The calcium channel antagonists receptor from rabbit skeletal muscle

Publisher Website
Google Scholar
Abstract
The Ca2+ channel antagonists receptor from rabbit skeletal muscle was purified to homogeneity. Following reconstitution into phosphatidylcholine vesicles, binding experiments with (+)[3H]PN 200–110, (−)[3H]D888 and d‐cis‐[3H]diltiazem demonstrated that receptor sites for the three most common Ca2+ channel markers copurified with binding stoichiometries close to 1:1:1.Sodium dodecyl sulfate gel analysis of the purified receptor showed that it is composed of only one protein of Mr 170000 under non‐reducing conditions and of two polypeptides of Mr 140000 and 32000 under disulfide‐reducing conditions. Iodination of the protein of Mr 170000 and immunoblots experiments with antisera directed against the differents components demonstrated that the Ca2+ channel antagonists receptor is a complex of Mr 170000 composed of a polypeptide chain of Mr 140000 associated to one polypeptide chain of Mr 32000 by disulfide bridges. One of the problems concerning this subunit structure of the putative Ca2+ channel was the presence of smaller polypeptide chains of Mr 29000 and 25000. Peptide mapping of these polypeptide chains and analysis of their cross‐reactivity with sera directed against the proteins of Mr 170000 and 32000 demonstrated that they were degradative products of the Mr 32000 component.Both the large (140 kDa) and the small (32 kDa) component of the putative Ca2+ channel are heavily glycosylated. At least 20–22% of their mass were removed by enzymatic deglycosylation. Finally the possibility that both the 140‐kDa and 32‐kDa components originate from a single polypeptide chain of Mr 170000 which is cleaved by a proteolysis upon purification is discussed.

This publication has 32 references indexed in Scilit: