HECT <p>The name HECT comes from 'Homologous to the E6-AP Carboxyl Terminus' [<cite idref="PUB00004858"/>]. Proteins containing this domain at the C terminus includeubiquitin-protein ligase, which regulates ubiquitination of CDC25. Ubiquitin-protein ligase accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester, and then directly transfers the ubiquitin to targeted substrates. A cysteine residue is required for ubiquitin-thiolester formation. Human thyroid receptor interacting protein 12, which also contains this domain, is a component of an ATP-dependent multisubunit protein that interacts with the ligand binding domain of the thyroid hormone receptor. It could be an E3 ubiquitin-protein ligase. Human ubiquitin-protein ligase E3A interacts with the E6 protein of the cancer-associated <taxon tax_id="333760">Human papillomavirus type 16</taxon> and <taxon tax_id="333761">Human papillomavirus type 18</taxon>. The E6/E6-AP complex binds to and targets the P53 tumour-suppressor protein for ubiquitin-mediated proteolysis.</p>