Figure 4.

Effect of MTS reagents on wild-type and S440C mutant transporters. Sodium-dependent d-[³H]aspartate uptake was measured in HeLa cells expressing WT and S440C mutant transporters. Before the transport assay the cells were washed with 150 mM choline chloride-containing medium and subsequently preincubated in the same medium supplemented with or without MTSEA, MTSET, and MTSES at 0.1 mM, 0.2 mM, and 0.25 mM, respectively. After 5 min at room temperature, the cells were washed and assayed for d-[³H]aspartate transport for 10 min. Each bar is mean ± SE of three different experiments. The control value of S440C is 89.5 ± 6.8% of that of wild-type GLT-1.