Modifications of E290C/KCNE1 by MTSES approximated the WT K_v7.1/KCNE1 current phenotype. (A and B) Current traces of WT K_v7.1/KCNE1 and E290C/KCNE1 before and after MTSES modification. The bottom panel shows the time course of the current resulting from the MTSES modification and DTT application at a test pulse of 40 mV. The increase in current amplitude from MTSES modification was reversed by DTT. (C) Summary data for the effects of MTSES modification on WT K_v7.1/KCNE1 compared with E290C/KCNE1 channels. The relative current was calculated by normalizing the current at 40 mV after MTSES modification to that before MTSES modification (n = 9 for E290C/KCNE1 and n = 5 for WT K_v7.1/KCNE1; *, P < 0.05). (D) The effects of 50 mM K⁺_e on the WT K_v7.1/KCNE1 current. (E) The reduction of the E290C/KCNE1 current by 50 mM K⁺_e before and after MTSES modification. (F) The reduction of the E290C/KCNE1 current by 50 mM K⁺_e after MTSES modification approximated that of the WT K_v7.1/KCNE1 current. The relative current was calculated by normalizing the current obtained using 50 mM K⁺_e to that at 4 mM K⁺_e at the test potential of 40 mV (n = 5 for WT K_v7.1/KCNE1 and n = 7 for E290C/KCNE1).