Recently, I wrote an article on Mad Cow Disease. In the article I briefly described prions. However, one reader mentioned it would be great to get more information about these rather unique proteins (Thanks for the idea Lily :-). A prion is a proteinaceous infectious particle. This simply means that a protein can cause a particular disease and it can be given to another individual and they can then get the same disease. This term prion was coined by Dr. Stanley Prusiner.
Prion diseases have been described in a number of mammals and in man. Kuru, Creutzfeldt-Jakob disease, and Gerstmann-Straussler-Scheinker disease are the prion diseases that cause illness in humans. All three diseases cause damage to the person's brain and always lead to DEATH :-( . HOWEVER, PLEASE REMEMBER PRION DISEASES ARE VERY RARE!
Now that I have your attention. What is a prion again? A prion is a protein that can cause disease. NO virus, bacteria, fungus, or parasite causes the diseases mentioned above. How does this protein cause disease? The prion protein called PrP (Prion Protein) is produced in all our brains; however, it does NOT cause disease unless it is mutated or over-produced.
Researchers have shown that when the PrP is mutated at certain places in the protein its shape changes. The normal PrP, which does not cause disease, has an alpha helical shape (Sort of like a Slinky that has been stretched out.). Biochemists use the term conformation when talking about protien shape. To see what these protein conformations look like go to The Hypertext Biology Textbook. When mutated the PrP has a beta-pleated sheet shape. Fold up a sheet of paper lengthwise several times and then look at the end of the paper while still folded. That is sort of what it looks like. Once this mutant PrP gets into another person it makes contact with normal PrP. The mutant PrP causes the normal PrP to change in conformation from the alpha helical to the beta-pleated sheet. This beta-pleated sheet -- PrP -- is, for reasons not yet known, lethal to the brain cells and causes holes in the brain (Spongiform Encephalopathy = Sponge-like appearance of the brain).
Are prions a new form of life? No. They are simply one of our own proteins that has gone awry and has the ability to cause normal PrP to also go awry. Sort of like when you hang out with the wrong crowd. The wrong crowd can cause you to mess up rather than your good influence making you act better.
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