Snake venom and mammalian salivary gland protein arose from shared genes

(ORDO NEWS) — Scientists from Japan and Australia have learned that the line between poisonous and non-venomous mammals and snakes is more blurred than expected. They also found that under certain conditions, non-poisonous animals that feed on milk can acquire toxic saliva. This also applies to people.

Organic poisons are a cocktail of toxic proteins needed to kill or immobilize prey. Snake venoms are especially difficult to study, and their origins are still obscure. Scientists from the Okinawa Institute of Science and Technology (Japan) and the Australian National University decided to shed light on this issue and focused on studying the class of toxins found in the venoms of most snakes, as well as reptiles and mammals (some of them are known to be capable of producing similar substances ).

Such poisons are called kallikrein serine proteases. These are enzymes that break down a protein that plays a key role in the regulation of blood pressure. In poisonous snakes and some mammals, these proteins have become toxic: when a large dose of such proteins enters the body, they can dramatically reduce blood pressure, cause loss of consciousness and even death of the victim.

In previous studies, the same group of scientists found that the salivary gland of mammals and the gland of snake venom have a similar structure of activity in a group of regulatory genes. However, similarity does not mean kinship. Nevertheless, in a new article published in the journal BMC Biology , the same authors still hypothesized that the ancestors of snakes and mammals had a common group of genes with toxic potential. And it seems they were not mistaken.

At one time, as you know, these groups of animals followed different evolutionary paths. At the same time, the ancestors of snakes evolved towards the development of various and more and more toxic poisons , but in the ancestors of mammals, the development of toxicity of the poison was much less. In addition, there are so many different serine proteases that have a high degree of similarity that it is not easy to isolate the genes needed to determine their evolutionary history.

Thanks to the latest advances in genomics, scientists have been able to identify and compare kallikrein genes in reptiles, amphibians, fish and mammals. They found that the serine proteases of snake venom kallikrein and mammalian salivary gland kallikreins were derived from a common ancestral gene.

It is the origin of the non-toxic salivary proteins found in both mice and humans. This means that the kallikrein proteins of the salivary glands of mammals, including humans, also have the potential to become toxic. However, the fact that we have the building blocks for the development of poison does not mean that this will happen. There must be good environmental reasons for this. The conclusions of the authors of the article only mean that the line between poisonous and non-venomous mammals and snakes is more blurred than expected.

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