Protein degradation; Posttranslational protein modification
Protein modification by the covalent attachment of ubiquitin chains serves as a signal to mark proteins for the degradation by a multicatalytic proteinase complex called the proteasome. Thus the ubiquitin proteasome system (UPS) controls the stability of proteins in a regulated manner affecting multiple essential cellular processes. In addition, dependent on the mode of linkage, ubiquitin regulates protein-protein interaction, endocytosis, replication and the formation of signaling complexes in a proteasome-independent fashion. Beside phosphorylation ubiquitination represents the most important posttranslational regulatory mechanism in biology.
Ubiquitin is a highly conserved 8.5 kDa polypeptide, which was first described in 1974. The discovery that the Ubiquitin proteasome system serves as a general mechanism to target proteins for destruction