lubiquitinazione

Ubiquitination is a post-translational modification process in which a small protein called ubiquitin is attached to a target protein. This modification is a highly conserved and versatile cellular mechanism involved in a wide range of biological processes. The attachment of ubiquitin is catalyzed by a cascade of enzymes, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s). E3 ligases are crucial as they confer substrate specificity to the ubiquitination process.

Ubiquitination can lead to various cellular outcomes depending on the type of ubiquitin chain formed and the target protein. The most well-known outcome is the targeting of proteins for degradation by the proteasome, a multi-subunit protease complex. This is often mediated by the formation of K48-linked polyubiquitin chains. However, ubiquitin can also be conjugated as single molecules (monoubiquitination) or form different types of polyubiquitin chains linked through other lysine residues on ubiquitin (e.g., K63-linked chains). These alternative forms of ubiquitination can regulate protein localization, activity, DNA repair, signal transduction, and protein trafficking without necessarily leading to degradation. The dynamic nature of ubiquitination, involving both the addition and removal of ubiquitin by deubiquitinating enzymes (DUBs), allows for precise control of cellular processes. Dysregulation of ubiquitination has been implicated in various diseases, including cancer, neurodegenerative disorders, and immune system dysfunctions.