Proteasome

Proteasome

The Proteasome is a protein complex found in all eukaryotes and archaea, and in some bacteria. In eukaryotes, they are located in the nucleus and the cytoplasm. The main function of the proteasome is to degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds.

Structure

The proteasome is a large protein complex that is composed of two main subunits: the 20S core particle (CP) and the 19S regulatory particle (RP). The 20S CP is a barrel-shaped structure that is made up of four stacked rings. Each ring is composed of seven different proteins. The 19S RP is attached to one or both ends of the 20S CP and is responsible for recognizing, unfolding, and translocating target proteins into the 20S CP.

Function

The main function of the proteasome is to degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Proteins are targeted for degradation by the proteasome through a two-step process. First, the protein is tagged with a small protein called ubiquitin. This tagging process is known as ubiquitination. Once a protein has been ubiquitinated, it is recognized by the 19S RP of the proteasome, which unfolds the protein and translocates it into the 20S CP for degradation.

Clinical significance

Proteasomes have been implicated in a number of human diseases, including cancer, neurodegenerative diseases, and autoimmune diseases. In cancer, proteasomes play a role in regulating cell growth and division. In neurodegenerative diseases, the failure of proteasomes to degrade misfolded or damaged proteins can lead to the accumulation of toxic protein aggregates. In autoimmune diseases, proteasomes are involved in the processing of antigens for presentation to the immune system.

See also

• Ubiquitin-proteasome system
• Proteasome inhibitor
• Proteolysis

References

Proteasome Resources
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