6wb9 | pdb_00006wb9
Structure of the S. cerevisiae ER membrane complex
Structural highlights
Function[EMC5_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). [EMC2_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). [EMC6_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). [EMC1_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). [SOP4_YEAST] Involved in the export of PMA1, possibly through the monitoring or assisting of PMA1 folding and acquisition of competence to enter vesicles.[1] [2] [EMC10_YEAST] Non essential component of the endoplasmic reticulum (ER) membrane protein complex (EMC) involved in ER-associated degradation (ERAD) and proper assembly of multi-pass transmembrane proteins (Probable). EMC acts in yeast as an ER-mitochondria tether that interacts with outer membrane protein TOM5 of TOM (translocase of the mitochondrial outer membrane) complex (Probable).[3] [EMC3_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). [EMC4_YEAST] The EMC seems to be required for efficient folding of proteins in the endoplasmic reticulum (ER). Publication Abstract from PubMedThe 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(1-3). How EMC accomplishes this feat has been unclear. Here we report the first, to our knowledge, cryo-electron microscopy structure of the eukaryotic EMC. 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. We identified a five-TMH fold centred around Emc3 that resembles the prokaryotic YidC insertase and that delineates a largely hydrophilic client protein pocket. The transmembrane domain of Emc4 tilts away from the main transmembrane region of EMC and is partially mobile. Mutational studies demonstrated that the flexibility of Emc4 and the hydrophilicity of the client pocket are required for EMC function. 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. Structure of the ER membrane complex, a transmembrane-domain insertase.,Bai L, You Q, Feng X, Kovach A, Li H Nature. 2020 Jun 3. pii: 10.1038/s41586-020-2389-3. doi:, 10.1038/s41586-020-2389-3. PMID:32494008[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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