K6 Tetra-Ubiquitin

The array of cellular processes initiated and regulated by ubiquitin has been partially explained by the structural diversity of differently linked ubiquitin chains. In a ubiquitin chain, ubiquitin moieties can be conjugated through one of their lysine residues (K6, K11, K27, K29, K33, K48 and K63) or the N-terminal methionine residue (M1), offering countless possibilities to assemble a specific polymer. Ubiquitin molecules can also be modified by other post-translational modifications, including acetylation and phosphorylation, adding another layer of ubiquitin signal regulation and diversification. K6 linked ubiquitin linkages are found at increased levels in response to UV radiation, indirectly associated with DNA repair, and have been identified on mitochondrial outer membrane (MOM) proteins. This K6 linked tetra-ubiquitin was recombinantly expressed in E. coli, enzymatically conjugated, and purified via liquid chromatography.