Botulinum toxins are some of the most deadly neurotoxins known to man, with lethal doses in the region of 1 to 3 nanograms per kilogram, but people also pay extravagant sums to have them injected into their bodies for health and cosmetic issues. Botulinum toxin acts by indirectly inhibiting the release of acetylcholine as the nerve ending, leading to partial or full paralysis of the innervated tissue. This paralysis, depending on the dose and type of botulinum toxin, can last upwards of six months. While this protein is most commonly associated with cosmetic “botox,” localized long term paralysis can be instrumental in treating a variety of disorders involving spasms and overactivity. Despite its lethality, botulinum toxin is still able to be harnessed for medicine through careful use and botox injections have been the most common cosmetic operation since 2007.
Lethal when inhaled or injected, this protein can be found at virtually any local hospital. Still, the most potent strains can kill in smaller doses than any other compound known to man. Less than two kilograms is enough to kill every living person on the planet. The power of this elegantly simple protein, less than 150 kDa, is what makes it so spectacular. Other proteins may facilitate crucial reactions or have intricate structures, but this incredibly simple, small, globular protein has more power than any of them. If you can find another protein that would have such an extreme impact on an organism in such a small dose, you'll win my vote. If not, I find it hard to argue against this being the protein of the year.
Here are some views of the structure. Note how the simplicity; one would never guess that such a bland looking structure could be so deadly.
Simple ribbon view indicating the beginning and end of the chain by color
This protein is also a Wisconsin Badgers fan
