FIG. 3.

Peptidoglycan assembly. The cytoplasmic steps leading to the prenylated disaccharide pentapeptide (lipid II) are shown. Through the action of a hypothetical flippase, the disaccharide pentapeptide becomes exposed to the periplasm. The membrane-bound disaccharide peptide becomes attached to a polymer that is also membrane bound. Glycan chain elongation occurs by transglycosylation. Elongation can occur at the nonreducing end of the glycan chain (this figure) or at the reducing end (not shown). G, N-acetylglucosamine; M, N-acetylmuramic acid; P, undecaprenylphosphate; PP, undecaprenyl biphosphate; pep, pentapeptide. Modified from reference 161 with permission from the American Society for Microbiology.