Molecular characterization of 1,4-dihydropyridine-sensitive calcium channels of chick heart and skeletal muscle.
A monoclonal antibody designated as MAC-L1 immunoprecipitated [3H]PN200-110-labeled calcium channels of chick cardiac and skeletal muscle. On specific immunoprecipitation of 125I-labeled proteins, two large polypeptides (Mr 197,000 and 139,000 for heart, and 172,000 and 135,000 for skeletal muscle, under reducing conditions) were identified as the major components of these channels. Both polypeptides were found to exist together as a complex in 1% digitonin, but to become separated from each other in 1% Triton X-100. The 197 and 172 kDa peptides of cardiac and skeletal muscles, respectively, were photolabeled with [3H]azidopine. Under nonreducing conditions, the 139 kDa polypeptide of heart and the 135 kDa polypeptide of skeletal muscle took on larger molecular weights of 192,000 and 190,000, respectively. The 139 kDa but not the 197 kDa component of the heart was capable of binding to wheat germ agglutinin-Sepharose. Among the polypeptides specifically precipitated by MAC-L1, a 165 kDa peptide of skeletal muscle was phosphorylated by cAMP-dependent protein kinase. In contrast, a minor 99 kDa polypeptide, but not the major 197 kDa polypeptide, of the heart was phosphorylated by this kinase. These results suggest that the dihydropyridine-sensitive cardiac calcium channel has alpha 1 and alpha 2 subunits that are homologous but not identical to those of the skeletal muscle calcium channel.
Yoshida
A
A
Department of Biology, Faculty of Science, Osaka University.
Takahashi
M
M
Fujimoto
Y
Y
Takisawa
H
H
Nakamura
T
T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000032:analysis; D015220:Calcium Channels / Q000032:analysis* / Q000187:drug effects / Q000276:immunology; D002645:Chickens; D003429:Cross Reactions; D004095:Dihydropyridines / Q000494:pharmacology*; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D009206:Myocardium / Q000032:analysis* / Q000276:immunology; D010766:Phosphorylation; D011233:Precipitin Tests; D011487:Protein Conformation
D000911:Antibodies, Monoclonal; D000941:Antigens; D015220:Calcium Channels; D004095:Dihydropyridines; C038806:1,4-dihydropyridine