title: The oxidation of methionine and its effect of the properties of cardiotoxin VII1 from Naja melanoleuca venom.
abstract: Methionine residues 24 and 26 of cardiotoxin VII1 from Naja melanoleuca were oxidised to sulphoxides using N-chlorosuccinimide at pH 8.5. The number of equivalents of oxidant required for complete oxidation suggested that the methionine side-chains existed in a relatively "exposed" conformational state in cardiotoxin. The oxidised cardiotoxin was devoid of lethality. It was also non-haemolytic, both on its own and in the presence of phospholipase A2. However, it was still able to precipitate with anti-cardiotoxin antibody. CD studies indicated that the polypeptide backbone conformation was intact in the oxidised cardiotoxin but some perturbation of tyrosine residues was evident. The possibility of a direct or indirect involvement of the methionine residues in the biological activity of the cardiotoxin is discussed.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002942:Circular Dichroism; D004220:Disulfides; D004546:Elapid Venoms; D006321:Heart / Q000187:drug effects; D006461:Hemolysis; D005779:Immunodiffusion; D008715:Methionine; D010740:Phospholipases / Q000378:metabolism; D011487:Protein Conformation; D013388:Succinimides
chemical_list: D000596:Amino Acids; D004220:Disulfides; D004546:Elapid Venoms; D013388:Succinimides; C015752:N-chlorosuccinimide; D008715:Methionine; D010740:Phospholipases