Fig. 3

Dose-response analysis. K_0.5, I_max, and transport efficiency of zebrafish PepT1a (Slc15a1a) evaluated in the presence of Gly-Gln. a I/V relationships were obtained by subtracting the current traces in the absence to that in the presence of the indicated amounts of Gly-Gln, at pH 6.5 (green) and 7.6 (blue). The current values were fitted with the logistic equation \( \left[{I}_0=\frac{-{I}_{\mathrm{max}}}{1+\left(\left[S\right]/{K}_{0.5}\ \right)}+{I}_{\mathrm{max}}\right] \) to obtain K_0.5, i.e., the substrate concentration that yields one-half of the maximal current (I_max), at each indicated voltage and at pH 6.5 (green square) and 7.6 (blue circle). b I_max at each voltage and pH. c K_0.5 at each voltage and pH; the insert (c) is an enlargement of K_0.5 at pH 6.5. d Transport efficiency, evaluated as the ratio of I_max/K_0.5, and plotted vs. membrane potential for the two pH conditions. I_max, relative maximal current; K_0.5, apparent substrate affinity; I_max/K_0.5, transport efficiency