Interactions among the seven Helicobacter pylori proteins encoded by the urease gene cluster.

Survival of Helicobacter pylori in acid depends on intrabacterial urease. This urease is a Ni(2+)-containing oligomeric heterodimer. Regulation of its activity and assembly is important for gastric habitation by this neutralophile. The gene complex encodes catalytic subunits (ureA/B), an acid-gated urea channel (ureI), and accessory assembly proteins (ureE-H). With the use of yeast two-hybrid analysis for determining protein-protein interactions, UreF as bait identified four interacting sequences encoding UreH, whereas UreG as bait detected five UreE sequences. These results were confirmed by coimmunoprecipitation and beta-galactosidase assays. Native PAGE immunoblotting of H. pylori inner membranes showed interaction of UreA/B with UreI, whereas UreI deletion mutants lacked this protein interaction. Deletion of ureE-H did not affect this interaction with UreI. Hence, the accessory proteins UreE/G and UreF/H form dimeric complexes and UreA/B form a membrane complex with UreI, perhaps enabling assembly of the urease apoenzyme at the membrane surface and immediate urea access to intrabacterial urease to allow rapid periplasmic neutralization.