PITVIPERS OF CAATINGA: STRUCTURAL AND FUNCTIONAL ASPECTS OF THEIR TOXINS

GUARNIERI M.C.(1), DE ALBUQUERQUE-MODESTO J.C.(2), RÁDIS-BAPTISTA G. (3)

(1) Department of Zoology, Federal University of Pernambuco (UFPE), Brazil;  (2) Nucleus of Biology, Academic Center of Vitória, UFPE, Brazil; (3) Department of Biochemistry and Laboratory of Immunopathology Keizo Asami,  UFPE. Brazil.

In Brazil, there are 27 species of snakes belonging to Viperidae family, of which six are found in Caatinga.This biome, with an area of approximatelly 800.000 km² and 10% of all Brazilian territory, encompasses seven states (CE, RN, PB, PE, SE, AL, BA, part of PI and MG).The Caatinga presents a semi-arid climate, with a period of irregular rain, xerophytic and decidous vegetation, as well as a  particular biodiversity. In the state of Pernambuco, the Viperidae species found in Caatinga are Bothriopsis bilineata, Bothrops neuwiedi, B. leucurus, B. erythromelas and Crotalus durissus cascavella.  These two latter are the main responsible for envenomation in Pernambuco. Our group has particularly dedicated to the investigation of  B. erythromelas and C. d. cascavella venom, by purification, characterization and molecular cloning of their toxins. Recently, we have isolated and cloned a novel acidic Asp49 phospholipase A2 from B. erythromelas, with a MW of 13,649.57 Da, as estimated by mass spectrometry (MALDI-ToF). The complete BE-I-PLA2 cDNA possesses 457 bp and encodes a protein with significant sequence similarity to many other snake venom phospholipases A2. When tested in platelet rich plasma, the enzyme showed a potent inhibitory effect on aggregation induced by arachidonic acid and collagen, but not ADP.  Moreover, BE-I-PLA2 stimulated endothelial cells to release prostaglandin I2, suggesting an increase of its potential anti-platelet activity in vivo. For now, we are determining the exact mechanism of action of BE-I-PLA2 in the inhibition of platelet aggregation, and characterizing a new isoform of this PLA2. In other study, from C. d. cascavella venom gland, we have cloned several cDNA precursors of convulxin (CVX) subunit homologs. One of them, it was named crotacetin (CTC) beta-subunit and it predicts a polypeptide with a tridimensional topology very similar to other subunits of CVX-like snake toxins. Crotacetin was further purified from the venom of several C. durissus, but it is quantitative predominant in the venom of C. durissus cascavella. Functional analysis indicates that CTC induces platelet aggregation, and, importantly, exhibits an antimicrobial activity against Gram-positive and -negative bacteria, comparable with CVX. Our ongoing projects include the purification and cloning of hemorragic and factor X activator metalloproteases, neurotoxic PLA2s, and C-type lectins from B. leucurus and  C. d. Cascavella venoms.

KEY WORDS: PLA2, C-type lectin, Bothrops, Crotalus, platelets, snake toxin.

CORRESPONDENCE TO: Rua Nestor Chaves, s/n, Cidade Universitária, Recife-PE, CEP: 52.011-330. E-mail: mcg@ufpe.br

FINANCIAL SUPPORT: CAPES, CNPq, FAPESP.