Following processing by an ubiquitin
C-terminal hydrolase (UCH), Ub is conjugated to a specific substrate
as a chain by the ubiquitin-activating (E1), -conjugating (E2), and
-ligating (E3) enzymes. The chain targets the substrate to the 26S
proteasome, which comprises one 20S proteolytic complex and two 19S
regulatory complexes. (from C.A. Ross, C.M. Pickart, Trends Cell Biol, 14:703–11, 2004) |