Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1.

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). The catalytic activity of the CSN complex, carried by subunit 5 (CSN5/Jab1), resides in the deneddylation of the CRLs that is the hydrolysis of the cullin-neural precursor cell expressed developmentally downregulated gene 8 (Nedd8)isopeptide bond. Whereas CSN-dependent CSN5 displays isopeptidase activity, it is intrinsically inactive in other physiologically relevant forms.

Structural insight into the Mycobacterium tuberculosis Rv0020c protein and its interaction with the PknB kinase.

The protein Rv0020c from Mycobacterium tuberculosis, also called FhaA, is one of the major substrates of the essential Ser/Thr protein kinase (STPK) PknB. The protein is composed of three domains and is phosphorylated on a unique site in its N terminus. We solved the solution structure of both N- and C-terminal domains and demonstrated that the approximately 300 amino acids of the intermediate domain are not folded.