ubiquinated

Ubiquitinated refers to the state of a protein or other molecule into which ubiquitin, a small regulatory protein, has been covalently attached. This post-translational modification is dynamic and can influence a protein’s stability, activity, location, or interactions with other molecules.

The attachment of ubiquitin is accomplished through a cascade of enzymes: an E1 activating enzyme, an E2 conjugating enzyme, and an E3 ligase that provides substrate specificity. Ubiquitin can be added as a single molecule (monoubiquitination) or as chains (polyubiquitination). Polyubiquitin chains can be formed through linkages at different ubiquitin lysine residues, with the most well-known being K48-linked chains that often signal degradation by the proteasome, and other linkages (such as K63) that participate in signaling, DNA repair, endocytosis, and trafficking. The modification is reversible through deubiquitinases, which remove ubiquitin.

The functional consequences of ubiquitination are diverse. It commonly marks proteins for degradation by the 26S proteasome, but it also regulates enzymatic activity, protein–protein interactions, subcellular localization, and responses to stress or signaling events. Monoubiquitination can alter activity or trafficking without triggering degradation, while different polyubiquitin chain types can direct distinct cellular outcomes.

Dysregulation of ubiquitination pathways is linked to numerous diseases, including cancer, neurodegenerative disorders, and immune or inflammatory conditions. Because of its central role in protein quality control and signaling, ubiquitination remains a major focus for therapeutic research, with strategies targeting E3 ligases, deubiquitinases, or the proteasome itself.