Activation kinetic of the heteromeric K _V 7.2/K _V 7.3 (WT) and K _V 7.2-R198Q/K _V 7.3 (R198Q) channels. (A–D) The n-powered two-exponential function was fitted to the activation phase of K⁺ currents recording from oocytes expressing the WT K_V7.2 (A and B) and the mutant R198Q (C and D) coexpressed with K_V7.3. In both cases, the holding potential was set to −90 mV. The average fast (A and C) and slow (B and D) time constants were calculated from the parameters yielded by the fitting on individual experiments (WT: n = 9; R198Q: n = 8).