Purification, amino-acid sequence and partial characterization of two toxins with anti-insect activity from the venom of the South American scorpion Tityus bahiensis (Buthidae).

We report here the isolation by a two-step chromatographic procedure of two new toxins from the South American scorpion Tityus bahiensis. Their amino-acid sequences and some of their biological features were established. The two toxins have different biological properties. Toxin TbIT-I had almost no activity or pharmacological effects in vertebrate tissues whereas it was lethal to house ?ies (LD50 80.0 ng/house ?y). In contrast, Tb2-II was active against both mammals (intracerebroventricular injection of 100 ng/mouse was lethal) and insects (LD50 40.0 ng/house ?y). The amino-acid sequences of these toxins were established and found to be similar (60?95%) to previously described b-toxins from the Tityus genus. Based on the available comparative information, this study attempts identify possible structure?function relationships that may be responsible for the differences in bioactivity displayed by these toxins