APC11 (anaphase-promoting complex subunit 11) is a member of the E3 enzyme family. This protein contains a RING-H2 domain and has a molecular weight of approximately 9.8 kD. The APC11 protein is distributed diffusely in the cytoplasm and is located in the nucleus with discrete accumulation in granular structures. The APC11 protein is a probable catalytic unit in the APC complex. The APC11 protein functions with other members of the APC complex as a multisubunit cell cycle ubiquitin ligase, and a regulator of sister chromatid separation by degrading securins. In addition, this protein functions in ubiquitin-dependent cyclin catabolism, metaphase/anaphase transition, and spindle elongation. The APC11 protein comprises one subunit of the anaphase promoting complex including APC1-8, and other probable complex proteins APC9-11, Cdc26, Mnd2, Swm1. The APC complex is inactivated by protein kinase A and is activated by CDC20 and Cdh1. In addition to the APC complex proteins, APC11 has been shown to interact with Ubc4.