Science & Technology

Snake venom and mammalian saliva proteins evolved from the same ancestral gene


A new study found that the toxin classes found in snake and mammalian venoms evolved from genes of the same ancestry.

A new study found that the toxin classes found in snake and mammalian venoms evolved from genes of the same ancestry.

  • New studies show that the poisons found in snakes and mammals share a common origin.
  • Researchers have traced the origin of a class of toxins called kallikrein serine proteases to salivary proteins found in a common ancestor.
  • The results of the evolutionary tree showed that mammalian non-toxic salivary kallikrein, including those found in mouse and human saliva, also evolved from the same ancestral gene.
  • This study provides strong evidence of the hypothesis that the venom evolved from a general group of potentially toxic genes that existed in snake and mammalian ancestry.

Snakes, some lizards, and even a few mammals can bite poison. Although these strains split more than 300 million years ago, scientists reported today (December 22, 2021) that their toxins evolved from salivary proteins of the same ancestry. BMC biology..

With researchers from Okinawa Institute of Science and Technology Graduate University (OIST) in Japan Australian National University Focusing on the classes of toxins found in most snake venoms and all other reptile and mammalian toxins called kallikrein serine proteases, their origins have been traced back to genes found in a common ancestor.

“Venom is a toxic protein cocktail that has evolved throughout the animal kingdom as a way to kill and fix prey,” explained Agneesh Barua, co-lead author and PhD student at OIST. “The oral toxin system found in snakes is particularly complex, and the origin of those toxins is still unknown.”

Evolutionary tree of kallikrein serine protease

Salivary kallikrein, as found in mice, humans, and toxic mammals such as shrews and solenodon, is closely associated with the toxic serine protease kallikrein found in toxic snakes. Credit: OIST

In a previous paper, Balua and his colleagues found that mammalian salivary glands and snake venom glands share similar patterns of activity in groups of regulatory genes. This suggests that both snakes and mammals have the necessary foundations for the evolution of poisons.

“The paper assumed that snake and mammalian ancestors had a common group of genes that could be toxic,” Barua said. “Since then, snakes and mammals have taken different evolutionary paths, and snake strains have evolved diverse and increasingly toxic formulations, but in mammals, toxins have evolved, but to a much lower extent. But what we wanted to know was whether the toxins in mammalian and snake venom evolved from a common ancestral gene. “

Kallikrein serine proteases are a type of proteolytic enzyme that plays an important role in regulating blood pressure. Mammalian saliva contains small amounts of these proteins, but their function is unknown to date. However, in venomous snakes and mammals such as shrews and solenodon, these proteins have evolved toxicity. Large doses can significantly reduce blood pressure, cause loss of consciousness and even death.

Early on, researchers noticed the biochemical similarities between snake venom kallikrein serine proteases and mammalian saliva kallikrein serine proteases, but scientists have so far found that they are actually related. I didn’t know if it was there. “Because of the large number of different serine proteases that have a high degree of similarity, it has been very difficult to isolate the appropriate genes needed to determine evolutionary history,” Balua said. I am saying.

Recent advances in genomic techniques have allowed the research group to identify and compare all kallikrein genes in reptiles, amphibians, fish and mammals to create an evolutionary tree.

Excitingly, they discovered that the snake venom kallikrein serine protease and mammalian salivary kallikrein evolved from the same ancestral gene.

“This is really strong evidence of our hypothesis that the poison evolved from a common group of genes of ancestors that had the potential for toxicity,” Balua said. “But the most surprising thing was that the non-toxic salivary kallikrein found in humans and mice also evolved from the same ancestral gene.”

In fact, researchers have found that the non-toxic kallikrein in mammalian saliva is more closely associated with the venom found in snakes than in other mammalian kallikreins.

Overall, this evidence suggests that mammalian salivary kallikrein proteins, including humans, can also be evolutionarily toxic.

But Barua soon added, there is a warning. “Just because there are components to evolve poisons doesn’t mean that this will happen. Poisons are really expensive to make energetically, so they have a strong ecological nature that humans and most mammals don’t have. There had to be pressure. “

But what this tells us is that the line between poisonous and non-toxic mammals is blurry than previously thought.

Reference: “Co-selection of gene families of the same ancestry gave rise to toxins in mammals and reptiles” December 22, 2021 BMC biology..
DOI: 10.1186 / s12915-021-01191-1

Snake venom and mammalian saliva proteins evolved from the same ancestral gene Snake venom and mammalian saliva proteins evolved from the same ancestral gene

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