Structure of the type IX Group B Streptococcus capsular polysaccharide and its evolutionary relationship with types V and VII [Genomics and Proteomics]

July 2nd, 2014 by Berti, F., Campisi, E., Toniolo, C., Morelli, L., Crotti, S., Rosini, R., Romano, M. R., Pinto, V., Brogioni, B., Torricelli, G., Janulczyk, R., Grandi, G., Margarit, I.

The Group B Streptococcus capsular polysaccharide type IX was isolated and purified, and the structure of its repeating unit determined. Type IX capsule {→4)[NeupNAc-α-(2→3)-Galp-β-(1→4)-GlcpNAc-β-(1→6)]-β-GlcpNAc-(1→4)-β-Galp-(1→4)-β-Glcp-(1→} appears most similar to types VII and V, although it contains two GlcpNAc residues. Genetic analysis identified differences in cpsM, cpsO and cpsI gene sequences as responsible for the differentiation between the three capsular polysaccharide types, leading us to hypothesize that type V emerged from a recombination event in a type IX background.
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