A gating mechanism for Pi release governs the mRNA unwinding by eIF4AI during translation initiation-猫眼课题宝

DOI：

10.1093/nar/gkv1033

发表时间：

2015-10

期刊：

Nucleic Acids Research

影响因子：

14.9

通讯作者：

中科院分区：

生物学2区

文献类型：

作者：

Junyan Lu;Chenxiao Jiang;Xiaojing Li;Lizhi Jiang;Zengxia Li;Tilman Schneider-Poetsch;Jianwei Liu;Kunqian Yu;Jun O. Liu;Hualiang Jiang;C. Luo;Yongjun Dang

真核翻译起始因子eIF4AI是DEAD盒解旋酶的创始成员，在翻译起始过程中经历ATP水解偶联的构象变化以解开mRNA二级结构。然而，其偶联酶活性的机制仍不清楚。在这里，我们报告说，由eIF4AI的域间连接器控制的Pi释放的门控机制调节ATP水解和RNA解旋之间的耦合。分子动力学模拟和实验结果表明，该接头通过N端保守的SAT基序和C端保守的I357形成疏水核心，控制Pi从水解位点释放，避免了eIF4AI的无效水解循环。进一步的诱变研究表明，该接头还在eIF4AI的酶活性中起着自抑制作用，这可能是其在翻译起始期间的功能所必需的。总的来说，我们的研究结果揭示了一种新的调控机制，控制eIF4AI介导的mRNA解旋，并可以指导其他DEAD盒解旋酶的进一步机制研究。

Eukaryotic translation initiation factor eIF4AI, the founding member of DEAD-box helicases, undergoes ATP hydrolysis-coupled conformational changes to unwind mRNA secondary structures during translation initiation. However, the mechanism of its coupled enzymatic activities remains unclear. Here we report that a gating mechanism for Pi release controlled by the inter-domain linker of eIF4AI regulates the coupling between ATP hydrolysis and RNA unwinding. Molecular dynamic simulations and experimental results revealed that, through forming a hydrophobic core with the conserved SAT motif of the N-terminal domain and I357 from the C-terminal domain, the linker gated the release of Pi from the hydrolysis site, which avoided futile hydrolysis cycles of eIF4AI. Further mutagenesis studies suggested this linker also plays an auto-inhibitory role in the enzymatic activity of eIF4AI, which may be essential for its function during translation initiation. Overall, our results reveal a novel regulatory mechanism that controls eIF4AI-mediated mRNA unwinding and can guide further mechanistic studies on other DEAD-box helicases.

A gating mechanism for Pi release governs the mRNA unwinding by eIF4AI during translation initiation

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