Figure S3.

Q559K, a pore lining residue mutation that eliminates channel rundown, has the same pH_i sensitivity as WT TMEM16F. (A) Representative TMEM16F-Q559K currents recorded from inside-out patches perfused with intracellular solutions containing 100 µM Ca²⁺ at different pH_i values. (B) The G-V curves of Q559K currents at different pH_i values. Error bars represent SEM (n = 5). (C) The pH_i sensitivity of Q559K (QK) evaluated by the G-pH_i relationship. The slope of the G-pH_i relationship for Q559K at 100 µM Ca²⁺ is 0.20 ± 0.02, shown as red solid line. The G-pH_i curves of WT at different Ca²⁺ concentrations are also plotted as dashed lines for reference.