Structure of Sulfur-Substituted Rhodanese at 1.36 Å Resolution

1.36 Å resolution X-ray diffraction data have been recorded at 100 K for bovine liver sulfur-substituted rhodanese, using synchrotron radiation. The crystal structure has been refined anisotropically to a final R factor of 0.159 (Rfree = 0.229) for 53 034 unique reflections. The model contains 2 327 protein atoms and 407 solvent molecules, with a good geometry. The high resolution allows full details for helices, [beta]-sheets, tight turns and of all inter- and intramolecular interactions stabilizing the enzyme molecule to be given. The situation at the active site is described, particularly in regard to the network of hydrogen bonds made by S[gamma] and S[delta] of the sulfur-substituted catalytic Cys247 and surrounding groups and solvent molecules. The replacement of the precipitant ammonium sulfate with cryoprotectants in the crystal-suspending medium led to the removal of the sulfate ion from the enzyme active site. Only limited changes of the enzyme structure have been found as a result of the drastic change in the crystal medium.