A protein degradation “machine” within the cell that can digest a variety of proteins into short polypeptides and amino acids. The proteasome is itself made up of proteins. It requires ATP to work. It is hollow and has openings at both ends to allow entry of the protein to be digested.
A human cell contains about 30,000 proteasomes. These barrel-formed structures can break down practically all proteins to 7-9-amino-acid-long peptides. The active surface of the proteasome is within the barrel where it is shielded from the rest of the cell. The only way in to the active surface is via the “lock”, which recognises proteins tagged with ubiquitin, denatures these proteins and admits them to the barrel for disassembly once the ubiquitin label has been removed. The peptides formed are released from the other end of the proteasome.
Proteasomes digest mainly endogenous proteins, those synthesized within the cell, as opposed to extracellular proteins such as the proteins in blood plasma. The digestion of protein removes excess enzymes and transcription factors and supplies amino acids for new protein synthesis.
- Protease inhibitor
Norvir), and they are used primarily in HIV/AIDS treatment. They are taken as part of a multi-drug cocktail and have been shown to be capable of significantly reducing the level of HIV virus in the blood. Side effects associated with protease inhibitors include lipodystrophy syndrome, in which the face, arms, and legs become thin due […]
One of the three nutrients used as energy sources (calories) by the body. Proteins are essential components of the muscle, skin, and bones. Proteins and carbohydrates each provide 4 calories of energy per gram, whereas fats provide 9 calories per gram.
- Protein C
A vitamin K’dependent protein in plasma that enters into the cascade of biochemical events leading to the formation of blood clots.
- Protein C deficiency
Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease and excess platelets with recurrent thrombophlebitis (inflammation of the vein that occurs when a clot forms). The clot can break loose and travel through […]
- Protein kinase A
An enzyme system that is activated by cyclic adenosine monophosphate (cAMP) and that catalyzes the activity of intracellular proteins. There are two isozymes of protein kinase A, type I and type II. Also known as cAMP-dependent protein kinase and cyclic AMP-dependent protein kinase.