Structural insight into poplar glutaredoxin C1 with a bridging iron-sulfur cluster at the active site
Structural insight into poplar glutaredoxin C1 with a bridging iron-sulfur cluster at the active site
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活性位点具有桥接铁硫簇的杨树谷氧还蛋白 C1 的结构洞察
DOI：
10.1021/bi060444t
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发表时间：
2006-07-04
期刊：
影响因子：
2.9
通讯作者：
Xia, Bin
中科院分区：
文献类型：
--
作者：
Feng, Yingang;Zhong, Nan;Xia, Bin
谷氧还蛋白是谷胱甘肽依赖性酶，其功能是在体内还原二硫键。有趣的是，最近的一项发现表明，一些谷氧还蛋白也可以以另一种形式存在，即铁硫蛋白[Lillig，C. H、等人（2005）Proc.Natl. Acad. Sci.联合S. A. 102，8168-8173]。这提供了一个直接的连接之间的谷胱甘肽和铁-硫蛋白，这表明一个可能的新的调节作用的铁-硫簇沿着与新的功能开关的谷胱甘肽。生化研究表明，白杨谷氧还蛋白C1（Grx-C1）也是这样一种双型蛋白。Grx-C1的apo形式（单体）是一种常规的谷氧还蛋白，而holo形式（二聚体）是一种具有桥接[2Fe-2S]簇的铁硫蛋白。在这里，我们报告的结构表征白杨Grx-C1在两个apo和holo形式的NMR光谱。还原型载脂蛋白Grx-C1是第一个植物Grx结构，其溶液结构显示出典型的Grx折叠。当白杨Grx-C1与铁硫簇形成二聚体时，holo形式的每个亚基仍然保留apo形式的整体折叠。全Grx-C1中的桥连铁硫簇在活性中心附近配位。除了铁-硫簇连接体之外，每个亚基的螺旋α 3可能参与两个亚基之间的直接接触。此外，两个谷胱甘肽分子被确定在附近的铁-硫簇，很可能参与集群协调。综上所述，我们提出，桥接[2Fe-2S]簇是协调的第一个半胱氨酸在谷氧还蛋白活性位点从每个亚基的holo Grx-C1，沿着两个半胱氨酸从两个谷胱甘肽分子。我们的研究表明，holo Grx-C1具有新颖的铁硫蛋白结构和铁硫簇配位模式。
Glutaredoxins are glutathione-dependent enzymes that function to reduce disulfide bonds in vivo. Interestingly, a recent discovery indicates that some glutaredoxins can also exist in another form, an iron-sulfur protein [Lillig, C. H., et al. (2005) Proc. Natl. Acad. Sci. U. S. A. 102, 8168-8173]. This provides a direct connection between glutaredoxins and iron-sulfur proteins, suggesting a possible new regulatory role of iron-sulfur clusters along with the new functional switch of glutaredoxins. Biochemical studies have indicated that poplar glutaredoxin C1 (Grx-C1) is also such a biform protein. The apo form (monomer) of Grx-C1 is a regular glutaredoxin, and the holo form (dimer) is an iron-sulfur protein with a bridging [2Fe-2S] cluster. Here, we report the structural characterizations of poplar Grx-C1 in both the apo and holo forms by NMR spectroscopy. The solution structure of the reduced apo Grx-C1, which is the first plant Grx structure, shows a typical Grx fold. When poplar Grx-C1 forms a dimer with an iron-sulfur cluster, each subunit of the holo form still retains the overall fold of the apo form. The bridging iron-sulfur cluster in holo Grx-C1 is coordinated near the active site. In addition to the iron-sulfur cluster linker, helix alpha 3 of each subunit is probably involved in the direct contact between the two subunits. Moreover, two glutathione molecules are identified in the vicinity of the iron-sulfur cluster and very likely participate in cluster coordination. Taken together, we propose that the bridging [2Fe-2S] cluster is coordinated by the first cysteine at the glutaredoxin active site from each subunit of holo Grx-C1, along with two cysteines from two glutathione molecules. Our studies reveal that holo Grx-C1 has a novel structural and iron-sulfur cluster coordination pattern for an iron-sulfur protein.