Probing the binding of Cu2+ ions to a fragment of the Aβ(1-42) polypeptide using fluorescence spectroscopy, isothermal titration calorimetry and molecular dynamics simulations

Joanna Makowska , Krzysztof Żamojć , Dariusz Wyrzykowski , Wioletta Żmudzińska , Dorota Uber , Małgorzata Wierzbicka , Wiesław Wiczk , Lech Chmurzyński

Abstract

Steady-state and time-resolved fluorescence quenching measurements supported by isothermal titration calorimetry (ITC) and molecular dynamics simulations (MD), with the NMR-derived restraints, were used to investigate the interactions of Cu2 + ions with a fragment of the Aβ(1–42) polypeptide, Aβ(5–16) with the following sequence: Ac-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-NH2, denoted as HZ1. The studies presented in this paper, when compared with our previous results (Makowska et al., Spectrochim. Acta A 153: 451–456), show that the affinity of the peptide to metal ions is conformation-dependent. All the measurements were carried out in 20 mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer solution, pH 6.0. The Stern-Volmer equations, along with spectroscopic observations, were used to determine the quenching and binding parameters. The obtained results unequivocally suggest that Cu2 + ions quench the fluorescence of HZ1 only through a static quenching mechanism, in contrast to the fragment from the N–terminal part of the FPB28 protein, with sequence Ac-Tyr-Lys-Thr-Ala-Asp-Gly-Lys-Thr-Tyr- NH2 (D9) and its derivative with a single point mutation: Ac-Tyr-Lys-Thr-Ala-Asn-Gly-Lys-Thr-Tyr- NH2 (D9_M), where dynamic quenching occurred. The thermodynamic parameters (ΔITCH, ΔITCS) for the interactions between Cu2 + ions and the HZ1 peptide were determined from the calorimetric data. The conditional thermodynamic parameters suggest that, under the experimental conditions, the formation of the Cu2 +-HZ1 complex is both an enthalpy and entropy driven process.
Author Joanna Makowska PFZK
Joanna Makowska,,
- Laboratory of Physicochemistry of Coordination Complexes
, Krzysztof Żamojć PFZK
Krzysztof Żamojć,,
- Laboratory of Physicochemistry of Coordination Complexes
, Dariusz Wyrzykowski PFZK
Dariusz Wyrzykowski,,
- Laboratory of Physicochemistry of Coordination Complexes
, Wioletta Żmudzińska PSB
Wioletta Żmudzińska,,
- Laboratory of Biopolymers Structure
, Dorota Uber PFZK
Dorota Uber ,,
- Laboratory of Physicochemistry of Coordination Complexes
, Małgorzata Wierzbicka PFotobiofizyki
Małgorzata Wierzbicka,,
- Laboratory of Photobiophysics
, Wiesław Wiczk PFotobiofizyki
Wiesław Wiczk,,
- Laboratory of Photobiophysics
, Lech Chmurzyński PFZK
Lech Chmurzyński,,
- Laboratory of Physicochemistry of Coordination Complexes
Journal seriesBiophysical Chemistry, ISSN 0301-4622
Issue year2016
Vol216
Pages44-50
Publication size in sheets0.5
Keywords in EnglishAβ(1-42) fragments, fluorescence quenching, metal-peptide binding, isothermal titration calorimetry, molecular dynamics simulations
DOIDOI:10.1016/j.bpc.2016.06.006
URL http://dx.doi.org/10.1016/j.bpc.2016.06.006
Languageen angielski
Score (nominal)20
ScoreMinisterial score = 20.0, 20-12-2017, ArticleFromJournal
Ministerial score (2013-2016) = 20.0, 20-12-2017, ArticleFromJournal
Publication indicators WoS Impact Factor: 2016 = 2.402 (2) - 2016=2.121 (5)
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