FIGURE 4.

Kinetics of Ba²⁺ block and unblock in WT KCNQ1 and mutants L273F and L273W. (A–C) After depolarization from −80 mV to −20 mV for 24 s, 10 mM Ba²⁺ was applied to oocytes expressing WT or mutant channels for 12 s and then was washed out for 48 s, while keeping the membrane at −20 mV. (D) Fast (triangles) and slow (squares) time constants of Ba²⁺ block in WT KCNQ1 (black) and mutant L273F (blue) with their respective slow component amplitude (E) plotted as a function of voltage (A_s and A_f are the amplitudes of the slow and fast components, respectively). (F) Fast (open triangles) and slow (open squares) time constants of Ba²⁺ unblock in WT KCNQ1 (black) and mutant L273F (blue) with their respective slow component amplitudes (G) plotted as a function of voltage. Data shown are mean ± SE (n = 6–8).