Characterization of eIF3k: A newly discovered subunit of mammalian translation initiation factor eIF3

Greg L. Mayeur, Christopher S. Fraser, Franck Peiretti, Karen L. Block, John W B Hershey

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Mammalian translation initiation factor 3 (eIF3) is a multisubunit complex containing at least 12 subunits with an apparent aggregate mass of ≈ 700 kDa. eIF3 binds to the 40S ribosomal subunit, promotes the binding of methionyl-tRNAi and mRNA, and interacts with several other initiation factors to form the 40S initiation complex. Human cDNAs encoding 11 of the 12 subunits have been isolated previously; here we report the cloning and characterization of a twelfth subunit, a 28-kDa protein named eIF3k. Evidence that eIF3k is present in the eIF3 complex was obtained. A monoclonal anti-eIF3a (p170) Ig coimmunoprecipitates eIF3k with the eIF3 complex. Affinity purification of histidine-tagged eIF3k from transiently transfected COS cells copurifies other eIF3 subunits. eIF3k colocalizes with eIF3 on 40S ribosomal subunits. eIF3k coexpressed with five other 'core' eIF3 subunits in baculovirus-infected insect cells, forms a stable, immunoprecipitatable, complex with the 'core'. eIF3k interacts directly with eIF3c, eIF3g and eIF3j by glutathione S-transferase pull-down assays. Sequences homologous with eIF3k are found in the genomes of Caenorhabitis elegans, Arabidopsis thaliana and Drosophila melanogaster, and a homologous protein has been reported to be present in wheat eIF3. Its ubiquitous expression in human tissues, yet its apparent absence in Saccharomyces cerevisiae and Schizosaccharomyces pombe, suggest a unique regulatory role for eIF3k in higher organisms. The studies of eIF3k complete the characterization of mammalian eIF3 subunits.

Original languageEnglish (US)
Pages (from-to)4133-4139
Number of pages7
JournalEuropean Journal of Biochemistry
Issue number20
StatePublished - Oct 2003


  • eIF3
  • eIF3k
  • Initiation factor
  • Protein synthesis
  • Translation initiation

ASJC Scopus subject areas

  • Biochemistry


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