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Cell. 1994 Jul 1;77(7):1071-81.

Phosphatidylcholine translocase: a physiological role for the mdr2 gene.

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Department of Biochemistry, McGill University, Montreal, Quebec, Canada.


P-glycoproteins (P-gps) encoded by the mouse mdr2 and mdr3 genes were expressed in secretory vesicles (SVs) from the yeast mutant sec6-4, and their capacity to function as a lipid translocase/flippase was tested. An assay that uses a fluorescent phosphatidylcholine (PC) analog was developed to quantitate asymmetric lipid distribution in the outer and inner leaflets of the lipid bilayer of these vesicles. Mdr2 expression in SVs caused a time- and temperature-dependent enhancement of PC translocation to the inner leaflet of the membrane. The Mdr2-mediated effect was specific since expression of Mdr3 in these vesicles was without effect on the membrane distribution of PC. Increased Mdr2-mediated PC translocation was strictly ATP and Mg2+ dependent, was abrogated by the ATPase inhibitor vanadate and the P-gp modulator verapamil, but was insensitive to the presence of excess of the multidrug resistance drugs colchicine and vinblastine.

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