Question

explain the importance of protein degradation, and outline the essential pathway for cytosolic protein degradation.

Answer 1

Ans. Impotance of protein degradation:-

1. It is responsible for the formation of the new protein molecules as the building blocks are released by the protein degradation. So new proteins are formed from the amino acids which are released by the previously protein degradation.

2. It is beast for cell regulation. Because degraded proteins acts as the regulatory proteins or as 5he transcriptional factors.

3. They also respond to external stimulli by protein degradation.

4. They are responsible for the intracellular enzyme activity.

5. Protein degradation help in the degradation of faulty enzyme or the protein which is harmful for the cell and hence keep the cell out of rea h from proteotoxicity.

6. It help in the degradation of the older and the damaged proteins.

Pathways for the cytosolic protein degradation:- In eukaryotic cell , it is operated by the biquitin proteasome pathways.

It is for the selective protein degradation. It uses the ubiquitin which is a protein of 75 amino acid polypeptide chian . This is highly conserved in all the plant and animal cell. The ubiquitin protein targets the cytosolic as well as the nucleic protein that to be degraded or cell want to proteolysed.

First of all ubiquitin is phosphorylated by the hydrolysis of ATP.

The protein that to be degraded , the phosphorylated ubiqutin get attached to it by the amino group of side chain of the lysine residue. Now a large number of the ubiquitin molecule get attached to the ubiquitin to form a multiubiqutinated chain structure. This polyubiquinated protein is recogenised by the proteasome. Proteasome is also a multisubunit complex and it will degrade the protein. The ubiquitin is released intact in this process and used in the next degradation process.