tailieunhanh - Báo cáo khoa học: A unique variant of streptococcal group O-antigen (C-polysaccharide) that lacks phosphocholine

Streptococcus mitisstrain SK598, which represents a sub-group of biovar 1, possesses a unique variant of the C-polysaccharide found in the cell wall of all strains of Streptococcus pneumoniaeand in some strains ofS. mitis. This newvariant lacks the cholinemethyl groups in contrast to the previously characterized forms of C-polysaccharide, whichall containone or two choline residues per repeat. The following structure of the repeating unit of the SK598 polysaccharide was established: where AAT is 2-acetamido-4-amino-2,4,6-trideoxy-D-galactose | Eur. J. Biochem. 270 2157-2162 2003 FEBS 2003 doi A unique variant of streptococcal group O-antigen C-polysaccharide that lacks phosphocholine Niklas Bergstrom1 Per-Erik Jansson1 Mogens Kilian2 and Uffe B. Skov Sorensen2 1 Clinical Research Centre Analytical Unit Karolinska Institute Huddinge Hospital Sweden 2Department of Medical Microbiology and Immunology University of Aarhus Denmark Streptococcus mitis strain SK598 which represents a subgroup of biovar 1 possesses a unique variant of the C-polysaccharide found in the cell wall of all strains of Streptococcus pneumoniae and in some strains of S. mitis. This new variant lacks the choline methyl groups in contrast to the previously characterized forms of C-polysaccharide which all contain one or two choline residues per repeat. The following structure of the repeating unit of the SK598 polysaccharide was established where AAT is 2-acetamido-4-amino-2 4 6-trideoxy-D-galactose. This structure is identical to the double choline-substi-tuted form of C--polysacchaiiclc. cxccpt that it is sLibsiitulcd with ethanolamine instead of choline. This extends the number of recognized C-polysaccharide variants to four. Keywords cell wall polysaccharide C-polysaccharide Streptococcus pneumoniae phosphocholine Streptococcus mitis. O -P-EtN O -P-EtN 4 4 6 6 6 -P-D-Glcp- lo3 -a-AATp- l- 4 -a-D-GalpNAc- lo3 -p-D-GalpNAc- lol -nbitol-5-P- Oo Previous serological analysis of the mitis group streptococci suggested that C-polysaccharide is a common antigen of Streptococcus pneumoniae and of most Streptococcus mitis biovar 1 strains. Different reaction patterns however emerged among the mitis group streptococci when examined by using a combination of two monoclonal antibodies in an enzyme linked immunoassay that recognize phosphocholine moieties and the backbone of C-polysaccharide respectively. Positive reactions with both monoclonals were interpreted as the presence of the classical C-polysaccharide with