Inhibition of Helicobacter pylori urease activity in vivo by the synthetic nickel binding protein Hpn.

Helicobacter pylori infection is the most common cause of gastroduodenal ulcerations worldwide. Adaptation of H. pylori to the acidic environment is mediated by urease splitting urea into carbon dioxide and ammonia. Whereas neutralization of acid by ammonia is essential for gastric H. pylori colonization, the catalytic activity of urease is mediated by nickel ions. Therefore, nickel uptake and metabolism play key roles in H. pylori infection and urease is considered first line target for drug development and vaccination. Since nickel binding within H. pylori cells is mediated by the Histidine-rich protein designated Hpn, we investigated whether nickel binding by a synthetic Hpn is capable of abrogating urease activity of live H. pylori in liquid cultures. Supplementation of growth media with synthetic Hpn completely inhibited urease acitivity in live cells, indicating that H. pylori nickel uptake is effectively blocked by Hpn. Thus, nickel chelation by Hpn is stronger than nickel uptake of H. pylori offering therapeutic use of Hpn. Although the nickel binding of Hpn was confirmed by binding assays in vitro, its use in anti-H. pylori directed strategy will further need to be adapted to the gastric environment given that protons interfere with nickel binding and Hpn is degraded by pepsin.