FIG. 5.
Kinetics of cation-dependent succinate transport. Initial rates of succinate transport (100 μM) in the presence of NaCl (•) and LiCl (○). Transport was estimated as described in Materials and Methods except that the assay buffer contained 50 mM MOPS-Tris, pH 7, plus the indicated concentrations of NaCl (or LiCl). Assay buffer isotonicity was maintained at 100 mM by the addition of the necessary amounts of choline chloride. Data from three independent trials were normalized to peak values (16 ± 2.9 nmol/mg protein/min for NaCl; 6.7 ± 0.49 nmol/mg protein/min for LiCl) and are shown as means ± standard errors. K0.5 and Vmax values for SdcS under these conditions are shown in Table 1.