Copper(II), nickel(II) and zinc(II) complexes of N-acetyl-His-Pro-His-His-NH2: Equilibria, solution structure and enzyme mimicking

Ida Noemi Jakab, Attila Jancso, Tamas Gajda, Bela Gyurcsik, Antal Rockenbauer

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The copper(II), nickel(II) and zinc(II) binding ability of the multi-histidine peptide N-acetyl-His-Pro-His-His-NH2 has been studied by combined pH-potentiometry and visible, CD and EPR spectroscopies. The internal proline residue, preventing the metal ion induced successive amide deprotonations, resulted in the shift of this process toward higher pH values as compared to other peptides. The metal ions in the parent [ML]2+ complexes are exclusively bound by the three imidazole side chains. In [CuH−1L]+, formed between pH 6–8, the side chains of the two adjacent histidines and the peptide nitrogen between them are involved in metal ion binding. The next deprotonation results in the proton loss of the coordinated water molecule (CuH−1L(OH)). The latter two species exert polyfunctional catalytic activity, since they possess superoxide dismutase-, catecholase- (the oxidation of 3,5-di-tert-butylcatechol) and phosphatase-like (transesterification of the activated phosphoester 2-hydroxypropyl-4-nitrophenyl phosphate) properties. On further increase of the pH rearrangement of the coordination sphere takes place leading to the [CuH−3L]− species, the deprotonated amide nitrogen displaces a coordinated imidazole nitrogen from the equatorial position of the metal ion. The shapes of the visible and CD spectra reflect a distorted arrangement of the donor atoms around the metal ion. In presence of zinc(II) the species [ZnL]2+ forms only above pH 6, which is shortly followed by precipitation. On the other hand, the [NiL]2+ complex is stable over a wide pH range, its deprotonation takes place only above pH 8. At pH 10 an octahedral NiH−2L species is present at first, which transforms slowly to a yellow square planar complex.
Keyword: Catecholase activity,SOD activity,Peptide complexes,Equilibrium studies,Histidine-rich peptides
Original languageEnglish
JournalJournal of Inorganic Biochemistry
Volume102
Issue number7
Pages (from-to)1438-1448
ISSN0162-0134
DOIs
Publication statusPublished - 2008
Externally publishedYes

Cite this