Identification of the Helicobacter pylori VacA toxin domain active in the cell cytosol

Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles whic h originate from massive swelling of membranous compartments at late stages of the endocytic pathway. When expressed in the cytosol, VacA induces vacu olization as it does when added from outside. This and other evidence indic ate that VacA is a toxin capable of entering the cell cytosol, where it dis plays its activity. In this study, me have used cytosolic expression to ide ntify the portion of the toxin molecule responsible for the vacuolating act ivity. VacA mutants with deletions at the C and N termini were generated, a nd their activity was analyzed upon expression in HeLa cells. We found that the vacuolating activity of VacA resides in the amino-terminal region, the whole of which is required for its intracellular activity.