Crystallization and preliminary X-ray diffraction studies of a hyperthermophilic Rieske protein variant (SDX-triple) with an engineered rubredoxin-like mononuclear iron site.

In place of the Rieske [2Fe-2S] cluster, an archetypal mononuclear iron site has rationally been designed into a hyperthermophilic archaeal Rieske [2Fe-2S] protein (sulredoxin) from Sulfolobus tokodaii by three residue replacements with reference to the Pyrococcus furiosus rubredoxin sequence. The resulting sulredoxin variant, SDX-triple (H44I/A45C/H64C), has been purified and crystallized by the hanging-drop vapour-diffusion method using 65%(v/v) 2-methyl-2,4-pentanediol, 0.025 M citric acid and 0.075 M sodium acetate trihydrate pH 4.3. The crystals diffract to 1.63 A resolution and belong to the triclinic space group P1, with unit-cell parameters a = 43.56, b = 76.54, c = 80.28 A, alpha = 88.12, beta = 78.82, gamma = 73.46 degrees. The asymmetric unit contains eight protein molecules.