Investigation of the fine structure around the copper site in copper/zinc superoxide dismutase by XANES combined with ab initio calculations

Copper/zinc superoxide dismutase (CuZnSOD) is an important enzyme that plays a crucial role in protecting oxygen-metabolizing cells against harmful effects of superoxide free-radicals. In this work, the three-dimensional local structure around the copper-binding site in pH 7.0 buffer solution was determined using X-ray absorption near-edge spectroscopy (XANES) combined with ab initio calculations in the framework of the multiple-scattering theory performed by MXAN. Extremely accurate bond distances and bond angle information between ligands were returned. The result confirmed that the copper ion binds four conserved His residues and a water molecule in CuZnSOD and prefers a five-coordinated in a distorted square pyramidal geometry.