Cell walls of Streptococcus pyogenes, type 14. C polysaccharide-peptidoglycan and G polysaccharide-peptidoglycan complexes

About 20% of the organic phosphorus present in cell walls of Streptococcus pyogenes occurs as N-acetylmuramic acid 6-phosphate residues (50 mµequiv/mg of walls). These groups link about 10% of the peptidoglycan subunits to a hitherto unrecognized polysaccharide. This polymer was isolated after degradation of trypsin-treated walls with Streptornyces F1 endo-N-acetylmuramidase; it consists of disaccharide peptide monomer (50 mµmoles/mg of walls) linked through a phosphodiester bridge to a polymer containing, per peptide monomer, five to six D-glucose residues, one glucosamine residue, and four to five unidentified hexosamine compounds. This polymer is designated as G polysaccharide.
About 70% of the organically bound phosphorus in the cell walls (150 mµequiv/mg of walls) is present in the form of phosphodiester groups in the interior of the rhamnose-containing C polysaccharide. The linkages of the C-polysaccharide chains to the peptidoglycan are visualized as bridges of trirhamnose groupings, each bearing one β-linked N-acetylgluco-samine residue, bound at the reducing end, either directly or through an as yet undetermined intervening molecule, to C-4 of an N-acetylmuramic acid residue. After degradation of walls by endo-N-acetylmurami-dase, the C-polysaccharide chains remain bound to one N-acetylmuramic acid residue. This N-acetylmur-amic acid residue is substituted by one tetrapeptide monomer which in turn is linked via a di-L-alanyl bridge to another disaccharide peptide monomer. A structure for the cell walls of Streptococcus pyogenes is proposed that takes into account all of the recognized covalent linkages among the constituent polymers.