Send to:

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 2014 Mar 7;289(10):7190-9. doi: 10.1074/jbc.M113.506634. Epub 2014 Jan 17.

Cryo-electron microscopic structure of SecA protein bound to the 70S ribosome.

Author information

  • 1From the Rudolf Virchow Center/DFG Research Center for Experimental Biomedicine, University of Würzburg, Josef Schneider Str. 2, 97078 Würzburg, Germany.


SecA is an ATP-dependent molecular motor pumping secretory and outer membrane proteins across the cytoplasmic membrane in bacteria. SecA associates with the protein-conducting channel, the heterotrimeric SecYEG complex, in a so-called posttranslational manner. A recent study further showed binding of a monomeric state of SecA to the ribosome. However, the true oligomeric state of SecA remains controversial because SecA can also form functional dimers, and high-resolution crystal structures exist for both the monomer and the dimer. Here we present the cryo-electron microscopy structures of Escherichia coli SecA bound to the ribosome. We show that not only a monomeric SecA binds to the ribosome but also that two copies of SecA can be observed that form an elongated dimer. Two copies of SecA completely surround the tunnel exit, providing a unique environment to the nascent polypeptides emerging from the ribosome. We identified the N-terminal helix of SecA required for a stable association with the ribosome. The structures indicate a possible function of the dimeric form of SecA at the ribosome.


70S; Cryo-EM; Electron Microscopy (EM); Protein Secretion; Protein Translocation; Ribosome; Ribosomes; SecA; SecYEG; Single Particle Analysis

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk