Cloning and characterization of cDNA sequences encoding for new venom peptides of the Brazilian scorpion Opisthacanthus cayaporum

Scorpion venom glands produce a large variety of bioactive peptides. This communication reports the identification of venom components obtained by sequencing clones isolated from a cDNA library prepared with venomous glands of the Brazilian scorpion Opisthacanthus cayaporum (Ischnuridae). Two main types of components were identified: peptides with toxin-like sequences and proteins involved in cellular processes. Using the expressed sequence tag (EST) strategy 118 clones were identified, from which 61 code for unique sequences (17 contigs and 44 singlets) with an average length of 531 base-pairs (bp). These results were compared with those previously obtained by the proteomic analysis of the same venom, showing a considerable degree of similarity in terms of the molecular masses expected and DNA sequences found. About 36% of the ESTs correspond to toxin-like peptides and proteins with identifiable open reading frames (ORFs). The cDNA sequencing results also show the presence of sequences whose putative products correspond to a scorpine-like component; three short antimicrobial peptides; three K+-channel blockers; and an additional peptide containing 78 amino acid residues, whose sequence resembles peptide La1 from another Ischnuridae scorpion Liocheles australiasiae, thus far with unknown function.