This shows some of the protein not visible in crystal structures. The green regions form Prp-SC specific epitopes. The red regions form epitopes in both forms of Prp. The disulfide is in yellow. An antibody against the blue region blocks Prp-Sc formation. (Note that one helix does show in cartoon format.)

James, T. L., Liu, H., Ulyanov, N. B., Farr-Jones, S., Zhang, H., Donne, D. G., Kaneko, K., Groth, D., Mehlhorn, I., Prusiner, S. B., Cohen, F. E.: Solution structure of a 142-residue recombinant prion protein corresponding to the infectious fragment of the scrapie isoform. Proc Natl Acad Sci U S A 94 pp. 10086 (1997) (PubMed)

2prp (PDB)