Which of the following is the abnormal conformational state of the prion protein?

• A. PrP^C
• B. PrP^Sc
• C. Scrapie
• D. Prion variant

Answer: (B)

The abnormal conformational state of the prion protein is identified as PrP^Sc. This form is derived from the normal prion protein, PrP^C, which is predominantly found in a healthy state within the brain and other tissues.

PrP^Sc is characterized by a misfolded structure that aggregates into amyloid plaques, which are associated with various neurodegenerative diseases, including Creutzfeldt-Jakob disease and variant Creutzfeldt-Jakob disease. The key difference between PrP^Sc and PrP^C lies in their secondary structures; PrP^Sc has an increased amount of beta-sheet content compared to the alpha-helices found in PrP^C. This structural change not only allows PrP^Sc to resist proteolytic degradation but also to induce the misfolding of other normal PrP^C proteins into the abnormal PrP^Sc state, thereby propagating the disease.

The other choices refer to variations of the prion protein or related concepts. Scrapie is a specific prion disease affecting sheep; it implicates the presence of PrP^Sc but does not directly identify the abnormal conformational state. Prion variant refers to different strains or types of prion