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Naulin PA, Lozano B, Fuentes C, Liu Y, Schmidt C, Contreras JE, Barrera NP. Polydisperse molecular architecture of connexin 26/30 heteromeric hemichannels revealed by atomic force microscopy imaging. J Biol Chem 2020; 295:16499-16509. [PMID: 32887797 PMCID: PMC7864052 DOI: 10.1074/jbc.ra119.012128] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 08/31/2020] [Indexed: 11/06/2022] Open
Abstract
Connexin (Cx) protein forms hemichannels and gap junctional channels, which play diverse and profound roles in human physiology and diseases. Gap junctions are arrays of intercellular channels formed by the docking of two hemichannels from adjacent cells. Each hexameric hemichannel contains the same or different Cx isoform. Although homomeric Cxs forms have been largely described functionally and structurally, the stoichiometry and arrangement of heteromeric Cx channels remain unknown. The latter, however, are widely expressed in human tissues and variation might have important implications on channel function. Investigating properties of heteromeric Cx channels is challenging considering the high number of potential subunit arrangements and stoichiometries, even when only combining two Cx isoforms. To tackle this problem, we engineered an HA tag onto Cx26 or Cx30 subunits and imaged hemichannels that were liganded by Fab-epitope antibody fragments via atomic force microscopy. For Cx26-HA/Cx30 or Cx30-HA/Cx26 heteromeric channels, the Fab-HA binding distribution was binomial with a maximum of three Fab-HA bound. Furthermore, imaged Cx26/Cx30-HA triple liganded by Fab-HA showed multiple arrangements that can be derived from the law of total probabilities. Atomic force microscopy imaging of ringlike structures of Cx26/Cx30-HA hemichannels confirmed these findings and also detected a polydisperse distribution of stoichiometries. Our results indicate a dominant subunit stoichiometry of 3Cx26:3Cx30 with the most abundant subunit arrangement of Cx26-Cx26-Cx30-Cx26-Cx30-Cx30. To our knowledge, this is the first time that the molecular architecture of heteromeric Cx channels has been revealed, thus providing the basis to explore the functional effect of these channels in biology.
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Affiliation(s)
- Pamela A Naulin
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Benjamin Lozano
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christian Fuentes
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Yu Liu
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Carla Schmidt
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Jorge E Contreras
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Nelson P Barrera
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile.
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Soto P, Gaete PS, Fuentes C, Lozano B, Naulin PA, Figueroa XF, Barrera NP. Function of P2X4 Receptors Is Directly Modulated by a 1:1 Stoichiometric Interaction With 5-HT 3A Receptors. Front Cell Neurosci 2020; 14:106. [PMID: 32431598 PMCID: PMC7214622 DOI: 10.3389/fncel.2020.00106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/07/2020] [Indexed: 12/30/2022] Open
Abstract
Interacting receptors at the neuronal plasma membrane represent an additional regulatory mode for intracellular transduction pathways. P2X4 receptor triggers fast neurotransmission responses via a transient increase in intracellular Ca2+ levels. It has been proposed that the P2X4 receptor interacts with the 5-HT3A receptor in hippocampal neurons, but their binding stoichiometry and the role of P2X4 receptor activation by ATP on this crosstalking system remains unknown. Via pull-down assays, total internal reflection fluorescence (TIRF) microscopy measurements of the receptors colocalization and expression at the plasma membrane, and atomic force microscopy (AFM) imaging, we have demonstrated that P2X4/5-HT3A receptor complexes can interact with each other in a 1:1 stoichiometric manner that is preserved after ATP binding. Also, macromolecular docking followed by 100 ns molecular dynamics (MD) simulations suggested that the interaction energy of the P2X4 receptor with 5-HT3A receptor is similar at the holo and the apo state of the P2X4 receptor, and the interacting 5-HT3A receptor decreased the ATP binding energy of P2X4 receptor. Finally, the P2X4 receptor-dependent Ca2+ mobilization is inhibited by the 5-HT3A interacting receptor. Altogether, these findings provide novel molecular insights into the allosteric regulation of P2X4/5-HT3A receptor complex in lipid bilayers of living cells via stoichiometric association, rather than accumulation or unspecific clustering of complexes.
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Affiliation(s)
- Paola Soto
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo S Gaete
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christian Fuentes
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Benjamin Lozano
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pamela A Naulin
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Xavier F Figueroa
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nelson Patricio Barrera
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
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3
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Purinergic system in psychiatric diseases. Mol Psychiatry 2018; 23:94-106. [PMID: 28948971 DOI: 10.1038/mp.2017.188] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 07/15/2017] [Accepted: 07/20/2017] [Indexed: 12/14/2022]
Abstract
Psychiatric disorders are debilitating diseases, affecting >80 million people worldwide. There are no causal cures for psychiatric disorders and available therapies only treat the symptoms. The etiology of psychiatric disorders is unknown, although it has been speculated to be a combination of environmental, stress and genetic factors. One of the neurotransmitter systems implicated in the biology of psychiatric disorders is the purinergic system. In this review, we performed a comprehensive search of the literature about the role and function of the purinergic system in the development and predisposition to psychiatric disorders, with a focus on depression, schizophrenia, bipolar disorder, autism, anxiety and attention deficit/hyperactivity disorder. We also describe how therapeutics used for psychiatric disorders act on the purinergic system.
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Pissinis DE, Diaz C, Maza E, Bonini IC, Barrantes FJ, Salvarezza RC, Schilardi PL. Functional nicotinic acetylcholine receptor reconstitution in Au(111)-supported thiolipid monolayers. NANOSCALE 2015; 7:15789-15797. [PMID: 26355753 DOI: 10.1039/c5nr04109k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The insertion and function of the muscle-type nicotinic acetylcholine receptor (nAChR) in Au(111)-supported thiolipid self-assembled monolayers have been studied by atomic force microscopy (AFM), surface plasmon resonance (SPR), and electrochemical techniques. It was possible for the first time to resolve the supramolecular arrangement of the protein spontaneously inserted in a thiolipid monolayer in an aqueous solution. Geometric supramolecular arrays of nAChRs were observed, most commonly in a triangular form compatible with three nAChR dimers of ∼20 nm each. Addition of the full agonist carbamoylcholine activated and opened the nAChR ion channel, as revealed by the increase in capacitance relative to that of the nAChR-thiolipid system under basal conditions. Thus, the self-assembled system appears to be a viable biomimetic model to measure ionic conductance mediated by ion-gated ion channels under different experimental conditions, with potential applications in biotechnology and pharmacology.
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Affiliation(s)
- Diego E Pissinis
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CONICET - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC16, Suc. 4, La Plata, Buenos Aires, Argentina.
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Marcuello C, Arilla-Luna S, Medina M, Lostao A. Detection of a quaternary organization into dimer of trimers of Corynebacterium ammoniagenes FAD synthetase at the single-molecule level and at the in cell level. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:665-76. [PMID: 23291469 DOI: 10.1016/j.bbapap.2012.12.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Revised: 12/11/2012] [Accepted: 12/21/2012] [Indexed: 01/24/2023]
Abstract
Biochemical characterization of Corynebacterium ammoniagenes FADS (CaFADS) pointed to certain confusion about the stoichiometry of this bifunctional enzyme involved in the production of FMN and FAD in prokaryotes. Resolution of its crystal structure suggested that it might produce a hexameric ensemble formed by a dimer of trimers. We used atomic force microscopy (AFM) to direct imaging single CaFADS molecules bound to mica surfaces, while preserving their catalytic properties. AFM allowed solving individual CaFADS monomers, for which it was even possible to distinguish their sub-molecular individual N- and C-terminal modules in the elongated enzyme. Differences between monomers and higher stoichiometries were easily imaged, enabling us to detect formation of oligomeric species induced by ligand binding. The presence of ATP:Mg(2+) particularly induced the appearance of the hexameric assembly whose mean molecular volume resembles the crystallographic dimer of trimers. Finally, the AFM results are confirmed in cross-linking solution, and the presence of such oligomeric CaFADS species detected in cell extracts. All these results are consistent with the formation of a dimer of trimers during the enzyme catalytic cycle that might bear biological relevance.
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Affiliation(s)
- Carlos Marcuello
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Spain
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Burnstock G, Kennedy C. P2X receptors in health and disease. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 61:333-372. [PMID: 21586364 DOI: 10.1016/b978-0-12-385526-8.00011-4] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Seven P2X receptor subunits have been cloned which form functional homo- and heterotrimers. These are cation-selective channels, equally permeable to Na(+) and K(+) and with significant Ca(2+) permeability. The three-dimensional structure of the P2X receptor is described. The channel pore is formed by the α-helical transmembrane spanning region 2 of each subunit. When ATP binds to a P2X receptor, the pore opens within milliseconds, allowing the cations to flow. P2X receptors are expressed on both central and peripheral neurons, where they are involved in neuromuscular and synaptic neurotransmission and neuromodulation. They are also expressed in most types of nonneuronal cells and mediate a wide range of actions, such as contraction of smooth muscle, secretion, and immunomodulation. Changes in the expression of P2X receptors have been characterized in many pathological conditions of the cardiovascular, gastrointestinal, respiratory, and urinogenital systems and in the brain and special senses. The therapeutic potential of P2X receptor agonists and antagonists is currently being investigated in a range of disorders, including chronic neuropathic and inflammatory pain, depression, cystic fibrosis, dry eye, irritable bowel syndrome, interstitial cystitis, dysfunctional urinary bladder, and cancer.
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Affiliation(s)
- G Burnstock
- Autonomic Neuroscience Centre, University College Medical School, London, United Kingdom
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Carnally SM, Edwardson JM, Barrera NP. Imaging the spatial orientation of subunits within membrane receptors by atomic force microscopy. Methods Mol Biol 2011; 736:47-60. [PMID: 21660720 DOI: 10.1007/978-1-61779-105-5_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Our experimental approach is based on the atomic force microscope (AFM) imaging of epitope-tagged subunits within membrane protein complexes purified in small amounts and decorated by anti-tag antibodies. Furthermore, we can produce simultaneous decoration of protein complexes using Fab fragments and IgG antibodies, which, combined with chemical modification of the substrate, allows us to determine the protein orientation across the cell membrane. Here, we describe a detailed protocol for membrane protein purification, AFM data collection, analysis, and interpretation of results. The protocol also covers basic AFM instrument settings and best practices for both observation of membrane protein complexes by AFM and automatic detection of the structures by an in-house algorithm. Once a sufficient number of membrane protein complexes have been visualized by AFM, data acquisition and processing can be completed in approximately 10 min using a scanning surface of 1 μm(2).
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Affiliation(s)
- Stewart M Carnally
- Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
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Benesch JLP, Ruotolo BT, Simmons DA, Barrera NP, Morgner N, Wang L, Saibil HR, Robinson CV. Separating and visualising protein assemblies by means of preparative mass spectrometry and microscopy. J Struct Biol 2010; 172:161-8. [PMID: 20227505 DOI: 10.1016/j.jsb.2010.03.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
Abstract
Many multi-protein assemblies exhibit characteristics which hamper their structural and dynamical characterization. These impediments include low copy number, heterogeneity, polydispersity, hydrophobicity, and intrinsic disorder. It is becoming increasingly apparent that both novel and hybrid structural biology approaches need to be developed to tackle the most challenging targets. Nanoelectrospray mass spectrometry has matured over the last decade to enable the elucidation of connectivity and composition of large protein assemblies. Moreover, comparing mass spectrometry data with transmission electron microscopy images has enabled the mapping of subunits within topological models. Here we describe a preparative form of mass spectrometry designed to isolate specific protein complexes from within a heterogeneous ensemble, and to 'soft-land' these target complexes for ex situ imaging. By building a retractable probe incorporating a versatile target holder, and modifying the ion optics of a commercial mass spectrometer, we show that we can steer the macromolecular ion beam onto a target for imaging by means of transmission electron microscopy and atomic force microscopy. Our data for the tetradecameric chaperonin GroEL show that not only are the molecular volumes of the landed particles consistent with the overall dimensions of the complex, but also that their gross topological features can be maintained.
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Affiliation(s)
- Justin L P Benesch
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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Carnally SM, Johannessen M, Henderson RM, Jackson MB, Edwardson JM. Demonstration of a direct interaction between sigma-1 receptors and acid-sensing ion channels. Biophys J 2010; 98:1182-91. [PMID: 20371317 PMCID: PMC2849097 DOI: 10.1016/j.bpj.2009.12.4293] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/08/2009] [Accepted: 12/15/2009] [Indexed: 10/19/2022] Open
Abstract
The sigma-1 receptor is a widely expressed protein that interacts with a variety of ion channels, including the acid-sensing ion channel (ASIC) 1a. Here we used atomic force microscopy to determine the architecture of the ASIC1a/sigma-1 receptor complex. When isolated His(8)-tagged ASIC1a was imaged in complex with anti-His(6) antibodies, the angle between pairs of bound antibodies was 135 degrees , consistent with the known trimeric structure of the channel. When ASIC1a was coexpressed with FLAG/His(6)-tagged sigma-1 receptor, ASIC1a became decorated with small particles, and pairs of these particles bound at an angle of 131 degrees . When these complexes were incubated with anti-FLAG antibodies, pairs of antibodies bound at an angle of 134 degrees , confirming that the small particles were sigma-1 receptors. Of interest, we found that the sigma-1 receptor ligand haloperidol caused an approximately 50% reduction in ASIC1a/sigma-receptor binding, suggesting a way in which sigma-1 ligands might modulate channel properties. For the first time, to our knowledge, we have resolved the structure of a complex between the sigma-1 receptor and a target ion channel, and demonstrated that the stoichiometry of the interaction is 1 sigma-1 receptor/1 ASIC1a subunit.
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Affiliation(s)
- Stewart M. Carnally
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Molly Johannessen
- Department of Physiology, University of Wisconsin, Madison, Wisconsin
| | - Robert M. Henderson
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Meyer B. Jackson
- Department of Physiology, University of Wisconsin, Madison, Wisconsin
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Intermittent contact mode AFM investigation of native plasma membrane of Xenopus laevis oocyte. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:903-10. [PMID: 19458948 DOI: 10.1007/s00249-009-0464-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/12/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
Abstract
Intermittent contact mode atomic force microscopy (AFM) was used to visualize the native plasma membrane of Xenopus laevis oocytes. Oocyte membranes were purified via ultracentrifugation on a sucrose gradient and adsorbed on mica leaves. AFM topographs and the corresponding phase images allowed for visualization and identification of both oocyte plasma membrane patches and pure lipid bilayer regions with a height of about 5 nm within membrane patches. The quantitative analysis showed a normal distribution for the lateral dimension and height of the protein complexes centered on 16.7 +/- 0.2 nm (mean +/- SE, n = 263) and 5.4 +/- 0.1 nm (n = 262), respectively. The phase signal, providing material-dependent information, allowed for the recognition of structural features observed in AFM topographs.
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Direct visualization of the trimeric structure of the ASIC1a channel, using AFM imaging. Biochem Biophys Res Commun 2008; 372:752-5. [PMID: 18514062 DOI: 10.1016/j.bbrc.2008.05.100] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Accepted: 05/20/2008] [Indexed: 01/25/2023]
Abstract
There has been confusion about the subunit stoichiometry of the degenerin family of ion channels. Recently, a crystal structure of acid-sensing ion channel (ASIC) 1a revealed that it assembles as a trimer. Here, we used atomic force microscopy (AFM) to image unprocessed ASIC1a bound to mica. We detected a mixture of subunit monomers, dimers and trimers. In some cases, triple-subunit clusters were clearly visible, confirming the trimeric structure of the channel, and indicating that the trimer sometimes disaggregated after adhesion to the mica surface. This AFM-based technique will now enable us to determine the subunit arrangement within heteromeric ASICs.
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Determination of the architecture of ionotropic receptors using AFM imaging. Pflugers Arch 2007; 456:199-209. [PMID: 18026748 DOI: 10.1007/s00424-007-0381-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 10/26/2007] [Indexed: 10/22/2022]
Abstract
Fast neurotransmission in the nervous system is mediated by ionotropic receptors, all of which contain several subunits surrounding an integral ion channel. There are three major families of ionotropic receptors: the 'Cys-loop' receptors (including the nicotinic receptor for acetylcholine, the 5-HT(3) receptor, the GABA(A) receptor and the glycine receptor), the glutamate receptors (including the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, kainate and N-methyl-D: -aspartic acid receptors) and the P2X receptors for adenosine triphosphate. These receptors are often built from multiple types of subunit, raising the question of the stoichiometry and subunit arrangement within the receptors. This question is of therapeutic significance because in some cases drug-binding sites are located at subunit-subunit interfaces. In this paper, we describe a general method, based on atomic force microscopy imaging, to solve the architecture of multi-subunit proteins, such as the ionotropic receptors. Specific epitope tags are engineered onto each receptor subunit. The subunits are then expressed exogenously in cultured cells, and the receptors are isolated from detergent extracts of membrane fractions by affinity chromatography. The receptors are imaged both alone and in complex with anti-epitope antibodies. The size of the imaged particles provides an estimate of the subunit stoichiometry, whereas the geometry of the receptor-antibody complexes produces more detailed information about the receptor architecture. We use an automated, unbiased system to identify receptors and receptor-antibody complexes and to determine the geometry of the complexes. We are also able to determine the orientation of the receptors on the mica substrate, which will allow us to solve the subunit arrangement within receptors, such as the GABA(A) receptor, which contain three types of subunits.
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