title: Structural characterization of a novel Chlamydia pneumoniae type III secretion-associated protein, Cpn0803.
abstract: Type III secretion (T3S) is an essential virulence factor used by gram-negative pathogenic bacteria to deliver effector proteins into the host cell to establish and maintain an intracellular infection. Chlamydia is known to use T3S to facilitate invasion of host cells but many proteins in the system remain uncharacterized. The C. trachomatis protein CT584 has previously been implicated in T3S. Thus, we analyzed the CT584 ortholog in C. pneumoniae (Cpn0803) and found that it associates with known T3S proteins including the needle-filament protein (CdsF), the ATPase (CdsN), and the C-ring protein (CdsQ). Using membrane lipid strips, Cpn0803 interacted with phosphatidic acid and phosphatidylinositol, suggesting that Cpn0803 may associate with host cells. Crystallographic analysis revealed a unique structure of Cpn0803 with a hydrophobic pocket buried within the dimerization interface that may be important for binding small molecules. Also, the binding domains on Cpn0803 for CdsN, CdsQ, and CdsF were identified using Pepscan epitope mapping. Collectively, these data suggest that Cpn0803 plays a role in T3S.
authors.affiliation: M. G. DeGroote Institute for Infectious Disease Research, Faculty of Health Sciences and the Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors.forename: Chris B
authors.initials: CB
authors.lastname: Stone
authors.forename: Seiji
authors.initials: S
authors.lastname: Sugiman-Marangos
authors.forename: David C
authors.initials: DC
authors.lastname: Bulir
authors.forename: Rob C
authors.initials: RC
authors.lastname: Clayden
authors.forename: Tiffany L
authors.initials: TL
authors.lastname: Leighton
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Slootstra
authors.forename: Murray S
authors.initials: MS
authors.lastname: Junop
authors.forename: James B
authors.initials: JB
authors.lastname: Mahony
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D016993:Chlamydophila pneumoniae / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D010712:Phosphatidic Acids / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D010712:Phosphatidic Acids; D010716:Phosphatidylinositols; D011994:Recombinant Proteins