InterPro domain: IPR040961

The COP9 (Constitutive photomorphogenesis 9) signalosome (CSN), a large multiprotein complex that resembles the 19S lid of the 26S proteasome, plays a central role in the regulation of the E3-cullin RING ubiquitin ligases (CRLs) [ 1 ]. The catalytic activity of the CSN complex is carried by subunit 5 (CSN5), also known as c-Jun activation domain-binding protein-1 (Jab1) [ 2 ]. This entry is the C-terminal domain found in CSN5 proteins. CSN5, whose two C-terminal helices form an antiparallel hairpin, inserts its final C-terminal helix (helix II) into the central CSN6 framework at the core of the bundle. Deletion of the C-terminal helices has a pronounced effect on CSN integrity [ 2 ].

1. Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1. Proc. Natl. Acad. Sci. U.S.A. 110, 1273-8
2. Crystal structure of the human COP9 signalosome. Nature 512, 161-5