Structure of the streptococcal groups A, A-variant and C carbohydrates

Structural studies on the Groups A, A-variant and C carbohydrates of β-hemolytic streptococci indicate that they have in common a polyrhamnose core. The A-variant carbohydrate consists solely of this polyrhamnose structure which has been shown to contain alternating α1, 2-and α1, 3-linked rhamnose units. In agreement with results first published by Heidelberger and his coworkers (Estrada-Parraet al., 1963), the Group A carbohydrate has been shown to containN-acetylgulcosamine residues attached to the 3-position of the 1, 2-linked rhamnose units in this polyrhamnose structure. TheseN-acetylglucosamine residues impart group-specificity to the Group A carbohydrate. The Group C carbohydrate differs from the Group A carbohydrate by having 3-O-α-N-acetylgalactosaminosyl-N-acetylgalactosamine units attached to the 3-position of the polyrhamnose structure. TheseN-acetylgalactosamine disaccharides are capable of inhibiting the binding of Group C carbohydrate to anti-Group C sera and are cross-reactive with the Forssman antigen.