Cryo-EM structures of the endoplasmic reticulum membrane complex.
1Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China.
The FEBS Journal
|February 25, 2021
Summary
The endoplasmic reticulum membrane complex (EMC) inserts less hydrophobic transmembrane helices into membranes. Recent cryo-electron microscopy studies reveal its conserved architecture and evolutionary links to prokaryotic insertases.
Area of Science:
- Membrane protein biogenesis
- Protein translocation
- Cellular machinery
Background:
- Transmembrane α-helices are typically hydrophobic and insert via the Sec61 translocon.
- Less hydrophobic, amphipathic transmembrane helices require specialized machinery for membrane insertion.
- The endoplasmic reticulum membrane complex (EMC) is a distinct multi-subunit chaperone involved in inserting such helices.
Purpose of the Study:
- To investigate the structure and function of the eukaryotic EMC.
- To understand the mechanism of amphipathic transmembrane helix insertion.
- To explore the evolutionary relationship between eukaryotic and prokaryotic insertases.
Main Methods:
- Cryo-electron microscopy (cryo-EM) of eukaryotic EMC complexes.
- Comparative structural analysis across species (yeast to human).
- Analysis of evolutionary links to prokaryotic protein insertion machinery.
Main Results:
- Revealed remarkable architectural conservation of the EMC from yeast to humans.
- Established a consensus view of the substrate transmembrane helix-binding pocket within the EMC.
- Identified an evolutionary link between the eukaryotic EMC and prokaryotic insertases for tail-anchored proteins.
Conclusions:
- The conserved structure of the EMC provides a framework for understanding its mechanism.
- EMC plays a crucial role in the biogenesis of specific membrane proteins.
- Structural insights facilitate future mechanistic studies of membrane protein insertion.
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