Improvement of the Diffraction Properties of Thiocyanate Dehydrogenase Crystals

During determination of the thiocyanate dehydrogenase (TcDH) structure difficulties have occurred, related to the fact that enzyme crystals have been either twinned or strongly anisotropic. The diffraction quality of crystals can be improved by using mutant forms as objects of a study or by studying the structure of a related enzyme from another organism. Based on the analysis of the oligomeric structure of TcDH, the mutant forms of the enzyme that are promising for improving the diffraction properties have been proposed. The crystals have been obtained and the structures of the TcDH mutant forms with the substitutions T169A and K281A have been solved. The structure of the mutant form with the substitution T169A is found to be similar to the previously solved structures. In the structure of the mutant form with the substitution K281A, a change in the tetramer structure that made twinning impossible has been detected.