Crystal structures of a poplar thioredoxin peroxidase that exhibits the structure of glutathione peroxidases: Insights into redox-driven conformational changes
Crystal structures of a poplar thioredoxin peroxidase that exhibits the structure of glutathione peroxidases: Insights into redox-driven conformational changes
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DOI：
10.1016/j.jmb.2007.04.031
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发表时间：
2007-07-13
影响因子：
5.6
通讯作者：
Corbier, Catherine
中科院分区：
文献类型：
--
作者：
Koh, Cha San;Didierjean, Claude;Corbier, Catherine
谷胱甘肽过氧化物酶（GPXs）是一组调节细胞和组织中活性氧水平并保护它们免受氧化损伤的酶。与动物细胞中的大多数同类酶不同，到目前为止所鉴定的高等植物GPX同源物在其活性位点含有半胱氨酸而非硒代半胱氨酸。有趣的是，植物GPXs在体外不依赖谷胱甘肽，而是依赖硫氧还蛋白作为电子供体。我们利用硒代甲硫氨酸衍生物确定了美洲黑杨×三角叶杨GPX5（PtGPX5）还原态和氧化态的晶体结构。PtGPX5呈现出与已知动物GPXs相似的整体结构。PtGPX5以假定的生理二聚体形式结晶，显示出一个假十链β折叠核心。对两种氧化还原结构的比较表明，需要剧烈的构象变化才能使两个相距较远的半胱氨酸残基靠近形成分子内二硫键。此外，基于氧化态酶的晶体堆积，提出了PtGPX5及其体外循环伙伴硫氧还蛋白h1复合物的计算机模型。还讨论了PtGPX5作为重金属汇的可能作用。（c）2007爱思唯尔有限公司。保留所有权利。
Glutathione peroxidases (GPXs) are a group of enzymes that regulate the levels of reactive oxygen species in cells and tissues, and protect them against oxidative damage. Contrary to most of their counterparts in animal cells, the higher plant GPX homologues identified so far possess cysteine instead of selenocysteine in their active site. Interestingly, the plant GPXs are not dependent on glutathione but rather on thioredoxin as their in vitro electron donor. We have determined the crystal structures of the reduced and oxidized form of Populus trichocarpa x deltoides GPX5 (PtGPX5), using a selenomethionine derivative. PtGPX5 exhibits an overall structure similar to that of the known animal GPXs. PtGPX5 crystallized in the assumed physiological dimeric form, displaying a pseudo ten-stranded beta sheet core. Comparison of both redox structures indicates that a drastic conformational change is necessary to bring the two distant cysteine residues together to form an intramolecular disulfide bond. In addition, a computer model of a complex of PtGPX5 and its in vitro recycling partner thioredoxin h1 is proposed on the basis of the crystal packing of the oxidized form enzyme. A possible role of PtGPX5 as a heavy-metal sink is also discussed. (c) 2007 Elsevier Ltd. All rights reserved.