Prions are misfolded proteins that are associated with several fatal neurodegenerative diseases in animals and humans.
It is not known what causes the normal prion protein to misfold; the abnormal 3D structure is suspected to confer infectious properties. The word prion derives from ‘proteinaceous infectious particle’. Prions composed of the prion protein (PrP) are hypothesized as the cause of transmissible spongiform encephalopathies(TSEs), including scrapie in sheep and bovine spongiform encephalopathy (BSE) in cattle—known popularly as "mad cow disease".
