Lukas Bischoff / Stephan Wickles / Otto Berninghausen / Eli O van der Sluis / Roland Beckmann /
PubMed Abstract
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 ...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.
EMDB-2446: Visualization of a polytopic membrane protein egressing from the SecY complex - Electron cryo-microscopy of an tightly coupled RNC-SecY complex PDB-5abb: Visualization of a polytopic membrane protein during SecY-mediated membrane insertion Method: EM (single particle) / Resolution: 7.28 Å
Source
escherichia coli (E. coli)
Keywords
TRANSLATION / RIBOSOME / MEMBRANE PROTEIN / TRANSLOCON
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