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Enhanced meta-analysis of acetylcholine binding protein structures reveals conformational signatures of agonism in nicotinic receptors
Journal article   Open access   Peer reviewed

Enhanced meta-analysis of acetylcholine binding protein structures reveals conformational signatures of agonism in nicotinic receptors

Spencer T Stober and Cameron F Abrams
Protein science, v 21(3), pp 307-317
Mar 2012
PMID: 22170867
url
https://doi.org/10.1002/pro.2016View
Published, Version of Record (VoR) Open

Abstract

Amino Acid Sequence Models, Molecular Molecular Sequence Data Crystallography, X-Ray Molecular Dynamics Simulation Nicotinic Agonists - chemistry Aplysia Carrier Proteins - genetics Sequence Alignment Animals Receptors, Nicotinic - chemistry Carrier Proteins - chemistry Ligands Protein Conformation
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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Biochemistry & Molecular Biology
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