Ubiquitin ligases (also known as E3 enzymes) are critical enzymatic mediators of the ubiquitin-proteasome system (UPS). They play key roles in regulating protein stability and function by facilitating the transfer of ubiquitin molecules from E2 enzymes to target proteins. The human genome encodes many E3 ubiquitin ligases, estimated to be in the range of 600 to 1,000 or even more, each with distinct substrate specificities and cellular functions. These E3 ligases can be classified into different families based on their structural and functional characteristics. Some well-known E3 ligase families include the RING (Really Interesting New Gene), HECT (Homologous to E6-AP C Terminus), and RBR (RING-Between-RING) families, amongst others. Important E3 ligases include such proteins as the SCF Complex (Skp1-Cullin-F-box), involved in the ubiquitylation and degradation of numerous substrates, including cell cycle regulators and transcription factors. β-TrCP is an F-box protein within this complex that targets substrates for degradation. It plays a critical role in the regulation of the cell cycle by targeting the cyclin-dependent kinase inhibitor p27 for ubiquitylation and degradation, allowing cell cycle progression. MDM2 is an E3 ligase that regulates the tumour suppressor protein p53. It ubiquitylates p53, marking it for degradation by the proteasome. This interaction keeps p53 levels low under normal conditions. However, in response to DNA damage or cellular stress, MDM2 is inhibited, leading to p53 stabilization and activation, which promotes cell cycle arrest or apoptosis, depending on the extent of damage. CHIP (Carboxyl terminus of Hsc70-interacting protein) is an E3 ligase that is involved in the quality control of proteins. It binds to misfolded or damaged proteins and polyubiquitylates them, directing them to the proteasome for degradation. This process helps maintain protein homeostasis and prevents the accumulation of toxic protein aggregates. Parkin is an E3 ligase associated with a specific disease, Parkinson's disease. It plays a critical role in mitochondrial quality control by ubiquitylating damaged or dysfunctional mitochondria, targeting them for removal via mitophagy, a selective form of autophagy. Dysfunction of Parkin is linked to mitochondrial dysfunction and neurodegenerative diseases. SCFFBXO7 (Skp1-Cullin-F-box protein FBXO7) ubiquitylates Parkin, marking it for degradation. This process regulates Parkin levels, which is essential for maintaining mitochondrial homeostasis and preventing excessive mitophagy. The CRL4 (Cullin 4-RING E3 Ligase) complex is involved in DNA repair and replication. DDB2 is one of its substrate receptors that binds to DNA lesions. When DNA damage occurs, CRL4(DDB2) ubiquitylates proteins at the damage site, promoting DNA repair processes. Fbxw7 (F-box/WD repeat-containing protein 7) is an E3 ligase involved in regulating the cell cycle. It targets several cell cycle regulators, including cyclin E, for ubiquitylation and degradation. By doing so, Fbxw7 helps control cell cycle progression and prevents abnormal cell proliferation. Finally, TRIM (Tripartite Motif) proteins constitute a large family of E3 ligases with diverse functions. TRIM25, for instance, plays a role in innate immunity by ubiquitylating the RIG-I protein, which is involved in antiviral responses. This ubiquitylation activates RIG-I, leading to the production of interferons and the antiviral immune response. We provide a wide product range of research tools for studying E3 ubiquitin ligases, including MDM2 antibodies, MURF1 antibodies, and RNF8 antibodies. Explore our full E3 ubiquitin ligases product range below and discover more, for less.