Fig. 2.

Cell surface expression and function of PCFT mutants. A, top: Western blot analysis of the level of Cys-substituted Trp PCFT mutants at the cell surface based on biotinylation of extracellular Lys residues. A, bottom: PCFT expression in the crude membrane fraction. A, middle: actin loading control. B: function of PCFT mutants assessed by [3′,5′,7-³H]methotrexate ([³H]MTX) influx (0.5 and 50 μM) at pH 5.5 for 1 min. The images in A are representative of 3 independent experiments; the data in B are the mean ± SE from 3 independent experiments. WT, wild type.