cDNA cloning of two novel T-superfamily conotoxins from Conus leopardus

The full-length cDNAs of two novel T-superfamily conotoxins,Lp5.1 and Lp5.2,were cloned from a vermivorous cone snail Conus leopardus using 3'/5'-rapid amplification of cDNA ends.The cDNA of Lp5.1 encodes a precursor of 65 residues,including a 22-residue signal peptide,a 28-residue propeptide and a 15-residue mature peptide.Lp5.1 is processed at the common signal site -X-Arg- immediately before the mature peptide sequences.In the case of Lp5.2,the precursor includes a 25-residue signal peptide and a 43-residue sequence comprising the propeptide and mature peptide,which is probably cleaved to yield a 29-residue propeptide and a 14-residue mature toxin.Although these two conotoxins share a similar signal sequence and a conserved disulfide pattern with the known T-superfamily,the pro-region and mature peptides are of low identity,especially Lp5.2 with an identity as low as 10.7% compared with the reference Mr5.1a. The elucidated cDNAs of these two toxins will facilitate a better understanding of the species distribution, the sequence diversity of T-superfamily conotoxins,the special gene structure and the evolution of these peptides.