REQUIREMENT OF THE CALCIUM-CHANNEL BETA-SUBUNIT FOR FUNCTIONAL CONFORMATION

The cardiac dihydropyridine-sensitive L-type calcium channel was stably expressed in Chinese hamster ovary cells by transfecting the rabbit cardiac calcium channel alpha1 subunit cDNA with or without coexpression of the beta subunit of skeletal muscle calcium channel. Whereas coexpression of the beta subunit significantly increased DHP binding activity and calcium channel activity, it did not affect the amount of the alpha1 subunit expressed, as judged by RNA blot hybridization analysis and immunoblotting analysis. The results suggest that association with the beta subunit is necessary for the alpha1 subunit protein to take a proper conformation suitable for a functional calcium channel.