or 200 GHz apart. This work represents an important milestone towards demonstrating advanced signal processing of high-speed and broadband optical signals in compact planar waveguides, with the potential for monolithic optical integration. PMID:21165019

  11. Using Pulse Width Modulation for Wireless Transmission of Neural Signals in Multichannel Neural Recording Systems

    PubMed Central

    Yin, Ming; Ghovanloo, Maysam

    2013-01-01

    We have used a well-known technique in wireless communication, pulse width modulation (PWM) of time division multiplexed (TDM) signals, within the architecture of a novel wireless integrated neural recording (WINeR) system. We have evaluated the performance of the PWM-based architecture and indicated its accuracy and potential sources of error through detailed theoretical analysis, simulations, and measurements on a setup consisting of a 15-channel WINeR prototype as the transmitter and two types of receivers; an Agilent 89600 vector signal analyzer and a custom wideband receiver, with 36 and 75 MHz of maximum bandwidth, respectively. Furthermore, we present simulation results from a realistic MATLAB-Simulink model of the entire WINeR system to observe the system behavior in response to changes in various parameters. We have concluded that the 15-ch WINeR prototype, which is fabricated in a 0.5-μm standard CMOS process and consumes 4.5 mW from ±1.5 V supplies, can acquire and wirelessly transmit up to 320 k-samples/s to a 75-MHz receiver with 8.4 bits of resolution, which is equivalent to a wireless data rate of ~ 2.26 Mb/s. PMID:19497823

  12. Using pulse width modulation for wireless transmission of neural signals in multichannel neural recording systems.

    PubMed

    Yin, Ming; Ghovanloo, Maysam

    2009-08-01

    We have used a well-known technique in wireless communication, pulse width modulation (PWM) of time division multiplexed (TDM) signals, within the architecture of a novel wireless integrated neural recording (WINeR) system. We have evaluated the performance of the PWM-based architecture and indicated its accuracy and potential sources of error through detailed theoretical analysis, simulations, and measurements on a setup consisting of a 15-channel WINeR prototype as the transmitter and two types of receivers; an Agilent 89600 vector signal analyzer and a custom wideband receiver, with 36 and 75 MHz of maximum bandwidth, respectively. Furthermore, we present simulation results from a realistic MATLAB-Simulink model of the entire WINeR system to observe the system behavior in response to changes in various parameters. We have concluded that the 15-ch WINeR prototype, which is fabricated in a 0.5- mum standard CMOS process and consumes 4.5 mW from +/-1.5 V supplies, can acquire and wirelessly transmit up to 320 k-samples/s to a 75-MHz receiver with 8.4 bits of resolution, which is equivalent to a wireless data rate of approximately 2.56 Mb/s. PMID:19497823

  13. Transmission of a signal that synchronizes cell movements in swarms of Myxococcus xanthus

    PubMed Central

    Kaiser, Dale; Warrick, Hans

    2014-01-01

    We offer evidence for a signal that synchronizes the behavior of hundreds of Myxococcus xanthus cells in a growing swarm. Swarms are driven to expand by the periodic reversing of direction by members. By using time-lapse photomicroscopy, two organized multicellular elements of the swarm were analyzed: single-layered, rectangular rafts and round, multilayered mounds. Rafts of hundreds of cells with their long axes aligned in parallel enlarge as individual cells from the neighborhood join them from either side. Rafts can also add a second layer piece by piece. By repeating layer additions to a raft and rounding each layer, a regular multilayered mound can be formed. About an hour after a five-layered mound had formed, all of the cells from its top layer descended to the periphery of the fourth layer, both rapidly and synchronously. Following the first synchronized descent and spaced at constant time intervals, a new fifth layer was (re)constructed from fourth-layer cells, in very close proximity to its old position and with a number of cells similar to that before the “explosive” descent. This unexpected series of changes in mound structure can be explained by the spread of a signal that synchronizes the reversals of large groups of individual cells. PMID:25149859

  14. Depletion of calcium stores regulates calcium influx and signal transmission in rod photoreceptors

    PubMed Central

    Szikra, Tamas; Cusato, Karen; Thoreson, Wallace B; Barabas, Peter; Bartoletti, Theodore M; Krizaj, David

    2008-01-01

    Tonic synapses are specialized for sustained calcium entry and transmitter release, allowing them to operate in a graded fashion over a wide dynamic range. We identified a novel plasma membrane calcium entry mechanism that extends the range of rod photoreceptor signalling into light-adapted conditions. The mechanism, which shares molecular and physiological characteristics with store-operated calcium entry (SOCE), is required to maintain baseline [Ca2+]i in rod inner segments and synaptic terminals. Sustained Ca2+ entry into rod cytosol is augmented by store depletion, blocked by La3+ and Gd3+ and suppressed by organic antagonists MRS-1845 and SKF-96365. Store depletion and the subsequent Ca2+ influx directly stimulated exocytosis in terminals of light-adapted rods loaded with the activity-dependent dye FM1–43. Moreover, SOCE blockers suppressed rod-mediated synaptic inputs to horizontal cells without affecting presynaptic voltage-operated Ca2+ entry. Silencing of TRPC1 expression with small interference RNA disrupted SOCE in rods, but had no effect on cone Ca2+ signalling. Rods were immunopositive for TRPC1 whereas cone inner segments immunostained with TRPC6 channel antibodies. Thus, SOCE modulates Ca2+ homeostasis and light-evoked neurotransmission at the rod photoreceptor synapse mediated by TRPC1. PMID:18755743

  15. Ionospheric ELF radio signal generation due to LF and/or MF radio transmissions. II - Interpretation

    NASA Astrophysics Data System (ADS)

    Cannon, P. S.; Turunen, T.; Rycroft, M. J.

    1982-10-01

    Four possible mechanisms are considered for the generation of the ELF pips reported by Cannon (1982). The mechanisms involve the heating of the auroral D region or lower E region by AM waves from one or more distant Soviet LF and/or MF radio transmitters, leading to modulation of the large electrojet current, which then radiates at 1 kHz. It is shown that the experimental data favor a mechanism entailing periodic in-phase heating of the ionosphere by two or more synchronized transmitters and that the most likely solutions involve transmissions at 173, 263, 281, and 549 kHz. A 0.6-K peak-to-peak sinusoidal electron-temperature variation superimposed on a 2-K temperature rise is predicted for the combined effect of transmitters in Kaliningrad (173 kHz), Moscow (173 and 263 kHz), and Minsk (281 and 549 kHz). The corresponding 1-kHz magnetic field variations on the ground directly below the source are estimated to be 0.09 pT, in good agreement with the experimental ELF pip field strengths.

  16. GPCR heteromers and their allosteric receptor-receptor interactions.

    PubMed

    Fuxe, K; Borroto-Escuela, D O; Marcellino, D; Romero-Fernandez, W; Frankowska, M; Guidolin, D; Filip, M; Ferraro, L; Woods, A S; Tarakanov, A; Ciruela, F; Agnati, L F; Tanganelli, S

    2012-01-01

    The concept of intramembrane receptor-receptor interactions and evidence for their existences were introduced in the beginning of the 1980's, suggesting the existence of receptor heterodimerization. The discovery of GPCR heteromers and the receptor mosaic (higher order oligomers, more than two) has been related to the parallel development and application of a variety of resonance energy transfer techniques such as bioluminescence (BRET), fluorescence (FRET) and sequential energy transfer (SRET). The assembly of interacting GPCRs, heterodimers and receptor mosaic leads to changes in the agonist recognition, signaling, and trafficking of participating receptors via allosteric mechanisms, sometimes involving the appearance of cooperativity. The receptor interface in the GPCR heteromers is beginning to be characterized and the key role of electrostatic epitope-epitope interactions for the formation of the receptor heteromers will be discussed. Furthermore, a "guide-and-clasp" manner of receptor-receptor interactions has been proposed where the "adhesive guides" may be the triplet homologies. These interactions probably represent a general molecular mechanism for receptor-receptor interactions. It is proposed that changes in GPCR function (moonlighting) may develop through the intracellular loops and C-terminii of the GPCR heteromers as a result of dynamic allosteric interactions between different types of G proteins and other receptor interacting proteins in these domains of the receptors. The evidence for the existence of receptor heteromers opens up a new field for a better understanding of neurophysiology and neuropathology. Furthermore, novel therapeutic approaches could be possible based on the use of heteromers as targets for drug development based on their unique pharmacology. PMID:22335512

  17. Collective retention and transmission of chemical signals in a social insect

    NASA Astrophysics Data System (ADS)

    Gill, Katherine P.; van Wilgenburg, Ellen; Taylor, Peter; Elgar, Mark A.

    2012-03-01

    Social insect colonies exhibit highly coordinated responses to ecological challenges by acquiring information that is disseminated throughout the colony. Some responses are coordinated directly from the signals produced by individuals that acquired the information. Other responses may require information to be transferred indirectly through a third party, thereby requiring colony-wide retention of information. Social insects use colony signature odours to distinguish between nestmates and non-nestmates, and the level of aggression between non-nestmates typically varies according to the distance between colonies and thus their history of interactions. Such coordinated, colony-specific responses may require information about particular odours to be disseminated and retained across the colony. Our field experiments with weaver ants reveal colony-wide, indirect acquisition and retention of the signature odours of a different colony with which they had experienced aggression. These data highlight the significance of interaction history and suggest the presence of a collective memory.

  18. Digital signal processing approaches for semiconductor phase noise tolerant coherent transmission systems

    NASA Astrophysics Data System (ADS)

    Iglesias Olmedo, Miguel; Pang, Xiaodan; Schatz, Richard; Zibar, Darko; Tafur Monroy, Idelfonso; Jacobsen, Gunnar; Popov, Sergei

    2015-01-01

    We discuss about digital signal processing approaches that can enable coherent links based on semiconductor lasers. A state-of-the art analysis on different carrier-phase recovery (CPR) techniques is presented. We show that these techniques are based on the assumption of lorentzian linewidth, which does not hold for monolithically integrated semiconductor lasers. We investigate the impact of such lineshape on both 3 and 20 dB linewidth and experimentally conduct a systematic study for 56-GBaud DP-QPSK and 28-GBaud DP-16QAM systems using a decision directed phase look loop algorithm. We show how carrier induced frequency noise has no impact on linewidth but a significant impact on system performance; which rises the question on whether 3-dB linewidth should be used as performance estimator for semiconductor lasers.

  19. Transmission of wireless neural signals through a 0.18 µm CMOS low-power amplifier.

    PubMed

    Gazziro, M; Braga, C F R; Moreira, D A; Carvalho, A C P L F; Rodrigues, J F; Navarro, J S; Ardila, J C M; Mioni, D P; Pessatti, M; Fabbro, P; Freewin, C; Saddow, S E

    2015-01-01

    In the field of Brain Machine Interfaces (BMI) researchers still are not able to produce clinically viable solutions that meet the requirements of long-term operation without the use of wires or batteries. Another problem is neural compatibility with the electrode probes. One of the possible ways of approaching these problems is the use of semiconductor biocompatible materials (silicon carbide) combined with an integrated circuit designed to operate with low power consumption. This paper describes a low-power neural signal amplifier chip, named Cortex, fabricated using 0.18 μm CMOS process technology with all electronics integrated in an area of 0.40 mm(2). The chip has 4 channels, total power consumption of only 144 μW, and is impedance matched to silicon carbide biocompatible electrodes. PMID:26737437

  20. OAM multiple transmission using uniform circular arrays: Numerical modeling and experimental verification with two digital television signals

    NASA Astrophysics Data System (ADS)

    Gaffoglio, Rossella; Cagliero, Andrea; Vita, Assunta De; Sacco, Bruno

    2016-06-01

    In this work we present the outcomes of a radio frequency orbital angular momentum (OAM) transmission between two antenna arrays performed in a real-world context. The analysis is supplemented by deep simulative investigations able to provide both a preliminary overview of the experimental scenario and a posteriori validation of the achieved results. As a first step, the far-field OAM communication link is tested at various frequencies and the corresponding link budget is studied by means of an angular scan generated by the rotation of the receiving system. Then, on the same site, two digital television signals encoded as OAM modes (ℓ = 1 and ℓ =- 1) are simultaneously transmitted at a common frequency of 198.5 MHz with good mode insulation.

  1. A conserved activation cluster is required for allosteric communication in HtrA-family proteases.

    PubMed

    de Regt, Anna K; Kim, Seokhee; Sohn, Jungsan; Grant, Robert A; Baker, Tania A; Sauer, Robert T

    2015-03-01

    In E. coli, outer-membrane stress causes a transcriptional response through a signaling cascade initiated by DegS cleavage of a transmembrane antisigma factor. Each subunit of DegS, an HtrA-family protease, contains a protease domain and a PDZ domain. The trimeric protease domain is autoinhibited by the unliganded PDZ domains. Allosteric activation requires binding of unassembled outer-membrane proteins (OMPs) to the PDZ domains and protein substrate binding. Here, we identify a set of DegS residues that cluster together at subunit-subunit interfaces in the trimer, link the active sites and substrate binding sites, and are crucial for stabilizing the active enzyme conformation in response to OMP signaling. These residues are conserved across the HtrA-protease family, including orthologs linked to human disease, supporting a common mechanism of allosteric activation. Indeed, mutation of residues at homologous positions in the DegP quality-control protease also eliminates allosteric activation. PMID:25703375

  2. The nicotinic acetylcholine receptor and its prokaryotic homologues: Structure, conformational transitions & allosteric modulation.

    PubMed

    Cecchini, Marco; Changeux, Jean-Pierre

    2015-09-01

    Pentameric ligand-gated ion channels (pLGICs) play a central role in intercellular communications in the nervous system by converting the binding of a chemical messenger - a neurotransmitter - into an ion flux through the postsynaptic membrane. Here, we present an overview of the most recent advances on the signal transduction mechanism boosted by X-ray crystallography of both prokaryotic and eukaryotic homologues of the nicotinic acetylcholine receptor (nAChR) in conjunction with time-resolved analyses based on single-channel electrophysiology and Molecular Dynamics simulations. The available data consistently point to a global mechanism of gating that involves a large reorganization of the receptor mediated by two distinct quaternary transitions: a global twisting and a radial expansion/contraction of the extracellular domain. These transitions profoundly modify the organization of the interface between subunits, which host several sites for orthosteric and allosteric modulatory ligands. The same mechanism may thus mediate both positive and negative allosteric modulations of pLGICs ligand binding at topographically distinct sites. The emerging picture of signal transduction is expected to pave the way to new pharmacological strategies for the development of allosteric modulators of nAChR and pLGICs in general. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'. PMID:25529272

  3. Transmissive grating-reflective mirror-based fiber optic accelerometer for stable signal acquisition in industrial applications

    NASA Astrophysics Data System (ADS)

    Lee, Yeon-Gwan; Kim, Dae-Hyun; Kim, Chun-Gon

    2012-05-01

    This paper discusses an applicable fiber-optic accelerometer composed of a transmissive grating panel, a reflection mirror, and two optical fibers with a separation of quarter grating pitch as transceivers that monitor the low-frequency accelerations of civil engineering structures. This sensor structure brings together the advantages of both a simple sensor structure, which leads to simplified cable design by 50% in comparison with the conventional transmission-type fiber optic accelerometer, and a stable reflected signals acquisition with repeatability in comparison to the researched grating-reflection type fiber optic accelerometer. The vibrating displacement and sinusoidal acceleration measured from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and a MEMS accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4.0 Hz with a margin of error that is less than 5% and a high sensitivity of 5.06 rad/(m/s)2.

  4. Heterodyne detection and transmission of 60-Gbaud PDM-QPSK signal with SE of 4b/s/Hz.

    PubMed

    Li, Xinying; Xiao, Jiangnan; Yu, Jianjun

    2014-04-21

    We experimentally demonstrate 8 × 240-Gb/s super-Nyquist wavelength-division-multiplexing (WDM) polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal transmission on a 50-GHz grid with a net spectral efficiency (SE) of 4b/s/Hz adopting hardware-efficient simplified heterodyne detection. 9-ary quadrature-amplitude-modulation-like (9QAM-like) processing based on multi-modulus blind equalization (MMBE) is adopted to reduce analog-to-digital converter (ADC) bandwidth requirement and improve receiver sensitivity. The transmission distance at the soft-decision forward-error-correction (SD-FEC) threshold of 2 × 10(-2) is 2 × 420 km based on digital post filtering while largely extended to over 5 × 420 km based on 9QAM-like processing, which well illustrates 9QAM-like processing is more efficient for heterodyne coherent WDM system. Moreover, only two ADC channels are needed for simplified heterodyne detection of one 60-Gbaud PDM-QPSK WDM channel, and thus only one commercial oscilloscope (OSC) with two input ports can work well for each WDM channel. PMID:24787819

  5. Diffusible signal factor-repressed extracellular traits enable attachment of Xylella fastidiosa to insect vectors and transmission.

    PubMed

    Baccari, Clelia; Killiny, Nabil; Ionescu, Michael; Almeida, Rodrigo P P; Lindow, Steven E

    2014-01-01

    The hypothesis that a wild-type strain of Xylella fastidiosa would restore the ability of rpfF mutants blocked in diffusible signal factor production to be transmitted to new grape plants by the sharpshooter vector Graphocephala atropunctata was tested. While the rpfF mutant was very poorly transmitted by vectors irrespective of whether they had also fed on plants infected with the wild-type strain, wild-type strains were not efficiently transmitted if vectors had fed on plants infected with the rpfF mutant. About 100-fewer cells of a wild-type strain attached to wings of a vector when suspended in xylem sap from plants infected with an rpfF mutant than in sap from uninfected grapes. The frequency of transmission of cells suspended in sap from plants that were infected by the rpfF mutant was also reduced over threefold. Wild-type cells suspended in a culture supernatant of an rpfF mutant also exhibited 10-fold less adherence to wings than when suspended in uninoculated culture media. A factor released into the xylem by rpfF mutants, and to a lesser extent by the wild-type strain, thus inhibits their attachment to, and thus transmission by, sharpshooter vectors and may also enable them to move more readily through host plants. PMID:24571393

  6. Transmission of 40-Gb/s QPSK upstream signal in RSOA-based coherent WDM PON using offset PDM technique.

    PubMed

    Shim, H K; Cho, K Y; Hong, U H; Chung, Y C

    2013-02-11

    We demonstrate the 40-Gb/s upstream transmission in the 60-km reach wavelength-division-multiplexed passive optical network (WDM PON) implemented by using directly modulated reflective semiconductor optical amplifiers (RSOAs) and self-homodyne receivers. It is difficult to operate the RSOA at 40 Gb/s due to its limited modulation bandwidth. To overcome this problem and generate 40-Gb/s upstream signal, we utilize the quadrature phase-shift-keying (QPSK) format and the offset polarization-division-multiplexing (PDM) technique. For this purpose, we install two RSOAs at each ONU and provide the seed light for these RSOAs by polarization-multiplexing the outputs of two lasers with a small frequency offset (20 GHz). This frequency offset is used to separate the polarization-multiplexed seed light by using a simple delay-line interferometer (DLI), instead of the polarization-beam splitter and polarization controller, at the ONU. The separated seed light is modulated by each RSOA at 20 Gb/s in the QPSK format, and then combined again by the DLI before sent back to the central office (CO). The results show that this WDM PON can support the transmission of 40-Gb/s channels spaced at 50 GHz over 60 km without using any remote optical amplifiers. PMID:23481828

  7. The lactose repressor system: paradigms for regulation, allosteric behavior and protein folding.

    PubMed

    Wilson, C J; Zhan, H; Swint-Kruse, L; Matthews, K S

    2007-01-01

    In 1961, Jacob and Monod proposed the operon model for gene regulation based on metabolism of lactose in Escherichia coli. This proposal was followed by an explication of allosteric behavior by Monod and colleagues. The operon model rationally depicted how genetic mechanisms can control metabolic events in response to environmental stimuli via coordinated transcription of a set of genes with related function (e.g. metabolism of lactose). The allosteric response found in the lactose repressor and many other proteins has been extended to a variety of cellular signaling pathways in all organisms. These two models have shaped our view of modern molecular biology and captivated the attention of a surprisingly broad range of scientists. More recently, the lactose repressor monomer was used as a model system for experimental and theoretical explorations of protein folding mechanisms. Thus, the lac system continues to advance our molecular understanding of genetic control and the relationship between sequence, structure and function. PMID:17103112

  8. In vivo structure-activity relationship studies support allosteric targeting of a dual specificity phosphatase.

    PubMed

    Korotchenko, Vasiliy N; Saydmohammed, Manush; Vollmer, Laura L; Bakan, Ahmet; Sheetz, Kyle; Debiec, Karl T; Greene, Kristina A; Agliori, Christine S; Bahar, Ivet; Day, Billy W; Vogt, Andreas; Tsang, Michael

    2014-07-01

    Dual specificity phosphatase 6 (DUSP6) functions as a feedback attenuator of fibroblast growth factor signaling during development. In vitro high throughput chemical screening attempts to discover DUSP6 inhibitors have yielded limited success. However, in vivo whole-organism screens of zebrafish identified compound 1 (BCI) as an allosteric inhibitor of DUSP6. Here we designed and synthesized a panel of analogues to define the structure-activity relationship (SAR) of DUSP6 inhibition. In vivo high-content analysis in transgenic zebrafish, coupled with cell-based chemical complementation assays, identified structural features of the pharmacophore of 1 that were essential for biological activity. In vitro assays of DUSP hyperactivation corroborated the results from in vivo and cellular SAR. The results reinforce the notion that DUSPs are druggable through allosteric mechanisms and illustrate the utility of zebrafish as a model organism for in vivo SAR analyses. PMID:24909879

  9. Neurobiological Insights from mGlu Receptor Allosteric Modulation

    PubMed Central

    O’Brien, Daniel E

    2016-01-01

    Allosteric modulation of metabotropic glutamate (mGlu) receptors offers a promising pharmacological approach to normalize neural circuit dysfunction associated with various psychiatric and neurological disorders. As mGlu receptor allosteric modulators progress through discovery and clinical development, both technical advances and novel tool compounds are providing opportunities to better understand mGlu receptor pharmacology and neurobiology. Recent advances in structural biology are elucidating the structural determinants of mGlu receptor–negative allosteric modulation and supplying the means to resolve active, allosteric modulator-bound mGlu receptors. The discovery and characterization of allosteric modulators with novel pharmacological profiles is uncovering the biological significance of their intrinsic agonist activity, biased mGlu receptor modulation, and novel mGlu receptor heterodimers. The development and exploitation of optogenetic and optopharmacological tools is permitting a refined spatial and temporal understanding of both mGlu receptor functions and their allosteric modulation in intact brain circuits. Together, these lines of research promise to provide a more refined understanding of mGlu receptors and their allosteric modulation that will inform the development of mGlu receptor allosteric modulators as neurotherapeutics in the years to come. PMID:26647381

  10. Transmission and full-band coherent detection of polarization-multiplexed all-optical Nyquist signals generated by Sinc-shaped Nyquist pulses.

    PubMed

    Zhang, Junwen; Yu, Jianjun; Chi, Nan

    2015-01-01

    All optical method is considered as a promising technique for high symbol rate Nyquist signal generation, which has attracted a lot of research interests for high spectral-efficiency and high-capacity optical communication system. In this paper, we extend our previous work and report the fully experimental demonstration of polarization-division multiplexed (PDM) all-optical Nyquist signal generation based on Sinc-shaped Nyquist pulse with advanced modulation formats, fiber-transmission and single-receiver full-band coherent detection. Using this scheme, we have successfully demonstrated the generation, fiber transmission and single-receiver full-band coherent detection of all-optical Nyquist PDM-QPSK and PDM-16QAM signals up to 125-GBaud. 1-Tb/s single-carrier PDM-16QAM signal generation and full-band coherent detection is realized, which shows the advantage and feasibility of the single-carrier all-optical Nyquist signals. PMID:26323238

  11. Transmission and full-band coherent detection of polarization-multiplexed all-optical Nyquist signals generated by Sinc-shaped Nyquist pulses

    PubMed Central

    Zhang, Junwen; Yu, Jianjun; Chi, Nan

    2015-01-01

    All optical method is considered as a promising technique for high symbol rate Nyquist signal generation, which has attracted a lot of research interests for high spectral-efficiency and high-capacity optical communication system. In this paper, we extend our previous work and report the fully experimental demonstration of polarization-division multiplexed (PDM) all-optical Nyquist signal generation based on Sinc-shaped Nyquist pulse with advanced modulation formats, fiber-transmission and single-receiver full-band coherent detection. Using this scheme, we have successfully demonstrated the generation, fiber transmission and single-receiver full-band coherent detection of all-optical Nyquist PDM-QPSK and PDM-16QAM signals up to 125-GBaud. 1-Tb/s single-carrier PDM-16QAM signal generation and full-band coherent detection is realized, which shows the advantage and feasibility of the single-carrier all-optical Nyquist signals. PMID:26323238

  12. Transmission and full-band coherent detection of polarization-multiplexed all-optical Nyquist signals generated by Sinc-shaped Nyquist pulses

    NASA Astrophysics Data System (ADS)

    Zhang, Junwen; Yu, Jianjun; Chi, Nan

    2015-09-01

    All optical method is considered as a promising technique for high symbol rate Nyquist signal generation, which has attracted a lot of research interests for high spectral-efficiency and high-capacity optical communication system. In this paper, we extend our previous work and report the fully experimental demonstration of polarization-division multiplexed (PDM) all-optical Nyquist signal generation based on Sinc-shaped Nyquist pulse with advanced modulation formats, fiber-transmission and single-receiver full-band coherent detection. Using this scheme, we have successfully demonstrated the generation, fiber transmission and single-receiver full-band coherent detection of all-optical Nyquist PDM-QPSK and PDM-16QAM signals up to 125-GBaud. 1-Tb/s single-carrier PDM-16QAM signal generation and full-band coherent detection is realized, which shows the advantage and feasibility of the single-carrier all-optical Nyquist signals.

  13. Noise-driven signal transmission device using molecular dynamics of organic polymers

    NASA Astrophysics Data System (ADS)

    Asakawa, Naoki; Umemura, Koichiro; Fujise, Shinya; Yazawa, Koji; Shimizu, Tadashi; Tansho, Masataka; Kanki, Teruo; Tanaka, Hidekazu

    2014-01-01

    Stochastic threshold devices using a trap-filling transition (TFT) coupled with molecular dynamics in poly(3-alkylthiophene)s were fabricated as potential key devices for noise-driven bioinspired sensors and information processors. This article deals with variable-temperature direct current conductivity and alternating current impedance measurements for vertical-type device elements of Au/regioregular poly(3-decylthiophene) ((RR-P3DT) (thickness: 100 nm)/Au, which show multiple conducting states and quasi-stochastic transitions between these states. Noise measurements indicate the ω-2-type (if VVTFT) power spectral densities, where V and VTFT are an applied voltage and the voltage for TFT, respectively. The noise generation is due to the TFT associated with twist dynamics of π-conjugated polymers near the order-disorder phase transition (ODT). At 298 K, the quasi-stochastic behavior is more noticeable for RR-P3DT than poly(3-hexylthiophene). The quasi-stochastic property is employed to a stochastic one-directional signal transmitting device using optical-electric conversion. The dynamics of ODT for powder samples were also investigated by differential scanning calorimetry measurements and high-resolution solid-state C13 nuclear magnetic resonance spectroscopy, and the correlation of the molecular structure and dynamics with electric properties was discussed.

  14. Transmission of linearly polarized light in seawater: implications for polarization signaling.

    PubMed

    Shashar, Nadav; Sabbah, Shai; Cronin, Thomas W

    2004-09-01

    Partially linearly polarized light is abundant in the oceans. The natural light field is partially polarized throughout the photic range, and some objects and animals produce a polarization pattern of their own. Many polarization-sensitive marine animals take advantage of the polarization information, using it for tasks ranging from navigation and finding food to communication. In such tasks, the distance to which the polarization information propagates is of great importance. Using newly designed polarization sensors, we measured the changes in linear polarization underwater as a function of distance from a standard target. In the relatively clear waters surrounding coral reefs, partial (%) polarization decreased exponentially as a function of distance from the target, resulting in a 50% reduction of partial polarization at a distance of 1.25-3 m, depending on water quality. Based on these measurements, we predict that polarization sensitivity will be most useful for short-range (in the order of meters) visual tasks in water and less so for detecting objects, signals, or structures from far away. Navigation and body orientation based on the celestial polarization pattern are predicted to be limited to shallow waters as well, while navigation based on the solar position is possible through a deeper range. PMID:15339957

  15. An Asymmetry-to-Symmetry Switch in Signal Transmission by the Histidine Kinase Receptor for TMAO

    SciTech Connect

    Moore, Jason O.; Hendrickson, Wayne A.

    2012-06-28

    The osmoregulator trimethylamine-N-oxide (TMAO), commonplace in aquatic organisms, is used as the terminal electron acceptor for respiration in many bacterial species. The TMAO reductase (Tor) pathway for respiratory catalysis is controlled by a receptor system that comprises the TMAO-binding protein TorT, the sensor histidine kinase TorS, and the response regulator TorR. Here we study the TorS/TorT sensor system to gain mechanistic insight into signaling by histidine kinase receptors. We determined crystal structures for complexes of TorS sensor domains with apo TorT and with TorT (TMAO); we characterized TorS sensor associations with TorT in solution; we analyzed the thermodynamics of TMAO binding to TorT-TorS complexes; and we analyzed in vivo responses to TMAO through the TorT/TorS/TorR system to test structure-inspired hypotheses. TorS-TorT(apo) is an asymmetric 2:2 complex that binds TMAO with negative cooperativity to form a symmetric active kinase.

  16. An Asymmetry-to-Symmetry Switch in Signal Transmission by the Histidine Kinase Receptor for TMAO

    PubMed Central

    Moore, Jason O.; Hendrickson, Wayne A.

    2012-01-01

    Summary The osmoregulator trimethylamine-N-oxide (TMAO), commonplace in aquatic organisms, is used as the terminal electron acceptor for respiration in many bacterial species. The TMAO reductase (Tor) pathway for respiratory catalysis is controlled by a receptor system that comprises the TMAO-binding protein TorT, the sensor histidine kinase TorS and the response regulator TorR. Here we study the TorS/TorT sensor system to gain mechanistic insight into signaling by histidine kinase receptors. We determined crystal structures for complexes of TorS sensor domains with apo TorT and with TorT(TMAO); we characterized TorS sensor associations with TorT in solution; we analyzed the thermodynamics of TMAO binding to TorT-TorS complexes; and we analyzed in vivo responses to TMAO through the TorT/TorS/TorR system to test structure-inspired hypotheses. TorS-TorT(apo) is an asymmetric 2:2 complex that binds TMAO with negative cooperativity to form a symmetric active kinase. PMID:22483119

  17. Allosteric mechanisms within the adenosine A2A-dopamine D2 receptor heterotetramer.

    PubMed

    Ferré, Sergi; Bonaventura, Jordi; Tomasi, Dardo; Navarro, Gemma; Moreno, Estefanía; Cortés, Antonio; Lluís, Carme; Casadó, Vicent; Volkow, Nora D

    2016-05-01

    The structure constituted by a G protein coupled receptor (GPCR) homodimer and a G protein provides a main functional unit and oligomeric entities can be viewed as multiples of dimers. For GPCR heteromers, experimental evidence supports a tetrameric structure, comprised of two different homodimers, each able to signal with its preferred G protein. GPCR homomers and heteromers can act as the conduit of allosteric interactions between orthosteric ligands. The well-known agonist/agonist allosteric interaction in the adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromer, by which A2AR agonists decrease the affinity of D2R agonists, gave the first rationale for the use of A2AR antagonists in Parkinson's disease. We review new pharmacological findings that can be explained in the frame of a tetrameric structure of the A2AR-D2R heteromer: first, ligand-independent allosteric modulations by the D2R that result in changes of the binding properties of A2AR ligands; second, differential modulation of the intrinsic efficacy of D2R ligands for G protein-dependent and independent signaling; third, the canonical antagonistic Gs-Gi interaction within the frame of the heteromer; and fourth, the ability of A2AR antagonists, including caffeine, to also exert the same allosteric modulations of D2R ligands than A2AR agonists, while A2AR agonists and antagonists counteract each other's effects. These findings can have important clinical implications when evaluating the use of A2AR antagonists. They also call for the need of monitoring caffeine intake when evaluating the effect of D2R ligands, when used as therapeutic agents in neuropsychiatric disorders or as probes in imaging studies. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'. PMID:26051403

  18. Selective activation of the M1 muscarinic acetylcholine receptor achieved by allosteric potentiation.

    PubMed

    Ma, Lei; Seager, Matthew A; Seager, Matthew; Wittmann, Marion; Jacobson, Marlene; Bickel, Denise; Burno, Maryann; Jones, Keith; Graufelds, Valerie Kuzmick; Xu, Guangping; Pearson, Michelle; McCampbell, Alexander; Gaspar, Renee; Shughrue, Paul; Danziger, Andrew; Regan, Christopher; Flick, Rose; Pascarella, Danette; Garson, Susan; Doran, Scott; Kreatsoulas, Constantine; Veng, Lone; Lindsley, Craig W; Shipe, William; Kuduk, Scott; Sur, Cyrille; Kinney, Gene; Seabrook, Guy R; Ray, William J

    2009-09-15

    The forebrain cholinergic system promotes higher brain function in part by signaling through the M(1) muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M(1) receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M(1) mAChR. BQCA reduces the concentration of ACh required to activate M(1) up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 microM. Furthermore studies in M(1)(-/-) mice demonstrates that BQCA requires M(1) to promote inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M(1) allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces beta-arrestin recruitment to M(1), suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M(1) receptor and represents a promising therapeutic strategy for cognitive disorders. PMID:19717450

  19. Selective activation of the M1 muscarinic acetylcholine receptor achieved by allosteric potentiation

    PubMed Central

    Ma, Lei; Seager, Matthew A.; Wittmann, Marion; Jacobson, Marlene; Bickel, Denise; Burno, Maryann; Jones, Keith; Graufelds, Valerie Kuzmick; Xu, Guangping; Pearson, Michelle; McCampbell, Alexander; Gaspar, Renee; Shughrue, Paul; Danziger, Andrew; Regan, Christopher; Flick, Rose; Pascarella, Danette; Garson, Susan; Doran, Scott; Kreatsoulas, Constantine; Veng, Lone; Lindsley, Craig W.; Shipe, William; Kuduk, Scott; Sur, Cyrille; Kinney, Gene; Seabrook, Guy R.; Ray, William J.

    2009-01-01

    The forebrain cholinergic system promotes higher brain function in part by signaling through the M1 muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M1 receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M1 mAChR. BQCA reduces the concentration of ACh required to activate M1 up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 μM. Furthermore studies in M1−/− mice demonstrates that BQCA requires M1 to promote inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M1 allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces β-arrestin recruitment to M1, suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M1 receptor and represents a promising therapeutic strategy for cognitive disorders. PMID:19717450

  20. Radiation quality dependence of signal transmission and bystander induced cell killing

    NASA Astrophysics Data System (ADS)

    Esposito, Giuseppe; Bertolotti, Alessia; Facoetti, Angelica; Grande, Sveva; Mariotti, Luca; Ottolenghi, Andrea; Ranza, Elena; Simone, Giustina; Sorrentino, Eugenio; Antonella Tabocchini, Maria

    at 20 hours post exposure, whereas IL-8 release was significantly increased at shorter times, i.e. 5-7 hours after irradiation. The expression of their receptors was modulated in both irradiated and bystander cells, although it is not apparently correlated with the relative interleukin re-lease. In order to investigate possible correlation between NRS and cytokines as early and late mediators in the signalling chain leading to bystander induced cell killing, experiments were performed using c-PTIO, a well known scavengers of RNS. In these experiments conditioned medium taken after 1h or 5h from α-particle irradiated cells was used. The results obtained after 5h in the absence of c-PTIO didn't show any further decrease in clonogenic survival of bystander cells. The presence of the scavenger seems to reduce, the bystander induced cell killing indicating that RNS are involved in the transduction of the bystander signal. Experi-ments, performed with both c-PTIO and DMSO, a scavenger of hydroxyl radicals, showed that RNS and ROS play a role in some cytokine pathways (interleukins release and their receptor expression) activated by irradiation. ACKNOWLEDGEMENTS This work was partially supported by the European Commission (EC Contract FP6-36465, "NOTE")

  1. Optimization of wide-angle seismic signal-to-noise ratios and P-wave transmission in Kenya

    USGS Publications Warehouse

    Jacob, A.W.B.; Vees, R.; Braile, L.W.; Criley, E.

    1994-01-01

    In previous refraction and wide-angle reflection experiments in the Kenya Rift there were problems with poor signal-noise ratios which made good seismic interpretation difficult. Careful planning and preparation for KRISP 90 has substantially overcome these problems and produced excellent seismic sections in a difficult environment. Noise levels were minimized by working, as far as possible, at times of the day when conditions were quiet, while source signals were optimized by using dispersed charges in water where it was available and waterfilled boreholes in most cases where it was not. Seismic coupling at optimum depth in water has been found to be more than 100 times greater than it is in a borehole in dry loosely compacted material. Allowing for the source coupling, a very marked difference has been found between the observation ranges in the rift and those on the flanks, where the observation ranges are greater. These appear to indicate a significant difference in seismic transmission through the two types of crust. ?? 1994.

  2. Feasibility study of monitoring of plasma etching chamber conditions using superimposed high-frequency signals on rf power transmission line.

    PubMed

    Kasashima, Y; Uesugi, F

    2015-10-01

    An in situ monitoring system that can detect changes in the conditions of a plasma etching chamber has been developed. In the system, low-intensity high-frequency signals are superimposed on the rf power transmission line used for generating plasma. The system measures reflected high-frequency signals and detects the change in their frequency characteristics. The results indicate that the system detects the changes in the conditions in etching chambers caused by the changes in the electrode gap and the inner wall condition and demonstrate the effectiveness of the system. The system can easily be retrofitted to mass-production equipment and it can be used with or without plasma discharge. Therefore, our system is suitable for in situ monitoring of mass-production plasma etching chambers. The system is expected to contribute to development of predictive maintenance, which monitors films deposited on the inner wall of the chamber and prevents equipment faults caused by misalignment of chamber parts in mass-production equipment. PMID:26520984

  3. Gigabit radio-over-fiber link for converged baseband and millimeter-wave band signal transmission using cascaded injection-locked Fabry-Pérot laser diodes.

    PubMed

    Hong, Moon-Ki; Won, Yong-Yuk; Han, Sang-Kook

    2009-05-11

    A novel scheme, for both baseband and millimeter-wave band gigabit data transmission in radio-over-fiber system, is proposed and experimentally demonstrated by using cascaded injection-locked Fabry- Pérot laser diodes. It was able to improve suppression ratio of carrier suppressed signal using the cascaded injection-locking. The suppression ratio improvement of the optical carrier suppressed signal of 20 dB was verified. Applying this mechanism, 60-GHz millimeter-wave carrier of enhanced signal quality could be accomplished. Its peak power and phase noise were obtained as -40 dBm and -103.5 dBm/Hz respectively, which was suitable for 60-GHz data transmission. In addition, a successful bidirectional transmission of 1.25-Gbps wired and wireless data was achieved by adopting remodulation technique using a gain-saturated reflective semiconductor optical amplifier for uplink. PMID:19434116

  4. Chemical, target, and bioactive properties of allosteric modulation.

    PubMed

    van Westen, Gerard J P; Gaulton, Anna; Overington, John P

    2014-04-01

    Allosteric modulators are ligands for proteins that exert their effects via a different binding site than the natural (orthosteric) ligand site and hence form a conceptually distinct class of ligands for a target of interest. Here, the physicochemical and structural features of a large set of allosteric and non-allosteric ligands from the ChEMBL database of bioactive molecules are analyzed. In general allosteric modulators are relatively smaller, more lipophilic and more rigid compounds, though large differences exist between different targets and target classes. Furthermore, there are differences in the distribution of targets that bind these allosteric modulators. Allosteric modulators are over-represented in membrane receptors, ligand-gated ion channels and nuclear receptor targets, but are underrepresented in enzymes (primarily proteases and kinases). Moreover, allosteric modulators tend to bind to their targets with a slightly lower potency (5.96 log units versus 6.66 log units, p<0.01). However, this lower absolute affinity is compensated by their lower molecular weight and more lipophilic nature, leading to similar binding efficiency and surface efficiency indices. Subsequently a series of classifier models are trained, initially target class independent models followed by finer-grained target (architecture/functional class) based models using the target hierarchy of the ChEMBL database. Applications of these insights include the selection of likely allosteric modulators from existing compound collections, the design of novel chemical libraries biased towards allosteric regulators and the selection of targets potentially likely to yield allosteric modulators on screening. All data sets used in the paper are available for download. PMID:24699297

  5. Polypharmacology within CXCR4: Multiple binding sites and allosteric behavior

    NASA Astrophysics Data System (ADS)

    Planesas, Jesús M.; Pérez-Nueno, Violeta I.; Borrell, José I.; Teixidó, Jordi

    2014-10-01

    CXCR4 is a promiscuous receptor, which binds multiple diverse ligands. As usual in promiscuous proteins, CXCR4 has a large binding site, with multiple subsites, and high flexibility. Hence, it is not surprising that it is involved in the phenomenon of allosteric modulation. However, incomplete knowledge of allosteric ligand-binding sites has hampered an in-depth molecular understanding of how these inhibitors work. For example, it is known that lipidated fragments of intracellular GPCR loops, so called pepducins, such as pepducin ATI-2341, modulate CXCR4 activity using an agonist allosteric mechanism. Nevertheless, there are also examples of small organic molecules, such as AMD11070 and GSK812397, which may act as antagonist allosteric modulators. Here, we give new insights into this issue by proposing the binding interactions between the CXCR4 receptor and the above-mentioned allosteric modulators. We propose that CXCR4 has minimum two topographically different allosteric binding sites. One allosteric site would be in the intracellular loop 1 (ICL1) where pepducin ATI-2341 would bind to CXCR4, and the second one, in the extracellular side of CXCR4 in a subsite into the main orthosteric binding pocket, delimited by extracellular loops n° 1, 2, and the N-terminal end, where antagonists AMD11070 and GSK812397 would bind. Prediction of allosteric interactions between CXCR4 and pepducin ATI-2341 were studied first by rotational blind docking to determine the main binding region and a subsequent refinement of the best pose was performed using flexible docking methods and molecular dynamics. For the antagonists AMD11070 and GSK812397, the entire CXCR4 protein surface was explored by blind docking to define the binding region. A second docking analysis by subsites of the identified binding region was performed to refine the allosteric interactions. Finally, we identified the binding residues that appear to be essential for CXCR4 (agonists and antagonists) allosteric

  6. Allosteric modulation of Ras and the PI3K/AKT/mTOR pathway: emerging therapeutic opportunities

    PubMed Central

    Hubbard, Paul A.; Moody, Colleen L.; Murali, Ramachandran

    2014-01-01

    GTPases and kinases are two predominant signaling modules that regulate cell fate. Dysregulation of Ras, a GTPase, and the three eponymous kinases that form key nodes of the associated phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3K)/AKT/mTOR pathway have been implicated in many cancers, including pancreatic cancer, a disease noted for its current lack of effective therapeutics. The K-Ras isoform of Ras is mutated in over 90% of pancreatic ductal adenocarcinomas (PDAC) and there is growing evidence linking aberrant PI3K/AKT/mTOR pathway activity to PDAC. Although these observations suggest that targeting one of these nodes might lead to more effective treatment options for patients with pancreatic and other cancers, the complex regulatory mechanisms and the number of sequence-conserved isoforms of these proteins have been viewed as significant barriers in drug development. Emerging insights into the allosteric regulatory mechanisms of these proteins suggest novel opportunities for development of selective allosteric inhibitors with fragment-based drug discovery (FBDD) helping make significant inroads. The fact that allosteric inhibitors of Ras and AKT are currently in pre-clinical development lends support to this approach. In this article, we will focus on the recent advances and merits of developing allosteric drugs targeting these two inter-related signaling pathways. PMID:25566081

  7. Allosteric modulation of Ras and the PI3K/AKT/mTOR pathway: emerging therapeutic opportunities.

    PubMed

    Hubbard, Paul A; Moody, Colleen L; Murali, Ramachandran

    2014-01-01

    GTPases and kinases are two predominant signaling modules that regulate cell fate. Dysregulation of Ras, a GTPase, and the three eponymous kinases that form key nodes of the associated phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3K)/AKT/mTOR pathway have been implicated in many cancers, including pancreatic cancer, a disease noted for its current lack of effective therapeutics. The K-Ras isoform of Ras is mutated in over 90% of pancreatic ductal adenocarcinomas (PDAC) and there is growing evidence linking aberrant PI3K/AKT/mTOR pathway activity to PDAC. Although these observations suggest that targeting one of these nodes might lead to more effective treatment options for patients with pancreatic and other cancers, the complex regulatory mechanisms and the number of sequence-conserved isoforms of these proteins have been viewed as significant barriers in drug development. Emerging insights into the allosteric regulatory mechanisms of these proteins suggest novel opportunities for development of selective allosteric inhibitors with fragment-based drug discovery (FBDD) helping make significant inroads. The fact that allosteric inhibitors of Ras and AKT are currently in pre-clinical development lends support to this approach. In this article, we will focus on the recent advances and merits of developing allosteric drugs targeting these two inter-related signaling pathways. PMID:25566081

  8. NGL-2 Regulates Pathway-Specific Neurite Growth and Lamination, Synapse Formation, and Signal Transmission in the Retina

    PubMed Central

    Watkins, Kelly L.; Johnson, Robert E.; Schottler, Frank

    2013-01-01

    Parallel processing is an organizing principle of many neural circuits. In the retina, parallel neuronal pathways process signals from rod and cone photoreceptors and support vision over a wide range of light levels. Toward this end, rods and cones form triad synapses with dendrites of distinct bipolar cell types, and the axons or dendrites, respectively, of horizontal cells (HCs). The molecular cues that promote the formation of specific neuronal pathways remain largely unknown. Here, we discover that developing and mature HCs express the leucine-rich repeat (LRR)-containing protein netrin-G ligand 2 (NGL-2). NGL-2 localizes selectively to the tips of HC axons, which form reciprocal connections with rods. In mice with null mutations in Ngl-2 (Ngl-2−/−), many branches of HC axons fail to stratify in the outer plexiform layer (OPL) and invade the outer nuclear layer. In addition, HC axons expand lateral territories and increase coverage of the OPL, but establish fewer synapses with rods. NGL-2 can form transsynaptic adhesion complexes with netrin-G2, which we show to be expressed by photoreceptors. In Ngl-2−/− mice, we find specific defects in the assembly of presynaptic ribbons in rods, indicating that reverse signaling of complexes involving NGL-2 regulates presynaptic maturation. The development of HC dendrites and triad synapses of cone photoreceptors proceeds normally in the absence of NGL-2 and in vivo electrophysiology reveals selective defects in rod-mediated signal transmission in Ngl-2−/− mice. Thus, our results identify NGL-2 as a central component of pathway-specific development in the outer retina. PMID:23864682

  9. Allosteric antibody inhibition of human hepsin protease.

    PubMed

    Koschubs, Tobias; Dengl, Stefan; Dürr, Harald; Kaluza, Klaus; Georges, Guy; Hartl, Christiane; Jennewein, Stefan; Lanzendörfer, Martin; Auer, Johannes; Stern, Alvin; Huang, Kuo-Sen; Packman, Kathryn; Gubler, Ueli; Kostrewa, Dirk; Ries, Stefan; Hansen, Silke; Kohnert, Ulrich; Cramer, Patrick; Mundigl, Olaf

    2012-03-15

    Hepsin is a type II transmembrane serine protease that is expressed in several human tissues. Overexpression of hepsin has been found to correlate with tumour progression and metastasis, which is so far best studied for prostate cancer, where more than 90% of such tumours show this characteristic. To enable improved future patient treatment, we have developed a monoclonal humanized antibody that selectively inhibits human hepsin and does not inhibit other related proteases. We found that our antibody, hH35, potently inhibits hepsin enzymatic activity at nanomolar concentrations. Kinetic characterization revealed non-linear, slow, tight-binding inhibition. This correlates with the crystal structure we obtained for the human hepsin-hH35 antibody Fab fragment complex, which showed that the antibody binds hepsin around α3-helix, located far from the active centre. The unique allosteric mode of inhibition of hH35 is distinct from the recently described HGFA (hepatocyte growth factor activator) allosteric antibody inhibition. We further explain how a small change in the antibody design induces dramatic structural rearrangements in the hepsin antigen upon binding, leading to complete enzyme inactivation. PMID:22132769

  10. Efficiency parameters in artificial allosteric systems.

    PubMed

    Schneider, Hans-Jörg

    2016-09-14

    It is shown that the until now largely overlooked change of the conformational energy ΔGC is the dominating factor for most synthetic allosteric complexes. Essential is the energy ΔGC required for the formation of a suitable geometry for ligand binding in the absence of an effector molecule E; ΔGC is usually dominated by an increase of strain and/or by high energy solvents in a cavity. The role of the effector molecule E in such systems is to generate a suitable conformation for binding the ligand A and thus to compensate the unfavourable conformational energy ΔGC. Positive cooperativity increases with ΔGC, and decreases with the ΔG0(A) value which reflects the binding energy of A in a strain-free host. As illustrated with a few examples ΔG0(A) cannot be measured directly but can eventually be estimated independently. Many artificial allosteric systems described in the literature, such as those based on ethylene glycol chains or bipyridyl units, lack significant strain differences, and are therefore less efficient. Negative cooperativity is determined only by the difference ΔΔGA,E between the binding energies at the two sites; it can be enhanced or lowered by concomitant changes in ΔGC. PMID:27431438

  11. All-optical clock recovery for 100 Gb/s RZ-OOK signal after 25km transmission using a dual-mode beating DBR laser

    NASA Astrophysics Data System (ADS)

    Yu, Liqiang; Pan, Biwei; Lu, Dan; Zhao, Lingjuan

    2014-11-01

    All-optical clock recovery (AOCR) for 100 Gb/s RZ-OOK signal is demonstrated by using a dualmode beating DBR laser. Based on the injection-locking of the DBR (distributed Bragg reflector) laser, a 100-GHz optical clock is recovered. Timing jitter (<1 ps) derived from both phase noise and power fluctuation is measured by an optical sampling oscilloscope (OSO). Furthermore, clock recovery is also realized for the 100 Gb/s signal after 25 km transmission. After the 25-km SMF (5- dB loss) transmission, the signal-to-noise ratio (SNR) of the signal drops from 18 dB to 5.2 dB. The dependence of the timing jitter on the input power is investigated. The lowest timing jitter of 665 fs is realized when the input power is 3 dBm.

  12. 100.29-Gb/s direct detection optical OFDM/OQAM 32-QAM signal over 880  km SSMF transmission using a single photodiode.

    PubMed

    Li, Chao; Yang, Qi; Luo, Ming; He, Zhixue; Li, Haibo; Hu, Rong; Yu, Shaohua

    2015-04-01

    We propose a novel guard-band-shared direct-detection (GBS-DD) scheme for a 100-Gb/s single-photodiode direct-detection transmission system. The 100.29 Gb/s signal is successfully transmitted over 880 km standard single mode fiber (SSMF) with Raman amplification under the 20% forward error correction (FEC) threshold within 52 GHz optical bandwidth. The signal is modulated with orthogonal frequency-division multiplexing/offset quadrature-amplitude-modulation 32-ary QAM (OFDM/OQAM 32-QAM). The signal-to-signal beat interference (SSBI) terms fall and overlap in the same guard band. Adopting the proposed approach, the bandwidth usage efficiency of the photodiode is greatly enhanced, which brings benefits on the data rate and transmission performance. PMID:25831288

  13. Ignavine: a novel allosteric modulator of the μ opioid receptor.

    PubMed

    Ohbuchi, Katsuya; Miyagi, Chika; Suzuki, Yasuyuki; Mizuhara, Yasuharu; Mizuno, Keita; Omiya, Yuji; Yamamoto, Masahiro; Warabi, Eiji; Sudo, Yuka; Yokoyama, Akinobu; Miyano, Kanako; Hirokawa, Takatsugu; Uezono, Yasuhito

    2016-01-01

    Processed Aconiti tuber (PAT) is used to treat pain associated with various disorders. Although it has been demonstrated that the κ opioid receptor (KOR) signaling pathway is a mediator of the analgesic effect of PAT, active components affecting opioid signaling have not yet been identified. In this study, we explored candidate components of PAT by pharmacokinetic analysis and identified ignavine, which is a different structure from aconitine alkaloids. A receptor binding assay of opioid receptors showed that ignavine specifically binds the μ opioid receptor (MOR), not the KOR. Receptor internalization assay in MOR-expressing cell lines revealed that ignavine augmented the responses produced by D-Ala(2)-N-Me-Phe(4)-Gly-ol(5)-enkephalin (DAMGO), a representative MOR agonist, at a low concentration and inhibited it at a higher concentration. Ignavine also exerted positive modulatory activity for DAMGO, endomorphin-1 and morphine in cAMP assay. Additionally, ignavine alone showed an analgesic effect in vivo. In silico simulation analysis suggested that ignavine would induce a unique structural change distinguished from those induced by a representative MOR agonist and antagonist. These data collectively suggest the possibility that ignavine could be a novel allosteric modulator of the MOR. The present results may open the way for the development of a novel pain management strategy. PMID:27530869

  14. Ignavine: a novel allosteric modulator of the μ opioid receptor

    PubMed Central

    Ohbuchi, Katsuya; Miyagi, Chika; Suzuki, Yasuyuki; Mizuhara, Yasuharu; Mizuno, Keita; Omiya, Yuji; Yamamoto, Masahiro; Warabi, Eiji; Sudo, Yuka; Yokoyama, Akinobu; Miyano, Kanako; Hirokawa, Takatsugu; Uezono, Yasuhito

    2016-01-01

    Processed Aconiti tuber (PAT) is used to treat pain associated with various disorders. Although it has been demonstrated that the κ opioid receptor (KOR) signaling pathway is a mediator of the analgesic effect of PAT, active components affecting opioid signaling have not yet been identified. In this study, we explored candidate components of PAT by pharmacokinetic analysis and identified ignavine, which is a different structure from aconitine alkaloids. A receptor binding assay of opioid receptors showed that ignavine specifically binds the μ opioid receptor (MOR), not the KOR. Receptor internalization assay in MOR-expressing cell lines revealed that ignavine augmented the responses produced by D-Ala(2)-N-Me-Phe(4)-Gly-ol(5)-enkephalin (DAMGO), a representative MOR agonist, at a low concentration and inhibited it at a higher concentration. Ignavine also exerted positive modulatory activity for DAMGO, endomorphin-1 and morphine in cAMP assay. Additionally, ignavine alone showed an analgesic effect in vivo. In silico simulation analysis suggested that ignavine would induce a unique structural change distinguished from those induced by a representative MOR agonist and antagonist. These data collectively suggest the possibility that ignavine could be a novel allosteric modulator of the MOR. The present results may open the way for the development of a novel pain management strategy. PMID:27530869

  15. Detection of DNA methyltransferase activity using allosteric molecular beacons.

    PubMed

    Zhang, Weiting; Zu, Xiaolong; Song, Yanling; Zhu, Zhi; Yang, Chaoyong James

    2016-01-21

    Abnormal DNA methylation patterns caused by altered DNA methyltransferase (MTase) activity are closely associated with cancer. Herein, using DNA adenine methylation methyltransferase (Dam MTase) as a model analyte, we designed an allosteric molecular beacon (aMB) for sensitive detection of Dam MTase activity. When the specific site in an aMB is methylated by Dam MTase, the probe can be cut by the restriction nuclease DpnI to release a fluorophore labeled aptamer specific for streptavidin (SA) which will bind to SA beads to generate highly fluorescent beads for easy signal readout by a microscope or flow cytometer. However, aMBs maintain a hairpin structure without the binding ability to SA beads in the absence of Dam MTase, leading to weakly fluorescent SA beads. Unlike the existing signal amplified assays, our method is simpler and more convenient. The high performance of the aptamer and the easy bead separation process make this probe superior to other methods for the detection of MTase in complex biological systems. Overall, the proposed method with a detection limit of 0.57 U mL(-1) for Dam MTase shows great potential for further applications in the detection of other MTases, screening of MTase inhibitors, and early diagnosis of cancer. PMID:26478921

  16. Remote Activation of Host Cell DNA Synthesis in Uninfected Cells Signaled by Infected Cells in Advance of Virus Transmission

    PubMed Central

    Schmidt, Nora; Hennig, Thomas; Serwa, Remigiusz A.; Marchetti, Magda

    2015-01-01

    effector. The field has had no conception that this process occurs, and the work changes our interpretation of virus-host interaction during advancing infection and has implications for understanding controls of host DNA synthesis. Our findings demonstrate the utility of chemical biology techniques in analysis of infection processes, reveal distinct processes when infection is examined in multiround transmission versus single-step growth curves, and reveal a hitherto-unknown process in virus infection, likely relevant for other viruses (and other infectious agents) and for remote signaling of other processes, including transcription and protein synthesis. PMID:26311877

  17. Allosteric activation of the Par-6 PDZ via a partial unfolding transition

    PubMed Central

    Whitney, Dustin S.; Peterson, Francis C.; Kovrigin, Evgenii L.; Volkman, Brian F.

    2013-01-01

    Proteins exist in a delicate balance between the native and unfolded states, where thermodynamic stability may be sacrificed to attain the flexibility required for efficient catalysis, binding or allosteric control. Par-6 regulates the Par polarity complex by transmitting a GTPase signal through the CRIB-PDZ module that alters PDZ lig-and binding. Allosteric activation of the PDZ is achieved by local rearrangement of the L164 and K165 side chains to stabilize the interdomain CRIB-PDZ interface and reposition a conserved element of the ligand binding pocket. However, microsecond to millisecond dynamics measurements revealed that L164/K165 exchange requires a larger rearrangement than expected. The margin of thermodynamic stability for the PDZ domain is modest (~3 kcal/mol) and further reduced by transient interactions with the disordered CRIB domain. Measurements of local structural stability revealed that tertiary contacts within the PDZ are disrupted by a partial unfolding transition that enables interconversion of the L/K switch. The unexpected participation of partial PDZ unfolding in the allosteric mechanism of Par-6 suggests that native-state unfolding may be essential for the function of other marginally stable proteins. PMID:23705660

  18. Are AMPA receptor positive allosteric modulators potential pharmacotherapeutics for addiction?

    PubMed

    Watterson, Lucas R; Olive, M Foster

    2013-01-01

    Positive allosteric modulators (PAMs) of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a diverse class of compounds that increase fast excitatory transmission in the brain. AMPA PAMs have been shown to facilitate long-term potentiation, strengthen communication between various cortical and subcortical regions, and some of these compounds increase the production and release of brain-derived neurotrophic factor (BDNF) in an activity-dependent manner. Through these mechanisms, AMPA PAMs have shown promise as broad spectrum pharmacotherapeutics in preclinical and clinical studies for various neurodegenerative and psychiatric disorders. In recent years, a small collection of preclinical animal studies has also shown that AMPA PAMs may have potential as pharmacotherapeutic adjuncts to extinction-based or cue-exposure therapies for the treatment of drug addiction. The present paper will review this preclinical literature, discuss novel data collected in our laboratory, and recommend future research directions for the possible development of AMPA PAMs as anti-addiction medications. PMID:24380895

  19. Are AMPA Receptor Positive Allosteric Modulators Potential Pharmacotherapeutics for Addiction?

    PubMed Central

    Watterson, Lucas R.; Olive, M. Foster

    2013-01-01

    Positive allosteric modulators (PAMs) of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a diverse class of compounds that increase fast excitatory transmission in the brain. AMPA PAMs have been shown to facilitate long-term potentiation, strengthen communication between various cortical and subcortical regions, and some of these compounds increase the production and release of brain-derived neurotrophic factor (BDNF) in an activity-dependent manner. Through these mechanisms, AMPA PAMs have shown promise as broad spectrum pharmacotherapeutics in preclinical and clinical studies for various neurodegenerative and psychiatric disorders. In recent years, a small collection of preclinical animal studies has also shown that AMPA PAMs may have potential as pharmacotherapeutic adjuncts to extinction-based or cue-exposure therapies for the treatment of drug addiction. The present paper will review this preclinical literature, discuss novel data collected in our laboratory, and recommend future research directions for the possible development of AMPA PAMs as anti-addiction medications. PMID:24380895

  20. Emerging Computational Methods for the Rational Discovery of Allosteric Drugs.

    PubMed

    Wagner, Jeffrey R; Lee, Christopher T; Durrant, Jacob D; Malmstrom, Robert D; Feher, Victoria A; Amaro, Rommie E

    2016-06-01

    Allosteric drug development holds promise for delivering medicines that are more selective and less toxic than those that target orthosteric sites. To date, the discovery of allosteric binding sites and lead compounds has been mostly serendipitous, achieved through high-throughput screening. Over the past decade, structural data has become more readily available for larger protein systems and more membrane protein classes (e.g., GPCRs and ion channels), which are common allosteric drug targets. In parallel, improved simulation methods now provide better atomistic understanding of the protein dynamics and cooperative motions that are critical to allosteric mechanisms. As a result of these advances, the field of predictive allosteric drug development is now on the cusp of a new era of rational structure-based computational methods. Here, we review algorithms that predict allosteric sites based on sequence data and molecular dynamics simulations, describe tools that assess the druggability of these pockets, and discuss how Markov state models and topology analyses provide insight into the relationship between protein dynamics and allosteric drug binding. In each section, we first provide an overview of the various method classes before describing relevant algorithms and software packages. PMID:27074285

  1. Emerging Computational Methods for the Rational Discovery of Allosteric Drugs

    PubMed Central

    2016-01-01

    Allosteric drug development holds promise for delivering medicines that are more selective and less toxic than those that target orthosteric sites. To date, the discovery of allosteric binding sites and lead compounds has been mostly serendipitous, achieved through high-throughput screening. Over the past decade, structural data has become more readily available for larger protein systems and more membrane protein classes (e.g., GPCRs and ion channels), which are common allosteric drug targets. In parallel, improved simulation methods now provide better atomistic understanding of the protein dynamics and cooperative motions that are critical to allosteric mechanisms. As a result of these advances, the field of predictive allosteric drug development is now on the cusp of a new era of rational structure-based computational methods. Here, we review algorithms that predict allosteric sites based on sequence data and molecular dynamics simulations, describe tools that assess the druggability of these pockets, and discuss how Markov state models and topology analyses provide insight into the relationship between protein dynamics and allosteric drug binding. In each section, we first provide an overview of the various method classes before describing relevant algorithms and software packages. PMID:27074285

  2. Coupled Dynamics and Entropic Contribution to the Allosteric Mechanism of Pin1.

    PubMed

    Barman, Arghya; Hamelberg, Donald

    2016-08-25

    Allosteric communication in proteins regulates a plethora of downstream processes in subcellular signaling pathways. Describing the effects of cooperative ligand binding on the atomic level is a key to understanding many regulatory processes involving biomolecules. Here, we use microsecond-long molecular dynamics simulations to investigate the allosteric mechanism of Pin1, a potential therapeutic target and a phosphorylated-Ser/Thr dependent peptidyl-prolyl cis-trans isomerase that regulates several subcellular processes and has been implicated in many diseases, including cancer and Alzheimer's. Experimental studies suggest that the catalytic domain and the noncatalytic WW domain are allosterically coupled; however, an atomic level description of the dynamics associated with the interdomain communication is lacking. We show that binding of the substrate to the WW domain is directly coupled to the dynamics of the catalytic domain, causing rearrangement of the residue-residue contact dynamics from the WW domain to the catalytic domain. The binding affinity of the substrate in the catalytic domain is also enhanced upon binding of the substrate to the WW domain. Modulation of the dynamics of the catalytic domain upon binding of the substrate to the WW domain leads to prepayment of the entropic cost of binding the substrate to the catalytic domain. This study shows that Ile 28 at the interfacial region between the catalytic and WW domains is certainly one of the residues responsible for bridging the communication between the two domains. The results complement previous experiments and provide valuable atomistic insights into the role of dynamics and possible entropic contribution to the allosteric mechanism of proteins. PMID:27077947

  3. Structural dynamics and energetics underlying allosteric inactivation of the cannabinoid receptor CB1

    PubMed Central

    Fay, Jonathan F.; Farrens, David L.

    2015-01-01

    G protein-coupled receptors (GPCRs) are surprisingly flexible molecules that can do much more than simply turn on G proteins. Some even exhibit biased signaling, wherein the same receptor preferentially activates different G-protein or arrestin signaling pathways depending on the type of ligand bound. Why this behavior occurs is still unclear, but it can happen with both traditional ligands and ligands that bind allosterically outside the orthosteric receptor binding pocket. Here, we looked for structural mechanisms underlying these phenomena in the marijuana receptor CB1. Our work focused on the allosteric ligand Org 27569, which has an unusual effect on CB1—it simultaneously increases agonist binding, decreases G-protein activation, and induces biased signaling. Using classical pharmacological binding studies, we find that Org 27569 binds to a unique allosteric site on CB1 and show that it can act alone (without need for agonist cobinding). Through mutagenesis studies, we find that the ability of Org 27569 to bind is related to how much receptor is in an active conformation that can couple with G protein. Using these data, we estimated the energy differences between the inactive and active states. Finally, site-directed fluorescence labeling studies show the CB1 structure stabilized by Org 27569 is different and unique from that stabilized by antagonist or agonist. Specifically, transmembrane helix 6 (TM6) movements associated with G-protein activation are blocked, but at the same time, helix 8/TM7 movements are enhanced, suggesting a possible mechanism for the ability of Org 27569 to induce biased signaling. PMID:26100912

  4. Joint Source-Channel Coding Based on Cosine-Modulated Filter Banks for Erasure-Resilient Signal Transmission

    NASA Astrophysics Data System (ADS)

    Marinkovic, Slavica; Guillemot, Christine

    2005-12-01

    This paper examines erasure resilience of oversampled filter bank (OFB) codes, focusing on two families of codes based on cosine-modulated filter banks (CMFB). We first revisit OFBs in light of filter bank and frame theory. The analogy with channel codes is then shown. In particular, for paraunitary filter banks, we show that the signal reconstruction methods derived from the filter bank theory and from coding theory are equivalent, even in the presence of quantization noise. We further discuss frame properties of the considered OFB structures. Perfect reconstruction (PR) for the CMFB-based OFBs with erasures is proven for the case of erasure patterns for which PR depends only on the general structure of the code and not on the prototype filters. For some of these erasure patterns, the expression of the mean-square reconstruction error is also independent of the filter coefficients. It can be expressed in terms of the number of erasures, and of parameters such as the number of channels and the oversampling ratio. The various structures are compared by simulation for the example of an image transmission system.

  5. Signaling mechanism underlying α2A -adrenergic suppression of excitatory synaptic transmission in the medial prefrontal cortex of rats.

    PubMed

    Yi, Feng; Liu, Shu-Su; Luo, Fei; Zhang, Xue-Han; Li, Bao-Ming

    2013-08-01

    Stimulation of α2A -adrenoceptors (ARs) in the prefrontal cortex (PFC) produces a beneficial effect on cognitive functions such as working memory. A previous study in our laboratory showed that α2A -AR stimulation suppresses excitatory synaptic transmission in layer V-VI pyramidal cells of the rat medial PFC (mPFC). However, the intracellular mechanism underlying the α2A -AR suppression remains unclear. In the present study, we recorded evoked excitatory postsynaptic current (eEPSC) in layer V-VI pyramidal cells of the mPFC, using whole-cell patch-clamp recording. We found that the α2A -AR agonist guanfacine significantly suppresses eEPSC in mPFC pyramidal cells. The α2A -AR inhibition is mediated by the Gi-cAMP-PKA-PP1-CaMKII-AMPAR signaling pathway, as such inhibition no longer exists when each step of this pathway is blocked with NF023, Rp-cAMP, PKI5-24 or H89, tautomycin, and KN-62 or KN-93, respectively. PMID:23701442

  6. Determination of fission neutron transmission through waste matrix material using neutron signal correlation from active assay of {sup 239}Pu

    SciTech Connect

    Hollas, C.L.; Arnone, G.; Brunson, G.; Coop, K.

    1996-09-01

    The accuracy of TRU (transuranic) waste assay using the differential die-away technique depends upon significant corrections to compensate for the effects of the matrix material in which the TRU waste is located. The authors have used a new instrument, the Combined Thermal/Epithermal Neutron (CTEN) instrument for the assay of TRU waste, to develop methods to improve the accuracy of these corrections. Neutrons from a pulsed 14-MeV neutron generator are moderated in the walls of the CTEN cavity and induce fission in the TRU material. The prompt neutrons from these fission events are detected in cadmium-wrapped {sup 3}He neutron detectors. They report new methods of data acquisition and analysis to extract correlation in the neutron signals resulting form fission during active interrogation. They use the correlation information in conjunction with the total number of neutrons to determine the fraction of fission neutrons transmitted through the matrix material into the {sup 3}He detectors. This determination allows them to cleanly separate the matrix effects into two processes: matrix modification upon the neutron interrogating flux and matrix modification upon the fraction of fission neutrons transmitted to the neutron detectors. This transmission information is also directly applied in a neutron multiplicity analysis in the passive assay of {sup 240}Pu.

  7. Signal transmission from motor axons to group Ia muscle spindle afferents: frequency responses and second-order non-linearities.

    PubMed

    Windhorst, U; Kokkoroyiannis, T; Laouris, Y; Meyer-Lohmann, J

    1994-03-01

    Spinal recurrent inhibition via Renshaw cells and proprioceptive feedback via skeletal muscle and muscle spindle afferents have been hypothesized to constitute a compound feedback system [Windhorst (1989) Afferent Control of Posture and Locomotion; Windhorst (1993) Robots and Biological Systems--Towards a New Bionics]. To assess their detailed functions, it is necessary to know their dynamic characteristics. Previously we have extensively described the properties of signal transmission from motor axons to Renshaw cells using random motor axon stimulation and data analysis methods based thereupon. Using the same methods, we here compare these properties, in the cat, with those between motor axons and group Ia muscle spindle afferents in terms of frequency responses and nonlinear features. The frequency responses depend on the mean rate (carrier rate) of activation of motor axons and on the strength of coupling between motor units and spindles. In general, they are those of a second-order low-pass system with a cut-off at fairly low frequencies. This contrasts with the dynamics of motor axon-Renshaw cell couplings which are those of a much broader band-pass with its peak in the range of c. 2-15 Hz [Christakos (1987) Neuroscience 23, 613-623]. The second-order non-linearities in motor unit-muscle spindle signal lines are much more diverse than those in motor axon-Renshaw cell couplings. Although the average strength of response declines with mean stimulus rate in both subsystems, there is no systematic relationship between the amount of non-linearity and the average response in the former, whilst there is in the latter. The qualitative appearance of motor unit-muscle spindle non-linearities was complicated as was the average response to motor unit twitches. Thus, whilst Renshaw cells appear to dynamically reflect motor output rather faithfully, muscle spindles seem to signal local muscle fibre length changes and their dynamics. This would be consistent with the

  8. Allosteric Modification, the Primary ATP Activation Mechanism of ANF-RGC

    PubMed Central

    Duda, Teresa; Yadav, Prem; Sharma, Rameshwar K.

    2011-01-01

    ANF-RGC is the prototype receptor membrane guanylate cyclase being both the receptor and the signal transducer of the most hypotensive hormones, ANF and BNP. It is a single transmembrane-spanning protein. After binding these hormones at the extracellular domain it at its intracellular domain signals activation of the C-terminal catalytic module and accelerates the production of its second messenger, cyclic GMP, which controls blood pressure, cardiac vasculature and fluid secretion. ATP is obligatory for the post-transmembrane dynamic events leading to ANF-RGC activation. It functions through the ATP regulated module, ARM (KHD) domain, of ANF-RGC. In the current over-a-decade-held-model “phosphorylation of the KHD is absolutely required for hormone-dependent activation of NPR-A” (Potter, L.R., and T. Hunter. 1998. Mol. Cell. Biol. 18: 2164–2172). The presented study challenges this concept. It demonstrates that, instead, ATP allosteric modification of ARM is the primary signaling step of ANF-GC activation. In this 2-step new dynamic model, ATP in the first step binds ARM. This triggers in it a chain of transduction events, which cause its allosteric modification. The modification partially activates (about 50%) ANF-RGC; and concomitantly also prepares the ARM for the second successive step. In this second step, ARM is phosphorylated and ANF-RGC achieves additional (~50%) full catalytic activation. The study defines a new paradigm of ANF-RGC signaling mechanism. PMID:21222471

  9. Ligand Binding to Macromolecules: Allosteric and Sequential Models of Cooperativity.

    ERIC Educational Resources Information Center

    Hess, V. L.; Szabo, Attila

    1979-01-01

    A simple model is described for the binding of ligands to macromolecules. The model is applied to the cooperative binding by hemoglobin and aspartate transcarbamylase. The sequential and allosteric models of cooperative binding are considered. (BB)

  10. Regulation of G Protein-Coupled Receptors by Allosteric Ligands

    PubMed Central

    2013-01-01

    Topographically distinct, druggable, allosteric sites may be present on all G protein-coupled receptors (GPCRs). As such, targeting these sites with synthetic small molecules offers an attractive approach to develop receptor-subtype selective chemical leads for the development of novel therapies. A crucial part of drug development is to understand the acute and chronic effects of such allosteric modulators at their corresponding GPCR target. Key regulatory processes including cell-surface delivery, endocytosis, recycling, and down-regulation tightly control the number of receptors at the surface of the cell. As many GPCR therapeutics will be administered chronically, understanding how such ligands modulate these regulatory pathways forms an essential part of the characterization of novel GPCR ligands. This is true for both orthosteric and allosteric ligands. In this Review, we summarize our current understanding of GPCR regulatory processes with a particular focus on the effects and implications of allosteric targeting of GPCRs. PMID:23398684

  11. Allosteric regulation of focal adhesion kinase by PIP₂ and ATP.

    PubMed

    Zhou, Jing; Bronowska, Agnieszka; Le Coq, Johanne; Lietha, Daniel; Gräter, Frauke

    2015-02-01

    Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase that regulates cell signaling, proliferation, migration, and development. A major mechanism of regulation of FAK activity is an intramolecular autoinhibitory interaction between two of its domains--the catalytic and FERM domains. Upon cell adhesion to the extracellular matrix, FAK is being translocated toward focal adhesion sites and activated. Interactions of FAK with phosphoinositide phosphatidylinsositol-4,5-bis-phosphate (PIP₂) are required to activate FAK. However, the molecular mechanism of the activation remains poorly understood. Recent fluorescence resonance energy transfer experiments revealed a closure of the FERM-kinase interface upon ATP binding, which is reversed upon additional binding of PIP₂. Here, we addressed the allosteric regulation of FAK by performing all-atom molecular-dynamics simulations of a FAK fragment containing the catalytic and FERM domains, and comparing the dynamics in the absence or presence of ATP and PIP₂. As a major conformational change, we observe a closing and opening motion upon ATP and additional PIP₂ binding, respectively, in good agreement with the fluorescence resonance energy transfer experiments. To reveal how the binding of the regulatory PIP₂ to the FERM F2 lobe is transduced to the very distant F1/N-lobe interface, we employed force distribution analysis. We identified a network of mainly charged residue-residue interactions spanning from the PIP₂ binding site to the distant interface between the kinase and FERM domains, comprising candidate residues for mutagenesis to validate the predicted mechanism of FAK activation. PMID:25650936

  12. Positive allosteric action of eburnamonine on cardiac muscarinic acetylcholine receptors.

    PubMed

    Proska, J; Tucek, S

    1996-06-01

    It was discovered recently that alcuronium and strychnine (which is a precursor of alcuronium) allosterically increase the affinity of cardiac muscarinic receptors for the antagonist, N-methylscopolamine. We have now investigated the effects of l-eburnamonine and vincamine, which are both closely related to strychnine. In experiments on rat heart atria, l-eburnamonine was found to increase the binding of [3H]N-methylscopolamine with Ehlert's cooperativity coefficient alpha = 0.35, which indicates that the strength of its allosteric action is close to that of alcuronium and strychnine (alpha = 0.31 and 0.44, respectively). However, the affinity of l-eburnamonine for the cardiac muscarinic receptors is lower than the affinities of alcuronium and strychnine (KAR = 22.6 microM, 0.15 microM, and 3.4 microM, respectively). In spite of its extremely close similarity to l-eburnamonine, vincamine has a negative allosteric effect on the binding of [3H]N-methylscopolamine (alpha = 4.1; KAR = 22.8 microM). It is likely that a systematic investigation of the allosteric effects of the analogues of strychnine will not only yield new allosteric effectors on muscarinic receptors, but also clarify the structural features responsible for the direction (positive or negative) of their allosteric effect. PMID:8813554

  13. Positive Allosteric Modulators of Metabotropic Glutamate 2 Receptors in Schizophrenia Treatment

    PubMed Central

    Ellaithy, Amr; Younkin, Jason; Gonzalez-Maeso, Javier; Logothetis, Diomedes E.

    2015-01-01

    The last two decades have witnessed a rise in the “NMDA receptor hypofunction” hypothesis for schizophrenia, a devastating disorder that affects around 1% of the population worldwide. A variety of presynaptic, postsynaptic and regulatory proteins involved in glutamatergic signaling have thus been proposed as potential therapeutic targets. This Review focuses on positive allosteric modulation of metabotropic glutamate 2 receptors (mGlu2Rs) and discusses how recent preclinical epigenetic data may provide a molecular explanation for the discrepant results of clinical studies, further stimulating the field to exploit the promise of mGlu2R as a target for schizophrenia treatment. PMID:26148747

  14. Transmission performance of the single-sideband optical OFDM signal with reduced guard-band based on beat interference cancellation receiver

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Zheng, Guoli; Zhou, Wei

    2015-12-01

    We have investigated the fiber transmission performance of the single-sideband optical orthogonal frequency division multiplexing (SSB-OOFDM) signal with reduced guard band (GB) received by the beat interference cancellation receiver based on balanced detection (ICRBD). The simulation results show that the error vector magnitude (EVM) of the 40 Gb/s 16-QAM SSB-OOFDM with 2 GHz GB remains below the forward error correction (FEC) limit even after 5×100 km standard single-mode fiber (SSMF) transmission. The link has stable tolerance of both the laser linewidth and the linear channel imperfections.

  15. Fading-free transmission of 124-Gb/s PDM-DMT signal over 100-km SSMF using digital carrier regeneration.

    PubMed

    Li, Cai; Hu, Rong; Yang, Qi; Luo, Ming; Li, Wei; Yu, Shaohua

    2016-01-25

    The coherent reception of intensity modulated signal has been recently widely investigated, in which the signal is recovered by the envelop detection. High linewidth tolerance is achieved with such scheme. However, strong optical carrier exists during the transmission, which degrades the optical power efficiency. In this paper, an efficient modulation scheme for discrete multi-tone (DMT) signal is proposed based on the Mach-Zehnder modulator (MZM). Different from the traditional intensity modulation, the proposed method employs both intensity and phase domain. Thus, the optical carrier power can be greatly reduced by adjusting the bias of MZM around the null point. By employing coherent detection and digital carrier regeneration (DCR), the carrier suppressed DMT signal can be recovered using envelop detection. No carrier frequency or phase estimation is required. Numerical investigations are made to demonstrate the feasibility, in which significant improvements are found for the proposed DCR method, showing great tolerance against laser linewidth and carrier power reduction. Finally, a 124-Gb/s transmission of polarization-division multiplexed DMT (PDM-DMT) signal is demonstrated over 100-km SSMF, with only -8 dB optical carrier to signal power ratio (CSPR). PMID:26832465

  16. Transmission of electric and magnetic foetal cardiac signals in a case of ectopia cordis: the dominant role of the vernix caseosa

    NASA Astrophysics Data System (ADS)

    Wakai, R. T.; Lengle, J. M.; Leuthold, A. C.

    2000-07-01

    Foetal electrocardiograms (fECGs) and foetal magnetocardiograms (fMCGs) were recorded in the 26th, 29th and 31st weeks of gestation from a foetus with ectopia cordis - a rare condition in which the heart lies outside the chest wall. This provided an opportunity to study foetal cardiograms uninfluenced by the insulating effects of the foetal skin and vernix caseosa. The fECG of the ectopia cordis foetus was striking. Unlike recordings from age-matched normal foetuses, recordings from this subject had very high signal-to-noise ratio and showed no anomalous signal transmission properties. In contrast, fMCGs recorded from the ectopia cordis foetus and normal foetuses were largely similar. Both showed high signal-to-noise ratio and signal transmission properties consistent with volume conduction. The findings corroborate the hypothesis that high foetal skin resistance due primarily to the vernix caseosa is responsible for the low amplitude and anomalous transmission properties of the normal fECG, and demonstrate that the fMCG is relatively insensitive to conductivity inhomogeneities.

  17. TLR2 Signaling Decreases Transmission of Streptococcus pneumoniae by Limiting Bacterial Shedding in an Infant Mouse Influenza A Co-infection Model

    PubMed Central

    Richard, Aimee L.; Siegel, Steven J.; Erikson, Jan; Weiser, Jeffrey N.

    2014-01-01

    While the importance of transmission of pathogens is widely accepted, there is currently little mechanistic understanding of this process. Nasal carriage of Streptococcus pneumoniae (the pneumococcus) is common in humans, especially in early childhood, and is a prerequisite for the development of disease and transmission among hosts. In this study, we adapted an infant mouse model to elucidate host determinants of transmission of S. pneumoniae from inoculated index mice to uninfected contact mice. In the context of co-infection with influenza A virus, the pneumococcus was transmitted among wildtype littermates, with approximately half of the contact mice acquiring colonization. Mice deficient for TLR2 were colonized to a similar density but transmitted S. pneumoniae more efficiently (100% transmission) than wildtype animals and showed decreased expression of interferon α and higher viral titers. The greater viral burden in tlr2−/− mice correlated with heightened inflammation, and was responsible for an increase in bacterial shedding from the mouse nose. The role of TLR2 signaling was confirmed by intranasal treatment of wildtype mice with the agonist Pam3Cys, which decreased inflammation and reduced bacterial shedding and transmission. Taken together, these results suggest that the innate immune response to influenza virus promotes bacterial shedding, allowing the bacteria to transit from host to host. These findings provide insight into the role of host factors in the increased pneumococcal carriage rates seen during flu season and contribute to our overall understanding of pathogen transmission. PMID:25166617

  18. CMOS mixed-signal MODEM for data transmission and control of electrical household appliances using the low-voltage power line

    NASA Astrophysics Data System (ADS)

    Escalera, Sara; Dominguez-Matas, Carlos M.; Garcia-Gonzalez, Jose M.; Guerra, Oscar; Rodriguez-Vazquez, Angel

    2003-04-01

    This paper presents a CMOS mixed-signal MODEM ASIC for data transmission on the low-voltage power line. The circuit includes all the analog circuitry needed for input interfacing and modulation/demodulation (PLL-based frequency synthesis, slave filter banks with PLL master VCO for tuning, and decision circuitry) plus the logic circuitry needed for control purposes. To allow the communication between the electrical household appliances and a remote unit to control them as well as to reduce the cost, an unique mixed-signal ASIC, made of two parts, one operating at high frequencies and another operating at lower frequencies, has been designed. The High Frequencies Module must allow the connection with the external control systems and, to ensure reasonable robustness, has to be able to send and receive signals using at least two different channels (to avoid local and temporary degradations of the communication). The Low Frequencies Module is needed to manage the indoors communication. This module enables the transmission of signals within distances between 50 and 100 meters with a speed in the order of, but never less than, 100 bits/s. This link should be accomplished by using a frequency range in such a way that a maximum number of channels are disposable to allow the control of as many different in-house devices as possible. Again, to this end, two different tunable channels have to be simultaneously available: one to control the quality of the signal and the other to allow the effective communication.

  19. Tunable Allosteric Behavior in Random Spring Networks

    NASA Astrophysics Data System (ADS)

    Rocks, Jason W.; Pashine, Nidhi; Bischofberger, Irmgard; Goodrich, Carl P.; Nagel, Sidney R.; Liu, Andrea J.

    Many proteins and other macromolecules exhibit allosteric behavior in which the binding of a ligand to one site affects the activity at a second distant site. Inspired by this biological process, we present an algorithm to tune disordered spring networks to exhibit allostery-like behavior. When the positions of a pair of nodes at one site in a network are perturbed, we can precisely tune the response of nodes located at another distant site in the system by removing only a small fraction of the bonds. This algorithm can be used to create a wide variety of different response types: response nodes can be located far away from each other, a large number of response sites can be simultaneously controlled, and even multiple independent responses can be tuned into the system. In addition, this algorithm can be generalized to account for bond bending, geometric nonlinearities and nonlinear bond potentials. However, even linear calculations match surprisingly well with macroscopic experimental realizations made by laser cutting or 3D printing.

  20. Allosteric inhibition of antiapoptotic MCL-1.

    PubMed

    Lee, Susan; Wales, Thomas E; Escudero, Silvia; Cohen, Daniel T; Luccarelli, James; Gallagher, Catherine G; Cohen, Nicole A; Huhn, Annissa J; Bird, Gregory H; Engen, John R; Walensky, Loren D

    2016-06-01

    MCL-1 is an antiapoptotic BCL-2 family protein that has emerged as a major pathogenic factor in human cancer. Like BCL-2, MCL-1 bears a surface groove whose function is to sequester the BH3 killer domains of proapoptotic BCL-2 family members, a mechanism harnessed by cancer cells to establish formidable apoptotic blockades. Although drugging the BH3-binding groove has been achieved for BCL-2, translating this approach to MCL-1 has been challenging. Here, we report an alternative mechanism for MCL-1 inhibition by small-molecule covalent modification of C286 at a new interaction site distant from the BH3-binding groove. Our structure-function analyses revealed that the BH3 binding capacity of MCL-1 and its suppression of BAX are impaired by molecular engagement, a phenomenon recapitulated by C286W mutagenic mimicry in vitro and in mouse cells. Thus, we characterize an allosteric mechanism for disrupting the antiapoptotic BH3 binding activity of MCL-1, informing a new strategy for disarming MCL-1 in cancer. PMID:27159560

  1. Allosteric regulation of rhomboid intramembrane proteolysis

    PubMed Central

    Arutyunova, Elena; Panwar, Pankaj; Skiba, Pauline M; Gale, Nicola; Mak, Michelle W; Lemieux, M Joanne

    2014-01-01

    Proteolysis within the lipid bilayer is poorly understood, in particular the regulation of substrate cleavage. Rhomboids are a family of ubiquitous intramembrane serine proteases that harbour a buried active site and are known to cleave transmembrane substrates with broad specificity. In vitro gel and Förster resonance energy transfer (FRET)-based kinetic assays were developed to analyse cleavage of the transmembrane substrate psTatA (TatA from Providencia stuartii). We demonstrate significant differences in catalytic efficiency (kcat/K0.5) values for transmembrane substrate psTatA (TatA from Providencia stuartii) cleavage for three rhomboids: AarA from P. stuartii, ecGlpG from Escherichia coli and hiGlpG from Haemophilus influenzae demonstrating that rhomboids specifically recognize this substrate. Furthermore, binding of psTatA occurs with positive cooperativity. Competitive binding studies reveal an exosite-mediated mode of substrate binding, indicating allostery plays a role in substrate catalysis. We reveal that exosite formation is dependent on the oligomeric state of rhomboids, and when dimers are dissociated, allosteric substrate activation is not observed. We present a novel mechanism for specific substrate cleavage involving several dynamic processes including positive cooperativity and homotropic allostery for this interesting class of intramembrane proteases. PMID:25009246

  2. Allosteric Inhibition of Human Immunodeficiency Virus Integrase

    PubMed Central

    Gupta, Kushol; Brady, Troy; Dyer, Benjamin M.; Malani, Nirav; Hwang, Young; Male, Frances; Nolte, Robert T.; Wang, Liping; Velthuisen, Emile; Jeffrey, Jerry; Van Duyne, Gregory D.; Bushman, Frederic D.

    2014-01-01

    HIV-1 replication in the presence of antiviral agents results in evolution of drug-resistant variants, motivating the search for additional drug classes. Here we report studies of GSK1264, which was identified as a compound that disrupts the interaction between HIV-1 integrase (IN) and the cellular factor lens epithelium-derived growth factor (LEDGF)/p75. GSK1264 displayed potent antiviral activity and was found to bind at the site occupied by LEDGF/p75 on IN by x-ray crystallography. Assays of HIV replication in the presence of GSK1264 showed only modest inhibition of the early infection steps and little effect on integration targeting, which is guided by the LEDGF/p75·IN interaction. In contrast, inhibition of late replication steps was more potent. Particle production was normal, but particles showed reduced infectivity. GSK1264 promoted aggregation of IN and preformed LEDGF/p75·IN complexes, suggesting a mechanism of inhibition. LEDGF/p75 was not displaced from IN during aggregation, indicating trapping of LEDGF/p75 in aggregates. Aggregation assays with truncated IN variants revealed that a construct with catalytic and C-terminal domains of IN only formed an open polymer associated with efficient drug-induced aggregation. These data suggest that the allosteric inhibitors of IN are promising antiviral agents and provide new information on their mechanism of action. PMID:24904063

  3. Novel allosteric agonists of M1 muscarinic acetylcholine receptors induce brain region-specific responses that correspond with behavioral effects in animal models

    PubMed Central

    Digby, G.J.; Noetzel, M.J.; Bubser, M.; Utley, T.J.; Walker, A.G.; Byun, N.E.; Lebois, E.P.; Xiang, Z.; Sheffler, D.J.; Cho, H.P.; Davis, A.A.; Nemirovsky, N.E.; Mennenga, S.E.; Camp, B.W.; Bimonte-Nelson, H.A.; Bode, J.; Italiano, K.; Morrison, R.; Daniels, J.S.; Niswender, C.M.; Olive, M.F.; Lindsley, C.W.; Jones, C.K.; Conn, P.J.

    2012-01-01

    M1 muscarinic acetylcholine receptors (mAChRs) represent a viable target for treatment of multiple disorders of the central nervous system (CNS) including Alzheimer’s disease and schizophrenia. The recent discovery of highly selective allosteric agonists of M1 receptors has provided a major breakthrough in developing a viable approach for discovery of novel therapeutic agents that target these receptors. Here, we describe the characterization of two novel M1 allosteric agonists VU0357017 and VU0364572 that display profound differences in their efficacy in activating M1 coupling to different signaling pathways including Ca++ and β-arrestin responses. Interestingly, the ability of these agents to differentially activate coupling of M1 to specific signaling pathways leads to selective actions on some but not all M1-mediated responses in brain circuits. These novel M1 allosteric agonists induced robust electrophysiological effects in rat hippocampal slices but showed lower efficacy in striatum and no measureable effects on M1-mediated responses in medial prefrontal cortical pyramidal cells in mice. Consistent with these actions, both M1 agonists enhanced acquisition of hippocampal-dependent cognitive function but did not reverse amphetamine-induced hyperlocomotion in rats. Together, these data reveal that M1 allosteric agonists can differentially regulate coupling of M1 to different signaling pathways and this can dramatically alter the actions of these compounds on specific brain circuits important for learning and memory and psychosis. PMID:22723693

  4. Entropic mechanism of large fluctuation in allosteric transition.

    PubMed

    Itoh, Kazuhito; Sasai, Masaki

    2010-04-27

    A statistical mechanical model of allosteric transitions in proteins is developed by extending the structure-based model of protein folding to cases of multiple native conformations. The partition function is calculated exactly within the model and the free-energy surface reflecting allostery is derived. This approach is applied to an example protein, the receiver domain of the bacterial enhancer-binding protein NtrC. The model predicts the large entropy associated with a combinatorial number of preexisting transition routes. This large entropy lowers the free-energy barrier of the allosteric transition, which explains the large structural fluctuation observed in the NMR data of NtrC. The global allosteric transformation of NtrC is explained by the shift of preexisting distribution of conformations upon phosphorylation, but the local structural adjustment around the phosphorylation site is explained by the complementary induced-fit mechanism. Structural disordering accompanied by fluctuating interactions specific to two allosteric conformations underlies a large number of routes of allosteric transition. PMID:20385843

  5. Allosteric Coupling in the Bacterial Adhesive Protein FimH*

    PubMed Central

    Rodriguez, Victoria B.; Kidd, Brian A.; Interlandi, Gianluca; Tchesnokova, Veronika; Sokurenko, Evgeni V.; Thomas, Wendy E.

    2013-01-01

    The protein FimH is expressed by the majority of commensal and uropathogenic strains of Escherichia coli on the tips of type 1 fimbriae and mediates adhesion via a catch bond to its ligand mannose. Crystal structures of FimH show an allosteric conformational change, but it remains unclear whether all of the observed structural differences are part of the allosteric mechanism. Here we use the protein structural analysis tool RosettaDesign combined with human insight to identify and synthesize 10 mutations in four regions that we predicted would stabilize one of the conformations of that region. The function of each variant was characterized by measuring binding to the ligand mannose, whereas the allosteric state was determined using a conformation-specific monoclonal antibody. These studies demonstrated that each region investigated was indeed part of the FimH allosteric mechanism. However, the studies strongly suggested that some regions were more tightly coupled to mannose binding and others to antibody binding. In addition, we identified many FimH variants that appear locked in the low affinity state. Knowledge of regulatory sites outside the active and effector sites as well as the ability to make FimH variants locked in the low affinity state may be crucial to the future development of novel antiadhesive and antimicrobial therapies using allosteric regulation to inhibit FimH. PMID:23821547

  6. Activation of Nanoscale Allosteric Protein Domain Motion Revealed by Neutron Spin Echo Spectroscopy

    PubMed Central

    Farago, Bela; Li, Jianquan; Cornilescu, Gabriel; Callaway, David J.E.; Bu, Zimei

    2010-01-01

    NHERF1 is a multidomain scaffolding protein that assembles signaling complexes, and regulates the cell surface expression and endocytic recycling of a variety of membrane proteins. The ability of the two PDZ domains in NHERF1 to assemble protein complexes is allosterically modulated by the membrane-cytoskeleton linker protein ezrin, whose binding site is located as far as 110 Ångstroms away from the PDZ domains. Here, using neutron spin echo (NSE) spectroscopy, selective deuterium labeling, and theoretical analyses, we reveal the activation of interdomain motion in NHERF1 on nanometer length-scales and on submicrosecond timescales upon forming a complex with ezrin. We show that a much-simplified coarse-grained model suffices to describe interdomain motion of a multidomain protein or protein complex. We expect that future NSE experiments will benefit by exploiting our approach of selective deuteration to resolve the specific domain motions of interest from a plethora of global translational and rotational motions. Our results demonstrate that the dynamic propagation of allosteric signals to distal sites involves changes in long-range coupled domain motions on submicrosecond timescales, and that these coupled motions can be distinguished and characterized by NSE. PMID:21081097

  7. Seven Transmembrane Receptors as Shapeshifting Proteins: The Impact of Allosteric Modulation and Functional Selectivity on New Drug Discovery

    PubMed Central

    Miller, Laurence J.

    2010-01-01

    It is useful to consider seven transmembrane receptors (7TMRs) as disordered proteins able to allosterically respond to a number of binding partners. Considering 7TMRs as allosteric systems, affinity and efficacy can be thought of in terms of energy flow between a modulator, conduit (the receptor protein), and a number of guests. These guests can be other molecules, receptors, membrane-bound proteins, or signaling proteins in the cytosol. These vectorial flows of energy can yield standard canonical guest allostery (allosteric modification of drug effect), effects along the plane of the cell membrane (receptor oligomerization), or effects directed into the cytosol (differential signaling as functional selectivity). This review discusses these apparently diverse pharmacological effects in terms of molecular dynamics and protein ensemble theory, which tends to unify 7TMR behavior toward cells. Special consideration will be given to functional selectivity (biased agonism and biased antagonism) in terms of mechanism of action and potential therapeutic application. The explosion of technology that has enabled observation of diverse 7TMR behavior has also shown how drugs can have multiple (pluridimensional) efficacies and how this can cause paradoxical drug classification and nomenclatures. PMID:20392808

  8. Agonists and allosteric modulators of the calcium-sensing receptor and their therapeutic applications.

    PubMed

    Saidak, Zuzana; Brazier, Michel; Kamel, Saïd; Mentaverri, Romuald

    2009-12-01

    The calcium-sensing receptor (CaR) belongs to the G protein-coupled receptor superfamily, with a characteristic structure consisting of seven transmembrane helices, an intracellular C-terminal and an extracellular N terminal domain. The primary physiological function of the CaR is the maintenance of constant blood Ca2+ levels, as a result of its ability to sense very small changes in extracellular Ca2+ (Ca2+(o)). Nevertheless, in addition to being expressed in tissues involved in Ca2+(o) homeostasis, the CaR is also expressed in tissues not involved in mineral homeostasis, suggestive of additional physiological functions. Numerous agonists and modulators of the CaR are now known in addition to Ca2+(o), including various divalent and trivalent cations, aromatic l-amino acids, polyamines, and aminoglycoside antibiotics. The signaling of the CaR is also regulated by extracellular pH and ionic strength. The activated CaR couples mainly to the phospholipase Cbeta and extracellular signal-regulated kinase 1/2 signaling pathways, and it decreases intracellular cAMP levels, leading to various physiological effects. The recent identification of synthetic allosteric modulators of the CaR has opened up a new field of research possibilities. Calcimimetics and calcilytics, which increase and decrease agonist signaling via the CaR, respectively, may facilitate the manipulation of the CaR and thus aid in further investigations of its precise signaling. These allosteric modulators, as well as strontium, have been demonstrated to have therapeutic potential for the treatment of disorders involving the CaR. This review discusses the various agonists and modulators of the CaR, differences in their binding and signaling, and their roles as therapeutics in various diseases. PMID:19779033

  9. Structure, Dynamics, and Allosteric Potential of Ionotropic Glutamate Receptor N-Terminal Domains

    PubMed Central

    Krieger, James; Bahar, Ivet; Greger, Ingo H.

    2015-01-01

    Ionotropic glutamate receptors (iGluRs) are tetrameric cation channels that mediate synaptic transmission and plasticity. They have a unique modular architecture with four domains: the intracellular C-terminal domain (CTD) that is involved in synaptic targeting, the transmembrane domain (TMD) that forms the ion channel, the membrane-proximal ligand-binding domain (LBD) that binds agonists such as L-glutamate, and the distal N-terminal domain (NTD), whose function is the least clear. The extracellular portion, comprised of the LBD and NTD, is loosely arranged, mediating complex allosteric regulation and providing a rich target for drug development. Here, we briefly review recent work on iGluR NTD structure and dynamics, and further explore the allosteric potential for the NTD in AMPA-type iGluRs using coarse-grained simulations. We also investigate mechanisms underlying the established NTD allostery in NMDA-type iGluRs, as well as the fold-related metabotropic glutamate and GABAB receptors. We show that the clamshell motions intrinsically favored by the NTD bilobate fold are coupled to dimeric and higher-order rearrangements that impact the iGluR LBD and ultimately the TMD. Finally, we explore the dynamics of intact iGluRs and describe how it might affect receptor operation in a synaptic environment. PMID:26255587

  10. An allosteric inhibitor of substrate recognition by the SCF[superscript Cdc4] ubiquitin ligase

    SciTech Connect

    Orlicky, Stephen; Tang, Xiaojing; Neduva, Victor; Elowe, Nadine; Brown, Eric D.; Sicheri, Frank; Tyers, Mike

    2010-09-17

    The specificity of SCF ubiquitin ligase-mediated protein degradation is determined by F-box proteins. We identified a biplanar dicarboxylic acid compound, called SCF-I2, as an inhibitor of substrate recognition by the yeast F-box protein Cdc4 using a fluorescence polarization screen to monitor the displacement of a fluorescein-labeled phosphodegron peptide. SCF-I2 inhibits the binding and ubiquitination of full-length phosphorylated substrates by SCF{sup Cdc4}. A co-crystal structure reveals that SCF-I2 inserts itself between the {beta}-strands of blades 5 and 6 of the WD40 propeller domain of Cdc4 at a site that is 25 {angstrom} away from the substrate binding site. Long-range transmission of SCF-I2 interactions distorts the substrate binding pocket and impedes recognition of key determinants in the Cdc4 phosphodegron. Mutation of the SCF-I2 binding site abrogates its inhibitory effect and explains specificity in the allosteric inhibition mechanism. Mammalian WD40 domain proteins may exhibit similar allosteric responsiveness and hence represent an extensive class of druggable target.

  11. Kerr nonlinearity mitigation in 5 × 28-GBd PDM 16-QAM signal transmission over a dispersion-uncompensated link with backward-pumped distributed Raman amplification.

    PubMed

    Sackey, Isaac; Da Ros, Francesco; Jazayerifar, Mahmoud; Richter, Thomas; Meuer, Christian; Nölle, Markus; Molle, Lutz; Peucheret, Christophe; Petermann, Klaus; Schubert, Colja

    2014-11-01

    We present experimental and numerical investigations of Kerr nonlinearity compensation in a 400-km standard single-mode fiber link with distributed Raman amplification with backward pumping. A dual-pump polarization-independent fiber-based optical parametric amplifier is used for mid-link spectral inversion of 5 × 28-GBd polarization-multiplexed 16-QAM signals. Signal quality factor (Q-factor) improvements of 1.1 dB and 0.8 dB were obtained in the cases of a single-channel and a five-channel wavelength-division multiplexing (WDM) system, respectively. The experimental results are compared to numerical simulations with good agreement. It is also shown with simulations that a maximum transmission reach of 2400 km enabled by the optical phase conjugator is possible for the WDM signal. PMID:25401887

  12. Targeting the Akt1 allosteric site to identify novel scaffolds through virtual screening.

    PubMed

    Yilmaz, Oya Gursoy; Olmez, Elif Ozkirimli; Ulgen, Kutlu O

    2014-02-01

    Preclinical data and tumor specimen studies report that AKT kinases are related to many human cancers. Therefore, identification and development of small molecule inhibitors targeting AKT and its signaling pathway can be therapeutic in treatment of cancer. Numerous studies report inhibitors that target the ATP-binding pocket in the kinase domains, but the similarity of this site, within the kinase family makes selectivity a major problem. The sequence identity amongst PH domains is significantly lower than that in kinase domains and developing more selective inhibitors is possible if PH domain is targeted. This in silico screening study is the first time report toward the identification of potential allosteric inhibitors expected to bind the cavity between kinase and PH domains of Akt1. Structural information of Akt1 was used to develop structure-based pharmacophore models comprising hydrophobic, acceptor, donor and ring features. The 3D structural information of previously identified allosteric Akt inhibitors obtained from literature was employed to develop a ligand-based pharmacophore model. Database was generated with drug like subset of ZINC and screening was performed based on 3D similarity to the selected pharmacophore hypotheses. Binding modes and affinities of the ligands were predicted by Glide software. Top scoring hits were further analyzed considering 2D similarity between the compounds, interactions with Akt1, fitness to pharmacophore models, ADME, druglikeness criteria and Induced-Fit docking. Using virtual screening methodologies, derivatives of 3-methyl-xanthine, quinoline-4-carboxamide and 2-[4-(cyclohexa-1,3-dien-1-yl)-1H-pyrazol-3-yl]phenol were proposed as potential leads for allosteric inhibition of Akt1. PMID:24291487

  13. Anisotropic energy flow and allosteric ligand binding in albumin

    PubMed Central

    Li, Guifeng; Magana, Donny; Dyer, R. Brian

    2014-01-01

    Allosteric interactions in proteins generally involve propagation of local structural changes through the protein to a remote site. Anisotropic energy transport is thought to couple the remote sites, but the nature of this process is poorly understood. Here, we report the relationship between energy flow through the structure of bovine serum albumin and allosteric interactions between remote ligand binding sites of the protein. Ultrafast infrared spectroscopy is used to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic and anisotropic energy flow through the protein structure following input of thermal energy into the flexible ligand binding sites, without local heating of the rigid helix bundles that connect these sites. This efficient energy transport mechanism enables the allosteric propagation of binding energy through the connecting helix structures. PMID:24445265

  14. Current status of A1 adenosine receptor allosteric enhancers.

    PubMed

    Romagnoli, Romeo; Baraldi, Pier Giovanni; Moorman, Allan R; Borea, Pier Andrea; Varani, Katia

    2015-01-01

    Adenosine is an ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A1, A2A, A2B and A3 adenosine receptors (ARs). Allosteric enhancers to A1ARs may represent novel therapeutic agents because they increase the activity of these receptors by mediating a shift to their active form in the A1AR-G protein ternary complex. In this manner, they are able to amplify the action of endogenous adenosine, which is produced in high concentrations under conditions of metabolic stress. A1AR allosteric enhancers could be used as a justifiable alternative to the exogenous agonists that are characterized by receptor desensitization and downregulation. In this review, an analysis of some of the most interesting allosteric modulators of A1ARs has been reported. PMID:26144263

  15. SPACER: server for predicting allosteric communication and effects of regulation

    PubMed Central

    Goncearenco, Alexander; Mitternacht, Simon; Yong, Taipang; Eisenhaber, Birgit; Eisenhaber, Frank; Berezovsky, Igor N.

    2013-01-01

    The SPACER server provides an interactive framework for exploring allosteric communication in proteins with different sizes, degrees of oligomerization and function. SPACER uses recently developed theoretical concepts based on the thermodynamic view of allostery. It proposes easily tractable and meaningful measures that allow users to analyze the effect of ligand binding on the intrinsic protein dynamics. The server shows potential allosteric sites and allows users to explore communication between the regulatory and functional sites. It is possible to explore, for instance, potential effector binding sites in a given structure as targets for allosteric drugs. As input, the server only requires a single structure. The server is freely available at http://allostery.bii.a-star.edu.sg/. PMID:23737445

  16. Development of indole sulfonamides as cannabinoid receptor negative allosteric modulators.

    PubMed

    Greig, Iain R; Baillie, Gemma L; Abdelrahman, Mostafa; Trembleau, Laurent; Ross, Ruth A

    2016-09-15

    Existing CB1 negative allosteric modulators (NAMs) fall into a limited range of structural classes. In spite of the theoretical potential of CB1 NAMs, published in vivo studies have generally not been able to demonstrate the expected therapeutically-relevant CB1-mediated effects. Thus, a greater range of molecular tools are required to allow definitive elucidation of the effects of CB1 allosteric modulation. In this study, we show a novel series of indole sulfonamides. Compounds 5e and 6c (ABD1075) had potencies of 4 and 3nM respectively, and showed good oral exposure and CNS penetration, making them highly versatile tools for investigating the therapeutic potential of allosteric modulation of the cannabinoid system. PMID:27542310

  17. Anisotropic energy flow and allosteric ligand binding in albumin

    NASA Astrophysics Data System (ADS)

    Li, Guifeng; Magana, Donny; Dyer, R. Brian

    2014-01-01

    Allosteric interactions in proteins generally involve propagation of local structural changes through the protein to a remote site. Anisotropic energy transport is thought to couple the remote sites, but the nature of this process is poorly understood. Here, we report the relationship between energy flow through the structure of bovine serum albumin and allosteric interactions between remote ligand binding sites of the protein. Ultrafast infrared spectroscopy is used to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic and anisotropic energy flow through the protein structure following input of thermal energy into the flexible ligand binding sites, without local heating of the rigid helix bundles that connect these sites. This efficient energy transport mechanism enables the allosteric propagation of binding energy through the connecting helix structures.

  18. Shape shifting leads to small molecule allosteric drug discovery

    PubMed Central

    Lawrence, Sarah H.; Ramirez, Ursula D.; Tang, Lei; Fazliyev, Farit; Kundrat, Lenka; Markham, George D.; Jaffe, Eileen K.

    2009-01-01

    SUMMARY Enzymes that regulate their activity by modulating an equilibrium of alternate, non-additive, functionally distinct oligomeric assemblies (morpheeins) define a novel mode of allostery (Jaffe, TiBS 30:490-7, 2005). The oligomeric equilibrium for porphobilinogen synthase (PBGS) consists of high-activity octamers, low-activity hexamers, and two dimer conformations. A phylogenetically diverse allosteric site specific to hexamers is proposed as an inhibitor binding site. Inhibitor binding is predicted to draw the oligomeric equilibrium toward the low-activity hexamer. In silico docking enriched a selection from a small molecule library for compounds predicted to bind to this allosteric site. In vitro testing of selected compounds identified one compound whose inhibition mechanism is species-specific conversion of PBGS octamers to hexamers. We propose that this novel strategy for inhibitor discovery can be applied to other proteins that use the morpheein model for allosteric regulation. PMID:18559269

  19. A multi-channel low-power system-on-chip for single-unit recording and narrowband wireless transmission of neural signal.

    PubMed

    Bonfanti, A; Ceravolo, M; Zambra, G; Gusmeroli, R; Spinelli, A S; Lacaita, A L; Angotzi, G N; Baranauskas, G; Fadiga, L

    2010-01-01

    This paper reports a multi-channel neural recording system-on-chip (SoC) with digital data compression and wireless telemetry. The circuit consists of a 16 amplifiers, an analog time division multiplexer, an 8-bit SAR AD converter, a digital signal processor (DSP) and a wireless narrowband 400-MHz binary FSK transmitter. Even though only 16 amplifiers are present in our current die version, the whole system is designed to work with 64 channels demonstrating the feasibility of a digital processing and narrowband wireless transmission of 64 neural recording channels. A digital data compression, based on the detection of action potentials and storage of correspondent waveforms, allows the use of a 1.25-Mbit/s binary FSK wireless transmission. This moderate bit-rate and a low frequency deviation, Manchester-coded modulation are crucial for exploiting a narrowband wireless link and an efficient embeddable antenna. The chip is realized in a 0.35- εm CMOS process with a power consumption of 105 εW per channel (269 εW per channel with an extended transmission range of 4 m) and an area of 3.1 × 2.7 mm(2). The transmitted signal is captured by a digital TV tuner and demodulated by a wideband phase-locked loop (PLL), and then sent to a PC via an FPGA module. The system has been tested for electrical specifications and its functionality verified in in-vivo neural recording experiments. PMID:21096380

  20. RNA-mediated gene silencing signals are not graft transmissible from the rootstock to the scion in greenhouse-grown apple plants Malus sp.

    PubMed

    Flachowsky, Henryk; Tränkner, Conny; Szankowski, Iris; Waidmann, Sascha; Hanke, Magda-Viola; Treutter, Dieter; Fischer, Thilo C

    2012-01-01

    RNA silencing describes the sequence specific degradation of RNA targets. Silencing is a non-cell autonomous event that is graft transmissible in different plant species. The present study is the first report on systemic acquired dsRNA-mediated gene silencing of transgenic and endogenous gene sequences in a woody plant like apple. Transgenic apple plants overexpressing a hairpin gene construct of the gusA reporter gene were produced. These plants were used as rootstocks and grafted with scions of the gusA overexpressing transgenic apple clone T355. After grafting, we observed a reduction of the gusA gene expression in T355 scions in vitro, but not in T355 scions grown in the greenhouse. Similar results were obtained after silencing of the endogenous Mdans gene in apple that is responsible for anthocyanin biosynthesis. Subsequently, we performed grafting experiments with Mdans silenced rootstocks and red leaf scions of TNR31-35 in order to evaluate graft transmitted silencing of the endogenous Mdans. The results obtained suggested a graft transmission of silencing signals in in vitro shoots. In contrast, no graft transmission of dsRNA-mediated gene silencing signals was detectable in greenhouse-grown plants and in plants grown in an insect protection tent. PMID:22949844

  1. Discovery of a novel allosteric inhibitor-binding site in ERK5: comparison with the canonical kinase hinge ATP-binding site.

    PubMed

    Chen, Hongming; Tucker, Julie; Wang, Xiaotao; Gavine, Paul R; Phillips, Chris; Augustin, Martin A; Schreiner, Patrick; Steinbacher, Stefan; Preston, Marian; Ogg, Derek

    2016-05-01

    MAP kinases act as an integration point for multiple biochemical signals and are involved in a wide variety of cellular processes such as proliferation, differentiation, regulation of transcription and development. As a member of the MAP kinase family, ERK5 (MAPK7) is involved in the downstream signalling pathways of various cell-surface receptors, including receptor tyrosine kinases and G protein-coupled receptors. In the current study, five structures of the ERK5 kinase domain co-crystallized with ERK5 inhibitors are reported. Interestingly, three of the compounds bind at a novel allosteric binding site in ERK5, while the other two bind at the typical ATP-binding site. Binding of inhibitors at the allosteric site is accompanied by displacement of the P-loop into the ATP-binding site and is shown to be ATP-competitive in an enzymatic assay of ERK5 kinase activity. Kinase selectivity data show that the most potent allosteric inhibitor exhibits superior kinase selectivity compared with the two inhibitors that bind at the canonical ATP-binding site. An analysis of these structures and comparison with both a previously published ERK5-inhibitor complex structure (PDB entry 4b99) and the structures of three other kinases (CDK2, ITK and MEK) in complex with allosteric inhibitors are presented. PMID:27139631

  2. Discovery of a novel allosteric inhibitor-binding site in ERK5: comparison with the canonical kinase hinge ATP-binding site

    PubMed Central

    Chen, Hongming; Tucker, Julie; Wang, Xiaotao; Gavine, Paul R.; Phillips, Chris; Augustin, Martin A.; Schreiner, Patrick; Steinbacher, Stefan; Preston, Marian; Ogg, Derek

    2016-01-01

    MAP kinases act as an integration point for multiple biochemical signals and are involved in a wide variety of cellular processes such as proliferation, differentiation, regulation of transcription and development. As a member of the MAP kinase family, ERK5 (MAPK7) is involved in the downstream signalling pathways of various cell-surface receptors, including receptor tyrosine kinases and G protein-coupled receptors. In the current study, five structures of the ERK5 kinase domain co-crystallized with ERK5 inhibitors are reported. Interestingly, three of the compounds bind at a novel allosteric binding site in ERK5, while the other two bind at the typical ATP-binding site. Binding of inhibitors at the allosteric site is accompanied by displacement of the P-loop into the ATP-binding site and is shown to be ATP-competitive in an enzymatic assay of ERK5 kinase activity. Kinase selectivity data show that the most potent allosteric inhibitor exhibits superior kinase selectivity compared with the two inhibitors that bind at the canonical ATP-binding site. An analysis of these structures and comparison with both a previously published ERK5–inhibitor complex structure (PDB entry 4b99) and the structures of three other kinases (CDK2, ITK and MEK) in complex with allosteric inhibitors are presented. PMID:27139631

  3. Post-translational disulfide modifications in cell signaling--role of inter-protein, intra-protein, S-glutathionyl, and S-cysteaminyl disulfide modifications in signal transmission.

    PubMed

    O'Brian, Catherine A; Chu, Feng

    2005-05-01

    Cell signaling entails a host of post-translational modifications of effector-proteins. These modifications control signal transmission by regulating the activity, localization or half-life of the effector-protein. Prominent oxidative modifications induced by cell-signaling reactive oxygen species (ROS) are cysteinyl modifications such as S-nitrosylation, sulfenic acid and disulfide formation. Disulfides protect protein sulfhydryls against oxidative destruction and simultaneously influence cell signaling by engaging redox-regulatory sulfhydryls in effector-proteins. The types of disulfides implicated in signaling span (1) protein S-glutathionylation, e.g. as a novel mode of Ras activation through S-glutathionylation at Cys-118 in response to a hydrogen-peroxide burst, (2) intra-protein disulfides, e.g. in the regulation of the stability of the protein phosphatase Cdc25C by hydrogen-peroxide, (3) inter-protein disulfides, e.g. in the hydrogen peroxide-mediated inactivation of receptor protein-tyrosine phosphatase alpha (RPTPalpha) by dimerization and (4) protein S-cysteaminylation by cystamine. Cystamine is a byproduct of pantetheinase-catalyzed pantothenic acid recycling from pantetheine for biosynthesis of Coenzyme A (CoA), a ubiquitous and metabolically indispensable cofactor. Cystamine inactivates protein kinase C-epsilon (PKCepsilon), gamma-glutamylcysteine synthetase and tissue transglutaminase by S-cysteaminylation-triggered mechanisms. The importance of protein S-cysteaminylation in signal transmission in vivo is evident from the ability of cystamine administration to rescue the intestinal inflammatory-response deficit of pantetheinase knockout mice. These mice lack the predominant epithelial pantetheinase isoform and have sharply reduced levels of cystamine/cysteamine in epithelial tissues. In addition, intraperitoneal administration of cystamine significantly delays neurodegenerative pathogenesis in a Huntington's disease mouse model. Thus, cystamine may

  4. Allosteric mechanism of water channel gating by Ca2+–calmodulin

    PubMed Central

    Reichow, Steve L.; Clemens, Daniel M.; Freites, J. Alfredo; Németh-Cahalan, Karin L.; Heyden, Matthias; Tobias, Douglas J.; Hall, James E.; Gonen, Tamir

    2013-01-01

    Calmodulin (CaM) is a universal regulatory protein that communicates the presence of calcium to its molecular targets and correspondingly modulates their function. This key signaling protein is important for controlling the activity of hundreds of membrane channels and transporters. However, our understanding of the structural mechanisms driving CaM regulation of full-length membrane proteins has remained elusive. In this study, we determined the pseudo-atomic structure of full-length mammalian aquaporin-0 (AQP0, Bos Taurus) in complex with CaM using electron microscopy to understand how this signaling protein modulates water channel function. Molecular dynamics and functional mutation studies reveal how CaM binding inhibits AQP0 water permeability by allosterically closing the cytoplasmic gate of AQP0. Our mechanistic model provides new insight, only possible in the context of the fully assembled channel, into how CaM regulates multimeric channels by facilitating cooperativity between adjacent subunits. PMID:23893133

  5. Intestinal Epithelial Toll-Like Receptor 4 Signaling Affects Epithelial Function and Colonic Microbiota and Promotes a Risk for Transmissible Colitis

    PubMed Central

    Dheer, Rishu; Santaolalla, Rebeca; Davies, Julie M.; Lang, Jessica K.; Phillips, Matthew C.; Pastorini, Cristhine; Vazquez-Pertejo, Maria T.

    2016-01-01

    Evidence obtained from gene knockout studies supports the role of Toll-like receptor 4 (TLR4) in intestinal inflammation and microbiota recognition. Increased epithelial TLR4 expression is observed in patients with inflammatory bowel disease. However, little is known of the effect of increased TLR4 signaling on intestinal homeostasis. Here, we examined the effect of increased TLR4 signaling on epithelial function and microbiota by using transgenic villin-TLR4 mice that overexpress TLR4 in the intestinal epithelium. Our results revealed that villin-TLR4 mice are characterized by increases in the density of mucosa-associated bacteria and bacterial translocation. Furthermore, increased epithelial TLR4 signaling was associated with an impaired epithelial barrier, altered expression of antimicrobial peptide genes, and altered epithelial cell differentiation. The composition of the colonic luminal and mucosa-associated microbiota differed between villin-TLR4 and wild-type (WT) littermates. Interestingly, WT mice cohoused with villin-TLR4 mice displayed greater susceptibility to acute colitis than singly housed WT mice did. The results of this study suggest that epithelial TLR4 expression shapes the microbiota and affects the functional properties of the epithelium. The changes in the microbiota induced by increased epithelial TLR4 signaling are transmissible and exacerbate dextran sodium sulfate-induced colitis. Together, our findings imply that host innate immune signaling can modulate intestinal bacteria and ultimately the host's susceptibility to colitis. PMID:26755160

  6. Intestinal Epithelial Toll-Like Receptor 4 Signaling Affects Epithelial Function and Colonic Microbiota and Promotes a Risk for Transmissible Colitis.

    PubMed

    Dheer, Rishu; Santaolalla, Rebeca; Davies, Julie M; Lang, Jessica K; Phillips, Matthew C; Pastorini, Cristhine; Vazquez-Pertejo, Maria T; Abreu, Maria T

    2016-03-01

    Evidence obtained from gene knockout studies supports the role of Toll-like receptor 4 (TLR4) in intestinal inflammation and microbiota recognition. Increased epithelial TLR4 expression is observed in patients with inflammatory bowel disease. However, little is known of the effect of increased TLR4 signaling on intestinal homeostasis. Here, we examined the effect of increased TLR4 signaling on epithelial function and microbiota by using transgenic villin-TLR4 mice that overexpress TLR4 in the intestinal epithelium. Our results revealed that villin-TLR4 mice are characterized by increases in the density of mucosa-associated bacteria and bacterial translocation. Furthermore, increased epithelial TLR4 signaling was associated with an impaired epithelial barrier, altered expression of antimicrobial peptide genes, and altered epithelial cell differentiation. The composition of the colonic luminal and mucosa-associated microbiota differed between villin-TLR4 and wild-type (WT) littermates. Interestingly, WT mice cohoused with villin-TLR4 mice displayed greater susceptibility to acute colitis than singly housed WT mice did. The results of this study suggest that epithelial TLR4 expression shapes the microbiota and affects the functional properties of the epithelium. The changes in the microbiota induced by increased epithelial TLR4 signaling are transmissible and exacerbate dextran sodium sulfate-induced colitis. Together, our findings imply that host innate immune signaling can modulate intestinal bacteria and ultimately the host's susceptibility to colitis. PMID:26755160

  7. Facilitation of corticostriatal transmission following pharmacological inhibition of striatal phosphodiesterase 10A: role of nitric oxide-soluble guanylyl cyclase-cGMP signaling pathways.

    PubMed

    Padovan-Neto, Fernando E; Sammut, Stephen; Chakroborty, Shreaya; Dec, Alexander M; Threlfell, Sarah; Campbell, Peter W; Mudrakola, Vishnu; Harms, John F; Schmidt, Christopher J; West, Anthony R

    2015-04-01

    The striatum contains a rich variety of cyclic nucleotide phosphodiesterases (PDEs), which play a critical role in the regulation of cAMP and cGMP signaling. The dual-substrate enzyme PDE10A is the most highly expressed PDE in striatal medium-sized spiny neurons (MSNs) with low micromolar affinity for both cyclic nucleotides. Previously, we have shown that systemic and local administration of the selective PDE10A inhibitor TP-10 potently increased the responsiveness of MSNs to cortical stimulation. However, the signaling mechanisms underlying PDE10A inhibitor-induced changes in corticostriatal transmission are only partially understood. The current studies assessed the respective roles of cAMP and cGMP in the above effects using soluble guanylyl cyclase (sGC) or adenylate cyclase (AC) specific inhibitors. Cortically evoked spike activity was monitored in urethane-anesthetized rats using in vivo extracellular recordings performed proximal to a microdialysis probe during local infusion of vehicle, the selective sGC inhibitor ODQ, or the selective AC inhibitor SQ 22536. Systemic administration of TP-10 (3.2 mg/kg) robustly increased cortically evoked spike activity in a manner that was blocked following intrastriatal infusion of ODQ (50 μm). The effects of TP-10 on evoked activity were due to accumulation of cGMP, rather than cAMP, as the AC inhibitor SQ was without effect. Consistent with these observations, studies in neuronal NO synthase (nNOS) knock-out (KO) mice confirmed that PDE10A operates downstream of nNOS to limit cGMP production and excitatory corticostriatal transmission. Thus, stimulation of PDE10A acts to attenuate corticostriatal transmission in a manner largely dependent on effects directed at the NO-sGC-cGMP signaling cascade. PMID:25855188

  8. Development of allosteric modulators of GPCRs for treatment of CNS disorders

    PubMed Central

    Nickols, Hilary Highfield; Conn, P. Jeffrey

    2013-01-01

    The discovery of allosteric modulators of G protein-coupled receptors (GPCRs) provides a promising new strategy with potential for developing novel treatments for a variety of central nervous system (CNS) disorders. Traditional drug discovery efforts targeting GPCRs have focused on developing ligands for orthosteric sites which bind endogenous ligands. Allosteric modulators target a site separate from the orthosteric site to modulate receptor function. These allosteric agents can either potentiate (positive allosteric modulator, PAM) or inhibit (negative allosteric modulator, NAM) the receptor response and often provide much greater subtype selectivity than do orthosteric ligands for the same receptors. Experimental evidence has revealed more nuanced pharmacological modes of action of allosteric modulators, with some PAMs showing allosteric agonism in combination with positive allosteric modulation in response to endogenous ligand (ago-potentiators) as well as “bitopic” ligands that interact with both the allosteric and orthosteric sites. Drugs targeting the allosteric site allow for increased drug selectivity and potentially decreased adverse side effects. Promising evidence has demonstrated potential utility of a number of allosteric modulators of GPCRs in multiple CNS disorders, including neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease, as well as psychiatric or neurobehavioral diseases such as anxiety, schizophrenia, and addiction. PMID:24076101

  9. A Novel Allosteric Activator of Free Fatty Acid 2 Receptor Displays Unique Gi-functional Bias*

    PubMed Central

    Bolognini, Daniele; Moss, Catherine E.; Nilsson, Karolina; Petersson, Annika U.; Donnelly, Iona; Sergeev, Eugenia; König, Gabriele M.; Kostenis, Evi; Kurowska-Stolarska, Mariola; Miller, Ashley; Dekker, Niek; Tobin, Andrew B.

    2016-01-01

    The short chain fatty acid receptor FFA2 is able to stimulate signaling via both Gi- and Gq/G11-promoted pathways. These pathways are believed to control distinct physiological end points but FFA2 receptor ligands appropriate to test this hypothesis have been lacking. Herein, we characterize AZ1729, a novel FFA2 regulator that acts as a direct allosteric agonist and as a positive allosteric modulator, increasing the activity of the endogenously produced short chain fatty acid propionate in Gi-mediated pathways, but not at those transduced by Gq/G11. Using AZ1729 in combination with direct inhibitors of Gi and Gq/G11 family G proteins demonstrated that although both arms contribute to propionate-mediated regulation of phospho-ERK1/2 MAP kinase signaling in FFA2-expressing 293 cells, the Gq/G11-mediated pathway is predominant. We extend these studies by employing AZ1729 to dissect physiological FFA2 signaling pathways. The capacity of AZ1729 to act at FFA2 receptors to inhibit β-adrenoreceptor agonist-promoted lipolysis in primary mouse adipocytes and to promote chemotaxis of isolated human neutrophils confirmed these as FFA2 processes mediated by Gi signaling, whereas, in concert with blockade by the Gq/G11 inhibitor FR900359, the inability of AZ1729 to mimic or regulate propionate-mediated release of GLP-1 from mouse colonic preparations defined this physiological response as an end point transduced via activation of Gq/G11. PMID:27385588

  10. Fluorescence Polarization Screening Assays for Small Molecule Allosteric Modulators of ABL Kinase Function

    PubMed Central

    Grover, Prerna; Shi, Haibin; Baumgartner, Matthew; Camacho, Carlos J.; Smithgall, Thomas E.

    2015-01-01

    The ABL protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and contributes to several forms of cancer. The kinase activity of ABL is repressed by intramolecular interactions involving its regulatory Ncap, SH3 and SH2 domains. Small molecules that allosterically regulate ABL kinase activity through its non-catalytic domains may represent selective probes of ABL function. Here we report a screening assay for chemical modulators of ABL kinase activity that target the regulatory interaction of the SH3 domain with the SH2-kinase linker. This fluorescence polarization (FP) assay is based on a purified recombinant ABL protein consisting of the N-cap, SH3 and SH2 domains plus the SH2-kinase linker (N32L protein) and a short fluorescein-labeled probe peptide that binds to the SH3 domain. In assay development experiments, we found that the probe peptide binds to the recombinant ABL N32L protein in vitro, producing a robust FP signal that can be competed with an excess of unlabeled peptide. The FP signal is not observed with control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved drugs identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays showed that one of these hit compounds, the antithrombotic drug dipyridamole, enhances ABL kinase activity in vitro to a greater extent than the previously described ABL agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates ABL by disrupting this regulatory interaction. These results show that screening assays based on the non-catalytic domains of ABL can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery for this important

  11. A Novel Allosteric Activator of Free Fatty Acid 2 Receptor Displays Unique Gi-functional Bias.

    PubMed

    Bolognini, Daniele; Moss, Catherine E; Nilsson, Karolina; Petersson, Annika U; Donnelly, Iona; Sergeev, Eugenia; König, Gabriele M; Kostenis, Evi; Kurowska-Stolarska, Mariola; Miller, Ashley; Dekker, Niek; Tobin, Andrew B; Milligan, Graeme

    2016-09-01

    The short chain fatty acid receptor FFA2 is able to stimulate signaling via both Gi- and Gq/G11-promoted pathways. These pathways are believed to control distinct physiological end points but FFA2 receptor ligands appropriate to test this hypothesis have been lacking. Herein, we characterize AZ1729, a novel FFA2 regulator that acts as a direct allosteric agonist and as a positive allosteric modulator, increasing the activity of the endogenously produced short chain fatty acid propionate in Gi-mediated pathways, but not at those transduced by Gq/G11 Using AZ1729 in combination with direct inhibitors of Gi and Gq/G11 family G proteins demonstrated that although both arms contribute to propionate-mediated regulation of phospho-ERK1/2 MAP kinase signaling in FFA2-expressing 293 cells, the Gq/G11-mediated pathway is predominant. We extend these studies by employing AZ1729 to dissect physiological FFA2 signaling pathways. The capacity of AZ1729 to act at FFA2 receptors to inhibit β-adrenoreceptor agonist-promoted lipolysis in primary mouse adipocytes and to promote chemotaxis of isolated human neutrophils confirmed these as FFA2 processes mediated by Gi signaling, whereas, in concert with blockade by the Gq/G11 inhibitor FR900359, the inability of AZ1729 to mimic or regulate propionate-mediated release of GLP-1 from mouse colonic preparations defined this physiological response as an end point transduced via activation of Gq/G11. PMID:27385588

  12. BDNF up-regulates evoked GABAergic transmission in developing hippocampus by potentiating presynaptic N- and P/Q-type Ca2+ channels signalling.

    PubMed

    Baldelli, P; Novara, M; Carabelli, V; Hernández-Guijo, J M; Carbone, E

    2002-12-01

    Chronic application of brain-derived neurotrophic factor (BDNF) induces new selective synthesis of non-L-type Ca2+ channels (N, P/Q, R) at the soma of cultured hippocampal neurons. As N- and P/Q-channels support neurotransmitter release in the hippocampus, this suggests that BDNF-treatment may enhance synaptic transmission by increasing the expression of presynaptic Ca2+ channels as well. To address this issue we studied the long-term effects of BDNF on miniature and stimulus-evoked GABAergic transmission in rat embryo hippocampal neurons. We found that BDNF increased the frequency of miniature currents (mIPSCs) by approximately 40%, with little effects on their amplitude. BDNF nearly doubled the size of evoked postsynaptic currents (eIPSCs) with a marked increase of paired-pulse depression, which is indicative of a major increase in presynaptic activity. The potentiation of eIPSCs was more relevant during the first two weeks in culture, when GABAergic transmission is depolarizing. BDNF action was mediated by TrkB-receptors and had no effects on: (i) the amplitude and dose-response of GABA-evoked IPSCs and (ii) the number of GABA(A) receptor clusters and the total functioning synapses, suggesting that the neurotrophin unlikely acted postsynaptically. In line with this, BDNF affected the contribution of voltage-gated Ca2+ channels mediating evoked GABAergic transmission. BDNF drastically increased the fraction of evoked IPSCs supported by N- and P/Q-channels while it decreased the contribution associated with R- and L-types. This selective action resembles the previously observed up-regulatory effects of BDNF on somatic Ca2+ currents in developing hippocampus, suggesting that potentiation of presynaptic N- and P/Q-channel signalling belongs to a manifold mechanism by which BDNF increases the efficiency of stimulus-evoked GABAergic transmission. PMID:12492424

  13. Allosteric Activation of a G Protein-coupled Receptor with Cell-penetrating Receptor Mimetics*

    PubMed Central

    Zhang, Ping; Leger, Andrew J.; Baleja, James D.; Rana, Rajashree; Corlin, Tiffany; Nguyen, Nga; Koukos, Georgios; Bohm, Andrew; Covic, Lidija; Kuliopulos, Athan

    2015-01-01

    G protein-coupled receptors (GPCRs) are remarkably versatile signaling systems that are activated by a large number of different agonists on the outside of the cell. However, the inside surface of the receptors that couple to G proteins has not yet been effectively modulated for activity or treatment of diseases. Pepducins are cell-penetrating lipopeptides that have enabled chemical and physical access to the intracellular face of GPCRs. The structure of a third intracellular (i3) loop agonist, pepducin, based on protease-activated receptor-1 (PAR1) was solved by NMR and found to closely resemble the i3 loop structure predicted for the intact receptor in the on-state. Mechanistic studies revealed that the pepducin directly interacts with the intracellular H8 helix region of PAR1 and allosterically activates the receptor through the adjacent (D/N)PXXYYY motif through a dimer-like mechanism. The i3 pepducin enhances PAR1/Gα subunit interactions and induces a conformational change in fluorescently labeled PAR1 in a very similar manner to that induced by thrombin. As pepducins can potentially be made to target any GPCR, these data provide insight into the identification of allosteric modulators to this major drug target class. PMID:25934391

  14. An allosteric model for heterogeneous receptor complexes: Understanding bacterial chemotaxis responses to multiple stimuli

    PubMed Central

    Mello, Bernardo A.; Tu, Yuhai

    2005-01-01

    The classical Monod-Wyman-Changeux model for homogeneous allosteric protein complex is generalized in this article to model the responses of heterogeneous receptor complexes to multiple types of ligand stimulus. We show that the recent in vivo experimental data of Escherichia coli chemotaxis responses for mutant strains with different expression levels of the chemo-receptors to different types of stimulus [Sourjik, V. & Berg, H. C. (2004) Nature 428, 437–441] all can be explained consistently within this generalized Monod-Wyman-Changeux model. Based on the model and the existing data, responses of all of the strains (studied in this article) to the presence of any combinations of ligand (Ser and MeAsp) concentrations are predicted quantitatively for future experimental verification. Through modeling the in vivo response data, our study reveals important information about the properties of different types of individual receptors, as well as the composition of the cluster. The energetic contribution of the nonligand binding, cytoplasmic parts of the cluster, such as CheA and CheW, is also discussed. The generalized allosteric model provides a consistent framework in understanding signal integration and differentiation in bacterial chemotaxis. It should also be useful for studying the functions of other heterogeneous receptor complexes. PMID:16293695

  15. Engineering and optimization of an allosteric biosensor protein for peroxisome proliferator-activated receptor γ ligands.

    PubMed

    Li, Jingjing; Gierach, Izabela; Gillies, Alison R; Warden, Charles D; Wood, David W

    2011-11-15

    The peroxisome proliferator-activated receptor gamma (PPARγ or PPARG) belongs to the nuclear receptor superfamily, and is a potential drug target for a variety of diseases. In this work, we constructed a series of bacterial biosensors for the identification of functional PPARγ ligands. These sensors entail modified Escherichia coli cells carrying a four-domain fusion protein, comprised of the PPARγ ligand binding domain (LBD), an engineered mini-intein domain, the E. coli maltose binding protein (MBD), and a thymidylate synthase (TS) reporter enzyme. E. coli cells expressing this protein exhibit hormone ligand-dependent growth phenotypes. Unlike our published estrogen (ER) and thyroid receptor (TR) biosensors, the canonical PPARγ biosensor cells displayed pronounced growth in the absence of ligand. They were able to distinguish agonists and antagonists, however, even in the absence of agonist. To improve ligand sensitivity of this sensor, we attempted to engineer and optimize linker peptides flanking the PPARγ LBD insertion point. Truncation of the original linkers led to decreased basal growth and significantly enhanced ligand sensitivity of the PPARγ sensor, while substitution of the native linkers with optimized G(4)S (Gly-Gly-Gly-Gly-Ser) linkers further increased the sensitivity. Our studies demonstrate that the properties of linkers, especially the C-terminal linker, greatly influence the efficiency and fidelity of the allosteric signal induced by ligand binding. Our work also suggests an approach to increase allosteric behavior in this multidomain sensor protein, without modification of the functional LBD. PMID:21893405

  16. Allosteric Activation of Bacterial Response Regulators: the Role of the Cognate Histidine Kinase Beyond Phosphorylation

    PubMed Central

    Trajtenberg, Felipe; Albanesi, Daniela; Ruétalo, Natalia; Botti, Horacio; Mechaly, Ariel E.; Nieves, Marcos; Aguilar, Pablo S.; Cybulski, Larisa; Larrieux, Nicole; de Mendoza, Diego

    2014-01-01

    ABSTRACT Response regulators are proteins that undergo transient phosphorylation, connecting specific signals to adaptive responses. Remarkably, the molecular mechanism of response regulator activation remains elusive, largely because of the scarcity of structural data on multidomain response regulators and histidine kinase/response regulator complexes. We now address this question by using a combination of crystallographic data and functional analyses in vitro and in vivo, studying DesR and its cognate sensor kinase DesK, a two-component system that controls membrane fluidity in Bacillus subtilis. We establish that phosphorylation of the receiver domain of DesR is allosterically coupled to two distinct exposed surfaces of the protein, controlling noncanonical dimerization/tetramerization, cooperative activation, and DesK binding. One of these surfaces is critical for both homodimerization- and kinase-triggered allosteric activations. Moreover, DesK induces a phosphorylation-independent activation of DesR in vivo, uncovering a novel and stringent level of specificity among kinases and regulators. Our results support a model that helps to explain how response regulators restrict phosphorylation by small-molecule phosphoryl donors, as well as cross talk with noncognate sensors. PMID:25406381

  17. A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors.

    PubMed

    Schmidt, Thomas; Ye, Feng; Situ, Alan J; An, Woojin; Ginsberg, Mark H; Ulmer, Tobias S

    2016-08-19

    In many families of cell surface receptors, a single transmembrane (TM) α-helix separates ecto- and cytosolic domains. A defined coupling of ecto- and TM domains must be essential to allosteric receptor regulation but remains little understood. Here, we characterize the linker structure, dynamics, and resulting ecto-TM domain coupling of integrin αIIb in model constructs and relate it to other integrin α subunits by mutagenesis. Cellular integrin activation assays subsequently validate the findings in intact receptors. Our results indicate a flexible yet carefully tuned ecto-TM coupling that modulates the signaling threshold of integrin receptors. Interestingly, a proline at the N-terminal TM helix border, termed NBP, is critical to linker flexibility in integrins. NBP is further predicted in 21% of human single-pass TM proteins and validated in cytokine receptors by the TM domain structure of the cytokine receptor common subunit β and its P441A-substituted variant. Thus, NBP is a conserved uncoupling motif of the ecto-TM domain transition and the degree of ecto-TM domain coupling represents an important parameter in the allosteric regulation of diverse cell surface receptors. PMID:27365391

  18. The positive allosteric GABAB receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice.

    PubMed

    Zemoura, Khaled; Ralvenius, William T; Malherbe, Pari; Benke, Dietmar

    2016-09-01

    Neuropathic pain is associated with impaired inhibitory control of spinal dorsal horn neurons, which are involved in processing pain signals. The metabotropic GABAB receptor is an important component of the inhibitory system and is highly expressed in primary nociceptors and intrinsic dorsal horn neurons to control their excitability. Activation of GABAB receptors with the orthosteric agonist baclofen effectively reliefs neuropathic pain but is associated with severe side effects that prevent its widespread application. The recently developed positive allosteric GABAB receptor modulators lack most of these side effects and are therefore promising drugs for the treatment of pain. Here we tested the high affinity positive allosteric modulator rac-BHFF for its ability to relief neuropathic pain induced by chronic constriction of the sciatic nerve in mice. rac-BHFF significantly increased the paw withdrawal threshold to mechanical stimulation in healthy mice, indicating an endogenous GABABergic tone regulating the sensitivity to mechanical stimuli. Surprisingly, rac-BHFF displayed no analgesic activity in neuropathic mice although GABAB receptor expression was not affected in the dorsal horn as shown by quantitative receptor autoradiography. However, activation of spinal GABAB receptors by intrathecal injection of baclofen reduced hyperalgesia and its analgesic effect was considerably potentiated by co-application of rac-BHFF. These results indicate that under conditions of neuropathic pain the GABAergic tone is too low to provide a basis for allosteric modulation of GABAB receptors. However, allosteric modulators would be well suited as an add-on to reduce the dose of baclofen required to achieve analgesia. PMID:27108932

  19. Identification and Quantification of a New Family of Peptide Endocannabinoids (Pepcans) Showing Negative Allosteric Modulation at CB1 Receptors*

    PubMed Central

    Bauer, Mark; Chicca, Andrea; Tamborrini, Marco; Eisen, David; Lerner, Raissa; Lutz, Beat; Poetz, Oliver; Pluschke, Gerd; Gertsch, Jürg

    2012-01-01

    The α-hemoglobin-derived dodecapeptide RVD-hemopressin (RVDPVNFKLLSH) has been proposed to be an endogenous agonist for the cannabinoid receptor type 1 (CB1). To study this peptide, we have raised mAbs against its C-terminal part. Using an immunoaffinity mass spectrometry approach, a whole family of N-terminally extended peptides in addition to RVD-Hpα were identified in rodent brain extracts and human and mouse plasma. We designated these peptides Pepcan-12 (RVDPVNFKLLSH) to Pepcan-23 (SALSDLHAHKLRVDPVNFKLLSH), referring to peptide length. The most abundant Pepcans found in the brain were tested for CB1 receptor binding. In the classical radioligand displacement assay, Pepcan-12 was the most efficacious ligand but only partially displaced both [3H]CP55,940 and [3H]WIN55,212-2. The data were fitted with the allosteric ternary complex model, revealing a cooperativity factor value α < 1, thus indicating a negative allosteric modulation. Dissociation kinetic studies of [3H]CP55,940 in the absence and presence of Pepcan-12 confirmed these results by showing increased dissociation rate constants induced by Pepcan-12. A fluorescently labeled Pepcan-12 analog was synthesized to investigate the binding to CB1 receptors. Competition binding studies revealed Ki values of several Pepcans in the nanomolar range. Accordingly, using competitive ELISA, we found low nanomolar concentrations of Pepcans in human plasma and ∼100 pmol/g in mouse brain. Surprisingly, Pepcan-12 exhibited potent negative allosteric modulation of the orthosteric agonist-induced cAMP accumulation, [35S]GTPγS binding, and CB1 receptor internalization. Pepcans are the first endogenous allosteric modulators identified for CB1 receptors. Given their abundance in the brain, Pepcans could play an important physiological role in modulating endocannabinoid signaling. PMID:22952224

  20. Metal ion coupled protein folding and allosteric motions

    NASA Astrophysics Data System (ADS)

    Wang, Wei

    2014-03-01

    Many proteins need the help of cofactors for their successful folding and functioning. Metal ions, i.e., Zn2+, Ca2+, and Mg2+ etc., are typical biological cofactors. Binding of metal ions can reshape the energy landscapes of proteins, thereby modifying the folding and allosteric motions. For example, such binding may make the intrinsically disordered proteins have funneled energy landscapes, consequently, ensures their spontaneous folding. In addition, the binding may activate certain biological processes by inducing related conformational changes of regulation proteins. However, how the local interactions involving the metal ion binding can induce the global conformational motions of proteins remains elusive. Investigating such question requires multiple models with different details, including quantum mechanics, atomistic models, and coarse grained models. In our recent work, we have been developing such multiscale methods which can reasonably model the metal ion binding induced charge transfer, protonation/deprotonation, and large conformational motions of proteins. With such multiscale model, we elucidated the zinc-binding induced folding mechanism of classical zinc finger and the calcium-binding induced dynamic symmetry breaking in the allosteric motions of calmodulin. In addition, we studied the coupling of folding, calcium binding and allosteric motions of calmodulin domains. In this talk, I will introduce the above progresses on the metal ion coupled protein folding and allosteric motions. We thank the finacial support from NSFC and the 973 project.

  1. Allosteric regulation in phosphofructokinase from the extreme thermophile Thermus thermophilus.

    PubMed

    McGresham, Maria S; Lovingshimer, Michelle; Reinhart, Gregory D

    2014-01-14

    An investigation into the kinetics and regulatory properties of the type-1 phosphofructokinase (PFK) from the extreme thermophile Thermus thermophilus (TtPFK) reveals an enzyme that is inhibited by PEP and activated by ADP by modifying the affinity exhibited for the substrate fructose 6-phosphate (Fru-6-P) in a manner analogous to other prokaryotic PFKs. However, TtPFK binds both of these allosteric ligands significantly more tightly than other bacterial PFKs while effecting a substantially more modest extent of inhibition or activation at 25 °C, reinforcing the principle that binding affinity and effectiveness can be both independent and uncorrelated to one another. These properties have allowed us to establish rigorously that PEP only inhibits by antagonizing the binding of Fru-6-P and not by influencing turnover, a conclusion that requires kcat to be determined under conditions in which both inhibitor and substrate are saturating simultaneously. In addition, the temperature dependence of the allosteric effects on Fru-6-P binding indicate that the coupling free energies are entropy-dominated, as observed previously for PFK from Bacillus stearothermophilus but not for PFK from Escherichia coli , supporting the hypothesis that entropy-dominated allosteric effects may be a characteristic of enzymes derived from thermostable organisms. For such enzymes, the root cause of the allosteric effect may not be easily discerned from static structural information such as that obtained from X-ray crystallography. PMID:24328040

  2. Allosteric Modulators of Class B G-Protein-Coupled Receptors

    PubMed Central

    Hoare, Sam R.J

    2007-01-01

    Class B GPCR’s are activated by peptide ligands, typically 30-40 amino acid residues, that are involved in major physiological functions such as glucose homeostasis (glucagon and glucagon-like peptide 1), calcium homeostasis and bone turnover (parathyroid hormone and calcitonin), and control of the stress axis (corticotropin-releasing factor). Peptide therapeutics have been developed targeting these receptors but development of nonpeptide ligands, enabling oral administration, has proved challenging. Allosteric modulation of these receptors provides a potential route to developing nonpeptide ligands that inhibit, activate, or potentiate activation of these receptors. Here the known mechanisms of allosteric modulators targeting Class B GPCR’s are reviewed, particularly nonpeptide antagonists of the corticotropin-releasing factor 1 receptor and allosteric enhancers of the glucagon-like peptide-1 receptor. Also discussed is the potential for antagonist ligands to operate by competitive inhibition of one of the peptide binding sites, analogous to the Charniere mechanism. These mechanisms are then used to discuss potential strategies and management of pharmacological complexity in the future development of allosteric modulators for Class B GPCR’s. PMID:19305799

  3. Allosteric activation of M4 muscarinic receptors improve behavioral and physiological alterations in early symptomatic YAC128 mice

    PubMed Central

    Pancani, Tristano; Foster, Daniel J.; Moehle, Mark S.; Bichell, Terry Jo; Bradley, Emma; Bridges, Thomas M.; Klar, Rebecca; Poslusney, Mike; Rook, Jerri M.; Daniels, J. Scott; Niswender, Colleen M.; Jones, Carrie K.; Wood, Michael R.; Bowman, Aaron B.; Lindsley, Craig W.; Xiang, Zixiu; Conn, P. Jeffrey

    2015-01-01

    Mutations that lead to Huntington’s disease (HD) result in increased transmission at glutamatergic corticostriatal synapses at early presymptomatic stages that have been postulated to set the stage for pathological changes and symptoms that are observed at later ages. Based on this, pharmacological interventions that reverse excessive corticostriatal transmission may provide a novel approach for reducing early physiological changes and motor symptoms observed in HD. We report that activation of the M4 subtype of muscarinic acetylcholine receptor reduces transmission at corticostriatal synapses and that this effect is dramatically enhanced in presymptomatic YAC128 HD and BACHD relative to wild-type mice. Furthermore, chronic administration of a novel highly selective M4 positive allosteric modulator (PAM) beginning at presymptomatic ages improves motor and synaptic deficits in 5-mo-old YAC128 mice. These data raise the exciting possibility that selective M4 PAMs could provide a therapeutic strategy for the treatment of HD. PMID:26508634

  4. Allosteric activation of M4 muscarinic receptors improve behavioral and physiological alterations in early symptomatic YAC128 mice.

    PubMed

    Pancani, Tristano; Foster, Daniel J; Moehle, Mark S; Bichell, Terry Jo; Bradley, Emma; Bridges, Thomas M; Klar, Rebecca; Poslusney, Mike; Rook, Jerri M; Daniels, J Scott; Niswender, Colleen M; Jones, Carrie K; Wood, Michael R; Bowman, Aaron B; Lindsley, Craig W; Xiang, Zixiu; Conn, P Jeffrey

    2015-11-10

    Mutations that lead to Huntington's disease (HD) result in increased transmission at glutamatergic corticostriatal synapses at early presymptomatic stages that have been postulated to set the stage for pathological changes and symptoms that are observed at later ages. Based on this, pharmacological interventions that reverse excessive corticostriatal transmission may provide a novel approach for reducing early physiological changes and motor symptoms observed in HD. We report that activation of the M4 subtype of muscarinic acetylcholine receptor reduces transmission at corticostriatal synapses and that this effect is dramatically enhanced in presymptomatic YAC128 HD and BACHD relative to wild-type mice. Furthermore, chronic administration of a novel highly selective M4 positive allosteric modulator (PAM) beginning at presymptomatic ages improves motor and synaptic deficits in 5-mo-old YAC128 mice. These data raise the exciting possibility that selective M4 PAMs could provide a therapeutic strategy for the treatment of HD. PMID:26508634

  5. Porphyrin-encapsulated metal-organic frameworks as mimetic catalysts for electrochemical DNA sensing via allosteric switch of hairpin DNA.

    PubMed

    Ling, Pinghua; Lei, Jianping; Zhang, Lei; Ju, Huangxian

    2015-04-01

    A sensitive electrochemical sensor is designed for DNA detection based on mimetic catalysis of metal-organic framework (MOF) and allosteric switch of hairpin DNA. The functional MOFs are synthesized as signal probes by a one-pot encapsulation of iron(III) meso-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin chloride (FeTCPP) into a prototypal MOF, HKUST-1(Cu), and sequentially conjugated with streptavidin (SA) as a recognition element. The resulting FeTCPP@MOF composites can mimetically catalyze the oxidation of o-phenylenediamine (o-PD) to 2,2'-diaminoazobenzene, which is a good electrochemical indicator for signal readout. The presence of target DNA introduces the allosteric switch of hairpin DNA to form SA aptamer, and thus, FeTCPP@MOF-SA probe is brought on the electrode surface via the specific recognition between SA and the corresponding aptamer, resulting in the enhancement of electrochemical signal. The "signal-on" electrochemical sensor can detect target DNA down to 0.48 fM with the linear range of 10 fM to 10 nM. Moreover, the MOF-based electrochemical sensor exhibits acceptable selectivity against even a single mismatched DNA and good feasibility in complex serum matrixes. This strategy opens up a new direction of porphyrin-functionalized MOF for signal transduction in electrochemical biosensing. PMID:25741988

  6. Transmission of 107-Gb/s mode and polarization multiplexed CO-OFDM signal over a two-mode fiber.

    PubMed

    Li, An; Al Amin, Abdullah; Chen, Xi; Shieh, William

    2011-04-25

    In addition to the dimensions of time, frequency, complex constellation, and polarization, spatial mode can be the fifth dimension to be explored for modulation and multiplexing in optical fiber communications. In this paper, we demonstrate successful transmission of 107-Gb/s dual-mode and dual-polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) over a 4.5-km two-mode fiber. A mechanically-induced LP01/LP11 mode converter is used as the mode selective element in a spatial-mode multiplexed system. PMID:21643133

  7. 28 Gb/s duobinary signal transmission over 40 km based on 10 GHz DML and PIN for 100 Gb/s PON.

    PubMed

    Li, Zhengxuan; Yi, Lilin; Wang, Xiaodong; Hu, Weisheng

    2015-08-10

    In this paper, we demonstrate the direct modulation and direct detection of 28-Gb/s duobinary signal for the future downstream capacity upgrade in next generation passive optical network (PON). Commercial 10-GHz directly modulated laser (DML) and PIN with a combined modulation bandwidth of ~7 GHz are used as transmitter and receiver respectively. In order to mitigate the chromatic dispersion induced signal distortion, an optical delay interferometer (DI) is employed to narrow down the signal spectrum, thereby realizing 40-km single mode fiber (SMF) transmission in C-band. Besides, the chirp-induced spectral broadening of the directly modulated signal enables a higher launch power than external modulation schemes, which increases the loss budget of the system. As a result, 31-dB loss budget is achieved, supporting 64 users with 40-km reach. Also, as the transceivers in both optical line terminal (OLT) and optical network unit (ONU) are commercial l0-GHz devices, the proposed scheme is compatible with 40-Gb/s time and wavelength division multiplexing passive optical network (TWDM-PON) systems, providing a cost-efficient alternative for the development of 100G PON. PMID:26367880

  8. A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulses

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Ramakrishnan, R.; Ahuja, K. K.; Brown, W. H.

    1981-01-01

    An acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.

  9. Maturation of glutamatergic transmission in the vestibulo-olivary pathway impacts on the registration of head rotational signals in the brainstem of rats.

    PubMed

    Lai, Chun-Hong; Ma, Chun-Wai; Lai, Suk-King; Han, Lei; Wong, Hoi-Man; Yeung, Kelvin Wai-Kwok; Shum, Daisy Kwok-Yan; Chan, Ying-Shing

    2016-01-01

    The recognition of head orientation in the adult involves multi-level integration of inputs within the central vestibular circuitry. How the different inputs are recruited during postnatal development remains unclear. We hypothesize that glutamatergic transmission at the vestibular nucleus contributes to developmental registration of head orientations along the vestibulo-olivary pathway. To investigate the maturation profile by which head rotational signals are registered in the brainstem, we used sinusoidal rotations on the orthogonal planes of the three pairs of semicircular canals. Fos expression was used as readout of neurons responsive to the rotational stimulus. Neurons in the vestibular nucleus and prepositus hypoglossal nucleus responded to all rotations as early as P4 and reached adult numbers by P21. In the reticular formation and inferior olive, neurons also responded to horizontal rotations as early as P4 but to vertical rotations not until P21 and P25, respectively. Neuronal subpopulations that distinguish between rotations activating the orthogonally oriented vertical canals were identifiable in the medial and spinal vestibular nuclei by P14 and in the inferior olivary subnuclei IOβ and IOK by P25. Neonatal perturbation of glutamate transmission in the vestibular nucleus was sufficient to derange formation of this distribution in the inferior olive. This is the first demonstration that developmental refinement of glutamatergic synapses in the central vestibular circuitry is essential for developmental registration of head rotational signals in the brainstem. PMID:25304399

  10. Mechanotransduction in the Endothelium: Role of Membrane Proteins and Reactive Oxygen Species in Sensing, Transduction, and Transmission of the Signal with Altered Blood Flow

    PubMed Central

    Fisher, Aron B.

    2014-01-01

    Abstract Significance: Changes in shear stress associated with alterations in blood flow initiate a signaling cascade that modulates the vascular phenotype. Shear stress is “sensed” by the endothelium via a mechanosensitive complex on the endothelial cell (EC) membrane that has been characterized as a “mechanosome” consisting of caveolae, platelet endothelial cell adhesion molecule (PECAM), vascular endothelial growth factor receptor 2 (VEGFR2), vascular endothelial (VE)–cadherin, and possibly other elements. This shear signal is transduced by cell membrane ion channels and various kinases and results in the activation of NADPH oxidase (type 2) with the production of reactive oxygen species (ROS). Recent Advances: The signaling cascade associated with stop of shear, as would occur in vivo with various obstructive pathologies, leads to cell proliferation and eventual revascularization. Critical Issues and Future Directions: Although several elements of mechanosensing such as the sensing event, the transduction, transmission, and reception of the mechanosignal are now reasonably well understood, the links among these discrete steps in the pathway are not clear. Thus, identifying the mechanisms for the interaction of the KATP channel, the kinases, and ROS to drive long-term adaptive responses in ECs is necessary. A critical re-examination of the signaling events associated with complex flow patterns (turbulent, oscillatory) under physiological conditions is also essential for the progress in the field. Since these complex shear patterns may be associated with an atherosclerosis susceptible phenotype, a specific challenge will be the pharmacological modulation of the responses to altered signaling events that occur at specific sites of disturbed or obstructed flow. Antioxid. Redox Signal. 20, 899–913. PMID:24328670

  11. Conserved residues of the Pro103–Arg115 loop are involved in triggering the allosteric response of the Escherichia coli ADP-glucose pyrophosphorylase

    PubMed Central

    Hill, Benjamin L; Wong, Jennifer; May, Brian M; Huerta, Fidel B; Manley, Tara E; Sullivan, Peter RF; Olsen, Kenneth W; Ballicora, Miguel A

    2015-01-01

    The synthesis of glycogen in bacteria and starch in plants is allosterically controlled by the production of ADP-glucose by ADP-glucose pyrophosphorylase. Using computational studies, site-directed mutagenesis, and kinetic characterization, we found a critical region for transmitting the allosteric signal in the Escherichia coli ADP-glucose pyrophosphorylase. Molecular dynamics simulations and structural comparisons with other ADP-glucose pyrophosphorylases provided information to hypothesize that a Pro103–Arg115 loop is part of an activation path. It had strongly correlated movements with regions of the enzyme associated with regulation and ATP binding, and a network analysis showed that the optimal network pathways linking ATP and the activator binding Lys39 mainly involved residues of this loop. This hypothesis was biochemically tested by mutagenesis. We found that several alanine mutants of the Pro103–Arg115 loop had altered activation profiles for fructose-1,6-bisphosphate. Mutants P103A, Q106A, R107A, W113A, Y114A, and R115A had the most altered kinetic profiles, primarily characterized by a lack of response to fructose-1,6-bisphosphate. This loop is a distinct insertional element present only in allosterically regulated sugar nucleotide pyrophosphorylases that could have been acquired to build a triggering mechanism to link proto-allosteric and catalytic sites. PMID:25620658

  12. Ionospheric ELF radio signal generation due to LF and/or MF radio transmissions. I - Experimental results

    NASA Astrophysics Data System (ADS)

    Cannon, P. S.

    1982-10-01

    Data obtained in a program of ELF/VLF goniometer recordings in northern Scandinavia are analyzed. The results indicate that six 1-kHz timing signals (pips) received on the hour were produced by a nonlinear demodulation mechanism in the D region of the auroral ionosphere. A positive temporal correlation between ELF pip generation and periods of enhanced local magnetic activity is obtained, demonstrating a close association between the reception of the ELF pips and the auroral electrojet. The pip magnetic field strengths are found to be of the order of 0.1 pT. The originating signals are shown to emanate from one or more Soviet LF and/or MF radio transmitters located at least several hundred km from the favored generation region.

  13. Autism-associated mutations in ProSAP2/Shank3 impair synaptic transmission and neurexin-neuroligin-mediated transsynaptic signaling.

    PubMed

    Arons, Magali H; Thynne, Charlotte J; Grabrucker, Andreas M; Li, Dong; Schoen, Michael; Cheyne, Juliette E; Boeckers, Tobias M; Montgomery, Johanna M; Garner, Craig C

    2012-10-24

    Mutations in several postsynaptic proteins have recently been implicated in the molecular pathogenesis of autism and autism spectrum disorders (ASDs), including Neuroligins, Neurexins, and members of the ProSAP/Shank family, thereby suggesting that these genetic forms of autism may share common synaptic mechanisms. Initial studies of ASD-associated mutations in ProSAP2/Shank3 support a role for this protein in glutamate receptor function and spine morphology, but these synaptic phenotypes are not universally penetrant, indicating that other core facets of ProSAP2/Shank3 function must underlie synaptic deficits in patients with ASDs. In the present study, we have examined whether the ability of ProSAP2/Shank3 to interact with the cytoplasmic tail of Neuroligins functions to coordinate pre/postsynaptic signaling through the Neurexin-Neuroligin signaling complex in hippocampal neurons of Rattus norvegicus. Indeed, we find that synaptic levels of ProSAP2/Shank3 regulate AMPA and NMDA receptor-mediated synaptic transmission and induce widespread changes in the levels of presynaptic and postsynaptic proteins via Neurexin-Neuroligin transsynaptic signaling. ASD-associated mutations in ProSAP2/Shank3 disrupt not only postsynaptic AMPA and NMDA receptor signaling but also interfere with the ability of ProSAP2/Shank3 to signal across the synapse to alter presynaptic structure and function. These data indicate that ASD-associated mutations in a subset of synaptic proteins may target core cellular pathways that coordinate the functional matching and maturation of excitatory synapses in the CNS. PMID:23100419

  14. Allosteric inhibitors of plasma membrane Ca pumps: Invention and applications of caloxins.

    PubMed

    Pande, Jyoti; Szewczyk, Magdalena M; Grover, Ashok K

    2011-03-26

    Plasma membrane Ca(2+) pumps (PMCA) play a major role in Ca(2+) homeostasis and signaling by extruding cellular Ca(2+) with high affinity. PMCA isoforms are encoded by four genes which are expressed differentially in various cell types in normal and disease states. Therefore, PMCA isoform selective inhibitors would aid in delineating their role in physiology and pathophysiology. We are testing the hypothesis that extracellular domains of PMCA can be used as allosteric targets to obtain a novel class of PMCA-specific inhibitors termed caloxins. This review presents the concepts behind the invention of caloxins and our progress in this area. A section is also devoted to the applications of caloxins in literature. We anticipate that isoform-selective caloxins will aid in understanding PMCA physiology in health and disease. With strategies to develop therapeutics from bioactive peptides, caloxins may become clinically useful in cardiovascular diseases, neurological disorders, retinopathy, cancer and contraception. PMID:21537489

  15. Investigation of in-band transmission of both spectral amplitude coding/optical code division multiple-access and wavelength division multiplexing signals

    NASA Astrophysics Data System (ADS)

    Ashour, Isaac A. M.; Shaari, Sahbudin; Shalaby, Hossam M. H.; Menon, P. Susthitha

    2011-06-01

    The transmission of both optical code division multiple-access (OCDMA) and wavelength division multiplexing (WDM) users on the same band is investigated. Code pulses of spectral amplitude coding (SAC)/optical code division multiple-access (CDMA) are overlaid onto a multichannel WDM system. Notch filters are utilized in order to suppress the WDM interference signals for detection of optical broadband CDMA signals. Modified quadratic congruence (MQC) codes are used as the signature codes for the SAC/OCDMA system. The proposed system is simulated and its performance in terms of both the bit-error rate and Q-factor are determined. In addition, eavesdropper probability of error-free code detection is evaluated. Our results are compared to traditional nonhybrid systems. It is concluded that the proposed hybrid scheme still achieves acceptable performance. In addition, it provides enhanced data confidentiality as compared to the scheme with SAC/OCDMA only. It is also shown that the performance of the proposed system is limited by the interference of the WDM signals. Furthermore, the simulation illustrates the tradeoff between the performance and confidentiality for authorized users.

  16. Application of advanced signal processing techniques to the rectification and registration of spaceborne imagery. [technology transfer, data transmission

    NASA Technical Reports Server (NTRS)

    Caron, R. H.; Rifman, S. S.; Simon, K. W.

    1974-01-01

    The development of an ERTS/MSS image processing system responsive to the needs of the user community is discussed. An overview of the TRW ERTS/MSS processor is presented, followed by a more detailed discussion of image processing functions satisfied by the system. The particular functions chosen for discussion are evolved from advanced signal processing techniques rooted in the areas of communication and control. These examples show how classical aerospace technology can be transferred to solve the more contemporary problems confronting the users of spaceborne imagery.

  17. Genetically encoded photo-cross-linkers map the binding site of an allosteric drug on a G protein-coupled receptor.

    PubMed

    Grunbeck, Amy; Huber, Thomas; Abrol, Ravinder; Trzaskowski, Bartosz; Goddard, William A; Sakmar, Thomas P

    2012-06-15

    G protein-coupled receptors (GPCRs) are dynamic membrane proteins that bind extracellular molecules to transduce signals. Although GPCRs represent the largest class of therapeutic targets, only a small percentage of their ligand-binding sites are precisely defined. Here we describe the novel application of targeted photo-cross-linking using unnatural amino acids to obtain structural information about the allosteric binding site of a small molecule drug, the CCR5-targeted HIV-1 co-receptor blocker maraviroc. PMID:22455376

  18. Molecular blueprint of allosteric binding sites in a homologue of the agonist-binding domain of the α7 nicotinic acetylcholine receptor

    PubMed Central

    Spurny, Radovan; Debaveye, Sarah; Farinha, Ana; Veys, Ken; Vos, Ann M.; Gossas, Thomas; Atack, John; Bertrand, Sonia; Bertrand, Daniel; Danielson, U. Helena; Tresadern, Gary; Ulens, Chris

    2015-01-01

    The α7 nicotinic acetylcholine receptor (nAChR) belongs to the family of pentameric ligand-gated ion channels and is involved in fast synaptic signaling. In this study, we take advantage of a recently identified chimera of the extracellular domain of the native α7 nicotinic acetylcholine receptor and acetylcholine binding protein, termed α7-AChBP. This chimeric receptor was used to conduct an innovative fragment-library screening in combination with X-ray crystallography to identify allosteric binding sites. One allosteric site is surface-exposed and is located near the N-terminal α-helix of the extracellular domain. Ligand binding at this site causes a conformational change of the α-helix as the fragment wedges between the α-helix and a loop homologous to the main immunogenic region of the muscle α1 subunit. A second site is located in the vestibule of the receptor, in a preexisting intrasubunit pocket opposite the agonist binding site and corresponds to a previously identified site involved in positive allosteric modulation of the bacterial homolog ELIC. A third site is located at a pocket right below the agonist binding site. Using electrophysiological recordings on the human α7 nAChR we demonstrate that the identified fragments, which bind at these sites, can modulate receptor activation. This work presents a structural framework for different allosteric binding sites in the α7 nAChR and paves the way for future development of novel allosteric modulators with therapeutic potential. PMID:25918415

  19. Allosteric Pathways in the PPARγ-RXRα nuclear receptor complex

    NASA Astrophysics Data System (ADS)

    Ricci, Clarisse G.; Silveira, Rodrigo L.; Rivalta, Ivan; Batista, Victor S.; Skaf, Munir S.

    2016-01-01

    Understanding the nature of allostery in DNA-nuclear receptor (NR) complexes is of fundamental importance for drug development since NRs regulate the transcription of a myriad of genes in humans and other metazoans. Here, we investigate allostery in the peroxisome proliferator-activated/retinoid X receptor heterodimer. This important NR complex is a target for antidiabetic drugs since it binds to DNA and functions as a transcription factor essential for insulin sensitization and lipid metabolism. We find evidence of interdependent motions of Ω-loops and PPARγ-DNA binding domain with contacts susceptible to conformational changes and mutations, critical for regulating transcriptional functions in response to sequence-dependent DNA dynamics. Statistical network analysis of the correlated motions, observed in molecular dynamics simulations, shows preferential allosteric pathways with convergence centers comprised of polar amino acid residues. These findings are particularly relevant for the design of allosteric modulators of ligand-dependent transcription factors.

  20. Ultrasensitive regulation of anapleurosis via allosteric activation of PEP carboxylase

    PubMed Central

    Xu, Yi-Fan; Amador-Noguez, Daniel; Reaves, Marshall Louis; Feng, Xiao-Jiang; Rabinowitz, Joshua D.

    2012-01-01

    Anapleurosis is the filling of the TCA cycle with four-carbon units. The common substrate for both anapleurosis and glucose phosphorylation in bacteria is the terminal glycolytic metabolite, phosphoenolpyruvate (PEP). Here we show that E. coli quickly and almost completely turns off PEP consumption upon glucose removal. The resulting build-up of PEP is used to quickly import glucose if it becomes re-available. The switch-like termination of anapleurosis results from depletion of fructose-1,6-bisphosphate (FBP), an ultrasensitive allosteric activator of PEP carboxylase. E. coli expressing an FBP-insensitive point mutant of PEP carboxylase grow normally on steady glucose. However, they fail to build-up PEP upon glucose removal, grow poorly on oscillating glucose, and suffer from futile cycling at the PEP node on gluconeogenic substrates. Thus, bacterial central carbon metabolism is intrinsically programmed with ultrasensitive allosteric regulation to enable rapid adaptation to changing environmental conditions. PMID:22522319

  1. Allosterism and Structure in Thermally Activated Transient Receptor Potential Channels.

    PubMed

    Diaz-Franulic, Ignacio; Poblete, Horacio; Miño-Galaz, Germán; González, Carlos; Latorre, Ramón

    2016-07-01

    The molecular sensors that mediate temperature changes in living organisms are a large family of proteins known as thermosensitive transient receptor potential (TRP) ion channels. These membrane proteins are polymodal receptors that can be activated by cold or hot temperatures, depending on the channel subtype, voltage, and ligands. The stimuli sensors are allosterically coupled to a pore domain, increasing the probability of finding the channel in its ion conductive conformation. In this review we first discuss the allosteric coupling between the temperature and voltage sensor modules and the pore domain, and then discuss the thermodynamic foundations of thermo-TRP channel activation. We provide a structural overview of the molecular determinants of temperature sensing. We also posit an anisotropic thermal diffusion model that may explain the large temperature sensitivity of TRP channels. Additionally, we examine the effect of several ligands on TRP channel function and the evidence regarding their mechanisms of action. PMID:27297398

  2. Looking for the Origin of Allosteric Cooperativity in Metallopolymers.

    PubMed

    Babel, Lucille; Hoang, Thi Nhu Y; Guénée, Laure; Besnard, Céline; Wesolowski, Tomasz A; Humbert-Droz, Marie; Piguet, Claude

    2016-06-01

    The basic concept of allosteric cooperativity used in biology, chemistry and physics states that any change in the intermolecular host-guest interactions operating in multisite receptors can be assigned to intersite interactions. Using lanthanide metals as guests and linear multi-tridentate linear oligomers of variable lengths and geometries as hosts, this work shows that the quantitative modeling of metal loadings requires the consideration of a novel phenomenon originating from solvation processes. It stepwise modulates the intrinsic affinity of each isolated site in multisite receptors, and this without resorting to allosteric cooperativity. An easy-to-handle additive model predicts a negative power law dependence of the intrinsic affinity on the length of the linear metallopolymer. Applied to lanthanidopolymers, the latter common analysis overestimates cooperativity factors by more than two orders of magnitude. PMID:27142083

  3. Allosteric Pathways in the PPARγ-RXRα nuclear receptor complex

    PubMed Central

    Ricci, Clarisse G.; Silveira, Rodrigo L.; Rivalta, Ivan; Batista, Victor S.; Skaf, Munir S.

    2016-01-01

    Understanding the nature of allostery in DNA-nuclear receptor (NR) complexes is of fundamental importance for drug development since NRs regulate the transcription of a myriad of genes in humans and other metazoans. Here, we investigate allostery in the peroxisome proliferator-activated/retinoid X receptor heterodimer. This important NR complex is a target for antidiabetic drugs since it binds to DNA and functions as a transcription factor essential for insulin sensitization and lipid metabolism. We find evidence of interdependent motions of Ω-loops and PPARγ-DNA binding domain with contacts susceptible to conformational changes and mutations, critical for regulating transcriptional functions in response to sequence-dependent DNA dynamics. Statistical network analysis of the correlated motions, observed in molecular dynamics simulations, shows preferential allosteric pathways with convergence centers comprised of polar amino acid residues. These findings are particularly relevant for the design of allosteric modulators of ligand-dependent transcription factors. PMID:26823026

  4. mGluR5 Positive Allosteric Modulation Enhances Extinction Learning Following Cocaine Self-Administration

    PubMed Central

    Cleva, Richard M.; Hicks, Megan P.; Gass, Justin T.; Wischerath, Kelly C.; Plasters, Elizabeth T.; Widholm, John J.; Olive, M. Foster

    2011-01-01

    Extinction of classically and instrumentally conditioned behaviors, such as conditioned fear and drug-seeking behavior, is a process of active learning, and recent studies indicate that potentiation of glutamatergic transmission facilitates extinction learning. In this study we investigated the effects of the type 5 metabotropic glutamate receptors (mGluR5) positive allosteric modulator 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) on the extinction of cocaine-seeking behavior in rats with a history of intravenous cocaine self-administration. To assess its effects on acquisition and consolidation of extinction learning, CDPPB (60 mg/kg) or vehicle was administered either 20 min prior to, or immediately following, each of 10 extinction sessions, respectively. When administered prior to each extinction session, CDPPB produced a significant reduction in the number of active lever presses on all 10 days of extinction training as compared to vehicle-treated animals. When administered following each extinction session, a significant reduction in the number of active lever presses was observed on the 2nd through 10th day of extinction. Both treatment regimens also reduced the number of extinction training sessions required to meet extinction criteria. Pre- or post-extinction training administration of CDPPB did not alter responding on the inactive lever and had no effects on open field locomotor activity. These data indicate that positive allosteric modulation of mGluR5 receptors facilitates the acquisition and consolidation of extinction learning following cocaine self-administration, and may provide a novel pharmacological approach to enhancing extinction learning when combined with cue exposure therapy for the treatment of cocaine addiction. PMID:21319882

  5. Divergent allosteric patterns verify the regulatory paradigm for aspartate transcarbamylase.

    PubMed

    Wales, M E; Madison, L L; Glaser, S S; Wild, J R

    1999-12-17

    The native Escherichia coli aspartate transcarbamoylase (ATCase, E.C. 2.1.3.2) provides a classic allosteric model for the feedback inhibition of a biosynthetic pathway by its end products. Both E. coli and Erwinia herbicola possess ATCase holoenzymes which are dodecameric (2(c3):3(r2)) with 311 amino acid residues per catalytic monomer and 153 and 154 amino acid residues per regulatory (r) monomer, respectively. While the quaternary structures of the two enzymes are identical, the primary amino acid sequences have diverged by 14 % in the catalytic polypeptide and 20 % in the regulatory polypeptide. The amino acids proposed to be directly involved in the active site and nucleotide binding site are strictly conserved between the two enzymes; nonetheless, the two enzymes differ in their catalytic and regulatory characteristics. The E. coli enzyme has sigmoidal substrate binding with activation by ATP, and inhibition by CTP, while the E. herbicola enzyme has apparent first order kinetics at low substrate concentrations in the absence of allosteric ligands, no ATP activation and only slight CTP inhibition. In an apparently important and highly conserved characteristic, CTP and UTP impose strong synergistic inhibition on both enzymes. The co-operative binding of aspartate in the E. coli enzyme is correlated with a T-to-R conformational transition which appears to be greatly reduced in the E. herbicola enzyme, although the addition of inhibitory heterotropic ligands (CTP or CTP+UTP) re-establishes co-operative saturation kinetics. Hybrid holoenzymes assembled in vivo with catalytic subunits from E. herbicola and regulatory subunits from E. coli mimick the allosteric response of the native E. coli holoenzyme and exhibit ATP activation. The reverse hybrid, regulatory subunits from E. herbicola and catalytic subunits from E. coli, exhibited no response to ATP. The conserved structure and diverged functional characteristics of the E. herbicola enzyme provides an opportunity

  6. Micro- and nano-structural details of a spider's filter for substrate vibrations: relevance for low-frequency signal transmission

    PubMed Central

    Erko, Maxim; Younes-Metzler, Osnat; Rack, Alexander; Zaslansky, Paul; Young, Seth L.; Milliron, Garrett; Chyasnavichyus, Marius; Barth, Friedrich G.; Fratzl, Peter; Tsukruk, Vladimir; Zlotnikov, Igor; Politi, Yael

    2015-01-01

    The metatarsal lyriform organ of the Central American wandering spider Cupiennius salei is its most sensitive vibration detector. It is able to sense a wide range of vibration stimuli over four orders of magnitude in frequency between at least as low as 0.1 Hz and several kilohertz. Transmission of the vibrations to the slit organ is controlled by a cuticular pad in front of it. While the mechanism of high-frequency stimulus transfer (above ca 40 Hz) is well understood and related to the viscoelastic properties of the pad's epicuticle, it is not yet clear how low-frequency stimuli (less than 40 Hz) are transmitted. Here, we study how the pad material affects the pad's mechanical properties and thus its role in the transfer of the stimulus, using a variety of experimental techniques, such as X-ray micro-computed tomography for three-dimensional imaging, X-ray scattering for structural analysis, and atomic force microscopy and scanning electron microscopy for surface imaging. The mechanical properties were investigated using scanning acoustic microscopy and nanoindentation. We show that large tarsal deflections cause large deformation in the distal highly hydrated part of the pad. Beyond this region, a sclerotized region serves as a supporting frame which resists the deformation and is displaced to push against the slits, with displacement values considerably scaled down to only a few micrometres. Unravelling the structural arrangement in such specialized structures may provide conceptual ideas for the design of new materials capable of controlling a technical sensor's specificity and selectivity, which is so typical of biological sensors. PMID:25631567

  7. NbIT--a new information theory-based analysis of allosteric mechanisms reveals residues that underlie function in the leucine transporter LeuT.

    PubMed

    LeVine, Michael V; Weinstein, Harel

    2014-05-01

    Complex networks of interacting residues and microdomains in the structures of biomolecular systems underlie the reliable propagation of information from an input signal, such as the concentration of a ligand, to sites that generate the appropriate output signal, such as enzymatic activity. This information transduction often carries the signal across relatively large distances at the molecular scale in a form of allostery that is essential for the physiological functions performed by biomolecules. While allosteric behaviors have been documented from experiments and computation, the mechanism of this form of allostery proved difficult to identify at the molecular level. Here, we introduce a novel analysis framework, called N-body Information Theory (NbIT) analysis, which is based on information theory and uses measures of configurational entropy in a biomolecular system to identify microdomains and individual residues that act as (i)-channels for long-distance information sharing between functional sites, and (ii)-coordinators that organize dynamics within functional sites. Application of the new method to molecular dynamics (MD) trajectories of the occluded state of the bacterial leucine transporter LeuT identifies a channel of allosteric coupling between the functionally important intracellular gate and the substrate binding sites known to modulate it. NbIT analysis is shown also to differentiate residues involved primarily in stabilizing the functional sites, from those that contribute to allosteric couplings between sites. NbIT analysis of MD data thus reveals rigorous mechanistic elements of allostery underlying the dynamics of biomolecular systems. PMID:24785005

  8. Identification of the Allosteric Regulatory Site of Insulysin

    SciTech Connect

    Noinaj, Nicholas; Bhasin, Sonia K.; Song, Eun Suk; Scoggin, Kirsten E.; Juliano, Maria A.; Juliano, Luiz; Hersh, Louis B.; Rodgers, David W.

    2012-05-25

    Insulin degrading enzyme (IDE) is responsible for the metabolism of insulin and plays a role in clearance of the A{beta} peptide associated with Alzheimer's disease. Unlike most proteolytic enzymes, IDE, which consists of four structurally related domains and exists primarily as a dimer, exhibits allosteric kinetics, being activated by both small substrate peptides and polyphosphates such as ATP. The crystal structure of a catalytically compromised mutant of IDE has electron density for peptide ligands bound at the active site in domain 1 and a distal site in domain 2. Mutating residues in the distal site eliminates allosteric kinetics and activation by a small peptide, as well as greatly reducing activation by ATP, demonstrating that this site plays a key role in allostery. Comparison of the peptide bound IDE structure (using a low activity E111F IDE mutant) with unliganded wild type IDE shows a change in the interface between two halves of the clamshell-like molecule, which may enhance enzyme activity by altering the equilibrium between closed and open conformations. In addition, changes in the dimer interface suggest a basis for communication between subunits. Our findings indicate that a region remote from the active site mediates allosteric activation of insulysin by peptides. Activation may involve a small conformational change that weakens the interface between two halves of the enzyme.

  9. Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins

    PubMed Central

    Peralta, Francisco Andrés; Huidobro-Toro, Juan Pablo

    2016-01-01

    Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel’s ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators. PMID:27384555

  10. Identification of the Allosteric Regulatory Site of Insulysin

    SciTech Connect

    Noinaj, Nicholas; Bhasin, Sonia K.; Song, Eun Suk; Scoggin, Kirsten E.; Juliano, Maria A.; Juliano, Luiz; Hersh, Louis B.; Rodgers, David W.; Gerrard, Juliet Ann

    2011-06-24

    Background Insulin degrading enzyme (IDE) is responsible for the metabolism of insulin and plays a role in clearance of the Aβ peptide associated with Alzheimer's disease. Unlike most proteolytic enzymes, IDE, which consists of four structurally related domains and exists primarily as a dimer, exhibits allosteric kinetics, being activated by both small substrate peptides and polyphosphates such as ATP. Principal Findings The crystal structure of a catalytically compromised mutant of IDE has electron density for peptide ligands bound at the active site in domain 1 and a distal site in domain 2. Mutating residues in the distal site eliminates allosteric kinetics and activation by a small peptide, as well as greatly reducing activation by ATP, demonstrating that this site plays a key role in allostery. Comparison of the peptide bound IDE structure (using a low activity E111F IDE mutant) with unliganded wild type IDE shows a change in the interface between two halves of the clamshell-like molecule, which may enhance enzyme activity by altering the equilibrium between closed and open conformations. In addition, changes in the dimer interface suggest a basis for communication between subunits. Conclusions/Significance Our findings indicate that a region remote from the active site mediates allosteric activation of insulysin by peptides. Activation may involve a small conformational change that weakens the interface between two halves of the enzyme.

  11. Enzyme Inhibition by Allosteric Capture of an Inactive Conformation

    PubMed Central

    Lee, Gregory M.; Shahian, Tina; Baharuddin, Aida; Gable, Jonathan E.; Craik, Charles S.

    2011-01-01

    All members of the human herpesvirus protease family are active as weakly associating dimers, but inactive as monomers. A small molecule allosteric inhibitor of Kaposi’s sarcoma-associated herpesvirus protease (KSHV Pr) traps the enzyme in an inactive monomeric state where the C-terminal helices are unfolded and the hydrophobic dimer interface is exposed. NMR titration studies demonstrate that the inhibitor binds to KSHV Pr monomers with low μM affinity. A 2.0 Å resolution X-ray crystal structure of a C-terminal truncated KSHV Pr-inhibitor complex locates the binding pocket at the dimer interface and displays significant conformational perturbations at the active site, 15 Å from the allosteric site. NMR and CD data suggest that the small molecule inhibits human cytomegalovirus protease (HCMV Pr) via a similar mechanism. As all HHV proteases are functionally and structurally homologous, the inhibitor represents a class of compounds that may be developed into broad-spectrum therapeutics which allosterically regulate enzymatic activity by disrupting protein-protein interactions. PMID:21723875

  12. Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins.

    PubMed

    Peralta, Francisco Andrés; Huidobro-Toro, Juan Pablo

    2016-01-01

    Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel's ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators. PMID:27384555

  13. Prediction of allosteric sites on protein surfaces with an elastic-network-model-based thermodynamic method

    NASA Astrophysics Data System (ADS)

    Su, Ji Guo; Qi, Li Sheng; Li, Chun Hua; Zhu, Yan Ying; Du, Hui Jing; Hou, Yan Xue; Hao, Rui; Wang, Ji Hua

    2014-08-01

    Allostery is a rapid and efficient way in many biological processes to regulate protein functions, where binding of an effector at the allosteric site alters the activity and function at a distant active site. Allosteric regulation of protein biological functions provides a promising strategy for novel drug design. However, how to effectively identify the allosteric sites remains one of the major challenges for allosteric drug design. In the present work, a thermodynamic method based on the elastic network model was proposed to predict the allosteric sites on the protein surface. In our method, the thermodynamic coupling between the allosteric and active sites was considered, and then the allosteric sites were identified as those where the binding of an effector molecule induces a large change in the binding free energy of the protein with its ligand. Using the proposed method, two proteins, i.e., the 70 kD heat shock protein (Hsp70) and GluA2 alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor, were studied and the allosteric sites on the protein surface were successfully identified. The predicted results are consistent with the available experimental data, which indicates that our method is a simple yet effective approach for the identification of allosteric sites on proteins.

  14. ASD v3.0: unraveling allosteric regulation with structural mechanisms and biological networks

    PubMed Central

    Shen, Qiancheng; Wang, Guanqiao; Li, Shuai; Liu, Xinyi; Lu, Shaoyong; Chen, Zhongjie; Song, Kun; Yan, Junhao; Geng, Lv; Huang, Zhimin; Huang, Wenkang; Chen, Guoqiang; Zhang, Jian

    2016-01-01

    Allosteric regulation, the most direct and efficient way of regulating protein function, is induced by the binding of a ligand at one site that is topographically distinct from an orthosteric site. Allosteric Database (ASD, available online at http://mdl.shsmu.edu.cn/ASD) has been developed to provide comprehensive information featuring allosteric regulation. With increasing data, fundamental questions pertaining to allostery are currently receiving more attention from the mechanism of allosteric changes in an individual protein to the entire effect of the changes in the interconnected network in the cell. Thus, the following novel features were added to this updated version: (i) structural mechanisms of more than 1600 allosteric actions were elucidated by a comparison of site structures before and after the binding of an modulator; (ii) 261 allosteric networks were identified to unveil how the allosteric action in a single protein would propagate to affect downstream proteins; (iii) two of the largest human allosteromes, protein kinases and GPCRs, were thoroughly constructed; and (iv) web interface and data organization were completely redesigned for efficient access. In addition, allosteric data have largely expanded in this update. These updates are useful for facilitating the investigation of allosteric mechanisms, dynamic networks and drug discoveries. PMID:26365237

  15. Prediction of allosteric sites on protein surfaces with an elastic-network-model-based thermodynamic method.

    PubMed

    Su, Ji Guo; Qi, Li Sheng; Li, Chun Hua; Zhu, Yan Ying; Du, Hui Jing; Hou, Yan Xue; Hao, Rui; Wang, Ji Hua

    2014-08-01

    Allostery is a rapid and efficient way in many biological processes to regulate protein functions, where binding of an effector at the allosteric site alters the activity and function at a distant active site. Allosteric regulation of protein biological functions provides a promising strategy for novel drug design. However, how to effectively identify the allosteric sites remains one of the major challenges for allosteric drug design. In the present work, a thermodynamic method based on the elastic network model was proposed to predict the allosteric sites on the protein surface. In our method, the thermodynamic coupling between the allosteric and active sites was considered, and then the allosteric sites were identified as those where the binding of an effector molecule induces a large change in the binding free energy of the protein with its ligand. Using the proposed method, two proteins, i.e., the 70 kD heat shock protein (Hsp70) and GluA2 alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor, were studied and the allosteric sites on the protein surface were successfully identified. The predicted results are consistent with the available experimental data, which indicates that our method is a simple yet effective approach for the identification of allosteric sites on proteins. PMID:25215770

  16. ASD v3.0: unraveling allosteric regulation with structural mechanisms and biological networks.

    PubMed

    Shen, Qiancheng; Wang, Guanqiao; Li, Shuai; Liu, Xinyi; Lu, Shaoyong; Chen, Zhongjie; Song, Kun; Yan, Junhao; Geng, Lv; Huang, Zhimin; Huang, Wenkang; Chen, Guoqiang; Zhang, Jian

    2016-01-01

    Allosteric regulation, the most direct and efficient way of regulating protein function, is induced by the binding of a ligand at one site that is topographically distinct from an orthosteric site. Allosteric Database (ASD, available online at http://mdl.shsmu.edu.cn/ASD) has been developed to provide comprehensive information featuring allosteric regulation. With increasing data, fundamental questions pertaining to allostery are currently receiving more attention from the mechanism of allosteric changes in an individual protein to the entire effect of the changes in the interconnected network in the cell. Thus, the following novel features were added to this updated version: (i) structural mechanisms of more than 1600 allosteric actions were elucidated by a comparison of site structures before and after the binding of an modulator; (ii) 261 allosteric networks were identified to unveil how the allosteric action in a single protein would propagate to affect downstream proteins; (iii) two of the largest human allosteromes, protein kinases and GPCRs, were thoroughly constructed; and (iv) web interface and data organization were completely redesigned for efficient access. In addition, allosteric data have largely expanded in this update. These updates are useful for facilitating the investigation of allosteric mechanisms, dynamic networks and drug discoveries. PMID:26365237

  17. Positive allosteric modulation of alpha-7 nicotinic receptors promotes cell death by inducing Ca(2+) release from the endoplasmic reticulum.

    PubMed

    Guerra-Álvarez, María; Moreno-Ortega, Ana J; Navarro, Elisa; Fernández-Morales, José Carlos; Egea, Javier; López, Manuela G; Cano-Abad, María F

    2015-05-01

    Positive allosteric modulation of α7 isoform of nicotinic acetylcholine receptors (α7-nAChRs) is emerging as a promising therapeutic approach for central nervous system disorders such as schizophrenia or Alzheimer's disease. However, its effect on Ca(2+) signaling and cell viability remains controversial. This study focuses on how the type II positive allosteric modulator (PAM II) PNU120596 affects intracellular Ca(2+) signaling and cell viability. We used human SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH). We monitored cytoplasmic and endoplasmic reticulum (ER) Ca(2+) with Fura-2 and the genetically encoded cameleon targeting the ER, respectively. Nicotinic inward currents were measured using patch-clamp techniques. Viability was assessed using methylthiazolyl blue tetrazolium bromide or propidium iodide staining. We observed that in the presence of a nicotinic agonist, PNU120596 (i) reduced viability of α7-SH but not of C-SH cells; (ii) significantly increased inward nicotinic currents and cytosolic Ca(2+) concentration; (iii) released Ca(2+) from the ER by a Ca(2+) -induced Ca(2+) release mechanism only in α7-SH cells; (iv) was cytotoxic in rat organotypic hippocampal slice cultures; and, lastly, all these effects were prevented by selective blockade of α7-nAChRs, ryanodine receptors, or IP3 receptors. In conclusion, positive allosteric modulation of α7-nAChRs with the PAM II PNU120596 can lead to dysregulation of ER Ca(2+) , overloading of intracellular Ca(2+) , and neuronal cell death. This study focuses on how the type II positive allosteric modulator PNU120596 (PAM II PNU12) affects intracellular Ca(2+) signaling and cell viability. Using SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH), we find that PAM of α7-nAChRs with PNU120596: (i) increases inward calcium current (ICa ) and cytosolic Ca(2+) concentration ([Ca(2+) ]cyt ); (ii) releases Ca(2+) from the ER ([Ca(2

  18. Investigation of receiver contraints on the transmission performance of 1 Tbps WDM-Nyquist and CO-OFDM signals

    NASA Astrophysics Data System (ADS)

    Hraghi, Abir; Menif, Mourad

    2015-01-01

    In this paper, we implement an Optical Flat Comb Source generating a coherent super-channel operating at 1 Tbps using Wavelength Division Multiplexing-Nyquist (WDM-Nyquist) and Coherent Optical-Orthogonal Frequency Division Multiplexing (CO-OFDM) approaches with 12.5 GHz channel spacing. We evaluate through simulation the performance of the two techniques for generating Dual Polarization Quadrature-Amplitude Modulation based on 16 (DP-16QAM). We first study the robustness of CO-OFDM system to the receiver constraints such as Analog-to-Digital Converters (ADCs) speed and the receiver bandwidth in Back-to-Back link (Optical Signal-to- Noise Ratio (OSNR)) and over longhaul dispersion compensated links using Standard Single Mode Fiber (SSMF). We find that CO-OFDM requires 6 Samples per Symbol (SpS) with a large receiver bandwidth (2.25× Baud rate) to achieve the same performance of WDM-Nyquist system in terms of SNR. However, the CO-OFDM system needs more than 6 SpS to achieve the same distances as WDM-Nyquist. We also study the impact of the input power level in terms of OSNR for CO-OFDM and WDM-Nyquist systems in order to evaluate the robustness of both systems to the nonlinear effects.

  19. Endosomal pH in neuronal signaling and synaptic transmission: role of Na+/H+ exchanger NHE5

    PubMed Central

    Diering, Graham H.; Numata, Masayuki

    2013-01-01

    Neuronal precursor cells extend multiple neurites during development, one of which extends to form an axon whereas others develop into dendrites. Chemical stimulation of N-methyl D-aspartate (NMDA) receptor in fully-differentiated neurons induces projection of dendritic spines, small spikes protruding from dendrites, thereby establishing another layer of polarity within the dendrite. Neuron-enriched Na+/H+ exchanger NHE5 contributes to both neurite growth and dendritic spine formation. In resting neurons and neuro-endocrine cells, neuron-enriched NHE5 is predominantly associated with recycling endosomes where it colocalizes with nerve growth factor (NGF) receptor TrkA. NHE5 potently acidifies the lumen of TrkA-positive recycling endosomes and regulates cell-surface targeting of TrkA, whereas chemical stimulation of NMDA receptors rapidly recruits NHE5 to dendritic spines, alkalinizes dendrites and down-regulates the dendritic spine formation. Possible roles of NHE5 in neuronal signaling via proton movement in subcellular compartments are discussed. PMID:24454292

  20. Implementation of orthogonal frequency division multiplexing (OFDM) and advanced signal processing for elastic optical networking in accordance with networking and transmission constraints

    NASA Astrophysics Data System (ADS)

    Johnson, Stanley

    An increasing adoption of digital signal processing (DSP) in optical fiber telecommunication has brought to the fore several interesting DSP enabled modulation formats. One such format is orthogonal frequency division multiplexing (OFDM), which has seen great success in wireless and wired RF applications, and is being actively investigated by several research groups for use in optical fiber telecom. In this dissertation, I present three implementations of OFDM for elastic optical networking and distributed network control. The first is a field programmable gate array (FPGA) based real-time implementation of a version of OFDM conventionally known as intensity modulation and direct detection (IMDD) OFDM. I experimentally demonstrate the ability of this transmission system to dynamically adjust bandwidth and modulation format to meet networking constraints in an automated manner. To the best of my knowledge, this is the first real-time software defined networking (SDN) based control of an OFDM system. In the second OFDM implementation, I experimentally demonstrate a novel OFDM transmission scheme that supports both direct detection and coherent detection receivers simultaneously using the same OFDM transmitter. This interchangeable receiver solution enables a trade-off between bit rate and equipment cost in network deployment and upgrades. I show that the proposed transmission scheme can provide a receiver sensitivity improvement of up to 1.73 dB as compared to IMDD OFDM. I also present two novel polarization analyzer based detection schemes, and study their performance using experiment and simulation. In the third implementation, I present an OFDM pilot-tone based scheme for distributed network control. The first instance of an SDN-based OFDM elastic optical network with pilot-tone assisted distributed control is demonstrated. An improvement in spectral efficiency and a fast reconfiguration time of 30 ms have been achieved in this experiment. Finally, I

  1. Allosteric inhibition of SHP2 phosphatase inhibits cancers driven by receptor tyrosine kinases.

    PubMed

    Chen, Ying-Nan P; LaMarche, Matthew J; Chan, Ho Man; Fekkes, Peter; Garcia-Fortanet, Jorge; Acker, Michael G; Antonakos, Brandon; Chen, Christine Hiu-Tung; Chen, Zhouliang; Cooke, Vesselina G; Dobson, Jason R; Deng, Zhan; Fei, Feng; Firestone, Brant; Fodor, Michelle; Fridrich, Cary; Gao, Hui; Grunenfelder, Denise; Hao, Huai-Xiang; Jacob, Jaison; Ho, Samuel; Hsiao, Kathy; Kang, Zhao B; Karki, Rajesh; Kato, Mitsunori; Larrow, Jay; La Bonte, Laura R; Lenoir, Francois; Liu, Gang; Liu, Shumei; Majumdar, Dyuti; Meyer, Matthew J; Palermo, Mark; Perez, Lawrence; Pu, Minying; Price, Edmund; Quinn, Christopher; Shakya, Subarna; Shultz, Michael D; Slisz, Joanna; Venkatesan, Kavitha; Wang, Ping; Warmuth, Markus; Williams, Sarah; Yang, Guizhi; Yuan, Jing; Zhang, Ji-Hu; Zhu, Ping; Ramsey, Timothy; Keen, Nicholas J; Sellers, William R; Stams, Travis; Fortin, Pascal D

    2016-07-01

    The non-receptor protein tyrosine phosphatase SHP2, encoded by PTPN11, has an important role in signal transduction downstream of growth factor receptor signalling and was the first reported oncogenic tyrosine phosphatase. Activating mutations of SHP2 have been associated with developmental pathologies such as Noonan syndrome and are found in multiple cancer types, including leukaemia, lung and breast cancer and neuroblastoma. SHP2 is ubiquitously expressed and regulates cell survival and proliferation primarily through activation of the RAS–ERK signalling pathway. It is also a key mediator of the programmed cell death 1 (PD-1) and B- and T-lymphocyte attenuator (BTLA) immune checkpoint pathways. Reduction of SHP2 activity suppresses tumour cell growth and is a potential target of cancer therapy. Here we report the discovery of a highly potent (IC50 = 0.071 μM), selective and orally bioavailable small-molecule SHP2 inhibitor, SHP099, that stabilizes SHP2 in an auto-inhibited conformation. SHP099 concurrently binds to the interface of the N-terminal SH2, C-terminal SH2, and protein tyrosine phosphatase domains, thus inhibiting SHP2 activity through an allosteric mechanism. SHP099 suppresses RAS–ERK signalling to inhibit the proliferation of receptor-tyrosine-kinase-driven human cancer cells in vitro and is efficacious in mouse tumour xenograft models. Together, these data demonstrate that pharmacological inhibition of SHP2 is a valid therapeutic approach for the treatment of cancers. PMID:27362227

  2. Extracellular Calcium Modulates Actions of Orthosteric and Allosteric Ligands on Metabotropic Glutamate Receptor 1α*

    PubMed Central

    Jiang, Jason Y.; Nagaraju, Mulpuri; Meyer, Rebecca C.; Zhang, Li; Hamelberg, Donald; Hall, Randy A.; Brown, Edward M.; Conn, P. Jeffrey; Yang, Jenny J.

    2014-01-01

    Metabotropic glutamate receptor 1α (mGluR1α), a member of the family C G protein-coupled receptors, is emerging as a potential drug target for various disorders, including chronic neuronal degenerative diseases. In addition to being activated by glutamate, mGluR1α is also modulated by extracellular Ca2+. However, the underlying mechanism is unknown. Moreover, it has long been challenging to develop receptor-specific agonists due to homologies within the mGluR family, and the Ca2+-binding site(s) on mGluR1α may provide an opportunity for receptor-selective targeting by therapeutics. In the present study, we show that our previously predicted Ca2+-binding site in the hinge region of mGluR1α is adjacent to the site where orthosteric agonists and antagonists bind on the extracellular domain of the receptor. Moreover, we found that extracellular Ca2+ enhanced mGluR1α-mediated intracellular Ca2+ responses evoked by the orthosteric agonist l-quisqualate. Conversely, extracellular Ca2+ diminished the inhibitory effect of the mGluR1α orthosteric antagonist (S)-α-methyl-4-carboxyphenylglycine. In addition, selective positive (Ro 67-4853) and negative (7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester) allosteric modulators of mGluR1α potentiated and inhibited responses to extracellular Ca2+, respectively, in a manner similar to their effects on the response of mGluR1α to glutamate. Mutations at residues predicted to be involved in Ca2+ binding, including E325I, had significant effects on the modulation of responses to the orthosteric agonist l-quisqualate and the allosteric modulator Ro 67-4853 by extracellular Ca2+. These studies reveal that binding of extracellular Ca2+ to the predicted Ca2+-binding site in the extracellular domain of mGluR1α modulates not only glutamate-evoked signaling but also the actions of both orthosteric ligands and allosteric modulators on mGluR1α. PMID:24280223

  3. Studying allosteric regulation in metal sensor proteins using computational methods.

    PubMed

    Chakravorty, Dhruva K; Merz, Kenneth M

    2014-01-01

    In this chapter, we describe advances made in understanding the mechanism of allosteric regulation of DNA operator binding in the ArsR/SmtB family of metal-sensing proteins using computational methods. The paradigm, zinc-sensing transcriptional repressor Staphylococcus aureus CzrA represents an excellent model system to understand how metal sensor proteins maintain cellular metal homeostasis. Here, we discuss studies that helped to characterize a metal ion-mediated hydrogen-bonding pathway (HBP) that plays a dominant role in the allosteric mechanism of DNA operator binding in these proteins. The chapter discusses computational methods used to provide a molecular basis for the large conformational motions and allosteric coupling free energy (~6kcal/mol) associated with Zn(II) binding in CzrA. We present an accurate and convenient means by which to include metal ions in the nuclear magnetic resonance (NMR) structure determination process using molecular dynamics (MD) constrained by NMR-derived data. The method provides a realistic and physically viable description of the metal-binding site(s) and has potentially broad applicability in the structure determination of metal ion-bound proteins, protein folding, and metal template protein-design studies. Finally, our simulations provide strong support for a proposed HBP that physically connects the metal-binding residue, His97, to the DNA-binding interface through the αR helix that is present only in the Zn(II)-bound state. We find the interprotomer hydrogen bond interaction to be significantly stronger (~8kcal/mol) at functional allosteric metal-binding sites compared to the apo proteins. This interaction works to overcome the considerable disorder at these hydrogen-bonding sites in apo protein and functions as a "switch" to lock in a weak DNA-binding conformation once metal is bound. This interaction is found to be considerably weaker in nonresponsive metal-binding sites. These findings suggest a conserved functional

  4. Dynamic Transmission of Protein Allostery without Structural Change: Spatial Pathways or Global Modes?

    PubMed

    McLeish, Tom C B; Cann, Martin J; Rodgers, Thomas L

    2015-09-15

    We examine the contrast between mechanisms for allosteric signaling that involve structural change, and those that do not, from the perspective of allosteric pathways. In particular we treat in detail the case of fluctuation-allostery by which amplitude modulation of the thermal fluctuations of the elastic normal modes conveys the allosteric signal, and address the question of what an allosteric pathway means in this case. We find that a perturbation theory of thermal elastic solids and nonperturbative approach (by super-coarse-graining elasticity into internal bending modes) have opposite signatures in their structure of correlated pathways. We illustrate the effect from analysis of previous results from GlxR of Corynebacterium glutamicum, an example of the CRP/FNR transcription family of allosteric homodimers. We find that the visibility of both correlated pathways and disconnected sites of correlated motion in this protein suggests that mechanisms of local elastic stretch and bend are recruited for the purpose of creating and controlling allosteric cooperativity. PMID:26338443

  5. Exploring signal transduction in heteromultimeric protein based on energy dissipation model.

    PubMed

    Ma, Cheng-Wei; Xiu, Zhi-Long; Zeng, An-Ping

    2015-01-01

    Dynamic intersubunit interactions are key elements in the regulation of many biological systems. A better understanding of how subunits interact with each other and how their interactions are related to dynamic protein structure is a fundamental task in biology. In this paper, a heteromultimeric allosteric protein, Corynebacterium glutamicum aspartokinase, is used as a model system to explore the signal transduction involved in intersubunit interactions and allosteric communication with an emphasis on the intersubunit signaling process. For this purpose, energy dissipation simulation and network construction are conducted for each subunit and the whole protein. Comparison with experimental results shows that the new approach is able to predict all the mutation sites that have been experimentally proved to desensitize allosteric regulation of the enzyme. Additionally, analysis revealed that the function of the effector threonine is to facilitate the binding of the two subunits without contributing to the allosteric communication. During the allosteric regulation upon the binding of the effector lysine, signals can be transferred from the β-subunit to the catalytic site of the α-subunit through both a direct way of intersubunit signal transduction, and an indirect way: first, to the regulatory region of the α-subunit by intersubunit signal transduction and then to the catalytic region by intramolecular signal transduction. Therefore, the new approach is able to illustrate the diversity of the underlying mechanisms when the strength of feedback inhibition by the effector(s) is modulated, providing useful information that has potential applications in engineering heteromultimeric allosteric regulation. PMID:24279729

  6. Effects of the Dopamine D2 Allosteric Modulator, PAOPA, on the Expression of GRK2, Arrestin-3, ERK1/2, and on Receptor Internalization

    PubMed Central

    Basu, Dipannita; Tian, Yuxin; Bhandari, Jayant; Jiang, Jian Ru; Hui, Patricia; Johnson, Rodney L.; Mishra, Ram K.

    2013-01-01

    The activity of G protein-coupled receptors (GPCRs) is intricately regulated by a range of intracellular proteins, including G protein-coupled kinases (GRKs) and arrestins. Understanding the effects of ligands on these signaling pathways could provide insights into disease pathophysiologies and treatment. The dopamine D2 receptor is a GPCR strongly implicated in the pathophysiology of a range of neurological and neuropsychiatric disorders, particularly schizophrenia. Previous studies from our lab have shown the preclinical efficacy of a novel allosteric drug, 3(R)- [(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA), in attenuating schizophrenia-like behavioural abnormalities in rodent models of the disease. As an allosteric modulator, PAOPA binds to a site on the D2 receptor, which is distinct from the endogenous ligand-binding site, in order to modulate the binding of the D2 receptor ligand, dopamine. The exact signaling pathways affected by this allosteric modulator are currently unknown. The objectives of this study were to decipher the in vivo effects, in rats, of chronic PAOPA administration on D2 receptor regulatory and downstream molecules, including GRK2, arrestin-3 and extracellular receptor kinase (ERK) 1/2. Additionally, an in vitro cellular model was also used to study PAOPA’s effects on D2 receptor internalization. Results from western immunoblots showed that chronic PAOPA treatment increased the striatal expression of GRK2 by 41%, arrestin-3 by 34%, phospho-ERK1 by 51% and phospho-ERK2 by 36%. Results also showed that the addition of PAOPA to agonist treatment in cells increased D2 receptor internalization by 33%. This study provides the foundational evidence of putative signaling pathways, and changes in receptor localization, affected by treatment with PAOPA. It improves our understanding on the diverse mechanisms of action of allosteric modulators, while advancing PAOPA’s development into a novel drug for the improved

  7. Illumination distribution and signal transmission for indoor visible light communication with different light-emitting diode arrays and pre-equality circuits

    NASA Astrophysics Data System (ADS)

    Chen, Hsi-Chao; Liou, Cheng-Jyun; Siao, Syuan-Ruei

    2015-11-01

    The purpose of this study was to seek the optimal design for light-emitting diode (LED) arrays and pre-equality circuits in indoor visible lighting illumination combined with communication. The optical and communicational properties of illumination distribution and signal transmission were investigated. These illumination distributions of array sources were derivate and simulated and actually can be used in free-space communication. Simulated results show the total flux size was rectangle>radial>circlearray, and real measurements also showed the total flux was rectangle>radial>circlearray. The simulated and measured results have a similarity of over 98% by normalized cross correlation. In addition, when the distance of the installed lamp from the wall was 1 m, the rectangular array had the best illumination uniformity of 77.24%, and the size of uniformity was the rectangle>radial≈circle array. Finally, the gain and constant-current pre-equality circuits were used in free-space communication with a carrier frequency from 1 KHz to 1 MHz at a distance of 1.8 m. Both the received signal intensity and divergence angle were rectangle>radial>circle array. The constant-current pre-equality circuit could add the divergence angle from ±18.6 deg to ±36.68 deg in the rectangle array at a carrier frequency of 1 MHz.

  8. Intramolecular allosteric communication in dopamine D2 receptor revealed by evolutionary amino acid covariation

    PubMed Central

    Sung, Yun-Min; Wilkins, Angela D.; Rodriguez, Gustavo J.; Wensel, Theodore G.; Lichtarge, Olivier

    2016-01-01

    The structural basis of allosteric signaling in G protein-coupled receptors (GPCRs) is important in guiding design of therapeutics and understanding phenotypic consequences of genetic variation. The Evolutionary Trace (ET) algorithm previously proved effective in redesigning receptors to mimic the ligand specificities of functionally distinct homologs. We now expand ET to consider mutual information, with validation in GPCR structure and dopamine D2 receptor (D2R) function. The new algorithm, called ET-MIp, identifies evolutionarily relevant patterns of amino acid covariations. The improved predictions of structural proximity and D2R mutagenesis demonstrate that ET-MIp predicts functional interactions between residue pairs, particularly potency and efficacy of activation by dopamine. Remarkably, although most of the residue pairs chosen for mutagenesis are neither in the binding pocket nor in contact with each other, many exhibited functional interactions, implying at-a-distance coupling. The functional interaction between the coupled pairs correlated best with the evolutionary coupling potential derived from dopamine receptor sequences rather than with broader sets of GPCR sequences. These data suggest that the allosteric communication responsible for dopamine responses is resolved by ET-MIp and best discerned within a short evolutionary distance. Most double mutants restored dopamine response to wild-type levels, also suggesting that tight regulation of the response to dopamine drove the coevolution and intramolecular communications between coupled residues. Our approach provides a general tool to identify evolutionary covariation patterns in small sets of close sequence homologs and to translate them into functional linkages between residues. PMID:26979958

  9. Robust Stimulation of W1282X-CFTR Channel Activity by a Combination of Allosteric Modulators

    PubMed Central

    Wang, Wei; Hong, Jeong S.; Rab, Andras; Sorscher, Eric J.; Kirk, Kevin L.

    2016-01-01

    W1282X is a common nonsense mutation among cystic fibrosis patients that results in the production of a truncated Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. Here we show that the channel activity of the W1282X-CFTR polypeptide is exceptionally low in excised membrane patches at normally saturating doses of ATP and PKA (single channel open probability (PO) < 0.01). However, W1282X-CFTR channels were stimulated by two CFTR modulators, the FDA-approved VX-770 and the dietary compound curcumin. Each of these compounds is an allosteric modulator of CFTR gating that promotes channel activity in the absence of the native ligand, ATP. Although W1282X-CFTR channels were stimulated by VX-770 in the absence of ATP their activities remained dependent on PKA phosphorylation. Thus, activated W1282X-CFTR channels should remain under physiologic control by cyclic nucleotide signaling pathways in vivo. VX-770 and curcumin exerted additive effects on W1282X-CFTR channel gating (opening/closing) in excised patches such that the Po of the truncated channel approached unity (> 0.9) when treated with both modulators. VX-770 and curcumin also additively stimulated W1282X-CFTR mediated currents in polarized FRT epithelial monolayers. In this setting, however, the stimulated W1282X-CFTR currents were smaller than those mediated by wild type CFTR (3–5%) due presumably to lower expression levels or cell surface targeting of the truncated protein. Combining allosteric modulators of different mechanistic classes is worth considering as a treatment option for W1282X CF patients perhaps when coupled with maneuvers to increase expression of the truncated protein. PMID:27007499

  10. Robust Stimulation of W1282X-CFTR Channel Activity by a Combination of Allosteric Modulators.

    PubMed

    Wang, Wei; Hong, Jeong S; Rab, Andras; Sorscher, Eric J; Kirk, Kevin L

    2016-01-01

    W1282X is a common nonsense mutation among cystic fibrosis patients that results in the production of a truncated Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. Here we show that the channel activity of the W1282X-CFTR polypeptide is exceptionally low in excised membrane patches at normally saturating doses of ATP and PKA (single channel open probability (PO) < 0.01). However, W1282X-CFTR channels were stimulated by two CFTR modulators, the FDA-approved VX-770 and the dietary compound curcumin. Each of these compounds is an allosteric modulator of CFTR gating that promotes channel activity in the absence of the native ligand, ATP. Although W1282X-CFTR channels were stimulated by VX-770 in the absence of ATP their activities remained dependent on PKA phosphorylation. Thus, activated W1282X-CFTR channels should remain under physiologic control by cyclic nucleotide signaling pathways in vivo. VX-770 and curcumin exerted additive effects on W1282X-CFTR channel gating (opening/closing) in excised patches such that the Po of the truncated channel approached unity (> 0.9) when treated with both modulators. VX-770 and curcumin also additively stimulated W1282X-CFTR mediated currents in polarized FRT epithelial monolayers. In this setting, however, the stimulated W1282X-CFTR currents were smaller than those mediated by wild type CFTR (3-5%) due presumably to lower expression levels or cell surface targeting of the truncated protein. Combining allosteric modulators of different mechanistic classes is worth considering as a treatment option for W1282X CF patients perhaps when coupled with maneuvers to increase expression of the truncated protein. PMID:27007499

  11. Intramolecular allosteric communication in dopamine D2 receptor revealed by evolutionary amino acid covariation.

    PubMed

    Sung, Yun-Min; Wilkins, Angela D; Rodriguez, Gustavo J; Wensel, Theodore G; Lichtarge, Olivier

    2016-03-29

    The structural basis of allosteric signaling in G protein-coupled receptors (GPCRs) is important in guiding design of therapeutics and understanding phenotypic consequences of genetic variation. The Evolutionary Trace (ET) algorithm previously proved effective in redesigning receptors to mimic the ligand specificities of functionally distinct homologs. We now expand ET to consider mutual information, with validation in GPCR structure and dopamine D2 receptor (D2R) function. The new algorithm, called ET-MIp, identifies evolutionarily relevant patterns of amino acid covariations. The improved predictions of structural proximity and D2R mutagenesis demonstrate that ET-MIp predicts functional interactions between residue pairs, particularly potency and efficacy of activation by dopamine. Remarkably, although most of the residue pairs chosen for mutagenesis are neither in the binding pocket nor in contact with each other, many exhibited functional interactions, implying at-a-distance coupling. The functional interaction between the coupled pairs correlated best with the evolutionary coupling potential derived from dopamine receptor sequences rather than with broader sets of GPCR sequences. These data suggest that the allosteric communication responsible for dopamine responses is resolved by ET-MIp and best discerned within a short evolutionary distance. Most double mutants restored dopamine response to wild-type levels, also suggesting that tight regulation of the response to dopamine drove the coevolution and intramolecular communications between coupled residues. Our approach provides a general tool to identify evolutionary covariation patterns in small sets of close sequence homologs and to translate them into functional linkages between residues. PMID:26979958

  12. Reviews Book: SEP Communications: Transmitting and Receiving Signals Book: Gliding for Gold Book: Radioactivity: A History of a Mysterious Science Book: The New Quantum Age Books: The Art of Science and The Oxford Book of Modern Science Writing Equipment: SEP Analogue/digital transmission unit Equipment: SEP Optical signal transmission set Book: Stars and their Spectra Book: Voicebox: The Physics and Evolution of Speech Web Watch

    NASA Astrophysics Data System (ADS)

    2012-03-01

    WE RECOMMEND Transmitting and Receiving Signals SEP booklet transmits knowledge The New Quantum Age Understanding modern quantum theory The Art of Science and The Oxford Book of Modern Science Writing Anthologies bring science to life SEP Analogue/digital transmission unit Kit transmits signal between two points SEP Optical signal transmission set Optical kit shows light transmission Stars and their Spectra New book for teaching astrophysics WORTH A LOOK Gliding for Gold Take a journey through the physics of winter sports Radioactivity: A History of a Mysterious Science Book looks at history of radioactivity Voicebox: The Physics and Evolution of Speech TExploring the evolution of the voice WEB WATCH An interactive program with promise?

  13. Allosteric Communication in the Dynein Motor Domain

    PubMed Central

    Bhabha, Gira; Cheng, Hui-Chun; Zhang, Nan; Moeller, Arne; Liao, Maofu; Speir, Jeffrey A.; Cheng, Yifan; Vale, Ronald D.

    2014-01-01

    SUMMARY Dyneins power microtubule motility using ring-shaped, AAA-containing motor domains. Here, we report X-ray and electron microscopy (EM) structures of yeast dynein bound to different ATP analogs, which collectively provide insight into the roles of dynein’s two major ATPase sites, AAA1 and AAA3, in the conformational change mechanism. ATP binding to AAA1 triggers a cascade of conformational changes that propagate to all six AAA domains and cause a large movement of the “linker,” dynein’s mechanical element. In contrast to the role of AAA1 in driving motility, nucleotide transitions in AAA3 gate the transmission of conformational changes between AAA1 and the linker, suggesting that AAA3 acts as a regulatory switch. Further structural and mutational studies also uncover a role for the linker in regulating the catalytic cycle of AAA1. Together, these results reveal how dynein’s two major ATP-binding sites initiate and modulate conformational changes in the motor domain during motility. PMID:25417161

  14. Sequence Analysis and Molecular Characterization of Clonorchis sinensis Hexokinase, an Unusual Trimeric 50-kDa Glucose-6-Phosphate-Sensitive Allosteric Enzyme

    PubMed Central

    Chen, Tingjin; Ning, Dan; Sun, Hengchang; Li, Ran; Shang, Mei; Li, Xuerong; Wang, Xiaoyun; Chen, Wenjun; Liang, Chi; Li, Wenfang; Mao, Qiang; Li, Ye; Deng, Chuanhuan; Wang, Lexun; Wu, Zhongdao; Huang, Yan; Xu, Jin; Yu, Xinbing

    2014-01-01

    Clonorchiasis, which is induced by the infection of Clonorchis sinensis (C. sinensis), is highly associated with cholangiocarcinoma. Because the available examination, treatment and interrupting transmission provide limited opportunities to prevent infection, it is urgent to develop integrated strategies to prevent and control clonorchiasis. Glycolytic enzymes are crucial molecules for trematode survival and have been targeted for drug development. Hexokinase of C. sinensis (CsHK), the first key regulatory enzyme of the glycolytic pathway, was characterized in this study. The calculated molecular mass (Mr) of CsHK was 50.0 kDa. The obtained recombinant CsHK (rCsHK) was a homotrimer with an Mr of approximately 164 kDa, as determined using native PAGE and gel filtration. The highest activity was obtained with 50 mM glycine-NaOH at pH 10 and 100 mM Tris-HCl at pH 8.5 and 10. The kinetics of rCsHK has a moderate thermal stability. Compared to that of the corresponding negative control, the enzymatic activity was significantly inhibited by praziquantel (PZQ) and anti-rCsHK serum. rCsHK was homotropically and allosterically activated by its substrates, including glucose, mannose, fructose, and ATP. ADP exhibited mixed allosteric effect on rCsHK with respect to ATP, while inorganic pyrophosphate (PPi) displayed net allosteric activation with various allosteric systems. Fructose behaved as a dose-dependent V activator with the substrate glucose. Glucose-6-phosphate (G6P) displayed net allosteric inhibition on rCsHK with respect to ATP or glucose with various allosteric systems in a dose-independent manner. There were differences in both mRNA and protein levels of CsHK among the life stages of adult worm, metacercaria, excysted metacercaria and egg of C. sinensis, suggesting different energy requirements during different development stages. Our study furthers the understanding of the biological functions of CsHK and supports the need to screen for small molecule inhibitors

  15. Allosteric Inhibition of the Neuropeptidase Neurolysin*

    PubMed Central

    Hines, Christina S.; Ray, Kallol; Schmidt, Jack J.; Xiong, Fei; Feenstra, Rolf W.; Pras-Raves, Mia; de Moes, Jan Peter; Lange, Jos H. M.; Melikishvili, Manana; Fried, Michael G.; Mortenson, Paul; Charlton, Michael; Patel, Yogendra; Courtney, Stephen M.; Kruse, Chris G.; Rodgers, David W.

    2014-01-01

    Neuropeptidases specialize in the hydrolysis of the small bioactive peptides that play a variety of signaling roles in the nervous and endocrine systems. One neuropeptidase, neurolysin, helps control the levels of the dopaminergic circuit modulator neurotensin and is a member of a fold group that includes the antihypertensive target angiotensin converting enzyme. We report the discovery of a potent inhibitor that, unexpectedly, binds away from the enzyme catalytic site. The location of the bound inhibitor suggests it disrupts activity by preventing a hinge-like motion associated with substrate binding and catalysis. In support of this model, the inhibition kinetics are mixed, with both noncompetitive and competitive components, and fluorescence polarization shows directly that the inhibitor reverses a substrate-associated conformational change. This new type of inhibition may have widespread utility in targeting neuropeptidases. PMID:25378390

  16. Signal Transduction Pathways in the Pentameric Ligand-Gated Ion Channels

    PubMed Central

    Mowrey, David; Chen, Qiang; Liang, Yuhe; Liang, Jie; Xu, Yan; Tang, Pei

    2013-01-01

    The mechanisms of allosteric action within pentameric ligand-gated ion channels (pLGICs) remain to be determined. Using crystallography, site-directed mutagenesis, and two-electrode voltage clamp measurements, we identified two functionally relevant sites in the extracellular (EC) domain of the bacterial pLGIC from Gloeobacter violaceus (GLIC). One site is at the C-loop region, where the NQN mutation (D91N, E177Q, and D178N) eliminated inter-subunit salt bridges in the open-channel GLIC structure and thereby shifted the channel activation to a higher agonist concentration. The other site is below the C-loop, where binding of the anesthetic ketamine inhibited GLIC currents in a concentration dependent manner. To understand how a perturbation signal in the EC domain, either resulting from the NQN mutation or ketamine binding, is transduced to the channel gate, we have used the Perturbation-based Markovian Transmission (PMT) model to determine dynamic responses of the GLIC channel and signaling pathways upon initial perturbations in the EC domain of GLIC. Despite the existence of many possible routes for the initial perturbation signal to reach the channel gate, the PMT model in combination with Yen's algorithm revealed that perturbation signals with the highest probability flow travel either via the β1–β2 loop or through pre-TM1. The β1–β2 loop occurs in either intra- or inter-subunit pathways, while pre-TM1 occurs exclusively in inter-subunit pathways. Residues involved in both types of pathways are well supported by previous experimental data on nAChR. The direct coupling between pre-TM1 and TM2 of the adjacent subunit adds new insight into the allosteric signaling mechanism in pLGICs. PMID:23667707

  17. Allosteric Inhibition of the Regulator of G Protein Signaling–Gα Protein–Protein Interaction by CCG-4986

    PubMed Central

    Blazer, Levi L.; Monroy, C. Aaron; Neubig, Richard R.

    2010-01-01

    Regulator of G protein signaling (RGS) proteins act to temporally modulate the activity of G protein subunits after G protein-coupled receptor activation. RGS proteins exert their effect by directly binding to the activated Gα subunit of the G protein, catalyzing the accelerated hydrolysis of GTP and returning the G protein to its inactive, heterotrimeric form. In previous studies, we have sought to inhibit this GTPase-accelerating protein activity of the RGS protein by using small molecules. In this study, we investigated the mechanism of CCG-4986 [methyl-N-[(4-chlorophenyl)sulfonyl]-4-nitro-benzenesulfinimidoate], a previously reported small-molecule RGS inhibitor. Here, we find that CCG-4986 inhibits RGS4 function through the covalent modification of two spatially distinct cysteine residues on RGS4. We confirm that modification of Cys132, located near the RGS/Gα interaction surface, modestly inhibits Gα binding and GTPase acceleration. In addition, we report that modification of Cys148, a residue located on the opposite face of RGS4, can disrupt RGS/Gα interaction through an allosteric mechanism that almost completely inhibits the Gα–RGS protein–protein interaction. These findings demonstrate three important points: 1) the modification of the Cys148 allosteric site results in significant changes to the RGS interaction surface with Gα; 2) this identifies a “hot spot” on RGS4 for binding of small molecules and triggering an allosteric change that may be significantly more effective than targeting the actual protein-protein interaction surface; and 3) because of the modification of a positional equivalent of Cys148 in RGS8 by CCG-4986, lack of inhibition indicates that RGS proteins exhibit fundamental differences in their responses to small-molecule ligands. PMID:20530129

  18. A novel allosteric mechanism in the cysteine peptidase cathepsin K discovered by computational methods

    NASA Astrophysics Data System (ADS)

    Novinec, Marko; Korenč, Matevž; Caflisch, Amedeo; Ranganathan, Rama; Lenarčič, Brigita; Baici, Antonio

    2014-02-01

    Allosteric modifiers have the potential to fine-tune enzyme activity. Therefore, targeting allosteric sites is gaining increasing recognition as a strategy in drug design. Here we report the use of computational methods for the discovery of the first small-molecule allosteric inhibitor of the collagenolytic cysteine peptidase cathepsin K, a major target for the treatment of osteoporosis. The molecule NSC13345 is identified by high-throughput docking of compound libraries to surface sites on the peptidase that are connected to the active site by an evolutionarily conserved network of residues (protein sector). The crystal structure of the complex shows that NSC13345 binds to a novel allosteric site on cathepsin K. The compound acts as a hyperbolic mixed modifier in the presence of a synthetic substrate, it completely inhibits collagen degradation and has good selectivity for cathepsin K over related enzymes. Altogether, these properties qualify our methodology and NSC13345 as promising candidates for allosteric drug design.

  19. Antitumoral activity of allosteric inhibitors of protein kinase CK2

    PubMed Central

    Sautel, Céline F.; Teillet, Florence; Barette, Caroline; Lafanechere, Laurence; Receveur-Brechot, Veronique; Cochet, Claude

    2011-01-01

    Introduction Due to its physiological role into promoting cell survival and its dysregulation in most cancer cells, protein kinase CK2 is a relevant physiopathological target for development of chemical inhibitors. We report the discovery of azonaphthalene derivatives, as a new family of highly specific CK2 inhibitors. First, we demonstrated that CK2 inhibition (IC50= 0.4 μM) was highly specific, reversible and non ATP-competitive. Small Angle X-ray Scattering experiments showed that this inhibition was due to large conformational change of CK2α upon binding of these inhibitors. We showed that several compounds of the family were cell-potent CK2 inhibitors promoting cell cycle arrest of human glioblastoma U373 cells. Finally, in vitro and in vivo assays showed that these compounds could decrease U373 cell tumor mass by 83% emphasizing their efficacy against these apoptosis-resistant tumors. In contrast, Azonaphthalene derivatives inactive on CK2 activity showed no effect in colony formation and tumor regression assays. These findings illustrate the emergence of nonclassical CK2 inhibitors and provide exciting opportunities for the development of novel allosteric CK2 inhibitors. Background CK2 is an emerging therapeutic target and ATP-competitive inhibitors have been identified. CK2 is endowed with specific structural features providing alternative strategies for inhibition. Results Azonaphthalene compounds are allosteric CK2 inhibitors showing antitumor activity. Conclusion CK2 may be targeted allosterically. Significance These inhibitors provide a foundation for a new paradigm for specific CK2 inhibition. PMID:22184283

  20. ATP Is an Allosteric Inhibitor of Coxsackievirus B3 Polymerase.

    PubMed

    Karr, Jonathan P; Peersen, Olve B

    2016-07-19

    The RNA-dependent RNA polymerases from positive-strand RNA viruses, such as picornaviruses and flaviviruses, close their active sites for catalysis via a unique NTP-induced conformational change in the palm domain. Combined with a fully prepositioned templating nucleotide, this mechanism is error-prone and results in a distribution of random mutations in the viral progeny often described as a quasi-species. Here we examine the extent to which noncognate NTPs competitively inhibit single-cycle elongation by coxsackievirus B3 3D(pol), a polymerase that generates three to four mutations per 10 kb of RNA synthesized during viral infection. Using an RNA with a templating guanosine combined with 2-aminopurine fluorescence as a reporter for elongation, we find that the cognate CTP has a Km of 24 μM and the three noncognate nucleotides competitively inhibit the reaction with Kic values of 500 μM for GTP, 1300 μM for ATP, and 3000 μM for UTP. Unexpectedly, ATP also acted as an uncompetitive inhibitor with a Kiu of 1800 μM, resulting in allosteric modulation of 3D(pol) that slowed the polymerase elongation rate ≈4-fold. ATP uncompetitive inhibition required the β- and γ-phosphates, and its extent was significantly diminished in two previously characterized low-fidelity polymerases. This led to further mutational analysis and the identification of a putative allosteric binding site below the NTP entry channel at the interface of conserved motifs A and D, although cocrystallization failed to reveal any density for bound ATP in this pocket. The potential role of an ATP allosteric effect during the virus life cycle is discussed. PMID:27319576

  1. Discovery and Characterization of Novel Subtype-Selective Allosteric Agonists for the Investigation of M1 Receptor Function in the Central Nervous System

    PubMed Central

    2009-01-01

    Cholinergic transmission in the forebrain is mediated primarily by five subtypes of muscarinic acetylcholine receptors (mAChRs), termed M1−M5. Of the mAChR subtypes, M1 is among the most heavily expressed in regions that are critical for learning and memory and has been viewed as the most critical mAChR subtype for memory and attention mechanisms. Unfortunately, it has been difficult to develop selective activators of M1 and other individual mAChR subtypes, which has prevented detailed studies of the functional roles of selective activation of M1. Using a functional high-throughput screening and subsequent diversity-oriented synthesis approach, we have discovered a novel series of highly selective M1 allosteric agonists. These compounds activate M1 with EC50 values in the 150−500 nM range and have unprecedented, clean ancillary pharmacology (no substantial activity at 10 μM across a large panel of targets). Targeted mutagenesis revealed a potentially novel allosteric binding site in the third extracellular loop of the M1 receptor for these allosteric agonists. Optimized compounds, such as VU0357017, provide excellent brain exposure after systemic dosing and have robust in vivo efficacy in reversing scopolamine-induced deficits in a rodent model of contextual fear conditioning. This series of selective M1 allosteric agonists provides critical research tools to allow dissection of M1-mediated effects in the CNS and potential leads for novel treatments for Alzheimer’s disease and schizophrenia. PMID:21961051

  2. Exploring the allosteric mechanism of dihydrodipicolinate synthase by reverse engineering of the allosteric inhibitor binding sites and its application for lysine production.

    PubMed

    Geng, Feng; Chen, Zhen; Zheng, Ping; Sun, Jibin; Zeng, An-Ping

    2013-03-01

    Dihydrodipicolinate synthase (DHDPS, EC 4.2.1.52) catalyzes the first committed reaction of L-lysine biosynthesis in bacteria and plants and is allosterically regulated by L-lysine. In previous studies, DHDPSs from different species were proved to have different sensitivity to L-lysine inhibition. In this study, we investigated the key determinants of feedback regulation between two industrially important DHDPSs, the L-lysine-sensitive DHDPS from Escherichia coli and L-lysine-insensitive DHDPS from Corynebacterium glutamicum, by sequence and structure comparisons and site-directed mutation. Feedback inhibition of E. coli DHDPS was successfully alleviated after substitution of the residues around the inhibitor's binding sites with those of C. glutamicum DHDPS. Interestingly, mutagenesis of the lysine binding sites of C. glutamicum DHDPS according to E. coli DHDPS did not recover the expected feedback inhibition but an activation of DHDPS by L-lysine, probably due to differences in the allosteic signal transduction in the DHDPS of these two organisms. Overexpression of L-lysine-insensitive E. coli DHDPS mutants in E. coli MG1655 resulted in an improvement of L-lysine production yield by 46 %. PMID:22644522

  3. Nor-seco-cucurbit[10]uril exhibits homotropic allosterism.

    PubMed

    Huang, Wei-Hao; Liu, Simin; Zavalij, Peter Y; Isaacs, Lyle

    2006-11-22

    The condensation of glycoluril and formaldehyde in concentrated HCl at 50 degrees C delivers nor-seco-cucurbit[10]uril (ns-CB [10]). 1H NMR and X-ray crystallographic evidence indicates that the two cavities of ns-CB[10] accommodate guests that are typically bound within CB[6] or CB[7]. Several interesting types of selectivity are possible within these ternary complexes-top/center isomerism, diastereoselective complexation of chiral (but racemic) guest pairs, and guest size controlled homotropic allosterism. PMID:17105250

  4. Bioinformatic scaling of allosteric interactions in biomedical isozymes

    NASA Astrophysics Data System (ADS)

    Phillips, J. C.

    2016-09-01

    Allosteric (long-range) interactions can be surprisingly strong in proteins of biomedical interest. Here we use bioinformatic scaling to connect prior results on nonsteroidal anti-inflammatory drugs to promising new drugs that inhibit cancer cell metabolism. Many parallel features are apparent, which explain how even one amino acid mutation, remote from active sites, can alter medical results. The enzyme twins involved are cyclooxygenase (aspirin) and isocitrate dehydrogenase (IDH). The IDH results are accurate to 1% and are overdetermined by adjusting a single bioinformatic scaling parameter. It appears that the final stage in optimizing protein functionality may involve leveling of the hydrophobic limits of the arms of conformational hydrophilic hinges.

  5. The allosteric modulation of lipases and its possible biological relevance

    PubMed Central

    Köhler, Jens; Wünsch, Bernhard

    2007-01-01

    Background During the development of an enantioselective synthesis using the lipase from Mucor miehei an unusual reaction course was observed, which was analyzed precisely. For the first time an allosteric modulation of a lipase changing its selectivity was shown. Theory Considering the biological relevance of the discovered regulation mechanism we developed a theory that describes the regulation of energy homeostasis and fat metabolism. Conclusion This theory represents a new approach to explain the cause of the metabolic syndrome and provides an innovative basis for further research activity. PMID:17825093

  6. Allosteric modulators of the hERG K{sup +} channel

    SciTech Connect

    Yu, Zhiyi Klaasse, Elisabeth Heitman, Laura H. IJzerman, Adriaan P.

    2014-01-01

    Drugs that block the cardiac K{sup +} channel encoded by the human ether-à-go-go gene (hERG) have been associated with QT interval prolongation leading to proarrhythmia, and in some cases, sudden cardiac death. Because of special structural features of the hERG K{sup +} channel, it has become a promiscuous target that interacts with pharmaceuticals of widely varying chemical structures and a reason for concern in the pharmaceutical industry. The structural diversity suggests that multiple binding sites are available on the channel with possible allosteric interactions between them. In the present study, three reference compounds and nine compounds of a previously disclosed series were evaluated for their allosteric effects on the binding of [{sup 3}H]astemizole and [{sup 3}H]dofetilide to the hERG K{sup +} channel. LUF6200 was identified as an allosteric inhibitor in dissociation assays with both radioligands, yielding similar EC{sub 50} values in the low micromolar range. However, potassium ions increased the binding of the two radioligands in a concentration-dependent manner, and their EC{sub 50} values were not significantly different, indicating that potassium ions behaved as allosteric enhancers. Furthermore, addition of potassium ions resulted in a concentration-dependent leftward shift of the LUF6200 response curve, suggesting positive cooperativity and distinct allosteric sites for them. In conclusion, our investigations provide evidence for allosteric modulation of the hERG K{sup +} channel, which is discussed in the light of findings on other ion channels. - Highlights: • Allosteric modulators on the hERG K{sup +} channel were evaluated in binding assays. • LUF6200 was identified as a potent allosteric inhibitor. • Potassium ions were found to behave as allosteric enhancers. • Positive cooperativity and distinct allosteric sites for them were proposed.

  7. Transmission of single-carrier 400G signals (515.2-Gb/s) based on 128.8-GBaud PDM QPSK over 10,130- and 6,078 km terrestrial fiber links.

    PubMed

    Zhang, Junwen; Yu, Jianjun; Zhu, Benyuan; Li, Fan; Chien, Hung-Chang; Jia, Zhensheng; Cai, Yi; Li, Xinying; Xiao, Xin; Fang, Yuan; Wang, Yuanquan

    2015-06-29

    We experimentally demonstrate the coherent transmission system with the highest ETDM-based symbol rate of 128.8-GBaud over record breaking distances. We successfully transmitted single-carrier 515.2-Gb/s PDM-QPSK/9-QAM signals over 10,130km/6,078-km, respectively, over 100km spans of TeraWave SLA + fiber. To the best of our knowledge, it is the highest ETDM-based symbol rate reported so far, and the longest WDM transmission distance with single-carrier 400G signals. For the first time, the 515.2-Gb/s single-carrier PDM-QPSK signals in 200-GHz-grid are successfully transmitted over distance above 10,000km in terrestrial transmission environment. We have also demonstrated the transmission of single carrier 128.8-GBaud filtered QPSK signals in 100-GHz-grid over 6,078-km, which has the line spectral efficiency (SE) of 5.152 (b/s/Hz). PMID:26191665

  8. Real-time optical wireless transmissions of digital TV signals using white InGaN LEDs grown with an asymmetric quantum barrier.

    PubMed

    Tsai, Chia-Lung; Chen, Yen-Jen

    2015-10-19

    The feasibility of using InGaN LEDs grown with asymmetric barrier layer (ABL) as transmitters in visible light communications is investigated experimentally. Compared with normal LEDs, the improvement in the spontaneous emission rate due to enhanced carrier localization and better uniformity of carrier distribution in ABL-containing MQWs leads to the fabricated LEDs can exhibit a 32.6% (@ 350 mA) increase in emission intensity and a 10.5% increase in modulation bandwidth. After eliminating the slow-responding phosphorescent components emitting from the phosphor-converted white LEDs, an open eye-diagram at 180 Mb/s is demonstrated over a distance of 100 cm in directed line-of-sight optical links. With the use of proposed LEDs, real-time transmissions of digital TV signals over a moderate distance (~100 cm) in free space is shown to be available in a 150 Mbit/s white LED-based optical link with conventional on-off keying modulation. PMID:26480463

  9. Automated manual transmission controller

    DOEpatents

    Lawrie, Robert E.; Reed, Jr., Richard G.; Bernier, David R.

    1999-12-28

    A powertrain system for a hybrid vehicle. The hybrid vehicle includes a heat engine, such as a diesel engine, and an electric machine, which operates as both an electric motor and an alternator, to power the vehicle. The hybrid vehicle also includes a manual-style transmission configured to operate as an automatic transmission from the perspective of the driver. The engine and the electric machine drive an input shaft which in turn drives an output shaft of the transmission. In addition to driving the transmission, the electric machine regulates the speed of the input shaft in order to synchronize the input shaft during either an upshift or downshift of the transmission by either decreasing or increasing the speed of the input shaft. When decreasing the speed of the input shaft, the electric motor functions as an alternator to produce electrical energy which may be stored by a storage device. Operation of the transmission is controlled by a transmission controller which receives input signals and generates output signals to control shift and clutch motors to effect smooth launch, upshift shifts, and downshifts of the transmission, so that the transmission functions substantially as an automatic transmission from the perspective of the driver, while internally substantially functioning as a manual transmission.

  10. Dynamics of allosteric action in multisite protein modification

    NASA Astrophysics Data System (ADS)

    Milotti, Edoardo; Del Fabbro, Alessio; Dalla Pellegrina, Chiara; Chignola, Roberto

    2007-06-01

    Protein functions in cells may be activated or modified by the attachment of several kinds of chemical groups. While protein phosphorylation, i.e., the attachment of a phosphoryl (PO3-) group, is the most studied form of protein modification, and is known to regulate the functions of many proteins, protein behavior can also be modified by nitrosylation, acetylation, methylation, etc. A protein can have multiple modification sites, and displays some form of transition only when enough sites are modified. In a previous paper we have modeled the generic equilibrium properties of multisite protein modification [R. Chignola, C. Dalla Pellegrina, A. Del Fabbro, E. Milotti, Physica A 371 (2006) 463] and we have shown that it can account both for sharp, robust thresholds and for information transfer between processes with widely separated timescales. Here we use the same concepts to expand that analysis starting from a dynamical description of multisite modification: we give analytical results for the basic dynamics and numerical results in an example where the modification chain is cascaded with a Michaelis-Menten step. We modify the dynamics and analyze an example with realistic phosphorylation/dephosphorylation steps, and give numerical evidence of the independence of the allosteric effect from the details of the attachment-detachment processes. We conclude that multisite protein modification is dynamically equivalent to the classic allosteric effect.

  11. Allosteric Inhibition of Macrophage Migration Inhibitory Factor Revealed by Ibudilast

    SciTech Connect

    Cho, Y.; Crichlow, G; Vermeire, J; Leng, L; Du, X; Hodsdon, M; Bucala, R; Cappello, M; Gross, M; et al.

    2010-01-01

    AV411 (ibudilast; 3-isobutyryl-2-isopropylpyrazolo-[1,5-a]pyridine) is an antiinflammatory drug that was initially developed for the treatment of bronchial asthma but which also has been used for cerebrovascular and ocular indications. It is a nonselective inhibitor of various phosphodiesterases (PDEs) and has varied antiinflammatory activity. More recently, AV411 has been studied as a possible therapeutic for the treatment of neuropathic pain and opioid withdrawal through its actions on glial cells. As described herein, the PDE inhibitor AV411 and its PDE-inhibition-compromised analog AV1013 inhibit the catalytic and chemotactic functions of the proinflammatory protein, macrophage migration inhibitory factor (MIF). Enzymatic analysis indicates that these compounds are noncompetitive inhibitors of the p-hydroxyphenylpyruvate (HPP) tautomerase activity of MIF and an allosteric binding site of AV411 and AV1013 is detected by NMR. The allosteric inhibition mechanism is further elucidated by X-ray crystallography based on the MIF/AV1013 binary and MIF/AV1013/HPP ternary complexes. In addition, our antibody experiments directed against MIF receptors indicate that CXCR2 is the major receptor for MIF-mediated chemotaxis of peripheral blood mononuclear cells.

  12. Allosterically controlled threading of polymers through macrocyclic dimers.

    PubMed

    Cantekin, Seda; Markvoort, Albert J; Elemans, Johannes A A W; Rowan, Alan E; Nolte, Roeland J M

    2015-03-25

    As part of an ongoing study to construct a molecular Turing machine in which a polymer chain is encoded via allosteric information transfer between macrocyclic complexes, we describe the thermodynamic and kinetic characterization of a multicomponent self-assembled system based on a zinc porphyrin macrocyclic compound, a bidentate ligand (1,4-diazabicyclo[2.2.2]octane, DABCO), and a viologen-substituted polymer guest. Initial addition of DABCO to the porphyrin macrocycle in chloroform solution leads to the formation of a stable 2:1 (porphyrin:DABCO) dimeric complex, even under dilute conditions, by means of strong cooperative interactions involving hydrogen and metal-ligand bonds. Further titration of the porphyrin-DABCO mixtures with the polymer gives rise to a complex array of species in the solution. The system is analyzed in detail by a combination of spectroscopic measurements and computational modeling. Each association constant in the binding scheme and the fraction of each individual complex that is formed in solution are determined precisely using a mass-balance model. Kinetic studies revealed that the rates of the polymer threading and dethreading in and out of the dimeric system are remarkably slow, indicating that the polymer is locked inside the cavity of the stable 2:1 dimeric complex as a result of strong allosteric interactions. PMID:25734357

  13. A Sphingosine 1-phosphate receptor 2 selective allosteric agonist

    PubMed Central

    Satsu, Hideo; Schaeffer, Marie-Therese; Guerrero, Miguel; Saldana, Adrian; Eberhart, Christina; Hodder, Peter; Cayanan, Charmagne; Schürer, Stephan; Bhhatarai, Barun; Roberts, Ed; Rosen, Hugh; Brown, Steven J.

    2013-01-01

    Molecular probe tool compounds for the Sphingosine 1-phosphate receptor 2 (S1PR2) are important for investigating the multiple biological processes in which the S1PR2 receptor has been implicated. Amongst these are NF-κB-mediated tumor cell survival and fibroblast chemotaxis to fibronectin. Here we report our efforts to identify selective chemical probes for S1PR2 and their characterization. We employed high throughput screening to identify two compounds which activate the S1PR2 receptor. SAR optimization led to compounds with high nanomolar potency. These compounds, XAX-162 and CYM-5520, are highly selective and do not activate other S1P receptors. Binding of CYM-5520 is not competitive with the antagonist JTE-013. Mutation of receptor residues responsible for binding to the zwitterionic headgroup of sphingosine 1-phosphate (S1P) abolishes S1P activation of the receptor, but not activation by CYM-5520. Competitive binding experiments with radiolabeled S1P demonstrate that CYM-5520 is an allosteric agonist and does not displace the native ligand. Computational modeling suggests that CYM-5520 binds lower in the orthosteric binding pocket, and that co-binding with S1P is energetically well tolerated. In summary, we have identified an allosteric S1PR2 selective agonist compound. PMID:23849205

  14. The allosteric switching mechanism in bacteriophage MS2

    NASA Astrophysics Data System (ADS)

    Perkett, Matthew R.; Mirijanian, Dina T.; Hagan, Michael F.

    2016-07-01

    We use all-atom simulations to elucidate the mechanisms underlying conformational switching and allostery within the coat protein of the bacteriophage MS2. Assembly of most icosahedral virus capsids requires that the capsid protein adopts different conformations at precise locations within the capsid. It has been shown that a 19 nucleotide stem loop (TR) from the MS2 genome acts as an allosteric effector, guiding conformational switching of the coat protein during capsid assembly. Since the principal conformational changes occur far from the TR binding site, it is important to understand the molecular mechanism underlying this allosteric communication. To this end, we use all-atom simulations with explicit water combined with a path sampling technique to sample the MS2 coat protein conformational transition, in the presence and absence of TR-binding. The calculations find that TR binding strongly alters the transition free energy profile, leading to a switch in the favored conformation. We discuss changes in molecular interactions responsible for this shift. We then identify networks of amino acids with correlated motions to reveal the mechanism by which effects of TR binding span the protein. We find that TR binding strongly affects residues located at the 5-fold and quasi-sixfold interfaces in the assembled capsid, suggesting a mechanism by which the TR binding could direct formation of the native capsid geometry. The analysis predicts amino acids whose substitution by mutagenesis could alter populations of the conformational substates or their transition rates.

  15. Broad-Spectrum Allosteric Inhibition of Herpesvirus Proteases

    PubMed Central

    2015-01-01

    Herpesviruses rely on a homodimeric protease for viral capsid maturation. A small molecule, DD2, previously shown to disrupt dimerization of Kaposi’s sarcoma-associated herpesvirus protease (KSHV Pr) by trapping an inactive monomeric conformation and two analogues generated through carboxylate bioisosteric replacement (compounds 2 and 3) were shown to inhibit the associated proteases of all three human herpesvirus (HHV) subfamilies (α, β, and γ). Inhibition data reveal that compound 2 has potency comparable to or better than that of DD2 against the tested proteases. Nuclear magnetic resonance spectroscopy and a new application of the kinetic analysis developed by Zhang and Poorman [Zhang, Z. Y., Poorman, R. A., et al. (1991) J. Biol. Chem. 266, 15591–15594] show DD2, compound 2, and compound 3 inhibit HHV proteases by dimer disruption. All three compounds bind the dimer interface of other HHV proteases in a manner analogous to binding of DD2 to KSHV protease. The determination and analysis of cocrystal structures of both analogues with the KSHV Pr monomer verify and elaborate on the mode of binding for this chemical scaffold, explaining a newly observed critical structure–activity relationship. These results reveal a prototypical chemical scaffold for broad-spectrum allosteric inhibition of human herpesvirus proteases and an approach for the identification of small molecules that allosterically regulate protein activity by targeting protein–protein interactions. PMID:24977643

  16. An allosteric photoredox catalyst inspired by photosynthetic machinery

    PubMed Central

    Lifschitz, Alejo M.; Young, Ryan M.; Mendez-Arroyo, Jose; Stern, Charlotte L.; McGuirk, C. Michael; Wasielewski, Michael R.; Mirkin, Chad A.

    2015-01-01

    Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switching using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Thus, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices. PMID:25817586

  17. Study of Functional and Allosteric Sites in Protein Superfamilies

    PubMed Central

    Suplatov, D.; Švedas, V.

    2015-01-01

    The interaction of proteins (enzymes) with a variety of low-molecular-weight compounds, as well as protein-protein interactions, is the most important factor in the regulation of their functional properties. To date, research effort has routinely focused on studying ligand binding to the functional sites of proteins (active sites of enzymes), whereas the molecular mechanisms of allosteric regulation, as well as binding to other pockets and cavities in protein structures, remained poorly understood. Recent studies have shown that allostery may be an intrinsic property of virtually all proteins. Novel approaches are needed to systematically analyze the architecture and role of various binding sites and establish the relationship between structure, function, and regulation. Computational biology, bioinformatics, and molecular modeling can be used to search for new regulatory centers, characterize their structural peculiarities, as well as compare different pockets in homologous proteins, study the molecular mechanisms of allostery, and understand the communication between topologically independent binding sites in protein structures. The establishment of an evolutionary relationship between different binding centers within protein superfamilies and the discovery of new functional and allosteric (regulatory) sites using computational approaches can improve our understanding of the structure-function relationship in proteins and provide new opportunities for drug design and enzyme engineering. PMID:26798490

  18. Allosteric activation of ADAMTS13 by von Willebrand factor

    PubMed Central

    Muia, Joshua; Zhu, Jian; Gupta, Garima; Haberichter, Sandra L.; Friedman, Kenneth D.; Feys, Hendrik B.; Deforche, Louis; Vanhoorelbeke, Karen; Westfield, Lisa A.; Roth, Robyn; Tolia, Niraj Harish; Heuser, John E.

    2014-01-01

    The metalloprotease ADAMTS13 cleaves von Willebrand factor (VWF) within endovascular platelet aggregates, and ADAMTS13 deficiency causes fatal microvascular thrombosis. The proximal metalloprotease (M), disintegrin-like (D), thrombospondin-1 (T), Cys-rich (C), and spacer (S) domains of ADAMTS13 recognize a cryptic site in VWF that is exposed by tensile force. Another seven T and two complement C1r/C1s, sea urchin epidermal growth factor, and bone morphogenetic protein (CUB) domains of uncertain function are C-terminal to the MDTCS domains. We find that the distal T8-CUB2 domains markedly inhibit substrate cleavage, and binding of VWF or monoclonal antibodies to distal ADAMTS13 domains relieves this autoinhibition. Small angle X-ray scattering data indicate that distal T-CUB domains interact with proximal MDTCS domains. Thus, ADAMTS13 is regulated by substrate-induced allosteric activation, which may optimize VWF cleavage under fluid shear stress in vivo. Distal domains of other ADAMTS proteases may have similar allosteric properties. PMID:25512528

  19. Evidence for allosteric regulation of succinyl-CoA synthetase.

    PubMed Central

    Um, H D; Klein, C

    1993-01-01

    We have previously reported that distinctly different concentrations of GDP stimulate the phosphorylation and dephosphorylation of p36, the alpha-subunit of succinyl-CoA synthetase (SCS) in Dictyostelium discoideum. In this present study, we have investigated the mechanism underlying these dual effects of GDP. Dephosphorylation of p36 is induced by relatively high levels of GDP and is coincident with the formation of GTP. This indicates that, at high concentrations, GDP serves as a substrate of SCS. However, 100-fold lower concentrations of GDP, which do not bind to the catalytic site to induce SCS dephosphorylation, stimulate p36 phosphorylation. This stimulation is not diminished by dilution of the sample, and is retained during purification of the protein. Gel-filtration analyses indicate that SCS in our system behaves as a non-interacting alpha beta dimer, the hydrodynamic behaviour of which is not altered by the presence of added GDP. The data indicate that altered protein-protein interactions do not account for the stimulation of p36 phosphorylation by low GDP concentrations. We propose that GDP functions as an allosteric regulator of SCS, and experiments using guanosine 5'-[beta-thio]diphosphate (GDP[S]) are shown to distinguish further the allosteric and catalytic binding sites. Images Figure 1 Figure 2 Figure 3 Figure 5 PMID:8240297

  20. Evidence for allosteric regulation of succinyl-CoA synthetase.

    PubMed

    Um, H D; Klein, C

    1993-11-01

    We have previously reported that distinctly different concentrations of GDP stimulate the phosphorylation and dephosphorylation of p36, the alpha-subunit of succinyl-CoA synthetase (SCS) in Dictyostelium discoideum. In this present study, we have investigated the mechanism underlying these dual effects of GDP. Dephosphorylation of p36 is induced by relatively high levels of GDP and is coincident with the formation of GTP. This indicates that, at high concentrations, GDP serves as a substrate of SCS. However, 100-fold lower concentrations of GDP, which do not bind to the catalytic site to induce SCS dephosphorylation, stimulate p36 phosphorylation. This stimulation is not diminished by dilution of the sample, and is retained during purification of the protein. Gel-filtration analyses indicate that SCS in our system behaves as a non-interacting alpha beta dimer, the hydrodynamic behaviour of which is not altered by the presence of added GDP. The data indicate that altered protein-protein interactions do not account for the stimulation of p36 phosphorylation by low GDP concentrations. We propose that GDP functions as an allosteric regulator of SCS, and experiments using guanosine 5'-[beta-thio]diphosphate (GDP[S]) are shown to distinguish further the allosteric and catalytic binding sites. PMID:8240297

  1. Allosteric Ligand Binding and Anisotropic Energy Flow in Albumin

    NASA Astrophysics Data System (ADS)

    Dyer, Brian

    2014-03-01

    Protein allostery usually involves propagation of local structural changes through the protein to a remote site. Coupling of structural changes at remote sites is thought to occur through anisotropic energy transport, but the nature of this process is poorly understood. We have studied the relationship between allosteric interactions of remote ligand binding sites of the protein and energy flow through the structure of bovine serum albumin (BSA). We applied ultrafast infrared spectroscopy to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic flow through the protein structure following input of thermal energy into the flexible ligand binding sites. We also observe anisotropic heat flow through the structure, without local heating of the rigid helix bundles that connect these sites. We will discuss the implications of this efficient energy transport mechanism with regard to the allosteric propagation of binding energy through the connecting helix structures.

  2. Structural Analysis of Iac Repressor Bound to Allosteric Effectors

    SciTech Connect

    Daber,R.; Stayrook, S.; Rosenberg, A.; Lewis, M.

    2007-01-01

    The lac operon is a model system for understanding how effector molecules regulate transcription and are necessary for allosteric transitions. The crystal structures of the lac repressor bound to inducer and anti-inducer molecules provide a model for how these small molecules can modulate repressor function. The structures of the apo repressor and the repressor bound to effector molecules are compared in atomic detail. All effectors examined here bind to the repressor in the same location and are anchored to the repressor through hydrogen bonds to several hydroxyl groups of the sugar ring. Inducer molecules form a more extensive hydrogen-bonding network compared to anti-inducers and neutral effector molecules. The structures of these effector molecules suggest that the O6 hydroxyl on the galactoside is essential for establishing a water-mediated hydrogen bonding network that bridges the N-terminal and C-terminal sub-domains. The altered hydrogen bonding can account in part for the different structural conformations of the repressor, and is vital for the allosteric transition.

  3. Allosteric communication between DNA-binding and light-responsive domains of diatom class I aureochromes

    PubMed Central

    Banerjee, Ankan; Herman, Elena; Serif, Manuel; Maestre-Reyna, Manuel; Hepp, Sebastian; Pokorny, Richard; Kroth, Peter G.; Essen, Lars-Oliver; Kottke, Tilman

    2016-01-01

    The modular architecture of aureochrome blue light receptors, found in several algal groups including diatoms, is unique by having the LOV-type photoreceptor domain fused to the C-terminus of its putative effector, an N-terminal DNA-binding bZIP module. The structural and functional understanding of aureochromes’ light-dependent signaling mechanism is limited, despite their promise as an optogenetic tool. We show that class I aureochromes 1a and 1c from the diatom Phaeodactylum tricornutum are regulated in a light-independent circadian rhythm. These aureochromes are capable to form functional homo- and heterodimers, which recognize the ACGT core sequence within the canonical ‘aureo box’, TGACGT, in a light-independent manner. The bZIP domain holds a more folded and less flexible but extended conformation in the duplex DNA-bound state. FT-IR spectroscopy in the absence and the presence of DNA shows light-dependent helix unfolding in the LOV domain, which leads to conformational changes in the bZIP region. The solution structure of DNA bound to aureochrome points to a tilted orientation that was further validated by molecular dynamics simulations. We propose that aureochrome signaling relies on an allosteric pathway from LOV to bZIP that results in conformational changes near the bZIP-DNA interface without major effects on the binding affinity. PMID:27179025

  4. Allosteric N-WASP activation by an inter-SH3 domain linker in Nck

    PubMed Central

    Okrut, Julia; Prakash, Sumit; Wu, Qiong; Kelly, Mark J. S.; Taunton, Jack

    2015-01-01

    Actin filament networks assemble on cellular membranes in response to signals that locally activate neural Wiskott–Aldrich-syndrome protein (N-WASP) and the Arp2/3 complex. An inactive conformation of N-WASP is stabilized by intramolecular contacts between the GTPase binding domain (GBD) and the C helix of the verprolin-homology, connector-helix, acidic motif (VCA) segment. Multiple SH3 domain-containing adapter proteins can bind and possibly activate N-WASP, but it remains unclear how such binding events relieve autoinhibition to unmask the VCA segment and activate the Arp2/3 complex. Here, we have used purified components to reconstitute a signaling cascade driven by membrane-localized Src homology 3 (SH3) adapters and N-WASP, resulting in the assembly of dynamic actin networks. Among six SH3 adapters tested, Nck was the most potent activator of N-WASP–driven actin assembly. We identify within Nck a previously unrecognized activation motif in a linker between the first two SH3 domains. This linker sequence, reminiscent of bacterial virulence factors, directly engages the N-WASP GBD and competes with VCA binding. Our results suggest that animals, like pathogenic bacteria, have evolved peptide motifs that allosterically activate N-WASP, leading to localized actin nucleation on cellular membranes. PMID:26554011

  5. Allosteric communication between DNA-binding and light-responsive domains of diatom class I aureochromes.

    PubMed

    Banerjee, Ankan; Herman, Elena; Serif, Manuel; Maestre-Reyna, Manuel; Hepp, Sebastian; Pokorny, Richard; Kroth, Peter G; Essen, Lars-Oliver; Kottke, Tilman

    2016-07-01

    The modular architecture of aureochrome blue light receptors, found in several algal groups including diatoms, is unique by having the LOV-type photoreceptor domain fused to the C-terminus of its putative effector, an N-terminal DNA-binding bZIP module. The structural and functional understanding of aureochromes' light-dependent signaling mechanism is limited, despite their promise as an optogenetic tool. We show that class I aureochromes 1a and 1c from the diatom Phaeodactylum tricornutum are regulated in a light-independent circadian rhythm. These aureochromes are capable to form functional homo- and heterodimers, which recognize the ACGT core sequence within the canonical 'aureo box', TGACGT, in a light-independent manner. The bZIP domain holds a more folded and less flexible but extended conformation in the duplex DNA-bound state. FT-IR spectroscopy in the absence and the presence of DNA shows light-dependent helix unfolding in the LOV domain, which leads to conformational changes in the bZIP region. The solution structure of DNA bound to aureochrome points to a tilted orientation that was further validated by molecular dynamics simulations. We propose that aureochrome signaling relies on an allosteric pathway from LOV to bZIP that results in conformational changes near the bZIP-DNA interface without major effects on the binding affinity. PMID:27179025

  6. Targeting the disordered C-terminus of PTP1B with an allosteric inhibitor

    PubMed Central

    Krishnan, Navasona; Koveal, Dorothy; Miller, Daniel H.; Xue, Bin; Akshinthala, Sai Dipikaa; Kragelj, Jaka; Jensen, Malene Ringkjøbing; Gauss, Carla-Maria; Page, Rebecca; Blackledge, Martin; Muthuswamy, Senthil K.; Peti, Wolfgang; Tonks, Nicholas K.

    2014-01-01

    PTP1B, a validated therapeutic target for diabetes and obesity, plays a critical positive role in HER2 signaling in breast tumorigenesis. Efforts to develop therapeutic inhibitors of PTP1B have been frustrated by the chemical properties of the active site. We defined a novel mechanism of allosteric inhibition that targets the C-terminal, non-catalytic segment of PTP1B. We present the first ensemble structure of PTP1B containing this intrinsically disordered segment, within which we identified a binding site for the small molecule inhibitor, MSI-1436. We demonstrate binding to a second site close to the catalytic domain, with cooperative effects between the two sites locking PTP1B in an inactive state. MSI-1436 antagonized HER2 signaling, inhibited tumorigenesis in xenografts and abrogated metastasis in the NDL2 mouse model of breast cancer, validating inhibition of PTP1B as a therapeutic strategy in breast cancer. This new approach to inhibition of PTP1B emphasizes the potential of disordered segments of proteins as specific binding sites for therapeutic small molecules. PMID:24845231

  7. The kinetics of effector binding to phosphofructokinase. The allosteric conformational transition induced by 1,N6-ethenoadenosine triphosphate.

    PubMed Central

    Roberts, D; Kellett, G L

    1979-01-01

    1. The fluorescent ATP analogue 1,N6-etheno-ATP is a good substrate and an efficient allosteric inhibitor of rabbit skeletal-muscle phosphofructokinase. 2. Fluorescence energy transfer occurs between bound 1,N6-etheno-ATP and phosphofructokinase. 1,N6-Etheno-ATP fluorescence is enhanced, intrinsic protein fluorescence is quenched, and the excitation spectrum of 1,N6-etheno-ATP fluorescence is characteristic of protein absorption. 3. The binding reaction of 1,N6-etheno-ATP observed by stopped-flow fluorimetry is biphasic. The fast phase results from binding to the catalytic site alone. The slow phase results from the allosteric transition of the R conformation into the T conformation induced by the binding of 1,N6-etheno-ATP to the regulatory site. 4. The fluorescence signal that allows the transition of the R conformation into the T conformation to be observed does not arise from 1,N6-etheno-ATP bound to the regulatory site. It arises instead from 1,N6-etheno-ATP bound to the catalytic site as a consequence of changes at the catalytic site caused by the transition of the R conformation into the T conformation. 5. In the presence of excess of Mg2+, the affinity of 1,N6-etheno-ATP for the regulatory site is very much greater in the T state than in the R state. Images Fig. 5. Fig. 8. PMID:160791

  8. Structural insights into Ca(2+)-activated long-range allosteric channel gating of RyR1.

    PubMed

    Wei, Risheng; Wang, Xue; Zhang, Yan; Mukherjee, Saptarshi; Zhang, Lei; Chen, Qiang; Huang, Xinrui; Jing, Shan; Liu, Congcong; Li, Shuang; Wang, Guangyu; Xu, Yaofang; Zhu, Sujie; Williams, Alan J; Sun, Fei; Yin, Chang-Cheng

    2016-09-01

    Ryanodine receptors (RyRs) are a class of giant ion channels with molecular mass over 2.2 mega-Daltons. These channels mediate calcium signaling in a variety of cells. Since more than 80% of the RyR protein is folded into the cytoplasmic assembly and the remaining residues form the transmembrane domain, it has been hypothesized that the activation and regulation of RyR channels occur through an as yet uncharacterized long-range allosteric mechanism. Here we report the characterization of a Ca(2+)-activated open-state RyR1 structure by cryo-electron microscopy. The structure has an overall resolution of 4.9 Å and a resolution of 4.2 Å for the core region. In comparison with the previously determined apo/closed-state structure, we observed long-range allosteric gating of the channel upon Ca(2+) activation. In-depth structural analyses elucidated a novel channel-gating mechanism and a novel ion selectivity mechanism of RyR1. Our work not only provides structural insights into the molecular mechanisms of channel gating and regulation of RyRs, but also sheds light on structural basis for channel-gating and ion selectivity mechanisms for the six-transmembrane-helix cation channel family. PMID:27573175

  9. Allosteric Regulation of Transport Activity by Heterotrimerization of Arabidopsis Ammonium Transporter Complexes in Vivo[C][W][OA

    PubMed Central

    Yuan, Lixing; Gu, Riliang; Xuan, Yuanhu; Smith-Valle, Erika; Loqué, Dominique; Frommer, Wolf B.; von Wirén, Nicolaus

    2013-01-01

    Ammonium acquisition by plant roots is mediated by AMMONIUM TRANSPORTERs (AMTs), ubiquitous membrane proteins with essential roles in nitrogen nutrition in all organisms. In microbial and plant cells, ammonium transport activity is controlled by ammonium-triggered feedback inhibition to prevent cellular ammonium toxicity. Data from heterologous expression in yeast indicate that oligomerization of plant AMTs is critical for allosteric regulation of transport activity, in which the conserved cytosolic C terminus functions as a trans-activator. Employing the coexpressed transporters AMT1;1 and AMT1;3 from Arabidopsis thaliana as a model, we show here that these two isoforms form functional homo- and heterotrimers in yeast and plant roots and that AMT1;3 carrying a phosphomimic residue in its C terminus regulates both homo- and heterotrimers in a dominant-negative fashion in vivo. 15NH4+ influx studies further indicate that allosteric inhibition represses ammonium transport activity in roots of transgenic Arabidopsis expressing a phosphomimic mutant together with functional AMT1;3 or AMT1;1. Our study demonstrates in planta a regulatory role in transport activity of heterooligomerization of transporter isoforms, which may enhance their versatility for signal exchange in response to environmental triggers. PMID:23463773

  10. The M1 Muscarinic Positive Allosteric Modulator PQCA Improves Performance on Translatable Tests of Memory and Attention in Rhesus Monkeys.

    PubMed

    Lange, Henry S; Cannon, Christopher E; Drott, Jason T; Kuduk, Scott D; Uslaner, Jason M

    2015-12-01

    Improved treatment of Alzheimer disease (AD) is a significant unmet medical need that is becoming even more critical given the rise in the number of patients and the substantial economic burden. The current standards of care, acetylcholinesterase inhibitors (AChEIs), are hindered by gastrointestinal side effects owing to their nonselective activation of muscarinic and nicotinic receptors. Recently, the highly selective M1 positive allosteric modulator PQCA (1-((4-cyano-4-(pyridine-2-yl)piperidin-1-yl)methyl-4-oxo-4 H-quinolizine-3-carboxylic acid) has been demonstrated to improve cognition in a variety of rodent and nonhuman primate cognition models without producing significant gastrointestinal side effects. Here we describe the effect of PQCA and the AChEI donepezil on two clinically relevant and highly translatable touchscreen cognition tasks in nonhuman primates: paired-associates learning (PAL) and the continuous-performance task (CPT). Blockade of muscarinic signaling by scopolamine produced significant impairments in both PAL and CPT. PQCA and donepezil attenuated the scopolamine deficits in both tasks, and the action of these two compounds was similar in magnitude. In addition, the combination of subeffective doses of PQCA and donepezil enhanced PAL performance. These results further suggest that M1-positive allosteric modulators, either as monotherapy or as an add-on to current standards of care, have potential to reduce the cognitive deficits associated with AD. PMID:26446308

  11. Allosteric modulation in monomers and oligomers of a G protein-coupled receptor

    PubMed Central

    Shivnaraine, Rabindra V; Kelly, Brendan; Sankar, Krishana S; Redka, Dar'ya S; Han, Yi Rang; Huang, Fei; Elmslie, Gwendolynne; Pinto, Daniel; Li, Yuchong; Rocheleau, Jonathan V; Gradinaru, Claudiu C; Ellis, John; Wells, James W

    2016-01-01

    The M2 muscarinic receptor is the prototypic model of allostery in GPCRs, yet the molecular and the supramolecular determinants of such effects are unknown. Monomers and oligomers of the M2 muscarinic receptor therefore have been compared to identify those allosteric properties that are gained in oligomers. Allosteric interactions were monitored by means of a FRET-based sensor of conformation at the allosteric site and in pharmacological assays involving mutants engineered to preclude intramolecular effects. Electrostatic, steric, and conformational determinants of allostery at the atomic level were examined in molecular dynamics simulations. Allosteric effects in monomers were exclusively negative and derived primarily from intramolecular electrostatic repulsion between the allosteric and orthosteric ligands. Allosteric effects in oligomers could be positive or negative, depending upon the allosteric-orthosteric pair, and they arose from interactions within and between the constituent protomers. The complex behavior of oligomers is characteristic of muscarinic receptors in myocardial preparations. DOI: http://dx.doi.org/10.7554/eLife.11685.001 PMID:27151542

  12. Allosteric Modulation of Metabotropic Glutamate Receptors: Structural Insights and Therapeutic Potential

    PubMed Central

    Gregory, Karen J.; Dong, Elizabeth N.; Meiler, Jens; Conn, P. Jeffrey

    2010-01-01

    Allosteric modulation of G protein-coupled receptors (GPCRs) represents a novel approach to the development of probes and therapeutics that is expected to enable subtype-specific regulation of central nervous system target receptors. The metabotropic glutamate receptors (mGlus) are class C GPCRs that play important neuromodulatory roles throughout the brain, as such they are attractive targets for therapeutic intervention for a number of psychiatric and neurological disorders including anxiety, depression, Fragile X Syndrome, Parkinson’s disease and schizophrenia. Over the last fifteen years, selective allosteric modulators have been identified for many members of the mGlu family. The vast majority of these allosteric modulators are thought to bind within the transmembrane-spanning domains of the receptors to enhance or inhibit functional responses. A combination of mutagenesis-based studies and pharmacological approaches are beginning to provide a better understanding of mGlu allosteric sites. Collectively, when mapped onto a homology model of the different mGlu subtypes based on the β2-adrenergic receptor, the previous mutagenesis studies suggest commonalities in the location of allosteric sites across different members of the mGlu family. In addition, there is evidence for multiple allosteric binding pockets within the transmembrane region that can interact to modulate one another. In the absence of a class C GPCR crystal structure, this approach has shown promise with respect to the interpretation of mutagenesis data and understanding structure-activity relationships of allosteric modulator pharmacophores. PMID:20637216

  13. Positive Allosteric Modulation of the Glucagon-like Peptide-1 Receptor by Diverse Electrophiles.

    PubMed

    Bueno, Ana B; Showalter, Aaron D; Wainscott, David B; Stutsman, Cynthia; Marín, Aranzazu; Ficorilli, James; Cabrera, Over; Willard, Francis S; Sloop, Kyle W

    2016-05-13

    Therapeutic intervention to activate the glucagon-like peptide-1 receptor (GLP-1R) enhances glucose-dependent insulin secretion and improves energy balance in patients with type 2 diabetes mellitus. Studies investigating mechanisms whereby peptide ligands activate GLP-1R have utilized mutagenesis, receptor chimeras, photo-affinity labeling, hydrogen-deuterium exchange, and crystallography of the ligand-binding ectodomain to establish receptor homology models. However, this has not enabled the design or discovery of drug-like non-peptide GLP-1R activators. Recently, studies investigating 4-(3-benzyloxyphenyl)-2-ethylsulfinyl-6-(trifluoromethyl)pyrimidine (BETP), a GLP-1R-positive allosteric modulator, determined that Cys-347 in the GLP-1R is required for positive allosteric modulator activity via covalent modification. To advance small molecule activation of the GLP-1R, we characterized the insulinotropic mechanism of BETP. In guanosine 5'-3-O-(thio)triphosphate binding and INS1 832-3 insulinoma cell cAMP assays, BETP enhanced GLP-1(9-36)-NH2-stimulated cAMP signaling. Using isolated pancreatic islets, BETP potentiated insulin secretion in a glucose-dependent manner that requires both the peptide ligand and GLP-1R. In studies of the covalent mechanism, PAGE fluorography showed labeling of GLP-1R in immunoprecipitation experiments from GLP-1R-expressing cells incubated with [(3)H]BETP. Furthermore, we investigated whether other reported GLP-1R activators and compounds identified from screening campaigns modulate GLP-1R by covalent modification. Similar to BETP, several molecules were found to enhance GLP-1R signaling in a Cys-347-dependent manner. These chemotypes are electrophiles that react with GSH, and LC/MS determined the cysteine adducts formed upon conjugation. Together, our results suggest covalent modification may be used to stabilize the GLP-1R in an active conformation. Moreover, the findings provide pharmacological guidance for the discovery and

  14. Positive Allosteric Modulation of the Glucagon-like Peptide-1 Receptor by Diverse Electrophiles*

    PubMed Central

    Showalter, Aaron D.; Wainscott, David B.; Stutsman, Cynthia; Marín, Aranzazu; Ficorilli, James; Cabrera, Over

    2016-01-01

    Therapeutic intervention to activate the glucagon-like peptide-1 receptor (GLP-1R) enhances glucose-dependent insulin secretion and improves energy balance in patients with type 2 diabetes mellitus. Studies investigating mechanisms whereby peptide ligands activate GLP-1R have utilized mutagenesis, receptor chimeras, photo-affinity labeling, hydrogen-deuterium exchange, and crystallography of the ligand-binding ectodomain to establish receptor homology models. However, this has not enabled the design or discovery of drug-like non-peptide GLP-1R activators. Recently, studies investigating 4-(3-benzyloxyphenyl)-2-ethylsulfinyl-6-(trifluoromethyl)pyrimidine (BETP), a GLP-1R-positive allosteric modulator, determined that Cys-347 in the GLP-1R is required for positive allosteric modulator activity via covalent modification. To advance small molecule activation of the GLP-1R, we characterized the insulinotropic mechanism of BETP. In guanosine 5′-3-O-(thio)triphosphate binding and INS1 832-3 insulinoma cell cAMP assays, BETP enhanced GLP-1(9–36)-NH2-stimulated cAMP signaling. Using isolated pancreatic islets, BETP potentiated insulin secretion in a glucose-dependent manner that requires both the peptide ligand and GLP-1R. In studies of the covalent mechanism, PAGE fluorography showed labeling of GLP-1R in immunoprecipitation experiments from GLP-1R-expressing cells incubated with [3H]BETP. Furthermore, we investigated whether other reported GLP-1R activators and compounds identified from screening campaigns modulate GLP-1R by covalent modification. Similar to BETP, several molecules were found to enhance GLP-1R signaling in a Cys-347-dependent manner. These chemotypes are electrophiles that react with GSH, and LC/MS determined the cysteine adducts formed upon conjugation. Together, our results suggest covalent modification may be used to stabilize the GLP-1R in an active conformation. Moreover, the findings provide pharmacological guidance for the discovery and

  15. Record-high and robust 17.125 Gb/s gross-rate over 25 km SSMF transmissions of real-time dual-band optical OFDM signals directly modulated by 1 GHz RSOAs.

    PubMed

    Zhang, Q W; Hugues-Salas, E; Ling, Y; Zhang, H B; Giddings, R P; Zhang, J J; Wang, M; Tang, J M

    2014-03-24

    Aggregated 17.125 Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) transmissions over 25 km SSMF IMDD systems with 7 dB receiver sensitivity improvements are experimentally demonstrated, for the first time, by utilizing low-cost transceiver components such as directly modulated 1GHz RSOAs and DACs/ADCs operating at sampling speeds as low as 4GS/s. The demonstrated OOFDM transceivers have both strong adaptability and sufficiently large passband carrier frequency tunability, which enable full use of highly dynamic spectral characteristics of the transmission systems. This results in the achievements of not only excellent performance robustness to variations in system operating conditions but also significantly relaxed requirements on RSOA small-signal modulation bandwidth. It is shown that the aforementioned transmission capacity only varies by <23% over a RSOA-injected optical power variation range as large as 20dB, and that the 1 GHz RSOAs can support successful transmissions of adaptively modulated OOFDM signals having bandwidths of 8.5 GHz. By taking into account the adopted 25% cyclic prefix and a typical 7.3% FEC overhead, the demonstrated real-time OOFDM transmission systems are capable of conveying 11.6 Gb/s user data. PMID:24663982

  16. Structural Mechanisms of Peptide Recognition and Allosteric Modulation of Gene Regulation by the RRNPP Family of Quorum-Sensing Regulators.

    PubMed

    Do, Hackwon; Kumaraswami, Muthiah

    2016-07-17

    The members of RRNPP family of bacterial regulators sense population density-specific secreted oligopeptides and modulate the expression of genes involved in cellular processes, such as sporulation, competence, virulence, biofilm formation, conjugative plasmid transfer and antibiotic resistance. Signaling by RRNPP regulators include several steps: generation and secretion of the signaling oligopeptides, re-internalization of the signaling molecules into the cytoplasm, signal sensing by the cytosolic RRNPP regulators, signal-specific allosteric structural changes in the regulators, and interaction of the regulators with their respective regulatory target and gene regulation. The recently determined structures of the RRNPP regulators provide insight into the mechanistic aspects for several steps in this signaling circuit. In this review, we discuss the structural principles underlying peptide specificity, regulatory target recognition, and ligand-induced allostery in RRNPP regulators and its impact on gene regulation. Despite the conserved tertiary structure of these regulators, structural analyses revealed unexpected diversity in the mechanism of activation and molecular strategies that couple the peptide-induced allostery to gene regulation. Although these structural studies provide a sophisticated understanding of gene regulation by RRNPP regulators, much needs to be learned regarding the target DNA binding by yet-to-be characterized RNPP regulators and the several aspects of signaling by Rgg regulators. PMID:27283781

  17. Interactions of orthosteric and allosteric ligands with [3H]dimethyl-W84 at the common allosteric site of muscarinic M2 receptors.

    PubMed

    Tränkle, Christian; Weyand, Oliver; Voigtländer, Uta; Mynett, Anita; Lazareno, Sebastian; Birdsall, Nigel J M; Mohr, Klaus

    2003-07-01

    An optimized assay for the binding of [3H]dimethyl-W84 to its allosteric site on M2 muscarinic receptors has been used to directly measure the affinities of allosteric ligands. Their potencies agree with those deduced indirectly by their modulation of the equilibrium binding and kinetics of [3H]N-methylscopolamine ([3H]NMS) binding to the orthosteric site. The affinities and cooperativities of orthosteric antagonists with [3H]dimethyl-W84 have also been quantitated. These affinities agree with those measured directly in a competition assay using [3H]NMS. All these data are compatible with the predictions of the allosteric ternary complex model. The association and dissociation kinetics of [3H]dimethyl-W84 are rapid but the estimate of its association rate constant is nevertheless comparable with that found for the orthosteric radioligand, [3H]NMS. This is unexpected, given that the allosteric site to which [3H]dimethyl-W84 binds is thought to be located on the external face of the receptor and above the [3H]NMS binding site that is buried within the transmembrane helices. The atypical allosteric ligands tacrine and 4,4'-bis-[(2,6-dichloro-benzyloxy-imino)-methyl]-1,1'-propane-1,3-diyl-bis-pyridinium dibromide (Duo3) inhibit [3H]dimethyl-W84 binding with the same potencies and comparably steep slope factors as found for inhibition of [3H]NMS binding. Tacrine and Duo3 decrease [3H]dimethyl-W84 affinity, not the number of binding sites. It is suggested that these atypical ligands either bind to the two known spatially separated allosteric sites on muscarinic receptors with positive cooperativity or their binding to the common allosteric site modulates receptor-receptor interactions such that homotropic positive cooperativity within a dimer or higher oligomer is generated. PMID:12815174

  18. Engineering an allosteric transcription factor to respond to new ligands

    PubMed Central

    Taylor, Noah D; Garruss, Alexander S; Moretti, Rocco; Chan, Sum; Arbing, Mark A; Cascio, Duilio; Rogers, Jameson K; Isaacs, Farren J; Kosuri, Sriram; Baker, David; Fields, Stanley; Church, George M; Raman, Srivatsan

    2016-01-01

    Genetic regulatory proteins inducible by small molecules are useful synthetic biology tools as sensors and switches. Bacterial allosteric transcription factors (aTFs) are a major class of regulatory proteins, but few aTFs have been redesigned to respond to new effectors beyond natural aTF-inducer pairs. Altering inducer specificity in these proteins is difficult because substitutions that affect inducer binding may also disrupt allostery. We engineered an aTF, the Escherichia coli lac repressor, LacI, to respond to one of four new inducer molecules: fucose, gentiobiose, lactitol or sucralose. Using computational protein design, single-residue saturation mutagenesis or random mutagenesis, along with multiplex assembly, we identified new variants comparable in specificity and induction to wild-type LacI with its inducer, isopropyl β-D-1-thiogalactopyranoside (IPTG). The ability to create designer aTFs will enable applications including dynamic control of cell metabolism, cell biology and synthetic gene circuits. PMID:26689263

  19. Engineering an allosteric transcription factor to respond to new ligands.

    PubMed

    Taylor, Noah D; Garruss, Alexander S; Moretti, Rocco; Chan, Sum; Arbing, Mark A; Cascio, Duilio; Rogers, Jameson K; Isaacs, Farren J; Kosuri, Sriram; Baker, David; Fields, Stanley; Church, George M; Raman, Srivatsan

    2016-02-01

    Genetic regulatory proteins inducible by small molecules are useful synthetic biology tools as sensors and switches. Bacterial allosteric transcription factors (aTFs) are a major class of regulatory proteins, but few aTFs have been redesigned to respond to new effectors beyond natural aTF-inducer pairs. Altering inducer specificity in these proteins is difficult because substitutions that affect inducer binding may also disrupt allostery. We engineered an aTF, the Escherichia coli lac repressor, LacI, to respond to one of four new inducer molecules: fucose, gentiobiose, lactitol and sucralose. Using computational protein design, single-residue saturation mutagenesis or random mutagenesis, along with multiplex assembly, we identified new variants comparable in specificity and induction to wild-type LacI with its inducer, isopropyl β-D-1-thiogalactopyranoside (IPTG). The ability to create designer aTFs will enable applications including dynamic control of cell metabolism, cell biology and synthetic gene circuits. PMID:26689263

  20. Structural Basis for Allosteric Regulation of GPCRs by Sodium Ions

    SciTech Connect

    Liu, Wei; Chun, Eugene; Thompson, Aaron A.; Chubukov, Pavel; Xu, Fei; Katritch, Vsevolod; Han, Gye Won; Roth, Christopher B.; Heitman, Laura H.; IJzerman, Adriaan P.; Cherezov, Vadim; Stevens, Raymond C.

    2012-08-31

    Pharmacological responses of G protein-coupled receptors (GPCRs) can be fine-tuned by allosteric modulators. Structural studies of such effects have been limited due to the medium resolution of GPCR structures. We reengineered the human A{sub 2A} adenosine receptor by replacing its third intracellular loop with apocytochrome b{sub 562}RIL and solved the structure at 1.8 angstrom resolution. The high-resolution structure allowed us to identify 57 ordered water molecules inside the receptor comprising three major clusters. The central cluster harbors a putative sodium ion bound to the highly conserved aspartate residue Asp{sup 2.50}. Additionally, two cholesterols stabilize the conformation of helix VI, and one of 23 ordered lipids intercalates inside the ligand-binding pocket. These high-resolution details shed light on the potential role of structured water molecules, sodium ions, and lipids/cholesterol in GPCR stabilization and function.

  1. Thrombin A-Chain: Activation Remnant or Allosteric Effector?

    PubMed Central

    Carter, Isis S. R.; Vanden Hoek, Amanda L.; Pryzdial, Edward L. G.; MacGillivray, Ross T. A.

    2010-01-01

    Although prothrombin is one of the most widely studied enzymes in biology, the role of the thrombin A-chain has been neglected in comparison to the other domains. This paper summarizes the current data on the prothrombin catalytic domain A-chain region and the subsequent thrombin A-chain. Attention is given to biochemical characterization of naturally occurring prothrombin A-chain mutations and alanine scanning mutants in this region. While originally considered to be simply an activation remnant with little physiologic function, the thrombin A-chain is now thought to play a role as an allosteric effector in enzymatic reactions and may also be a structural scaffold to stabilize the protease domain. PMID:22084659

  2. Allosteric initiation and regulation of catalysis with a molecular knot.

    PubMed

    Marcos, Vanesa; Stephens, Alexander J; Jaramillo-Garcia, Javier; Nussbaumer, Alina L; Woltering, Steffen L; Valero, Alberto; Lemonnier, Jean-François; Vitorica-Yrezabal, Iñigo J; Leigh, David A

    2016-06-24

    Molecular knots occur in DNA, proteins, and other macromolecules. However, the benefits that can potentially arise from tying molecules in knots are, for the most part, unclear. Here, we report on a synthetic molecular pentafoil knot that allosterically initiates or regulates catalyzed chemical reactions by controlling the in situ generation of a carbocation formed through the knot-promoted cleavage of a carbon-halogen bond. The knot architecture is crucial to this function because it restricts the conformations that the molecular chain can adopt and prevents the formation of catalytically inactive species upon metal ion binding. Unknotted analogs are not catalytically active. Our results suggest that knotting molecules may be a useful strategy for reducing the degrees of freedom of flexible chains, enabling them to adopt what are otherwise thermodynamically inaccessible functional conformations. PMID:27339983

  3. Controlling mammalian gene expression by allosteric hepatitis delta virus ribozymes.

    PubMed

    Nomura, Yoko; Zhou, Linlin; Miu, Anh; Yokobayashi, Yohei

    2013-12-20

    We engineered small molecule responsive allosteric ribozymes based on the genomic hepatitis delta virus (HDV) ribozyme by replacing the P4-L4 stem-loop with an RNA aptamer through a connector stem. When embedded in the 3' untranslated region of a reporter gene mRNA, these RNA devices enabled regulation of cis-gene expression by theophylline and guanine by up to 29.5-fold in mammalian cell culture. Furthermore, a NOR logic gate device was constructed by placing two engineered ribozymes in tandem, demonstrating the modularity of the RNA devices. The significant improvement in the regulatory dynamic range (ON/OFF ratio) of the RNA devices based on the HDV ribozyme should provide new opportunities for practical applications. PMID:23697539

  4. Dynamic Modulation of DNA Hybridization Using Allosteric DNA Tetrahedral Nanostructures.

    PubMed

    Song, Ping; Li, Min; Shen, Juwen; Pei, Hao; Chao, Jie; Su, Shao; Aldalbahi, Ali; Wang, Lihua; Shi, Jiye; Song, Shiping; Wang, Lianhui; Fan, Chunhai; Zuo, Xiaolei

    2016-08-16

    The fixed dynamic range of traditional biosensors limits their utility in several real applications. For example, viral load monitoring requires the dynamic range spans several orders of magnitude; whereas, monitoring of drugs requires extremely narrow dynamic range. To overcome this limitation, here, we devised tunable biosensing interface using allosteric DNA tetrahedral bioprobes to tune the dynamic range of DNA biosensors. Our strategy takes the advantage of the readily and flexible structure design and predictable geometric reconfiguration of DNA nanotechnology. We reconfigured the DNA tetrahedral bioprobes by inserting the effector sequence into the DNA tetrahedron, through which, the binding affinity of DNA tetrahedral bioprobes can be tuned. As a result, the detection limit of DNA biosensors can be programmably regulated. The dynamic range of DNA biosensors can be tuned (narrowed or extended) for up to 100-fold. Using the regulation of binding affinity, we realized the capture and release of biomolecules by tuning the binding behavior of DNA tetrahedral bioprobes. PMID:27435955

  5. Allosteric control in a metalloprotein dramatically alters function

    PubMed Central

    Baxter, Elizabeth Leigh; Zuris, John A.; Wang, Charles; Vo, Phu Luong T.; Axelrod, Herbert L.; Cohen, Aina E.; Paddock, Mark L.; Nechushtai, Rachel; Onuchic, Jose N.; Jennings, Patricia A.

    2013-01-01

    Metalloproteins (MPs) comprise one-third of all known protein structures. This diverse set of proteins contain a plethora of unique inorganic moieties capable of performing chemistry that would otherwise be impossible using only the amino acids found in nature. Most of the well-studied MPs are generally viewed as being very rigid in structure, and it is widely thought that the properties of the metal centers are primarily determined by the small fraction of amino acids that make up the local environment. Here we examine both theoretically and experimentally whether distal regions can influence the metal center in the diabetes drug target mitoNEET. We demonstrate that a loop (L2) 20 Å away from the metal center exerts allosteric control over the cluster binding domain and regulates multiple properties of the metal center. Mutagenesis of L2 results in significant shifts in the redox potential of the [2Fe-2S] cluster and orders of magnitude effects on the rate of [2Fe-2S] cluster transfer to an apo-acceptor protein. These surprising effects occur in the absence of any structural changes. An examination of the native basin dynamics of the protein using all-atom simulations shows that twisting in L2 controls scissoring in the cluster binding domain and results in perturbations to one of the cluster-coordinating histidines. These allosteric effects are in agreement with previous folding simulations that predicted L2 could communicate with residues surrounding the metal center. Our findings suggest that long-range dynamical changes in the protein backbone can have a significant effect on the functional properties of MPs. PMID:23271805

  6. The Allosteric Binding Sites of Sulfotransferase 1A1

    PubMed Central

    Cook, Ian; Wang, Ting; Falany, Charles N.

    2015-01-01

    Human sulfotransferases (SULTs) comprise a small, 13-member enzyme family that regulates the activities of thousands of compounds—endogenous metabolites, drugs, and other xenobiotics. SULTs transfer the sulfuryl-moiety (–SO3) from a nucleotide donor, PAPS (3′-phosphoadenosine 5′-phosphosulfate), to the hydroxyls and primary amines of acceptors. SULT1A1, a progenitor of the family, has evolved to sulfonate compounds that are remarkably structurally diverse. SULT1A1, which is found in many tissues, is the predominant SULT in liver, where it is a major component of phase II metabolism. Early work demonstrated that catechins and nonsteroidal anti-inflammatory drugs inhibit SULT1A1 and suggested that the inhibition was not competitive versus substrates. Here, the mechanism of inhibition of a single, high affinity representative from each class [epigallocatechin gallate (EGCG) and mefenamic acid] is determined using initial-rate and equilibrium-binding studies. The findings reveal that the inhibitors bind at sites separate from those of substrates, and at saturation turnover of the enzyme is reduced to a nonzero value. Further, the EGCG inhibition patterns suggest a molecular explanation for its isozyme specificity. Remarkably, the inhibitors bind at sites that are separate from one another, and binding at one site does not affect affinity at the other. For the first time, it is clear that SULT1A1 is allosterically regulated, and that it contains at least two, functionally distinct allosteric sites, each of which responds to a different class of compounds. PMID:25534770

  7. A Novel Allosteric Inhibitor of Macrophage Migration Inhibitory Factor (MIF)*

    PubMed Central

    Bai, Fengwei; Asojo, Oluwatoyin A.; Cirillo, Pier; Ciustea, Mihai; Ledizet, Michel; Aristoff, Paul A.; Leng, Lin; Koski, Raymond A.; Powell, Thomas J.; Bucala, Richard; Anthony, Karen G.

    2012-01-01

    Macrophage migration inhibitory factor (MIF) is a catalytic cytokine and an upstream mediator of the inflammatory pathway. MIF has broad regulatory properties, dysregulation of which has been implicated in the pathology of multiple immunological diseases. Inhibition of MIF activity with small molecules has proven beneficial in a number of disease models. Known small molecule MIF inhibitors typically bind in the tautomerase site of the MIF trimer, often covalently modifying the catalytic proline. Allosteric MIF inhibitors, particularly those that associate with the protein by noncovalent interactions, could reveal novel ways to block MIF activity for therapeutic benefit and serve as chemical probes to elucidate the structural basis for the diverse regulatory properties of MIF. In this study, we report the identification and functional characterization of a novel allosteric MIF inhibitor. Identified from a high throughput screening effort, this sulfonated azo compound termed p425 strongly inhibited the ability of MIF to tautomerize 4-hydroxyphenyl pyruvate. Furthermore, p425 blocked the interaction of MIF with its receptor, CD74, and interfered with the pro-inflammatory activities of the cytokine. Structural studies revealed a unique mode of binding for p425, with a single molecule of the inhibitor occupying the interface of two MIF trimers. The inhibitor binds MIF mainly on the protein surface through hydrophobic interactions that are stabilized by hydrogen bonding with four highly specific residues from three different monomers. The mode of p425 binding reveals a unique way to block the activity of the cytokine for potential therapeutic benefit in MIF-associated diseases. PMID:22782901

  8. Allosteric Optical Control of a Class B G-Protein-Coupled Receptor.

    PubMed

    Broichhagen, Johannes; Johnston, Natalie R; von Ohlen, Yorrick; Meyer-Berg, Helena; Jones, Ben J; Bloom, Stephen R; Rutter, Guy A; Trauner, Dirk; Hodson, David J

    2016-05-01

    Allosteric regulation promises to open up new therapeutic avenues by increasing drug specificity at G-protein-coupled receptors (GPCRs). However, drug discovery efforts are at present hampered by an inability to precisely control the allosteric site. Herein, we describe the design, synthesis, and testing of PhotoETP, a light-activated positive allosteric modulator of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR involved in the maintenance of glucose homeostasis in humans. PhotoETP potentiates Ca(2+) , cAMP, and insulin responses to glucagon-like peptide-1 and its metabolites following illumination of cells with blue light. PhotoETP thus provides a blueprint for the production of small-molecule class B GPCR allosteric photoswitches, and may represent a useful tool for understanding positive cooperativity at the GLP-1R. PMID:27059784

  9. Structural Features of Ion Transport and Allosteric Regulation in Sodium-Calcium Exchanger (NCX) Proteins.

    PubMed

    Giladi, Moshe; Tal, Inbal; Khananshvili, Daniel

    2016-01-01

    rigidifies local backbone segments of CBD2, but not of CBD1. The extent and strength of Ca(2+)-dependent rigidification at CBD2 is splice-variant dependent, showing clear correlations with phenotypes of matching NCX variants. Therefore, diverse NCX variants share a common mechanism for the initial decoding of the regulatory signal upon Ca(2+) binding at the interface of CBDs, whereas the allosteric message is shaped by CBD2, the dynamic features of which are dictated by the splicing segment. PMID:26903880

  10. Bio-layer interferometry for measuring kinetics of protein-protein interactions and allosteric ligand effects.

    PubMed

    Shah, Naman B; Duncan, Thomas M

    2014-01-01

    We describe the use of Bio-layer Interferometry to study inhibitory interactions of subunit ε with the catalytic complex of Escherichia coli ATP synthase. Bacterial F-type ATP synthase is the target of a new, FDA-approved antibiotic to combat drug-resistant tuberculosis. Understanding bacteria-specific auto-inhibition of ATP synthase by the C-terminal domain of subunit ε could provide a new means to target the enzyme for discovery of antibacterial drugs. The C-terminal domain of ε undergoes a dramatic conformational change when the enzyme transitions between the active and inactive states, and catalytic-site ligands can influence which of ε's conformations is predominant. The assay measures kinetics of ε's binding/dissociation with the catalytic complex, and indirectly measures the shift of enzyme-bound ε to and from the apparently nondissociable inhibitory conformation. The Bio-layer Interferometry signal is not overly sensitive to solution composition, so it can also be used to monitor allosteric effects of catalytic-site ligands on ε's conformational changes. PMID:24638157

  11. Insights into allosteric control of vinculin function from its large scale conformational dynamics.

    PubMed

    Chen, Yiwen; Dokholyan, Nikolay V

    2006-09-29

    Vinculin is an important constituent of both cell-cell and cell-matrix junctions, where it plays crucial roles in the regulation of cell adhesion and migration. When activated, it mediates the linkage between cadherins (cell-cell) or integrins (cell-matrix) and the actin cytoskeleton through interactions with various proteins. The activation of vinculin requires structural conversions from an autoinhibited conformation to the "open" conformations in which the occluded binding sites of its different ligands become exposed, while the structural dynamics underlying the vinculin activation remains largely unknown. Here we report the first computational study of large scale conformational dynamics of full-length vinculin. We find that the "holding" and "releasing" motions between vinculin tail and pincer-like structure formed by first three domains of vinculin are the dominant motions near the native state of vinculin, indicating that an inherent flexibility of vinculin has a large influence on its allostery. We also find a cooperative dissociation between the head and tail domains of vinculin with increasing temperature in both thermodynamic and kinetic simulations, implying that vinculin may function as an allosteric switch in response to external signals. We show that the kinetics of vinculin unfolding exhibits specific sequential patterns, suggesting that a sophisticated interplay between domains may synergistically contribute to vinculin activation. We further find that the interaction between vinculin-binding site peptide from talin and vinculin significantly destabilizes the intramolecular head-tail interactions, suggesting a direct role of talin binding in vinculin activation. PMID:16891659

  12. Bacterial rotary export ATPases are allosterically regulated by the nucleotide second messenger cyclic-di-GMP.

    PubMed

    Trampari, Eleftheria; Stevenson, Clare E M; Little, Richard H; Wilhelm, Thomas; Lawson, David M; Malone, Jacob G

    2015-10-01

    The widespread second messenger molecule cyclic di-GMP (cdG) regulates the transition from motile and virulent lifestyles to sessile, biofilm-forming ones in a wide range of bacteria. Many pathogenic and commensal bacterial-host interactions are known to be controlled by cdG signaling. Although the biochemistry of cyclic dinucleotide metabolism is well understood, much remains to be discovered about the downstream signaling pathways that induce bacterial responses upon cdG binding. As part of our ongoing research into the role of cdG signaling in plant-associated Pseudomonas species, we carried out an affinity capture screen for cdG binding proteins in the model organism Pseudomonas fluorescens SBW25. The flagella export AAA+ ATPase FliI was identified as a result of this screen and subsequently shown to bind specifically to the cdG molecule, with a KD in the low micromolar range. The interaction between FliI and cdG appears to be very widespread. In addition to FliI homologs from diverse bacterial species, high affinity binding was also observed for the type III secretion system homolog HrcN and the type VI ATPase ClpB2. The addition of cdG was shown to inhibit FliI and HrcN ATPase activity in vitro. Finally, a combination of site-specific mutagenesis, mass spectrometry, and in silico analysis was used to predict that cdG binds to FliI in a pocket of highly conserved residues at the interface between two FliI subunits. Our results suggest a novel, fundamental role for cdG in controlling the function of multiple important bacterial export pathways, through direct allosteric control of export ATPase proteins. PMID:26265469

  13. Bacterial Rotary Export ATPases Are Allosterically Regulated by the Nucleotide Second Messenger Cyclic-di-GMP*

    PubMed Central

    Trampari, Eleftheria; Stevenson, Clare E. M.; Little, Richard H.; Wilhelm, Thomas; Lawson, David M.; Malone, Jacob G.

    2015-01-01

    The widespread second messenger molecule cyclic di-GMP (cdG) regulates the transition from motile and virulent lifestyles to sessile, biofilm-forming ones in a wide range of bacteria. Many pathogenic and commensal bacterial-host interactions are known to be controlled by cdG signaling. Although the biochemistry of cyclic dinucleotide metabolism is well understood, much remains to be discovered about the downstream signaling pathways that induce bacterial responses upon cdG binding. As part of our ongoing research into the role of cdG signaling in plant-associated Pseudomonas species, we carried out an affinity capture screen for cdG binding proteins in the model organism Pseudomonas fluorescens SBW25. The flagella export AAA+ ATPase FliI was identified as a result of this screen and subsequently shown to bind specifically to the cdG molecule, with a KD in the low micromolar range. The interaction between FliI and cdG appears to be very widespread. In addition to FliI homologs from diverse bacterial species, high affinity binding was also observed for the type III secretion system homolog HrcN and the type VI ATPase ClpB2. The addition of cdG was shown to inhibit FliI and HrcN ATPase activity in vitro. Finally, a combination of site-specific mutagenesis, mass spectrometry, and in silico analysis was used to predict that cdG binds to FliI in a pocket of highly conserved residues at the interface between two FliI subunits. Our results suggest a novel, fundamental role for cdG in controlling the function of multiple important bacterial export pathways, through direct allosteric control of export ATPase proteins. PMID:26265469

  14. Contact rearrangements form coupled networks from local motions in allosteric proteins.

    PubMed

    Daily, Michael D; Upadhyaya, Tarak J; Gray, Jeffrey J

    2008-04-01

    Allosteric proteins bind an effector molecule at one site resulting in a functional change at a second site. We hypothesize that networks of contacts altered, formed, or broken are a significant contributor to allosteric communication in proteins. In this work, we identify which interactions change significantly between the residue-residue contact networks of two allosteric structures, and then organize these changes into graphs. We perform the analysis on 15 pairs of allo