omega-conotoxin MVIIA
omega-conotoxin mviia
A heterodetic cyclic polypeptide consisting of the linear sequence Cys-Lys-Gly-Lys-Gly-Ala-Lys-Cys-Ser-Arg-Leu-Met-Tyr-Asp-Cys-Cys-Thr-Gly-Ser-Cys-Arg-Ser-Gly-Lys-Cys-NH<small><sub>2</sub></small> with three disulfide bridges between cysteine residues 1-16, 8-20 and 15-25.  A neuronal N-type Ca<small><sup>2+</small></sup> channel blocker in mammalian and amphibian brain, it blocks release of GABA and glutamate at neuronal synapses. Used as a probe for calcium channel receptors, it is selective for different receptor subtypes. A synthetic form, named ziconotide, is an atypical analgesic agent for the amelioration of severe and chronic pain.