ATRACTASPIS - MINI REVIEW 



95 



Fig. 8 Elongated venom glands of Atractaspis engaddensis: V = venom gland. 



Fig. 9 Venom extraction from Atractaspis engaddensis using a piece of 

 tubing for safety and a parafilm-covered lid for the collection of venom. 



a high degree of structural homology amongst themselves and with 

 a group of active peptides that were isolated from mammalian 

 endothelium, the endothelins (Fig. 10). The sarafotoxins and 

 endothelins are also similar in their pharmacological activity and are 



15 10 



composed of 21 amino acid residues, with two disulphide bridges 

 between Cys 1-15 and 3-1 1 (Yanagisawa et at., 1988; Takasaki et 

 al., 1988; Wollberg et al.. 1990; Kochva et al, 1993). Another 

 member of the sarafotoxin/endothelin family, bibrotoxin, was iso- 

 lated from the venom of A. bibroni. It differs from SRTX-b in only 

 one amino acid substitution and induces vasoconstriction in rat aorta 

 (Becker et al.. 1993). The venom of A. m. microlepidota contains a 

 series of peptides with a somewhat higher molecular weight that are 

 composed of 24 amino acids (Ducancel et al, 1999) and are 

 apparently less toxic than SRTX-a or b. 



The sarafotoxins and endothelins are now synthesised by pharma- 

 ceutical companies and are widely used in both basic and applied 

 research, both clinical and industrial, in the field of cardiology and 

 in blood pressure studies (Ducancel et al., 1999: Yaakov et al., 

 2000). 



The various sarafotoxins (and endothelins) differ in their activity 

 and toxicity, the most potent ones being SRTX-a and SRTX-b 

 (Table 1 ). which exert a strong influence on the cardiovascular 

 system (Wollberg et al.. 1988). SRTX-b shows three, apparently 

 separate, effects on the heart: 1 ) positive inotropicity, which is 

 manifested by an increased contractility in isolated hearts and heart 

 muscles and in in vivo injected mice with sublethal doses of the 



15 20 



Cys-Ser-Cys-Lys-Asp-Met-Thr-Asp-Lys-Glu-Cys-Leu-Asn-Phe-Cys-His-Gln-Asp-Val-Ile-Trp 



Cys 

 Cys 

 Cys 

 Cys 



Cys * 

 Cys * 

 Cys * 

 Cys -Ala 



Ser 



Ser 



Cys-Thr-Cys-Asn * * * 

 Cys-Thr-Cys * * * * 

 Cys * Cys-Asn * Ile-Asn 

 Cys * Cys-Ser-Ser-Leu-Met 

 Cys * Cys-Ser-Ser-Trp-Leu 

 Cys * Cys-Asn-Ser-Trp-Leu 

 Cys-Thr-Cys-Phe-Thr-Tyr- Lys 

 Cys * Cys-Ala-Thr-Phe-Leu 

 1 5 



Glu 



Tyr 



Tyr 



Tyr 



* 



Tyr 



Cys 



Cys 



Cys 



Cys 



Cys 



Cys 



Cys Met Tyr 



Cys-Val-Tyr 



Cys-Val-Tyr 



Cys-Val-Tyr 



Cys-Val-Tyr- 



Cys-Val-Tyr 



10 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 



* Cys 

 Tyr-Cys 



* Cys 



15 



* Gly-Ile 



* * * 



Leu 

 Leu 

 Leu 

 Leu 

 Leu 



He 

 He 

 He 

 He 

 He 



SRTX-a 



* SRTX-al 



* SRTX-b 



* SRTX-bl 



* BTX 



* SRTX-c 



* SRTX-d/e 



* Asp-Glu-Pro A. microlepidota 



* ET-1 



* ET-2 



* VIC 



* ET-3 



* ET-trout (1999) 



20 



Fig. 10 Amino acid sequences of sarafotoxins and endothelins: BTX = bibrotoxin. ET = endothelin, SRTX = sarafotoxin. VIC = vasoactive intestinal 

 contractor. 



