Structure of the complex polysaccharide C-substance from Streptococcus pneumoniae type 1.

The complex cell-wall polysaccharide, C-substance, was isolated from Streptococcus pneumoniae type 1 and purified by DEAE-cellulose (HCO3(-) form) and Sephadex column chromatography. The complete structure of this antigen was obtained by the application of methylation and 1H NMR and 13C NMR spectroscopic techniques to a series of oligosaccharide fragments obtained by the selective degradation of the N-acetylated antigen. Native C-substance is composed of the following repeating unit: beta-D-Glup-1 leads to 3-alpha-AAT-Galp-1 leads to 4-alpha-D-GalNAcp-1 leads to 3-beta-D-GalNH2p-1 leads to 1'-ribitol-5-phosphate where AATGal is 2-acetamido-4-amino-2,4,6-trideoxygalactose. Phosphocholine substituents are situated at O(6) of the unacetylated galactosamine residues, and the repeating units are linked through a diphosphate ester from ribitol to O(6) of the beta-D-glucopyranose residue. This structure has also been shown to be common to C-substances prepared from a number of other pneumococcal types based on the criterion of their identical 13C NMR spectra.