The hyperthermophilic archaeal sulredoxin from Sulfolobus tokodaii is a water-soluble high-potential Rieske [2Fe-2S] protein with unique pH-dependent redox properties compared with its mesophilic homologues in cytochrome bc1/b6f complexes. The oxidized recombinant sulredoxin has been crystallized by the hanging-drop vapour-diffusion method using 30%(v/v) polyethylene glycol 400, 0.1 M cadmium chloride and 0.1 M sodium acetate pH 4.6. The crystals diffracted to beyond 2.0 A resolution and belong to the cubic space group F4(1)32, with unit-cell parameter a = 163.00 +/- 0.05 A. The asymmetric unit contains one sulredoxin molecule. Three-wavelength MAD data were collected.