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