FIG. 2.

Effect of competing amino acids on [¹⁴C]l-serine uptake in the wild type (A and C) and sdaC mutant (B). High-affinity uptake was examined by using 5 μM [¹⁴C]l-serine, with the addition of 50 μM competing unlabeled amino acid as indicated, while low-affinity uptake was examined with 30 μM [¹⁴C]l-serine and 300 μM competing amino acid as indicated. Inhibition is shown as the percentage of the uptake rate observed in the control incubation, where no competing amino acid was added. The data shown are from a single representative experiment; other experiments gave similar results.