A, whole‐cell patch clamp recording from human sperm at pHi = pHo = 6, 7, and 7.5. Voltage‐dependent outward currents (top traces) evoked by voltage steps (bottom traces) of increasing amplitude (–80 to +100 mV, pH 6 and 7; –20 to +100 mV, pH 7.5). B, inhibition of outward currents in excised patches of X. laevis oocytes heterologously expressing Hv1 or Hv1Sper by extracellular Zn2+ and intracellular 2GBI at pHi = pHo = 7. Currents were evoked by a voltage step from –80 mV to +80 mV (Zn2+: Hv1 99.7 ± 0.3% inhibition, n = 3; Hv1Sper 98.9 ± 1%, n = 4; 2GBI: Hv1 69.4 ± 3.7% inhibition, n = 3; Hv1Sper 74.2 ± 1.4%, n = 3). Error bars indicate the SD.