Related Experiment Video
Updated: Apr 26, 2026

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
Published on: May 10, 2018
Structure of the mammalian 80S initiation complex with initiation factor 5B on HCV-IRES RNA
Hiroshi Yamamoto1, Anett Unbehaun1, Justus Loerke2
11] Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany. [2].
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.
Related Concept Videos
Initiation of Translation
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
Initiation of Translation
General Transcription Factors
Transcription Initiation
The promoters and enhancers and their accessory proteins allow tight regulation of...
Leaky Scanning
Ribosomes
Ribosome Structure and Assembly
Ribosomes are composed of ribosomal RNA (rRNA) and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus—a part of the nucleus that specializes in ribosome...

