title: Structural similarity of secretins from type II and type III secretion systems.
abstract: Secretins, the outer membrane components of several secretion systems in Gram-negative bacteria, assemble into channels that allow exoproteins to traverse the membrane. The membrane-inserted, multimeric regions of PscC, the Pseudomonas aeruginosa type III secretion system secretin, and PulD, the Klebsiella oxytoca type II secretion system secretin, were purified after cell-free synthesis and their structures analyzed by single particle cryoelectron microscopy. Both homomultimeric, barrel-like structures display a "cup and saucer" architecture. The "saucer" region of both secretins is composed of two distinct rings, with that of PulD being less segmented than that of PscC. Both secretins have a central chamber that is occluded by a plug linked to the chamber walls through hairpin-like structures. Comparisons with published structures from other bacterial systems reveal that secretins have regions of local structural flexibility, probably reflecting their evolved functions in protein secretion and needle assembly.
authors.affiliation: Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 71 avenue des Martyrs, 38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Tosi
authors.affiliation: Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 71 avenue des Martyrs, 38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
authors.forename: Leandro F
authors.initials: LF
authors.lastname: Estrozi
authors.affiliation: Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 71 avenue des Martyrs, 38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
authors.forename: Viviana
authors.initials: V
authors.lastname: Job
authors.affiliation: Institut Pasteur, Molecular Genetics Unit, 25 rue du Docteur Roux, 75724 Paris, France; Centre National de la Recherche Scientifique (CNRS), ERL3526 Paris, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Guilvout
authors.affiliation: Institut Pasteur, Molecular Genetics Unit, 25 rue du Docteur Roux, 75724 Paris, France; Centre National de la Recherche Scientifique (CNRS), ERL3526 Paris, France.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Pugsley
authors.affiliation: Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 71 avenue des Martyrs, 38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France; Unit for Virus Host Cell Interactions UMI 3265 (UJF-EMBL-CNRS), 38027 Grenoble, France. Electronic address: schoehn@embl.fr.
authors.forename: Guy
authors.initials: G
authors.lastname: Schoehn
authors.affiliation: Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 71 avenue des Martyrs, 38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France; Brazilian National Laboratory for Biosciences (LNBio), CNPEM, 13083 Campinas, Brazil. Electronic address: andrea.dessen@ibs.fr.
authors.forename: Andréa
authors.initials: A
authors.lastname: Dessen
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure; D058947:Bacterial Secretion Systems; D020285:Cryoelectron Microscopy; D041121:Klebsiella oxytoca / Q000737:chemistry; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D011550:Pseudomonas aeruginosa / Q000737:chemistry; D012633:Secretin / Q000737:chemistry*; D040681:Structural Homology, Protein
chemical_list: D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D012633:Secretin