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Definition Prions and Protein misfolding Diseases: Alzheimer’s disease, Creutzfeld-Jakob disease

Alzheimer’s disease
  • Prion protein was actually an internal coded protein by PRNP gene
  • Normal gene forms a protein PrPc (prion protein cellular) which is distributed on the nerve cell surface
  • The infectious counterpart PrPsc(prion protein scrapie) protein accumulates within nerve cells and ultimately kill neurons.
  • Both these protein forms have identical amino acid but they differ in the way the polypeptide chain folds to form the 3D functional protein molecule. PrPsc is highly stable, insoluble and protease insensitive and composed of β sheets  compared to PrPc  which is protease sensitive and entirely of α helical segments. 
  • Prions also cause other neurological diseases such as Kuru and Gerstmann-Strausler-Sheinker syndrome.
1.Alzheimer’s disease (AD)
  • non transmissable          
  • CJD and AD are very similar and both are fatal degenerative diseases resulting memory loss, confusion loss of reasoning.
  • Why AD?
  • Is due to fibrillar deposits of insoluble materials called Amyloid
  • Amyloid is due to self association of polypeptide composed predominantly of β sheets
  • AD: caused by A β peptide from APP gene. (amyloid precursor protein).
  • Vaccination for AD: APP vaccination (A β42 peptide injection).
2.CJD (Creutzfeld-Jakob disease)
  • a neurodegenerative disease
  • The causative organism remained a mystery for a long time until Stanley Prusiner discovered the unexpected proteinaceous infectious particles, the prions.
Key terms:
Domains: A part of protein with more than few hundred amino acid that can fold and function independently from rest of protein and may exist in different protein.
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