EMD-15880

Subtomogram averaging
6.7 Å
EMD-15880 Deposition: 27/09/2022
Map released: 07/12/2022
Last modified: 15/02/2023
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-15880

Subtomogram Average of Soluble and ER Membrane-Associated Ribosomes in the Rotated Hibernating State

EMD-15880

Subtomogram averaging
6.7 Å
EMD-15880 Deposition: 27/09/2022
Map released: 07/12/2022
Last modified: 15/02/2023
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Homo sapiens
Sample: ER membrane-associated ribosomes
Raw data: EMPIAR-11751

Deposition Authors: Gemmer M , Forster FG
Visualization of translation and protein biogenesis at the ER membrane.
PUBMED: 36697828
DOI: doi:10.1038/s41586-022-05638-5
ISSN: 1476-4687
ASTM: NATUAS
Abstract:
The dynamic ribosome-translocon complex, which resides at the endoplasmic reticulum (ER) membrane, produces a major fraction of the human proteome1,2. It governs the synthesis, translocation, membrane insertion, N-glycosylation, folding and disulfide-bond formation of nascent proteins. Although individual components of this machinery have been studied at high resolution in isolation3-7, insights into their interplay in the native membrane remain limited. Here we use cryo-electron tomography, extensive classification and molecular modelling to capture snapshots of mRNA translation and protein maturation at the ER membrane at molecular resolution. We identify a highly abundant classical pre-translocation intermediate with eukaryotic elongation factor 1a (eEF1a) in an extended conformation, suggesting that eEF1a may remain associated with the ribosome after GTP hydrolysis during proofreading. At the ER membrane, distinct polysomes bind to different ER translocons specialized in the synthesis of proteins with signal peptides or multipass transmembrane proteins with the translocon-associated protein complex (TRAP) present in both. The near-complete atomic model of the most abundant ER translocon variant comprising the protein-conducting channel SEC61, TRAP and the oligosaccharyltransferase complex A (OSTA) reveals specific interactions of TRAP with other translocon components. We observe stoichiometric and sub-stoichiometric cofactors associated with OSTA, which are likely to include protein isomerases. In sum, we visualize ER-bound polysomes with their coordinated downstream machinery.