LIN, LIN-Gly, and LIN-Tyr require residue R218 to maintain their voltage dependence shifting effect. Experiments were done on the human KCNQ1 channel with the mutation R228Q; the Xenopus numbering R218 is used here for ease of comparison with the simulations. (A) Model of PUFA interaction with S4 that causes the V0.5 shifting effect, with residue R218 in the voltage sensor marked. (B) Conductance versus voltage (G(V)) curve of the R218Q and WT KCNQ1 currents with and without 7 µM of LIN-Gly. (C–E) ΔV0.5 dose response curve of (C) LIN (WT n = 8 and R218Q n = 3), (D) LIN-Gly (WT n = 10 and R218Q n = 3), and (E) LIN-Tyr (WT n = 6 and R218Q n = 5) on WT versus R218Q mutated KCNQ1 channels. Data are shown as mean ± SEM. (F–H) Comparison of ΔV0.5 effect on WT KCNQ1 channels versus R218Q mutated channels at 7 µM of (F) LIN (WT: −5.45 ± 0.69 mV; n = 8 and R218Q: −1.04 ± 0.54 mV; n = 3); a t test gave P = 0.005; (G) LIN-Gly (WT: −25.28 ± 1.69 mV; n = 10 and R218Q: −6.03 ± 5.43 mV; n = 3); ANOVA with Tukey’s multiple comparison, also containing the mutations in Fig. 8, gave P = 0.0015; (H) LIN-Tyr (WT: −43.57 ± 1.03 mV; n = 6 and R218Q: −10.89 ± 4.61 mV; n = 5), ANOVA with Tukey’s multiple comparison, also containing the mutations in Fig. 8, gave P = 0.0018. Data are shown as mean ± SEM. **, P < 0.01; ***, P < 0.001.