Structure
Volume 22, Issue 6, 10 June 2014, Pages 923-930
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Short Article
Translation Initiation Factor eIF3b Contains a Nine-Bladed β-Propeller and Interacts with the 40S Ribosomal Subunit

https://doi.org/10.1016/j.str.2014.03.010Get rights and content
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Highlights

  • The WD40 domain of eIF3b folds into a nine-bladed β-propeller

  • eIF3b binds to 40S ribosomes in proximity to the mRNA entry channel

  • eIF3b stably associates with ribosomal protein S9e

  • Binding of eIF3b to rpS9e depends on the C-terminal tail of eIF3b

Summary

The multisubunit eukaryotic translation initiation factor 3, among which the subunit b (eIF3b) is a major scaffold protein, plays essential roles in protein synthesis. Here, we report the crystal structure of the WD40 domain of Chaetomium thermophilum eIF3b, revealing a nine-bladed β-propeller fold. Sequence analysis indicates that this propeller architecture is common to all eIF3b orthologs. Revisiting the cryoelectron microscopy (cryo-EM) map of the 43S preinitiation complex suggests an interaction of the eIF3b with the 40S ribosomal subunit involving the ribosomal protein S9e and the 18S rRNA. This model is strongly supported by the direct binding of eIF3b to 40S ribosomes and to the isolated ribosomal protein rpS9e in vitro.

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