CuZn Superoxide Dismutase Geometry Optimization, Energetics, and Redox Potential Calculations by Density Functional...

Area of Science:

• Biochemistry
• Computational Chemistry
• Structural Biology

Background:

• Copper zinc superoxide dismutase (CuZnSOD) is crucial for cellular defense against reactive oxygen species.
• Understanding its catalytic mechanism requires accurate structural and electronic property calculations.

Purpose of the Study:

• To investigate the structures, energetics, and properties of CuZnSOD using computational methods.
• To determine the reduction potential and pK(a) of the CuZnSOD-catalyzed reaction.
• To assess the impact of the protein environment on CuZnSOD's function.

Main Methods:

• Density functional theory (DFT) and electrostatic methods were employed.
• A detailed model of CuZnSOD, including copper and zinc sites with coordinated ligands, was optimized.
• Poisson-Boltzmann methods were used to simulate the protein/solvent environment.

Main Results:

• Calculated geometrical parameters using nonlocal functionals showed good agreement with experimental X-ray data.
• The His61 Nepsilon-Cu bond breaking during reduction/protonation was consistent with experimental evidence.
• Redox potential and pK(a) predictions using the full protein environment model matched experimental values excellently.

Conclusions:

• The full protein environment is essential for accurately describing the redox process in CuZnSOD.
• The zinc ion, while not directly redox-active, significantly influences the catalytic mechanism.
• Computational modeling provides valuable insights into the function of metalloenzymes like CuZnSOD.