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Publication Abstract from PubMed

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.

Visualization of a polytopic membrane protein during SecY-mediated membrane insertion.,Bischoff L, Wickles S, Berninghausen O, van der Sluis EO, Beckmann R Nat Commun. 2014 Jun 10;5:4103. doi: 10.1038/ncomms5103. PMID:24912953^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.