Raman spectrum of toxin B in relation to structure and toxicity

Abstract

There are two types of neurotoxic proteins in the venoms of Elapidae and Hydrophiidae snakes. They are the short-chain neurotoxins (type I toxins) consisting of 60-62 amino acid residues with four disulfide bridges and the long-chain neurotoxins (type II toxins) consisting of 7 1-74 amino acid residues with five disulfide bridges [l] . Laticauda semifasciata III (Is III) is the only one exceptional neurotoxin so far identified that does not belong to either type [2,3]. The shortchain and long-chain toxins have similar neurotoxicity [4]. However, the differences distinguished between them in the effects of chemical modifications on the toxicity [5,6] suggest some difference in the role of the essential amino acids for neurotoxicity. In the preceding paper, Harada et al. reported the Raman spectra of the short-chain neurotoxins, erabutoxins a and b (Ea and Eb), the denatured toxins, and the weakly neurotoxic Is III, and discussed on the structure-toxicity relationships [7]. Toxin B is a long-chain neurotoxin from the venom of the Indian cobra, Naja naja, and 71 amino acid sequence and the position of the five disulfide bridges have been determined [8], In the present paper, the Raman spectrum of toxin B is reported and the structure-toxicity relationships are discussed in comparison with the former results on the short-chain toxins [7,9].