Complete purification of the acetylcholine receptor protein from mammalian muscle

Abstract

The receptor (ACh.R) for acetylcholine (ACh) has so far been obtained in apparently pure form only from fish electric organs (for reviews, see [ 1,2] ). From vertebrate skeletal muscle, on the other hand, where ACh.R is essential for synaptic transmission and for denervation supersensitivity to ACh, no extensive purification has been reported. Muscle is a much poorer source of ACh.R, and even after its proliferation following denervation it is far below the level in the electric organ of Torpedo. For muscles, quantitation and localisation of ACh.R, by exploitation of its essentially irreversible binding of labelled cu-bungarotoxin (BuTX), was initially described [3], and solubilisation of this ACh.R in detergents and some fractionation has been reported [4-71. Subsequently [S] , we reported upon a preparation, partly purified by affinity chromatography, of the form of ACh.R which is responsible for the extrajunctional ACh sensitivity of denervated mammalian muscle. We have further applied affinity chromatography in a more bio-specific form (in the sense in which this technique has been critically reviewed by Barry and O’Carra [9] ), and describe here the complete purification of this muscle ACh.R.