5ABB: Visualization Of A Polytopic Membrane Protein During Secy-mediated Membrane Insertion

The biogenesis of polytopic membrane proteins occurs co-translationally on ribosomes that are tightly bound to a membrane-embedded protein-conducting channel: the Sec-complex. The path that is followed by nascent proteins inside the ribosome and the Sec-complex is relatively well established; however, it is not clear what the fate of the N-terminal transmembrane domains (TMDs) of polytopic membrane proteins is when the C-terminal TMDs domains are not yet synthesized. Here, we present the sub-nanometer cryo-electron microscopy structure of an in vivo generated ribosome-SecY complex that carries a membrane insertion intermediate of proteorhodopsin (PR). The structure reveals a pre-opened Sec-complex and the first two TMDs of PR already outside the SecY complex directly in front of its proposed lateral gate. Thus, our structure is in agreement with positioning of N-terminal TMDs at the periphery of SecY, and in addition, it provides clues for the molecular mechanism underlying membrane protein topogenesis.
PDB ID: 5ABBDownload
MMDB ID: 131950
PDB Deposition Date: 2015/8/5
Updated in MMDB: 2017/09
Experimental Method:
electron microscopy
Resolution: 8  Å
Source Organism:
Similar Structures:
Biological Unit for 5ABB: trimeric; determined by author
Molecular Components in 5ABB
Label Count Molecule
Proteins (3 molecules)
Protein Translocase Subunit Secy
Molecule annotation
Protein Translocase Subunit Sece
Molecule annotation
Green-light Absorbing Proteorhodopsin
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB