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.

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. [ABSTRACT FROM AUTHOR]