Copper(II) Coordination Abilities of the Tau Protein’s NTerminus Peptide Fragments: A Combined Potentiometric, Spectroscopic and Mass Spectrometric Study

Lukács, Márton and Szunyog, Györgyi and Grenács, Ágnes and Lihi, Norbert and Kállay, Csilla and Campagna, Tiziana and Di Natale, Giuseppe and Lanza, Valeria and Pappalardo, Giuseppe and Tabbi, Giovanni and Sóvágó, Imre and Várnagy, Katalin (2019) Copper(II) Coordination Abilities of the Tau Protein’s NTerminus Peptide Fragments: A Combined Potentiometric, Spectroscopic and Mass Spectrometric Study. ChemPlusChem. ISSN 2192-6506

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Abstract

Copper(II) and nickel(II) complexes of the N-terminal peptide fragments of tau protein have been studied by potentiometric and various spectroscopic techniques (UV-vis, CD, ESR and ESI-MS). The octapeptide Tau(9-16) (Ac-EVMEDHAG-NH2) contains H14 residue of the native protein, while Tau(26-33) (Ac-QGGYTMHQ-NH2) and its mutants Ac-KGGYTMHK-NH2 and Ac-KGGATMHK-NH2 include H32. To compare the binding ability of H14 and H32 in a single molecule the decapeptide Ac-EDHAGTMHQD-NH2 has also been synthesized and studied. Histidyl residues are the primary metal binding sites for both metal ions, but in the case of Tau(9-16) the side chain carboxylate functions can enhance the stability of the M-Nim coordinated complexes. Deprotonation and metal ion coordination of amide groups occur around the physiological pH range for copper(II) and in slightly alkaline samples for nickel(II). The formation of the amide coordinated species with (Nim,N–,N–,N–) binding mode changes the metal ion preference and the complexes formed with the peptides containing H32 residue predominate over those of H14 in alkaline samples.

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