title: Structure of the mammalian 80S initiation complex with initiation factor 5B on HCV-IRES RNA.
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.
authors: 1] Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany. [2].
authors: Hiroshi
authors: H
authors: Yamamoto
authors: 1] Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany. [2].
authors: Anett
authors: A
authors: Unbehaun
authors: Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany.
authors: Justus
authors: J
authors: Loerke
authors: Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany.
authors: Elmar
authors: E
authors: Behrmann
authors: Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany.
authors: Marianne
authors: M
authors: Collier
authors: 1] Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany. [2] UltraStrukturNetzwerk, Max Planck Institute for Molecular Genetics, Berlin, Germany.
authors: Jörg
authors: J
authors: Bürger
authors: 1] Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany. [2] UltraStrukturNetzwerk, Max Planck Institute for Molecular Genetics, Berlin, Germany.
authors: Thorsten
authors: T
authors: Mielke
authors: Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany.
authors: Christian M T
authors: CM
authors: Spahn
mesh_terms: D000818:Animals; D020285:Cryoelectron Microscopy; D039642:Eukaryotic Initiation Factors / Q000737:chemistry*; D005583:Fourier Analysis; D006165:Guanylyl Imidodiphosphate / Q000737:chemistry; D016174:Hepacivirus / Q000235:genetics*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012358:RNA, Transfer, Met / Q000737:chemistry; D012367:RNA, Viral / Q000737:chemistry*; D011817:Rabbits; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry*
chemical_list: D039642:Eukaryotic Initiation Factors; D012358:RNA, Transfer, Met; D012367:RNA, Viral; C451459:eukaryotic initiation factor-5B; D006165:Guanylyl Imidodiphosphate