CELL-SURFACE-BOUND YERSINIA TRANSLOCATE THE PROTEIN-TYROSINE-PHOSPHATASE YOPH BY A POLARIZED MECHANISM INTO THE TARGET-CELL

YopH is translocated by cell-surface-bound bacteria through the plasma membrane to the cytosol of the HeLa cell. The transfer mechanism is c ontact dependent and polarizes the translocation to only occur at the contact zone between the bacterium and the target cell. More than 99% of the PTPase activity is associated with the HeLa cells. In contrast to the wild-type strain, the yopBD mutant cannot deliver YopH to the c ytosol. Instead YopH is deposited in localized areas in the proximity of cell-associated bacteria. A yopN mutant secretes 40% of the total a mount of YopH to the culture medium, suggesting a critical role of Yop N in regulation of the polarized translocation. Evidence for a region in YopH important for its translocation through the plasma membrane of the target cell but not for secretion from the pathogen is provided.