The cryo-EM structure of a translation initiation complex from Escherichia coli

Cell. 2005 Jun 3;121(5):703-12. doi: 10.1016/j.cell.2005.03.023.

Abstract

The 70S ribosome and its complement of factors required for initiation of translation in E. coli were purified separately and reassembled in vitro with GDPNP, producing a stable initiation complex (IC) stalled after 70S assembly. We have obtained a cryo-EM reconstruction of the IC showing IF2*GDPNP at the intersubunit cleft of the 70S ribosome. IF2*GDPNP contacts the 30S and 50S subunits as well as fMet-tRNA(fMet). IF2 here adopts a conformation radically different from that seen in the recent crystal structure of IF2. The C-terminal domain of IF2 binds to the single-stranded portion of fMet-tRNA(fMet), thereby forcing the tRNA into a novel orientation at the P site. The GTP binding domain of IF2 binds to the GTPase-associated center of the 50S subunit in a manner similar to EF-G and EF-Tu. Additionally, we present evidence for the localization of IF1, IF3, one C-terminal domain of L7/L12, and the N-terminal domain of IF2 in the initiation complex.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cryoelectron Microscopy
  • Escherichia coli / physiology*
  • Escherichia coli / ultrastructure
  • Euryarchaeota / metabolism
  • Prokaryotic Initiation Factor-2 / metabolism
  • Protein Biosynthesis / physiology*
  • Protein Structure, Tertiary
  • RNA, Transfer / metabolism
  • Ribosomes / metabolism*
  • Ribosomes / ultrastructure

Substances

  • Prokaryotic Initiation Factor-2
  • RNA, Transfer

Associated data

  • PDB/IZ01
  • PDB/IZ03