Phosphorylation and Ubiquitination?
What are they?…
A: Protein phosphorylation is a control mechanism that regulates most aspects of cell life. It involves the adding of a phosphate to a protein by a protein kinase or removal of a phosphate by a protein phosphatase, which activates or deactivates (switches on or off) many enzymes and other proteins, causing or preventing the mechanisms of diseases such as cancer and diabetes. Abnormal protein phosphorylation is a cause or consequence of cancer, diabetes and inflammatory disease, while defects in genes that encode protein kinases and phosphatases underlie a number of inherited disorders. Cyclosporin, the immunosuppressant drug widely used in organ transplantation, is a protein phosphatase inhibitor, while protein kinases have become the pharmaceutical industry's most important drug targets. Seventeen protein kinase inhibitors have been approved for clinical use as anti-cancer agents, including Gleevec, the drug that has transformed a previously fatal form of leukaemia into a manageable disease. (Gleevec was developed at Novartis by Nick Lydon, a former PhD student of the University of Dundee.)
Q: What is protein ubiquitination?
A: Protein ubiquitination was discovered in the late 1970s as a mechanism for marking proteins for destruction by the proteasome, but we now know it has many other functions and that it regulates almost all aspects of cell life. Ubiquitin is a small regulatory protein found in almost all tissues, and one of its key functions is recycling or degrading of unneeded proteins by binding covalently to the proteins and labelling them for destruction. As well as administering the “kiss of death” in proteins, ubiquitination also plays a key role in the control of the cell cycle, gene transcription and immunity. Abnormalities in this process are a cause of cancer as well as chronic inflammatory and auto-immune diseases.