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

Nat Struct Mol Biol. 2014 Aug;21(8):721-7. doi: 10.1038/nsmb.2859. Epub 2014 Jul 27.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cryoelectron Microscopy
  • Eukaryotic Initiation Factors / chemistry*
  • Fourier Analysis
  • Guanylyl Imidodiphosphate / chemistry
  • Hepacivirus / genetics*
  • Models, Molecular
  • Nucleic Acid Conformation
  • Protein Binding
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • RNA, Transfer, Met / chemistry
  • RNA, Viral / chemistry*
  • Rabbits
  • Ribosome Subunits, Large, Eukaryotic / chemistry*
  • Ribosome Subunits, Small, Eukaryotic / chemistry*


  • Eukaryotic Initiation Factors
  • RNA, Transfer, Met
  • RNA, Viral
  • eukaryotic initiation factor-5B
  • Guanylyl Imidodiphosphate

Associated data

  • PDB/4UPW
  • PDB/4UPX
  • PDB/4UPY
  • PDB/4UPZ
  • PDB/4UQ0
  • PDB/4UQ1
  • PDB/4UQ4
  • PDB/4UQ5