Accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro, in the presence or in the absence of BRCA1-BARD1 E3 ubiquitin-protein ligase complex, catalyzes the synthesis of 'Lys-48'-linked polyubiquitin chains. Does not transfer ubiquitin directly to but elongates monoubiquitinated substrate protein. Mediates the selective degradation of short-lived and abnormal proteins, such as the endoplasmic reticulum-associated degradation (ERAD) of misfolded lumenal proteins. Ubiquitinates huntingtin. May mediate foam cell formation by the suppression of apoptosis of lipid-bearing macrophages through ubiquitination and subsequence degradation of p53/TP53. Proposed to be involved in ubiquitination and proteolytic processing of NF-kappa-B; in vitro supports ubiquitination of NFKB1. In case of infection by cytomegaloviruses may be involved in the US11-dependent degradation of MHC class I heavy chains following their export from the ER to the cytosol. In case of viral infections may be involved in the HPV E7 protein- dependent degradation of RB1. Interacts with RNF138/NARF. Interacts with BRCA1. By aggregated low-density lipoprotein. Expressed in all tissues tested, including spleen, thymus, prostate, testis, ovary, small intestine, colon, peripheral blood leukocytes, T-lymphocytes, monocytes, granulocytes and bone marrow mononuclear cells. Highly expressed in brain, with highest levels found in cortex and striatum and at lower levels in cerebellum and brainstem. Belongs to the ubiquitin-conjugating enzyme family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Protein type: Ubiquitin ligase; Ubiquitin conjugating system; EC 18.104.22.168; Ligase
Cellular Component: cytoplasm
Molecular Function: protein binding; acid-amino acid ligase activity; ubiquitin protein ligase binding; ubiquitin-protein ligase activity; ATP binding
Biological Process: ubiquitin-dependent protein catabolic process; regulation of proteasomal ubiquitin-dependent protein catabolic process
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.