Source:http://linkedlifedata.com/resource/pubmed/id/15659161
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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
2
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pubmed:dateCreated |
2005-1-20
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pubmed:abstractText |
Lipid A of Salmonella typhimurium is covalently modified with additional acyl and/or polar substituents in response to activation of the PhoP/PhoQ and/or PmrA/PmrB signalling systems, which are induced by growth at low Mg2+ concentrations and mild acid pH respectively. Although these conditions are thought to exist within macrophage phagolysosomes, no direct evidence for lipid A modification after endocytosis has been presented. To address this issue, we grew S. typhimurium inside RAW264.7 cells in the presence of 32Pi, and then isolated the labelled lipid A fraction, which was found to be extensively derivatized with phosphoethanolamine, aminoarabinose, 2-hydroxymyristate and/or palmitate moieties. S. typhimurium grown in tissue culture medium synthesized lipid A molecules lacking all these substituents with the exception of the 2-hydroxymyristate chain, which was still present. Using defined minimal media to simulate the intracellular pH and Mg2+ concentrations of endosomes, we found that lipid A of S. typhimurium grown in an acidic, low-Mg2+ medium closely resembled lipid A isolated from bacteria internalized by RAW264.7 cells. A subset of S. typhimurium lipid A modifications were induced by low Mg2+ alone. Escherichia coli K-12 W3110 modified its lipid A molecules in response to growth under acidic but not low-Mg2+ conditions. Growth in a high-Mg2+, mildly alkaline medium resulted in suppression of most lipid A modifications with the exception of the 2-hydroxymyristate in S. typhimurium. Although lpxO transcription was stimulated by growth on low Mg2+, the biosynthesis of lipid A species containing 2-hydroxymyristate was independent of PhoP/PhoQ and PmrA/PmrB in S. typhimurium. Our labelling methods should be applicable to studies of lipid A modifications induced by endocytosis of diverse bacteria.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
Jan
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pubmed:issn |
0950-382X
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
55
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
425-40
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:15659161-Animals,
pubmed-meshheading:15659161-Bacterial Proteins,
pubmed-meshheading:15659161-Cell Line,
pubmed-meshheading:15659161-Endocytosis,
pubmed-meshheading:15659161-Gene Expression Regulation, Bacterial,
pubmed-meshheading:15659161-Hydrogen-Ion Concentration,
pubmed-meshheading:15659161-Lipid A,
pubmed-meshheading:15659161-Macrophages,
pubmed-meshheading:15659161-Magnesium,
pubmed-meshheading:15659161-Mice,
pubmed-meshheading:15659161-Phosphorus Radioisotopes,
pubmed-meshheading:15659161-Salmonella
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pubmed:year |
2005
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pubmed:articleTitle |
Role of Mg2+ and pH in the modification of Salmonella lipid A after endocytosis by macrophage tumour cells.
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pubmed:affiliation |
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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