Snake toxin secondary structure predictions. Structure activity relationships

Modified Chou &; Fasman (1974a,b) secondary structure prediction rules have been successfully applied to the 57 snake venom toxins described as being neurotoxic or cytotoxic. Despite the different toxicities involved, a common distribution of secondary structure was detected throughout these toxins. The results also highlight the contrasts between short and long neurotoxins, and neurotoxins and cytotoxins. From comparisons of the typical structure of each toxin group with the known X-ray data an erabutoxin b and Philippines sea-snake toxin b, regions that dictate neurotoxicity or cytotoxicity can be tentatively identified. These deductions are discussed with regard to known chemical properties of these molecules. Similarly, the relevance of the differences between short and long neurotoxins to the superior binding of the latter to the cholinergic receptor is considered.It appears that the cytotoxins and neurotoxins are variations on a central toxic theme, but have differing specificities, whose origin can be traced to certain regions of the toxin in question.