scholarly journals Subunit cooperation in the Get1/2 receptor promotes tail-anchored membrane protein insertion

2021 ◽  
Vol 220 (11) ◽  
Author(s):  
Un Seng Chio ◽  
Yumeng Liu ◽  
SangYoon Chung ◽  
Woo Jun Shim ◽  
Sowmya Chandrasekar ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Eukaryotic Cells ◽  
Protein Insertion ◽  
Protein Biogenesis ◽  
Cytosolic Domains ◽  
Membrane Protein Insertion ◽  
The Individual ◽  
Molecular Recognition Features

The guided entry of tail-anchored protein (GET) pathway, in which the Get3 ATPase delivers an essential class of tail-anchored membrane proteins (TAs) to the Get1/2 receptor at the endoplasmic reticulum, provides a conserved mechanism for TA biogenesis in eukaryotic cells. The membrane-associated events of this pathway remain poorly understood. Here we show that complex assembly between the cytosolic domains (CDs) of Get1 and Get2 strongly enhances the affinity of the individual subunits for Get3•TA, thus enabling efficient capture of the targeting complex. In addition to the known role of Get1CD in remodeling Get3 conformation, two molecular recognition features (MoRFs) in Get2CD induce Get3 opening, and both subunits are required for optimal TA release from Get3. Mutation of the MoRFs attenuates TA insertion into the ER in vivo. Our results demonstrate extensive cooperation between the Get1/2 receptor subunits in the capture and remodeling of the targeting complex, and emphasize the role of MoRFs in receptor function during membrane protein biogenesis.

scholarly journals The architecture of EMC reveals a path for membrane protein insertion

2020 ◽  
Author(s):  
John P. O’Donnell ◽  
Ben P. Phillips ◽  
Yuichi Yagita ◽  
Szymon Juszkiewicz ◽  
Armin Wagner ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Transmembrane Domain ◽  
Integral Membrane Proteins ◽  
Membrane Insertion ◽  
Protein Insertion ◽  
Chaperone Function ◽  
Eukaryotic Genes ◽  
Biochemical Assays ◽  
Protein Biogenesis ◽  
Membrane Protein Insertion

AbstractApproximately 25% of eukaryotic genes code for integral membrane proteins that are assembled at the endoplasmic reticulum. An abundant and widely conserved multi-protein complex termed EMC has been implicated in membrane protein biogenesis, but its mechanism of action is poorly understood. Here, we define the composition and architecture of human EMC using biochemical assays, crystallography of individual subunits, site-specific photocrosslinking, and cryo-EM reconstruction. Our results show that EMC’s cytosolic domain contains a large, moderately hydrophobic vestibule that binds a substrate’s transmembrane domain (TMD). The cytosolic vestibule leads into a lumenally-sealed, lipid-exposed intramembrane groove large enough to accommodate a single substrate TMD. A gap between the cytosolic vestibule and intramembrane groove provides a path for substrate egress from EMC. These findings suggest how EMC facilitates energy-independent membrane insertion of TMDs, explain why only short lumenal domains are translocated by EMC, and constrain models of EMC’s proposed chaperone function.

scholarly journals The architecture of EMC reveals a path for membrane protein insertion

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
John P O'Donnell ◽  
Ben P Phillips ◽  
Yuichi Yagita ◽  
Szymon Juszkiewicz ◽  
Armin Wagner ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Transmembrane Domain ◽  
Integral Membrane Proteins ◽  
Membrane Insertion ◽  
Protein Insertion ◽  
Chaperone Function ◽  
Eukaryotic Genes ◽  
Biochemical Assays ◽  
Protein Biogenesis ◽  
Membrane Protein Insertion

Approximately 25% of eukaryotic genes code for integral membrane proteins that are assembled at the endoplasmic reticulum. An abundant and widely conserved multi-protein complex termed EMC has been implicated in membrane protein biogenesis, but its mechanism of action is poorly understood. Here, we define the composition and architecture of human EMC using biochemical assays, crystallography of individual subunits, site-specific photocrosslinking, and cryo-EM reconstruction. Our results suggest that EMC’s cytosolic domain contains a large, moderately hydrophobic vestibule that can bind a substrate’s transmembrane domain (TMD). The cytosolic vestibule leads into a lumenally-sealed, lipid-exposed intramembrane groove large enough to accommodate a single substrate TMD. A gap between the cytosolic vestibule and intramembrane groove provides a potential path for substrate egress from EMC. These findings suggest how EMC facilitates energy-independent membrane insertion of TMDs, explain why only short lumenal domains are translocated by EMC, and constrain models of EMC’s proposed chaperone function.

scholarly journals The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria

2018 ◽  
Vol 29 (20) ◽  
pp. 2386-2396 ◽  
Author(s):  
Braulio Vargas Möller-Hergt ◽  
Andreas Carlström ◽  
Katharina Stephan ◽  
Axel Imhof ◽  
Martin Ott
Keyword(s):  
Membrane Protein ◽  
Mitochondrial Gene ◽  
Ribosomal Subunit ◽  
Mitochondrial Translation ◽  
Protein Insertion ◽  
Mitochondrial Ribosomes ◽  
Protein Biogenesis ◽  
Membrane Bound ◽  
Highly Hydrophobic ◽  
Soluble C

Mitochondrial gene expression in Saccharomyces cerevisiae is responsible for the production of highly hydrophobic subunits of the oxidative phosphorylation system. Membrane insertion occurs cotranslationally on membrane-bound mitochondrial ribosomes. Here, by employing a systematic mass spectrometry–based approach, we discovered the previously uncharacterized membrane protein Mrx15 that interacts via a soluble C-terminal domain with the large ribosomal subunit. Mrx15 contacts mitochondrial translation products during their synthesis and plays, together with the ribosome receptor Mba1, an overlapping role in cotranslational protein insertion. Taken together, our data reveal how these ribosome receptors organize membrane protein biogenesis in mitochondria.

Sign in / Sign up

Export Citation Format

Share Document