Ubiquitinázás

Ubiquitinázás refers to the process of ubiquitination, a crucial post-translational modification in all eukaryotic cells. It involves the covalent attachment of a small protein called ubiquitin to a target protein. This process is highly regulated and carried out by a cascade of enzymes. First, an activating enzyme (E1) uses ATP to bind ubiquitin. Then, a conjugating enzyme (E2) accepts the activated ubiquitin from E1. Finally, a ligase enzyme (E3) specifically recognizes the target protein and facilitates the transfer of ubiquitin from E2 to the target.

Ubiquitination can occur as a single ubiquitin molecule (monoubiquitination) or as a chain of ubiquitin molecules (polyubiquitination). The type and linkage of ubiquitin chains determine the fate of the target protein. Monoubiquitination and certain types of polyubiquitination often signal for protein trafficking, DNA repair, or changes in protein activity. However, the most well-known function of polyubiquitination, particularly those linked via lysine 48 of ubiquitin, is to mark proteins for degradation by the 26S proteasome.

This degradation pathway, known as the ubiquitin-proteasome system (UPS), plays a vital role in maintaining cellular homeostasis by removing damaged, misfolded, or unneeded proteins. Dysregulation of ubiquitinázás is implicated in a wide range of diseases, including cancer, neurodegenerative disorders, and immune system dysfunction, highlighting its fundamental importance in cellular biology and disease pathogenesis. The reversibility of ubiquitination is also significant, carried out by deubiquitinating enzymes (DUBs) that remove ubiquitin tags, thus allowing for dynamic regulation of protein fate.