RING finger, H2 subclass, found in anaphase-promoting complex subunit 11 (APC11) and similar proteins
APC11, also known as cyclosome subunit 11, or hepatocellular carcinoma-associated RING finger protein, is a C3H2C3-type RING-H2 protein that facilitates ubiquitin chain formation by recruiting ubiquitin-charged ubiquitin conjugating enzymes (E2) through its RING-H2 domain. APC11 and its partner the cullin-like subunit APC2 form the dynamic catalytic core of the gigantic, multisubunit 1.2-MDa anaphase-promoting complex/cyclosome (APC), also known as the cyclosome, which is a ubiquitin-protein ligase (E3) composed of at least 12 subunits and controls cell division by ubiquitinating cell cycle regulators, such as cyclin B and securin, to drive their timely degradation. APC11 can be inhibited by hydrogen peroxide, which may contributes to the delay in cell cycle progression through mitosis that is characteristic of cells subjected to oxidative stress. APC11 contains a canonical RING-H2-finger domain, which includes one histidine and seven cysteine residues that coordinate two Zn2+ ions. In addition, it contains a third Zn2+-binding site and the third Zn2+ ion is not essential for its ligase activity.