Discovery of a novel class of conotoxin from Conus litteratus, lt14a, with a unique cysteine pattern.

Conus litteratus is a worm-hunting cone snail with a highly sophisticated neuropharmacological defense strategy using small peptides in its venom. By analyzing different clones in the cDNA library of venom ducts from C. litteratus, we identified the peptide lt14a which displays a characteristic signal peptide sequence in its precursor and a unique arrangement of Cys residues (-C-C-C-C-) in its mature peptide region. RT-PCR analysis suggested that lt14a is abundantly expressed throughout the whole venom duct. An intensive analysis in sequence suggested that lt14a is similar to alpha-conotoxin qc1.1 cloned from Conus quercinus. We conducted the chemical synthesis of lt14a. The synthetic lt14a has a remarkable biological activity to suppress pain and inhibits the neuronal-type nicotinic acetylcholine receptors.