Question

Explain in words what the ubiquitination reactions are and how they function. What are the ubiquitination enzymes, where are they used in the pathway and what are their function? Explain how proteins starting with an acidic amino acid are recognized for ubiquitination (no structures needed).

Answer 1

Ubiquitination reaction is a kind of chemical reaction which primarily occurs during the post translational modifications. It is a reversible reaction that allows the binding of ubiquitin molecule to target protein molecule.

The covalent attachment or addition of ubiquitin molecule to cellular proteins commonly occurs during post translational machinery.

Ubiquitin is a small protein molecule containing 76 amino acids that binds to other proteins. When the ubiquitin dependent proteolytic machinery identifies a destabilizing amino acid at the N-terminus of protein, a covalent ubiquitin molecule is added on the N-terminus or the nearest lysine. A series of ubiquitin molecules are added, leading to the production of multi-ubiquitinated, branced protein. The attachment of ubiquitin occurs via a series of ATP dependent enzymatic reactions.

The ubiquitinational reaction is responsible for the degradation of short lived cellular proteins. In addition, it regulates the proteins at cellular level. Polyubiquitination reactions primarily triggers the degradation of target proteins in proteosome. It guides the degradation of cellular proteins via proteasomal activity.