Neutrophil-activating protein (HP-NAP) versus ferritin (Pfr): comparison of synthesis in Helicobacter pylori

Abstract

We recently reported that the neutrophil-activating protein (HP-NAP) of Helicobacter pylori is capable of binding iron in vitro. To more fully understand the relationship between iron and HP-NAP the synthesis of HP-NAP was compared to that of Pfr, another iron-binding protein of H. pylori. Synthesis of HP-NAP and Pfr in growing cultures of H. pylori was analysed under iron depletion and iron, copper, nickel and zinc overload. The synthesis of HP-NAP and Pfr in H. pylori was also analysed under conditions of varying pH and oxidative stress. In addition, recombinant HP-NAP and Pfr were produced in Escherichia coli to assess the contribution of the two proteins to increased survival of E. coli under heavy metal overload. Our data reveal that both HP-NAP and Pfr accumulate in the stationary phase of growth. HP-NAP synthesis is not regulated by iron depletion or overload or by the presence of copper, nickel or zinc in liquid medium and it does not confer resistance to these metals when produced in E. coli. Except for an increase in the synthesis of Pfr at pH 5.7 neither the pH or oxidative stress conditions investigated had an affect on the synthesis of either protein. An increase in Pfr synthesis was observed under iron overload and a decrease was observed under conditions of copper, nickel and zinc overload confirming previous reports. Recombinant Pfr, as well as conferring resistance to iron and copper as previously reported, also conferred resistance to zinc overload when produced in E. coli.