Prions
Not all infectious diseases are transmitted by bacteria or viruses. Some neurological diseases, such as Creutzfeldt-Jaakob disease (CJD) or mad cow disease are in fact caused by agents called Prions, which are of similar size to viruses but are made up of only protein [1] These diseases are can be called Prion diseases or transmissible spongiform encephalpathies (TSE) [2].
Prionshave these characteristics:
- "The transmissible agent consists of aggregated forms of a specific protein" [3].
- These protein aggregates cannot be degraded by the agents that degrade most other proteins [4].
- "The protein is largely or completely derived from a cellular protein called PrP, that is normally present in the brain" [5].
So an aggregated form of a protein (that is already present in the brain) is the infectious agent in prion diseases [6].
The pathalogic mechanism of prions is often associated with structural change. Exogenous prions cause the endogenous host proteins to undergo a structural change, rendering them functionless or harmful.
Prions size and structure enable them to resistance to
-proteases
-heat (not in 100 celsius)
-radiation
-fixative treatments (formaldehyde)
if only the secondary , tertitry and quaternary structure is destroy the prion can fold back to the prion after the influence of the substance
examples of prion disease
-scrapie (sheep)
-Bovie spongiform encephalopathy (BSE) mad cow disease
-Kuru (transmitted by ritual cannibalism)
References
- ↑ J. M. Berg et al. (2007) p 53, Biochemistry, Sixth edition, New York, W.H. Freeman and Company
- ↑ http://www.who.int/bloodproducts/tse/en/
- ↑ J. M. Berg et al. (2007) p 53, Biochemistry, Sixth edition, New York, W.H. Freeman and Company
- ↑ J. M. Berg et al. (2007) p 53, Biochemistry, Sixth edition, New York, W.H. Freeman and Company
- ↑ J. M. Berg et al. (2007) p 53, Biochemistry, Sixth edition, New York, W.H. Freeman and Company
- ↑ J. M. Berg et al. (2007) p 54, Biochemistry, Sixth edition, New York, W.H. Freeman and Company