The Helicobacter pylori HypA·UreE2 Complex Contains a Novel High-Affinity Ni(II)-Binding Site

Biochemistry. 2018 May 22;57(20):2932-2942. doi: 10.1021/acs.biochem.8b00127. Epub 2018 May 10.

Abstract

Helicobacter pylori is a human pathogen that colonizes the stomach, is the major cause of ulcers, and has been associated with stomach cancers. To survive in the acidic environment of the stomach, H. pylori uses urease, a nickel-dependent enzyme, to produce ammonia for maintenance of cellular pH. The bacteria produce apo-urease in large quantities and activate it by incorporating nickel under acid shock conditions. Urease nickel incorporation requires the urease-specific metallochaperone UreE and the (UreFGH)2 maturation complex. In addition, the H. pylori nickel urease maturation pathway recruits accessory proteins from the [NiFe] hydrogenase maturation pathway, namely, HypA and HypB. HypA and UreE dimers (UreE2) are known to form a protein complex, the role of which in urease maturation is largely unknown. Herein, we examine the nickel-binding properties and protein-protein interactions of HypA and UreE2 using isothermal titration calorimetry and fluorometric methods under neutral and acidic pH conditions to gain insight into the roles played by HypA in urease maturation. The results reveal that HypA and UreE2 form a stable complex with micromolar affinity that protects UreE from hydrolytic degradation. The HypA·UreE2 complex contains a unique high-affinity (nanomolar) Ni2+-binding site that is maintained under conditions designed to mimic acid shock (pH 6.3). The data are interpreted in terms of a proposed mechanism wherein HypA and UreE2 act as co-metallochaperones that target the delivery of Ni2+ to apo-urease with high fidelity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Binding Sites
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Helicobacter pylori / chemistry*
  • Helicobacter pylori / genetics
  • Helicobacter pylori / pathogenicity
  • Humans
  • Metallochaperones / chemistry
  • Metallochaperones / genetics
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / genetics
  • Nickel / chemistry
  • Protein Binding
  • Protein Domains

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • HypA protein, Helicobacter pylori
  • Metallochaperones
  • Multiprotein Complexes
  • UreE protein, Bacteria
  • Nickel