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Roman-Ramos H, Prieto-da-Silva ÁRB, Dellê H, Floriano RS, Dias L, Hyslop S, Schezaro-Ramos R, Servent D, Mourier G, de Oliveira JL, Lemes DE, Costa-Lotufo LV, Oliveira JS, Menezes MC, Markus RP, Ho PL. The Cloning and Characterization of a Three-Finger Toxin Homolog (NXH8) from the Coralsnake Micrurus corallinus That Interacts with Skeletal Muscle Nicotinic Acetylcholine Receptors. Toxins (Basel) 2024; 16:164. [PMID: 38668589 PMCID: PMC11054780 DOI: 10.3390/toxins16040164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/04/2024] [Accepted: 03/20/2024] [Indexed: 04/29/2024] Open
Abstract
Coralsnakes (Micrurus spp.) are the only elapids found throughout the Americas. They are recognized for their highly neurotoxic venom, which is comprised of a wide variety of toxins, including the stable, low-mass toxins known as three-finger toxins (3FTx). Due to difficulties in venom extraction and availability, research on coralsnake venoms is still very limited when compared to that of other Elapidae snakes like cobras, kraits, and mambas. In this study, two previously described 3FTx from the venom of M. corallinus, NXH1 (3SOC1_MICCO), and NXH8 (3NO48_MICCO) were characterized. Using in silico, in vitro, and ex vivo experiments, the biological activities of these toxins were predicted and evaluated. The results showed that only NXH8 was capable of binding to skeletal muscle cells and modulating the activity of nAChRs in nerve-diaphragm preparations. These effects were antagonized by anti-rNXH8 or antielapidic sera. Sequence analysis revealed that the NXH1 toxin possesses eight cysteine residues and four disulfide bonds, while the NXH8 toxin has a primary structure similar to that of non-conventional 3FTx, with an additional disulfide bond on the first loop. These findings add more information related to the structural diversity present within the 3FTx class, while expanding our understanding of the mechanisms of the toxicity of this coralsnake venom and opening new perspectives for developing more effective therapeutic interventions.
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Affiliation(s)
- Henrique Roman-Ramos
- Laboratório de Biotecnologia, Programa de Pós-Graduação em Medicina, Universidade Nove de Julho (UNINOVE), São Paulo 01504-001, SP, Brazil; (H.D.); (J.L.d.O.); (D.E.L.)
| | | | - Humberto Dellê
- Laboratório de Biotecnologia, Programa de Pós-Graduação em Medicina, Universidade Nove de Julho (UNINOVE), São Paulo 01504-001, SP, Brazil; (H.D.); (J.L.d.O.); (D.E.L.)
| | - Rafael S. Floriano
- Laboratório de Toxinologia e Estudos Cardiovasculares, Universidade do Oeste Paulista (UNOESTE), Presidente Prudente 19067-175, SP, Brazil;
| | - Lourdes Dias
- Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas 13083-887, SP, Brazil; (L.D.); (S.H.); (R.S.-R.)
| | - Stephen Hyslop
- Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas 13083-887, SP, Brazil; (L.D.); (S.H.); (R.S.-R.)
| | - Raphael Schezaro-Ramos
- Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas 13083-887, SP, Brazil; (L.D.); (S.H.); (R.S.-R.)
| | - Denis Servent
- Service d’Ingénierie Moléculaire pour la Santé (SIMoS), Département Médicaments et Technologies pour la Santé, Université Paris Saclay, Commissariat à l’énergie Atomique et aux Énergies Alternatives (CEA), F-91191 Gif sur Yvette, France; (D.S.); (G.M.)
| | - Gilles Mourier
- Service d’Ingénierie Moléculaire pour la Santé (SIMoS), Département Médicaments et Technologies pour la Santé, Université Paris Saclay, Commissariat à l’énergie Atomique et aux Énergies Alternatives (CEA), F-91191 Gif sur Yvette, France; (D.S.); (G.M.)
| | - Jéssica Lopes de Oliveira
- Laboratório de Biotecnologia, Programa de Pós-Graduação em Medicina, Universidade Nove de Julho (UNINOVE), São Paulo 01504-001, SP, Brazil; (H.D.); (J.L.d.O.); (D.E.L.)
| | - Douglas Edgard Lemes
- Laboratório de Biotecnologia, Programa de Pós-Graduação em Medicina, Universidade Nove de Julho (UNINOVE), São Paulo 01504-001, SP, Brazil; (H.D.); (J.L.d.O.); (D.E.L.)
| | - Letícia V. Costa-Lotufo
- Departamento de Farmacologia, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP), São Paulo 05508-000, SP, Brazil;
| | - Jane S. Oliveira
- Centro de Biotecnologia, Instituto Butantan, São Paulo 05503-900, SP, Brazil;
| | | | - Regina P. Markus
- Laboratório de Cronofarmacologia, Instituto de Biociências, Universidade de São Paulo (USP), São Paulo 05508-090, SP, Brazil;
| | - Paulo Lee Ho
- Centro Bioindustrial, Instituto Butantan, São Paulo 05503-900, SP, Brazil;
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Jiang Y, Lin L, Chen S, Jiang L, Kriegbaum MC, Gårdsvoll H, Hansen LV, Li J, Ploug M, Yuan C, Huang M. Crystal Structures of Human C4.4A Reveal the Unique Association of Ly6/uPAR/α-neurotoxin Domain. Int J Biol Sci 2020; 16:981-993. [PMID: 32140067 PMCID: PMC7053344 DOI: 10.7150/ijbs.39919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/26/2019] [Indexed: 01/26/2023] Open
Abstract
Ly6/uPAR/α-neurotoxin domain (LU-domain) is characterized by the presence of 4-5 disulfide bonds and three flexible loops that extend from a core stacked by several conversed disulfide bonds (thus also named three-fingered protein domain). This highly structurally stable protein domain is typically a protein-binder at extracellular space. Most LU proteins contain only single LU-domain as represented by Ly6 proteins in immunology and α-neurotoxins in snake venom. For Ly6 proteins, many are expressed in specific cell lineages and in differentiation stages, and are used as markers. In this study, we report the crystal structures of the two LU-domains of human C4.4A alone and its complex with a Fab fragment of a monoclonal anti-C4.4A antibody. Interestingly, both structures showed that C4.4A forms a very compact globule with two LU-domain packed face to face. This is in contrast to the flexible nature of most LU-domain-containing proteins in mammals. The Fab combining site of C4.4A involves both LU-domains, and appears to be the binding site for AGR2, a reported ligand of C4.4A. This work reports the first structure that contain two LU-domains and provides insights on how LU-domains fold into a compact protein and interacts with ligands.
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Affiliation(s)
- Yunbin Jiang
- State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lin Lin
- Institute of Oceanography, Minjiang University, Fuzhou, 350108, China
| | - Shanli Chen
- College of Chemistry, Fuzhou University, Fuzhou, Fujian, China
| | - Longguang Jiang
- College of Chemistry, Fuzhou University, Fuzhou, Fujian, China
| | - Mette C Kriegbaum
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2220 Copenhagen N, Denmark
| | - Henrik Gårdsvoll
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2220 Copenhagen N, Denmark
| | - Line V Hansen
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark
| | - Jinyu Li
- College of Chemistry, Fuzhou University, Fuzhou, Fujian, China
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-2220 Copenhagen N, Denmark
| | - Cai Yuan
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian, 350116, China
| | - Mingdong Huang
- State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China.,College of Chemistry, Fuzhou University, Fuzhou, Fujian, China
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Girish VM, Kumar S, Joseph L, Jobichen C, Kini RM, Sivaraman J. Identification and structural characterization of a new three-finger toxin hemachatoxin from Hemachatus haemachatus venom. PLoS One 2012; 7:e48112. [PMID: 23144733 PMCID: PMC3483290 DOI: 10.1371/journal.pone.0048112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Accepted: 09/19/2012] [Indexed: 01/26/2023] Open
Abstract
Snake venoms are rich sources of biologically active proteins and polypeptides. Three-finger toxins are non-enzymatic proteins present in elapid (cobras, kraits, mambas and sea snakes) and colubrid venoms. These proteins contain four conserved disulfide bonds in the core to maintain the three-finger folds. Although all three-finger toxins have similar fold, their biological activities are different. A new three-finger toxin (hemachatoxin) was isolated from Hemachatus haemachatus (Ringhals cobra) venom. Its amino acid sequence was elucidated, and crystal structure was determined at 2.43 Å resolution. The overall fold is similar to other three-finger toxins. The structure and sequence analysis revealed that the fold is maintained by four highly conserved disulfide bonds. It exhibited highest similarity to particularly P-type cardiotoxins that are known to associate and perturb the membrane surface with their lipid binding sites. Also, the increased B value of hemachotoxin loop II suggests that loop II is flexible and may remain flexible until its interaction with membrane phospholipids. Based on the analysis, we predict hemachatoxin to be cardiotoxic/cytotoxic and our future experiments will be directed to characterize the activity of hemachatoxin.
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Affiliation(s)
| | - Sundramurthy Kumar
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - Lissa Joseph
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - Chacko Jobichen
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - R. Manjunatha Kini
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail: (RMK); (JS)
| | - J. Sivaraman
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
- * E-mail: (RMK); (JS)
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Roy A, Zhou X, Chong MZ, D'hoedt D, Foo CS, Rajagopalan N, Nirthanan S, Bertrand D, Sivaraman J, Kini RM. Structural and functional characterization of a novel homodimeric three-finger neurotoxin from the venom of Ophiophagus hannah (king cobra). J Biol Chem 2010; 285:8302-15. [PMID: 20071329 DOI: 10.1074/jbc.m109.074161] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Snake venoms are a mixture of pharmacologically active proteins and polypeptides that have led to the development of molecular probes and therapeutic agents. Here, we describe the structural and functional characterization of a novel neurotoxin, haditoxin, from the venom of Ophiophagus hannah (King cobra). Haditoxin exhibited novel pharmacology with antagonism toward muscle (alphabetagammadelta) and neuronal (alpha(7), alpha(3)beta(2), and alpha(4)beta(2)) nicotinic acetylcholine receptors (nAChRs) with highest affinity for alpha(7)-nAChRs. The high resolution (1.5 A) crystal structure revealed haditoxin to be a homodimer, like kappa-neurotoxins, which target neuronal alpha(3)beta(2)- and alpha(4)beta(2)-nAChRs. Interestingly however, the monomeric subunits of haditoxin were composed of a three-finger protein fold typical of curaremimetic short-chain alpha-neurotoxins. Biochemical studies confirmed that it existed as a non-covalent dimer species in solution. Its structural similarity to short-chain alpha-neurotoxins and kappa-neurotoxins notwithstanding, haditoxin exhibited unique blockade of alpha(7)-nAChRs (IC(50) 180 nm), which is recognized by neither short-chain alpha-neurotoxins nor kappa-neurotoxins. This is the first report of a dimeric short-chain alpha-neurotoxin interacting with neuronal alpha(7)-nAChRs as well as the first homodimeric three-finger toxin to interact with muscle nAChRs.
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Affiliation(s)
- Amrita Roy
- Department of Biological Sciences, National University of Singapore, Singapore
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Loughnan ML, Nicke A, Lawrence N, Lewis RJ. Novel αD-Conopeptides and Their Precursors Identified by cDNA Cloning Define the D-Conotoxin Superfamily. Biochemistry 2009; 48:3717-29. [DOI: 10.1021/bi9000326] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Marion L. Loughnan
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia, and Max Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt/Main, Germany
| | - Annette Nicke
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia, and Max Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt/Main, Germany
| | - Nicole Lawrence
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia, and Max Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt/Main, Germany
| | - Richard J. Lewis
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia, and Max Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt/Main, Germany
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Fry BG, Vidal N, van der Weerd L, Kochva E, Renjifo C. Evolution and diversification of the Toxicofera reptile venom system. J Proteomics 2009; 72:127-36. [DOI: 10.1016/j.jprot.2009.01.009] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Accepted: 01/12/2009] [Indexed: 11/25/2022]
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Hogg RC, Bertrand D. Neurotoxins acting at nicotinic receptors. Future Neurology 2008. [DOI: 10.2217/14796708.3.4.463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Neurotoxins include, in the most general sense, all molecules that destroy or inhibit the proper functioning of the nervous system. Neurotoxins from animals and plants include alkaloids and peptides, many of which interact with physiological processes in a selective manner. The majority of neurotoxins disrupt the transmission of signals in the nervous system by interfering with synaptic transmission. Neurotoxins can act presynaptically to inhibit the release, uptake and recycling of neurotransmitters or postsynaptically, binding to receptors on the postsynaptic membrane and preventing their activation by neurotransmitters. A class of neurotoxins from plants and animals interact with nicotinic acetylcholine receptors, either at the neuromuscular junction, peripherally at neuronal ganglia or centrally, to produce neurotoxic effects. In this article we review current knowledge of some of these neurotoxins, their structure, pharmacology, importance as pharmaceutical tools as well as future prospects for the development of therapeutic molecules.
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Affiliation(s)
- Ron C Hogg
- University of Geneva, Department of Neurosciences Fondamentales, Faculty of Medicine, 1, rue Michel Servet, CH-1211 Geneva 4, Switzerland
| | - Daniel Bertrand
- University of Geneva, Department of Neurosciences Fondamentales, Faculty of Medicine, Switzerland
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Abstract
PiQSi facilitates the manual investigation of the quaternary structure of protein complexes in the Protein Data Bank (PDB). Users can browse and obtain an overview of the quaternary structure information of a given protein together with its evolutionary relatives, which helps in the determination of the biological quaternary state. I have used this framework to annotate over 10,000 structures from the PDB Biological Unit and corrected the quaternary state of approximately 15% of them. A benchmark shows that the annotations are of high quality and stresses the need for manual curation, in particular for ambiguous cases such as proteins in equilibrium between two quaternary states. The approximately 10,000 annotations already in the database can be used to improve the accuracy of analyses on protein structure or to benchmark methods that predict protein quaternary structure. In addition, PiQSi incorporates a community-based curation system, which I hope will allow us to reach an accurate and complete description of the biological quaternary state of proteins in PDB. PiQSi is accessible at http://www.PiQSi.org/.
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Loughnan M, Nicke A, Jones A, Schroeder CI, Nevin ST, Adams DJ, Alewood PF, Lewis RJ. Identification of a Novel Class of Nicotinic Receptor Antagonists. J Biol Chem 2006; 281:24745-55. [PMID: 16790424 DOI: 10.1074/jbc.m603703200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The venoms of predatory marine snails (Conus spp.) contain diverse mixtures of peptide toxins with high potency and selectivity for a variety of voltage-gated and ligand-gated ion channels. Here we describe the chemical and functional characterization of three novel conotoxins, alphaD-VxXIIA, alphaD-VxXIIB, and alphaD-VxXIIC, purified from the venom of Conus vexillum. Each toxin was observed as an approximately 11-kDa protein by LC/MS, size exclusion chromatography, and SDS-PAGE. After reduction, the peptide sequences were determined by Edman degradation chemistry and tandem MS. Combining the sequence data together with LC/MS and NMR data revealed that in solution these toxins are pseudo-homodimers of paired 47-50-residue peptides. The toxin subunits exhibited a novel arrangement of 10 conserved cystine residues, and additional post-translational modifications contributed heterogeneity to the proteins. Binding assays and two-electrode voltage clamp analyses showed that alphaD-VxXIIA, alphaD-VxXIIB, and alphaD-VxXIIC are potent inhibitors of nicotinic acetylcholine receptors (nAChRs) with selectivity for alpha7 and beta2 containing neuronal nAChR subtypes. These dimeric conotoxins represent a fifth and highly divergent structural class of conotoxins targeting nAChRs.
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Affiliation(s)
- Marion Loughnan
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
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Phui Yee JS, Nanling G, Afifiyan F, Donghui M, Siew Lay P, Armugam A, Jeyaseelan K. Snake postsynaptic neurotoxins: gene structure, phylogeny and applications in research and therapy. Biochimie 2004; 86:137-49. [PMID: 15016453 DOI: 10.1016/j.biochi.2003.11.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2003] [Accepted: 11/28/2003] [Indexed: 11/15/2022]
Abstract
Snake venoms are complex mixtures of biologically active polypeptides that target a variety of vital physiological functions in mammals. alpha-Neurotoxins, toxins that cause paralysis by binding to the nicotinic receptors at the postsynaptic region of the neuromuscular junction have been widely studied in terms of their structure-function relationships as well as gene structure, organization and expression. In this review, we describe the structure of alpha-neurotoxin genes and discuss their evolutionary relationships. Almost all members of neurotoxins have been found to exhibit a common evolutionary origin. The importance of alpha-neurotoxins in therapy and research has also been discussed to highlight their potential applications especially in the area of drug discovery.
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Affiliation(s)
- Joyce Siew Phui Yee
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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Abstract
Identification of all residues involved in the recognition and binding of cholinergic ligands (e.g. agonists, competitive antagonists, and noncompetitive agonists) is a primary objective to understand which structural components are related to the physiological function of the nicotinic acetylcholine receptor (AChR). The picture for the localization of the agonist/competitive antagonist binding sites is now clearer in the light of newer and better experimental evidence. These sites are located mainly on both alpha subunits in a pocket approximately 30-35 A above the surface membrane. Since both alpha subunits are identical, the observed high and low affinity for different ligands on the receptor is conditioned by the interaction of the alpha subunit with other non-alpha subunits. This molecular interaction takes place at the interface formed by the different subunits. For example, the high-affinity acetylcholine (ACh) binding site of the muscle-type AChR is located on the alphadelta subunit interface, whereas the low-affinity ACh binding site is located on the alphagamma subunit interface. Regarding homomeric AChRs (e.g. alpha7, alpha8, and alpha9), up to five binding sites may be located on the alphaalpha subunit interfaces. From the point of view of subunit arrangement, the gamma subunit is in between both alpha subunits and the delta subunit follows the alpha aligned in a clockwise manner from the gamma. Although some competitive antagonists such as lophotoxin and alpha-bungarotoxin bind to the same high- and low-affinity sites as ACh, other cholinergic drugs may bind with opposite specificity. For instance, the location of the high- and the low-affinity binding site for curare-related drugs as well as for agonists such as the alkaloid nicotine and the potent analgesic epibatidine (only when the AChR is in the desensitized state) is determined by the alphagamma and the alphadelta subunit interface, respectively. The case of alpha-conotoxins (alpha-CoTxs) is unique since each alpha-CoTx from different species is recognized by a specific AChR type. In addition, the specificity of alpha-CoTxs for each subunit interface is species-dependent. In general terms we may state that both alpha subunits carry the principal component for the agonist/competitive antagonist binding sites, whereas the non-alpha subunits bear the complementary component. Concerning homomeric AChRs, both the principal and the complementary component exist on the alpha subunit. The principal component on the muscle-type AChR involves three loops-forming binding domains (loops A-C). Loop A (from mouse sequence) is mainly formed by residue Y(93), loop B is molded by amino acids W(149), Y(152), and probably G(153), while loop C is shaped by residues Y(190), C(192), C(193), and Y(198). The complementary component corresponding to each non-alpha subunit probably contributes with at least four loops. More specifically, the loops at the gamma subunit are: loop D which is formed by residue K(34), loop E that is designed by W(55) and E(57), loop F which is built by a stretch of amino acids comprising L(109), S(111), C(115), I(116), and Y(117), and finally loop G that is shaped by F(172) and by the negatively-charged amino acids D(174) and E(183). The complementary component on the delta subunit, which corresponds to the high-affinity ACh binding site, is formed by homologous loops. Regarding alpha-neurotoxins, several snake and alpha-CoTxs bear specific residues that are energetically coupled with their corresponding pairs on the AChR binding site. The principal component for snake alpha-neurotoxins is located on the residue sequence alpha1W(184)-D(200), which includes loop C. In addition, amino acid sequence 55-74 from the alpha1 subunit (which includes loop E), and residues gammaL(119) (close to loop F) and gammaE(176) (close to loop G) at the low-affinity binding site, or deltaL(121) (close to the homologous region of loop G) at the high-affinity binding site, are i
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Affiliation(s)
- H R Arias
- Instituto de Matemática de Bahía Blanca, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahía Blanca, Argentina.
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