Crystal structure of a myotoxic Asp49-phospholipase A(2) with low catalytic activity: Insights into Ca2+ -independent catalytic mechanism

A myotoxic Asp49-phospholipase A(2) (Asp49-PLA(2)) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) was crystallized and the molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxic Asp49-PLA2 PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA(2)s. Despite of this, BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA(2) from B. jararacussu) and other Asp49-PLA(2)s. BthTX-II structure showed a severe distortion of calcium-binding loop leading to displacement of the C-terminal region. Tyr28 side chain, present in this region, is in an opposite position in relation to the same residue in the catalytic activity Asp49-PLA(2)s, making a hydrogen bond with the atom 0 delta 2 of the catalytically active Asp49, which should coordinate the calcium. This high distortion may also be confirmed by the inability of BthTX-II to bind Na+ ions at the Ca2+-binding loop, despite of the crystallization to have occurred in the presence of this ion. In contrast, other Asp49-PLA(2)s which are able to bind Ca2+ ions are also able to bind Na+ ions at this loop. The comparison with other catalytic, non-catalytic and inhibited PLA(2)s indicates that the BthTX-II is not able to bind calcium ions; consequently, we suggest that its low catalytic function is based on an alternative way compared with other PLA(2)s. (c) 2008 Elsevier B.V All rights reserved.

Crystal structure of a phospholipase A(2) homolog complexed with p-bromophenacyl bromide reveals important structural changes associated with the inhibition of myotoxic activity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The Intriguing Phospholipases A(2) Homologues: Relevant Structural Features on Myotoxicity and Catalytic Inactivity

Phospholipases A(2) homologues are found in the venom of Crotalinae snakes, being their main action related to myonecrosis induction. Although many studies on these toxins had already been performed, their mechanism of action remains unclear. Here, important aspects about these toxins are reviewed, including their correct biological assembly and how essential is the natural substitution D49K for their catalytic inactivity.

Crystallization and preliminary X-ray diffraction analysis of a Lys49-phospholipase A(2) complexed with caffeic acid, a molecule with inhibitory properties against snake venoms

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative study on extracts from the tissue covering the stingers of freshwater (Potamotrygon falkneri) and marine (Dasyatis guttata) stingrays

Stingrays are elasmobranchs found along the seacoast and in some rivers of Brazil. Pain is the most conspicuous symptom observed in patients wounded by the bilaterally retroserrate stingers located in the tail, which are covered by glandular and integument tissues. In addition, cutaneous necrosis is commonly observed in injuries caused by freshwater stingrays. The aim of this work was to characterize and compare certain properties of tissue extracts obtained from the glandular tissues covering the stinger apparatus of Potamotrygon falkneri and Dasyatis guttata stingrays. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), tissue extracts have similar bands above 80kDa, but most differences were observed below this molecular mass. Lethal, dermonecrotic and myotoxic activities were detected only in P. falkneri tissue extract. Edematogenic activity was similar and dose dependent in both tissue extracts. Nociceptive activity was verified in both tissue extracts, but P. falkneri presented a two-fold higher activity than D. guttata tissue extract. No direct hemolysis, phospholipase A(2) and coagulant activities were observed in both tissue extracts. Antigenic cross-reactivity was noticed by ELISA and Western blotting, using antisera raised in rabbits. Species-specific sera reacted with several components of both tissue extracts, noticeably above 22 kDa. Both tissue extracts presented gelatinolytic, caseinolytic and fibrinogenolytic activities, which were not caused by the action of metalloproteinases. Hyaluronidase activity was detected only in P. falkneri tissue extract. Our experimental observations suggest that P. falkneri tissue extract is more toxic than D. guttata tissue extract. These results may explain why injuries caused by freshwater stingrays are more severe in human accidents. (c) 2007 Elsevier Ltd. All rights reserved.

Expression and processing of recombinant sarafotoxins precursor in Pichia pastoris

Sarafotoxins are peptides isolated from the Atractaspisw snake venom. with strong constrictor effect on cardiac and smooth muscle. They are structurally and functionally related to endothelins. The sarafotoxins precursor cDNA predicts an unusual structure 'rosary-type', with 12 successive similar stretches of sarafotoxin (SRTX) and spacer, in the present work, the recombinant precursor of SRTXs was sub-cloned and expressed in the yeast Pichia pastoris. and secreted to the culture medium, Characterization by SDS-PAGE, immunoblot, mass spectrometry and biological activity, suggests that intact precursor was expressed but processing into mature toxins also occurred. Furthermore, our results indicate that the correct proportion of sarafotoxin types as contained in the precursor, is obtained in the yeast culture medium. Contractile effects of the expressed toxins, on rat and Bothrops jararaca isolated aorta, were equivalent to 5 X 10(-10) M and 5 x 10(-11) M of sarafotoxin b, respectively. The enzymes responsible for the complete maturation of sarafotoxins precursor are still unknown. Our results strongly suggest that the yeast Pichia pastoris is able to perform such a maturation process. Thus, the yeast Pichia pastoris may offer an alternative to snake venom gland to tentatively identify the molecular process responsible for SRTXs release. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Análise morfológica da glândula de veneno de Apis mellifera L. (Hymenoptera: Apidae) em populações de Mato Grosso do Sul

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inflammation and apoptosis induced by mastoparan Polybia-MPII on skeletal muscle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A new scenario of bioprospecting of Hymenoptera venoms through proteomic approach

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mastoparan effects in skeletal muscle damage: An ultrastructural view until now concealed

Animal venoms have been valuable sources for development of new drugs and important tools to understand cellular functioning in health and disease. The venom of Polybia paulista, a neotropical social wasp belonging to the subfamily Polistinae, has been sampled by headspace solid phase microextraction and analyzed by gas chromatography-mass spectrometry. Recent study has shown that mastoparan, a major basic peptide isolated from the venom, reproduces the myotoxic effect of the whole venom. In this study, Polybia-MPII mastoparan was synthesized and studies using transmission electron microscopy were carried out in mice tibial anterior muscle to identify the subcellular targets of its myotoxic action. The effects were followed at 3 and 24 h, 3, 7, and 21 days after mastoparan (0.25 mu g/mu L) intramuscular injection. The peptide caused disruption of the sarcolemma and collapse of myofibril arrangement in myofibers. As a consequence, fibers presented heteromorphic amorphous masses of agglutinated myofilaments very often intermingled with denuded sarcoplasmic areas sometimes only surrounded by a persistent basal lamina. To a lesser extent, a number of fibers apparently did not present sarcolemma rupture but instead appeared with multiple small vacuoles. The results showed that sarcolemma, sarcoplasmic reticulum (SR), and mitochondria were the main targets for mastoparan. In addition, a number of fibers showed apoptotic-like nuclei suggesting that the peptide causes death both by necrosis and apoptosis. This study presents a hitherto unexplored view of the effects of mastoparan in skeletal muscle and contributes to discuss how the known pharmacology of the peptide is reflected in the sarcolemma, SR, mitochondria, and nucleus of muscle fibers, apparently its subcellular targets.

The neurotoxicological effects of mastoparan Polybia-MPII at the murine neuromuscular junction: an ultrastructural and immunocytochemical study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Rapid configuration analysis of the solenopsins

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The chelation of metal ions by the acylpolyamine toxins from the web-spider Nephilengys cruentata: effects in the intoxication/detoxification of preys

Orb-web-spiders present a series of different strategies for prey capture, involving the use of different types of silk for web building, the use of adhesive traps in the webs, the secretion of toxic compounds to the spider's preys in the adhesive coating of the capture web and the biosynthesis of a wide range of structurally related acylpolyamine toxins in their venoms. The polyamine toxins usually block neuromuscular junctions and/or the central nervous system (CNS) of Arthropods, targeting specially the ionotropic glutamate receptors; this way these toxins are used are as chemical weapons to kill / paralyze the spider's prey. Polyamine toxins contain many azamethylene groups involved with the chelation of metal ions, which in turn can interact with the glutamate receptors, affecting the toxicity of these toxins. It was demonstrated that the chelation of Ni+2, Fe+2, Pb+2, Ca+2 and Mg+2 ions by the desalted crude venom of Nephilengys cruentata and by the synthetic toxin JSTX-3, did not cause any significant change in the toxicity of the acylpolyamine toxins to the model-prey insect (honeybees). However, it was also reported that the chelation of Zn+2 ions by the acylpolyamines potentiated the lethal / paralytic action of these toxins to the honeybees, while the chelation of Cu+2 ions caused the inverse effect. Atomic absorption spectrometry and Plasma-ICP analysis both of N.cruentata venom and honeybee's hemolymph revealed that the spider's venom concentrates Zn+2 ions, while the honeybee's hemolymph concentrates Cu+2 ions. These results are suggesting that the natural accumulation of Zn+2 ions in N. cruentata venom favors the prey catching and/or its maintenance in the web, while the natural accumulation of Cu+2 ions in prey's hemolymph minimizes the efficiency of the acylpolyamine toxins as killing/paralyzing tool.

Influence of Prey Size on the Predatory Behavior of Ectatomma brunneum (Hymenoptera: Formicidae) Under Laboratory Conditions

The influence of prey size on the predatory behavior and behavioral sequence of Ectatomma brunneum under laboratory conditions was evaluated. Two behaviors were characterized: rejection and attack, the latter divided into individual and group attack. In the group attack, prey transport (Tenebrio molitor larvae) into the nest prevailed, whether immobilized as a consequence of the ant venom or not. on the other hand, in the individual attacks such behavior was not observed. There was no significant relation between the predatory behavior and the size of the larvae offered, indicating that prey dimensions do not interfere with predation. The high rejection rates registered in the experimental trials may have been a consequence of the absence of immatures in the nests used in the research and/or the decrease in the activities observed, considering that the experiments were carried out in the coldest time of the year.

The effect of acidic residues and amphipathicity on the lytic activities of mastoparan peptides studied by fluorescence and CD spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)