The Making of the Fittest by Sean B. Carroll

Author:Sean B. Carroll [Carroll, Sean B.]
Language: eng
Format: epub, mobi
Publisher: W. W. Norton
Published: 2010-01-31T06:00:00+00:00

VCRDWFKETACRHAKSLGNCRTSQKYRANCAKTCELC

ZFTNVSCTTSKECWSVCQRLHNTSRGKCMNKKCRCYS

CRIONQKCFQHLDDCCSRKCNRFNKCG

ZPLRKLCILHRNPGRCYQKIPAFYYNG

KKKQCEGFTWSGGCGGNSNRFKTIEECRRTCIRKD

Do any similarities pop out at you?

No?

Well, don’t feel bad. I don’t see any either, but they do have something in common.

Here is a clue to the story. The fourth protein comes from a snake. I have been interested in snakes all my life and I have always taken the opportunity to look for snakes when I travel to places with interesting species. This protein sequence comes from the only snake that ever truly terrified me. I visited a very small reptile collection near Lake Baringo in Kenya and one of the keepers was delighted to bring out a very jumpy nine-or ten-foot-long black mamba to show me. The snake was so fast and agile. I kept trying to back farther away, but the handler just brought him closer.

Had the handler made a mistake, neither he nor I would have had long to think about it. A black mamba bite can be fatal in thirty minutes. The venom contains potent neurotoxins (the sequence of a major toxin is the fourth protein sequence in the list above). The neurotoxin kills by blocking so-called potassium channels. These channels play a critical role in the electrical signals that pass among neurons and muscles. When their function is blocked, so are nerve and muscle function. Victims of black mamba bites typically display neurological and muscle problems and, if untreated, die of respiratory paralysis.

The other three proteins in the list are also potassium channel blockers found in venom. Here is the amazing part of the story—the first protein comes from a sea anemone, the second protein is from a scorpion, and the third protein is from a marine cone shell snail. Each of these animals, as well as the black mamba, belongs to a different animal phylum—the anemone is a cnidarian, the scorpion is an arthropod, the cone shell is a mollusk, and the snake a vertebrate. Each of these venom toxins evolved independently of one another and represent different molecular solutions for the binding to and blocking of potassium channels of their prey. They are different molecules with different origins but a common, deadly purpose.

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