Discovery of a Novel Cysteine Framework XXIV Conotoxin from Conus striatus , S24a, with Potential Analgesic Activity

A novel conotoxin, S24a, containing 26 amino acid residues was first derived from the cDNA library of Conus striatus . This conotoxin has the same conserved signal peptide as A-superfamily conotoxins and some unconserved residues in the pro-region. According to the mature peptide sequence of this conotoxin, S24a was prepared by the Escherichia coli expression system and purified by affinity chromatography, Sephadex gel filtration and reversed-phase high-performance liquid chromatography (RP-HPLC). The molecular weight of S24a was identified by MALDI-TOF-MS. Biological function experiments showed that S24a could inhibit frog sciatic nerve muscle contraction. Moreover, a high dose of S24a (100 μg/kg) had more potent and longer lasting analgesic activity compared with lidocaine and pethidine in the hotplate pain model and the formalin pain model in mice, which indicated that S24a can be further developed as a potential analgesic drug lead.