The Novel Helicobacter pyloriCznABC Metal Efflux Pump Is Required for Cadmium, Zinc, and Nickel Resistance,Urease Modulation, and Gastric Colonization

ABSTRACTMaintaining metal homeostasis is crucial for the adaptation of Helicobacter pylorito the gastric environment. Iron, copper, and nickel homeostasis has recently been demonstrated to be required for the establishment of H. pyloriinfection in animal models. Here we demonstrate that the HP0969-0971 gene cluster encoding the Czc-type metal export pump homologs HP0969, HP0970, and the H. pylori-specific protein HP0971 forms part of a novel H. pylorimetal resistance determinant, which is required for gastric colonization and for the modulation of urease activity. Insertional mutagenesis of the HP0971, HP0970, or HP0969 genes in H. pylorireference strain 26695 resulted in increased sensitivity to cadmium, zinc, and nickel (czn), suggesting that the encoded proteins constitute a metal-specific export pump. Accordingly, the genes were designated cznC(HP0971), cznB(HP0970), and cznA(HP0969). The CznC and CznA proteins play a predominant role in nickel homeostasis, since only the cznCand cznAmutants but not the cznBmutant displayed an 8- to 10-fold increase in urease activity. Nickel-specific affinity chromatography demonstrated that recombinant versions of CznC and CznB can bind to nickel and that the purified CznB protein interacted with cadmium and zinc, since both metals competitively inhibited nickel binding. Finally, single cznA, cznB, and cznCmutants did not colonize the stomach in a Mongolian gerbil-based animal model. This demonstrates that the metal export functions of H. pylori cznABCare essential for gastric colonization and underlines the extraordinary importance of metal ion homeostasis for the survival of H. pyloriin the gastric environment.