Direction of Chain Extension during the Biosynthesis of Teichoic Acids in Bacterial Cell Walls

Abstract

RECENT developments in our knowledge of the biosynthesis of bacterial wall polymers include the recognition of the participation of lipid phosphates in the transfer of glycosyl residues from nucleoside diphosphate sugars to polysaccharide chains^1–4, the transfer of sugar l-phosphate residues from nucleotides into polymers⁵ and information on the direction of chain extension during biosynthesis^6,7. An interesting feature of studies on chain extension is the demonstration^6,8 that the polysaccharide chains of a bacterial lipopolysaccharide are built up on the polyisoprenoid pyrophosphate intermediates by the transfer of trisaccharide residues to the “reducing end” of the growing polymer, in a manner analogous to ammo-acid transfer in protein synthesis on ribosomes. This contrasts with glycogen biosynthesis where sugar residues are transferred to the “non-reducing ends” of chains, and with the biosynthesis of a teichoic acid of the poly(glycerol phosphate) type where glycerol phosphate units are transferred from CDP-glycerol to the glycerol-terminal end of the chain⁷.