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Putting the brakes on snake venom evolution: the unique molecular evolutionary patterns of Aipysurus eydouxii (Marbled sea snake) phospholipase A2 toxins.
Mol Biol Evol. 2005 Apr; 22(4):934-41.MB

Abstract

Accelerated evolution of toxins is a unique feature of venoms, with the toxins evolving via the birth-and-death mode of molecular evolution. The venoms of sea snakes, however, are remarkably simple in comparison to those of land snakes, which contain highly complex venoms. Aipysurus eydouxii (Marbled sea snake) is a particularly unique sea snake, feeding exclusively upon fish eggs. Secondary to this ecological change, the fangs have been lost and the venom glands greatly atrophied. We recently showed that the only neurotoxin (a three-finger toxin) gene found in the sea snake A. eydouxii has a dinucleotide deletion, resulting in the loss of neurotoxic activity. During these studies, we isolated and identified a number of cDNA clones encoding isozymes of phospholipase A(2) (PLA(2)) toxins from its venom gland. Sixteen unique PLA(2) clones were sequenced from the cDNA library and TA cloning of reverse transcription-polymerase chain reaction products. Phylogenetic analysis of these clones revealed that less diversification of the PLA(2) toxins has occurred in the A. eydouxii venom gland in comparison to equivalent terrestrial and other marine snakes. As there is no longer a positive selection pressure acting upon the venom, mutations have accumulated in the toxin-coding regions that would have otherwise had a deleterious effect upon the ability to use the venom for prey capture. Such mutations include substitutions of highly conserved residues; in one clone, the active site His(48) is replaced by Arg, and in two other clones, highly conserved cysteine residues are replaced. These mutations significantly affect the functional and structural properties of these PLA(2) enzymes, respectively. Thus, in A. eydouxii, the loss of the main neurotoxin is accompanied by a much slower rate of molecular evolution of the PLA(2) toxins as a consequence of the snake's shift in ecological niche. This is the first case of decelerated evolution of toxins in snake venom.

Authors+Show Affiliations

Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15635056

Citation

Li, Min, et al. "Putting the Brakes On Snake Venom Evolution: the Unique Molecular Evolutionary Patterns of Aipysurus Eydouxii (Marbled Sea Snake) Phospholipase A2 Toxins." Molecular Biology and Evolution, vol. 22, no. 4, 2005, pp. 934-41.
Li M, Fry BG, Kini RM. Putting the brakes on snake venom evolution: the unique molecular evolutionary patterns of Aipysurus eydouxii (Marbled sea snake) phospholipase A2 toxins. Mol Biol Evol. 2005;22(4):934-41.
Li, M., Fry, B. G., & Kini, R. M. (2005). Putting the brakes on snake venom evolution: the unique molecular evolutionary patterns of Aipysurus eydouxii (Marbled sea snake) phospholipase A2 toxins. Molecular Biology and Evolution, 22(4), 934-41.
Li M, Fry BG, Kini RM. Putting the Brakes On Snake Venom Evolution: the Unique Molecular Evolutionary Patterns of Aipysurus Eydouxii (Marbled Sea Snake) Phospholipase A2 Toxins. Mol Biol Evol. 2005;22(4):934-41. PubMed PMID: 15635056.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Putting the brakes on snake venom evolution: the unique molecular evolutionary patterns of Aipysurus eydouxii (Marbled sea snake) phospholipase A2 toxins. AU - Li,Min, AU - Fry,Bryan G, AU - Kini,R Manjunatha, Y1 - 2005/01/05/ PY - 2005/1/7/pubmed PY - 2005/9/27/medline PY - 2005/1/7/entrez SP - 934 EP - 41 JF - Molecular biology and evolution JO - Mol Biol Evol VL - 22 IS - 4 N2 - Accelerated evolution of toxins is a unique feature of venoms, with the toxins evolving via the birth-and-death mode of molecular evolution. The venoms of sea snakes, however, are remarkably simple in comparison to those of land snakes, which contain highly complex venoms. Aipysurus eydouxii (Marbled sea snake) is a particularly unique sea snake, feeding exclusively upon fish eggs. Secondary to this ecological change, the fangs have been lost and the venom glands greatly atrophied. We recently showed that the only neurotoxin (a three-finger toxin) gene found in the sea snake A. eydouxii has a dinucleotide deletion, resulting in the loss of neurotoxic activity. During these studies, we isolated and identified a number of cDNA clones encoding isozymes of phospholipase A(2) (PLA(2)) toxins from its venom gland. Sixteen unique PLA(2) clones were sequenced from the cDNA library and TA cloning of reverse transcription-polymerase chain reaction products. Phylogenetic analysis of these clones revealed that less diversification of the PLA(2) toxins has occurred in the A. eydouxii venom gland in comparison to equivalent terrestrial and other marine snakes. As there is no longer a positive selection pressure acting upon the venom, mutations have accumulated in the toxin-coding regions that would have otherwise had a deleterious effect upon the ability to use the venom for prey capture. Such mutations include substitutions of highly conserved residues; in one clone, the active site His(48) is replaced by Arg, and in two other clones, highly conserved cysteine residues are replaced. These mutations significantly affect the functional and structural properties of these PLA(2) enzymes, respectively. Thus, in A. eydouxii, the loss of the main neurotoxin is accompanied by a much slower rate of molecular evolution of the PLA(2) toxins as a consequence of the snake's shift in ecological niche. This is the first case of decelerated evolution of toxins in snake venom. SN - 0737-4038 UR - https://www.unboundmedicine.com/medline/citation/15635056/Putting_the_brakes_on_snake_venom_evolution:_the_unique_molecular_evolutionary_patterns_of_Aipysurus_eydouxii__Marbled_sea_snake__phospholipase_A2_toxins_ L2 - https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msi077 DB - PRIME DP - Unbound Medicine ER -