Figure 1.

The ubiquitination and deubiquitination process. In the upper panel, three distinct biochemical steps are required for substrate (Sub) ubiquitination: activation performed by activating enzymes (E1s), conjugation by conjugating enzymes (E2s), and ligation by ubiquitin ligases (E3s). In the lower panel, there are different ubiquitin (Ub) modifications and a schematic representation of deubiquitination performed by deubiquitinating enzymes (DUBs). The number of members of each type of enzymes in mammals are highlighted in purple.