An Indian researcher and his team have discovered that venoms from different families of snakes have many deadly ingredients in common.
A study has unexpectedly discovered three-finger toxins in a subspecies of the Massasauga Rattlesnake, as well as evidence for a novel toxin genes resulting from gene fusion.
The Indian researcher leading the study was Susanta Pahari from National University of Singapore, Singapore, currently working at Sri Bhagawan Mahaveer Jain College, Bangalore, India. Her team included Stephen Mackessy from the University of Northern Colorado, USA and R. Manjunatha Kini from National University of Singapore.
She used venom glands from a rare rattlesnake that lives in arid and desert grasslands. This pitviper also known as Desert Massasauga (Sistrurus catenatus edwardsii), is a subspecies of the North American Massasauga Rattlesnake (Sistrurus catenatus).
The team constructed a cDNA library of the snake's venom gland and 576 tagged sequences were created.
They detected a cocktail of recognized venom toxin sequences in the library, but the venom also contained three-finger toxin-like transcripts, a family of poisons believed only to occur in another family of snakes (Elapidae).
They also pointed out a novel toxin-like transcript generated by the fusion of two individual toxin genes, a mechanism not previously observed in toxin evolution.
The diversity in toxins usually results from gene duplication and subsequently neofunctionalization is achieved through several point mutations (called accelerated evolution) on the surface of the protein.
"In addition to gene duplication, exon shuffling or transcriptional splicing may also contribute to generating the diversity of toxins and toxin isoforms observed among snake venoms," said Pahari
Earlier, the researchers identified venom compounds using protein chemistry or individual gene cloning methods. Though, less abundant toxins were often missed.
Now, the library method has discovered new toxin genes and even new families of toxins.
Advanced snakes' venoms were actually shown to have a greater similarity than previously known, by taking low abundance toxins into consideration
Snake venoms are complex mixtures of pharmacologically active proteins and peptides.
It can be complicated to treat the victims of snake as there's a variation between venoms even within snake families.
"Such a diversity of toxins provides a gold mine of bioactive polypeptides, which could aid the development of novel therapeutic agents," said Kini.
The study is published in the online open access journal BMC Molecular Biology.