Interaction between DNA and viscotoxins

Journal/Book: Hoppe-Seyler's Z. Physiol. Chem. 361, 1535-1545. 1980;

Abstract: Cytotoxic viscotoxins I, II, III and IVb protect the native structure ofDNA against thermal denaturation. Viscotoxin IVb-DNA complexes, obtainedby direct mixing, were studied in detail by the techniques of thermaldenaturation of DNA and circular dichroism (CD). The binding ofviscotoxin IVb to DNA is principally ionic. This interaction results inDNA segments of different thermal stability, probably due to thecooperativity of the binding process. CD studies disclosed thatconformation of DNA remains unaltered upon complexing with viscotoxinIVb. The content of alpha-helical structure, appreciable in freeviscotoxin IVb, is reduced only slightly in the complexes with an excessof DNA and drastically at the polypeptide-DNA ratios close tosaturation. Stoichiometry at the saturation level has been estimated asapproximately one molecule of viscotoxin IVb per ten nucleotideresidues. The binding of heat-denatured, noncytotoxic viscotoxin IVb toDNA is random, in contrast to the native polypeptide, although theoverall stabilization of DNA-double helix is similar in both cases. Thepresented studies demonstrated that the cytotoxic viscotoxins bind toDNA and that viscotoxin IVb-DNA interaction has some common featureswith the interaction of various histones with DNA; however, therelevance of the interaction with DNA to the cytotoxic properties ofviscotoxins remains unknown. Author.

Keyword(s): ANIMAL

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