title: Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis.
abstract: Secretion of effector proteins into the eukaryotic host cell is required for Chlamydia trachomatis virulence. In the infection process, Scc1 and Scc4, two chaperones of the type III secretion (T3S) system, facilitate secretion of the important effector and plug protein, CopN, but little is known about the details of this event. Here we use biochemistry, mass spectrometry, nuclear magnetic resonance spectroscopy, and genetic analyses to characterize this trimolecular event. We find that Scc4 complexes with Scc1 and CopN in situ at the late developmental cycle of C. trachomatis. We show that Scc4 and Scc1 undergo dynamic interactions as part of the unique bacterial developmental cycle. Using alanine substitutions, we identify several amino acid residues in Scc4 that are critical for the Scc4-Scc1 interaction, which is required for forming the Scc4·Scc1·CopN ternary complex. These results, combined with our previous findings that Scc4 plays a role in transcription (Rao, X., Deighan, P., Hua, Z., Hu, X., Wang, J., Luo, M., Wang, J., Liang, Y., Zhong, G., Hochschild, A., and Shen, L. (2009) Genes Dev. 23, 1818-1829), reveal that the T3S process is linked to bacterial transcriptional events, all of which are mediated by Scc4 and its interacting proteins. A model describing how the T3S process may affect gene expression is proposed.
authors.affiliation: Department of Microbiology, Immunology, and Parasitology. Electronic address: lshen@lsuhsc.edu.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803.
authors.forename: Megan A
authors.initials: MA
authors.lastname: Macnaughtan
authors.affiliation: Department of Microbiology, Immunology, and Parasitology.
authors.forename: Kyla M
authors.initials: KM
authors.lastname: Frohlich
authors.affiliation: Department of Microbiology, Immunology, and Parasitology.
authors.forename: Yanguang
authors.initials: Y
authors.lastname: Cong
authors.affiliation: Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803.
authors.forename: Octavia Y
authors.initials: OY
authors.lastname: Goodwin
authors.affiliation: Department of Chemistry, University of Georgia, Athens, Georgia 30602.
authors.forename: Chau-Wen
authors.initials: CW
authors.lastname: Chou
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112.
authors.forename: Louis
authors.initials: L
authors.lastname: LeCour
authors.affiliation: Department of Microbiology, Immunology, and Parasitology.
authors.forename: Kristen
authors.initials: K
authors.lastname: Krup
authors.affiliation: Department of Microbiology, Immunology, and Parasitology.
authors.forename: Miao
authors.initials: M
authors.lastname: Luo
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112.
authors.forename: David K
authors.initials: DK
authors.lastname: Worthylake
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002692:Chlamydia trachomatis / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D012995:Solubility
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones
keywords: Chlamydia; CopN; Scc1; Scc4; chaperone; gene regulation; protein-protein interaction; type III secretion system (T3SS); virulence factor