Unusual Trigonal-Planar Copper Configuration Revealed in the Atomic Structure of Yeast Copper−Zinc Superoxide Dismutase

• Published in: Biochemistry (Easton) 1996-02, Vol.35 (7), p.2316-2321
• Main Authors: Ogihara, Nancy L, Parge, Hans E, Hart, P. John, Weiss, Manfred S, Goto, Joy J, Crane, Brian R, Tsang, Joyce, Slater, Kelly, Roe, James A, Valentine, Joan Selverstone, Eisenberg, David, Tainer, John A
• Format: Article
• Language: English
• Subjects: Crystallography, X-Ray; Electron Spin Resonance Spectroscopy; Fourier Analysis; Oxidation-Reduction; Protein Conformation; Saccharomyces cerevisiae - enzymology; Superoxide Dismutase - chemistry; SUPEROXIDO DISMUTASA; SUPEROXYDE DISMUTASE
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi951930b

The three-dimensional structure of yeast copper−zinc superoxide dismutase (CuZnSOD) has been determined in a new crystal form in space group R32 and refined against X-ray diffraction data using difference Fourier and restrained crystallographic refinement techniques. The unexpected result is that the copper ion has moved approximately 1 Å from its position in previously reported CuZnSOD models, the copper−imidazolate bridge is broken, and a roughly trigonal planar ligand geometry characteristic of CuI rather than CuII is revealed. Final R values for the two nearly identical room temperature structures are 18.6% for all 19 149 reflections in the 10.0−1.7 Å resolution range and 18.2% for 17 682 reflections (F > 2σ) in the 10.0−1.73 Å resolution range. A third structure has been determined using X-ray data collected at −180 °C. The final R value for this structure is 19.0% (R free = 22.9%) for all 24 356 reflections in the 10.0−1.55 Å resolution range. Virtually no change in the positions of the ligands to the zinc center is observed in these models. The origin of the broken bridge and altered Cu−ligand geometry is discussed.