The molecular structure of the left-handed supra-molecular helix of eukaryotic polyribosomes

Nat Commun. 2014 Nov 7;5:5294. doi: 10.1038/ncomms6294.

Abstract

During protein synthesis, several ribosomes bind to a single messenger RNA (mRNA) forming large macromolecular assemblies called polyribosomes. Here we report the detailed molecular structure of a 100 MDa eukaryotic poly-ribosome complex derived from cryo electron tomography, sub-tomogram averaging and pseudo-atomic modelling by crystal structure fitting. The structure allowed the visualization of the three functional parts of the polysome assembly, the central core region that forms a rather compact left-handed supra-molecular helix, and the more open regions that harbour the initiation and termination sites at either ends. The helical region forms a continuous mRNA channel where the mRNA strand bridges neighbouring exit and entry sites of the ribosomes and prevents mRNA looping between ribosomes. This structure provides unprecedented insights into protein- and RNA-mediated inter-ribosome contacts that involve conserved sites through 40S subunits and long protruding RNA expansion segments, suggesting a role in stabilizing the overall polyribosomal assembly.

MeSH terms

  • Cryoelectron Microscopy
  • Eukaryotic Cells*
  • Molecular Conformation*
  • Plasmids
  • Polyribosomes / chemistry*
  • RNA, Messenger / chemistry
  • RNA, Ribosomal / chemistry*
  • Triticum

Substances

  • RNA, Messenger
  • RNA, Ribosomal

Associated data

  • PDB/4V3P