Chlamydia trachomatis Slc1 is a type III secretion chaperone that enhances the translocation of its invasion effector substrate TARP

Amanda J Brinkworth, Denise S Malcolm, António T Pedrosa, Katarzyna Roguska, Sevanna Shahbazian, James E Graham, Richard D Hayward, Rey A Carabeo

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29 Citations (Scopus)


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¿²°°). Slc1 formed homodimers in vitro, as shown in cross-linking and gel filtration experiments. Biochemical analysis of an isolated Slc1-TARP¹¿²°° 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.
Original languageEnglish
Pages (from-to)131-144
Number of pages14
JournalMolecular Microbiology
Issue number1
Early online date1 Sept 2011
Publication statusPublished - Oct 2011

Bibliographical note

© 2011 Blackwell Publishing Ltd.


  • bacterial proteins
  • sequence alignment
  • amino acid motifs
  • HeLa cells
  • humans
  • chlamydia infections
  • molecular sequence data
  • chlamydia trachomatis
  • molecular chaperones
  • amino acid sequence
  • protein binding
  • protein transport


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