PSMB4
Description
The PSMB4 (proteasome 20S subunit beta 4) is a protein-coding gene located on chromosome 1.
PSMB4, also known as Proteasome subunit beta type-4 or 20S proteasome subunit beta-7, is a protein encoded by the PSMB4 gene in humans. It is one of the 17 essential subunits required for the complete assembly of the 20S proteasome complex, responsible for protein degradation. PSMB4, along with other beta subunits, forms two heptameric rings within the proteasome's proteolytic chamber. The proteasome recognizes degradable proteins, including damaged proteins for quality control and regulatory proteins for dynamic cellular processes. A modified proteasome called the immunoproteasome, which includes PSMB4, plays a crucial role in processing peptides presented by MHC class I molecules. PSMB4 belongs to the proteasome B-type family and is encoded by a gene with 7 exons located on chromosome 1q21. The protein is 23 kDa in size and comprises 219 amino acids, with a theoretical pI of 5.47. The proteasome is a multicatalytic proteinase complex with a highly ordered 20S core structure.
PSMB4 is a non-catalytic component of the 20S core proteasome complex, essential for the proteolytic degradation of most intracellular proteins. This complex is involved in various cellular processes by associating with different regulatory particles. When associated with two 19S regulatory particles, it forms the 26S proteasome, participating in the ATP-dependent degradation of ubiquitinated proteins. This process is crucial for maintaining protein homeostasis by removing misfolded or damaged proteins and those no longer required. PSMB4 can also associate with PA200 or PA28, facilitating ubiquitin-independent protein degradation. This type of proteolysis is vital for various pathways, including spermatogenesis (20S-PA200 complex) and MHC class I antigen presentation (20S-PA28 complex). The SMAD1/OAZ1/PSMB4 complex is involved in the degradation of the CREBBP/EP300 repressor SNIP1.
PSMB4 is also known as HN3, HsN3, PRAAS3, PROS-26, PROS26.
