James adds that "the multiple structures evident are probably related to the different types of prion diseases which an individual can potentially get." Prion variants affect different parts of the human brain, causing either Creutzfeldt-Jakob disease (CJD), Fatal Familial Insomnia (FFI), Kuru, or Gerstmann-Straussler- Scheinker (GSS) disease.
To reduce risks to laboratory workers, the scientists studied a prion protein from Syrian hamsters. They describe the normal prion structure and show the region of structural instability. James says that area coincides with a sequence of genetic instructions in which different mutations can lead to various diseases. Further, he claims that their structure provides a chemical explanation for the variety of infectious prions.
Previous epidemiological studies, in both humans and sheep, showed that individuals with positively charged amino acid residues in certain regions of their normal prions do not get prion diseases. James says their 3-D structure shows those residues to be fairly close to one another. "This suggests," he asserts, "that breeding animals with mutations to positively charged residues in that region will produce a scrapie-resistant or BSE (mad cow)-resistant herd."