FIG 1.

Overview of the different LDT family members. E. coli has six proteins with a YkuD (LDT) domain (top left). Protein regions: S, signal peptide; LysM and PGB, peptidoglycan-binding domains. The numbers indicate amino acid positions. Sequence alignment within the YkuD domain (bottom left) shows the active site cysteine (C, in red) and other conserved amino acid residues in gray. DpaA (LdtF) misses a conserved arginine (R), and its function is unknown. On the right side, it can be seen that LdtA, LdtB, and LdtC attach Lpp to meso-Dpm in PG stem peptides. LdtD and presumably LdtE form 3-3 cross-links in PG. l-Ala, l-alanine; d-Glu, d-glutamic acid; d-Ala, d-alanine; meso-Dpm, meso-diaminopimelic acid.