Nickel trafficking system responsible for urease maturation in Helicobacter pylori

Figure 1 Structure of Helicobacter pylori urease. A: The urease enzyme subunit UreAB (UreA, blue; UreB, cyan; PDB code: 1E9Z); B: The active sites of H. pylori urease with the side chains of the enzyme involved in the chelation of the catalytic di-nickel center shown (Ni, green; O, red; N, blue; C, pink). H. pylori: Helicobacter pylori.

Figure 2 Amino acid sequence of Hpn (A) and the apparent rate of nickel release vs concentrations of ethylenediaminetetraacetic acid at pH 6. 8 and 7.4 and the best nonlinear fit of the data (B). EDTA: Ethylenediaminetetraacetic acid.

Figure 3 Complex network controlling urease synthesis and activity in Helicobacter pylori. The different levels of control comprise (1) expression of the UreAB structural subunits fine-tuned by acidity and the nickel-dependent transcriptional regulator NikR; (2) nickel uptake into cells via NixA importer; (3) nickel storage in histidine-rich proteins such as Hpn, Hpnl and HspA; (4) nickel incorporation into urease as mediated by accessory proteins UreEFGH and HypAB; and (5) urea substrate entry via UreI. H. pylori: Helicobacter pylori.