Structural studies and biosynthetic aspects of the O-antigen polysaccharide from Escherichia coli O42

• Published in: Carbohydrate research Vol. 403; pp. 174 - 181
• Main Authors: Fontana, Carolina, Weintraub, Andrej, Widmalm, Göran
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 11-02-2015
• Subjects: Carbohydrate Sequence; Escherichia coli; Escherichia coli - metabolism; Magnetic Resonance Spectroscopy; Medicin och hälsovetenskap; Molecular Sequence Data; NMR; O Antigens - biosynthesis; O Antigens - chemistry; O-Acetylation; O-Antigen; O-Acetylation; O-Antigen; NMR; Escherichia coli
• ISSN: 0008-6215; 1873-426X; 1873-426X
• DOI: 10.1016/j.carres.2014.05.003

•The O-antigen polysaccharides of E. coli O28ac and O42 share the same trisaccharide–glycerol backbone.•Dephosphorylation with aqueous 48% hydrogen fluoride resulted in an oligosaccharide, which was sequenced by MS/MS.•The stereogenic center in the glycerol moiety is predicted to have the R configuration based on NMR and genetic data.
The structure of the O-antigen polysaccharide (PS) from Escherichia coli O42 has been investigated by NMR spectroscopy as the main method, which was complemented with sugar analysis, mass spectrometry, and analysis of biosynthetic information. The O-specific chain of the O-deacylated lipopolysaccharide (LPS-OH) consists of branched tetrasaccharide–glycerol repeating units joined by phosphodiester linkages. The lipid-free polysaccharide contains 0.8equiv of O-acetyl groups per repeating unit and has the following teichoic acid-like structure: Based on biosynthetic aspects, this should also be the biological repeating unit. This O-antigen structure is remarkably similar to that of E. coli O28ac, differing only in the presence or absence, respectively, of a glucose residue at the branching point. The structural similarity explains the serological cross-reactivity observed between strains of these two serogroups, and also their almost identical O-antigen gene cluster sequences. [Display omitted]