Isolation and characteristics of dihydropyridine calcium antagonist receptor from rabbit skeletal muscles

Up to 80% of the dihydropyridine receptor is solubilized from transverse tubules of rabbit skeletal muscle by 3-[(3-cholamidopropyl)-dimethylammonium]-2-oxy-1-propane sulfonate (CHAPSO). The DHP receptor is an oligomeric complex made up of two subunits with molecular masses of 160 and 53 kD as shown by DHP-Sepharose affinity chromatography and SDS gel electrophoresis of specifically eluted proteins. The reduction of disulfide bridges of the 160 kD subunit is accompanied by a decrease in its apparent molecular mass up to 125 kD. A method is proposed for preparative isolation of the DHP receptor which is based on ion-exchange chromatography and WGA-Sepharose chromatography. Individual subunits of DHP receptor were isolated by Sepharose 4B gel filtration in SDS; their amino acid composition was determined. Both the 160 and 53 kD subunits are N-glycosylated, and the oligosaccharide portions make up to 7.5% and 6.6%, respectively.