Phosphatidylcholine translocase: a physiological role for the mdr2 gene.
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.
Ruetz
S
S
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Gros
P
P
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism; D066298:In Vitro Techniques; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D051379:Mice; D010713:Phosphatidylcholines / Q000378:metabolism*; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D011994:Recombinant Proteins