Structural switching of Cu,Zn-superoxide dismutases at loop VI: insights from the crystal structure of 2-mercaptoethanol-modified enzyme.
Structural switching of Cu,Zn-superoxide dismutases at loop VI: insights from the crystal structure of 2-mercaptoethanol-modified enzyme.
复制标题
Cu，Zn-塞氧化物歧化酶在环VI上的结构切换：从2-羟基乙醇改性酶的晶体结构中的见解。
DOI：
10.1042/bsr20120029
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发表时间：
2012-12
影响因子：
4
通讯作者：
Suzuki K
中科院分区：
文献类型：
--
作者：
Ihara K;Fujiwara N;Yamaguchi Y;Torigoe H;Wakatsuki S;Taniguchi N;Suzuki K
Cu，Zn SOD 1（超氧化物歧化酶1）通过对神经元细胞有毒的错误折叠蛋白质的积累而与FALS（家族性肌萎缩侧索硬化症）有关。蛋白质的环VI（残基102-115）在二聚体界面处，并且可以在稳定性中起关键作用。环中的游离半胱氨酸残基Cys 111易于氧化和烷基化。我们已经发现，用2-ME（2-巯基乙醇; 2-ME-SOD 1）修饰该Cys 111可以稳定蛋白质，并且该机制可以提供对不稳定和聚集蛋白质形成的见解。在这里，我们确定了2-ME-SOD 1的晶体结构，并发现在两个亚基的2-ME部分相互作用不对称的二聚体界面，并有一个不对称的配置部分Gly 108 Cys 111在环VI。二聚体的一个环VI在由Ser 105-NH和His 110-CO之间的氢键稳定的独特β-桥内形成310-螺旋（Gly 108至His 110），而另一个环形成没有H-键的β-转角。氢键（H型）和无氢键（F型）构型也见于蛋白质数据库中的一些野生型和突变型人SOD 1中，表明它们是可相互转化的，是SOD 1的固有特性。这两种结构作为这些蛋白质分类的基础，并有望指导其稳定性和在病理生理学中的作用。
Cu,Zn SOD1 (superoxide dismutase 1) is implicated in FALS (familial amyotrophic lateral sclerosis) through the accumulation of misfolded proteins that are toxic to neuronal cells. Loop VI (residues 102–115) of the protein is at the dimer interface and could play a critical role in stability. The free cysteine residue, Cys111 in the loop, is readily oxidized and alkylated. We have found that modification of this Cys111 with 2-ME (2-mercaptoethanol; 2-ME-SOD1) stabilizes the protein and the mechanism may provide insights into destabilization and the formation of aggregated proteins. Here, we determined the crystal structure of 2-ME-SOD1 and find that the 2-ME moieties in both subunits interact asymmetrically at the dimer interface and that there is an asymmetric configuration of segment Gly108 to Cys111 in loop VI. One loop VI of the dimer forms a 310-helix (Gly108 to His110) within a unique β-bridge stabilized by a hydrogen bond between Ser105-NH and His110-CO, while the other forms a β-turn without the H-bond. The H-bond (H-type) and H-bond free (F-type) configurations are also seen in some wild-type and mutant human SOD1s in the Protein Data Bank suggesting that they are interconvertible and an intrinsic property of SOD1s. The two structures serve as a basis for classification of these proteins and hopefully a guide to their stability and role in pathophysiology.