Ubiquitin Cascade

Ubiquitin activation: The E1 mediates a nucleophilic attack on the C-terminus of ubiquitin to the α-phosphate of an ATP molecule in a reaction stabilized by Mg++. A second nucleophilic attack of the thiol group of a cysteine of the E1 (catalytic cysteine) to the C-terminus of ubiquitin produces a thiol-ester (thioester) bond. Two E1 enzymes […]


Ubiquitin is the founder member of the Ubl family. It participates in many biological processes, but its most studied effect is its covalent conjugation to other proteins, which targets the modified proteins for proteasome-mediated degradation. Ubiquitin is one of the highest conserved proteins in eukaryotes, however, it is found neither in bacteria nor in archaea.[…..]

Ubiquitin Proteasome System

The ubiquitin proteasome system (UPS) is the major non-lysosomal, intracellular proteolytic system. Its main role is the recycling of cellular components [89-91]. The UPS is also important in the quality control of proteins, control of cell cycle, transcription factor regulation, cell differentiation and immune response. The UPS is strongly regulated by the ubiquitin like protein[…..]