Figure 1.

Schematic of the ubiquitination mechanism. Protein ubiquitination is catalyzed by the signaling cascades of ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligase (E3). In the case of ATP energy supply, E1 activates ubiquitin and transmits the activated ubiquitin to E2. Subsequently, the activated ubiquitin molecules are recruited to E3 ligases, E3 ligases connect ubiquitin to the target protein, and the target protein is ubiquitinated to be specifically recognized and degraded by the 26S proteasome. Some of the graphics in this figure was created using ScienceSlides software 2016 edition (VisiScience Inc., Chapel Hill, NC, USA).