The prion protein is known as PrP and is a cell surface glycophosphatidylinositol(GPI)-anchored protein. Its normal function in the body is unknown, though presumably it serves, or served, some purpose because it is coded for by a host gene. The infectious form of PrP has the same amino acid sequence and the same post-translational modifications as the normal form, but it has a different tertiary conformation. The normal PrP contains many alpha-helices, whereas the disease-associated form contains many beta-pleated sheets. It is this conformational change from mostly alpha-helices to mostly beta-pleated sheets that gives the prion its infectious ability.