TRF-Ubiquitin Mix (100X) (2000 reactions)

Ubiquitin is a highly conserved protein that plays a major role in the ubiquitination pathway, which is conserved from yeast to mammals. Ubiquitination, the conjugation of ubiquitin to other proteins through a covalent bond between its C-terminal glycine and the epsilon-amino group of lysine residues or the alpha-amino group of an N- terminal methionine onto proteins is essential for many cellular processes primarily linked to protein degradation. This process involves three steps with specific groups of enzymes in an ATP depended manner, which are activation with ubiquitin-activating enzymes (E1s), conjugation with ubiquitin-conjugating enzymes (E2s) and ligation with ubiquitin ligases (E3s). Protein function: Ubiquitin: Exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair, Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation, Lys-29-linked is involved in lysosomal degradation, Lys-33-linked is involved in kinase modification, Lys-48-linked is involved in protein degradation via the proteasome, Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling. [The UniProt Consortium]