title: The Yersinia enterocolitica type three secretion chaperone SycO is integrated into the Yop regulatory network and binds to the Yop secretion protein YscM1.
abstract: BACKGROUND
  Pathogenic yersiniae (Y. pestis, Y. pseudotuberculosis, Y. enterocolitica) share a virulence plasmid encoding a type three secretion system (T3SS). This T3SS comprises more than 40 constituents. Among these are the transport substrates called Yops (Yersinia outer proteins), the specific Yop chaperones (Sycs), and the Ysc (Yop secretion) proteins which form the transport machinery. The effectors YopO and YopP are encoded on an operon together with SycO, the chaperone of YopO. The characterization of SycO is the focus of this study.
  
  
  RESULTS
  We have established the large-scale production of recombinant SycO in its outright form. We confirm that Y. enterocolitica SycO forms homodimers which is typical for Syc chaperones. SycO overproduction in Y. enterocolitica decreases secretion of Yops into the culture supernatant suggesting a regulatory role of SycO in type III secretion. We demonstrate that in vitro SycO interacts with YscM1, a negative regulator of Yop expression in Y. enterocolitica. However, the SycO overproduction phenotype was not mediated by YscM1, YscM2, YopO or YopP as revealed by analysis of isogenic deletion mutants.
  
  
  CONCLUSIONS
  We present evidence that SycO is integrated into the regulatory network of the Yersinia T3SS. Our picture of the Yersinia T3SS interactome is supplemented by identification of the SycO/YscM1 interaction. Further, our results suggest that at least one additional interaction partner of SycO has to be identified.
authors.affiliation: Max von Pettenkofer-Institut, Lehrstuhl für Bakteriologie, Ludwig-Maximilians-Universität München, München, Germany. dittmann@mvp.uni-muenchen.de <dittmann@mvp.uni-muenchen.de>
authors.forename: Svea
authors.initials: S
authors.lastname: Dittmann
authors.forename: Annika
authors.initials: A
authors.lastname: Schmid
authors.forename: Susanna
authors.initials: S
authors.lastname: Richter
authors.forename: Konrad
authors.initials: K
authors.lastname: Trülzsch
authors.forename: Jürgen
authors.initials: J
authors.lastname: Heesemann
authors.forename: Gottfried
authors.initials: G
authors.lastname: Wilharm
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D019281:Dimerization; D015964:Gene Expression Regulation, Bacterial; D018832:Molecular Chaperones / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*; D015008:Yersinia enterocolitica / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones; D014157:Transcription Factors; C110346:YscM1 protein, Yersinia enterocolitica