Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain Escherichia coli O82 |
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Authors: | Samuel Vilchez Magnus Lundborg Andrej Weintraub |
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Institution: | a Department of Microbiology, Faculty of Medical Sciences, National Autonomous University of Nicaragua (UNAN) León, Nicaragua b Karolinska Institute, Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska University Hospital, S-141 86 Stockholm, Sweden c Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden d Department of Physiological Sciences, Division of Biochemistry, National Autonomous University of Nicaragua (UNAN) León, Nicaragua |
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Abstract: | The structure of the O-antigen polysaccharides (PS) from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain E. coli O82 have been determined. Component analysis and 1H, 13C, and 31P NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by 1H, 13C-heteronuclear multiple-bond correlation, and 1H, 1H-NOESY experiments. d-GroA as a substituent is linked via its O-2 in a phosphodiester-linkage to O-6 of the α-d-Glcp residue. The PS is composed of tetrasaccharide repeating units with the following structure:→4)-α-d-Glcp6-(P-2-d-GroA)-(1→4)-β-d-Galp-(1→4)-β-d-Glcp-(1→3)-β-d-GlcpNAc-(1→Cross-peaks of low intensity from an α-d-Glcp residue were present in the NMR spectra and spectral analysis indicates that they originate from the terminal residue of the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-d-glucosamine residue at its reducing end. Enzyme immunoassay using specific anti-E. coli O82 rabbit sera showed identical reactivity to the LPS of the two strains, in agreement with the structural analysis of their O-antigen polysaccharides. |
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Keywords: | Escherichia coli Lipopolysaccharide NMR Biological repeating unit Glyceric acid |
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