Figure 3.

Determination of the substrate specificity of 4F2hc-LAT1 (A), LAT1 (B), 4F2hc-LAT2 (C), and LAT2 (D) by 100 nM [³H]L-leucine uptake competition assay. With the exception of D-leucine, proteogenic L-amino acids were used as competitors. Competitor concentrations of 250 µM ((A); 4F2hc-LAT1), 100 µM ((B); LAT1), 2500 µM ((C); 4F2hc-LAT2), and 500 µM ((D); LAT2) were used. These concentrations correspond to about ten times the determined L-leucine K_m values of the corresponding transporters (Figure 2). Residual uptake in the presence of competitor was normalized with respect to control samples without competitor (Ctrl). The amino acids are abbreviated using their three-letter-code. Means with SD from normalized data of three independent experiments, each at least in triplicate are shown. If not visible, error bars are smaller than symbols.