E3 Ligases 33 Products

There are estimated to be >700 E3 ligases forming several classes of enzyme; N-end rule ubiquitin E3 ligases, Homology to E6AP C-Terminus (HECT) domain E3s, Really Interesting New Gene (RING) domain E3s, U-Box containing E3s, Inhibitor of Apoptosis (IAP) E3s, and Cullin-RING E3 ligases (CRLs). The classes of E3 ligases are continually expanding. HECT E3 ligases form a thioester intermediate with the C-terminus of activated ubiquitin via a catalytic cysteine residue on the E3. In this case, ubiquitin is transferred from an E2 via the E3 to a substrate protein lysine side chain. RING and U-Box E3 ligases do not possess a catalytic cysteine residue and bring the E2-ubiquitin complex and substrate into close proximity to mediate the transfer of the ubiquitin directly from the E2 to the substrate.