Deletion of the Major Proteolytic Site of the Helicobacter pylori Cytotoxin Does Not Influence Toxin Activity but Favors Assembly of the Toxin into Hexameric Structures

The Helicobacter pylori cytotoxin is proteolytically cleaved at a flexible hydrophilic loop into two subunits. Deletion of the loop sequences had no effect on biological activity of the toxin in the HeLa cell vacuolation assay but favored the organization of the protein into hexameric rather than heptameric structures.