Mechanism of ribosome rescue by ArfA and RF2
Mechanism of ribosome rescue by ArfA and RF2
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DOI：
10.7554/elife.23687
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发表时间：
2017-03-16
期刊：
影响因子：
7.7
通讯作者：
Korostelev, Andrei A.
中科院分区：
文献类型：
--
作者：
Demo, Gabriel;Svidritskiy, Egor;Korostelev, Andrei A.
ARFA通过招募释放因子RF2来拯救停滞在被截断的mRNAs上的核糖体，RF2通常与终止密码子结合以催化肽释放。我们报告了两个3.2埃分辨率的低温EM结构--由单个样本确定--在A位带有ArfA.RF2的70年代核糖体。在这两种状态下，Arfa C末端占据了A位点下游的mRNA隧道。一种状态包含致密的非活性RF2构象。ArfA N-末端在第二状态的排序将RF2重新排列成扩展的构象，将催化GGQ基序对接到肽基转移酶中心。因此，我们的工作揭示了核糖体拯救的结构动力学。这些结构展示了ARFA是如何“感知”空置的mRNA隧道并激活RF2，在没有停止密码子的情况下介导肽的释放，从而使停滞的核糖体得以回收利用。
ArfA rescues ribosomes stalled on truncated mRNAs by recruiting release factor RF2, which normally binds stop codons to catalyze peptide release. We report two 3.2 angstrom resolution cryo-EM structures - determined from a single sample - of the 70S ribosome with ArfA.RF2 in the A site. In both states, the ArfA C-terminus occupies the mRNA tunnel downstream of the A site. One state contains a compact inactive RF2 conformation. Ordering of the ArfA N-terminus in the second state rearranges RF2 into an extended conformation that docks the catalytic GGQ motif into the peptidyl-transferase center. Our work thus reveals the structural dynamics of ribosome rescue. The structures demonstrate how ArfA 'senses' the vacant mRNA tunnel and activates RF2 to mediate peptide release without a stop codon, allowing stalled ribosomes to be recycled.