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Differently bound copper(I) in yeast Cu8-thionein
1Anorganische Biochemie, Physiologisch-chemisches Institut der Universität Tübingen, F.R.G.
Biochimica Et Biophysica Acta
|March 2, 1988
Summary
Yeast copper thionein (Cu-thionein) reactivity was studied using chelators. Results suggest distinct copper coordination types within Cu-thionein, indicating potential interconversion reactions of copper-thiolate centers.
Area of Science:
- Biochemistry
- Metalloprotein Chemistry
Background:
- Yeast copper thionein (Cu-thionein) is a metalloprotein with a high capacity for binding copper ions.
- Understanding the coordination state of copper within Cu-thionein is crucial for elucidating its biological functions.
Purpose of the Study:
- To investigate the reactivity of yeast Cu-thionein with specific Cu(I)-chelators.
- To differentiate between potential distinct coordination states of copper(I) within the protein.
Main Methods:
- Electronic absorption spectroscopy was employed to monitor the reaction kinetics.
- Circular dichroism was used to analyze changes in the copper-thiolate chromophores.
Main Results:
- Two of the eight copper ions in Cu-thionein reacted rapidly with bathocuproinesulphonate and cuproine.
- The characteristic Cotton bands of Cu(I)-thiolate chromophores remained unchanged, indicating the presence of spectro-silent copper.
- Removal of spectro-silent copper led to a significant increase in specific theta Cu values.
Conclusions:
- The findings strongly suggest the presence of at least two distinct types of copper(I) coordination within yeast Cu-thionein.
- The observed reactivity and spectral data imply possible interconversion reactions of copper(I)-thiolate centers, consistent with varying Cu/cysteine ratios in different organisms.