Characterization of theC-Terminal Domain ofHelicobacter pyloriVacuolating Toxin and Its Relationship with Extracellular Toxin Production

Abstract

Helicobacter pylorivacuolating cytotoxin (VacA) induces gastric epithelial necrosis. ItsC-terminal domain is hypothesized to be responsible for extracellular translocation of the mature cytotoxin. In this study, genetic-structural properties of VacAC-terminal domain and the level of cytotoxin secretion were investigated.Sau3AI-HaeIII restriction fragment length polymorphism (RFLP) analysis of the 1.1-kb PCR-amplifiedvacAfragment revealed 14 distinct combined patterns among 87 clinical isolates. Of the 4 popular groups (A-a, A-b, A-f, and B-a), A-a strains produced a higher level of the VacA protein than A-b strains and than A-f strains (P < 0.05). Sequence analysis and secondary structure prediction supported a β-barrel structure that might act as a selective export channel like Igaβ-core of IgA proteases. Sequence differences in the predicted β-barrel were present among strains of different RFLPs.