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Prions are infectious proteins that cause degeneration of the central nervous system (CNS). Prion diseases are disorders of protein conformation, the most common of which in humans is called Creutzfeldt-Jakob disease (CJD). CJD typically presents with dementia and myoclonus, is relentlessly progressive, and generally causes death within a year of onset. Most CJD patients are between 50 and 75 years of age; however, patients as young as 17 and as old as 83 have been recorded.

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In mammals, prions reproduce by binding to the normal, cellular isoform of the prion protein (PrPC) and stimulating conversion of PrPC into the disease-causing isoform (PrPSc). PrPC is rich in α-helix and has little β-structure, while PrPSc has less α-helix and a high amount of β-structure (Fig. 383-1). This α-to-β structural transition in the prion protein (PrP) is the fundamental event underlying prion diseases (Table 383-1).

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Figure 383-1
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Structures of prion proteins. A. NMR structure of Syrian hamster recombinant (rec) PrP(90–231). Presumably, the structure of the α-helical form of recPrP(90–231) resembles that of PrPC. recPrP(90–231) is viewed from the interface where PrPSc is thought to bind to PrPC. Shown are: α-helices A (residues 144–157), B (172–193), and C (200–227). Flat ribbons depict β-strands S1 (129–131) and S2 (161–163). (A, from SB Prusiner: N Engl J Med 344:1516, 2001; with permission.) B. Structural model of PrPSc. The 90–160 region has been modeled onto a β-helical architecture while the COOH terminal helices B and C are preserved as in PrPC. (Image prepared by C. Govaerts.)

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Table Graphic Jump Location
Table 383-1 Glossary of Prion Terminology
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