The human translation initiation multi-factor complex promotes methionyl-tRNA i binding to the 40S ribosomal subunit

Masaaki Sokabe, Christopher S. Fraser, John W B Hershey

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

The delivery of Met-tRNAi to the 40S ribosomal subunit is thought to occur by way of a ternary complex (TC) comprising eIF2, GTP and Met-tRNAi. We have generated from purified human proteins a stable multifactor complex (MFC) comprising eIF1, eIF2, eIF3 and eIF5, similar to the MFC reported in yeast and plants. A human MFC free of the ribosome also is detected in HeLa cells and rabbit reticulocytes, indicating that it exists in vivo. In vitro, the MFC-GTP binds Met-tRNAi and delivers the tRNA to the ribosome at the same rate as the TC. However, MFC-GDP shows a greatly reduced affinity to Met-tRNAi compared to that for eIF2-GDP, suggesting that MFC components may play a role in the release of eIF2-GDP from the ribosome following AUG recognition. Since an MFC-Met-tRNAi complex is detected in cell lysates, it may be responsible for Met-tRNAi-40S ribosome binding in vivo, possibly together with the TC. However, the MFC protein components also bind individually to 40S ribosomes, creating the possibility that Met-tRNAi might bind directly to such 40S-factor complexes. Thus, three distinct pathways for Met-tRNAi delivery to the 40S ribosomal subunit are identified, but which one predominates in vivo remains to be elucidated.

Original languageEnglish (US)
Pages (from-to)905-913
Number of pages9
JournalNucleic Acids Research
Volume40
Issue number2
DOIs
StatePublished - Jan 2012

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Eukaryotic Small Ribosome Subunits
Peptide Initiation Factors
Transfer RNA
Ribosomes
Guanosine Triphosphate
Reticulocytes
HeLa Cells
Proteins
Yeasts
Rabbits

ASJC Scopus subject areas

  • Genetics

Cite this

The human translation initiation multi-factor complex promotes methionyl-tRNA i binding to the 40S ribosomal subunit. / Sokabe, Masaaki; Fraser, Christopher S.; Hershey, John W B.

In: Nucleic Acids Research, Vol. 40, No. 2, 01.2012, p. 905-913.

Research output: Contribution to journalArticle

Sokabe, Masaaki ; Fraser, Christopher S. ; Hershey, John W B. / The human translation initiation multi-factor complex promotes methionyl-tRNA i binding to the 40S ribosomal subunit. In: Nucleic Acids Research. 2012 ; Vol. 40, No. 2. pp. 905-913.
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