WILTIMS #65: Grr. Argh.

Don't be a zombie! Eating brains is bad. We got to watch NOVA in class and it was as engaging as ever (albeit a bit dated in this case). The episode was on transmissible spongiform encephalopathies, such as scrapie (in sheep), mad cow disease (in... cattle) and Creutzfeldt–Jakob disease (in humans).

Normal prion protein on the left, mutant on the right.

These diseases are terrifying, as is their cause. Each disease is transmitted in one way: through the cannibalistic consumption of the brains of members of one's own species. The only exception is that certain forms of the disease can cross into other species, again, when brains are consumed. This was a major concern in Britain where the seemingly harmless sheep scrapie, which cannot transfer to humans, was introduced to cows, which were routinely fed protein supplement made from the ground remains of other cows and sheep. Once cows became infected, the toxin spread wildly through the same feed due to the cow component.

Creutzfeldt–Jakob disease (CJD) in humans was known to spontaneously arise very infrequently, causing the same symptoms seen in all other mammals. The patient rapidly loses motor coordination and then becomes progressively more demented, before dying within months. These spongiform encephalopathies are so named because the brain (encephalon) takes on a spongy appearance during autopsy do to the formation of many holes in the brain tissue. The disease progresses as more and more of the brain is consumed. There is no treatment. In the early nineties, people began coming down with a slightly different form of CJD, widely believed to have come from the the bovine disease that was transmitted through contaminated meat.

The biochemical cause of spongiform encephalopathy is very zombie-like. There is a normal version of a certain protein that is found in all healthy individuals. The disease is caused when a bad version of the protein is introduced that is able to bind with its healthy form in such a way so as to convert the normal form into the diseased form. It doesn't actually change the transcript of the protein. The order of the amino acids remains the same; the protein is merely folded differently. This causes a chain reaction that forms plaques of the aggregated diseased protein that build up and damage the surrounding tissue.

The protein can't be killed, because it's not alive and it is incredibly resistant to degradation, even when irradiated, burned and buried. Sleep well tonight!

TIL: There are protein motifs called "zinc fingers" formed by a zinc-stabilized hairpin turn. 

Epidermolysis bullosa is a disease resulting from the malformation of the keratin protein that results in incredibly fragile skin that blisters at even the softest touch.

Ehlers–Danlos syndrome is a collection of disorders caused by the mutation of genes involved in the organization of collagen. Collagen is the most abundant protein in the body and is generally found in connective tissue, providing a measure of flexible stability. Persons with this disease show many diverse symptoms, but a couple classic signs are of hyperflexible joints and stretchy skin that can be easily pulled away from the body.