A distinctive family of L,D-transpeptidases catalyzing L-Ala-mDAP crosslinks in Alpha- and Betaproteobacteria

Nat Commun. 2024 Feb 13;15(1):1343. doi: 10.1038/s41467-024-45620-5.


The bacterial cell-wall peptidoglycan is made of glycan strands crosslinked by short peptide stems. Crosslinks are catalyzed by DD-transpeptidases (4,3-crosslinks) and LD-transpeptidases (3,3-crosslinks). However, recent research on non-model species has revealed novel crosslink types, suggesting the existence of uncharacterized enzymes. Here, we identify an LD-transpeptidase, LDTGo, that generates 1,3-crosslinks in the acetic-acid bacterium Gluconobacter oxydans. LDTGo-like proteins are found in Alpha- and Betaproteobacteria lacking LD3,3-transpeptidases. In contrast with the strict specificity of typical LD- and DD-transpeptidases, LDTGo can use non-terminal amino acid moieties for crosslinking. A high-resolution crystal structure of LDTGo reveals unique features when compared to LD3,3-transpeptidases, including a proline-rich region that appears to limit substrate access, and a cavity accommodating both glycan chain and peptide stem from donor muropeptides. Finally, we show that DD-crosslink turnover is involved in supplying the necessary substrate for LD1,3-transpeptidation. This phenomenon underscores the interplay between distinct crosslinking mechanisms in maintaining cell wall integrity in G. oxydans.

MeSH terms

  • Bacteria
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Peptides / chemistry
  • Peptidoglycan / chemistry
  • Peptidyl Transferases* / chemistry
  • Polysaccharides


  • Peptidyl Transferases
  • Bacterial Proteins
  • Peptides
  • Polysaccharides
  • Peptidoglycan