Ubiquitin and Ubiquitin Chains

Ubiquitin is a small polypeptide that is conjugated via its C-terminus to an ε-amino group of lysine on a target protein; this conjugation is referred to as monoubiquitylation. Subsequently, additional ubiquitin moieties can be conjugated to the initial ubiquitin, utilizing any of seven lysine residues (K6, K11, K27, K29, K33, K48, K63) on the surface of ubiquitin; this ubiquitin chain formation is referred to as polyubiquitylation. Enzymatic conjugation of ubiquitin is performed by a series of enzymes — ubiquitin activating enzyme E1, ubiquitin conjugating enzyme E2, and ubiquitin ligase E3.  Ubiquitylation of proteins is reversible in cells; both mono- and polyubiquitylated chains are cleaved by hydrolysis catalyzed by deubiquitylases (DUBs).

LifeSensors has considerable experience with enzymes at all levels of the ubiquitin pathway, including E1, E2, and E3 enzymes and DUBs. LifeSensors’ extensive knowledge of protein purification has enabled us to produce approximately 30 E2 enzymes, 20 E3 enzymes, and 35 DUBs, with the capability for custom expression available. Further, our extensive panel of assays simplifies the process of confirming enzyme activity and determining the compatibility of E2-E3 pairs and ensures that you can choose an enzyme that will best address specific, critical biological questions that you wish to explore.

LifeSensors has developed a variety of ubiquitin derivatives for your research, including DUB-resistant polyubiquitin chains for binding interaction studies, ubiquitin conjugates for DUB assays and screening (fluorophores and reporter enzymes), selective ubiquitin chains (di-, tri-, and tetra-ubiquitin chains) for DUB specificity and binding assays, and site-specific lysine ubiquitin mutants for E3 ligase and DUB selectivity assays.