Figure 2. The Kv2.1 V378A mutant is a nonselective cation channel. Whole-cell patch-clamp recordings from transiently transfected CHO-K1 cells. Currents are responses to voltage steps from a holding potential of −100 mV. (A) Kv2.1 wild-type currents. 50-ms steps to 40 mV, and then to −120, −80, −40, 0, or 40 mV. (B) Kv2.1 V378A currents elicited by the same protocol as A. (C and D) Same cell and protocol as in A and B but with external Na+ replaced by NMDG+. (E) Instantaneous current level from Kv2.1 V378A at the indicated voltage after a 50-ms step to 40 mV in control external (black) or NMDG external (gray). (F) Permeability ratios for the indicated ion over K+, calculated from the reversal potential when external Na+ is replaced with the indicated ion. Cotransfection delivered an equal amount of wild-type and V378A DNA. *, P < 0.01, compared with wild type by two-tailed Mann–Whitney U test. Error bars represent means ± SEM.
Figure 2.

The Kv2.1 V378A mutant is a nonselective cation channel. Whole-cell patch-clamp recordings from transiently transfected CHO-K1 cells. Currents are responses to voltage steps from a holding potential of −100 mV. (A) Kv2.1 wild-type currents. 50-ms steps to 40 mV, and then to −120, −80, −40, 0, or 40 mV. (B) Kv2.1 V378A currents elicited by the same protocol as A. (C and D) Same cell and protocol as in A and B but with external Na+ replaced by NMDG+. (E) Instantaneous current level from Kv2.1 V378A at the indicated voltage after a 50-ms step to 40 mV in control external (black) or NMDG external (gray). (F) Permeability ratios for the indicated ion over K+, calculated from the reversal potential when external Na+ is replaced with the indicated ion. Cotransfection delivered an equal amount of wild-type and V378A DNA. *, P < 0.01, compared with wild type by two-tailed Mann–Whitney U test. Error bars represent means ± SEM.

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