Ring domain E3 ubiquitin ligases (RING E3s) are the most abundant type of ubiquitin ligases. They are characterized by the presence of a zinc-binding domain called RING (Really Interesting New Gene) or by a U-box domain, which adopts the same RING fold but does not contain zinc. The RING and U-box domains are responsible for binding the ubiquitin-charged E2 and mediate a direct transfer of ubiquitin to the substrate. RING E3s can function as monomers, homodimers, or heterodimers. Some are composed of multiple subunits, such as the cullin-RING ligases and the anaphase-promoting complex/cyclosome. (Adapted from PMID:27015313.)
Notes on Group
Note that only the catalytic RING subunit of the multi-subunit cullin-RING ligases and APC/C are included within the RING DOMAIN E3 UBIQUITIN LIGASES group.
