Multiple roles for the C-terminal domain of eIF5 in translation initiation complex assembly and GTPase activation

EMBO J. 2001 May 1;20(9):2326-37. doi: 10.1093/emboj/20.9.2326.

Abstract

eIF5 stimulates the GTPase activity of eIF2 bound to Met-tRNA(i)(Met), and its C-terminal domain (eIF5-CTD) bridges interaction between eIF2 and eIF3/eIF1 in a multifactor complex containing Met-tRNA(i)(Met). The tif5-7A mutation in eIF5-CTD, which destabilizes the multifactor complex in vivo, reduced the binding of Met-tRNA(i)(Met) and mRNA to 40S subunits in vitro. Interestingly, eIF5-CTD bound simultaneously to the eIF4G subunit of the cap-binding complex and the NIP1 subunit of eIF3. These interactions may enhance association of eIF4G with eIF3 to promote mRNA binding to the ribosome. In vivo, tif5-7A eliminated eIF5 as a stable component of the pre-initiation complex and led to accumulation of 48S complexes containing eIF2; thus, conversion of 48S to 80S complexes is the rate-limiting defect in this mutant. We propose that eIF5-CTD stimulates binding of Met-tRNA(i)(Met) and mRNA to 40S subunits through interactions with eIF2, eIF3 and eIF4G; however, its most important function is to anchor eIF5 to other components of the 48S complex in a manner required to couple GTP hydrolysis to AUG recognition during the scanning phase of initiation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Codon, Initiator / metabolism
  • Eukaryotic Initiation Factor-2 / metabolism
  • Eukaryotic Initiation Factor-3
  • Eukaryotic Initiation Factor-4G
  • Eukaryotic Initiation Factor-5
  • Fungal Proteins / metabolism
  • GTP Phosphohydrolases / metabolism*
  • Guanosine Triphosphate / metabolism
  • Macromolecular Substances
  • Mutation
  • Nuclear Proteins / metabolism
  • Peptide Initiation Factors / genetics
  • Peptide Initiation Factors / metabolism*
  • Poly A / metabolism
  • Prokaryotic Initiation Factor-3
  • Protein Binding / physiology
  • Protein Biosynthesis / physiology*
  • Protein Structure, Tertiary / physiology
  • RNA, Messenger / metabolism
  • RNA, Transfer, Met / metabolism
  • Ribosomes / metabolism
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins*

Substances

  • Codon, Initiator
  • Eukaryotic Initiation Factor-2
  • Eukaryotic Initiation Factor-3
  • Eukaryotic Initiation Factor-4G
  • Eukaryotic Initiation Factor-5
  • Fungal Proteins
  • Macromolecular Substances
  • Met-tRNA(i)(Met)
  • NIP1 protein, S cerevisiae
  • Nuclear Proteins
  • Peptide Initiation Factors
  • Prokaryotic Initiation Factor-3
  • RNA, Messenger
  • RNA, Transfer, Met
  • Saccharomyces cerevisiae Proteins
  • Poly A
  • Guanosine Triphosphate
  • GTP Phosphohydrolases