Structural basis of redox-dependent substrate binding of protein disulfide isomerase.
Structural basis of redox-dependent substrate binding of protein disulfide isomerase.
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DOI：
10.1038/srep13909
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发表时间：
2015-09-09
影响因子：
4.6
通讯作者：
Kato K
中科院分区：
文献类型：
--
作者：
Yagi-Utsumi M;Satoh T;Kato K
蛋白质二硫键异构酶（Protein disulfide isomerase，PDI）是一种多结构域酶，是一种重要的折叠催化剂，其中B′和a′结构域提供底物结合位点，并根据a′结构域的氧化还原状态进行开-闭结构域重排。尽管这种酶的研究历史很长，但其配体结合模式的三维结构数据仍然不可用。在这里，我们使用α-突触核蛋白（αSN）作为模型配体表征PDI底物识别。我们的核磁共振（NMR）数据显示，PDI的底物结合结构域仅以氧化形式捕获αSN片段Val 37-Val 40。此外，我们确定了与对应于该片段的十一肽复合的B′-a′结构域的氧化形式的晶体结构。通过NMR验证在晶体结构中观察到的肽结合模式的特征在于开放构象中B′结构域上的疏水相互作用。与先前报道的晶体结构的比较表明，a '结构域部分地掩蔽了B'结构域的结合表面，导致对呈现封闭构象的还原形式的B '-a'结构域的肽的空间位阻。这些研究结果提供了一个结构基础的机制的氧化还原依赖性底物结合的PDI。
Protein disulfide isomerase (PDI) is a multidomain enzyme, operating as an essential folding catalyst, in which the b′ and a′ domains provide substrate binding sites and undergo an open–closed domain rearrangement depending on the redox states of the a′ domain. Despite the long research history of this enzyme, three-dimensional structural data remain unavailable for its ligand-binding mode. Here we characterize PDI substrate recognition using α-synuclein (αSN) as the model ligand. Our nuclear magnetic resonance (NMR) data revealed that the substrate-binding domains of PDI captured the αSN segment Val37–Val40 only in the oxidized form. Furthermore, we determined the crystal structure of an oxidized form of the b′–a′ domains in complex with an undecapeptide corresponding to this segment. The peptide-binding mode observed in the crystal structure with NMR validation, was characterized by hydrophobic interactions on the b′ domain in an open conformation. Comparison with the previously reported crystal structure indicates that the a′ domain partially masks the binding surface of the b′ domain, causing steric hindrance against the peptide in the reduced form of the b′–a′ domains that exhibits a closed conformation. These findings provide a structural basis for the mechanism underlying the redox-dependent substrate binding of PDI.