A structural overview of the Helicobacter cytotoxin

VacA, the major exotoxin produced by Helicobacter pylori, is composed of id entical 87-kDa monomers that assemble into newer-shaped oligomers. The mono mers can be proteolytically cleaved into two moieties of 37 and 58 kDa, or P37 and P58. The most studied property of VacA is the alteration of intrace llular vesicular trafficking in eukaryotic cells leading to the formation o f large vacuoles containing markers of late endosomes and lysosomes. Howeve r, VacA also causes a reduction in trans-epithelial electrical resistance i n polarized monolayers and forms ion channels in lipid bilayers. The abilit y to induce vacuoles is localized mostly but not entirely in P37, while P58 is involved in cell targeting. Here, we review the structural aspects of V acA biology.