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

• Published in: PloS one Vol. 16; no. 7; p. e0254232
• Main Authors: Nguyen, Van Son, Spinelli, Silvia, Cascales, Éric, Roussel, Alain, Cambillau, Christian, Leone, Philippe
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 02.07.2021; Public Library of Science (PLoS)
• Subjects: Analysis; Bacteria; Binding sites; Biology and Life Sciences; Cell walls; Chromatography; Crystal structure; Crystallization; Crystals; Data collection; Domains; Gram-negative bacteria; Life Sciences; Medicine and Health Sciences; Peptidoglycans; Physical Sciences; Protein binding; Proteins; Structure; Virulence; Virulence factors; France; Molecular structure; Cell walls; Peptidoglycans; Outer membrane proteins; Sequence alignment; DNA cloning; Secretion systems; Crystal structure
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0254232

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.