The proteasome destroys proteins that the cell marks with a ubiquitin chain. A ring of six AAA+ ATPases grips the marked protein, pulls it straight, and feeds it into a barrel. Three catalytic sites inside the barrel cut the chain into short peptides. A lid subunit strips the ubiquitin tag off in the same cycle.
- Where
- Cytosol and nucleus of all eukaryotes. Archaea and some bacteria have a simpler 20S core.
- Power
- ATP hydrolysis by six AAA+ subunits, in a set order around the ring
6
Catalytic sites per core
1