Figure 3.

Estimating unitary conductance in Hv1 W207A-N214R. (A) Plots of maximal Q_ON (Q_{ON max}) versus maximal I_TAIL (I_{TAIL max}) measured in individual cells expressing W207A-N214R (open squares) or W207A-N214R-ΔC (filled triangles) are shown. Mean (± SE) Q_{ON max} = 1.25 ± 0.22 pC, and I_{TAIL max} = 197 ± 40 pA (n = 24 cells). Lines indicate linear fits of the data (W207A-N214, solid line: slope = 5.9 pC/nA; R² = 0.97; W207A-N214R-ΔC, dashed line: slope = 3.9 pC/nA; R² = 0.87. (B) The apparent number of channels (N) is calculated from the total charge (Q_{ON max}) divided by the previously reported (27) gating valences for full-length (squares; z_G = 6 e₀) or truncated (triangles; z_G = 3 e₀) channels’ limiting-slope analyses. Linear fits of maximal G_AQ (G_{AQ max}) determined from Boltzmann fits to G_AQ-V relations in each cell (see Fig. 1D) versus calculated channel number yield estimates of the G_AQ unitary conductances for W207A-N214R (solid line: γ_AQ = 1.75 fS) and W207A-N214R-ΔC (dashed line: γ_AQ = 1.67 fS). To see this figure in color, go online.