Molecular Characteristics of Four New Depressant Insect Neurotoxins Purified From Venom of Buthus martensi Karsch by HPLC

<正> Suitable pattern and high yield were obtained when the reverse-phase performance liquidchromatography (RP-HPLC) was used to separate neurotoxins from venom of Chinese scorpion Buthusmartensi Karsch.Using this technique,the venom was first separated to two main regions.The toxicitytests show that the insect-selective neurotoxical components are concentrated in the latter region,from whichfive insect-selective neurotoxins designated by BmK IT1-IT5 were obtained.According to the results of thetoxicity test as well as the amino acid composition and N-terminal analyses,BmK IT1 is the excitatory insectneurotoxin as reported in a previous paper,and the others are the newly found depressant insect-selectiveneurotoxins.The molecules of all the four toxins are single-chain minipeptides of about 60 amino acids.Their isoelectric points (pI) are between 8.3 and 8.5.The fact that BmK IT2 loses completely its insect tox-icity after being modified by fluorochrome shows that the positive charges on the molecular surface of thiskind of toxins are important to maintaining the bioactivity of the molecules.