Figure 3.

Concentration-dependent increase of the intramolecular FRET by verapamil. A, effect of verapamil on the proximity ratio of co-transfected P-gp–mCerulean and P-gp–mVenus. B, effect of the protein expression level on the proximity ratio of P-gp–FRET. C, dose-dependent increase of the proximity ratio by verapamil. Cells were treated with 100 μm verapamil (blue) or DMSO (empty) for 5 min at 37 °C. The proximity ratio is shown relative to that of P-gp–FRET without verapamil. 10–15 cells per sample; ***, p < 0.001; N.S., p > 0.05.