Initiation factor eIF2γ promotes eIF2-GTP-Met-tRNAi(Met) ternary complex binding to the 40S ribosome

Nat Struct Mol Biol. 2011 Oct 16;18(11):1227-34. doi: 10.1038/nsmb.2133.

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

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Archaeal Proteins / chemistry
  • Archaeal Proteins / genetics
  • Archaeal Proteins / metabolism
  • Cysteine / genetics
  • Eukaryotic Initiation Factor-2 / chemistry
  • Eukaryotic Initiation Factor-2 / genetics
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Guanosine Triphosphate / chemistry
  • Guanosine Triphosphate / metabolism*
  • Hydroxyl Radical / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • Peptide Elongation Factor Tu / chemistry
  • Peptide Elongation Factor Tu / genetics
  • Peptide Elongation Factor Tu / metabolism
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA, Ribosomal, 18S / chemistry
  • RNA, Ribosomal, 18S / metabolism
  • RNA, Transfer, Met / chemistry
  • RNA, Transfer, Met / genetics
  • RNA, Transfer, Met / metabolism*
  • Ribosome Subunits, Small, Eukaryotic / chemistry
  • Ribosome Subunits, Small, Eukaryotic / genetics
  • Ribosome Subunits, Small, Eukaryotic / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • Archaeal Proteins
  • Eukaryotic Initiation Factor-2
  • Met-tRNA(i)(Met)
  • RNA, Ribosomal, 18S
  • RNA, Transfer, Met
  • Saccharomyces cerevisiae Proteins
  • Hydroxyl Radical
  • Guanosine Triphosphate
  • Peptide Elongation Factor Tu
  • Cysteine