Newly synthesized proteins are targeted to the SecY protein-conducting channel for translocation across the membrane; here, cryo-electron microscopy structures of inactive and active ribosome–channel complexes are presented, revealing that ribosome binding does not result in major structural changes to transmembrane regions of the channel, and that stable channel opening requires loop insertion of the translocating nascent chain.
- Eunyong Park
- Jean-François Ménétret
- Christopher W. Akey