title: Crystallization of a nickel-containing superoxide dismutase and preliminary phase determination by MAD at the Ni K edge.
abstract: Superoxide dismutases are metalloenzymes which catalyse the disproportion of superoxide radicals and thus play an important role in the protection of biomolecules from oxidative damage. Redox-active metal ions known to act as the catalytic centre of these enzymes are Cu, Mn or Fe. Recently, enzymes containing Ni have been found in various Streptomyces species, introducing a fourth type of metal ion to the superoxide dismutase family. NiSOD has been crystallized for the purpose of structure determination by X-ray crystallography using Ni as an anomalous scatterer in multiple-wavelength anomalous dispersion (MAD) experiments. Two crystal forms belonging to space group P2(1)2(1)2(1) and one belonging to space group R3 were obtained using ammonium sulfate as a precipitant. Patterson maps of one of the orthorhombic forms revealed the presence of pseudo-translation, which could be removed for the other orthorhombic form by using 10% glycerol in its crystallization conditions. In addition, this reduced the unit cell by half. Phase information which led to interpretable electron-density maps was derived from MAD data to 2.0 A resolution after density modification applying solvent flattening, histogram matching and NCS averaging. Phases were extended to 1.68 A resolution with a data set collected at a wavelength of 1 A. Model building based on the resulting electron-density maps is in progress.
authors.affiliation: International School For Advanced Studies, Via Beirut 2-4, I-34014 Trieste, Italy.
authors.forename: Jochen
authors.initials: J
authors.lastname: Wuerges
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Lee
authors.forename: Sa Ouk
authors.initials: SO
authors.lastname: Kang
authors.forename: Kristina
authors.initials: K
authors.lastname: Djinovic Carugo
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray / Q000379:methods*; D004583:Electrons; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D013302:Streptomyces / Q000201:enzymology; D013482:Superoxide Dismutase / Q000737:chemistry*
chemical_list: D009532:Nickel; D013482:Superoxide Dismutase