Abstract: Cone snails are tropical marine predatory molluscs, and there is an unprecedented variety of neuropharmacologically active peptide. Over seventy living species of cone snails are distributed in China. The ve-nom of Conus caracteristicus collected from South China Sea was studied in this work. A new conotoxin, cr5a, was isolated from the venom through Sephadex G-25 chromatography and HPLC, and then was identified by amino acid analysis, mass spectrometry, N-terminal sequence. The primary structure of cr5a was CCKFQFLNFCCNE, it shared a conserved T-superfamily of conotoxins arrangement of cysteine residues(CC-CC). Total chemical synthesis of the two possible disulfide linkages of cr5a was achieved, and the result of HPLC co-elution showed that cr5a was a tridecapeptide with a disulfide connectivity of Cys¹-Cys¹⁰, Cys²-Cys¹¹. So cr5a is a new member of the T-superfamily conotoxins.

Key words: Conotoxins, T-superfamily, Conus caracteristicus, Structure characterization