| Abstract: | Acetylcholine receptor (AcChR) was solubilized and purified from membranes derived from electric organs of the marine fish Torpedo marmorata, Torpedo nobiliana, Narcine brasliensis, and of the freshwater eel, Electrophorus electricus, using techniques originally developed for Torpedo californica (27., 28.Biochem. Biophys. Res. Commun.49, 572–578; 1973, Biochemistry12, 852–856. The conditions used were identical in each case and the goal was to determine the degree of similarity between receptors from each source since conflicting reports have appeared with regard to polypeptide composition. The Torpedo and Narcine preparations were of high specific activity and exhibited four polypeptide components of apparent molecular weights 64, 59, 50, and 40 × 103 upon polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Two components were observed upon gel electrophoresis in sodium cholate or upon sucrose density gradient centrifugation, representing monomeric and dimeric forms. Eel acetylcholine receptor exhibited three major subunits of apparent molecular weights 57, 49, and 40 × 103. The amino acid and neutral sugar composition of the purified receptor preparations have been determined. The results support the contention that the receptor is composed of several types of polypeptide. |
