SEQUENCE OF THE CDNA CODING FOR THE LETHAL NEUROTOXIN TX1 FROM THE BRAZILIAN ARMED SPIDER PHONEUTRIA-NIGRIVENTER PREDICTS THE SYNTHESIS ANDPROCESSING OF A PREPROTOXIN

A cDNA library was constructed from the venom glands of the Brazilian ''armed'' spider, Phoneutria nigriventer, and a clone coding for Tx1, a lethal toxin, was identified and sequenced. The sequence data derive d from this cDNA clone combined with the previously determined amino a cid sequence predict that Tx1 is initially synthesized as a preprotoxi n. Four segments (comprising the signal sequence, a short, 15-amino ac id, glutamate-rich sequence, the functional toxin, and 2 glycine resid ues) can be distinguished. The structure of the preprotoxin and the pr oposed processing steps required to form the mature Tx1 toxin show sim ilarities with the synthesis and processing of omega-agatoxin IA.