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Updated: Jul 17, 2026
14:44
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Electron-mediating Cu(A) centers in proteins: a comparative high field (1)H ENDOR study
Boris Epel1, Claire S Slutter, Frank Neese
1Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
Journal of the American Chemical Society
|July 4, 2002
Summary
High-field electron-nuclear double resonance (ENDOR) reveals spin density distribution in copper A centers of various proteins. This study correlates structural features with electron-transfer functionality, offering insights into protein mechanisms.
Area of Science:
- Biophysics
- Biochemistry
- Spectroscopy
Background:
- The binuclear copper A (Cu(A)) center is crucial for electron transfer in proteins like nitrous oxide reductase and cytochrome c oxidase.
- Understanding the electronic structure and spin density distribution of the Cu(A) center is key to elucidating its function.
- High-field pulsed electron-nuclear double resonance (ENDOR) is a powerful technique for probing metal-ligand interactions in metalloproteins.
Purpose of the Study:
- To investigate the spin density distribution within the Cu(A) center of various proteins using high-field (W-band) pulsed ENDOR.
- To correlate structural features with electron-transfer properties by analyzing hyperfine interactions of cysteine and histidine protons.
- To compare the electronic and structural characteristics of the Cu(A) center across different protein environments.
Main Methods:
- High-field (95 GHz) pulsed electron-nuclear double resonance (ENDOR) measurements on nitrous oxide reductase (N(2)OR), Thermus thermophilus cytochrome c oxidase (COX) ba(3) (M160T9), its M160QT0 mutant, and engineered purple azurin (purpAz).
- Analysis of electron paramagnetic resonance (EPR) and ENDOR spectra to identify and characterize different proton signals (cysteine beta-protons, histidine H(epsilon)(1) protons, amide protons).
- Orientation-selective ENDOR spectroscopy and spectral simulations to determine isotropic and anisotropic hyperfine interactions and estimate sulfur spin densities.
Main Results:
- ENDOR spectra revealed distinct signals from strongly coupled cysteine beta-protons and weakly coupled protons, primarily histidine H(epsilon)(1) and amide protons.
- A linear correlation was observed between the isotropic hyperfine coupling of beta-protons and the copper hyperfine interaction.
- Sulfur spin densities and hyperconjugation contributions varied among the studied proteins, with M160T9 showing the largest and purpAz the lowest.
- Differences in the positions of imidazole rings relative to the Cu(2)S(2) core were inferred from the splitting patterns of weakly coupled protons.
Conclusions:
- High-field pulsed ENDOR successfully resolved and characterized hyperfine interactions within the Cu(A) centers of diverse proteins.
- The study provides quantitative estimates of spin density distribution and highlights the influence of protein structure on Cu(A) electronic properties.
- Findings suggest potential correlations between spin density distribution, structural nuances, and the electron-transfer functionality of the Cu(A) center.
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