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 Ca 2+ channel. The cardiac digitonin-solubilized receptor prelabeled with (+)-[ 3H]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 preparation was at least 22%, the yield of the receptors 24%. Photoaffinity labeling experiments with (−)-[ 3H]azidopine allowed the identification of the cardiac α 1 subunit. In contrast to the purified rabbit or guinea-pig skeletal muscle Ca 2+ 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.