Mutational analysis of the Helicobacter pylori vacuolating toxin amino terminus: Identification of amino acids essential for cellular vacuolation

The functional importance of the amino terminus of the Helicobacter pylori vacuolating cytotoxin (VacA) was investigated by analyzing the relative lev els of vacuolation of HeLa cells transfected with plasmids encoding wild-ty pe and mutant forms of the toxin. Notably, VacA's intracellular activity wa s found to be sensitive to small truncations and internal deletions at the toxin's amino terminus. Moreover, alanine scanning mutagenesis revealed the first VacA point mutations (at proline 9 or glycine 14) that completely ab olish the toxin's intracellular activity.