Figure 3

Effect of intracellular hemin on voltage-gated K⁺ channels. (A) Averaged current responses, normalized to the maximal control current at 40 mV (80 mV for Kv11.1-ni), of the indicated channel types recorded from inside-out patches of Xenopus oocytes before (black) and 180 s after (color) application of 200 nM hemin. Depolarization steps were applied to 0 and 40 mV for Kv10.1, Kv1.1, and Kv1.5 channels, and to 40 and 80 mV for Kv11.1-ni. Thick traces are means; shading indicates sem; for n see panel (C). (B) Normalized, mean maximal currents at 40 mV (80 mV for Kv11.1-ni) as a function of time after application of 200 nM hemin at time zero. Straight lines connect data points for clarity. (C) Averaged relative current remaining 180 s after application of 200 nM hemin for the indicated channel types. Data are mean ± sem, the numbers of independent experiments are indicated in parentheses. (D) Representative current traces recorded from inside-out Xenopus oocyte patches with Kv10.1 wild-type channels (left) at 40 mV before (black) and 150 s after application of 200 nM hemin. Right: Current traces for the N-terminal deletion mutant (∆N) before (blue) and 90 s after application of 200 nM hemin (red). Holding potential for Kv10.1 was − 80 mV and for Kv10.1∆N − 120 mV; the latter traces are shown without p/n leak subtraction because of high channel activity in the leak voltage range. (E) Time course of current decrease after application of 200 nM hemin for the indicated channel types: Kv10.1 (n = 8) and Kv10.1∆N (n = 4).