Which type of prion is associated with the spontaneous conversion of normal prion protein?

• A. PrP^C
• B. PrP^Sc
• C. Transmissible spongiform encephalopathy
• D. Prototypical prion

Answer: (B)

The association of spontaneous conversion of normal prion protein is attributed to the misfolded form, known as PrP^Sc. This form of the prion protein is derived from the normal cellular prion protein, PrP^C, through a process of conformational change.

PrP^C is the normal and non-infectious form found in healthy individuals. In contrast, PrP^Sc is infectious and is characterized by its abnormal structure, which promotes the misfolding of neighboring PrP^C molecules into more PrP^Sc. This self-propagating change is what leads to the accumulation of misfolded proteins and the development of prion diseases, such as transmissible spongiform encephalopathies.

Transmissible spongiform encephalopathy refers more generally to a range of diseases caused by prions but does not specifically identify the prion form responsible for the spontaneous conversion. Similarly, the term "prototypical prion" lacks a clear definition in this context, as it does not specifically refer to the mechanism by which prion diseases propagate. Therefore, the identification of PrP^Sc as the form associated with spontaneous conversion is crucial for understanding the pathology of prion diseases.