polyubiquitination

Ubiquitination refers to the process by which ubiquitin (a class of low molecular weight proteins) molecules classify proteins in cells under a series of special enzymes, select target protein molecules, and specifically modify target proteins. These special enzymes include ubiquitin-activating enzymes, binding enzymes, ligases and degrading enzymes. Ubiquitination plays an important role in the localization, metabolism, function, regulation and degradation of proteins. At the same time, it is also involved in the regulation of cell cycle, proliferation, apoptosis, differentiation, metastasis, gene expression, transcriptional regulation, signal transmission, damage repair, inflammatory immunity and almost all life activities. Ubiquitination is closely related to the pathogenesis of diseases such as cancer and cardiovascular disease.
Specific process of ubiquitination: ubiquitination involves a series of reactions involving ubiquitin-activating enzyme E1, ubiquitin-binding enzyme E2 and ubiquitin ligase E3. First, in the case of ATP-energy, enzyme E1 adheres to the tail of ubiquitin The ubiquitin is activated on the Cys residue, and then E1 transfers the activated ubiquitin molecule to the E2 enzyme. Subsequently, the E2 enzyme and some different E3 enzymes recognize the target protein and ubiquitinate. The target protein can be monoubiquitinated and polyubiquitinated according to the relative ratio of E3 to the target protein. The shape of the E3 enzyme is like a clip. The left domain of the enzyme in the gap between the target protein and the left domain of the enzyme determines the specific recognition of the target protein, and the right domain localizes the E2 enzyme to transfer the ubiquitin molecule. The result of protein ubiquitination is that the labeled protein is broken down by proteases into smaller polypeptides, amino acids, and ubiquitin that can be reused.