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The initiation of mammalian protein synthesis and mRNA scanning mechanism

Nature volume 500, pages 307–311 (2013)Cite this article

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Abstract

During translation initiation in eukaryotes, the small ribosomal subunit binds messenger RNA at the 5′ end and scans in the 5′ to 3′ direction to locate the initiation codon, form the 80S initiation complex and start protein synthesis. This simple, yet intricate, process is guided by multiple initiation factors. Here we determine the structures of three complexes of the small ribosomal subunit that represent distinct steps in mammalian translation initiation. These structures reveal the locations of eIF1, eIF1A, mRNA and initiator transfer RNA bound to the small ribosomal subunit and provide insights into the details of translation initiation specific to eukaryotes. Conformational changes associated with the captured functional states reveal the dynamics of the interactions in the P site of the ribosome. These results have functional implications for the mechanism of mRNA scanning.

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Figure 1: The crystal structure of rabbit pre-initiation complexes.
Figure 2: Interactions of tRNAi and eIF1A with the 40S subunit.
Figure 3: Path of the mRNA in the 48S PIC.
Figure 4: The latch and initiation factor eIF1.
Figure 5: Scanning model.

Accession codes

Accessions

Protein Data Bank

Data deposits

The structural coordinates of PIC1, PIC2 and 48S PIC have been deposited in the Protein Data Bank (http://www.rcsb.org/pdb) under accession codes 4KZX, 4KZY and 4KZZ, respectively.

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Acknowledgements

We thank the members of the Steitz laboratory for useful suggestions and discussions, the staff of the Advanced Photon Source beamline 24-ID, the National Synchrotron Light Source beamlines X25 and X29, and the Richards Center facility at Yale University for support. We also thank Y. Polikanov, J. Wang and Y. Xiong for advice with crystallographic software. This work was supported by the National Institutes of Health (NIH) grant GM022778 (to T.A.S.).

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Authors and Affiliations

  1. Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, 06520–8114, Connecticut, USA

    Ivan B. Lomakin & Thomas A. Steitz

  2. Howard Hughes Medical Institute, Yale University, New Haven, 06520–8114, Connecticut, USA

    Thomas A. Steitz

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  1. Ivan B. Lomakin
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I.B.L. designed and performed experiments, analysed data and wrote the paper; T.A.S. analysed data, wrote the paper and directed research.

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Correspondence to Ivan B. Lomakin or Thomas A. Steitz.

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Lomakin, I., Steitz, T. The initiation of mammalian protein synthesis and mRNA scanning mechanism. Nature 500, 307–311 (2013). https://doi.org/10.1038/nature12355

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