Alterations of channel kinetics in Y347 split and G348 split. (A) Tail current, normalized to the steady-state current at the end of the depolarizing segment of the voltage pulse, plotted against time at negative potential (mean ± SEM; n = 6). (Top right) Super slow deactivation component indicated by the red arrow. (B) Representative currents of the wild type, Y347 split, and G348 split recorded with the reactivation protocol with various intervals at −120 mV between the depolarizing pulses. (C) Time needed for current to reach 90% of its maximal value plotted against the length of the interval at −120 mV (mean ± SEM; n = 6–8). (D) Representative voltage-dependent changes of fluorescence reported by I319C-TMRM, elicited by a depolarization to 60 mV from a holding potential of −100 mV. (E) Activation and deactivation time constants obtained by exponential fits to fluorescence traces (n = 5–8; mean ± SD). Asterisks indicate statistical significance (P < 0.001). (Inset) Superimposed VCF traces from D with an expanded time base.