Binds and presumably selects ubiquitin-conjugates for destruction. Displays selectivity for longer polyubiquitin chains. Modulates intestinal fluid secretion. The 26S proteasome is composed of a core protease, known as the 20S proteasome, capped at one or both ends by the 19S regulatory complex (RC). The RC is composed of at least 18 different subunits in two subcomplexes, the base and the lid, which form the portions proximal and distal to the 20S proteolytic core, respectively. Directly interacts with NUB1. Interacts with SQSTM1. Interacts with UBQLN4. Belongs to the proteasome subunit S5A family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Biological Process: positive regulation of ubiquitin-protein ligase activity during mitotic cell cycle; negative regulation of ubiquitin-protein ligase activity during mitotic cell cycle; protein polyubiquitination; viral reproduction; apoptosis; M/G1 transition of mitotic cell cycle; antigen processing and presentation of exogenous peptide antigen via MHC class I, TAP-dependent; DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest; mRNA metabolic process; regulation of apoptosis; antigen processing and presentation of peptide antigen via MHC class I; regulation of ubiquitin-protein ligase activity during mitotic cell cycle; RNA metabolic process; anaphase-promoting complex-dependent proteasomal ubiquitin-dependent protein catabolic process; antigen processing and presentation of exogenous peptide antigen via MHC class I; gene expression; mitotic cell cycle; S phase of mitotic cell cycle; regulation of amino acid metabolic process; cell cycle checkpoint; G1/S transition of mitotic cell cycle
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.