Na⁺ can permeate through R477H at pH 8.5. (A–D) Current-voltage relationships for WT EAAT1 and R477H elicited by submaximal l-glutamate in 10 mM (red squares) and 100 mM (blue squares) Na⁺-based buffers at pH 5.5 (A and C) and 8.5 (B and D). All buffers were osmotically balanced using choline⁺ as the substitute cation. Data shown represent the mean ± SEM (n ≥ 4). Where error bars cannot be seen, they lie within the symbol. Note the scale difference in the y axes.