title: Synergistic pore formation by type III toxin translocators of Pseudomonas aeruginosa.
abstract: Type III secretion/translocation systems are essential actors in the pathogenicity of Gram-negative bacteria. The injection of bacterial toxins across the host cell plasma membranes is presumably accomplished by a proteinaceous structure, the translocon. In vitro, Pseudomonas aeruginosa translocators PopB and PopD form ringlike structures observed by electron microscopy. We demonstrate here that PopB and PopD are functionally active and sufficient to form pores in lipid vesicles. Furthermore, the two translocators act in synergy to promote membrane permeabilization. The size-based selectivity observed for the passage of solutes indicates that the membrane permeabilization is due to the formation of size-defined pores. Our results provide also new insights into the mechanism of translocon pore formation that may occur during the passage of toxins from the bacterium into the cell. While proteins bind to lipid vesicles equally at any pH, the kinetics of membrane permeabilization accelerate progressively with decreasing pH values. Electrostatic interactions and the presence of anionic lipids were found to be crucial for pore formation whereas cholesterol did not appear to play a significant role in functional translocon formation.
authors.affiliation: Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (UMR 5092 CNRS/CEA/UJF), 17 rue des Martyrs, 38054 Grenoble Cedex 09, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Faudry
authors.forename: Grégory
authors.initials: G
authors.lastname: Vernier
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Neumann
authors.forename: Vincent
authors.initials: V
authors.lastname: Forge
authors.forename: Ina
authors.initials: I
authors.lastname: Attree
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry; D002463:Cell Membrane Permeability; D007700:Kinetics; D007956:Leukocidins / Q000737:chemistry*; D008081:Liposomes; D018272:Porins / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000737:chemistry*
chemical_list: D001427:Bacterial Toxins; D007956:Leukocidins; D008081:Liposomes; D018272:Porins