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The Coordination of Ni II and Cu II Ions to the Polyhistidyl Motif of Hpn Protein: Is It as Strong as We Think?
Author(s) -
Witkowska Danuta,
Politano Rossella,
RowinskaZyrek Magdalena,
Guerrini Remo,
Remelli Maurizio,
Kozlowski Henryk
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201200780
Subject(s) - bioinorganic chemistry , chemistry , crystallography , potentiometric titration , stereochemistry , ion , peptide sequence , nickel , amino acid , biochemistry , organic chemistry , gene
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.