Structural determination of the O-antigenic polysaccharide from the verocytotoxin-producing Escherichia coli O176

• The structure of the O-antigen polysaccharide (PS) from Escherichia coli O176 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy was employed to elucidate the structure. Inter-residue correlations were determined by H-1,H-1 NOESY and H-1, C-13 heteronuclear multiple-bond correlation experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-alpha-D-Manp-(1 -> 2)-alpha-D-Manp-(1 -> 2)-beta-D-Manp-(1 -> 3)-alpha-D-GalpNAc-(-> Cross-peaks of low intensity from alpha-linked mannopyranosyl residues were present in the H-1, H-1 TOCSY NMR spectra and further analysis of these showed that they originate from the terminal part of the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end. The repeating unit of the E coli O176 O-antigen is similar to those from E coli 017 and 077, thereby explaining the reported cross-reactivities between the strains, and identical to that of Salmonella cerro (O:6, 14, 18).

Ämnesord

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

Nyckelord

Escherichia coli

Salmonella cerro

Lipopolysaccharide

NMR

Biological repeating unit

Organic chemistry

Organisk kemi

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