FIGURE 5.

Determination of the affinity of the glutamate-bound transporter for Na⁺. Anion currents were determined as a function of [Na⁺] at a close to saturating concentration of 30 mm glutamate (EAAC1_WT, triangles; EAAC1_T101A, closed squares; no currents were induced when the glutamate was substituted by 30 mm MES⁻). The open squares represent I_max values calculated by extrapolation according to the K_m values for glutamate at each [Na⁺] shown in Fig. 4C. The solid lines represent fits to the Hill equation (fit parameters in main text). All of the experiments were performed in the exchange mode and at 0 mV transmembrane potential. The currents were normalized to the response induced by 140 mm Na⁺.