期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：11
页码：5051-5055
DOI：10.1073/pnas.88.11.5051
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Structural changes occurring upon desensitization of the Torpedo marmorata acetylcholine receptor were monitored with tritiated p-(N,N-dimethyl)aminobenzenediazonium fluoroborate, a reversible competitive antagonist in the dark, which may serve as a photoaffinity probe of the area of the receptor molecule with which cholinergic ligands interact. Addition of meproadifen, an allosteric effector that stabilizes the high-affinity desensitized state of the receptor upon binding to a site topographically distinct from the cholinergic ligand-binding domains, caused a major increase in labeling of the alpha subunit, a smaller increase in the delta subunit, and decreased labeling in the gamma subunit, thus revealing changes in the alpha and non-alpha subunits' contribution to cholinergic ligand binding. Also, in agreement with the tighter binding of cholinergic ligands to the desensitized receptor, differential labeling of three peptide loops of the alpha subunit was detected: while Tyr-190, Cys-192, and Cys-193 were labeled in a roughly identical manner in both resting and desensitized conformations, the labeling of Tyr-93 and Trp-149 increased up to 6-fold in the desensitized state. Tyr-93 and Trp-149 belong to separate regions containing strictly conserved "canonical" amino acids, common to all nicotinic, gamma-aminobutyrate, and glycine receptor subunits. These regions are thus likely to play a critical role in the regulation of ligand-gated ion channels.
