The characterization of conotoxins

Conotoxins are peptide toxins synthesized by marine cone snails for both prey entrapment and defense. The peptides, when injected into the prey, cause immobilization and death. Cone snails are widely distributed in tropical waters, their prey includes fish, worms and other marine snails. The peptide toxins have very high specificity and selectivity for a variety of neuro receptors and ion channels. This makes the toxins very useful in studies aimed at identifying receptors and their ligands, as well as in drug development studies. Conotoxins are notable at the level of primary amino acid sequence for their high percentage of cysteine residues and other post-translational modifications including hydroxylation of proline, gamma-carboxylation of glutamate, pyroglutamic acid formation, bromination of tryptophan and C-terminal amidation. This review describes traditional and more novel techniques for the characterization of conotoxins. In particular, the identification of the nature and the site of post-translational modifications is emphasized. Among the different techniques used to characterize the conotoxins, the important role played by mass spectrometry is emphasized.