(A) Two-Electrode Voltage-Clamp recordings of heterologously expressed DrCNGK channels in the presence of different K+ concentrations (left panel: 7 mM, middle panel: 96 mM) and corresponding IV relation (right panel). (B) Two-Electrode Voltage-Clamp recordings of uninjected oocytes (control) in the presence of different K+ concentrations (left panel: 7 mM, middle panel: 96 mM). (C) Pooled IV curves of Two-Electrode Voltage-Clamp recordings of DrCNGK-injected and uninjected oocytes (control) in the presence of different K+ concentrations (left panel: 7 mM, middle panel: 96 mM). Number of experiments is given in parentheses. (D) Reversal potentials (Vrev) of DrCNGK-injected and control oocytes in the presence of different K+ concentrations. Number of experiments is given in parentheses. (E) Whole-cell recordings from zebrafish sperm and Two-Electrode Voltage-Clamp recordings from heterologously expressed DrCNGK channels in the absence and presence of different TEA concentrations (0, 1, and 100 mM TEA). (F) Normalized ((I-IminFit)/ImaxFit) dose dependence of TEA block. Mean current ± sd. Individual dose response curves were fitted with the Hill equation. Mean ( ± sd) Ki value and Hill coefficient for sperm K+ current were 4.5 ± 1.1 mM and 1.0 ± 0.2 (n = 5) and for DrCNGK in oocytes 1.6 ± 0.3 mM and 1.0 ± 0.1 (n = 11), respectively. The solid lines were calculated with the Hill equation using mean values for Ki and the Hill coefficient.