Highly purified ubiquitin free of glycine and buffer salts which can interfere with chemical and in vitro reactions. Ubiquitin is a 76 amino acid, highly conserved nuclear and cytoplasmic eukaryotic protein. It is covalently attached to substrate proteins by enzymes in the Ubiquitin-Proteasome Pathway (UPP). The major role of ubiquitination is to target cellular proteins for the ATP-dependent degradation by the 26S proteasome and proteasome-independent or regulatory events such as protein localization, activity and function. This protein sequence is for A.thaliana (P59263) and is exactly the same for barley, oat, soya bean and other plants.