Structural basis for the transition from translation initiation to elongation by an 80S-eIF5B complex

By Jinfan Wang, Jing Wang, B. Shin, Joo-Ran Kim, T. Dever, Joseph D. Puglisi, I. S. Fernández. 2020

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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-tRNAiMet 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-tRNAiMet 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. The GTPase eIF5B is involved in the correct positioning of the initiator Met-tRNAiMet on the ribosome during the late stages of translation initiation. Here the authors present a cryo-EM structure of the ribosome in complex with eIF5B and Met-tRNAiMet immediately before transition into elongation, providing insight on Met-tRNAiMetdelivery and how the correct reading frame is established.

Subfields: Ecology, Molecular Biology