Anchoring the T6SS to the cell wall: Crystal structure of the peptidoglycan binding domain of the TagL accessory protein

PLoS One. 2021 Jul 2;16(7):e0254232. doi: 10.1371/journal.pone.0254232. eCollection 2021.


The type VI secretion system (T6SS) is a widespread mechanism of protein delivery into target cells, present in more than a quarter of all sequenced Gram-negative bacteria. The T6SS constitutes an important virulence factor, as it is responsible for targeting effectors in both prokaryotic and eukaryotic cells. The T6SS comprises a tail structure tethered to the cell envelope via a trans-envelope complex. In most T6SS, the membrane complex is anchored to the cell wall by the TagL accessory protein. In this study, we report the first crystal structure of a peptidoglycan-binding domain of TagL. The fold is conserved with members of the OmpA/Pal/MotB family, and more importantly, the peptidoglycan binding site is conserved. This structure further exemplifies how proteins involved in anchoring to the cell wall for different cellular functions rely on an interaction network with peptidoglycan strictly conserved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Cell Wall / metabolism*
  • Gram-Negative Bacteria / metabolism
  • Peptidoglycan / metabolism*
  • Protein Domains / physiology*
  • Type VI Secretion Systems / metabolism*
  • Virulence Factors / metabolism


  • Bacterial Proteins
  • Peptidoglycan
  • Type VI Secretion Systems
  • Virulence Factors

Grants and funding

This work was funded by the Centre National de la Recherche Scientifique (CNRS), the Aix-Marseille Université and a grant from the Agence Nationale de la Recherche (ANR-14-CE14-0006-02) and the French Infrastructure for Integrated Structural Biology (FRISBI). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.