The type II secretion system
The type II secretion system (T2SS) plays a role in infection, colonization and microbial communication processes. An important element of many of these systems is the secretin, a membrane protein that forms a pore on the bacterial surface allowing toxins to be translocated towards the environment. Using cryo electron microscopy, crystallography, and microbial genetics techniques, and in collaboration with the MEM group of the IBS and the University of Saskatchewan in Canada, we solved the structures (at approximately 3.5 Å resolution) of two secretins from the emerging pathogens Vibrio vulnificus and Aeromonas hydrophila.
Ribbon model and electrostatic surface of the secretin EpsD from V. vulnificus. The monomer is shown in orange (N-terminal) and red (C-terminal).
We characterized the mechanism for their assembly on the bacterial membrane. This work has shown that the assembly of some secretins requires the help of membrane lipo-proteins called "pilotins", while others are assembled independently (Howard et al., 2019). Since the secretin-pilotin interface is essential for the virulence of many pathogens, it could be an original target for the development of new inhibitors of infections caused by different bacteria.
The V. vulnificus pilotin EpsS recognizes the C-terminal helix of EpsD (red).
Howard SP, Estrozi L, Contreras-Martel C, Bertrand Q, Job V, Martins A, Schoehn G, Dessen A (2019). Structure and assembly of pilotin-dependent and -independent secretins of the Type II secretion system. PLoS Path. 15, e1007731.
Dortet L, Lombardi C, Cretin F, Dessen A, Filloux A (2018). Pore-forming activity of the Pseudomonas aeruginosa type III secretion system translocon alters the host epigenome. Nature Microbiol. 3, 378-386.
Tosi T, Estrozi LF, Job V, Guilvout I, Pugsley AP, Schoehn G, and Dessen A (2014). Structural similarity of secretins from type II and type III secretion systems. Structure 22, 1348-1355.
Gendrin C, Contreras-Martel C, Bouillot S, Elsen S, Lemaire D, Skoufias DA, Huber P, Attrée I, Dessen A (2012). Structural basis of cytotoxicity mediated by the type III secretion toxin ExoU from Pseudomonas aeruginosa. PLoS Pathog. e1002637.