FIGURE 6.

Slow inactivation of KCNQ1 mutants causes Ba²⁺ trapping. Representative traces of mutant V310G at 0 mV (A) or at +40 mV (B) showing Ba²⁺ block (10 mM, 12 s) and unblock upon washout for 48 s. (C) Current deficit upon Ba²⁺ washout (open bars) and fractional inactivation (solid bars) measured in mutant V310G at 0 mV, +20 mV, and +40 mV. Current deficit = (Y-Z)/Y, where Z is the current measured after 48 s Ba²⁺ washout and Y is the current at the same time point in the absence of Ba²⁺. (D) Representative traces of mutant E295A at 0 mV showing Ba²⁺ block (12 s) and unblock upon 48 s washout. (E) Time constant of Ba²⁺ block in E295A channels at 0 mV (left) and current deficit measured after 48 s washout (right). (F) Representative traces of mutant D317A at +20 mV showing Ba²⁺ block (12 s) and unblock upon 48 s washout. (G) Slow (open bars) and fast (solid bars) time constants of Ba²⁺ block (10 s) in WT and D317A channels at +20 mV, with their respective slow component amplitudes (H, I) Slow (open bars) and fast (solid bars) time constants of Ba²⁺ unblock in WT and mutant D317A. Data shown are mean ± SE (n = 5–7; * p < 0.001).