ABSTRACT
Maintaining
metal homeostasis is crucial for the adaptation of Helicobacter
pylori to the gastric environment. Iron, copper, and nickel
homeostasis has recently been demonstrated to be required for the
establishment of H. pylori infection 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.
pylori metal 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.
pylori reference 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 cznC and
cznA mutants but not the cznB mutant 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
cznC mutants did not colonize the stomach in a Mongolian
gerbil-based animal model. This demonstrates that the metal export
functions of H. pylori cznABC are essential for gastric
colonization and underlines the extraordinary importance of metal ion
homeostasis for the survival of H. pylori in the gastric
environment.
Insight into the essential role of the Helicobacter pylori HP1043 orphan response regulator: genome-wide identification and characterization of the DNA-binding sites