6r7l

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Ribosome-bound SecYEG translocon in a nanodisc

Structural highlights

6r7l is a 3 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:Electron Microscopy, Resolution 6Å
Experimental data:Check to display Experimental Data
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

SECE_ECOLI Essential subunit of the protein translocation channel SecYEG. Clamps together the 2 halves of SecY. May contact the channel plug during translocation. Overexpression of some hybrid proteins has been thought to jam the protein secretion apparatus resulting in cell death; while this may be true it also results in FtsH-mediated degradation of SecY.[1]

Publication Abstract from PubMed

The Sec translocon provides the lipid bilayer entry for ribosome-bound nascent chains and thus facilitates membrane protein biogenesis. Despite the appreciated role of the native environment in the translocon:ribosome assembly, structural information on the complex in the lipid membrane is scarce. Here, we present a cryo-electron microscopy-based structure of bacterial translocon SecYEG in lipid nanodiscs and elucidate an early intermediate state upon insertion of the FtsQ anchor domain. Insertion of the short nascent chain causes initial displacements within the lateral gate of the translocon, where alpha-helices 2b, 7, and 8 tilt within the membrane core to "unzip" the gate at the cytoplasmic side. Molecular dynamics simulations demonstrate that the conformational change is reversed in the absence of the ribosome, and suggest that the accessory alpha-helices of SecE subunit modulate the lateral gate conformation. Site-specific cross-linking validates that the FtsQ nascent chain passes the lateral gate upon insertion. The structure and the biochemical data suggest that the partially inserted nascent chain remains highly flexible until it acquires the transmembrane topology.

Partially inserted nascent chain unzips the lateral gate of the Sec translocon.,Kater L, Frieg B, Berninghausen O, Gohlke H, Beckmann R, Kedrov A EMBO Rep. 2019 Aug 5:e48191. doi: 10.15252/embr.201948191. PMID:31379073[2]

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

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See Also

References

  1. Froderberg L, Houben EN, Baars L, Luirink J, de Gier JW. Targeting and translocation of two lipoproteins in Escherichia coli via the SRP/Sec/YidC pathway. J Biol Chem. 2004 Jul 23;279(30):31026-32. Epub 2004 May 12. PMID:15140892 doi:10.1074/jbc.M403229200
  2. Kater L, Frieg B, Berninghausen O, Gohlke H, Beckmann R, Kedrov A. Partially inserted nascent chain unzips the lateral gate of the Sec translocon. EMBO Rep. 2019 Aug 5:e48191. doi: 10.15252/embr.201948191. PMID:31379073 doi:http://dx.doi.org/10.15252/embr.201948191

Contents


6r7l, resolution 6.00Å

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