期刊
ACS CHEMICAL BIOLOGY
卷 12, 期 3, 页码 805-813出版社
AMER CHEMICAL SOC
DOI: 10.1021/acschembio.6b00926
关键词
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资金
- Australian Research Council [DP130101702]
- National Health and Medical Research Council [APP1058542]
- University of Queensland Graduate School International Travel Award
The efficacy of an agonist at a pentameric ligand-gated ion channel is determined by the rate at which it induces a conformational change from the resting closed state to a preopen (flip) state. If the ability of an agonist to promote this isomerization is sufficiently low, then it becomes a partial agonist. As partial agonists at pentameric ligand-gated ion channels show considerable promise as therapeutics, understanding the structural basis of the resting-flip-state isomerization may provide insight into therapeutic design. Accordingly, we sought to identify structural correlates of the resting-flip conformational change in the, glycine receptor chloride channel. We used nonsense suppression to introduce the small, fluorescent amino acid, 3-(6-acetylnaphthalen-2-ylamino)-2-aminopropanoic acid (ANAP), into specific sites in the extracellular and transmembrane domains. Then, under voltage-clamp conditions in Xenopus oocytes, we simultaneously quantified current and fluorescence responses induced by structurally similar agonists with high, medium, and low efficacies (glycine, beta-alanine, and taurine, respectively). Analyzing results from nine ANAP-incorporated sites, we show that glycine receptor activation by agonists with graded efficacies manifests structurally as correspondingly graded movements of the beta 1-beta 2 loop, the beta 8-beta 9 loop, and the Cys-loop from the extracellular domain and the TM2-TM3 linker in the transmembrane domain. We infer that the resting-flip transition involves an efficacy-dependent molecular reorganization at the extracellular-transmembrane domain interface that primes receptors for efficacious opening.
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