The Yersinia pestis YscY protein directly binds YscX, a secreted componentof the type III secretion machinery

Human pathogenic yersiniae organisms export and translocate the Yop virulen ce proteins and V antigen upon contact with a eukaryotic cell. Yersinia pes tis mutants defective for production of YscX or YscY were unable to export the Yops and V antigen. YscX and YscY were both present in the Y. pestis ce ll pellet fraction; however, YscX was also found in the culture supernatant . YscY showed structural and amino acid sequence similarities to the Syc fa mily of proteins, YscY specifically recognized and bound to a region of Ysc X that included a predicted coiled-coil region. These data suggest that Ysc Y may function as a chaperone for YscX in Y, pestis.