Conformational prediction for snake venom toxins and laser Raman scattering of a cardiotoxin from Taiwan cobra (Naja naja atra) venom.

Secondary structure regions in snake venom toxins were predicted using the prediction method of Chou and Fasman (Chou, P. Y., and Fasman, G. D. (1974), biochemistry 13,222) and an averaging scheme assuming structural homology in each type of toxins. The results indicate that, in general, snake toxins contain only some beta-sheet regions and beta bends. The content of secondary structures thus predicted does vary to some extent. The predicted results correlate well with conclusions from physicochemical studies. Interestingly, beta-bend regions predicted for the two types of neurotoxins, short-neurotoxin-type and long-neurotoxin-type, are primarily located in the middle of disulfide loops in spite of large differences in primary sequences. Comparisons between predicted results and the crystal structure of erabutoxin b determined at 2.75 A resolution suggest that the two types of neurotoxin are both sequencely and conformationally related while cardiotoxins could have an entirely different molecular topology. The Raman spectrum of a Taiwan cobra cardiotoxin indicates that the content of beta-pleated-sheet structure could be greater than that in neurotoxins.