Fig. 2. Lineweaver–Burk plots of the [¹⁴C]aspartate/aspartate and [¹⁴C]glutamate/aspartate exchanges in proteoliposomes reconstituted with citrin. Radioactive aspartate (squares) or glutamate (circles) was added at the concentrations indicated to proteoliposomes containing 20 mM aspartate. Valinomycin (1 µg/mg of phospholipids) and nigericin (50 ng/mg of phospholipids) in ethanol (10 µl/ml of liposomes) (B) or ethanol alone (A) were present in the reaction mixture. All data were determined in one experiment with the same preparation of proteoliposomes. Similar results were obtained in three additional independent experiments.