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Monoglucosyldiacylglycerol, a foreign lipid, can substitute for phosphatidylethanolamine in essential membrane-associated functions in Escherichia coli
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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2004 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 279, no 11, 10484-10493 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2004. Vol. 279, no 11, 10484-10493 p.
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:su:diva-23041DOI: 10.1074/jbc.M310183200ISI: 000220050400100OAI: diva2:189957

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 Mg2+ 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 Mg2+ and lack of correction by high monovalent salts strongly support the essential nature of the NB properties of MGlcDAG.

Available from: 2006-11-16 Created: 2006-11-16 Last updated: 2013-12-10Bibliographically approved
In thesis
1. Synthesis and protein curing abilities of membrane glycolipids
Open this publication in new window or tab >>Synthesis and protein curing abilities of membrane glycolipids
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There are many types of membrane lipids throughout Nature. Still little is known about synthesizing pathways and how different lipids affect the embedded membrane proteins. The most common lipids are glycolipids since they dominate plant green tissue. Glycolipids also exist in mammal cells as well as in most Gram-positive bacteria. Glycosyltransferases (GTs) catalyze the final enzymatic steps for these glycolipids. In the bacteria Acholeplasma laidlawii and Streptococcus pneumonie and in the plant Arabidopsis thaliana, GTs for mono-/di-glycosyl-diacylglycerol (-DAG) are suggested to be regulated to keep a certain membrane curvature close to a bilayer/nonbilayer phase transition. The monoglycosylDAGs are nonbilayer-prone with small headgroups, hence by themselves they will not form bilayer structures.

Here we have determined the genes encoding the main glycolipids of A. laidlawii and S. pneumonie. We have also shown that these GTs belong to a large enzyme group widely spread in Nature, and that all four enzymes are differently regulated by membrane lipids. The importance of different lipid properties were traced in a lipid mutant of Escherichia coli lacking the major (75 %), nonbilayer-prone/zwitterionic, lipid phosphatidylethanolamine. Introducing the genes for the GTs of A. laidlawii and two analogous genes from A. thaliana yielded new strains containing 50 percent of glyco-DAG lipids. The monoglyco-DAG strains contain significant amounts of nonbilayer-prone lipids while the diglyco-DAG strains contain no such lipids. Comparing these new strains for viability and the state of membrane-associated functions made it possible to connect different functions to certain lipid properties. In summary, a low surface charge density of anionic lipids is important in E.coli membranes, but this fails to be supportive if the diluting species have a too large headgroup. This indicates that a certain magnitude of the curvature stress is crucial for the membrane bilayer in vivo.

Place, publisher, year, edition, pages
Stockholm: Institutionen för biokemi och biofysik, 2006. 48 p.
membrane, lipids, glycolipids, nonbilayer-prone
National Category
Biochemistry and Molecular Biology
urn:nbn:se:su:diva-1361 (URN)91-7155-351-7 (ISBN)
Public defence
2006-12-15, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Available from: 2006-11-16 Created: 2006-11-16Bibliographically approved

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