Structure of myotoxin II, a catalytically inactive Lys49 phospholipase A2 homologue from Atropoides nummifer venom

Lys49 snake-venom phospholipase A2 (PLA2) homologues are highly myotoxic proteins which, although lacking catalytic activity, possess the ability to disrupt biological membranes, inducing significant muscle-tissue loss and permanent disability in severely envenomed patients. Since the structural basis for their toxic activity is still only partially understood, the structure of myotoxin II, a monomeric Lys49 PLA2 homologue from Atropoides nummifer, has been determined at 2.08 Å resolution and the anion-binding site has been characterized. © 2006 International Union of Crystallography. All rights reserved.

Análise morfológica e histoquímica do corpo gorduroso e dos túbulos de Malpighi de operárias adultas de Scaptotrigona postica (Latreille, 1807) (Hymenoptera, Apidae) tratadas com fipronil e ácido bórico

Pós-graduação em Ciências Biológicas (Biologia Celular e Molecular) - IBRC

Avaliação do potencial tripanocida de substâncias extraídas da Família Piperaceae em formas epimastigotas de Trypanosoma cruzi

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Papel da mitocôndria na citoxicidade induzida pela abamectina em hepatócitos isolados de rato

Pós-graduação em Ciência Animal - FMVA

Análise da expressão gênica em isolados de Bacillus thuringiensis por PCR tempo real visando o controle de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) de diferentes populações brasileiras

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

Avaliação da atividade antiulcerogênica e tóxica dos estratos metanólicos e clorofórmico das folhas de Serjania erecta Radlk(Sapindaceae)

Pós-graduação em Biologia Geral e Aplicada - IBB

Peptídeos derivados da toxina bacteriana ParE: síntese, estrutura e ação inibitória sobre a atividade de topoisomerases

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mortalidade e efeitos subletais de Bacillus thuringiensis Berliner em Spodoptera albula (Walker, 1857)

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Caracterização do potencial inseticida e capacidade antioxidante de Spathodea campanulata (Bignoniaceae)

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

Oxygen supply in Bacillus thuringiensis fermentations: bringing new insights on their impact on sporulation and delta-endotoxin production

The growth kinetics, sporulation, and toxicity of Bacillus thuringiensis var. israelensis were evaluated through the analysis of batch cultures with different dissolved oxygen (DO) profiles. Firstly, DO was maintained constant at 5%, 20%, or 50% throughout fermentation in order to identify the most suitable one to improve the main process parameters. Higher biomass concentration, cell productivity, and cell yield based on glucose were obtained with 50% DO. The higher aeration level also resulted in higher spore counts and markedly improved the toxic activity of the fermentation broth, which was 9-fold greater than that obtained with 5% DO (LC50 of 39 and 329 mg/L, respectively). Subsequently, using a two-stage oxygen supply strategy, DO was kept at 50% during the vegetative and transition phases until the maximum cell concentration was achieved. Then, DO was changed to 0%, 5%, 20%, or 100% throughout sporulation and cell lysis phases. The interruption of oxygen supply strongly reduced the spore production and thoroughly repressed the toxin synthesis. On the contrary, when DO was raised to 100% of saturation, toxic activity increased approximately four times (LC50 of 8.2 mg/L) in comparison with the mean values reached with lower DO levels, even though spore counts were lower than that from the 50% DO assay. When pure oxygen was used instead of normal air, it was possible to obtain 70% of the total biomass concentration achieved in the air assays; however, cultures did not sporulate and the toxin synthesis was consequently suppressed.

The role of the C-terminal region of pulchellin A-chain in the interaction with membrane model systems

Pulchellin is a Ribosome Inactivating Protein containing an A-chain (PAC), whose toxic activity requires crossing the endoplasmic reticulum (ER) membrane. In this paper, we investigate the interaction between recombinant PAC (rPAC) and Langmuir monolayers of dipalmitoyl phosphatidyl glycerol (DPPG), which served as membrane model. Three catalytically active, truncated PACs with increasing deletion of the C-terminal region, possessing 244,239 and 236 residues (rPAC(244), rPAC(239) and rPAC(236)), were studied. rPAC had the strongest interaction with the DPPG monolayer, inducing a large expansion in its surface pressure-area isotherm. The affinity to DPPG decreased with increased deletion of the C-terminal region. When the C-terminal region was deleted completely (rPAC(236)), the interaction was recovered, probably because other hydrophobic regions were exposed to the membrane. Using Polarization Modulated-Infrared Reflection Absorption Spectroscopy (PM-IRRAS) we observed that at a bare air/water interface rPAC comprised mainly alpha-helix structures, the C-terminal region had unordered structures when interacting with DPPG. For rPAC(236) the alpha-helices were preserved even in the presence of DPPG. These results confirm the importance of the C-terminal region for PAC-ER membrane interaction. The partial unfolding only with preserved C-terminal appears a key step for the protein to reach the cytosol and develop its toxic activity. (C) 2011 Elsevier B.V. All rights reserved.

Identification of Trypanosoma brucei components involved in trypanolysis by normal human serum

Normal human serum (NHS) confers human resistance to infection by the parasite Trypanosoma brucei owing to the trypanolytic activity of apolipoprotein L1 (APOL1), present in two serum complexes termed Trypanolytic Factors (TLF-1 and -2). In order to identify parasite components involved in the intracellular trafficking and activity of TLFs, an inducible RNA interference (RNAi) genomic DNA library constructed in bloodstream form T. brucei was subjected to RNAi induction and selection for resistant parasites under NHS conditions favouring either TLF-1 or TLF-2 uptake. While TLF-1 conditions readily selected the haptoglobin-haemoglobin (HP-HB) surface receptor TbHpHbR as expected, given its known ability to bind TLF-1, under TLF-2 conditions no specific receptor for TLF-2 was identified. Instead, the screen allowed the identification of five distinct factors expected to be involved in the assembly of the vacuolar proton pump V-ATPase and consecutive endosomal acidification. These data confirm that lowering the pH during endocytosis is required for APOL1 toxic activity.

Actividad tóxica del aceite esencial de laurel y del cineol sobre Brevicoryne brassicae L. en repollo

El objetivo del presente trabajo fue estudiar la actividad tóxica del aceite esencial de laurel (Laurus nobilis L.) y del cineol, monoterpeno cíclico considerado un aleloquímico puro, sobre Brevicoryne brassicae L. en repollo (Brassica oleracea var. capitata L.). Las concentraciones de aceite esencial utilizadas fueron: 1; 1,5; 2 y 3%, y para cineol: 0,5; 1,5 y 2,5%, ambas formuladas en solución acuosa con 2% de oleato de polietilenglicol como emulsionante. Se utilizaron dos técnicas de aplicación: papeles impregnados y pulverización directa. A las 24 horas del tratamiento se evaluó el porcentaje de mortalidad. Los resultados se analizaron por ANOVA de dos vías y Test de Tukey. Se encontraron diferencias significativas para los productos evaluados en todas las concentraciones ensayadas. Las técnicas de aplicación no dieron diferencias significativas. La mayor mortalidad correspondió a 52% para el aceite esencial de laurel y 27,5% para cineol a las mayores concentraciones en ambos casos. Se concluye que los productos ensayados podrían ser una herramienta para el Manejo Integrado de Plagas para control de áfidos en cultivos hortícolas.

Synergistic action of actinoporin isoforms from the same sea anemone species assembled into functionally active heteropores

Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are pore forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families which give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here, using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other’s activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores since (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help to understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity.

Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here,using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other’s activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity.