Synergistic activation of eIF4A by eIF4B and eIF4G

Nucleic Acids Res. 2011 Apr;39(7):2678-89. doi: 10.1093/nar/gkq1206. Epub 2010 Nov 26.


eIF4A is a key component in eukaryotic translation initiation; however, it has not been clear how auxiliary factors like eIF4B and eIF4G stimulate eIF4A and how this contributes to the initiation process. Based on results from isothermal titration calorimetry, we propose a two-site model for eIF4A binding to an 83.5 kDa eIF4G fragment (eIF4G-MC), with a high- and a low-affinity site, having binding constants KD of ∼50 and ∼1000 nM, respectively. Small angle X-ray scattering analysis shows that the eIF4G-MC fragment adopts an elongated, well-defined structure with a maximum dimension of 220 Å, able to span the width of the 40S ribosomal subunit. We establish a stable eIF4A-eIF4B complex requiring RNA, nucleotide and the eIF4G-MC fragment, using an in vitro RNA pull-down assay. The eIF4G-MC fragment does not stably associate with the eIF4A-eIF4B-RNA-nucleotide complex but acts catalytically in its formation. Furthermore, we demonstrate that eIF4B and eIF4G-MC act synergistically in stimulating the ATPase activity of eIF4A.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Eukaryotic Initiation Factor-4A / chemistry
  • Eukaryotic Initiation Factor-4A / metabolism*
  • Eukaryotic Initiation Factor-4G / chemistry
  • Eukaryotic Initiation Factor-4G / metabolism*
  • Eukaryotic Initiation Factors / metabolism*
  • Protein Binding
  • Scattering, Small Angle
  • X-Ray Diffraction


  • Eukaryotic Initiation Factor-4G
  • Eukaryotic Initiation Factors
  • eIF-4B
  • Eukaryotic Initiation Factor-4A
  • Adenosine Triphosphatases