title: Structural insights into the assembly of the type III secretion needle complex.
abstract: Type III secretion systems (TTSSs) mediate translocation of virulence factors into host cells. We report the 17-angstrom resolution structures of a central component of Salmonella typhimurium TTSS, the needle complex, and its assembly precursor, the bacterial envelope-anchored base. Both the base and the fully assembled needle complex adopted multiple oligomeric states in vivo, and needle assembly was accompanied by recruitment of the protein PrgJ as a structural component of the base. Moreover, conformational changes during needle assembly created scaffolds for anchoring both PrgJ and the needle substructure and may provide the basis for substrate-specificity switching during type III secretion.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520-8024, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Marlovits
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kubori
authors.forename: Anand
authors.initials: A
authors.lastname: Sukhan
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Thomas
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Galán
authors.forename: Vinzenz M
authors.initials: VM
authors.lastname: Unger
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D046911:Macromolecular Substances; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000648:ultrastructure; D012486:Salmonella typhimurium / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D026901:Membrane Transport Proteins; C079790:PrgH protein, Salmonella typhimurium; C090991:invG protein, Salmonella typhimurium