Figure 8.

Permeability ratios in Kv2.1 Y380 mutants. (A–D) I-V relationships, obtained as in Fig. 1, with equimolar internal and external Na⁺ (125 mM) plus 0 K⁺ (filled circles) or after addition of 1 mM external K⁺ (open circles). Each pair of I-V curves was obtained from a single cell. A and C illustrate I-V relationships from the Y380C and Y380T mutants, respectively, which contain the lysine at position 356. B and D illustrate I-V relationships from these two mutants after mutation of the 356 residue to a glycine. (Note that the additional K382V mutation in the Y380T channel had no impact on the results.) (E) Average reversal potentials (n = 3) in the presence of 1 mM external K⁺ in these four channels. In the absence of K⁺, currents reversed at 0.4 ± 0.1 mV (n = 12).