Fig. 1.

Functional characterization of human ABCB1. (A) Normalized ATPase activity of nanodisc-reconstituted ABCB1 in the absence (black bars) or presence of different drugs, and in the absence (−) or presence (+) of the Fab fragment of antibody MRK16. The concentration of ATP was 2 mM throughout. n = 3, error bars represent SDs. (B) Normalized ATPase activity of ABCB1 as a function of ATP concentration in the absence or presence of inhibitors, and in the absence (−) or presence (+) of the MRK16-Fab. The points were plotted with nonlinear regression of the Michaelis–Menten equation. Relative V_max and apparent K_m are displayed in the table. n = 3, error bars represent SDs.