Voltage dependence of accessibility to MTSET overlaps between the full-length channel and L341 split. (A and B) Representative currents and mean current ratios (±SEM) from I319C (A) and L322C (B) mutants before and after application of 200 µM MTSET at 0 or −100 mV. (C and D) Representative graphs showing the time course of current changes upon MTSET application at hyperpolarized and depolarized potentials for the weakly voltage-dependent I319C site (C) and the strongly voltage-dependent L322C site (D). Curves represent single-exponential fits to data points from individual cells. Insets contain histograms with mean modification rate constants ± SEM (n = 5–8).