Figure 1.

Conotoxin expression. (A) Conotoxins are produced in the venom apparatus that consists of (1) the venom bulb—a muscular organ that is used as a pump, (2) the venom duct which produces the venom, (3) the radular sac that stores the harpoons. Harpoons are evolutionarily modified radula teeth that are used to inject venom into the prey, like a hypodermic needle, (4) the proboscis is used to “load” (5) the harpoon at the tip to inject venom; and, (B) The venom peptides are translated as prepropeptide. They consist of a conserved N-terminal made up of the signal sequence and propeptide region which are cleaved during peptide processing. The final bioactive conotoxin consists of only the C-terminal region, which is also the disulfide rich hypervariable region of the prepropeptide.