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Copper(I) transfer into metallothionein mediated by glutathione
A M Ferreira1, M R Ciriolo, L Marcocci
1Department of Biology, Tor Vergata, University of Rome, Italy.
The Biochemical Journal
|June 15, 1993
Summary
Copper-glutathione (Cu(I)-GSH) efficiently reconstitutes metallothionein, acting as a potential physiological copper carrier. GSH also protects metallothionein from oxidation and aids copper binding.
Area of Science:
- Biochemistry
- Metalloprotein Chemistry
Background:
- Metallothionein (MT) is a metal-binding protein involved in detoxification and homeostasis.
- Understanding the physiological mechanisms of MT metal reconstitution is crucial.
Purpose of the Study:
- To investigate the efficacy of copper-glutathione (Cu(I)-GSH) complex in reconstituting metallothionein.
- To explore the role of GSH in copper binding to metallothionein.
Main Methods:
- Anaerobic fluorescence titration to monitor Cu(I) insertion into MT.
- Comparative analysis of Cu(I) reconstitution using different copper complexes (Cu(I)-GSH, Cu(I)-thiourea, Cu(I)-acetonitrile).
- Investigation of Cu(I)-GSH complex's ability to displace Zn(II) and Cd(II) from MT.
Main Results:
- Cu(I)-GSH fully reconstituted apo-metallothionein under anaerobic conditions, with binding stoichiometry matching available sites.
- Cu(I)-GSH was significantly more efficient than other tested copper complexes.
- In the presence of GSH, stoichiometric copper reconstitution of MT was achieved even in air.
- Cu(I)-GSH displaced existing Zn(II) and Cd(II) from metallothionein.
Conclusions:
- Cu(I)-GSH is a viable physiological carrier for copper, particularly for metallothionein.
- Glutathione (GSH) protects metallothionein from oxidative damage and facilitates copper-thiolate exchange.
- The natural metal composition of metallothionein may reflect metal availability rather than protein structural evolution.