Identification of the<scp>l,d</scp>-Transpeptidases for Peptidoglycan Cross-Linking in<i>Escherichia coli</i>

Abstract

Three active-site cysteine L,D-transpeptidases can individually anchor the Braun lipoprotein to the Escherichia coli peptidoglycan. We show here that two additional enzymes of the same family form peptide bonds between the third residues of peptidoglycan stems, generating meso-DAP(3)-->meso-DAP(3) unusual cross-links. This activity partially replaces the D,D-transpeptidase activity of penicillin-binding proteins.