δ-Conotoxins Synthesized Using an Acid-cleavable Solubility Tag Approach Reveal Key Structural Determinants for NaV Subtype Selectivity

Conotoxins are venom peptides from cone snails with multiple disulfide bridges that provide a rigid structural scaffold. Typically acting on ion channels implicated in neurotransmission, conotoxins are of interest both as tools for pharmacological studies and as potential new medicines. -Conotoxins act by inhibiting inactivation of voltage-gated sodium channels (Na-v). Their pharmacology has not been extensively studied because their highly hydrophobic character makes them difficult targets for chemical synthesis. Here we adopted an acid-cleavable solubility tag strategy that facilitated synthesis, purification, and directed disulfide bridge formation. Using this approach we readily produced three native -conotoxins from Conus consors plus two rationally designed hybrid peptides. We observed striking differences in Na-v subtype selectivity across this group of compounds, which differ in primary structure at only three positions: 12, 23, and 25. Our results provide new insights into the structure-activity relationships underlying the Na-v subtype selectivity of -conotoxins. Use of the acid-cleavable solubility tag strategy should facilitate synthesis of other hydrophobic peptides with complex disulfide bridge patterns.