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Covalent modifications of Salmonella lipid A :Roles of macrophages, media, and a membrane-bound hydroxylase.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Covalent modifications of Salmonella lipid A :
其他題名:	Roles of macrophages, media, and a membrane-bound hydroxylase.
作者:	Gibbons, Henry Sanford.
面頁冊數:	257 p.
附註:	Adviser: Christian R. H. Raetz.
附註:	Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4915.
Contained By:	Dissertation Abstracts International64-10B.
標題:	Chemistry, Biochemistry.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3109006
ISBN:	0496565516

Covalent modifications of Salmonella lipid A :Roles of macrophages, media, and a membrane-bound hydroxylase.
Gibbons, Henry Sanford.

Covalent modifications of Salmonella lipid A :Roles of macrophages, media, and a membrane-bound hydroxylase. [electronic resource] - 257 p.

Adviser: Christian R. H. Raetz.

Thesis (Ph.D.)--Duke University, 2003.

A S. typhimurium strain lacking lpxO was generated and shown to lack 2-hydroxymyristate groups in its lipid A. LpxO was overexpressed in E. coli and shown to be localized to the membrane fraction. Kdo2-[4'- 32P]-lipid A, a novel, highly radioactive endotoxin analogue, was shown in vitro to be a substrate for LpxO. The enzymatic activity localized to the membrane fraction as well. The continued formation of 2-hydroxymyristate in lipid A in an E. coli mutant carrying a temperature-sensitive mutation in msbA demonstrated that the active site of LpxO faces the cytoplasm. The product of the LpxO reaction was confirmed by mass spectrometry.

ISBN: 0496565516Subjects--Topical Terms:

226900
Chemistry, Biochemistry.

Covalent modifications of Salmonella lipid A :Roles of macrophages, media, and a membrane-bound hydroxylase.
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520 # $a A S. typhimurium strain lacking lpxO was generated and shown to lack 2-hydroxymyristate groups in its lipid A. LpxO was overexpressed in E. coli and shown to be localized to the membrane fraction. Kdo2-[4'- 32P]-lipid A, a novel, highly radioactive endotoxin analogue, was shown in vitro to be a substrate for LpxO. The enzymatic activity localized to the membrane fraction as well. The continued formation of 2-hydroxymyristate in lipid A in an E. coli mutant carrying a temperature-sensitive mutation in msbA demonstrated that the active site of LpxO faces the cytoplasm. The product of the LpxO reaction was confirmed by mass spectrometry.
520 # $a A sensitive radiochemical method was developed to study lipid A modifications of S. typhimurium residing inside RAW264.7 macrophage-like tumour cells. Bacteria residing intracellularly extensively modified lipid A with aminoarabinose, phosphoethanolamine, 2-hydroxymyristate, and palmitate. Bacteria grown in vitro in low-Mg2+ conditions at pH 6.0 made modified lipid A species that resembled those made by intracellular bacteria. E. coli K-12 also modifies lipid A when grown in acidic conditions.
520 # $a Hydroxylation of lipid A was sensitive in vivo to fluctuating levels of Fe2+ and Mn2. In otherwise unsupplemented, high Mg2+ minimal medium, submicromolar Mn2+ suppressed the formation of 2-hydroxymyristate in S. typhimurium. Other divalent metals did not affect lipid A hydroxylation. The effect of Mn2+ was not due to transcriptional repression, since lpxO was induced by low Mg2+ and PhoP/PhoQ. However, lipid A hydroxylation was also stimulated by supplementation of the medium with Fe2+. It is likely that Fe2+ and Mn 2+ compete in vivo for the active site of LpxO.
520 # $a Lipid A of Salmonella typhimurium is modified in a PhoP/PhoQ-dependent manner with numerous covalent modifications, which include 2-hydroxymyristate, aminoarabinose, phosphoethanolamine, and palmitate. The 2-hydroxymyristate moiety replaces the myristate normally found in acyloxyacyl linkage to the 3'-O-linked fatty acid of lipid A. Biosynthesis of 2-hydroxymyristate is dependent on O2; bacteria grown anaerobically lack 2-hydroxymyristate, the 2-hydroxyl group is derived from O2. The lpxO gene of S. typhimurium, a homologue of mammalian aspartyl/asparaginyl beta-hydroxylase, can induce the formation of 2-hydroxymyristate in the lipid A of E. coli, which normally lacks this fatty acid.
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