Amino acid sequence and three-dimensional structure of the Tn-specific isolectin B4 from Vicia villosa

International audienceThe partial amino acid sequence of the tetrameric isolectin B4 from Vicia villosa seeds has been determined by peptide analysis, and its three-dimensional structure solved by molecular replacement techniques and refined at 2.9 A resolution to a crystallographic R-factor of 21%. Each subunit displays the thirteen-stranded beta-barrel topology characteristic of legume lectins. The amino acid residues involved in metal- and sugar-binding are similar to those of other GalNAc-specific lectins, indicating that residues outside the carbohydrate-binding pocket modulate the affinity for the Tn glycopeptide. Isolectin B4 displays an unusual quaternary structure, probably due to protein glycosylation

Trypanosoma cruzi chemical proteomics using immobilized benznidazole

Benznidazole (Bzn) is a nitroimidazole drug currently used as first line treatment against Chagas disease, a neglected tropical disease caused by the flagellated protozoan Trypanosoma cruzi. Although the drug has been used since the late 1960s, its mechanism of action is not fully understood. In an attempt to study Bzn mode of action, a structurally modified derivative of the drug was synthesized and immobilized into a solid matrix. This allowed enrichment of T. cruzi proteins capable of binding immobilized Bzn, which were subsequently analysed by mass spectrometry. The proteins identified as specific non-covalent Bzn interactors were a homologue of the bacterial YjeF proteins, a Sec23A orthologue and the aldo–ketoreductase family member TcAKR. TcAKR is closely related to other enzymes previously associated with Bzn reductive activation such as NTRI and TcOYE. Thus, our untargeted search for Bzn binding partners allowed us to encounter proteins that could be related to drug reductive activation and/or resistance mechanisms.Fil: Trochine, Andrea. Instituto Pasteur de Montevideo. Unidad de Biologia Molecular; Uruguay. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Alvarez, Guzmán. Universidad de la República. Facultad de Ciencias; UruguayFil: Corre, Sandra. Instituto Pasteur de Montevideo. Unidad de Biologia Molecular; UruguayFil: Faral Tello, Paula. Instituto Pasteur de Montevideo. Unidad de Biologia Molecular; UruguayFil: Durán, Rosario. Instituto Pasteur de Montevideo; UruguayFil: Batthyany, Carlos I.. Instituto Pasteur de Montevideo; Uruguay. Instituto de Investigaciones Biologicas "Clemente Estable"; UruguayFil: Cerecetto, Hugo. Universidad de la República. Facultad de Ciencias; Uruguay. Instituto de Investigaciones Biologicas "Clemente Estable"; UruguayFil: Gonzalez, Mercedes. Universidad de la República. Facultad de Ciencias; UruguayFil: Robello, Carlos. Instituto Pasteur de Montevideo. Unidad de Biologia Molecular; Uruguay. Universidad de la Republica; Urugua

Exposing the Secrets of Two Well-Known Lactobacillus casei Phages, J-1 and PL-1, by Genomic and Structural Analysis

Bacteriophage J-1 was isolated in 1965 from an abnormal fermentation of Yakult using Lactobacillus casei strain Shirota, and a related phage, PL-1, was subsequently recovered from a strain resistant to J-1. Complete genome sequencing shows that J-1 and PL-1 are almost identical, but PL-1 has a deletion of 1.9 kbp relative to J-1, resulting in the loss of four predicted gene products involved in immunity regulation. The structural proteins were identified by mass spectrometry analysis. Similarly to phage A2, two capsid proteins are generated by a translational frameshift and undergo proteolytic processing. The structure of gene product 16 (gp16), a putative tail protein, was modeled based on the crystal structure of baseplate distal tail proteins (Dit) that form the baseplate hub in other Siphoviridae. However, two regions of the C terminus of gp16 could not be modeled using this template. The first region accounts for the differences between J-1 and PL-1 gp16 and showed sequence similarity to carbohydrate-binding modules (CBMs). J-1 and PL-1 GFP-gp16 fusions bind specifically to Lactobacillus casei/paracasei cells, and the addition of L-rhamnose inhibits binding. J-1 gp16 exhibited a higher affinity than PL-1 gp16 for cell walls of L. casei ATCC 27139 in phage adsorption inhibition assays, in agreement with differential adsorption kinetics observed for both phages in this strain. The data presented here provide insights into how Lactobacillus phages interact with their hosts at the first steps of infection.Fil: Dieterle, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. University of Pittsburgh; Estados UnidosFil: Bowman, Charles. University of Pittsburgh; Estados UnidosFil: Batthyany, Carlos. Instituto Pasteur de Montevideo; UruguayFil: Lanzarotti, Esteban Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Turjanski, Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Hatfull, Graham. University of Pittsburgh; Estados UnidosFil: Piuri, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Peanut seed cultivars with contrasting resistance to Aspergillus parasiticus colonization display differential temporal response of protease inhibitors

Significant efforts are being made to minimize aflatoxin contamination in peanut seeds and one possible strategy is to understand and exploit the mechanisms of plant defense against fungal infection. In this study we have identified and characterized, at biochemical and molecular levels, plant protease inhibitors (PPIs) produced in peanut seeds of the resistant PI 337394 and the susceptible Forman cultivar during Aspergillus parasiticus colonization. With chromatographic methods and 2D-electrophoresis-mass spectrometry we have isolated and identified four variants of Bowman-Birk trypsin inhibitor (BBTI) and a novel Kunitz-type protease inhibitor (KPI) produced in response to A. parasiticus colonization. KPI was detected only in the resistant cultivar, while BBTI was produced in the resistant cultivar in a higher concentration than susceptible cultivar and with different isoforms. The kinetic expression of KPI and BBTI genes along with trypsin inhibitory activity was analyzed in both cultivars during infection. In the susceptible cultivar an early PPI activity response was associated with BBTI occurrence. Meanwhile, in the resistant cultivar a later response with a larger increase in PPI activity was associated with BBTI and KPI occurrence. The biological significance of PPI in seed defense against fungal infection was analyzed and linked to inhibitory properties on enzymes released by the fungus during infection, and to the antifungal effect of KPI.Fil: Müller, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: Bonacci, Gustavo Roberto. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: Batthyany, Carlos. Institut Pasteur de Montevideo; UruguayFil: Amé, María Valeria. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: Carrari, Fernando Oscar. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; ArgentinaFil: Gieco, Jorge. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Asis, Ramón. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; Argentin

Characterisation of the native lipid moiety of Echinococcus granulosus antigen B.

Antigen B (EgAgB) is the most abundant and immunogenic antigen produced by the larval stage (metacestode) of Echinococcus granulosus. It is a lipoprotein, the structure and function of which have not been completely elucidated. EgAgB apolipoprotein components have been well characterised; they share homology with a group of hydrophobic ligand binding proteins (HLBPs) present exclusively in cestode organisms, and consist of different isoforms of 8-kDa proteins encoded by a polymorphic multigene family comprising five subfamilies (EgAgB1 to EgAgB5). In vitro studies have shown that EgAgB apolipoproteins are capable of binding fatty acids. However, the identity of the native lipid components of EgAgB remains unknown. The present work was aimed at characterising the lipid ligands bound to EgAgB in vivo. EgAgB was purified to homogeneity from hydatid cyst fluid and its lipid fraction was extracted using chloroform∶methanol mixtures. This fraction constituted approximately 40-50% of EgAgB total mass. High-performance thin layer chromatography revealed that the native lipid moiety of EgAgB consists of a variety of neutral (mainly triacylglycerides, sterols and sterol esters) and polar (mainly phosphatidylcholine) lipids. Gas-liquid chromatography analysis showed that 16∶0, 18∶0 and 18∶1(n-9) are the most abundant fatty acids in EgAgB. Furthermore, size exclusion chromatography coupled to light scattering demonstrated that EgAgB comprises a population of particles heterogeneous in size, with an average molecular mass of 229 kDa. Our results provide the first direct evidence of the nature of the hydrophobic ligands bound to EgAgB in vivo and indicate that the structure and composition of EgAgB lipoprotein particles are more complex than previously thought, resembling high density plasma lipoproteins. Results are discussed considering what is known on lipid metabolism in cestodes, and taken into account the Echinococcus spp. genomic information regarding both lipid metabolism and the EgAgB gene family

Mechanism of the Reaction of Human Manganese Superoxide Dismutase with Peroxynitrite: Nitration of Critical Tyrosine 34

Human Mn-containing superoxide dismutase (hMnSOD) is amitochondrial enzyme that metabolizes superoxide radical (O2?−). O2?− reacts atdiffusional rates with nitric oxide to yield a potent nitrating species, peroxynitriteanion (ONOO−). MnSOD is nitrated and inactivated in vivo, with active siteTyr34 as the key oxidatively modified residue. We previously reported a k of ∼1.0× 105 M−1 s−1 for the reaction of hMnSOD with ONOO− by direct stopped-flowspectroscopy and the critical role of Mn in the nitration process. In this study, wefurther established the mechanism of the reaction of hMnSOD with ONOO−,including the necessary re-examination of the second-order rate constant by anindependent method and the delineation of the microscopic steps that lead to theregio-specific nitration of Tyr34. The redetermination of k was performed bycompetition kinetics utilizing coumarin boronic acid, which reacts with ONOO−at a rate of ∼1 × 106 M−1 s−1 to yield the fluorescence product, 7-hydroxycoumarin. Time-resolved fluorescence studies in the presence of increasing concentrations of hMnSOD provided a kof ∼1.0 × 105 M−1 s−1, fully consistent with the direct method. Proteomic analysis indicated that ONOO−, but not othernitrating agents, mediates the selective modification of active site Tyr34. Hybrid quantum-classical (quantum mechanics/molecular mechanics) simulations supported a series of steps that involve the initial reaction of ONOO− with MnIII to yield MnIVand intermediates that ultimately culminate in 3-nitroTyr34. The data reported herein provide a kinetic and mechanistic basis forrationalizing how MnSOD constitutes an intramitochondrial target for ONOO− and the microscopic events, with atomic levelresolution, that lead to selective and efficient nitration of critical Tyr34.Fil: Demicheli, Verónica. Universidad de la República; UruguayFil: Moreno, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Jara, Gabriel Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Lima, Analía. Instituto Pasteur de Montevideo; UruguayFil: Carballal, Sebastián. Universidad de la República; UruguayFil: Ríos, Natalia. Universidad de la República; UruguayFil: Batthyany, Carlos. Universidad de la República; Uruguay. Instituto Pasteur de Montevideo; UruguayFil: Ferrer Sueta, Gerardo. Universidad de la República; UruguayFil: Quijano, Celia. Universidad de la República; UruguayFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Radi, Rafael. Universidad de la República; Urugua

The lipid fractions of EgAgB and HCF are similar and include a variety of neutral and polar lipids.

<p>The lipid fractions of bovine EgAgB and its corresponding HCF were analysed by HPTLC using double development (A) or in conditions for resolving separately neutral (B) and polar (C) lipid classes. Standards (between 2 and 8 µg) and samples (around 5 and 10 µg) were applied onto HPTLC plates; 1-nonadecanol was added as internal standard (IS) for normalization purposes. Lipid bands were visualised using CuSO₄/H₃PO₄ and identified by comparison with the standards. The profile is representative of three EgAgB and HCF batches, which were independently analysed. The wedges indicate increasing amount of loading samples. NLStd: neutral lipid standard; CH: cholesterol; FA: free fatty acid; TAG: triacylglycerols; FAMEs: fatty acid methyl esters; CL: cholesteryl laurate; PLStd: polar lipid standard; PC: phosphatidylcholine; PS: phosphatidylserine; PI: phosphatidylinositol; CLP: cardiolipin and PE: phsophatidylethanolamine.</p

Macrophage activation induces formation of the anti-inflammatory lipid cholesteryl-nitrolinoleate

Nitroalkene derivatives of fatty acids act as adaptive, anti-inflammatory signalling mediators, based on their high-affinity PPARγ (peroxisome-proliferator-activated receptor γ) ligand activity and electrophilic reactivity with proteins, including transcription factors. Although free or esterified lipid nitroalkene derivatives have been detected in human plasma and urine, their generation by inflammatory stimuli has not been reported. In the present study, we show increased nitration of cholesteryl-linoleate by activated murine J774.1 macrophages, yielding the mononitrated nitroalkene CLNO2 (cholesteryl-nitrolinoleate). CLNO2 levels were found to increase ∼20-fold 24 h after macrophage activation with Escherichia coli lipopolysaccharide plus interferon-γ; this response was concurrent with an increase in the expression of NOS2 (inducible nitric oxide synthase) and was inhibited by the •NO (nitric oxide) inhibitor L-NAME (NG-nitro-L-arginine methyl ester). Macrophage (J774.1 and bone-marrow-derived cells) inflammatory responses were suppressed when activated in the presence of CLNO2 or LNO2 (nitrolinoleate). This included: (i) inhibition of NOS2 expression and cytokine secretion through PPARγ and •NO-independent mechanisms; (ii) induction of haem oxygenase-1 expression; and (iii) inhibition of NF-κB (nuclear factor κB) activation. Overall, these results suggest that lipid nitration occurs as part of the response of macrophages to inflammatory stimuli involving NOS2 induction and that these by-products of nitro-oxidative reactions may act as novel adaptive down-regulators of inflammatory responses