Structure and characterization of the gene cluster of the O-antigen of Escherichia coli O49 containing 4,6-dideoxy-4-[(S-3-hydroxybutanoylamino]-D-glucose
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An O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of enteropathogenic Escherichia coli O49 and studied by sugar analysis along with one- and two-dimensional 1H- and 13C-NMR spectroscopy. The following structure of the linear tetrasaccharide repeating unit of the O-polysaccharide was established:
where d-Qui4N(S3HOBut) stands for 4,6-dideoxy-4-[(S)-3-hydroxybutanoylamino]-d-glucose and O-acetylation of GlcNAc is partial (∼30%). To our knowledge, no N-(3-hydroxybutanoyl) derivative of Qui4N has been hitherto found in bacterial polysaccharides. Gene functions of the O-antigen gene cluster of E. coli O49 were assigned by bioinformatics analysis and found to correspond to the O-polysaccharide structure. Two new genes were revealed and suggested to be responsible for synthesis and transfer of the 3-hydroxybutanoyl group.
$$ \to 2) - \alpha - D - Quip4N(S3HOBut) - (1 \to 4) - \beta - D - GalpNAc - (1 \to 4) - \alpha - L - Rhap - (1 \to 3) - \beta - D - GlcpNAc6Ac - (1 \to , $$
Key wordsEscherichia coli lipopolysaccharide bacterial polysaccharide structure 3-hydroxybutyrate 4-amino-4,6-dideoxy-d-glucose O-antigen gene cluster
© MAIK Nauka 2008