Fig. 3.

Mutation of Thr58 (hNET) and Thr62 (hDAT) to aspartate results in enhanced substrate potency. DA transport was measured in hNET (■), T58A-hNET (▴), and T58D-hNET (♢) cells in the presence of increasing concentration of DA (A), NE (B), and AMPH (C) and in hDAT (■), T62A-hDAT (▴), and T62D-hDAT (♢) cells in the presence of increasing concentrations of DA (D) and NE (E). Cells were incubated with 30 nM [³H]DA and indicated concentrations of competing substrate for 3 min at room temperature and processed as described under Materials and Methods. Data are expressed as percentage of [³H]DA uptake in the absence of any added substrate (control). IC₅₀ values, 95% confidence intervals, and statistical analysis of the results are given in Table 2.