FIGURE 12.

Interaction of hASCT2 reconstituted in proteoliposomes with aspartate. Purified hASCT2 was reconstituted in proteoliposomes containing 10 mM glutamine as described in materials and methods. In (A), inhibition by aspartate of the glutamate transport by ASCT2 reconstituted in proteoliposomes. The transport assay was started by adding 500 μM [³H]glutamate together with 50 mM Na-gluconate to proteoliposomes in the presence of indicated concentrations of aspartate. The transport was measured in 60 min according to the stop inhibitor method. The transport was indicated as % residual activity with respect to the condition with no external addition (none). Results are means ± SD from four independent experiments. *Significantly different from the control sample (none) as estimated by Student’s t-test (P < 0.05). In (B), uptake of glutamate and aspartate by ASCT2 in proteoliposomes. The transport assay was started by adding 500 μM [³H]glutamate (○) or 500 μM [³H]aspartate (●) together with 50 mM Na-gluconate to proteoliposomes. The transport was stopped at the indicated times according to the stop inhibitor method. Data were plotted with the first-order rate equation. Results are means ± SD from three independent experiments.