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How to hide zinc in a small protein
Claudia A Blindauer1, Peter J Sadler
1School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.
Accounts of Chemical Research
|January 19, 2005
Summary
Proteins like metallothioneins bind zinc clusters, mimicking mineral structures. Bacteria utilize unique zinc-binding folds, demonstrating precise protein control over zinc and related metal interactions.
Area of Science:
- Biochemistry
- Structural Biology
- Bioinorganic Chemistry
Background:
- Metallothioneins are small cysteine-rich proteins that bind metal ions.
- Zinc clusters in proteins can adopt structures similar to Zn(II) sulfide minerals.
- Bacterial metallothioneins exhibit unique zinc-binding motifs.
Purpose of the Study:
- To investigate the structural diversity and functional properties of zinc clusters in proteins.
- To explore the mechanisms of zinc binding and exchange in bacterial metallothioneins.
- To understand protein-mediated control over zinc cluster thermodynamics and kinetics.
Main Methods:
- Bioinformatic analysis of metallothionein and related protein sequences.
- Structural characterization of zinc-ligand interactions.
- Metal exchange assays to probe binding kinetics and thermodynamics.
Main Results:
- Proteins bind tri- and tetranuclear zinc clusters with topologies resembling Zn(II) sulfide mineral fragments.
- Bacterial metallothioneins can incorporate histidines and form "treble-clef" zinc-finger folds.
- Embedded zinc in bacterial folds is inert to Zn or Cd exchange, indicating fine protein control.
Conclusions:
- Proteins exhibit remarkable control over the thermodynamics and kinetics of zinc binding in thiolate clusters.
- The prevalence of related zinc-finger sites in bacteria suggests significant biological roles.
- Structural diversity in zinc cluster binding contributes to varied protein functions across species.