Identification and functional characterization of a calcium channel γ subunit

Abstract

 A positive selection technique was used to identify novel auxiliary calcium channel subunits that are similar to the skeletal muscle γ subunit. A new rat γ subunit cDNA was found, which was highly expressed in skeletal muscle tissue and was detected by RT-PCR in cardiac tissue. The 223-amino-acid-protein shares 84% and 79% identity, respectively, with the human and rabbit skeletal muscle subunits. Northern blot analysis revealed a single transcript of 1.5 kb in rat skeletal muscle, but not in cardiac tissue. Transient coexpression with the cardiac calcium channel complex demonstrated that the γ subunit shifted the inactivation curve to negative potentials and accelerated current inactivation without changing other voltage-dependent properties of the channel.