Investigations of copper(II) complexation by fragments of the FBP28 protein using isothermal titration (ITC) and differential scanning calorimetry (DSC)

Abstract

Isothermal titration calorimetry (ITC) was used to study the interactions between copper(II) ions and peptides with sequences taken from the N-terminal loop of the FBP28 protein (formin-binding protein) WW domain: AcLys-Thr-Ala-Asp-Gly-Lys-Thr-NH 2 (D7) and Ac-Tyr-LysThr-Ala-Asn-Gly-Lys-Thr-Tyr-NH 2 (D9 M), respectively. Measurements were taken at 298.15 K in 20 mM 2-(Nmorpholino)ethanesulfonic acid buffer solution at a pH of 6. The stoichiometry, conditional stability constants and thermodynamic parameters (D ITC G, D ITC H and D ITC S) for the pertinent complexation reactions were determined. Furthermore, the thermal stability of peptide conformations in the presence and absence of copper(II) in the system was investigated using differential scanning calorimetry. Finally, a general procedure on how to include the effect of buffer competition with the peptide for the metal as well as proton competition with the metal for the peptide and the buffer's component during ITC data analysis is described.

Isolation and identification of zinc‐chelating peptides from sea cucumber (Stichopus japonicus) protein hydrolysate

“…The higher positive value of Δ H of formation of metal and proteins can suggest a less covalent interaction character. Our results of Δ H (3.119 kJ mol −1 ) was comparatively higher than their reports (2.18 kJ mol −1 ), suggesting that the ZCPs of F3bIII might bind to zinc by low possibility of covalent bond. The endothermic curve stabilization at the end of titration (Fig.…”

“…Several studies have also reported that the enthalpy of interaction between metal ions and proteins is either endothermic or exothermic, including the interaction of zinc and peptides . Meanwhile, our study revealed that the binding of zinc to sea cucumber ZCPs is endothermic, with Δ H = 3.199 kJ mol −1 , which was similar to the binding between copper and the FBP28 protein . In their study, they mentioned that the thermodynamic stability of the complexes strongly depended on the entropy change.…”

“…31,33 Meanwhile, our study revealed that the binding of zinc to sea cucumber ZCPs is endothermic, with ΔH = 3.199 kJ mol −1 , which was similar to the binding between copper and the FBP28 protein. 34 In their study, they mentioned that the thermodynamic stability of the complexes strongly depended on the entropy change. The higher positive value of ΔH of formation of metal and proteins can suggest a less covalent interaction character.…”