*4.7. Preparation of ABCG2-Expressing Plasma Membrane Vesicles*

Plasma membrane vesicles were prepared from ABCG2-expressing 293A cells, as described previously [36]. The resulting plasma membrane vesicles were rapidly frozen in liquid N<sup>2</sup> and kept at −80 ◦C until used. The protein concentration of the plasma membrane vesicles was measured using a BCA Protein Assay Kit, as described above.
