Misfolded Prions Induce Normal Protein to Misfold
Prions, disease-causing proteins found in brain cells, have been named the culprit in a variety of disorders, including mad-cow disease, scrapie in sheep, and Creutzfeldt-Jakob disease (CJD) in humans. However, scientists have not been able to determine how prions were maintained and passed between cells and individuals if they were not associated with any nucleic acid. Now, recent work suggests that different types of prions are actually the same protein that has misfolded in different ways. Furthermore, one of these abnormally shaped proteins can infer its misfolding to normal prion proteins (PrP) by simple contact.

Researchers remain uncertain as to what causes PrP to misfold in the first place, perhaps a mutation. But once the change has occurred, abnormal prions induce normal PrP to misfold, and eventually prions crowd cells and cause nerve damage. When investigators injected prions of a different abnormal conformations into different hosts, the hosts developed prions with the same abnormal conformation as the parent prion. Still many scientists require more proof that prions are actually causing the nervous system disorders.

"Ironing Out the Wrinkles in the Prion Strain Problem," Science, vol. 274, page 2010, December 20, 1996