It's not a nucleic acid. Nucleic acids are the basic component of DNA and RNA, the chemicals that carry life's genetic code. Prions are sometimes compared to beta amyloid protein, which form brain insoluble plaques in Alzheimer's disease . In its normal, soluble shape, amyloid protein causes neither plaque nor disease. Courtesy Manuel C. Peitsch , Glaxo Institute of Molecular Biology , Geneva, Switzerland.
Proteins are huge, complex molecules whose function is heavily influenced by shape.
Prusiner hypothesized that normal prions twist into a shape that both causes disease and, chain-reaction fashion, distorts other prions into a new shape, which has new and dangerous properties. Many biologists deemed the hypothesis heresy. As virologists searched in vain for a viral explanation for the disease, Prusiner and his colleagues gradually built their case. Today, although a few scientists consider prions a marker rather than a cause of TSEs, the prion hypothesis is well accepted. Still, lots has been learned about prions and TSEs in the past few years.