Effect of synaptotagmin I on the kinetics of Kv1.4ΔN. (A) Representative traces of Kv1.4ΔN currents expressed alone. (B) Representative traces of Kv1.4ΔN currents coexpressed with synaptotagmin I. Currents were elicited by depolarizing steps from -80 to +70 mV in 10 mV increments every 45 s from a holding potential of -80 mV. (C) Currents recorded upon depolarization to +30 mV. (D) Inactivation time constants (τinact) of the indicated channel obtained at +30 mV. Data are mean ± SD of nine experiments. (E) Activation curves of Kv1.4ΔN and Kv1.4ΔN/synaptotagmin I. Current amplitudes recorded were normalized to the maximal response at +30 mV and plotted as a function of the membrane potential.