Single-channel study of the binding–gating coupling in the slowly desensitizing chimeric α7-5HT3A receptor

We have studied the role of the highly conserved residue αLysine145 in the early steps of activation by acetylcholine of the nicotinic acetylcholine receptor (nAChR). Both macroscopic and single-channel currents were recorded in the slowly desensitizing chimeric mutant receptor α7V201-5HT3A/R432Q/R436D/R440A, made of α7 nAChRs and serotonin receptors of subtype 3A (ch1), and its corresponding mutant K145A (ch1/K145A) expressed in Xenopus oocytes. Mutant ch1/K145A receptors had a reduced gating function similar to that produced by the same mutation in the wild type receptor α7. The mutated receptor has reduced opening rate constants, β, and increased closing rate constants, α.