Complementary DNAs were isolated and used to deduce the primary structures of the α1, and α2 subunits of the dihydropyridine-sensitive, voltage-dependent calcium channel from rabbit skeletal muscle. The α1 subunit, which contains putative binding sites for calcium antagonists, is a hydrophobic protein with a sequence that is consistent with multiple transmembrane domains and shows structural and sequence homology with other voltage-dependent ion channels. In contrast, the α2 subunit is a hydrophilic protein without homology to other known protein sequences. Nucleic acid hybridization studies suggest that the α1 and α2 subunit mRNAs are expressed differentially in a tissue-specific manner and that there is a family of genes encoding additional calcium channel subtypes.
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