Related Experiment Videos
Mammalian Sec61 is associated with Sec62 and Sec63
1Universität Göttingen, Zentrum Biochemie und Molekulare Zellbiologie, Biochemie II, Heinrich-Düker-Weg 12, Göttingen 37073, Germany.
The Journal of Biological Chemistry
|May 9, 2000
Summary
Mammalian cells possess ribosome-free Sec61 complexes, involving new Sec62 and Sec63 proteins, for endoplasmic reticulum (ER) protein transport. This suggests a potential post-translational pathway distinct from yeast.
Area of Science:
- Molecular Biology
- Cell Biology
- Protein Trafficking
Background:
- Protein transport across the endoplasmic reticulum (ER) membrane in yeast occurs via co-translational or post-translational pathways.
- Mammalian protein translocation is primarily co-translational, relying on the ribosome-bound Sec61 complex.
- The yeast post-translational pathway involves the Sec61p complex and the Sec62p-Sec63p subcomplex.
Purpose of the Study:
- To investigate the existence and composition of non-ribosomal protein complexes involved in ER membrane transport in mammals.
- To identify mammalian homologs of yeast Sec62p and Sec63p and characterize their association with the Sec61 complex.
Main Methods:
- Primary sequence analysis of newly identified ER membrane proteins.
- Identification and characterization of mammalian Sec61 complexes.
- Comparative analysis with yeast protein transport mechanisms.
Main Results:
- Discovery of ribosome-free mammalian Sec61 complexes associated with two novel ER membrane proteins.
- Sequence homology confirms these proteins as mammalian Sec62 and Sec63, analogous to yeast Sec62p and Sec63p.
- Mammalian ER membranes exhibit abundant Sec61-Sec62-Sec63 complexes, unlike yeast ER membranes.
Conclusions:
- Mammalian cells possess a distinct Sec61-Sec62-Sec63 complex, potentially mediating post-translational protein translocation.
- This complex may represent an alternative or complementary pathway to the predominantly co-translational translocation in mammals.
- The abundance of this complex suggests a significant role in mammalian ER protein transport, possibly compensating for less efficient post-translational activity compared to yeast.