Fig. 6.

Differential mutation-induced alterations of basal (a) and substrate-stimulated (b) ATPase activity of ABCG2. a Crude membranes from transfected HEK293 cells expressing wild-type ABCG2, or the L352A, S353A or E356A mutant were incubated in the presence or absence of beryllium-fluoride (0.2 mM beryllium sulfate and 2.5 mM sodium fluoride) in ATPase assay buffer with increasing ATP concentrations in the absence of substrate drug; b the drug-stimulated activity was measured at 5 mM ATP upon addition of 0.25 µM nilotinib (grey bars) in comparison to the basal activity without substrate addition (black bars). The results are expressed as mean values ±SDs from three independent experiments