Gene sequence analysis of toxins from the spider Phoneutria nigriventer revealed an intronless feature

spider venom contains several cysteine-rich peptide toxins that act on different ion channels. Despite extensive studies on its venom and description of cDNA sequences of several of its toxin precursors, the gene structure of these toxins remains unknown. Genomic regions encoding the precursors of three previously characterized toxins - PnTx1, PnTx2-5 and PnTx4(5-5) - were amplified by PCR using specific primers. PCR fragments were cloned and sequenced. Obtained sequences were compared with their corresponding cDNA sequences. The size of PCR fragments obtained and sequences corresponding to genomic regions encoding for the toxin precursors matched their cDNA sequences. Despite a few nucleotide substitutions in the genomic regions encoding for the toxin precursors when compared with cDNA sequences, the results of the present work indicate that toxins do not contain introns in their genes sequences.