STRUCTURAL BASIS OF GROUP G STREPTOCOCCAL ANTIGENICITY

Samples of streptococcal group G antigenic cell-wall polysaccharide extracted by different methods were analyzed for their carbohydrate content and tested for serological reactivity. On the basis of inhibition of group G-specific precipitation by various l-rhamnose derivatives, as well as by methylation analysis of the polysaccharide, it was concluded that the serologically determinant l-rhamnosyl residues were in α-1,4-linkages to the penultimate residues in the G polysaccharide chains. Studies of streptococcal group B precipitation by its homologous antisera, using the same l-rhamnose derivatives as inhibitors, led to the tentative conclusion that its serologically determinant l-rhamnosyl-residues are in α-1,2-linkage with the rhamnose chains in group B polysaccharide. The inhibition of groups B and G precipitation by other streptococcal polysaccharides suggested that cell wall polysaccharides of groups A, A Variant, C, E, and H contain α-1,3-linked terminal rhamnose units; that groups G, F, and K are α-1,4-linked; and that group B polysaccharide is unique among those tested in containing α-1,2-inter-rhamnosyl-linkages. © 1969.