FIGURE 6.

Competitive inhibition of AspT counterflow with amino acids and analogs. Amino acid inhibition pattern of AspT transport activity. Transport of 39 μm radiolabeled l-aspartate was measured for 10 s in AspT-reconstituted proteoliposomes containing 100 mm l-aspartate. Transport was measured in the absence (no amino acids) or presence of the indicated amino acids or d-cycloserine (CS) or glycine betaine (GB) at 15 mm in the external medium (black bars). Transport of 2.9 mm radiolabeled l-alanine was measured for 10 s in AspT-reconstituted proteoliposomes containing 100 mm l-alanine. Transport was measured in the absence (no amino acids) or presence of the indicated amino acids at 15 mm in the external medium (gray bars). Transport activities are expressed as a percentage of the transport in AspT proteoliposomes containing 100 mm l-aspartate (black bars) or l-alanine (gray bars) in the absence of inhibitors (no amino acids). Data are from two or three independent experiments with three replicates per condition and presented as the average with S.D. (*, p < 0.05; **, p < 0.01, Dunnett's test).