Structure and Modifications of Pseudomurein in Methano-bacleriales

Pseudomurein, the cell wall polymer found in all species of the order Methanobacteriales, is composed of glycan strands cross-linked by peptide subunits. The glycan strands are composed of alternating N-acetyl-D-glucosamine or N-acetyl-D-galactosamine and N-acetyl-D-talosaminuronic acid residues in β-1.3-linkage. In most species the cross-linking peptide subunits consist of alanine, glutamic acid and lysine. However, alanine is completely or partly replaced by threonine in Methanobrevibacter ruminantium. In Methano-brevibacter smithii ornithine was found as an additional amino acid residue attached by its (δ-amino group to the α-carboxyl group of the terminal glutamyl residue.