Structural Understanding of the Glutathione-dependent Reduction Mechanism of Glutathionyl-Hydroquinone Reductases
Structural Understanding of the Glutathione-dependent Reduction Mechanism of Glutathionyl-Hydroquinone Reductases
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DOI：
10.1074/jbc.m112.395541
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发表时间：
2012-10-19
影响因子：
4.8
通讯作者：
Kang, ChulHee
中科院分区：
文献类型：
--
作者：
Green, Abigail R.;Hayes, Robert P.;Kang, ChulHee
谷胱甘肽对苯二酚还原酶（GS-HQRs）是一类新发现的谷胱甘肽转移酶，广泛存在于细菌、盐细菌、真菌和植物中。GS-HQR催化谷胱甘肽（GSH）依赖性还原谷胱甘肽-氢醌（GS-氢醌）为氢醌。GS-对苯二酚可由苯醌与还原型GSH通过迈克尔加成反应自发形成，并且GS-HQR将缀合物转化为对苯二酚。本文报道了两种细菌GS-HQR的结构，Sphingobium chlorophenolicum的PcpF和Escherichia coli的YqjG。这两种结构和以前报道的真菌GS-HQR结构有许多共同的特征，并显示出所有关键残基的完全保守性。此外，我们得到了与GS-甲萘醌的二元配合物结构，其还原形式为GS-甲萘醌醇，是底物。该结构揭示了一个大的H-位点，可以容纳各种取代的氢醌和三个Tyr残基的氢网络，可以提供还原脱谷胱甘肽化的质子。Tyr残基的突变和两个GSH分子的位置证实了GS-HQR的拟议机制。GS-HQR在细菌、盐细菌、真菌和植物中的保守性增强了这些酶在醌代谢中的生理作用。
Glutathionyl-hydroquinone reductases (GS- HQRs) are a newly identified group of glutathione transferases, and they are widely distributed in bacteria, halobacteria, fungi, and plants. GS-HQRs catalyze glutathione (GSH)-dependent reduction of glutathionyl-hydroquinones (GS-hydroquinones) to hydroquinones. GS-hydroquinones can be spontaneously formed from benzoquinones reacting with reduced GSH via Michael addition, and GS-HQRs convert the conjugates to hydroquinones. In this report we have determined the structures of two bacterial GS-HQRs, PcpF of Sphingobium chlorophenolicum and YqjG of Escherichia coli. The two structures and the previously reported structure of a fungal GS-HQR shared many features and displayed complete conservation for all the critical residues. Furthermore, we obtained the binary complex structures with GS-menadione, which in its reduced form, GS-menadiol, is a substrate. The structure revealed a large H-site that could accommodate various substituted hydroquinones and a hydrogen network of three Tyr residues that could provide the proton for reductive deglutathionylation. Mutation of the Tyr residues and the position of two GSH molecules confirmed the proposed mechanism of GS-HQRs. The conservation of GS-HQRs across bacteria, halobacteria, fungi, and plants potentiates the physiological role of these enzymes in quinone metabolism.