Ubikvitináció

Ubikvitináció is a post-translational modification process in which a small protein called ubiquitin is attached to a target protein. This process is highly conserved and occurs in all eukaryotic cells. Ubiquitin is a 76-amino acid protein that is found in nearly all eukaryotic organisms. The attachment of ubiquitin to a target protein is catalyzed by a series of enzymes, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s).

The process of ubiquitination typically involves three steps. First, ubiquitin is activated by an E1 enzyme. Second, the activated ubiquitin is transferred to an E2 enzyme. Third, the E2 enzyme, in conjunction with an E3 ligase, transfers the ubiquitin to a lysine residue on the target protein. The E3 ligase is responsible for recognizing the specific target protein. Ubiquitin can be attached as a single molecule (monoubiquitination) or as a chain of ubiquitin molecules (polyubiquitination). The type and length of the ubiquitin chain can determine the fate of the target protein.

Ubiquitination plays a crucial role in a wide range of cellular processes, including protein degradation, DNA repair, signal transduction, and protein trafficking. The most well-known function of ubiquitination is its role in targeting proteins for degradation by the proteasome. Polyubiquitinated proteins are recognized by the proteasome and degraded into small peptides. However, ubiquitination also has non-degradative functions, such as regulating protein activity, localization, and interactions. Dysregulation of ubiquitination pathways has been implicated in various diseases, including cancer, neurodegenerative disorders, and immune diseases, making it a significant area of research.