979 resultados para Heterometrus xanthopus venom


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Cytochemistry studies of the nuclei of the venom glands' cells of worker bees of Apis mellifera indicated that there is a higher activity in the young workers while there is a predominance of degenerative characteristics in the older workers. In addition, we demonstrated that there is an occurrence of differential nuclear synthetic activities between the cells of the distal and the proximal regions of the secretory filament and of the venom reservoir. Signs of a higher nuclear activity were evidenced at the distal regions of this gland in 14-day old workers, while at the more proximal regions of the venom gland of 40-day old workers we identified the most obvious signs of degeneration. Therefore, it was evident that the process of glandular degeneration begins at the distal region of the venom gland instead of beginning at the proximal region as had been established previously. In addition, characteristics of nuclear synthetic activities were noted in the cells of the proximal region of the reservoir; these cells were thought to be non-secretory.

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Inflammatory peptides display different types of post-transcriptional modifications, such as C-terminal amidation, that alter their biological activity. Here we describe the structural and molecular dynamics features of the mast cell degranulating peptide, eumenine mastoparan-AF (EMP-AF-NH2), found in the venom of the solitary wasp, and of its carboxyl-free C-terminal form (EMP-AF-COO-) characterized by a reduced activity. Circular dichroism indicates that both peptides switch from a random coil conformation in water to a helical structure in TFE and SDS micelles. NMR data, in 30% TFE, reveal that the two peptides fold into an alpha-helix spanning most of their length, while they differ in terms of molecular rigidity. To understand the origins of the conformational flexibility observed in the case of EMP-AF-COO-, a 5 ns MD simulation was carried out for each peptide, in an explicit water/TFE environment. The results show that the two peptides differ in an H-bond between Leu14 NH2 and the backbone carbonyl of Ile11. The loss of that H-bond in EMP-AF-COO- leads to a significant modification of its structural dynamics. In fact, as evidenced by essential dynamics analysis, while EMP-AF-NH2 exists mainly as a rigid structure, EMP-AF-COO- presents two helical stretches that fluctuate in some sort of independent fashion. We conclude that the diverse biological activity of the two peptides is not simply due to the reduction of the net positive charge, as generally suggested, but also to a structural perturbation of the amphipathic alpha-helix that affects their ability to perturb the cell membrane.

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BaP1 is a metalloproteinase isolated from the venom of the Central American snake Bothrops asper (terciopelo). It is a 24 kDa protein consisting of a single chain which includes the metalloproteinase domain only, therefore being classified as a class P-I snake-venom metalloproteinase. BaP1 induces prominent local tissue damage, such as haemorrhage, myonecrosis, blistering, dermonecrosis and oedema. In order to elucidate its structure, BaP1 was crystallized by the hanging-drop vapour-diffusion technique in 0.1 M bicine pH 9.0, 10% PEG 20 000 and 2%(v/v) dioxane. Diffraction data were observed to a resolution of 2.7 Angstrom. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 38.22, b = 60.17, c = 86.09 Angstrom.

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Bothrombin, a snake-venom serine protease, specifically cleaves fibrinogen, releasing fibrinopeptide A to form non-crosslinked soft clots, aggregates platelets in the presence of exogeneous fibrinogen and activates blood coagulation factor VIII. Bothrombin shares high sequence homology with other snake-venom proteases such as batroxobin (94% identity), but only 30 and 34% identity with human alpha-thrombin and trypsin, respectively. Single crystals of bothrombin have been obtained and X-ray diffraction data have been collected at the Laboratorio Nacional de Luz Sincrotron to a resolution of 2.8 Angstrom. The crystals belong to the space group P2(1)2(1)2(1), with unit-cell parameters a = 94.81, b = 115.68, c = 155.97 Angstrom.

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A fibrinogen-clotting enzyme, Jararacussin-I, was purified from the venom of Bothrops jararacussu by a combination of ion exchange chromatography using Resource 15S resin and affinity chromatography using Benzamidine Sepharose 6B resin. Jararacussin-I displays a molecular mass of 28 kDa as estimated by sodium dodecyl sulphate-PAGE and possesses an isoetectric point of 5.0. The coagulant specific activity of the enzyme was determined to be 45.8 NIH U/mg using bovine fibrinogen as the substrate and the esterase specific activity was determined to be 258.7 U/mg. The protease inhibitors, benzamidine and DTT inhibited the esterase specific activity by 72.4 and 69.7%, respectively. The optimal temperature and pH for the degradation of both chains of fibrinogen and esterase specific activity were determined to be 37 degreesC and 7.4-8.0, respectively. The enzyme was inactivated at both 4 and 75 T. Single crystals of Jararacussin-I were obtained and complete three-dimensional X-ray diffraction data was collected at the Brazilian National Synchrotron Source (LNLS) to a resolution of 2.4 Angstrom. (C) 2002 Published by Elsevier B.V. Ltd.

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Convulxin, an alphabeta C-type lectin, is a potent platelet activator isolated from the venom of the South American rattlesnake Crotalus durissus terrificus. It is a 26.5 kDa alphabeta heterodimer consisting of two homologous disulfide-linked chains. The crystals belong to space group I4, with unit-cell parameters a = b = 131.61, c = 121.85 Angstrom, and diffraction data were collected to 2.7 Angstrom. The structure was solved by molecular replacement and the asymmetric unit contains two alphabeta heterodimers, each of which forms a disulfide-linked cyclic alpha(4)beta(4) tetramer in the unit cell. These alpha(4)beta(4) tetramers are stacked to form a large solvent channel.