A CDC25 homologue from rice functions as an arsenate reductase
A CDC25 homologue from rice functions as an arsenate reductase
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DOI：
10.1111/j.1469-8137.2007.02009.x
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发表时间：
2007-01-01
期刊：
影响因子：
9.4
通讯作者：
Zhu, Yong-Guan
中科院分区：
文献类型：
--
作者：
Duan, Gui-Lan;Zhou, Yao;Zhu, Yong-Guan
酶催化砷酸盐还原为亚砷酸盐是所有生物体内砷酸盐代谢的第一步。水稻基因组中含有两个与砷代谢有关的类ACR 2基因OsACR2.1和OsACR2.2，本研究克隆了这两个基因，并在缺失arsC基因的大肠杆菌和缺失ACR 2基因的酿酒酵母中进行了表达。OsACR2.1补充了E.大肠杆菌和酵母菌。OsACR2.2基因表达产物经纯化后，在体外能将砷酸盐还原为亚砷酸盐，并具有磷酸酶活性。与互补结果一致，OsACR2.1表现出比OsACR2.2更高的还原酶活性。在推测的活性位点HC（X）（5）R基序上半胱氨酸残基的突变导致磷酸酶和砷酸盐还原酶活性几乎完全丧失。OsACR2.2仅在砷暴露后的根中观察到，并且其表达低于OsACR2.1。
Enzymatic reduction of arsenate to arsenite is the first step in arsenate metabolism in all organisms studied. The rice genome contains two ACR2-like genes, OsACR2.1 and OsACR2.2, which may be involved in regulating arsenic metabolism in rice.Here, we cloned both OsACR2 genes and expressed them in an Escherichia coli strain in which the arsC gene was deleted and in a yeast (Saccharomyces cerevisiae) strain with a disrupted ACR2 gene. OsACR2.1 complemented the arsenate hypersensitive phenotype of E. coli and yeast. OsACR2.2 showed much less ability to complement.The gene products were purified and demonstrated to reduce arsenate to arsenite in vitro, and both exhibited phosphatase activity. In agreement with the complementation results, OsACR2.1 exhibited higher reductase activity than OsACR2.2. Mutagenesis of cysteine residues in the putative active site HC(X)(5)R motif led to nearly complete loss of both phosphatase and arsenate reductase activities.In planta expression of OsACR2.1 increased dramatically after exposure to arsenate. OsACR2.2 was observed only in roots following arsenate exposure, and its expression was less than OsACR2.1.