2012.04.02,Professor Zhou Congzhao Published a paper in Journal of Biological Chemistry,online

  • 2012.04.02,Professor Zhou Congzhao Published a paper entitled:"Structural snapshots of the yeast alkyl hydroperoxide reductase Ahp1 peroxiredoxin reveal a novel 2-cysteine mechanism of electron transfer to eliminate reactive oxygen species " in Journal of Biological Chemistry,online(doi:10.1074/jbc.M112.357368)
    Author:Lian Fuming、Yu Jiang、Ma Xiaoxiao、Yu Xiaojie、Chen Yuxing、Zhou Congzhao

    Abstract

    Peroxiredoxins (Prxs) are thiol-specific antioxidant proteins that protect cells against reactive oxygen species and are involved in cellular signaling pathways. Alkyl hydroperoxide reductase Ahp1 belongs to the Prx5 subfamily and is a 2-Cysteine (2-Cys) Prx that forms an intermolecular disulfide bond. Enzymatic assays and bioinformatics enabled us to re-assign the peroxidatic cysteine (CP) to Cys62 and the resolving cysteine (CR) to Cys31, but not the previously reported Cys120. Thus Ahp1 represents the first 2-Cys Prx with a peroxidatic cysteine following the resolving cysteine in the primary sequence. We also found that the positive cooperativity of the substrate tert-butyl hydroperoxide binding to Ahp1 homodimer at a Hill coefficient of approximately 2, which enabled Ahp1 to eliminate hydroperoxide at much higher efficiency. To gain the structural insights into the catalytic cycle of Ahp1, we determined the crystal structures of Ahp1 in the reduced, oxidized and Trx2-complexed forms at 2.40, 2.91 and 2.10 Å resolution, respectively. Structural superposition of the oxidized to the reduced form revealed significant conformational changes at the segments containing CP and CR. An intermolecular CP-CR disulfide bond crossing the A-type dimer interface distinguishes Ahp1 from other typical 2-Cys Prxs. The structure of the Ahp1-Trx2 complex showed, for the first time, how the electron transfers from thioredoxin to a peroxidase with a thioredoxin-like fold. In addition, site-directed mutagenesis in combination with enzymatic assays suggested that the peroxidase activity of Ahp1 would be altered upon the urmylation (covalently conjugated to ubiquitin-related modifier Urm1) of Lys32.

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