Positively charged mutants at residue 1784 increase noninactivating current. (A) Sample noninactivating currents recorded at −10 mV from residue 1784 mutants at pH 7.4 normalized to peak current. Inset: Unnormalized currents presented in A. (B) Average noninactivating current as a percentage of peak current for residue 1784 mutants recorded between −30 and 0 mV at extracellular pH 7.4 (n = 4–5; Table S8). (C) Average noninactivating current at −30 mV as a percentage of peak current for residue 1784 mutants at extracellular pH 7.4 and pH 6.0 (n = 4–5; Table S8). Error bars are SEM.