The cardiac dihydropyridine-sensitive L-type calcium channel was stably expressed in Chinese hamster ovary cells by transfecting the rabbit cardiac calcium channel α1 subunit cDNA with or without coexpression of the β subunit of skeletal muscle calcium channel. Whereas coexpression of the β subunit significantly increased DHP binding activity and calcium channel activity, it did not affect the amount of the α1 subunit expressed, as judged by RNA blot hybridization analysis and immunoblotting analysis. The results suggest that association with the β subunit is necessary for the α1 subunit protein to take a proper conformation suitable for a functional calcium channel.
