Conformational and topological aspects of the three-dimensional architecture of bacterial peptidoglycan.

An atomic model of the conformation of peptidoglycan was taken as the basis for an analysis of packing patterns of the peptidoglycan strands in two- and three-dimensional arrangements. For the sake of clarity, glycan strands were approximated by cylindrical rods around which a continuous helix of possible peptide cross-linkage sites was arranged. Using the packing patterns obtained, several important properties of the murein network could be explained. These include variations in the degree of cross-linking in Gram-negative and Gram-positive bacteria and an estimation of the number of peptide monomers, di/trimers and oligomers present. Furthermore, our model is compatible with the well known flexibility of the murein fabric and the distinct elastic properties of the cell wall in gram-positive cocci and rod-shaped bacteria.