Figure 2.

Effect of β3xo (xo28) on α_1E. (A and B) Time courses of activation of α_1E in oocytes injected with α_1E cRNA alone or cRNAs encoding both α_1E and β3xo (clone xo28). (C and D) Effect of β3xo on voltage-dependent activation and inactivation of α_1E. G–V curves were obtained from peak tail currents measured by stepping to −50 mV after depolarizing pulses of 25-msec duration from −88 to 116 mV in 4-mV increments. The data were sampled at 10 kHz and filtered at 2 kHz. The data points were fitted by the sum of two Boltzmann distributions. For α_1E, the first component had a V_1/2 = 2.7 mV, an effective valence (zδ) = 2.9 e, and a relative amplitude of 51%; the second had a V_1/2 = 41.8 mV and a zδ = 1.4 e. For α_1E + β3xo, the first component had a V_1/2 = 2.7 mV, a zδ = 3.4 e and a relative amplitude of 75%; the second had a V_1/2 = 51.8 mV and a zδ = 1.3 e. Steady-state inactivation curves were derived from peak currents elicited by a pulse to +20 mV following a conditioning pulse of 10 sec to potentials from −120 to 27 mV in 7 mV increments and a brief (4-msec) pulse to −90 mV. The data were sampled at 500 Hz and filtered at 100 Hz. Sweeps were separated by 20 sec to allow a full recovery from inactivation. Data points were fitted by a Boltzmann distribution. The effective valences were 2.7 ± 0.1 e for α_1E and 3.4 ± 0.1 e for α_1E + β3xo; the half-inactivation potentials were −32.2 ± 3.4 mV (n = 5) for α_1E and −53.5 ± 1.1 mV (n = 4) for α_1E + β3xo.