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This animation gives a very simplified view of how prions cause fatal neurodegenerative diseases of the brain in man and animals.
1. The prion protein PrP is a normal constituent of many cell types in the body, notably nerve cells (neurons) in the brain. The name prion (pronounced pree-on) is derived from "proteinaceous infectious particle." In its normal conformation, the prion protein (termed PrPc) is innocuous. Its function in the body is still unknown. However, PrPc can undergo a conformational change, adopting a harmful, disease-causing shape termed PrP-scrapie, or PrPSc. Scrapie is a transmissible spongiform encephalopathy of sheep identified in Iceland as early as the 18th century.
The conversion of the PrPc-form to the PrPSc-form occurs at an extremely low frequency. The process may be compared to the transformation of Robert Louis Stevenson's novel character, Dr Jekyll, to Mr Hyde - the same entity but in two manifestations - a "kind", innocuous one and a "vicious", lethal one. PrPSc has unusual properties. It is stable to treatments at high temperatures (100°C), UV-light, and ionizing irradiation enzymes that normally destroy proteins and nucleic acids and some detergents. Such treatments would destroy all known viruses.
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