Secondary Structure Study of Huwentoxin-I,a Neurotoxin from the Venom of the SpiderSelenocosmia Huwena

Huwentoxin-I is a low molecular weight peptide toxin which blocks the transmission of neuro-muscular junction of vertebrates. This toxin consists of 33 amino acid residues with three disulphide bonds. The circular dichroism spectra of the toxin in different conditions were measured and analysed. The contents of various secondary structure elements were calculated with the computer program according to the method of Greenfield, 22-28 percent of amino acid residues is in α-belix, 22-35 percent in β-sheet and 41-49 percent in random coil or β turn. Tbe contents of secondary structure elements of tbe toxin were found to be relatively stable under different pH and after heating at 80℃ for 20 min. The investigation with different methods of secondary structure prediction reveals that most part at the middle of the peptide sequence of the toxin is in random coil or β-turn conformation, while a small β-sheet is formed at the N-terminal and an α-helix at the C-terminal.