Functional significance and mechanism of eIF5-promoted GTP hydrolysis in eukaryotic translation initiation

Supratik Das, Umadas Maitra

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Eukaryotic translation initiation factor 5 (eIF5), a monomeric protein of about 49 kDa in mammals and 46 kDa in the yeast Saccharomyces cerevisiae, in conjunction with GTP and other initiation factors plays an essential role in initiation of protein synthesis in eukaryotic cells. Following formation of the 40S initiation complex (40S · eIF3 · mRNA · Met-tRNAf · eIF2 · GTP) at the AUG codon of an mRNA, eIF5 interacts with the 40S initiation complex to promote the hydrolysis of bound GTP Hydrolysis of GTP causes the release of bound initiation factors from the 40S subunit, an event that is essential for the subsequent joining of the 60S ribosomal subunit to the 40S complex to form the functional SOS initiation complex. Detailed characterization of the eIF5-promoted GTP hydrolysis reaction shows that eIF5 functions as a GTPase-activating protein (GAP) in translation initiation. First, eIF5 promotes hydrolysis of GTP only when the nucleotide is bound to eIF2 in the 40S initiation complex. eIF5, by itself, does not hydrolyze either free GTP or GTP bound to the Met-tRNAf · eIF2 · GTP ternary complex in the absence of 40S ribosomal subunits. Second, as with typical GAPs, eIF5 forms a complex with eIF2, the GTP-binding protein. This interaction, which occurs between the lysine-rich N-terminal region of the β subunit of eIF2 and the glutamic acid-rich C-terminal region of eIF5, is essential for eIF5 function both in vitro and in vivo in yeast cells. Finally, like typical GAPs, eIF5 also contains an arginine-finger motif consisting of an invariant arginine residue at its N-terminus that is also essential for its function. This invariant arginine residue is presumably involved in the stabilization of the transition state of the GTP hydrolysis reaction catalyzed by initiation factor eIF2.

Original languageEnglish (US)
Pages (from-to)207-231
Number of pages25
JournalProgress in Nucleic Acid Research and Molecular Biology
Volume70
StatePublished - 2001

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Eukaryotic Initiation Factor-5
Eukaryotic Initiation Factors
Guanosine Triphosphate
Hydrolysis
Peptide Initiation Factors
Arginine
Translational Peptide Chain Initiation
Eukaryotic Large Ribosome Subunits
Yeasts
Eukaryotic Small Ribosome Subunits
GTPase-Activating Proteins
Protein Biosynthesis
Eukaryotic Cells
GTP-Binding Proteins
Codon

ASJC Scopus subject areas

  • Molecular Biology

Cite this

Functional significance and mechanism of eIF5-promoted GTP hydrolysis in eukaryotic translation initiation. / Das, Supratik; Maitra, Umadas.

In: Progress in Nucleic Acid Research and Molecular Biology, Vol. 70, 2001, p. 207-231.

Research output: Contribution to journalArticle

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