Figure 5.

Concentration dependence of AtMRP1-dependent DNP-GS uptake. AtMRP1-dependent DNP-[³H]GS uptake rates were calculated by subtracting the radioactivity taken up by vacuolar membrane-enriched membrane vesicles prepared from pYES3-transformed DTY168 cells from that taken up by the equivalent membrane fraction from pYES3-AtMRP1-transformed DTY168 cells. The data were fitted to a single Michaelis–Menten function by nonlinear least-squares analysis (25) to yield a K_m and V_max of 49.7 ± 15.4 μM and 6.0 ± 1.7 nmol/mg per 10 min, respectively. Values shown are means ± SE (n = 3–6).