Prion diseases have been described in a number of mammals and in man. Now that I have your attention. A prion is a protein that can cause disease. NO virus, bacteria, fungus, or parasite causes the diseases mentioned above. Researchers have shown that when the PrP is mutated at certain places in the protein its shape changes.
Biochemists use the term conformation when talking about protien shape.
To see what these protein conformations look like go to The Hypertext Biology Textbook . When mutated the PrP has a beta-pleated sheet shape. Fold up a sheet of paper lengthwise several times and then look at the end of the paper while still folded. That is sort of what it looks like. The mutant PrP causes the normal PrP to change in conformation from the alpha helical to the beta-pleated sheet.