Figure 12. Reconstruction of effects of K448E mutation and pH on the transport-associated current.

A, normalized currents for wild-type (□) and mutated (○) transporters at pH 7.6. B, normalized current for mutated transporter at pH 7.6 (○) and pH 9.0 (▵). C, normalized current for mutated transporter at pH 7.6 (○) and pH 6.5 (▿). After fitting an arbitrary sigmoidal function I =f(V) to the squares in A (continuous line), the other curves in the figure were obtained by shift and scaling operations: I’ =kf(V+ΔV). In A, ΔV = +20 mV (dotted line) and k = 0.88 (dashed line through ○ symbols). In B, ΔV = +40 mV (dotted line) and k = 0.19 (dashed line through ▵ symbols). In C, ΔV = −4 mV (dotted line) and k = 1.0 (dashed line through ▿ symbols).