FIGURE 3.

Sodium dependence of glycine transport by GlyT2 and GlyT1 substitution mutants. COS7 cells expressing the indicated transporters were assayed for glycine transport in the presence of increasing extracellular NaCl concentrations (isotonic substitution by choline chloride). Control glycine transport by wild type GlyT2 and GlyT1 were 2.0 ± 0.06 and 5.49 ± 0.26 nmol glycine/mg protein/10 min, respectively. (A,D) Representative experiments are shown that were repeated at least three times performed in triplicate. Glycine transport has been V_max normalized. Experimental data were fitted to the Hill equation. (B–F) EC₅₀ for sodium and Hill coefficient were determined and analyzed by one-way ANOVA with Dunnett’s post hoc test, comparing with wild-type GlyT1 and GlyT2. p > 0.05; ^∗p < 0.05; ^∗∗p < 0.01; ^∗∗∗p < 0.001; ^∗∗∗∗p < 0.0001. For mutants nonsaturated at 150 mM NaCl, determinations up to 300 mM NaCl were performed.