Prions and Protein Folding

Prions are an unusual class of proteins that can transmit disease independently of nucleic acids. Diseases caused by prions include bovine spongiform encephalopathy (mad cow disease), scrapie in sheep, and certain neuropathologies in humans.

The protein believed to be responsible for transmitting the disease is called prion-related-protein, or PrP. Prp is present in many animals, including humans, in a non-pathological form called PrPc (prion-related protein cellular). In this form, it mainly has the conformation shown in Figure 6.27. Under certain circumstances, PrPc can change conformation to the sheet-rich structure shown in Figure 6.27, forming PrPsc (prion related protein scrapie). It is the PrPsc form that wreaks havoc with the nervous systems of infected individuals. Even more remarkable is the fact that ingesting PrPsc can induce conversion of PrPc to PrPsc. How the conversion is catalyzed is unknown, but it strongly suggests that PrPc is an especially stable "off pathway" folding.

See also: Dyanics of Protein Folding, Globular Proteins

INTERNET LINK: Prion Diseases