What is a Prion?

Q: Can anyone explain me what is a prion? Thanks

A: A prion is a nonliving, self-replicating infectious agent made of protein. It can reproduce with the aid of its host's biological machinery, like a virus. "Prion" is short for "proteinaceous infectious particle." The idea of an infectious agent lacking nucleic acids for reproduction was initially met with skepticism when the idea was proposed in the 60s, because such a phenomenon had never been observed before.

While self-replicating nucleic acid-based entities are well-understood, the mechanism of self-replication among prions is still a mystery. Prions found in animals exclusively infect the brain, are fatal and untreatable. Prions have been discovered in fungi, but rather than damaging them, it is theorized that they may play a symbiotic role in the fungi's immune system.

Prions are responsible for the outbreak of Mad Cow Disease in Britain during the early 00s, which led to the destruction of thousands of livestock, and international fear about the possibility of the disease spreading from bovines to humans. The prion protein was not isolated until 1982, when Stanley B. Prusiner discovered it and coined the term.

He was awarded the Nobel Prize in physiology or medicine in 1997 for his discovery. One of the first instances of prion-based disease to be investigated was that of scrapie, a disease occurring among sheep and goats. This disease was known since the 18th century, but it was not until the 60s that scientists began to suspect that scrapie was not a typical disease, self-replicating outside of the usual means of nucleic acids.

Scrapie, like most prion-based diseases, is fatal to the animal it infects, causing horrible symptoms before death. The name of the disease comes from the disturbing behavior of infected sheep, to scrape off their fleece against rocks. The prion also causes an inability to walk, convulsive collapse, and excessive lip-smacking.

more information:
http://dreddyclinic.com/forum/viewtopic.php?t=5475
http://www.wisegeek.com/what-is-a-prion.htm