title: The coordination of NiII and Cu(II) ions to the polyhistidyl motif of Hpn protein: is it as strong as we think?
abstract: Hpn, one of Helicobacter pylori's nickel-accessory proteins, is an amazingly peculiar protein: Almost half of its sequence consists of polyhistidyl (poly-His) residues. Herein, we try to understand the origin of this naturally occurring sequence, thereby shedding some light on the bioinorganic chemistry of Hpn's numerous poly-His repeats. By using potentiometric, mass spectrometric, and various spectroscopic techniques, we studied the Ni(II) - and Cu(II) complexes of the wild-type Ac-THHHHYHGG-NH(2) fragment of Hpn and of its six analogues, in which consecutive residues (His or Tyr) were replaced by Ala (Ala-substitution or Ala-scan approaches), thereby resulting in Ac-TAHHHYHGG-NH(2), Ac-THAHHYHGG-NH(2), Ac-THHAHYHGG-NH(2), Ac-THHHAYHGG-NH(2), Ac-THHHHAHGG-NH(2), and Ac-THHHHYAGG-NH(2) peptides. We found that the His4 residue is critical for both Ni(II) - and Cu(II) -ion binding and the effectiveness of binding varies even if the substituted amino acid does not take part in the direct binding interactions.
authors: Faculty of Chemistry, University of Wroclaw, Wroclaw, Poland.
authors: Danuta
authors: D
authors: Witkowska
authors: Rossella
authors: R
authors: Politano
authors: Magdalena
authors: M
authors: Rowinska-Zyrek
authors: Remo
authors: R
authors: Guerrini
authors: Maurizio
authors: M
authors: Remelli
authors: Henryk
authors: H
authors: Kozlowski
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D056831:Coordination Complexes / Q000138:chemical synthesis*; D003300:Copper / Q000737:chemistry*; D016480:Helicobacter pylori / Q000737:chemistry; D006639:Histidine / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D011199:Potentiometry; D011485:Protein Binding; D014443:Tyrosine / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D056831:Coordination Complexes; C033223:polyhistidine; D014443:Tyrosine; D006639:Histidine; D003300:Copper; D009532:Nickel; D000409:Alanine