An ESR study of the postsynatpic membrane acetylcholinesterase of Torpedo marmorata electric organ.

The effect of the cholinergic activator, phenyltrimethylammonium, on the ESR spectra of spin-labeled membrane bound acetylcholinesterase was studied; a reduction of maximal hyperfine splitting of the anisotropic ESR spectrum by 2 G was observed. The influence of phenyltrimethylammonium was prevented by the two cholinergic blocking agents d-tubocurarine and alpha-cobratoxine. The present results indicate that the conformation change of the esteratic site of membrane acetylcholinesterase is triggered by the binding of phenyltrimethylammonium to the cholinoreceptor site.