Ubiquitin and Ubiquitin-like Modifiers

Degradation of a protein via the Ubiquitin Proteasome pathway involves two discrete and successive steps: tagging of the substrate protein by the covalent attachment of multiple Ubiquitin molecules (conjugation), and the subsequent degradation of the tagged protein by the 26S proteasome. Ubiquitin is conjugated to substrate proteins via an enzymatic cascade involving E1 (ubiquitin activating), E2 (ubiquitin conjugating) and E3 (ubiquitin ligating) enzymes. This classical function is associated with housekeeping roles, including the regulation of protein turnover, and antigenic-peptide generation. More recently, it has become evident that protein modification by Ubiquitin has non-degradative functions, including involvement in DNA repair and histone modification, vesicular trafficking pathways and endocytosis, and viral budding.

Although Ubiquitin is the most studied, there is a growing family of Ubiquitin-like proteins (UBLs) that modify cellular targets in a pathway that is parallel to but distinct from that of Ubiquitin. These alternative modifiers include: SUMO, NEDD8, ISG15, APG8, APG12, FAT10, UFM1, URM1, FUB1, and Hub1. Proteins conjugated to UBLs are typically not targeted for degradation by the proteasome, but rather function in diverse regulatory activities including transcription, DNA repair, signal transduction, and autophagy.

Sino Biological lists the classification tree of Ubiquitin and Ubiquitin-like Modifiers, click to see all the related molecules/targets and research reagents of them.