The structure of the lipopolysaccharide (LPS) from three Neisseria meningitidis strains was elucidated. These strains were nonreactive with mAbs that recognize common inner-core epitopes from meningococcal LPS. It is well established that the inner core of meningococcal LPS consists of a diheptosyl-N-acetylglucosamine unit, in which the distal heptose unit (Hep II) can carry PEtn at the 3 or 6 position or not at all, and the proximal heptose residue (Hep I) is substituted at the 4 position by a glucose residue. Additional substitution at the 3 position of Hep II with a glucose residue is also a common structural feature in some strains. The structures of the O-deacylated LPSs and core oligosaccharides of the three chosen strains were deduced by a combination of monosaccharide analysis, NMR spectroscopy and MS. These analyses revealed the presence of a structure not previously identified in meningococcal LPS, in which an additional beta-configured glucose residue was found to substitute Hep I at the 2 position. This provided the structural basis for the nonreactivity of LPS with these mAbs. The determination of this novel structural feature identified a further degree of variability within the inner-core oligosaccharide of meningococcal LPS which may contribute to the interaction of meningococcal strains with their host.
Lipopolysaccharide, NMR, lipopolysaccharides, LPS, oligosaccharide, oligosaccharide structure, structure, common, core, heptose, Neisseria meningitidis, chemistry, growth & development, host, meningococcal, Neisseria, strain, structural, analysis, Research, degree, determination, epitope, Oligosaccharides, Carbohydrate Sequence, core oligosaccharide, immunology, Molecular Sequence Data, epitopes, MAb, NMR spectroscopy, spectrometry, biological, identification, position, inner core, Magnetic Resonance Spectroscopy, spectroscopy, interaction, glucose, MS, Carbohydrate Conformation, O-deacylated, monosaccharide, substitution, isolation & purification, Mass, monosaccharide analysis, Electrospray Ionization, variability
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The serotype d antigen of Actinobacillus actinomycetemcomitans consists of D-glucose, D-mannose, and L-rhamnose in a molar ratio of 1:2:1. A gene cluster involved in the synthesis of serotype-specific polysaccharide antigen was cloned from the chromosomal DNA of A. actinomycetemcomitans IDH 781 (serotype d). This cluster consisted of 12 open reading frames. Insertional inactivation of six genes in this cluster resulted in loss of ability of A. actinomycetemcomitans IDH 781 cells to produce the polysaccharide. Comparing the structure of the gene cluster with similar clusters from other serotypes of A. actinomycetemcomitans, showed that eight genes are unique to serotype d; the other four genes are involved in the biosynthesis of dTDP-L-rhamnose. These results suggest that the synthesis and structure of serotype d-specific polysaccharide of A. actinomycetemcomitans is quite different from those of other serotype strains.
synthesis, antigen, gene, polysaccharide, serotype, cluster, gene cluster, Actinobacillus, Actinobacillus actinomycetemcomitans, polysaccharide antigen, serotype antigen
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