Structural elucidation of the O-antigenic polysaccharide from enterohemorrhagic (EHEC) Escherichia coli O48:H21

The structure of the antigenic O-polysaccharide (O-PS) of the lipopolysaccharide (LPS) produced by the enterohemorrhagic strain of Escherichia coli O48:H21 (EHEC) has been elucidated. The O-PS obtained by mild acid hydrolysis of the LPS had [α]D +95 (water) and was composed of l-rhamnose (l-Rha), d-galactose (d-Gal), 2-amino-2-deoxy-d-glucose (d-GlcN), 2-amino-2-deoxy-d-galactose (d-GalN), and d-galacturonic acid (d-GalA) (1:1:1:1:1). From the results of methylation analysis, mass spectrometry, 2D NMR, and DOC-PAGE, the O-PS was shown to be a high molecular mass polymer of a repeating pentasaccharide unit having the structure:Figure optionsDownload as PowerPoint slideThe d-GalpA non-reducing end groups in the O-PS were partially O-acetylated (∼30%) at the O-2 and O-3 positions and the degree of acetylation was variable from batch to batch cell production.

Figure optionsDownload as PowerPoint slide