title: Unusual trigonal-planar copper configuration revealed in the atomic structure of yeast copper-zinc superoxide dismutase.
abstract: 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 angstrom from its position in previously reported CuZnSOD models, the copper-imidazolate bridge is broken, and a roughly trigonal planar ligand geometry characteristic of Cu(I) rather than Cu(II) 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 angstrom resolution range and 18. 2% for 17 682 reflections (F > 2 sigma) in the 10.0-1.73 angstrom resolution range. A third structure has been determined using X-ray data collected at -180 degrees 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 angstrom 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.
authors.affiliation: UCLA-DOE Laboratory of Structural Biology and Molecular Medicine, University of California, Los Angeles 90095-1570, USA.
authors.forename: N L
authors.initials: NL
authors.lastname: Ogihara
authors.forename: H E
authors.initials: HE
authors.lastname: Parge
authors.forename: P J
authors.initials: PJ
authors.lastname: Hart
authors.forename: M S
authors.initials: MS
authors.lastname: Weiss
authors.forename: J J
authors.initials: JJ
authors.lastname: Goto
authors.forename: B R
authors.initials: BR
authors.lastname: Crane
authors.forename: J
authors.initials: J
authors.lastname: Tsang
authors.forename: K
authors.initials: K
authors.lastname: Slater
authors.forename: J A
authors.initials: JA
authors.lastname: Roe
authors.forename: J S
authors.initials: JS
authors.lastname: Valentine
authors.forename: D
authors.initials: D
authors.lastname: Eisenberg
authors.forename: J A
authors.initials: JA
authors.lastname: Tainer
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D005583:Fourier Analysis; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013482:Superoxide Dismutase / Q000737:chemistry*
chemical_list: D013482:Superoxide Dismutase