The binding mechanism of eIF2β with its partner proteins, eIF5 and eIF2Bε, Biochem
The binding mechanism of eIF2β with its partner proteins, eIF5 and eIF2Bε, Biochem
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eIF2β与其伴侣蛋白eIF5和eIF2Bε的结合机制，Biochem
DOI：
10.1016/j.bbrc.2012.05.155
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Yao M
中科院分区：
文献类型：
--
作者：
Gai Z;Kitagawa Y;Tanaka Y;Shimizu N;Komoda K;Tanaka I;Yao M
真核生物翻译起始因子eIF 2将Met-tRNAiMet以与eIF 1、eIF 1A、eIF 3和eIF 5相关的GTP结合形式递送至核糖体小亚基，并在Met-tRNAiMet与mRNA之间形成起始密码子-反密码子碱基配对后，与eIF 5一起从核糖体小亚基解离为eIF 5-eIF 2-GDP复合物。然后通过eIF 2B将非活性形式eIF 2-GDP交换为活性形式eIF 2-GTP，以进行进一步的起始循环。先前的研究表明eIF 5和eIF 2B ε的C端结构域（eIF 5-CTD）和eIF 2B ε（eIF 2B ε-CTD）具有共同的eIF 2 β结合位点，用于与eIF 2 β的N端区域（eIF 2 β-NTD）相互作用。本研究在体外构建了（eIF 5-CTD）-（eIF 2 β-NTD）和（eIF 2B ε-CTD）-（eIF 2 β-NTD）复合物，并通过圆二色谱和小角X射线散射研究了其结合机理。结果表明，eIF 2 β-NTD在与伴侣蛋白结合时构象发生变化，而eIF 5-CTD和eIF 2B ε-CTD在分离态和复合态的结构相似。我们认为eIF 2 β-NTD是一个本质上无序的结构域，在分离状态下是无序的，但当与其伴侣蛋白结合时折叠成确定的结构。预期eIF 2 β-NTD的这种柔性是其结合能力的原因。
The eukaryotic translation initiation factor eIF2 delivers Met-tRNAiMetto the ribosomal small subunit in GTP-bound form associated with eIF1, eIF1A, eIF3 and eIF5, and dissociates together with eIF5 as eIF5-eIF2-GDP complex from the ribosomal small subunit after formation of start codon–anticodon base pairing between Met-tRNAiMetand mRNA. The inactive form eIF2-GDP is then exchanged for the active form eIF2-GTP by eIF2B for further initiation cycle. Previous studies showed that the C-terminal domains of eIF5 (eIF5-CTD) and eIF2Bε (eIF2Bε-CTD) have a common eIF2β-binding site for interacting with an N-terminal region of eIF2β (eIF2β-NTD). Here we have reconstructed the complexes of (eIF5-CTD)-(eIF2β-NTD) and (eIF2Bε-CTD)-(eIF2β-NTD) in vitro, and investigated binding mechanism by circular dichroism spectroscopy and small angle X-ray scattering in solution. The results showed the conformation of eIF2β-NTD was changed when bound to partner proteins, whereas the structures of eIF5-CTD and eIF2Bε-CTD were similar in both isolated and complex states. We propose that eIF2β-NTD works as an intrinsically disordered domain which is disorder in the isolated state, but folds into a definite structure when bound to its partner proteins. Such flexibility of eIF2β-NTD is expected to be responsible for its binding capability.