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Updated: May 22, 2026
14:44
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Outer-sphere contributions to the electronic structure of type zero copper proteins
Kyle M Lancaster1, María-Eugenia Zaballa, Stephen Sproules
1California Institute of Technology, Pasadena, California 91125, United States. kml236@cornell.edu
Journal of the American Chemical Society
|May 9, 2012
Summary
Researchers discovered novel "type zero" copper sites in proteins, challenging the bioinorganic canon. These sites, lacking thiolate coordination, exhibit unique electronic structures and electron transfer properties.
Area of Science:
- Bioinorganic chemistry
- Biophysics
- Protein engineering
Background:
- The established bioinorganic canon posits that active-site thiolate coordination is essential for rapid electron transfer (ET) in type 1 copper proteins.
- Recent findings indicate that copper ET sites can be engineered without thiolate ligation, termed "type zero" sites.
Purpose of the Study:
- To investigate the structural and electronic properties of type zero copper sites in Pseudomonas aeruginosa azurin variants.
- To compare the electronic structures of type zero sites with wild-type (type 1) and type 2 copper centers.
Main Methods:
- Multifrequency electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), and nuclear magnetic resonance (NMR) spectroscopy.
- Density functional theory (DFT) and spectroscopy-oriented configuration interaction (SORCI) calculations.
- Quantum mechanics/molecular mechanics (QM/MM) simulations.
Main Results:
- Type zero copper centers in Pseudomonas aeruginosa azurin variants exhibit ligand fields virtually identical to wild-type type 1 centers.
- Enhanced O-donor covalency and reduced N-donor covalency were observed in type zero centers compared to type 1 and type 2 proteins.
- Electronic structures of type zero and type 2 sites are strongly influenced by the carboxylate ligand's orientation and coordination, modulated by outer-sphere hydrogen bonding.
Conclusions:
- Type zero copper sites represent a viable alternative to traditional type 1 sites for modulating electron transfer properties.
- The coordination and orientation of carboxylate ligands, influenced by hydrogen bonding, are critical determinants of electronic structure in non-thiolate copper centers.
- This study expands the understanding of copper protein active sites and offers new avenues for protein engineering.
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