80S-eIF5B 复合物介导的从翻译起始到延伸的转变的结构基础。

Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.

Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, NY, USA.

Nat Commun. 2020 Oct 6;11(1):5003. doi: 10.1038/s41467-020-18829-3.

Recognition of a start codon by the initiator aminoacyl-tRNA determines the reading frame of messenger RNA (mRNA) translation by the ribosome. In eukaryotes, the GTPase eIF5B collaborates in the correct positioning of the initiator Met-tRNA on the ribosome in the later stages of translation initiation, gating entrance into elongation. Leveraging the long residence time of eIF5B on the ribosome recently identified by single-molecule fluorescence measurements, we determine the cryoEM structure of the naturally long-lived ribosome complex with eIF5B and Met-tRNA immediately before transition into elongation. The structure uncovers an unexpected, eukaryotic specific and dynamic fidelity checkpoint implemented by eIF5B in concert with components of the large ribosomal subunit.

核糖体通过起始氨酰-tRNA 识别起始密码子，从而决定信使 RNA（mRNA）翻译的阅读框。在真核生物中，GTP 酶 eIF5B 在翻译起始的后期阶段协同正确定位起始 Met-tRNA 在核糖体上，从而进入延伸阶段。最近通过单分子荧光测量确定了 eIF5B 在核糖体上的长停留时间，我们利用这一点，在自然状态下与 eIF5B 和 Met-tRNA 结合的核糖体复合物在进入延伸阶段之前确定了 cryoEM 结构。该结构揭示了一种出乎意料的、真核生物特有的、动态的保真度检查点，由 eIF5B 与大亚基的成分协同执行。