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Stober ST, Abrams CF. Enhanced meta-analysis of acetylcholine binding protein structures reveals conformational signatures of agonism in nicotinic receptors. Protein Sci 2012; 21:307-17. [PMID: 22170867 DOI: 10.1002/pro.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The soluble acetylcholine binding protein (AChBP) is the default structural proxy for pentameric ligand-gated ion channels (LGICs). Unfortunately, it is difficult to recognize conformational signatures of LGIC agonism and antagonism within the large set of AChBP crystal structures in both apo and ligand-bound states, primarily because AChBP conformations in this set are nearly superimposable (root mean square deviation < 1.5 Å). We have undertaken a systematic, alignment-free approach to elucidate conformational differences displayed by AChBP that cleanly differentiate apo/antagonist-bound from agonist-bound states. Our approach uses statistical inference based on both crystallographic states and conformations sampled during long molecular dynamics simulations to select important inter-C(α) distances and map their collective values onto functional states. We observe that binding of (nAChR) agonists to AChBP elicits clockwise rotation of the inner β-sheet with respect to the outer β-sheet, causing tilting of the cys-loop away from the five-fold axis, in a manner quite similar to that speculated for α-subunits of the heteromeric nAChR structure (Unwin, J Mol Biol 2005;346:967), making this motion potentially important in transmission of the gating signal to the transmembrane domain of a LGIC. The method is also successful at discriminating partial from full agonists and supports the hypothesis that a particularly controversial ligand, lobeline, is in fact an LGIC antagonist.
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Affiliation(s)
- Spencer T Stober
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA
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de Kloe GE, Retra K, Geitmann M, Källblad P, Nahar T, van Elk R, Smit AB, van Muijlwijk-Koezen JE, Leurs R, Irth H, Danielson UH, de Esch IJP. Surface Plasmon Resonance Biosensor Based Fragment Screening Using Acetylcholine Binding Protein Identifies Ligand Efficiency Hot Spots (LE Hot Spots) by Deconstruction of Nicotinic Acetylcholine Receptor α7 Ligands. J Med Chem 2010; 53:7192-201. [DOI: 10.1021/jm100834y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gerdien E. de Kloe
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Kim Retra
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of BioMolecular Analysis, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | | | | | - Tariq Nahar
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - René van Elk
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Jacqueline E. van Muijlwijk-Koezen
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Rob Leurs
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Hubertus Irth
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of BioMolecular Analysis, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - U. Helena Danielson
- Beactica AB, Box 567, SE-751 22 Uppsala, Sweden
- Department of Biochemistry and Organic Chemistry, Uppsala University, BMC, Box 576, SE-751 23, Uppsala, Sweden
| | - Iwan J. P. de Esch
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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Williams CA, Bell SV, Jenkins A. A residue in loop 9 of the beta2-subunit stabilizes the closed state of the GABAA receptor. J Biol Chem 2009; 285:7281-7. [PMID: 20007704 DOI: 10.1074/jbc.m109.050294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In gamma-aminobutyric acid type A (GABA(A)) receptors, the structural elements that couple ligand binding to channel opening remain poorly defined. Here, site-directed mutagenesis was used to determine if Loop 9 on the non-GABA binding site interface of the beta2-subunit may be involved in GABA(A) receptor activation. Specifically, residues Gly(170)-Gln(185) of the beta2-subunit were mutated to alanine, co-expressed with wild-type alpha1- and gamma2S-subunits in human embryonic kidney (HEK) 293 cells and assayed for their activation by GABA, the intravenous anesthetic propofol and the endogenous neurosteroid pregnanolone using whole cell macroscopic recordings. Three mutants, G170A, V175A, and G177A, produced 2.5-, 6.7-, and 5.6-fold increases in GABA EC(50) whereas one mutant, Q185A, produced a 5.2-fold decrease in GABA EC(50). None of the mutations affected the ability of propofol or pregnanolone to potentiate a submaximal GABA response, but the Q185A mutant exhibited 8.3- and 3.5-fold increases in the percent direct activation by propofol and pregnanolone, respectively. Mutant Q185A receptors also had an increased leak current that was sensitive to picrotoxin, indicating an increased gating efficiency. Further Q185E, Q185L, and Q185W substitutions revealed a strong correlation between the hydropathy of the amino acid at this position and the GABA EC(50). Taken together, these results indicate that beta2 Loop 9 is involved in receptor activation by GABA, propofol, and pregnanolone and that beta2(Q185) participates in hydrophilic interactions that are important for stabilizing the closed state of the GABA(A) receptor.
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Affiliation(s)
- Carrie A Williams
- Department of Anesthesiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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