Structural elucidation of the major Hex4 lipopolysaccharide glycoform from the lgtC mutant of Haemophilus influenzae strain Eagan

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• 作者：Hussein Masoud ; E. Richard Moxon ; James C. Richards
• 关键词：Haemophilus influenzae ; Lipopolysaccharide ; Structural analysis ; lgtC mutant
• 刊名：Carbohydrate Research
• 出版年：2008
• 出版时间：7 July 2008
• 年：2008
• 卷：343
• 期：9
• 页码：1424-1434
• 全文大小：449 K

文摘

Lipopolysaccharide (LPS) oligosaccharide epitopes are major virulence factors of Haemophilus influenzae. The structure of LPS glycoforms of H. influenzae type b strain Eagan containing a mutation in the gene lgtC is investigated. LgtC is involved in the biosynthesis of globoside trisaccharide [-d-Galp-(1→4)-β-d-Galp-(1→4)-β-d-Glcp-(1→], an LPS epitope implicated in the virulence of this organism. Glycose and methylation analyses provided information on the composition while electrospray ionization mass spectrometry (ESI-MS) on O-deacylated LPS (LPS-OH) indicated the major glycoform to contain 4 hexoses attached to the common H. influenzae triheptosyl inner-core unit. The structure of the Hex4 glycoform in LPS-OH and core oligosaccharide samples was determined by NMR. It consists of an l--d-HepIIIp-(1→2)-[PEtn→6]-l--d-HepIIp-(1→3)-l--d-HepIp-(1→5)-[P→4]--d-Kdop-(2→ to which a β-d-Glcp-(1→4)--d-Glcp disaccharide unit is extended from HepII at the C-3 position, while HepI and HepIII are substituted at the C-4 and C-2 positions with β-d-Glcp and β-d-Galp, respectively. This structure corresponds to that expressed as a subpopulation in the parent strain. ³¹P NMR studies permitted the identification of subpopulations of LPS containing Kdo substituted at the C-4 position with monophosphate or pyrophosphoethanolamine (PPEtn). HepIII was found to be substituted with either phosphate at the C-4 position or acetate at the C-3 position, but not both of them together in the same subpopulation. The subpopulations containing phosphate and acetate at HepIII and their location have not previously been reported.