Purification and characterization of a neurotoxic peptide huwentoxin-III and a natural inactive mutant from the venom of the spider Selenocosmia huwena Wang (Ornithoctonus huwena Wang).

A novel neurotoxic peptide, named huwentoxin-III, and a natural mutant have been isolated from the venom of the spider Selenocosmia huwena Wang (Ornithoctonus huwena Wang). The average molecular weights of the two peptides were determined as 3853.35 and 3667.40 by mass spectrometry, respectively. Huwentoxin-III has 33 amino acid residues containing 6 cysteine residues. Its natural mutant is only truncated a tryptophan residue from C-terminals of huwentoxin-III. The sequences of the two peptides show 70.5% sequence similarity with that of lectin-like peptide SHL-I previously isolated from the venom of the same spider, while they cannot agglutinate human erythrocytes. Huwentoxin-III can reversibly paralyze cockroaches for several hours with an ED(50) of (192.95 +/- 120.84) microg/g (P=0.95) (mean +/- SD) and can enhance the muscular contractions elicited by stimulating the nerve of the isolated rat vas deferens, however, the mutant of huwentoxin-III has no such effect, which suggests that Trp33 was an important residue related to the biological function of huwentoxin-III.