Summary information and primary citation

PDB-id
2wwb; SNAP-derived features in text and JSON formats; DNAproDB
Class
ribosome
Method
cryo-EM (6.48 Å)
Summary
cryo-EM structure of the mammalian sec61 complex bound to the actively translating wheat germ 80s ribosome
Reference
Becker T, Bhushan S, Jarasch A, Armache JP, Funes S, Jossinet F, Gumbart J, Mielke T, Berninghausen O, Schulten K, Westhof E, Gilmore R, Mandon E, Beckmann R (2009): "Structure of Monomeric Yeast and Mammalian Sec61 Complexes Interacting with the Translating Ribosome." Science, 326, 1369. doi: 10.1126/SCIENCE.1178535.
Abstract
The trimeric Sec61/SecY complex is a protein-conducting channel (PCC) for secretory and membrane proteins. Although Sec complexes can form oligomers, it has been suggested that a single copy may serve as an active PCC. We determined subnanometer-resolution cryo-electron microscopy structures of eukaryotic ribosome-Sec61 complexes. In combination with biochemical data, we found that in both idle and active states, the Sec complex is not oligomeric and interacts mainly via two cytoplasmic loops with the universal ribosomal adaptor site. In the active state, the ribosomal tunnel and a central pore of the monomeric PCC were occupied by the nascent chain, contacting loop 6 of the Sec complex. This provides a structural basis for the activity of a solitary Sec complex in cotranslational protein translocation.

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