Skip to main content
. Author manuscript; available in PMC: 2024 Mar 15.
Published in final edited form as: Semin Cell Dev Biol. 2023 Sep 19;156:107–120. doi: 10.1016/j.semcdb.2023.08.002

Fig. 1. The Ubiquitin Proteasome System.

Fig. 1.

Ub is initially conjugated to an E1 ubiquitin activating enzyme, in an ATP-dependent reaction, and is then transferred to an E2 Ub conjugation enzyme. E3 ligases bring an Ub-E2 complex in proximity with a target protein, to which Ub gets transferred. Additional ubiquitins are conjugated through the same processes to create a polyUb chain. This chain targets proteins to the 26 S proteasome, where deubiquitinases (DUBs) remove Ub before ATP-dependent proteasomal degradation. Other DUBs specifically break down Ub chains to replenish the cellular pool of free ubiquitin, which is then accessible for E1 enzymes. Created with BioRender.com.