title: YscB of Yersinia pestis functions as a specific chaperone for YopN.
abstract: Following contact with a eucaryotic cell, Yersinia species pathogenic for humans (Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica) export and translocate a distinct set of virulence proteins (YopE, YopH, YopJ, YopM, and YpkA) from the bacterium into the eucaryotic cell. During in vitro growth at 37 degrees C in the presence of calcium, Yop secretion is blocked; however, in the absence of calcium, Yop secretion is triggered. Yop secretion occurs via a plasmid-encoded type III, or "contact-dependent," secretion system. The secreted YopN (also known as LcrE), TyeA, and LcrG proteins are necessary to prevent Yop secretion in the presence of calcium and prior to contact with a eucaryotic cell. In this paper we characterize the role of the yscB gene product in the regulation of Yop secretion in Y. pestis. A yscB deletion mutant secreted YopM and V antigen both in the presence and in the absence of calcium; however, the export of YopN was specifically reduced in this strain. Complementation with a functional copy of yscB in trans completely restored the wild-type secretion phenotype for YopM, YopN, and V antigen. The YscB amino acid sequence showed significant similarities to those of SycE and SycH, the specific Yop chaperones for YopE and YopH, respectively. Protein cross-linking and immunoprecipitation studies demonstrated a specific interaction between YscB and YopN. In-frame deletions in yopN eliminating the coding region for amino acids 51 to 85 or 6 to 100 prevented the interaction of YopN with YscB. Taken together, these results indicate that YscB functions as a specific chaperone for YopN in Y. pestis.
authors.affiliation: Department of Microbiology and Immunology, University of Miami School of Medicine, Miami, Florida 33176, USA.
authors.forename: M W
authors.initials: MW
authors.lastname: Jackson
authors.forename: J B
authors.initials: JB
authors.lastname: Day
authors.forename: G V
authors.initials: GV
authors.lastname: Plano
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology*; D001665:Binding Sites; D008565:Membrane Proteins; D018832:Molecular Chaperones / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D015534:Trans-Activators / Q000502:physiology; D015010:Yersinia pestis / Q000502:physiology*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; C081269:SycE protein, Yersinia; D015534:Trans-Activators; C063239:yopE protein, Yersinia; C070015:YopN protein, Yersinia