The binding of Ni(II) ions to hexahistidine as a model system of the interaction between nickel and His-tagged proteins

LAURA E. VALENTI; CARLOS P. DE PAULI; CARLA EUGENIA GIACOMELLI

JOURNAL OF INORGANIC BIOCHEMISTRY

Elsevier Science B.V.

Año: 2006 vol. 100 p. 192 - 192

0162-0134

font size="1" face="AdvEPSTIM"> The aim of this work is to study the binding of nickel ions to hexahistidine (His6) combining potentiometric titrations and spectroscopic (UV?Vis and circular dichroism) determinations in order to establish the species distribution as a function of the pH, their stoichiometry, stability and geometry. For comparative purposes, the same procedure was applied to the Ni?histidine (His) system. His behaves as a tridentate ligand, coordinating the carboxyl group, the imidazole and the amino nitrogen atoms to Ni(II) ions in an octahedral coordination and a bis(histidine) complex is formed at pH higher than 5. For the Ni?His6 system, the complex formation starts at  pH 4 and five different species (Ni(His6)H, Ni(His