Atropine dissociates complexes of muscarinic acetylcholine receptor and guanine nucleotide‐binding protein in heart membranes

Abstract

Complexes of muscarinic acetylcholine receptor and guanine nucleotide-binding protein (G protein) are formed in the presence of the agonist carbachol. The complexes remain stable after removal of agonist, and survive subsequent solubilization from cardiac membranes and purification. Dissociation of the receptor from the G protein occurs when the antagonist atropine is added following removal of agonist. This is the first direct demonstration of destabilization of receptor—G protein complexes by the binding of an antagonist.