Photoaffinity labelling and phosphorylation of a 165 kilodalton peptide associated with dihydropyridine and phenylalkylamine-sensitive calcium channels

Partially purified fractions of dihydropyridine and phenylalkylamine receptors associated with voltage-dependent calcium channels in rabbit skeletal muscle were found to contain two glycopeptides of similar molecular weight. A peptide of approximately 165 kDa was photoaffinity labelled with an arylazido-phenylalkylamine Ca channel inhibitor and also was phosphorylated with cAMP-dependent protein kinase. Another peptide of 170 kDa could be distinguished from the 165 kDa peptide by peptide mapping and differences in electrophoretic mobility. The results suggest that the 165 kDa peptide contains the sites responsible for regulation of calcium channel activity by calcium channel inhibitors as well as by neurotransmitters that regulate its activity in a cAMP-dependent manner.