Fig. 2.

Function and expression of Cys PCFT mutants encompassing the entire TMD4. A: functional assessment. [³H]methotrexate (MTX) influx (0.5 μM) was measured at pH 5.5 at 37°C over 1 min. The horizontal line indicates 50% of wild-type (WT) activity. Values are means ± SE from 3 independent experiments. *Statistically significant reduction in activity compared with WT PCFT (P < 0.05). B: Western blot analysis of PCFT expression in the crude membrane preparation and biotinylated at the cell surface; the actin loading control is also shown. The blot is representative of 2 independent experiments. Vertical lines indicate repositioned gel lanes.