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The rapid evolution of cobra venom

Posted December 4, 2013
How did the cobra get its bite?
King cobra. Credit: Khao Khieo
A new study has provided the first comprehensive insight into how snake venom evolved into the sophisticated cocktail of different proteins it is today.

It turns out that snakes’ venom glands have co-opted many proteins that originally played more mundane roles elsewhere in their bodies. This constant innovation was needed to help them stay ahead of the animals they eat, which tend to develop resistance to particular venoms over time.

Researchers at Bangor University, the Liverpool School of Tropical Medicine and the universities of Leiden in Holland and Texas, Arlington in the USA sequenced genomes of the deadly venomous King Cobra and the non-venomous Burmese Python, and compared the two to shed light on how each evolved. They also looked at the only other venomous vertebrate genome that’s been sequenced so far – that of the platypus.

In particular, lead author Dr Nick Casewell and his colleagues were interested in how the cobra’s venom evolved. It contains dozens of highly specialised toxins, and exactly how this complex brew could have come about has long been a puzzle.

Analysing the newly-sequenced cobra genome confirmed the hypothesis that the individual toxins that make up the venom developed from proteins that originally evolved for unglamorous day-to-day tasks elsewhere in the body.

The genes responsible for these proteins have been duplicated many times, allowing the original version to keep doing its job while the copy mutates further and takes on new functions. This allows the proteins taken up by the venom system to multiply and diversify away from their original purposes and contribute to the increasingly complex venomous cocktail, forming lethal suites of chemicals that interact with each other to do more harm to prey.

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