Conotoxin

A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus. A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus. Conotoxins, which are peptides consisting of 10 to 30 amino acid residues, typically have one or more disulfide bonds. Conotoxins have a variety of mechanisms of actions, most of which have not been determined. However, it appears that many of these peptides modulate the activity of ion channels.Over the last few decades conotoxins have been the subject of pharmacological interest. The LD50 of conotoxin is 50 ng/kg. Conotoxins are hypervariable even within the same species. They do not act within a body where they are produced (endogenously) but act on other organisms. Therefore, conotoxins genes experience less selection against mutations (like gene duplication and nonsynonymous substitution), and mutations remain in the genome longer, allowing more time for potentially beneficial novel functions to arise. Variability in conotoxin components reduces the likelihood that prey organisms will develop resistance; thus cone snails are under constant selective pressure to maintain polymorphism in these genes because failing to evolve and adapt will lead to extinction (Red Queen hypothesis). Types of conotoxins also differ in the number and pattern of disulfide bonds. The disulfide bonding network, as well as specific amino acids in inter-cysteine loops, provide the specificity of conotoxins.