Circular Dichroism of Elapidae Protein Toxins

Abstract

The effect of temperature variation on the circular dichroic spectra of 4 Elapid snake toxins (1 short neurotoxin, 2 long neurotoxins and 1 cytotoxin) was determined and the results compared. The 3 neurotoxins have in common a delicately balanced conformation which can be perturbed independently of the predominant secondary structuring. Despite the many differences in sequence between long and short neurotoxins, the nature of this balance may be the same in both types and is considered to involve an equilibrium between 2 defined conformers. Such properties could not be discerned in the cytotoxin studied, but related work suggests that they could nevertheless be present in some cases. In terms of global structure, long neurotoxins may have a greater proportion of random chain inherent than short neurotoxins, the latter having extensive .beta.-sheet. The important feature of all toxins is a conformational freedom defined by the secondary structuring and characteristic disulfide bridge formation. Possible relevance to toxicity of such a property is discussed.