SINGLE-CHANNEL ANALYSIS OF A CLONED HUMAN HEART L-TYPE CA2+ CHANNEL ALPHA(1)-SUBUNIT AND THE EFFECTS OF A CARDIAC BETA-SUBUNIT

Macroscopic and single-channel properties of a cloned human heart L-type Ca2+ channel α1 subunit expressed in Xenopus oocytes were studied and the effects of a cardiac β subunit were evaluated. The α1 subunit expressed current with much slower activation and inactivation kinetics than native cells. The β subunit increased the current amplitude and accelerated both activation and inactivation rates. Single-channel analysis revealed that the β subunit increased the probability of channel opening and shifted the voltage-dependence to more negative potentials without affecting conductance or open time. The data suggest that the β subunit modulates macroscopic current by increasing the probability of channel opening and shifting the voltage-dependence of the channel. © 1993 Academic Press. All rights reserved.