antigenic substrate E3 ligases in proteasomal degradation Ub:E2s Ag-substrate:E3:E2:Ub Interaction of E3 with substrate and E2-Ub complex Authored: Garapati, P V, 2010-10-29 Edited: Garapati, P V, 2010-10-29 Pubmed12646216 Pubmed16954532 Pubmed19489725 Reactome Database ID Release 43983157 Reactome, http://www.reactome.org ReactomeREACT_75856 Reviewed: Elliott, T, 2011-02-10 Ubiquitin E3 ligases confer specificity to ubiquitination by recognizing target substrates and mediating transfer of ubiquitin from an E2 ubiquitin-conjugating enzyme to substrate (Raymond et al. 2009). E3 ligases includes a large, diverse set of proteins characterized by several defining motifs which include a HECT (homologous to E6-associated C-terminus), RING (Really Interesting New Gene) and U-box domains. The E3 ligases can be multisubunit complexes rather than a single polypeptide. Presently three different kinds of E3 complexes have been described called SCF, APC, and VHL. E3 ligases binds to both substrate and an E2 thioesterified with ubiquitin (E2-Ub).