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Structure of the mammalian 80S initiation complex with initiation factor 5B on HCV-IRES RNA

MPS-Authors
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Behrmann,  E.
Research Group Structural Dynamics of Proteins, Center of Advanced European Studies and Research (caesar), Max Planck Society;

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Bürger,  Jörg
Microscopy and Cryo-Electron Microscopy (Head: Thorsten Mielke), Scientific Service (Head: Christoph Krukenkamp), Max Planck Institute for Molecular Genetics, Max Planck Society;

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Mielke,  Thorsten
Microscopy and Cryo-Electron Microscopy (Head: Thorsten Mielke), Scientific Service (Head: Christoph Krukenkamp), Max Planck Institute for Molecular Genetics, Max Planck Society;

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Citation

Yamamoto, H., Unbehaun, A., Loerke, J., Behrmann, E., Collier, M., Bürger, J., et al. (2014). Structure of the mammalian 80S initiation complex with initiation factor 5B on HCV-IRES RNA. Nature Structural and Molecular Biology, 21(8), 721-727. doi:10.1038/nsmb.2859.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0029-B244-0
Abstract
The universally conserved eukaryotic initiation factor (eIF) 5B, a translational GTPase, is essential for canonical translation initiation. It is also required for initiation facilitated by the internal ribosomal entry site (IRES) of hepatitis C virus (HCV) RNA. eIF5B promotes joining of 60S ribosomal subunits to 40S ribosomal subunits bound by initiator tRNA (Met-tRNAi(Met)). However, the exact molecular mechanism by which eIF5B acts has not been established. Here we present cryo-EM reconstructions of the mammalian 80S-HCV-IRES-Met-tRNAi(Met)-eIF5B-GMPPNP complex. We obtained two substates distinguished by the rotational state of the ribosomal subunits and the configuration of initiator tRNA in the peptidyl (P) site. Accordingly, a combination of conformational changes in the 80S ribosome and in initiator tRNA facilitates binding of the Met-tRNAi(Met) to the 60S P site and redefines the role of eIF5B as a tRNA-reorientation factor.