Figure 2.
Coccolithophore EukCatB channels expressed in HEK293 cells yield currents with very fast kinetics. A, Under control external solution (E1; Supplemental Table S4), typical current traces for cells expressing EhEUKCATB1 in response to membrane depolarization from a holding potential of –120 mV. Average peak current–voltage curves (right), where current was normalized to cell capacitance. Peak current = 64.45 ± 6.64 pA/pF (n = 57). B, Steady-state inactivation: representative examples of current traces (left) used to obtain steady-state inactivation curves (right) for EhEUKCATB1 (n = 14). Average normalized data were fitted using the Boltzmann equation (see “Materials and Methods”) for both activation (solid circles) and steady-state inactivation (open circles) curves (τactivation < 0.6 ± 0.1 ms; τinactivation < 3.5 ± 0.9 ms). Error bars: means ± se (see Supplemental Table S3) C, Recovery from inactivation; superimposed currents obtained by a double-pulse protocol using a varying interval (∆t) between the two voltage pulses (gray dashed box). Holding potential was –100 mV and test potential was −30 mV for 5 ms, followed by a recovery test pulse to –30 mV for 5 ms at 100 to 1,800 ms after the first test pulse. The peak currents elicited by the recovery pulse were normalized to construct the recovery curve. A single exponential was fitted to the averaged normalized recovery curve yielding τ for recovery (first-order exponential fit) of 632 ± 50.6 ms (n = 14).