Figure 3.

Complex network controlling urease synthesis and activity in Helicobacter pylori. The different levels of control comprise (1) expression of the UreAB structural subunits fine-tuned by acidity and the nickel-dependent transcriptional regulator NikR; (2) nickel uptake into cells via NixA importer; (3) nickel storage in histidine-rich proteins such as Hpn, Hpnl and HspA; (4) nickel incorporation into urease as mediated by accessory proteins UreEFGH and HypAB; and (5) urea substrate entry via UreI. H. pylori: Helicobacter pylori.