E6-AP
E6-AP (E6-associated protein) is an E3 (ubiquitin protein ligase) that is involved in the conjugation of ubiquitin to target substrates along with E1 and E2 enzymes. It is a HECT domain E3 containing an active site cysteine which accepts a charged ubiquitin from the ubiquitin-E2 thiolester complex. E6-AP has been linked to a neurodevelopmental disorder, Angelman syndrome. In addition, the oncoprotein E6 of human papillomaviruses (HPV) utilizes E6-AP to target numerous cellular proteins for degradation including the tumor suppressor protein p53.