Structural characterization of a novel Chlamydia pneumoniae type III secretion-associated protein, Cpn0803

• Published in: PloS one 2012-01, Vol.7 (1), p.e30220-e30220
• Main Authors: Stone, Chris B, Sugiman-Marangos, Seiji, Bulir, David C, Clayden, Rob C, Leighton, Tiffany L, Slootstra, Jerry W, Junop, Murray S, Mahony, James B
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatase; Amino acids; Analysis; Antigenic determinants; Antigens; ATPases; Automation; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Binding; Biochemistry; Biology; Blotting, Western; Buried structures; Chlamydia; Chlamydia pneumoniae; Chlamydophila pneumoniae; Chlamydophila pneumoniae - genetics; Chlamydophila pneumoniae - metabolism; Cholesterol; Crystallography; Crystallography, X-Ray; Dimerization; E coli; Epitope mapping; Health aspects; Health sciences; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Infectious diseases; Medicine; Membrane proteins; Metabolism; Models, Molecular; Pathology; Phosphatidic acid; Phosphatidic Acids - metabolism; Phosphatidylinositol; Phosphatidylinositols - metabolism; Pneumonia; Protein Binding; Protein Interaction Mapping; Protein Multimerization; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins; Pseudomonas aeruginosa; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Secretion; Sexually transmitted diseases; STD; Structural analysis; Virulence; Virulence (Microbiology); Virulence factors; Yersinia pestis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0030220

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.