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
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Codon, Initiator / metabolism
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Eukaryotic Initiation Factor-2 / metabolism
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Eukaryotic Initiation Factor-3
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Eukaryotic Initiation Factor-4G
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Eukaryotic Initiation Factor-5
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Fungal Proteins / metabolism
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GTP Phosphohydrolases / metabolism*
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Guanosine Triphosphate / metabolism
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Macromolecular Substances
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Mutation
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Nuclear Proteins / metabolism
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Peptide Initiation Factors / genetics
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Peptide Initiation Factors / metabolism*
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Poly A / metabolism
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Prokaryotic Initiation Factor-3
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Protein Binding / physiology
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Protein Biosynthesis / physiology*
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Protein Structure, Tertiary / physiology
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RNA, Messenger / metabolism
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RNA, Transfer, Met / metabolism
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Ribosomes / metabolism
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Saccharomyces cerevisiae
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Saccharomyces cerevisiae Proteins*
Substances
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Codon, Initiator
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Eukaryotic Initiation Factor-2
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Eukaryotic Initiation Factor-3
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Eukaryotic Initiation Factor-4G
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Eukaryotic Initiation Factor-5
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Fungal Proteins
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Macromolecular Substances
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Met-tRNA(i)(Met)
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NIP1 protein, S cerevisiae
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Nuclear Proteins
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Peptide Initiation Factors
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Prokaryotic Initiation Factor-3
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RNA, Messenger
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RNA, Transfer, Met
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Saccharomyces cerevisiae Proteins
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Poly A
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Guanosine Triphosphate
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GTP Phosphohydrolases