TABLE 3.
Biophysical properties of E462R mutants with CaVβ2a wt and CS
| Inactivation (5 s) E0.5 (mV)
|
Activation E0.5 (mV)
|
Peak IBa (μA)
|
||||
|---|---|---|---|---|---|---|
| With α2bδ in 10 Ba2+ | +β2a | +β2aCS | +β2a | +β2aCS | +β2a | +β2aCS |
| CEEE | −18 ± 1 (5) z = 2.3 | n.d. | −4.6 ± 0.7 (2) z = 4.6 ± 0.3 | −5.1 ± 0.6 (6) z = 3.8 ± 0.1 | −0.51 ± 0.03 (2) | −0.66 ± 0.06 (6) |
| CEEE + E462R | −27.3 ± 0.5 mV (12) z = 2.5 | −33.6 ± 0.7 mV (6) z = 2.6 | −9.0 ± 0.4 (9) z = 5.0 ± 0.3 | −5.7 ± .5 (14) z = 4.0 ± 0.2 | −4.6 ± 0.9 (9) | −1.6 ± 0.2 (14) |
| CaV1.2 (XhoI) wt | n.d. | n.d. | −8.8 ± 0.6 (8) z = 3.9 ± 0.3 | −5.9 ± 0.7 (4) z = 3.7 ± 0.2 | −0.8 ± 0.1 (8) | −0.58 ± 0.05 (4) |
| CaV1.2 E462R | n.d. | n.d. | −11 ± 1 (8) z = 4.2 ± 0.3 | −7.7 ± 0.9 (7) z = 4.9 ± 0.6 | −0.9 ± 0.2 (8) | −0.63 ± 0.08 (7) |
Biophysical parameters of CaV1.2 and CEEE mutants expressed in Xenopus oocytes in the presence of CaVα2bδ and CaVβ2a or CaVβ2a C3S + C4S subunits. Whole-cell currents were measured in 10 mM Ba2+ throughout. The voltage dependence of inactivation was determined from the peak currents measured at 0 mV after 5 s pulses from −100 to +50 mV. Relative currents were fitted to Boltzmann Eq. 1. Activation data were estimated from the mean I/V relationships and fitted to Boltzmann Eq. 2. Peak IBa was determined from I/V relationships for the corresponding experiments. The data are shown with the mean ± SE and the number n of samples appears in parentheses.
n.d., not determined.