Conotoxin

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.

The number of conotoxins whose activities have been determined so far is five, and they are called the α(alpha)-, δ(delta)-, κ(kappa)-, μ(mu)-, and ω(omega)- types. Each of the five types of conotoxins attacks a different target:


 * α-conotoxin inhibits acetylcholine receptors at nerves and muscles.
 * δ-conotoxin inhibits the inactivation of voltage-dependent sodium channels.
 * κ-conotoxin inhibits potassium channels.
 * μ-conotoxin inhibits voltage-dependent sodium channels in muscles.
 * ω-conotoxin inhibits N-type voltage-dependent calcium channels. Because N-type voltage-dependent calcium channels are related to algesia (sensitivity to pain) in the nervous system, ω-conotoxin has an analgesic effect: the effect of ω-conotoxin M VII A is 100 to 1000 times that of morphine. Therefore a synthetic version of ω-conotoxin M VII A has found application as an analgesic drug ziconotide (Prialt ® ).