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A technique for delineating the unfolding requirements for substrate entry into retrotranslocons during endoplasmic reticulum–associated degradation
- Source :
- J Biol Chem
- Publication Year :
- 2019
- Publisher :
- American Society for Biochemistry and Molecular Biology, 2019.
-
Abstract
- The endoplasmic reticulum–associated degradation (ERAD) pathway mediates the endoplasmic reticulum–to–cytosol retrotranslocation of defective proteins through protein complexes called retrotranslocons. Defective proteins usually have complex conformations and topologies, and it is unclear how ERAD can thread these conformationally diverse protein substrates through the retrotranslocons. Here, we investigated the substrate conformation flexibility necessary for transport via retrotranslocons on the ERAD-L, ERAD-M, and HIV-encoded protein Vpu-hijacked ERAD branches. To this end, we appended various ERAD substrates with specific domains whose conformations were tunable in flexibility or tightness by binding to appropriate ligands. With this technique, we could define the capacity of specific retrotranslocons in disentangling very tight, less tight but well-folded, and unstructured conformations. The Hrd1 complex, the retrotranslocon on the ERAD-L branch, permitted the passage of substrates with a proteinase K–resistant tight conformation, whereas the E3 ligase gp78-mediated ERAD-M allowed passage only of nearly completely disordered but not well-folded substrates and thus may have the least unfoldase activity. Vpu-mediated ERAD, containing a potential retrotranslocon, could unfold well-folded substrates for successful retrotranslocation. However, substrate retrotranslocation in Vpu-mediated ERAD was blocked by enhanced conformational tightness of the substrate. On the basis of these findings, we propose a mechanism underlying polypeptide movement through the endoplasmic reticulum membrane. We anticipate that our biochemical system paves the way for identifying the factors necessary for the retrotranslocation of membrane proteins.
- Subjects :
- 0301 basic medicine
Proteasome Endopeptidase Complex
Leupeptins
Ubiquitin-Protein Ligases
Human Immunodeficiency Virus Proteins
macromolecular substances
Endoplasmic-reticulum-associated protein degradation
Endoplasmic Reticulum
Biochemistry
Substrate Specificity
03 medical and health sciences
Humans
Viral Regulatory and Accessory Proteins
Molecular Biology
Er associated degradation
Protein Unfolding
030102 biochemistry & molecular biology
biology
Chemistry
Endoplasmic reticulum
Substrate (chemistry)
Cell Biology
Endoplasmic Reticulum-Associated Degradation
Ubiquitin ligase
Receptors, Autocrine Motility Factor
030104 developmental biology
Membrane
HEK293 Cells
Membrane protein
biology.protein
Biophysics
Trimetrexate
Protein folding
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- J Biol Chem
- Accession number :
- edsair.doi.dedup.....0e17e7f46251f189a27569ce1871b45d