A Neurotoxin, Toxin α, from Egyptian Cobra (Naja haje haje) Venom
1969; Elsevier BV; Volume: 244; Issue: 15 Linguagem: Inglês
10.1016/s0021-9258(17)36396-2
ISSN1083-351X
AutoresDawie P. Botes, Daniël J. Strydom,
Tópico(s)Healthcare and Venom Research
ResumoA neurotoxin, designated toxin α, has been isolated from the venom of the Egyptian cobra (Naja haje haje) by gradient chromatography on Amberlite CG-50, and has been further purified by gel filtration on Sephadex G-50. Homogeneity was verified by free boundary electrophoresis, acrylamide gel electrophoresis, sedimentation velocity, amino acid analysis, and end group analysis. Toxin α has a sedimentation constant, s020, w, of 1.18 S, a diffusion constant, D20, w of 14.07 × 10−7 cm2 sec−1, electrophoretic mobilities of 6.02 × 10−5, 2.94 × 10−5, and 2.84 × 10−5 cm2 sec−1 volt−1 at pH 5.0, 6.8, and 8.3, respectively, and a formula weight of 6834.6. Ultracentrifugation studies indicate that the reduced, S-carboxymethylated toxin is capable of dimer formation. Chemical studies show that toxin α is a small, basic protein consisting of a single polypeptide chain of 61 amino acid residues, cross-linked by four disulfide bridges. Alanine, methionine, and phenylalanine are totally absent. The complete amino acid sequence of the neurotoxin was determined by analyzing tryptic and chymotryptic peptides of the S-carboxymethyl derivative of the neurotoxin. Alignment with the partially determined structure of the probably homologous neurotoxin α from Naja nigricollis indicates eight amino acid differences between the two neurotoxins.
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