Slc7a5 prolongs deactivation of Kv1.2/Kvβ. (A) Representative current traces of channel deactivation from LM cells transfected with combinations of WT Kv1.2, Kvβ, and Slc7a5. Cells were depolarized to +100 mV for 200 ms followed by repolarizing steps from −60 to −150 mV in 10-mV increments for 600 ms before returning to a −100 mV holding potential. Current traces highlight the deactivation tail currents upon repolarization to voltages between −60 and −150 mV. (B) Overlapping deactivation tail currents at −130 mV from representative current traces in A. Deactivation tails of WT Kv1.2, Kv1.2 + Kvβ, and Kv1.2 + Slc7a5 were fitted with a single exponential function. Deactivation tails of Kv1.2 + Kvβ + Slc7a5 were fitted with a double exponential function. (C) Time constants of deactivation (mean ± SD) calculated from single (WT Kv1.2, Kv1.2 + Kvβ, Kv1.2 + Slc7a5) or double (Kv1.2 + Kvβ + Slc7a5) exponential functions of the deactivation tail currents obtained from the voltage protocol in A. (D) τ Deactivation of individual cells from each group were obtained from the deactivation tail currents at −130 mV from a +100-mV depolarizing step (τ deact [ms] at −130 mV ± SD; WT Kv1.2 = 2.7 ± 0.5; Kv1.2 + Kvβ = 7.2 ± 1.9; Kv1.2 + Slc7a5 = 24.9 ± 5.2; Kv1.2 + Slc7a5 + Kvβ [fast] = 27 ± 13 ms; Kv1.2 + Slc7a5 + Kvβ [slow] = 151 ± 57; n = 13–21 individual cells recorded for each group).