Covalent structure of the insect toxin of Androctonus australis Hector

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Abstracts COVALENT STRUCTURE OF THE INSECT TOXIN OF ANDROCTONUS AUSTRALIS HECTOR Hervé DARBON, Hervé ROCHAT, Charles KOPEYAN, Jurphaas VAN RIETSCHOTEN and Eliahu ZLOTKIN

H . Darbon, H . Rochst, C . Kopeyan, J . Van Rietschoten : Laboratoire de Biochimie, Faculté de Médecine Secteur Nord, Hd . P . Dramard, 13326 Marseille Cedex 3 . E . Zlotkin : Department of Zoology, The Hebrew University of Jerusalem, Israël . Contrary to scorpion venoms which are highly toxic when injected to insect, it has been shown that the scorpion toxins, lethal to mice and therefore called "mammal toxins", are not active on insect (Zlotkin et al ., 1972a, b) . This observation prompted the purification, from the venoms of Androctonus aus tralis Hector and Androctonus mauretanicus mauretanicus ,of proteins, the "insect toxins" AaH IT and Amm IT, that are responsible for the activity on insects (Zlotkin et al ., 1979) . In the present work, the complete amino acid sequence of AaH IT is presented . The protein is made of one chain of 70 amino acid residues cross-linked by four disulfide bridges H-Lys-Lys-Asn-Gly-Tyr-Ala-Val-Asp-Ser-Ser-Gly-Lys-Ala-Pro-GluCys-Leu-Leu-Ser-Asn-Tyr-Cys-Asn-Asn-Gln-Cys-Thr-Lys-Val-HisTyr-Ala-Asp-Lys-Gly-Tyr-Cys-Cys-Leu-Leu-Ser-Cys-Tyr-Cys-PheGly-Leu-Asn-Asp-Asp-Lys-Lys-Val-Leu-Glu-Ile-Ser-Asp-Thr-ArgLys-Ser-Tyr-Cys-Asp-Thr-Thr-Ile-Ile-Asn-OH . Its C- terminal end is free contrary to that of mammal toxins that are generally C- amidated . One of the main feature is the shift of one half-cystine residue from position 12 to position 38 when comparing this insect toxin sequence to mammal toxins sequences (Rochst et al ., 1979) . The position of the disulfide bridges of AaH IT ~~s investigated using proteolysis of native and partially [ C]carboxymethylated protein . Determination of the amino acid compo sition of the cystine containüig peptides before or after performic oxydation, as also, when necessary, Edman degradation allowed to locate the four disulfide bonds in the toxin : they link respectively residues number 16 and 37, 22 and 42, 26 and 44, 38 and 64 . As it could be expected when comparing the sequences three amo~lg the four disulfide bonds are in homologous positions in insect and in mammal toxins (Kopeyan et al . 1974) . The fourth (38-64 or 12-63) is different that might give strong changes iii the protein conformation, which might well be important in the view of insect or mammal specificity of scorpion toxins . Acknowledgement : the authors are most grateful to Dr . Gérard Martüiez for his excellent assistance . Kopeyan, C ., Martüiez, G ., Lissitzky, S ., Miranda, F . and Rochat, H . (1974) Eur . J . Biochem ., 47, 483-489 ; Rochst, H ., Hernard, P . and Couraud, F . (1979) .Adv . in Cytopharmacology, 3, 325-333 ; Zlotkin, E ., Miranda, F, and Lissitzky, S . (1972a) Toxicon, 10, 211-216 ; Zlotkin, E ., Miranda, F . and Lissitzky, S . (1972b~Toxicon, 10, 207-210 ; Zlotkin, E ., Rochst, H ., Kopeyan, C ., Miranda, F. atid Lissitzky, S . (1971) Biochimie, 53, 1073-1078 ; Zlotkin, E ., Teitelbaum, Z ., Rochst, H . and Miranda, F . (1979) Insect Biochem ., 9, 347-354 . Oral Presentation

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