cDNA sequence analysis of seven peptide toxins from the spider Selenocosmia huwena

Seven cDNAs encoding six toxins HWTX-I, HWTX-II, HWTX-IIIa, HWTX-IV, HWTX-V, HWTX-VII and one lectin SHL-I, from the spider Selenocosmia huwena, were cloned and sequenced. On the basis of their amino acid sequences, we designed and synthesized 3' RACE and 5' RACE primer. By overlapping the two partial cDNA sequences obtained by 3' and 5' RACE, their full-length cDNA sequences were obtained. All of the cDNAs of these seven peptides encode a precursor including a potential signal peptide of 21-24 residues, a mature toxin of about 30 residues and an intervening pro region. The prepro regions of HWTX-I, HWTX-IIIa, HWTX-IV, HWTX-V and SHL-I were demonstrated, by the comparison of the cDNA sequences, to have high similarity, which is concert with the similar inhibitor cystine knot motif of HWTX-I, HWTX-IV and SHL-I although their functions are different. It was also demonstrated that, HWTX-II and HWTX-VII share the highly similar prepro region which is different from that of HWTX-I, HWTX-IV and SHL-I. The three dimensional structure of HWTX-II has been determined to exhibit a different motif. This indicates that the seven peptides from S. huwena could be classified into two different superfamilies according to the prepro region of cDNA sequences.