Single-channel activity of L-type Ca2+ channels reconstituted with the beta2c subunit cloned from the rat heart.

We recently cloned the beta(2c) subunit of the L-type Ca(2+) channel as a functional type of beta subunit from the rat heart. In order to clarify the contribution of the beta(2c) subunit to native Ca(2+) channel function, we investigated the single-channel properties of Ca(2+) channels reconstituted with beta(2a) or beta(2c) subunits and compared them with the properties of native channels. In contrast to the Ca(2+) channel with beta(2a) subunit, long-lasting closings were dominant in the Ca(2+) channel with beta(2c) subunit and the native channel. The ensemble-averaged current of the cells with beta(2c) subunits was comparable to that of the native cardiomyocytes. Many high P(o) sweeps (mode 2) were observed in the cells with beta(2a) subunits, while only a few high P(o) sweeps were observed in the cells with beta(2c) subunits and the native cells. These findings suggest that the beta(2c) subunit is one of the functional beta subunits in the rat heart.