A CALORIMETRIC STUDY ON THE INTERACTION OF ZINC ION WITH HUMAN GROWTH HORMONE

Document Type: Regular Paper

Authors

1 Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, I. R. of Iran

2 Institute of Biochemistry and Biophysics, University of Tehran, Tehran, I. R. of Iran

3 Department of Chemistry, Imam Khomeini International University, Qazvin, I. R. of Iran

Abstract

A thermodynamic study on the interaction between zinc ion (Zn2+) and human growth hormone
(hGH) was studied at two temperatures of 27C and 37C in aqueous solution using an isothermal titration
calorimetry. It was found that there is a set of three identical and non-interacting binding sites for Zn2+ ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 1.54 mM and 17.6 kJ mol-1 at 27C and 1.93 mM and 7.1 kJ mol-1 at 37C, respectively. To reproduce the binding parameters of metal ionhormone interaction over the whole range of Zn2+ concentrations a solvation theory was applied. The binding parameters deduced from the solvation model were attributed to the structural change of hGH and its biological activity due to the metal ion interaction

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