Changes in permeant ion-induced conductance between KirBac1.1 WT and I131x mutants. (A) Sequence alignment of SF signature sequences and TM2 of potassium channels. SF in green and I131 equivalent position in red. (B) Crystal structure of KirBac1.1 SF and transmembrane domains with residues forming K binding sites highlighted in green and I131 position in red. (C and D) Cartoon diagram of K-driven ⁸⁶Rb⁺ or ²²Na⁺ assays (C) or Na-driven assays (D). (E) Time course of ⁸⁶Rb⁺ uptake into liposomes (POPE:POPG, 75:25%), with 450 mM internal K⁺ (left) or Na⁺ (right). Inf, influx. (F) Time course of ²²Na⁺ uptake into liposomes (POPE:POPG, 75:25%), with 450 mM internal K⁺ (left) or Na⁺ (right). Liposomes were reconstituted with no protein (empty, gray), KirBac1.1 WT (black), or KirBac1.1 I131S/G/M (red, blue, and green, respectively; 2 µg/mg lipid). *, P < 0.05 versus. WT. All data are represented as mean ± SEM of at least n = 3 experiments.