Ca2+ channel regulation by a conserved beta subunit domain.

The beta subunit is a cytoplasmic component that normalizes the current amplitude, kinetics, and voltage dependence of voltage-gated Ca2+ channels. Here, we identify a 30 amino acid domain of the beta subunit that is sufficient to induce a stimulation and shift in the voltage dependence of activation of the Ca2+ channel currents. This domain is located at the amino terminus of the second region of high conservation among all beta subunit gene products. Single point mutations within this region on the beta 1b subunit modified or abolished the stimulation of Ca2+ channel currents and the binding of the beta subunit to the alpha 1A subunit. The binding of this domain is also required for the observed changes in kinetics and voltage dependence of steady-state inactivation induced by beta subunits.