Copyright ©2013 Baishideng Publishing Group Co.
World J Clin Oncol. Aug 10, 2013; 4(3): 58-69
Published online Aug 10, 2013. doi: 10.5306/wjco.v4.i3.58
Figure 1
Figure 1 Ubiquitin molecules are covalently conjugated to targeted proteins in a three-step enzymatic cascade. First, an E1 ubiquitin-activating enzyme activates ubiquitin in an adenosine triphosphate (ATP)-dependent manner. Activated ubiquitin is then transferred to the E1 enzyme, followed by the transfer of ubiquitin to an E2 ubiquitin-conjugating enzyme. Finally, an E3 ubiquitin protein ligase recognizes the target proteins and mediates the conjugation of one or more ubiquitin molecules to a lysine residue on the targeted proteins. Really interesting new gene (RING) E3 ubiquitin ligases mediate the direct transfer of ubiquitin from E2 to the targeted substrate whereas Homologous to the E6-associated protein (E6-AP) carboxyl terminus (HECT) E3 ubiquitin ligases first interact with the cognate E2, followed by linkage with ubiquitin and subsequent transfer of ubiquitin to the targeted substrate. AMP: Adenosine monophosphate.