Saturation of the ΔpH dependence of WT hHV1 (A and B) and of W207X mutants of hHV1 (C and D). The voltage at which gH is 10% maximal (VgH,max/10) is plotted as a function of pHo (A and C) or pHi (B and D), with lines connecting measurements in the same cell. In whole-cell measurements, pHi is color coded, as indicated. In inside-out patches, pHo is color coded, as indicated. For reference, the dashed gray line in each graph shows the slope of the ubiquitous 40-mV/U ΔpH shift in the gH–V relationship (Cherny et al., 1995; DeCoursey, 2003); the horizontal position of this line is arbitrary. (C) Data from 13 W207A, eight W207F, and two W207S cells. (D) Data from three W207A, one W207F, and one W207S patch. No differences were detected among the Trp replacements.
