The proteasome and the ubiquitin system are key interlinked components involved in protein degradation in animal cells. The proteasome itself is a large, barrel-shaped protein complex and in the cytoplasm plays a crucial role in regulating protein levels and maintaining cellular homeostasis. Additionally, it can be found in the nucleus, where it participates in various nuclear processes, including DNA repair and transcriptional regulation. It consists of a central core particle (CP) formed by four stacked rings, with two outer rings composed of alpha subunits and two inner rings composed of beta subunits. The CP is capped at both ends by regulatory particles (RP), which recognize and unfold ubiquitinated proteins. The proteasome primarily degrades ubiquitinated proteins that have been marked for destruction. It acts by recognizing, unfolding, and hydrolysing ubiquitin-tagged proteins. The ubiquitin-protein conjugates are recognized by the RP, unfolded by ATP-dependent unfoldase enzymes, and transferred into the central catalytic chamber of the CP, where proteins are cleaved into short peptides. Proteins targeted for degradation by the proteasome are covalently tagged with a chain of ubiquitin molecules. Ubiquitin itself is a small protein found in all eukaryotic cells and mainly acts as a molecular tag marking proteins for degradation, although multiple examples of ubiquitylation as a regulatory mechanism have also been identified. Ubiquitin molecules can be covalently attached to lysine residues of target proteins in the form of monoubiquitin or polyubiquitin chains. This process involves the sequential action of three enzymes: E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin ligase). E2 enzymes facilitate the transfer of ubiquitin from E1 to the target protein. They work in conjunction with E3 ligases to recognize and selectively transfer ubiquitin to specific target proteins. There are several E2 enzymes in cells, each with specificity for certain target proteins. E3 ligases provide the substrate specificity in the ubiquitin system by recognizing specific target proteins and transferring ubiquitin to them from the E2, resulting in the formation of a polyubiquitin chain. E3 ligases can be classified into several groups: 1) HECT (Homologous to the E6-AP Carboxyl Terminus) domain-containing E3 ligases, which have a conserved catalytic domain known as the HECT domain. They form an intermediate thioester bond with ubiquitin before transferring it to the target protein; 2) RBR (RING-between-RING) E3 ligases, which possess a unique combination of three domains: a RING1 domain, an in-between-RING (IBR) domain, and a RING2 domain. They also form a thioester intermediate with ubiquitin, like HECT ligases; 3) RING (Really Interesting New Gene) domain containing E3 ligases, which are the largest group of E3 ligases. They interact with both the target protein and an E2 ubiquitin-conjugating enzyme, facilitating the direct transfer of ubiquitin from the E2 to the target protein; 4) U-box E3 ligases, which share structural similarities with RING ligases but lack the characteristic zinc-coordinating residues found in RING domains. Instead, they contain a modified RING domain known as the U-box, which is responsible for their ubiquitin ligase activity; 5) Cullin-RING Ligases (CRLs), which are a family of multi-subunit E3 ligases that consist of a catalytic RING subunit, a scaffold protein (cullin), and an adaptor protein that recruits the target protein. CRLs are involved in the ubiquitination of a wide range of substrates. We provide a wide product catalogue of research reagents for investigating the proteasome and ubiquitin, including BRCA1 antibodies, PGP9.5 antibodies, Ubiquitin antibodies, Ubiquitin ELISA Kits, and BRCA1 ELISA Kits. Explore our full proteasome and ubiquitin product range below and discover more, for less. Alternatively, you can explore our Ubiquitin E3 Enzymes, Proteasome, and Deubiquitination product ranges.