Fig. 3.

Negatively charged amino acids in the cavity restore K⁺ selectivity. Only acidic substitutions at the N184 position of Kir3.2 restore K⁺ selectivity to the nonselective S177W mutant channel. Current traces were elicited with voltage pulses from +40 to −150 (in 10-mV increments) from a holding potential of 0 mV in 90 mM K⁺ (green line) and 90 mM Na⁺ (red line). Only traces at −150 mV are shown. All N184 substitutions are in the background of the S177W mutation. Baseline indicates 0 μA current value. (Scale bars: vertical, 10 μA; horizontal, 20 ms.)