TABLE 1

Voltage-dependent gating parameters (V½ ± S.E.M.) for activation and inactivation of Cav2.1 Ca2+ channels resulting from increasing concentrations of either β4a or β4b splice variant

The β-subunit concentrations are expressed as molar ratios relative to α1 and α2δ subunits (α1:α2δ:β). R300 is the percentage of current remaining relative to peak values at the end of a 300-ms stimulus.

nV½ Activation R300 nV½ Inactivation
mV % mV
α1α2δ 12 1.9 ± 0.8 30.4 ± 2.0 10 −18.1 ± 2.6
+ β4a
1:1:0.3 8 −4.5 ± 0.6 33.4 ± 1.4 8 −27.8 ± 2.3
1:1:1 9 −8.8 ± 1.0 34.4 ± 3.2 8 −36.3 ± 0.6
1:1:3 11 −13.5 ± 0.7 45.9 ± 1.4 10 −41.7 ± 0.7
1:1:10 10 −15.8 ± 0.7 55.4 ± 2.2 9 −42.0 ± 0.3
+ β4b
1:1:0.3 9 −6.0 ± 0.7 28.9 ± 2.4 8 −28.2 ± 0.9
1:1:1 11 −11.8 ± 0.8 48.8 ± 2.6 10 −38.3 ± 0.5
1:1:3 13 −15.0 ± 0.4 52.6 ± 3.2 12 −42.6 ± 0.8
1:1:10 10 −14.9 ± 0.6 55.0 ± 3.1 9 −43.6 ± 0.8