A useful toolbox for the detection of SCF E3 ligase activity

Since its discovery about 50 years ago, the ubiquitin-proteasome system (UPS) has not stopped to surprise us for its level of sophistication and complexity in achieving substrate-specific protein degradation (Vierstra, 2009). At the heart of this system lies the concerted activity of three major classes of enzymes: ubiquitin activators (E1), ubiquitin conjugators (E2), and ubiquitin ligases (or E3). E3s, together with selected E2s, are responsible for promoting the formation of a ubiquitin chain on a specific protein substrate. Once this step is completed, in most cases, the ubiquitinated protein will be released and can be recognized by the proteasome, which in turn will remove the ubiquitin chain and degrade the substrate in three- to six-aminoacid–long peptides and then to single amino acids (Vierstra, 2009).