Document Detail

Proper fatty acid composition rather than an ionizable lipid amine is required for full transport function of lactose permease from Escherichia coli.
MedLine Citation:
PMID:  23322771     Owner:  NLM     Status:  MEDLINE    
Energy-dependent uphill transport but not energy-independent downhill transport by lactose permease (LacY) is impaired when expressed in Escherichia coli cells or reconstituted in liposomes lacking phosphatidylethanolamine (PE) and containing only anionic phospholipids. The absence of PE results in inversion of the N-terminal half and misfolding of periplasmic domain P7, which are required for uphill transport of substrates. Replacement of PE in vitro by lipids with no net charge (phosphatidylcholine (PC), monoglucosyl diacylglycerol (GlcDAG), or diglucosyl diacylglycerol (GlcGlcDAG)) supported wild type transmembrane topology of the N-terminal half of LacY. The restoration of uphill transport in vitro was dependent on LacY native topology and proper folding of P7. Support of uphill transport by net neutral lipids in vitro (PE > PC ≫ GlcDAG ≠ GlcGlcDAG provided that PE or PC contained one saturated fatty acid) paralleled the results observed previously in vivo (PE = PC > GlcDAG ≠ GlcGlcDAG). Therefore, a free amino group is not required for uphill transport as previously concluded based on the lack of in vitro uphill transport when fully unsaturated PC replaced E. coli-derived PE. A close correlation was observed in vivo and in vitro between the ability of LacY to carry out uphill transport, the native conformation of P7, and the lipid headgroup and fatty acid composition. Therefore, the headgroup and the fatty acid composition of lipids are important for defining LacY topological organization and catalytically important structural features, further illustrating the direct role of lipids, independent of other cellular factors, in defining membrane protein structure/function.
Heidi Vitrac; Mikhail Bogdanov; William Dowhan
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-01-15
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  288     ISSN:  1083-351X     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-02-25     Completed Date:  2013-04-25     Revised Date:  2014-02-25    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  5873-85     Citation Subset:  IM    
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MeSH Terms
Amines / chemistry*
Biological Transport
Cell Membrane / metabolism
Densitometry / methods
Epitopes / chemistry
Escherichia coli / enzymology*,  metabolism
Escherichia coli Proteins / chemistry*,  metabolism
Fatty Acids / chemistry*
Gene Expression Regulation, Bacterial
Gene Expression Regulation, Enzymologic
Lipids / chemistry*
Membrane Transport Proteins / chemistry*
Monosaccharide Transport Proteins / chemistry*,  metabolism
Phosphatidylethanolamines / chemistry
Protein Binding
Proteolipids / metabolism
Symporters / chemistry*,  metabolism
Grant Support
Reg. No./Substance:
0/Amines; 0/Epitopes; 0/Escherichia coli Proteins; 0/Fatty Acids; 0/LacY protein, E coli; 0/Lipids; 0/Membrane Transport Proteins; 0/Monosaccharide Transport Proteins; 0/Phosphatidylethanolamines; 0/Proteolipids; 0/Symporters; 0/proteoliposomes; 39382-08-6/phosphatidylethanolamine; 9068-45-5/lactose permease

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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