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Metal-binding properties of an Hpn-like histidine-rich protein

Zeng, Yi-Bo, Yang, Nan and Sun, Hongzhe 2011. Metal-binding properties of an Hpn-like histidine-rich protein. Chemistry - A European Journal 17 (21) , pp. 5852-5860. 10.1002/chem.201100279

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The Hpn‐like protein (Hpnl), a histidine‐ and glutamine‐rich protein, is critical for Helicobacter pylori colonization in human gastric muscosa. In this study, the thermodynamic properties of NiII, CuII, CoII, and ZnII toward Hpnl were studied by isothermal titration calorimetry (ITC). We found that Hpnl exhibits two independent binding sites for NiII as opposed to one site for CuII, CoII, and ZnII. Protease digestion and chemical denaturation analysis further revealed that NiII confers a higher stability upon Hpnl than other divalent metal ions. The potential NiII binding sites are localized in the His‐rich domain of Hpnl as confirmed by mutagenesis in combination with modification of histidine residues of the protein. We also demonstrated that the single mutants (H29A and H31A) and tetrameric mutant (H29‐32A) cut nearly half of the binding capacity of Hpnl towards nickel ions, whereas other histidine residues (His30, 32, 38, 39, 40, and 41) are nonessential for nickel coordination. Escherichia coli cells that harbored H29A, H31A, and H29‐32A mutant genes exhibited less tolerance toward high concentrations of extracellular nickel ions than those with the wild‐type gene. Our combined data indicated that the conserved histidine residues, His29 and His31 in the His‐rich domain of Hpnl, are critical for nickel binding, and such a binding is important for Hpnl protein to fulfill its biological functions.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: Wiley
ISSN: 0947-6539
Last Modified: 03 Feb 2021 15:16

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