Purification, crystallization and phase determination of the DR1998 haem b catalase from Deinococcus radiodurans

The protective mechanisms of Deinococcus radiodurans against primary reactive oxygen species involve nonenzymatic scavengers and a powerful enzymatic antioxidant system including catalases, peroxidases and superoxide dismutases that prevents oxidative damage. Catalase is an enzyme that is responsible for the conversion of H₂O₂ to O₂ and H₂O, protecting the organism from the oxidative effect of H₂O₂. This study reports the purification and crystallization of the DR1998 catalase from D. radiodurans. The crystals diffracted to 2.6 Å resolution and belonged to space group C222₁, with unit-cell parameters a = 97.33, b = 311.88, c = 145.63 Å, suggesting that they contain four molecules per asymmetric unit. The initial phases were determined by molecular replacement and the obtained solution shows the typical catalase quaternary structure. A preliminary model of the protein structure has been built and refinement is currently in progress.