Fig. 1: Space-filling model of carbohydrate structures.

A GAC and (B) A Variant carbohydrate as modelled by Glycam76. Both structures have 18 repeats of the rhamnose disaccharide core - the average size of GAC isolated from GAS15. Both have the β(1, 4)linked GlcNAc that anchors the GAC to the peptidoglycan matrix77. The GAC structure is dominated by the GlcNAc linked to the core rhamnoses, Eight of the 18 GlcNAc in this structure are labelled. The green ellipse outlines one of the ~17 high affinity epitopes in this GAC identified using mAbs and other studies. It comprises 4 contiguous rhamnoses with 2 GlcNAc sidechains35. Not shown on the GAC are the glycerol phosphate attachments to some but not all GlcNAc sidechains78.