title: Structure of HrcQB-C, a conserved component of the bacterial type III secretion systems.
abstract: Type III secretion systems enable plant and animal bacterial pathogens to deliver virulence proteins into the cytosol of eukaryotic host cells, causing a broad spectrum of diseases including bacteremia, septicemia, typhoid fever, and bubonic plague in mammals, and localized lesions, systemic wilting, and blights in plants. In addition, type III secretion systems are also required for biogenesis of the bacterial flagellum. The HrcQ(B) protein, a component of the secretion apparatus of Pseudomonas syringae with homologues in all type III systems, has a variable N-terminal and a conserved C-terminal domain (HrcQ(B)-C). Here, we report the crystal structure of HrcQ(B)-C and show that this domain retains the ability of the full-length protein to interact with other type III components. A 3D analysis of sequence conservation patterns reveals two clusters of residues potentially involved in protein-protein interactions. Based on the analogies between HrcQ(B) and its flagellum homologues, we propose that HrcQ(B)-C participates in the formation of a C-ring-like assembly.
authors.affiliation: Department of Biology, University of Crete, PO Box 2208, GR-71409 Heraklion, Crete, Greece.
authors.forename: Vasiliki E
authors.initials: VE
authors.lastname: Fadouloglou
authors.forename: Anastasia P
authors.initials: AP
authors.lastname: Tampakaki
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Glykos
authors.forename: Marina N
authors.initials: MN
authors.lastname: Bastaki
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Hadden
authors.forename: Simon E
authors.initials: SE
authors.lastname: Phillips
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Panopoulos
authors.forename: Michael
authors.initials: M
authors.lastname: Kokkinidis
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D044224:Pseudomonas syringae / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; C441634:HrcQb protein, Pseudomonas syringae; D011994:Recombinant Proteins