Endogenous and exogenous proteolysis of the acetylcholine receptor from torpedo californica

Purified acetylcholine receptor reconstituted into liposomes catalyzes carbamylcholine-dependent ion flux 10]. An endogenous protease activated by Ca²⁺ gives rise to an acrylamide gel pattern of the receptor with the 40,000-dalton subunit apparently as the major component. Exogenous proteases nick the proteins so extensively that the acrylamide gel pattern reveals polypeptides of 20,000 daltons or less. In either case the receptor sediments at 9S, indicating that the polypeptide chains associated. Moreover, the nicked receptors bind α-bungarotoxin and catalyze carbamylcholine-dependent ion flux after reconstitution.