FIGURE 5.

Role of Glu-255, Asp-371, and neighboring residues in Na⁺ coupling. A, B, D, E, and H, active ethidium efflux activity in cells expressing E255Q (A), D371N (B), Y367A (D), F395A (E), or F288A (H) mutant was performed as described in the legend to Fig. 1C. C, F, and G, rates of facilitated ethidium efflux in ATP-depleted cells containing D371N (C), F395A (F), or F288A (G) mutant were measured as a function of the Na⁺ concentration as described for Fig. 1D. Error bars represent the mean ± S.E. of four independent observations.