Structural analysis of the O-antigen polysaccharide from Escherichia coli O188

• Published in: Carbohydrate research 2020-12, Vol.498, p.108051-108051, Article 108051
• Main Authors: Furevi, Axel, Ståhle, Jonas, Muheim, Claudio, Gkotzis, Spyridon, Udekwu, Klas I., Daley, Daniel O., Widmalm, Göran
• Format: Article
• Language: English
• Subjects: Escherichia coli; Lipopolysaccharide; NMR spectroscopy; Shigella boydii
• ISSN: 0008-6215; 1873-426X; 1873-426X
• DOI: 10.1016/j.carres.2020.108051

The structure of the O-antigen from Escherichia coli reference strain O188 (E. coli O188:H10) has been investigated. The lipopolysaccharide shows a typical nonrandom modal chain-length distribution and the sugar and absolute configuration analysis revealed d-Man, d-Glc, d-GlcN and d-GlcA as major components. The structure of the O-specific polysaccharide was determined using one- and two-dimensional 1H and 13C NMR spectroscopy experiments, where inter-residue correlations were identified by 1H,13C-heteronuclear multiple-bond correlation and 1H,1H-NOESY experiments, which revealed that it consists of pentasaccharide repeating units with the following structure: ▪Biosynthetic aspects and NMR analysis are consistent with the presented structure as the biological repeating unit. The O-antigen of Shigella boydii type 16 differs only in that it carries O-acetyl groups to ~50% at O6 of the branch-point mannose residues. A molecular model of the E. coli O188 O-antigen containing 20 repeating units extends ~100 Å, which is similar to the height of the periplasmic portion of polysaccharide co-polymerase Wzz proteins that regulate the O-antigen chain length of lipopolysaccharides in the Wzx/Wzy biosynthetic pathway. [Display omitted] •E. coli O188 O-antigen contains pentasaccharide repeating units.•S. boydii type 16 O-antigen is in addition O-acetylated.•Molecular models of the O-antigens identify epitopes that are different.