Biology: What´s Ubiquitin and Ubiquitination?

Ubiquitin and ubiquitination are commonly used to understand ubiquitin. Ubiquitin is a regulatory protein that plays an important role in the regulation of eukaryotic cells. The word ubiquitin comes from the Latin ubiquitous. It was first isolated from the thymus by Goldstein in 1975 and was later discovered in all tissues and organs of eukaryotic cells. This protein has a molecular weight of 5 kDa and consists of 76 amino acids and is highly conserved in all eukaryotes 1.

Ubiquitin ligase (also known as E3 ubiquitin ligase) is a protein that already carries ubiquitin, recognizes a protein substrate, and recruits E2 path that aids or directly catalyzes the transfer of ubiquitin from E2 to a protein substrate . In protein - bound enzymes. . The ubiquitin protein is bound to lysine on the target protein by an isopeptide bond. The E3 ligase interacts with the target protein and the E2 enzyme, thus conferring E2 substrate specificity. Typically, E3 ubiquitinates the substrate with a ubiquitin chain bound by Lys 48 and targets a substrate that is destroyed by the proteasome. However, many other types of linkages are possible, and it alters the activity, interaction or localization of proteins. Ubiquitination of the E3 ligase regulates various regions such as cell trafficking, DNA repair and signal transduction, and is very important in cell biology. The human genome encodes over 600 putative E3 ligases and gives the substrate a great diversity

Schematic of RING 1 B regulation by self-ubiquitination and exogenous ligase ubiquitination. RING 1 B is a target for the ubiquitination of E 6 - AP and / or other E 3 ligase and results in a Lys 48 based ubiquitin chain targeting RING 1 B due to proteasome degradation. Self ubiquitination of RING 1 B results in the formation of mixed and multi-branched ubiquitin chains based on Lys 6 -, Lys 27 - and Lys 48 activated as a ligase for histone H 2 A. The balance between these two ubiquitination is regulated in several ways. (I) Since the ubiquitination activation and degradation forms target the same lysine residues in RING1 B, the two modifications are mutually exclusive. (Ii) PRCl subunit BMI1 inhibits both types of ubiquitination. (Iii) DUB USP 7 reverses ubiquitination of RING 1 B by itself and E 6 - AP mediated, thereby restoring it to its native state, presumably shifting the balance between ubiquitinated forms.

Ubiquitination of E 3 ligase: self-regulation of the ubiquitin system by proteolysis and nonproteolytic mechanism