EMC1-dependent stabilization drives membrane penetration of a partially destabilized non-enveloped virus. ER membrane protein complex is required for the insertions of late-synthesized transmembrane helices of Rh1 in Drosophila photoreceptors.
Proteomic analysis identifies membrane proteins dependent on the ER membrane protein complex. A network of chaperones prevents and detects failures in membrane protein lipid bilayer integration. Biosynthesis of ionotropic acetylcholine receptors requires the evolutionarily conserved ER membrane complex. Complexity in targeting membrane proteins. Identification of oxa1 homologs operating in the eukaryotic endoplasmic reticulum. Oxa1 superfamily: new members found in the ER. The ER membrane protein complex is a transmembrane domain insertase. EMC is required to initiate accurate membrane protein topogenesis. The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins. The EMC structure reveals notable evolutionary conservation with the prokaryotic insertases 4, 5, suggests that eukaryotic TMH insertion involves a similar mechanism, and provides a framework for detailed understanding of membrane insertion for numerous eukaryotic integral membrane proteins and tail-anchored proteins.
Mutational studies demonstrated that the flexibility of Emc4 and the hydrophilicity of the client pocket are required for EMC function. The transmembrane domain of Emc4 tilts away from the main transmembrane region of EMC and is partially mobile. We identified a five-TMH fold centred around Emc3 that resembles the prokaryotic YidC insertase and that delineates a largely hydrophilic client protein pocket.
MULTIPASS PROTEIN PLUS
We found that the Saccharomyces cerevisiae EMC contains eight subunits (Emc1–6, Emc7 and Emc10), has a large lumenal region and a smaller cytosolic region, and has a transmembrane region formed by Emc4, Emc5 and Emc6 plus the transmembrane domains of Emc1 and Emc3. Here we report the first, to our knowledge, cryo-electron microscopy structure of the eukaryotic EMC. How EMC accomplishes this feat has been unclear. The endoplasmic reticulum (ER) membrane complex (EMC) cooperates with the Sec61 translocon to co-translationally insert a transmembrane helix (TMH) of many multi-pass integral membrane proteins into the ER membrane, and it is also responsible for inserting the TMH of some tail-anchored proteins 1, 2, 3.
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