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. Author manuscript; available in PMC: 2008 Oct 17.
Published in final edited form as: Annu Rev Biochem. 2001 Nov 9;71:635–700. doi: 10.1146/annurev.biochem.71.110601.135414

Figure 13. Biosynthesis and assembly of O polysaccharides in a Wzy-dependent pathway.

Figure 13

Panel A shows the sequence of reactions involved in the formation of the undecaprenyl-linked repeat units and their polymerization in S. enterica serovar Typhimurium. The individual glycosyltransferase enzymes are identified in green enzymes are identified in the boxes and structural details are presented elsewhere (2, 9). Panel B shows a model for the events in polymerization. Individual undecaprenyl-linked O-repeat units are transferred across the membrane by a process involving Wzx (yellow). These intermediates provide the substrates for the putative polymerase (Wzy- identified in blue) acting in the periplasm. Chain extension occurs at the reducing terminus with the nascent chain being transferred from its undecaprenyl carrier to the non-reducing terminus of the “new” undecaprenyl-linked subunit. The chain-length modality (i.e. the extent of polymerization) is determined by Wzz (also in blue). The nascent polymer is then ligated to lipid A-core and translocated to the outer membrane.