Cloning, purification, crystallization and X-ray crystallographic analysis of Ignicoccus hospitalis neelaredoxin

Superoxide reductases (SORs) are metalloproteins which constitute the most recently identified oxygen-detoxification system in anaerobic and microaerobic bacteria and archaea. SORs are involved in scavenging superoxide radicals from the cell by catalyzing the reduction of superoxide (O-2(center dot-)) to hydrogen peroxide and are characterized by a catalytic nonhaem iron centre coordinated by four histidine ligands and one cysteine ligand. Ignicoccus hospitalis, a hyperthermophilic crenarchaeon, is known to have a neelaredoxin-type SOR that keeps toxic oxygen species levels under control. Blue crystals of recombinant I. hospitalis oxidized neelaredoxin (14.1 kDa, 124 residues) were obtained. These crystals diffracted to 2.4 angstrom resolution in-house at room temperature and belonged to the hexagonal space group P6(2)22 or P6(4)22, with unit-cell parameters a = b = 108, c = 64 angstrom. Cell-content analysis indicated the presence of one monomer in the asymmetric unit.