MsbA-dependent translocation of lipids across the inner membrane of Escherichia coli.
MsbA is an essential ABC transporter in Escherichia coli required for exporting newly synthesized lipids from the inner to the outer membrane. It remains uncertain whether or not MsbA catalyzes trans-bilayer lipid movement (i.e. flip-flop) within the inner membrane. We now show that newly synthesized lipid A accumulates on the cytoplasmic side of the inner membrane after shifting an E. coli msbA missense mutant to the non-permissive temperature. This conclusion is based on the selective inhibition of periplasmic, but not cytoplasmic, covalent modifications of lipid A that occur in polymyxin-resistant strains of E. coli. The accessibility of newly synthesized phosphatidylethanolamine to membrane impermeable reagents, like 2,4,6-trinitrobenzene sulfonic acid, is also reduced severalfold. Our data showed that MsbA facilitates the rapid translocation of some lipids from the cytoplasmic to the periplasmic side of the inner membrane in living cells.
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
William T
WT
Doerrler
Henry S
HS
Gibbons
Christian R H
CR
Raetz
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D001089:Arabinose / Q000031:analogs & derivatives* / Q000737:chemistry; D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D020404:Glycerophospholipids / Q000737:chemistry; D006900:Hydroxylation; D007425:Intracellular Membranes / Q000378:metabolism*; D008050:Lipid A / Q000737:chemistry; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008954:Models, Biological; D008956:Models, Chemical; D009154:Mutation; D020125:Mutation, Missense; D019897:Periplasm / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D021381:Protein Transport; D012475:Salmonella / Q000378:metabolism; D013395:Sucrose / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014302:Trinitrobenzenesulfonic Acid / Q000737:chemistry
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D020404:Glycerophospholipids; D008050:Lipid A; D008055:Lipids; C079726:MsbA protein, Bacteria; D010714:Phosphatidylethanolamines; C016982:aminoarabinose; C483858:phosphatidylethanolamine; D013395:Sucrose; D014302:Trinitrobenzenesulfonic Acid; D002784:Cholesterol; D001089:Arabinose