Mechanism of ribosome rescue by alternative ribosome-rescue factor B
Mechanism of ribosome rescue by alternative ribosome-rescue factor B
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DOI：
10.1038/s41467-020-17853-7
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发表时间：
2020-08-14
影响因子：
16.6
通讯作者：
Rodnina, Marina V.
中科院分区：
文献类型：
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作者：
Chan, Kai-Hsin;Petrychenko, Valentyn;Rodnina, Marina V.
替代核糖体拯救因子B（Arf B）通过从肽基-tRNA释放新生多肽来拯救停滞在非终止mRNA上的核糖体。通过快速动力学，我们表明，ArfB选择核糖体停滞在短截短的mRNA，而不是在较长的mRNA模仿暂停罕见的密码子簇。结合冷冻电子显微镜，我们解剖了ArfB的多步救援途径，它首先非常迅速地结合到核糖体上，而不管mRNA的长度。对较短mRNA的选择性来自随后的缓慢接合步骤，因为它需要较长的mRNA转移以实现ArfB结合。接合导致ArfB C-末端结构域与mRNA进入通道的特异性相互作用，其通过N-末端结构域激活肽基-tRNA水解。这些数据揭示了蛋白质动力学如何转化为底物识别的特异性，并提供了对线粒体中假定的拯救因子的作用的见解。
Alternative ribosome-rescue factor B (ArfB) rescues ribosomes stalled on non-stop mRNAs by releasing the nascent polypeptide from the peptidyl-tRNA. By rapid kinetics we show that ArfB selects ribosomes stalled on short truncated mRNAs, rather than on longer mRNAs mimicking pausing on rare codon clusters. In combination with cryo-electron microscopy we dissect the multistep rescue pathway of ArfB, which first binds to ribosomes very rapidly regardless of the mRNA length. The selectivity for shorter mRNAs arises from the subsequent slow engagement step, as it requires longer mRNA to shift to enable ArfB binding. Engagement results in specific interactions of the ArfB C-terminal domain with the mRNA entry channel, which activates peptidyl-tRNA hydrolysis by the N-terminal domain. These data reveal how protein dynamics translate into specificity of substrate recognition and provide insights into the action of a putative rescue factor in mitochondria.