A new cysteine framework in sodium channel blocking conotoxins

Two conotoxins obtained from the venom of molluscivorous snail Conus pennaceus, PnIVA and PnIVB, block the sodium channels in the neurons of molluscs but are ineffective on the sodium channels in bovine chromaffin cells and rat brain synaptosomes. The amino acid sequences of the conotoxins reveal the presence of a cysteine framework, hence the nomenclature IV is used. Peptide toxins from snail venom are small and fall into pharmacological or chemical groups based on structure and activities on target receptors.