YscO of Yersinia pestis is a mobile core component of the Yop secretion system.
The Yersinia pestis low-Ca2+ response stimulon is responsible for the temperature- and Ca2+-regulated expression and secretion of plasmid pCD1-encoded antihost proteins (V antigen and Yops). We have previously shown that lcrD, yscC, yscD, yscG, and yscR encode proteins that are essential for high-level expression and secretion of V antigen and Yops at 37 degreesC in the absence of Ca2+. In this study, we characterized yscO of the Yop secretion (ysc) operon that contains yscN through yscU by determining the localization of its gene product and the phenotype of an in-frame deletion. The yscO mutant grew and expressed the same levels of Yops as the parent at 37 degreesC in the presence of Ca2+. In the absence of Ca2+, the mutant grew independently of Ca2+, expressed only basal levels of V antigen and Yops, and failed to secrete these. These defects could be partially complemented by providing yscO in trans in the yscO mutant. Overexpression of YopM and V antigen in the mutant failed to restore the export of either protein, showing that the mutation had a direct effect on secretion. These results indicated that the yscO gene product is required for high-level expression and secretion of V antigen and Yops. YscO was found by immunoblot analysis in the soluble and membrane fractions of bacteria growing at 37 degreesC irrespective of the presence of Ca2+ and in the culture medium in the absence of Ca2+. YscO is the only mobile protein identified so far in the Yersinia species that is required for secretion of V antigen and Yops.
Department of Microbiology and Immunology, Albert B. Chandler Medical Center, University of Kentucky, Lexington, Kentucky 40536-0084, USA.
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Payne
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Straley
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D003001:Cloning, Molecular; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009876:Operon; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D017384:Sequence Deletion; D013696:Temperature; D015010:Yersinia pestis / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C113723:YscO protein, Yersinia pestis; D002118:Calcium