Structural determination of the O-antigenic polysaccharide from the Shiga toxin-producing Escherichia coli O171

The structure of the O-antigenic part of the lipopolysaccharide (LPS) obtained from the verotoxin-producing Escherichia coli O171 has been determined. 1H and 13C NMR spectroscopy techniques in combination with component analysis were used to elucidate the O-antigen structure of O-deacylated LPS. Subsequent NMR analysis of the native LPS revealed acetylation at O-7/O-9 of the sialic acid residue. The sequence of sugars was determined by inter-residue correlations in 1H,1H-NOESY and 1H,13C-heteronuclear multiple-bond correlation spectra. The O-antigen is composed of pentasaccharide repeating units with one equivalent of O-acetyl groups distributed over two positions:Based on biosynthetic considerations, this should also be the biological repeating unit.

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