R477H presents strong pH dependence for apparent glutamate affinity. (A–C) Representative current traces elicited by K_0.5 concentrations (see Table 1) of l-glutamate for control (uninjected oocytes; A), WT EAAT (B), and R477H (C) at pH 5.5 (black bars) and 8.5 (red bars). (D and E) l-Glutamate concentration responses for WT EAAT1 (D) and R477H (E) were conducted at −60 mV in ND96 at pH 5.5 (black), 6.5 (orange), 7.5 (blue), and 8.5 (red). (F) Na⁺ concentration responses were performed at −60 mV for WT EAAT1 (closed squares) and R477H (open circles) at pH 5.5 in the presence of 300 µM or 3 µM l-glutamate for WT EAAT1 or R477H, respectively. Choline⁺ was used as the substitute cation. Currents were normalized to the maximal current activated for each cell. Data shown represent the mean ± SEM (n ≥ 3). Where error bars cannot be seen, they lie within the symbol.