COP9 signalosome
COP9 signalosome is a protein complex with isopeptidase activity. It catalyses the hydrolysis of NEDD8 protein from the cullin subunit of Cullin-RING ubiquitin ligases. Therefore, it is responsible for CRL deneddylation – at the same time, it is able to bind denedyllated cullin-RING complex and retain them in deactivated form. COP9 signalosome thus serves as a sole deactivator of CRLs. The complex was originally identified in plants, and subsequently found in all eukaryotic organisms including human.
Human COP9 signalosome consists of 8 subunits - CSN1, CSN2, CSN3, CSN4, CSN5, CSN6, CSN7, CSN8. All are essential for full function of the complex and mutation in some of them is lethal in mice.
