FIG. 3.

Time course of uptake of BCAAs and methionine in whole cells of L. lactis. (A) Uptake of l-isoleucine by L. lactis MG1363 (open circles), MGbcaP (closed circles), and MGbcaP (pNGbcaP) overproducing BcaP (closed triangles). l-[¹⁴C]leucine uptake in the presence of 100 μM of unlabeled substrate and in the absence of glucose in the uptake buffer is shown in the inset. (B) Uptake by L. lactis MG1363 and L. lactis MGbcaP (pNGbcaP) of l-leucine (open and closed triangles, respectively), l-valine (open and closed squares, respectively), and l-methionine (open and closed circles, respectively). Transport assays using concentrated samples of cells harvested from the exponential phase of growth were performed in the presence of 0.05 μCi ¹⁴C- or ³⁵S-labeled amino acid and 250 μM of the corresponding unlabeled amino acid as described in Materials and Methods. Prior to the uptake assay, cells were energized by incubation for 5 min at 30°C in the presence of 0.5% glucose. T, time.