Prions
A Prion is a normal protein that is found on the membranes of cells. The normal Prion protein (PrPC) consist mainly alpha helix rich 30-35kDa glycoprotein with 209 amino acid sequence and one disulfide bond (1). The disease causing form of normal prion protein named after scrapie (PrPSc) occurs when properly folded normal prion protein change its conformation. Although the exact tertiary structure of PrPSc still remains elusive but the previous studies have shown that the secondary structure of infectious protein contains high proportion of beta sheet in place of normal alpha helix. The increased content of beta sheet in PrPSc leads to the formation of aggregates resistant to proteases that assemble into amyloid fibers and accumulate to form plaques in brain cells (2).
Prions are extremely small unique pathogens and have no nucleic acid. The PrpSc protein cannot self replicate but causes other normal prion proteins to change the conformation making them infectious. The process by which the infectious prion recruits the normal protein is still unclear. All known prion disease commonly known as transmissible spongiform encephalopathies to date is untreatable and fatal. Some of the common prion disease found in humans includes Creutzfeldt-Jakob disease (CJD), Variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Straussler-Scheinker Syndrome, Fatal Familial insomnia, and Kuru. Besides human prions disease is also prevalent in animals causing Bovine Spongiform Encephalopathy (BSC) also known as mad cow disease, Chronic Wasting Disease, Scrapie, Transmissible mink encephalophathy, Feline spongiform encephalophathy. The new human prion disease vCJD was first reported in United Kingdom in 1996 and was believed to come from feeding the meat of cattle infected with mad cow disease.
Prion disease can be transmitted by ingestion of BSC contaminated food products especially beef and may also be transmitted by using contaminated surgical instruments. It can also be
Prions are extremely small unique pathogens and have no nucleic acid. The PrpSc protein cannot self replicate but causes other normal prion proteins to change the conformation making them infectious. The process by which the infectious prion recruits the normal protein is still unclear. All known prion disease commonly known as transmissible spongiform encephalopathies to date is untreatable and fatal. Some of the common prion disease found in humans includes Creutzfeldt-Jakob disease (CJD), Variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Straussler-Scheinker Syndrome, Fatal Familial insomnia, and Kuru. Besides human prions disease is also prevalent in animals causing Bovine Spongiform Encephalopathy (BSC) also known as mad cow disease, Chronic Wasting Disease, Scrapie, Transmissible mink encephalophathy, Feline spongiform encephalophathy. The new human prion disease vCJD was first reported in United Kingdom in 1996 and was believed to come from feeding the meat of cattle infected with mad cow disease.
Prion disease can be transmitted by ingestion of BSC contaminated food products especially beef and may also be transmitted by using contaminated surgical instruments. It can also be
References: 1. PamKM, Baldwin M, Nguyen J et al. Conversion of alpha helices into beta sheets features in the formation of the scrapie prion protein. Proceedings of the National Acedemics of science of the United State of America 90 (23) : 10962-6. (December 1993).