title: The assembly mode of the pseudopilus: a hallmark to distinguish a novel secretion system subtype.
abstract: In gram-negative bacteria, type II secretion systems assemble a piston-like structure, called pseudopilus, which expels exoproteins out of the cell. The pseudopilus is constituted by a major pseudopilin that when overproduced multimerizes into a long cell surface structure named hyper-pseudopilus. Pseudomonas aeruginosa possesses two type II secretion systems, Xcp and Hxc. Although major pseudopilins are exchangeable among type II secretion systems, we show that XcpT and HxcT are not. We demonstrate that HxcT does not form a hyper-pseudopilus and is different in amino acid sequence and multimerization properties. Using structure-based mutagenesis, we observe that five mutations are sufficient to revert HxcT into a functional XcpT-like protein, which also becomes capable of forming a hyper-pseudopilus. Phylogenetic and experimental analysis showed that the whole Hxc system was acquired by P. aeruginosa PAO1 and other Pseudomonas species through horizontal gene transfer. We thus identified a new type II secretion subfamily, of which the P. aeruginosa Hxc system is the archetype. This finding demonstrates how similar bacterial machineries evolve toward distinct mechanisms that may contribute specific functions.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM-UPR9027), CNRS, Université de la Méditerranée, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Durand
authors.forename: Sébastien
authors.initials: S
authors.lastname: Alphonse
authors.forename: Céline
authors.initials: C
authors.lastname: Brochier-Armanet
authors.forename: Geneviève
authors.initials: G
authors.lastname: Ball
authors.forename: Badreddine
authors.initials: B
authors.lastname: Douzi
authors.forename: Alain
authors.initials: A
authors.lastname: Filloux
authors.forename: Cédric
authors.initials: C
authors.lastname: Bernard
authors.forename: Romé
authors.initials: R
authors.lastname: Voulhoux
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000502:physiology*; D019143:Evolution, Molecular; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism; D022761:Gene Transfer, Horizontal / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems