Jon Lindstrom,* John Merlie, 5 and Ganesa Yogeeswaran abstract: Four polypeptide chains composing acetylcholine receptors from the electric organ of Torpedo californica were purified by preparative electrophoresis in sodium dodecyl sulfate. Their apparent mole ratio a/(3/y/6 is 2: 1: 1: 1. These chains are not readily distinguished by amino acid or car-.^^. cetylcholine receptor (AcChR) 1 solubilized from the electric organ of Torpedo californica by Triton X-100 and purified by affinity chromatography is composed of four polypeptide chains termed a, 8, 7, and 8. The apparent molecular weights of these chains depend on the electrophoresis system and standards employed but approximate 38 000, 50000, 57 000, and 64000 for a, 8, 7, and 8, respectively (Weill et al., 1974; Raftery et al., 1975; Hucho et al., 1978; f From the Salk Institute for Biological Studies, San Diego, California