MAD COW DISEASE
that the difference between them was a single amino acid change. The mutant one has the amino acid proline instead of leucine at position 34 on the chain.
This change is due to a point mutation, that is, a single base change in the protein gene is capable of causing such a deadly disease. It is important to tell you that the function of the normal protein is still unknown and that more than 15 mutations have been discovered that transform the PrP protein into an infections agent.
The proposed mechanism by which the mutant protein leads to the disease is as follows: The mutation in the prion induces a change in its structure (If you are interested it goes from what is called an alpha to a beta configuration), which inhibits its digestion in the brain and leads to its accumulation in the brain. This somehow causes the formation of vacuoles that give the brain the sponge like appearance.
Prussiner´s team was also criticized when they concluded that prions multiply in a way until that moment unheard of. Perversely, the disease-causing prions stick to the normal proteins, inducing them to change to the same shape. This, of course, converts them into pathological ones, thus increasing the size and number of the vacuoles. This process is a very slow one and that is why it takes so long for the disease to appear.
As you can imagine, Prussiner was awarded the Nobel Prize in Medicine for his finding.
The source of the epidemic in England was eventually traced to food contaminated with meat and bone from dead sheep. It seems that the problem started because they changed the processing of the sheep carcasses in such a way that the scrapie was not eliminated. The British government prohibited the use of animal-derived feed supplements in 1988, but the damage was already done.
In Europe almost half-a-million cows have been burned since 1996, and afterwards it was shown that only a few thousands of them were infected. This incredible economic loss could have been avoided if there have been an adequate test for the prions. Now it seems that there are some tests on the market that can detect the prions in hours. As matter of fact, Germany is testing 100 percent of the animals going to the slaughterhouse. Read this article to learn more about tests for
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