Figure 6.

For a Figure360 author presentation of this figure, see https://doi.org/10.1016/j.bpj.2020.03.032.

Inactivation kinetics of hKv2.1, hKv3.1 and their T-to-A mutants. (a) and (b) show representative current recordings for hKv2.1 (a) and hKv3.1 (b) channels with their T-to-A mutations represented on the right, respectively. Currents were elicited with the pulse protocols shown on top, and the zero-current level is indicated by the horizontal bar at the start of the recordings. Prolonged depolarizations induce inactivation in WT channels, resulting in a gradual decrease in current amplitude. The degree of channel inactivation was determined by applying an activating test pulse to +60 mV, which elicited a current amplitude that reports directly on the number of channels that did not inactivate. Note, the current amplitude of hKv2.1-T377A (a) gradually increased upon prolonged depolarization or remained constant for hKv3.1-T400A (b). (c) and (d) display the voltage dependence of channel inactivation for the WT hKv2.1 and hKv3.1 channels (open circles). Curves were obtained by plotting the normalized current amplitude at the +60 mV test pulse at (I/Imax) as a function of the 5-s preconditioning depolarization. Stronger depolarizations induced after 5 s ∼60 and 70% of channel inactivation in hKv2.1 (c) and hKv3.1 (d), respectively. Plotting the normalized currents elicited with the activating test pulse for the T-to-A mutations (solid circles) resulted in an opposite behavior. The mutants did not inactivate, and hKv2.1-T377A contradictorily displayed an increase in current (c). Represented values are the means ± SEM from five to eight independent observations.