3sbc
Crystal structure of Saccharomyces cerevisiae TSA1C47S mutant proteinCrystal structure of Saccharomyces cerevisiae TSA1C47S mutant protein
Structural highlights
Function[TSA1_YEAST] Physiologically important antioxidant which constitutes an enzymatic defense against sulfur-containing radicals. Can provide protection against a thiol-containing oxidation system but not against an oxidation system without thiol. Publication Abstract from PubMed2-Cys peroxiredoxin (Prx) enzymes are ubiquitously distributed peroxidases that make use of a peroxidatic cysteine (Cys(P)) to decompose hydroperoxides. A disulfide bond is generated as a consequence of the partial unfolding of the alpha-helix that contains Cys(P). Therefore, during its catalytic cycle, 2-Cys Prx alternates between two states, locally unfolded and fully folded. Tsa1 (thiol-specific antioxidant protein 1 from yeast) is by far the most abundant Cys-based peroxidase in Saccharomyces cerevisiae. In this work, we present the crystallographic structure at 2.8A resolution of Tsa1(C47S) in the decameric form [(alpha(2))(5)] with a DTT molecule bound to the active site, representing one of the few available reports of a 2-Cys Prx (AhpC-Prx1 subfamily) (AhpC, alkyl hydroperoxide reductase subunit C) structure that incorporates a ligand. The analysis of the Tsa1(C47S) structure indicated that Glu50 and Arg146 participate in the stabilization of the Cys(P) alpha-helix. As a consequence, we raised the hypothesis that Glu50 and Arg146 might be relevant to the Cys(P) reactivity. Therefore, Tsa1(E50A) and Tsa1(R146Q) mutants were generated and were still able to decompose hydrogen peroxide, presenting a second-order rate constant in the range of 10(6)M(-1)s(-1). Remarkably, although Tsa1(E50A) and Tsa1(R146Q) were efficiently reduced by the low-molecular-weight reductant DTT, these mutants displayed only marginal thioredoxin (Trx)-dependent peroxidase activity, indicating that Glu50 and Arg146 are important for the Tsa1-Trx interaction. These results may impact the comprehension of downstream events of signaling pathways that are triggered by the oxidation of critical Cys residues, such as Trx. Disulfide biochemistry in 2-cys peroxiredoxin: requirement of Glu50 and Arg146 for the reduction of yeast Tsa1 by thioredoxin.,Tairum CA Jr, de Oliveira MA, Horta BB, Zara FJ, Netto LE J Mol Biol. 2012 Nov 23;424(1-2):28-41. doi: 10.1016/j.jmb.2012.09.008. Epub 2012, Sep 15. PMID:22985967[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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