Prion diseases (transmissible spongiform encephalopathies) are characterised by conversion of normal cellular prion protein (PrPC) to the pathological isoform PrPSc. The two isoforms differ in:

• A Tertiary conformation — PrPSc has increased beta-sheet content and is protease-resistant ✓
• B Primary amino acid sequence — PrPSc has unique mutations at multiple codons
• C Glycosylation pattern — PrPSc is unglycosylated
• D Cellular location — PrPC is intracellular while PrPSc is extracellular only

Explanation

PrPC (normal) and PrPSc share the same amino acid sequence, encoded by the PRNP gene, but differ in tertiary folding: PrPC is predominantly alpha-helical and proteinase K-sensitive, while PrPSc has a predominant beta-sheet conformation making it protease-resistant, detergent-insoluble, and prone to aggregation. PrPSc acts as a template that catalyses conversion of PrPC to the beta-sheet conformation — a conformational change without any mutation in the coding sequence. Both isoforms are GPI-anchored glycoproteins.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.