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Issue 6, 2016
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Thermodynamics of Pb(ii) and Zn(ii) binding to MT-3, a neurologically important metallothionein

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Abstract

Isothermal titration calorimetry (ITC) was used to quantify the thermodynamics of Pb2+ and Zn2+ binding to metallothionein-3 (MT-3). Pb2+ binds to zinc-replete Zn7MT-3 displacing each zinc ion with a similar change in free energy (ΔG) and enthalpy (ΔH). EDTA chelation measurements of Zn7MT-3 and Pb7MT-3 reveal that both metal ions are extracted in a tri-phasic process, indicating that they bind to the protein in three populations with different binding thermodynamics. Metal binding is entropically favoured, with an enthalpic penalty that reflects the enthalpic cost of cysteine deprotonation accompanying thiolate ligation of the metal ions. These data indicate that Pb2+ binding to both apo MT-3 and Zn7MT-3 is thermodynamically favourable, and implicate MT-3 in neuronal lead biochemistry.

Graphical abstract: Thermodynamics of Pb(ii) and Zn(ii) binding to MT-3, a neurologically important metallothionein

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Supplementary files

Article information


Submitted
02 Aug 2015
Accepted
24 Dec 2015
First published
24 Dec 2015

Metallomics, 2016,8, 605-617
Article type
Paper
Author version available

Thermodynamics of Pb(II) and Zn(II) binding to MT-3, a neurologically important metallothionein

M. C. Carpenter, A. Shami Shah, S. DeSilva, A. Gleaton, A. Su, B. Goundie, M. L. Croteau, M. J. Stevenson, D. E. Wilcox and R. N. Austin, Metallomics, 2016, 8, 605
DOI: 10.1039/C5MT00209E

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