A type of protein common in many cells that can become pathogenic when its peptide bonds produce abnormal folding on itself through its bonds at the atomic level. Even though it is an amino acid without genetic material, it has the ability to replicate in one organism and even infect others by copying the error into other cells, which occurs with diseases of the type "spongiform encephalopathy". The name is an acronym for PRotein infectION ("infection protein"), and was named after neurologist Stanley B. Prusiner (Nobel Prize in Physiology 1997). See bovine spongiform encephalopathy, mad cow, zombie deer.
