title: Type II protein secretion in Pseudomonas aeruginosa: the pseudopilus is a multifibrillar and adhesive structure.
abstract: The type II secretion pathway of Pseudomonas aeruginosa is involved in the extracellular release of various toxins and hydrolytic enzymes such as exotoxin A and elastase. This pathway requires the function of a macromolecular complex called the Xcp secreton. The Xcp secreton shares many features with the machinery involved in type IV pilus assembly. More specifically, it involves the function of five pilin-like proteins, the XcpT-X pseudopilins. We show that, upon overexpression, the XcpT pseudopilin can be assembled in a pilus, which we call a type II pseudopilus. Image analysis and filtering of electron micrographs indicated that these appendages are composed of individual fibrils assembled together in a bundle structure. Our observations thus revealed that XcpT has properties similar to those of type IV pilin subunits. Interestingly, the assembly of the type II pseudopilus is not exclusively dependent on the Xcp machinery but can be supported by other similar machineries, such as the Pil (type IV pilus) and Hxc (type II secretion) systems of P. aeruginosa. In addition, heterologous pseudopilins can be assembled by P. aeruginosa into a type II pseudopilus. Finally, we showed that assembly of the type II pseudopilus confers increased bacterial adhesive capabilities. These observations confirmed the ability of pseudopilins to form a pilus structure and raise questions with respect to their function in terms of secretion and adhesion, two crucial biological processes in the course of bacterial infections.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Unité Propre de Recherche 9027, Institut de Biologie Structurale et Microbiologie/Centre National de la Recherche Scientifique, 13402 Marseille Cedex 20, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Durand
authors.forename: Alain
authors.initials: A
authors.lastname: Bernadac
authors.forename: Geneviève
authors.initials: G
authors.lastname: Ball
authors.forename: Andrée
authors.initials: A
authors.lastname: Lazdunski
authors.forename: James N
authors.initials: JN
authors.lastname: Sturgis
authors.forename: Alain
authors.initials: A
authors.lastname: Filloux
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D011550:Pseudomonas aeruginosa / Q000378:metabolism* / Q000648:ultrastructure; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C082104:XcpT protein, Pseudomonas aeruginosa; D036781:Fimbriae Proteins