CONTRIBUTION OF YOPB TO VIRULENCE OF YERSINIA-ENTEROCOLITICA

The 70-kb virulence plasmid, pYV, of Yersinia enterocolitica encodes a number of secreted proteins (Yops) which are essential for virulence. YopD, the 33-kDa product of the lcrGVHyopBD operon, appears to be inv olved in delivering YopE and YopH (the Yersinia protein tyrosine phosp hatase) into target cells, These proteins then act in concert to cause cytotoxicity in host cells, Previously, we reported that bacteria car rying transposon insertions in yopD are not cytotoxic for macrophages, show impaired tyrosine phosphatase activity in host cells, and are av irulent for mice (E. L. Hartland, S. P. Green, W. A. Phillips, and R. M. Robins-Browne, Infect. Immun. 62:4445-4453, 1994), trans complement ation of yopD mutants of Y. enterocolitica with the yopD gene restores all these properties. In this study, we show that polar mutations in proximal genes of the lcrGVHyopBD operon also abrogated bacterial viru lence and the capacity to induce cytotoxicity in mouse bone marrow-der ived macrophages and HEp-2 epithelial cells. Moreover, trans complemen tation of a yopBD mutant with the yopD gene alone was not sufficient t o restore the ability of the bacteria to cause cytotoxicity. Further w ork showed that YopB was required for cytotoxicity, dephosphorylation of host proteins, and virulence for mice. These findings indicate that YopB and YopD mag serve a related function in Y. enterocolitica and t hat they may act together to deliver intracellularly acting Yops to th eir respective targets in host cells.