PT  - JOURNAL ARTICLE
AU  - Henri Voedts
AU  - Delphine Dorchêne
AU  - Adam Lodge
AU  - Waldemar Vollmer
AU  - Michel Arthur
AU  - Jean-Emmanuel Hugonnet
TI  - Role of endopeptidases in peptidoglycan synthesis mediated by alternative cross-linking enzymes in <em>Escherichia coli</em>
AID  - 10.1101/2021.02.12.430937
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.02.12.430937
4099  - http://biorxiv.org/content/early/2021/02/25/2021.02.12.430937.short
4100  - http://biorxiv.org/content/early/2021/02/25/2021.02.12.430937.full
AB  - Bacteria resist to the turgor pressure of the cytoplasm through a net-like macromolecule, the peptidoglycan, made of glycan strands connected via peptides cross-linked by penicillin-binding proteins (PBPs). We recently reported the emergence of β-lactam resistance resulting from a bypass of PBPs by the YcbB L,D-transpeptidase (LdtD), which form chemically distinct 3→3 cross-links compared to 4→3 formed by PBPs. Here we show that peptidoglycan expansion requires controlled hydrolysis of cross-links and identify amongst eight endopeptidase paralogues the minimum enzyme complements essential for bacterial growth with 4→3 (MepM) and 3→3 (MepM and MepK) cross-links. Purified Mep endopeptidases unexpectedly displayed a 4→3 and 3→3 dual specificity implying recognition of a common motif in the two cross-link types. Uncoupling of the polymerization of glycan chains from the 4→3 cross-linking reaction was found to facilitate the bypass of PBPs by YcbB. These results illustrate the plasticity of the peptidoglycan polymerization machinery in response to the selective pressure of β-lactams.Competing Interest StatementThe authors have declared no competing interest.