Autoinhibition of acetylcholine binding to Torpedo electroplax; a possible molecular mechanism for desensitization.

Binding of [(3)H]acetylcholine (measured by equilibrium dialysis) to a particulate preparation of Torpedo electroplax exhibits autoinhibition at concentrations higher than 1 muM. It is suggested that autoinhibition results from acetylcholine binding to regulatory sites on its receptor macromolecules. This binding causes the change to a new and inactive conformation and rejection of acetylcholine bound to the larger number of active sites. The relationship to the physiological phenomenon of desensitization is discussed.