Crystallization and preliminary X-ray analysis of a decameric form of cytosolic thioredoxin peroxidase 1 (Tsa1), C47S mutant, from Saccharomyces cerevisiae

Saccharomyces cerevisiae cytosolic thioredoxin peroxidase 1 (cTPxI or Tsa1) is a bifunctional enzyme with protective roles in cellular defence against oxidative and thermal stress that exhibits both peroxidase and chaperone activities. Protein overoxidation and/or high temperatures induce great changes in its quaternary structure and lead to its assembly into large complexes that possess chaperone activity. A recombinant mutant of Tsa1 from S. cerevisiae, with Cys47 substituted by serine, was overexpressed in Escherichia coli as a His6‐tagged fusion protein and purified by nickel‐affinity chromatography. Crystals were obtained from protein previously treated with 1,4‐dithiothreitol by the hanging‐drop vapour‐diffusion method using PEG 3000 as precipitant and sodium fluoride as an additive. Diffraction data were collected to 2.8 Å resolution using a synchrotron‐radiation source. The crystal structure was solved by molecular‐replacement methods and structure refinement is currently in progress.