Figure 2.

Efflux of d-[³H]aspartate from wild type (Left) or Y403F proteoliposomes (Right) in which it was previously accumulated by exchange. For each time, 20 μl of proteoliposomes containing 0.12 M sodium phosphate and 10 mM l-aspartate was loaded with d-[³H]aspartate by dilution into 80 μl of 0.15 M NaCl and 1 μCi of labeled aspartate (1 Ci = 37 GBq). After 10 min, the mixture was diluted into 1 ml of 0.15 M NaCl (▪), 20 mM KCl/130 mM NaCl (▴), 150 mM KCl (•), or 0.15 M NaCl/100 M l-glutamate (▾). Reactions were terminated at the times indicated at the abscissa.