A RAPID PROCEDURE FOR THE PURIFICATION OF CARDIAC 1,4-DIHYDROPYRIDINE RECEPTORS FROM PORCINE HEART

Highly purified porcine cardiac sarcolemma was used as a source for purification of mammalian cardiac 1,4-dihydropyridine receptors associated with the voltage-dependent Ca2+ channel. The cardiac digitonin-solubilized receptor prelabeled with (+)-[H-3]PN 200-110 was enriched at least 236-fold using an improved, rapid three-step purification protocol which could be completed within 12 h. The purity of the preparations was at least 22%, the yield of the receptors 24%. Photoaffinity labeling experiments with (-)-[H-3]azidopine allowed the identification of the cardiac alpha-1 subunit. In contrast to the purified rabbit or guinea-pig skeletal muscle Ca2+ channel complex, none of the purified polypeptides underwent rapid and substantial phosphorylation by the catalytic subunit of the cyclic AMP-dependent protein kinase in vitro.