High-resolution NMR spectroscopic analysis of the C-polysaccharide of Streptococcus pneumoniae

The complete structure of the complex cell-wall C-polysaccharide from Streptococcus pneumoniae R36A was elucidated using a combination of high-resolution NMR spectroscopy and theoretical calculations. The C-polysaccharide is composed of the following repeating unit β-D-Glcp1 → 3-α-D-AATp1 → 4-α-D-GalpNAc1 → 3-β-D-GalpNAc1 → 1-ribitol-5-phosphate where AAT is 2-acetamido-4-amino-2,4,6-trideoxygalactopyranoside. The C-polysaccharide contains two phosphorylcholine substituents per repeating unit, which are situated on O-6 of each of the two 2-acetamido-2-deoxy-galactopyranose residues. The repeating units are linked through a diphosphate ester from ribitol to O-6 of the β-D-glucopyranosyl residue.