FIGURE 3.

Mutations at the base of the selectivity filter alter Rb⁺ permeation. (Top) Typical current traces recorded during voltage pulses from −130 to +60 mV from wild-type (ATAT/SASA) and Kir3.1-A-142V/Kir3.4-T-148V (VVVV/SASA) and Kir3.1-S-166L/Kir3.4-A-172L (ATAT/LLLL) mutant channels with K⁺ or Rb⁺ as the charge carrier. Currents were recorded in 90 mM extracellular K⁺ or 90 mM extracellular Rb⁺. Arrows indicate zero current. (Bottom) Mean normalized current-voltage relationships for each channel with K⁺ or Rb⁺ as the charge carrier. Mean ± SE shown (n = 5–9).