title: Chlamydia trachomatis Slc1 is a type III secretion chaperone that enhances the translocation of its invasion effector substrate TARP.
abstract: Bacterial type III secretion system (T3SS) chaperones pilot substrates to the export apparatus in a secretion-competent state, and are consequently central to the translocation of effectors into target cells. Chlamydia trachomatis is a genetically intractable obligate intracellular pathogen that utilizes T3SS effectors to trigger its entry into mammalian cells. The only well-characterized T3SS effector is TARP (translocated actin recruitment protein), but its chaperone is unknown. Here we exploited a known structural signature to screen for putative type III secretion chaperones encoded within the C. trachomatis genome. Using bacterial two-hybrid, co-precipitation, cross-linking and size exclusion chromatography we show that Slc1 (SycE-like chaperone 1; CT043) specifically interacts with a 200-amino-acid residue N-terminal region of TARP (TARP¹⁻²⁰⁰). Slc1 formed homodimers in vitro, as shown in cross-linking and gel filtration experiments. Biochemical analysis of an isolated Slc1-TARP¹⁻²⁰⁰ complex was consistent with a characteristic 2:1 chaperone-effector stoichiometry. Furthermore, Slc1 was co-immunoprecipitated with TARP from C. trachomatis elementary bodies. Also, coexpression of Slc1 specifically enhanced host cell translocation of TARP by a heterologous Yersinia enterocolitica T3SS. Taken together, we propose Slc1 as a chaperone of the C. trachomatis T3SS effector TARP.
authors: Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College, London SW72AZ, UK.
authors: Amanda J
authors: AJ
authors: Brinkworth
authors: Denise S
authors: DS
authors: Malcolm
authors: António T
authors: AT
authors: Pedrosa
authors: Katarzyna
authors: K
authors: Roguska
authors: Sevanna
authors: S
authors: Shahbazian
authors: James E
authors: JE
authors: Graham
authors: Richard D
authors: RD
authors: Hayward
authors: Rey A
authors: RA
authors: Carabeo
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002690:Chlamydia Infections / Q000382:microbiology*; D002692:Chlamydia trachomatis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D021381:Protein Transport; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones