Three-state ion-dependent kinetic model in KirBac1.1 WT and I131M. (A) Three-state kinetic model for ion-dependent conformational transitions in KirBac1.1. The channels SF is presumed to exist in high FRET state (H), medium FRET state (M), and low FRET state (L). (B) Transition density plots (TDP) between the three states for WT and I131M in increasing [K⁺]/[Na⁺]. (nt indicates total number of transitions; nt from n traces given in Figs. 6 and 7). (C) Ion dependence of calculated state probability obtained from the idealized traces. The [K⁺]/[Na⁺] dependence of H and L state probability is weaker in I131M than in WT. (D) Calculated rate constants for WT and I131M as a function of [K⁺]/[Na⁺]. *, P < 0.05 versus WT. As in Fig. 8, concatenated trajectories were split into three equal-sized groups and analyzed separately to assess variability in the data, which are presented as mean ± SEM of the three data groups.