Chemical Structures of Streptococcus pneumoniae Capsular Polysaccharide Type 39 (CPS39), CPS47F, and CPS34 Characterized by Nuclear Magnetic Resonance Spectroscopy and Their Relation to

Structural characterization of Streptococcus pneumoniae capsular polysaccharides (CPS) is a prerequisite for unraveling both antigenic and genetic relationships that exist between different serotypes. In the current study, comparative structural studies of S. pneumoniae CPS serogroup 10 (CPS10) were extended to include genetically related S. pneumoniae CPS34, CPS39, and CPS47F. High-resolution heteronuclear nuclear magnetic resonance (NMR) spectroscopy confirmed the published structure of CPS34 and, in conjunction with glycosyl composition analyses, revealed the following repeat unit structures of the other sero-types, which have not been previously characterized: Common and unique structural features of these polysaccharides, including different positions of O-acetylation, were unambig-uously associated with specific genes in each corresponding cps locus. The only exception involved the gene designatedwcrC, which is associated with the1-2 transfer of Gal pyranoside (Galp) to ribitol-5-phosphate in the synthesis of CPS10A, CPS47F, and CPS34 but with1-1 transfer of Gal to ribitol-5-phosphate in the synthesis of CPS39. The corresponding gene in the cps39 locus, although related towcrC, more closely resembled a previously identified gene (i.e.,wefM) of Streptococcus oralis that is associated with1-1 transfer of Galp to ribitol-5-phosphate. These and other recent findings identify linkages from -Galp to ribitol-5-phosphate and from this residue to adjacent Gal furanoside (Galf) as important sites of CPS structural and genetic diversity. Streptococcus pneumoniae capsular polysaccharides (CPS) are ofinterest both as virulence factors and as protective immuno