Monoglucosyldiacylglycerol, a foreign lipid, can substitute for phosphatidylethanolamine in essential membrane-associated functions in Escherichia coli.
The mechanisms by which lipid bilayer properties govern or influence membrane protein functions are little understood, but a liquid-crystalline state and the presence of anionic and nonbilayer (NB)-prone lipids seem important. An Escherichia coli mutant lacking the major membrane lipid phosphatidylethanolamine (NB-prone) requires divalent cations for viability and cell integrity and is impaired in several membrane functions that are corrected by introduction of the "foreign" NB-prone neutral glycolipid alpha-monoglucosyldiacylglycerol (MGlcDAG) synthesized by the MGlcDAG synthase from Acholeplasma laidlawii. Dependence on Mg(2+) was reduced, and cellular yields and division malfunction were greatly improved. The increased passive membrane permeability of the mutant was not abolished, but protein-mediated osmotic stress adaptation to salts and sucrose was recovered by the presence of MGlcDAG. MGlcDAG also restored tryptophan prototrophy and active transport function of lactose permease, both critically dependent on phosphatidylethanolamine. Three mechanisms can explain the observed effects: NB-prone MGlcDAG improves the quenched lateral pressure profile across the bilayer; neutral MGlcDAG dilutes the high anionic lipid surface charge; MGlcDAG provides a neutral lipid that can hydrogen bond and/or partially ionize. The reduced dependence on Mg(2+) and lack of correction by high monovalent salts strongly support the essential nature of the NB properties of MGlcDAG.
Wikström
Malin
M
Department of Biochemistry and Biophysics, Stockholm University, Sweden.
Xie
Jun
J
Bogdanov
Mikhail
M
Mileykovskaya
Eugenia
E
Heacock
Philip
P
Wieslander
Ake
A
Dowhan
William
W
D000127:Acholeplasma / Q000201:enzymology; D002412:Cations; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006017:Glycolipids / Q000737:chemistry* / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008164:Luminescent Proteins / Q000378:metabolism; D008274:Magnesium / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000737:chemistry; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D009995:Osmosis; D010714:Phosphatidylethanolamines / Q000737:chemistry* / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011312:Pressure; D011485:Protein Binding; D027981:Symporters; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry
D002412:Cations; D029968:Escherichia coli Proteins; D006017:Glycolipids; C050221:LacY protein, E coli; D008051:Lipid Bilayers; D008055:Lipids; D008164:Luminescent Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D010714:Phosphatidylethanolamines; D027981:Symporters; C014571:glucosyl diacylglycerol; D049452:Green Fluorescent Proteins; D011189:Potassium Chloride; D014364:Tryptophan; C021499:lactose permease; D008274:Magnesium