Abstract
In contrast to prokaryotic elongation factor EF-Tu, which delivers aminoacyl-tRNAs to the ribosomal A-site, eukaryotic initiation factor eIF2 binds methionyl initiator transfer RNA (Met-tRNA(i)(Met)) to the P-site of the 40S ribosomal subunit. The results of directed hydroxyl radical probing experiments to map binding of Saccharomyces cerevisiae eIF2 on the ribosome and on Met-tRNA(i)(Met) revealed that eIF2γ primarily contacts the acceptor stem of Met-tRNA(i)(Met) and identified a key binding interface between domain III of eIF2γ and 18S rRNA helix h44 on the 40S subunit. Whereas the analogous domain III of EF-Tu contacts the T stem of tRNAs, biochemical analyses demonstrated that eIF2γ domain III is important for ribosome, not Met-tRNA(i)(Met). Thus, despite their structural similarity, eIF2 and EF-Tu bind tRNAs in substantially different manners, and we propose that the tRNA-binding domain III of EF-Tu has acquired a new ribosome-binding function in eIF2γ.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, N.I.H., Intramural
MeSH terms
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Archaeal Proteins / chemistry
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Archaeal Proteins / genetics
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Archaeal Proteins / metabolism
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Cysteine / genetics
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Eukaryotic Initiation Factor-2 / chemistry
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Eukaryotic Initiation Factor-2 / genetics
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Eukaryotic Initiation Factor-2 / metabolism*
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Guanosine Triphosphate / chemistry
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Guanosine Triphosphate / metabolism*
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Hydroxyl Radical / metabolism
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Models, Molecular
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Molecular Sequence Data
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Nucleic Acid Conformation
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Peptide Elongation Factor Tu / chemistry
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Peptide Elongation Factor Tu / genetics
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Peptide Elongation Factor Tu / metabolism
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Protein Binding
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Protein Structure, Tertiary
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RNA, Ribosomal, 18S / chemistry
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RNA, Ribosomal, 18S / metabolism
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RNA, Transfer, Met / chemistry
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RNA, Transfer, Met / genetics
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RNA, Transfer, Met / metabolism*
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Ribosome Subunits, Small, Eukaryotic / chemistry
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Ribosome Subunits, Small, Eukaryotic / genetics
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Ribosome Subunits, Small, Eukaryotic / metabolism*
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
Substances
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Archaeal Proteins
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Eukaryotic Initiation Factor-2
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Met-tRNA(i)(Met)
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RNA, Ribosomal, 18S
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RNA, Transfer, Met
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Saccharomyces cerevisiae Proteins
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Hydroxyl Radical
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Guanosine Triphosphate
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Peptide Elongation Factor Tu
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Cysteine