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 l ethal to house flies (LD50 80.0 ng/house fly). In contrast, Tb2-II was acti ve against both mammals (intracerebroventricular injection of 100 ng/mouse was lethal) and insects (LD50 40.0 ng/house fly). The amino-acid sequences of these toxins were established and found to be similar (60-95%) to previo usly described beta -toxins from the Tityus, genus. Based on the available comparative information, this study attempts identify possible structure-fu nction relationships that may be responsible for the differences in bioacti vity displayed by these toxins. (C) 2001 Published by Elsevier Science Ltd.