FIG. 4.

Muropeptides from E. faecalis JH2-2 and JH2-2ΔcroRS. (A) The most abundant muropeptides of both strains contained two d-Ala residues at the free C-terminal end and two l-Ala residues both at the free N-terminal end and in the cross-bridge (boxed). d-Glutamic acid is incorporated into the precursors and secondarily α-amidated (d-iGln, γ-d-glutaminyl residue). GlcNAc, N-acetylglucosamine; MurNAc, N-acetylmuramic acid. The orientation of the CO→NH peptide bonds is indicated by arrows. (B) Relative abundances of the major monomer, dimer, trimer, and tetramer. The totals include muropeptides of lesser abundance lacking the two C-terminal d-Ala residues and O-acetylated derivatives.