Ion permeability of the TMEM16F wt, D703R and Y563A mutants. (A) Inside-out excised membrane patches expressing TMEM16F wt or the indicated mutant were stimulated with a solution containing 1 mM Ca2+ at the time indicated in the upper traces. The holding potential was +60 mV. Patches were exposed to 140 mM NaCl and (B) 14 mM NaCl, (C) 140 mM NMDG-Cl, (D) 140 mM NaMeS or (E) 140 mM NaSCN. IV relations were determined by voltage ramps from +100 to −80 mV. Only the regions around reversal potentials are shown. Leakage currents measured in 0 Ca2+ were subtracted. (F) Comparison of PNa/PCl for TMEM16F wt and the indicated mutants (n = 3–19, *** p < 0.001, Dunnett test after ANOVA F = 19.303, p = 7.26 × 10−6). (G) Comparison of the shift of reversal potentials after the replacement of 140 mM NaCl with 140 mM NMDG-Cl, NaMeS or NaSCN for TMEM16F wt and the indicated mutants (for NMDG-Cl: *** p < 0.001, Dunnett test after ANOVA F = 30.569, p = 7.79 × 10−6; for NaMeS: *** p < 0.001, Dunnett test after ANOVA F = 26.3, p = 3.86 × 10−7; for NaSCN: ANOVA, F = 1.499, p = 0.25).