Empleo de urea de liberación controlada en el crecimiento del arándano Vaccinium corymbosum cv. Biloxi en invernadero de la UNALM

Universidad Nacional Agraria La Molina. Facultad de Agronomía. Departamento Académico de SuelosSe realizó una investigación para evaluar el efecto de dos tipos de fertilizante nitrogenado (urea+NBPT y urea), tres dosis de fertilización nitrogenada (15, 30 y 60 ppm) y dos fraccionamientos (sin fraccionamiento y con fraccionamiento), utilizando plantones de arándano (Vaccinium corymbosum L.). El experimento se realizó en el invernadero “Sven Villagracía” del Departamento Académico de Suelos de la Facultad de Agronomía de la Universidad Nacional Agraria La Molina (12° 05´S, 76° 57´W a 238 m.s.n.m.). el diseño experimental empleado fue completo al azar con enfoque factorial 2x3x2, los tratamientos fueron las combinaciones de los niveles de tipos, dosis y fraccionamientos. La materia seca responde a una mayor eficiencia de disponibilidad de nitrógeno, la cual a su vez es afectada por el uso de fertilizantes con o sin inhibidores, distintas dosis y fraccionamientos de la fertilización. La absorción de macronutrientes (N, P, K, Mg y Ca) en arándano cv. Biloxy, se ve afectado significativamente por los fertilizantes nitrogenados con o sin inhibidores. Solo la absorción de los macronutrientes (N, P y K) son afectados por los números de fraccionamientos de fertilización nitrogenada.An investigation was conducted to evaluate the effect of two types of nitrogen fertilizer (urea + NBPT and urea), three doses of nitrogen fertilization (15, 30 and 60 ppm) and two fractionations (without fractionation and fractionation), using blueberry (Vaccinium corymbosum L.). The experiment was conducted in the greenhouse "Sven Villagarcía" of the Academic Department of Soils of the Faculty of Agronomy of the Universidad Nacional Agraria La Molina (12 ° 05´S, 76 ° 57´W at 238 m.a.s.l.). The experimental design used was randomized with a 2x3x2 factorial approach, the treatments were the combinations of the levels of types, doses and fractionations. Dry matter responds to a greater efficiency of nitrogen availability, which in turn is affected by the use of fertilizers with or without inhibitors, different doses and fractionation of fertilization. The absorption of macronutrients (N, P, K, Mg and Ca) in blueberry cv. Biloxy, is significantly affected by nitrogen fertilizers with or without inhibitors. Only the absorption of macronutrients (N, P and K) are affected by the numbers of nitrogen fertilization fractionation

Substitutions in PBP2b from β-lactam resistant Streptococcus pneumoniae have different effects on enzymatic activity and drug reactivity

Pneumococcus resists β-lactams by expressing variants of its target enzymes, the penicillin-binding proteins (PBPs), with many amino acid substitutions. Up to 10% of the sequence can be modified. These altered PBPs have a much reduced reactivity with the drugs but retain their physiological activity of cross-linking the peptidoglycan, the major constituent of the bacterial cell wall. However, as β-lactams are chemical and structural mimics of the natural substrate, resistance mediated by altered PBPs raises the following paradox: how PBPs that react poorly with the drugs maintain a sufficient level of activity with the physiological substrate? This question is addressed for the first time in this study, which compares the peptidoglycan cross-linking activity of PBP2b from susceptible and resistant strains with their inhibition by different β-lactams. Unexpectedly, the enzymatic activity of the variants did not correlate with their antibiotic reactivity. This finding indicates that some of the numerous amino acid substitutions were selected to restore a viable level of enzymatic activity by a compensatory molecular mechanism

Second-generation sulfonamide inhibitors of D-glutamic acid-adding enzyme: activity optimisation with conformationally rigid analogues of D-glutamic acid.

peer reviewedD-Glutamic acid-adding enzyme (MurD) catalyses the essential addition of d-glutamic acid to the cytoplasmic peptidoglycan precursor UDP-N-acetylmuramoyl-l-alanine, and as such it represents an important antibacterial drug-discovery target enzyme. Based on a series of naphthalene-N-sulfonyl-d-Glu derivatives synthesised recently, we synthesised two series of new, optimised sulfonamide inhibitors of MurD that incorporate rigidified mimetics of d-Glu. The compounds that contained either constrained d-Glu or related rigid d-Glu mimetics showed significantly better inhibitory activities than the parent compounds, thereby confirming the advantage of molecular rigidisation in the design of MurD inhibitors. The binding modes of the best inhibitors were examined with high-resolution NMR spectroscopy and X-ray crystallography. We have solved a new crystal structure of the complex of MurD with an inhibitor bearing a 4-aminocyclohexane-1,3-dicarboxyl moiety. These data provide an additional step towards the development of sulfonamide inhibitors with potential antibacterial activities

Intervención no farmacológica como estrategia para favorecer el control de la hipertensión arterial y mejorar el cumplimiento antihipertensivo

ResumenObjetivoComprobar la eficacia de una intervención mediante una revista educacional en el cumplimiento antihipertensivo de la hipertensión arterial (HTA) no controlada.DiseñoEstudio clínico controlado, aleatorizado y multicéntrico.EmplazamientoOchenta y siete Centros de Salud de España.ParticipantesSe incluyeron 450 pacientes hipertensos diagnosticados de HTA no controlada.IntervenciónSe formaron 2 grupos con 225 individuos: a) grupo de intervención (GI), los que recibieron una revista educacional domiciliaria bimensual y b) grupo de control (GC), que tuvieron práctica clínica habitual.Mediciones principalesEl cumplimiento se midió mediante monitores electrónicos (MEMS-Aardex). Se calculó el porcentaje de cumplimiento, el porcentaje de cumplidores del total de dosis y de días en los que tomaba una dosis y el NNT (number needed to treat 'número de pacientes que es necesario tratar'). Se definió cumplidor un consumo del 80 al 110%. Se calculó la presión arterial media y los porcentajes de los controlados.ResultadosConcluyeron 393 individuos (edad: 62,4 años [desviación estándar de 11,6 años]), 196 pacientes del GI y 197 pacientes del GC. Ciento ochenta y cuatro eran varones (46,8%).Fueron cumplidores del total de las dosis tomadas el 83,2% en el GI (del 78 al 88,4%) y el 49,2% del GC (IC del 95%: del 42,2 al 56,2%) (p=0,0001) y fueron cumplidores diarios el 74% del GI (IC del 95%: del 67,9 al 80,1%) y el 42,6% del GC (IC del 95%: del 35,7 al 49,5%) (p=0,0001).El control de la HTA fue del 81,6% en el GI (IC del 95%: del 76,2 al 86,5%) y del 56,3% en el GC (IC del 95%: del 49,4 al 63,2%). El NNT con la intervención fue de 3,3 pacientes.ConclusionesEl incumplimiento del tratamiento fue muy alto. La revista educacional es una estrategia eficaz para disminuir el incumplimiento y mejorar el grado de control de la HTA.AbstractObjetiveTo evaluate the efficacy of an intervention by means of an educational magazine on treatment compliance in uncontrolled arterial hypertension (AHT).DesignControlled, randomised clinical trial.Setting87 primary care centres. Spain.ParticipantsA total of 450 patients with uncontrolled hypertension were included.InterventionTwo groups of 225 patients were formed: 1) Control group (CG): standard health intervention; 2) Intervention Group (IG): received a twice monthly educational magazine at home.Main measurementsCompliance was measured using the Medication Event Monitoring System (MEMS-Aardex). Compliance rate (CR) was recorded. Compliers were defined as individuals with a treatment compliance of 80–110%. The percentage of compliers, the mean percentage of doses taken and the percentage of patients taking the medication at the correct times were estimated. The mean blood pressures (BPs) and the percentage of controlled patientswere calculated. The number needed to treat (NNT) was calculated.ResultsA total of 393 individuals were evaluable (Age: 62.4 years), 196 in the IG and 197 in the CG. There were 83.2% (95% CI 78–88.4) and 49.2% (95% CI 42.2–56.2) (P=0.0001) of overall compliers in the IG and CG, respectively and 74% (95% CI: 67.9–80.1) and 42.6% (95% CI=35.7–49.5) (P=0.0001) of correct times compliers. A total of 81.6% (95% CI=76.2–86.5%)) were controlled in the IG and 56.3% (95% CI=49.4–63.2) in the CG. The NNT was 3.3 patients.ConclusionsTherapeutic non-compliance was very high. The educational magazine is an effective strategy to improve the compliance and degree of control of the AHT

Structural Basis of Cytotoxicity Mediated by the Type III Secretion Toxin ExoU from Pseudomonas aeruginosa

The type III secretion system (T3SS) is a complex macromolecular machinery employed by a number of Gram-negative pathogens to inject effectors directly into the cytoplasm of eukaryotic cells. ExoU from the opportunistic pathogen Pseudomonas aeruginosa is one of the most aggressive toxins injected by a T3SS, leading to rapid cell necrosis. Here we report the crystal structure of ExoU in complex with its chaperone, SpcU. ExoU folds into membrane-binding, bridging, and phospholipase domains. SpcU maintains the N-terminus of ExoU in an unfolded state, required for secretion. The phospholipase domain carries an embedded catalytic site whose position within ExoU does not permit direct interaction with the bilayer, which suggests that ExoU must undergo a conformational rearrangement in order to access lipids within the target membrane. The bridging domain connects catalytic domain and membrane-binding domains, the latter of which displays specificity to PI(4,5)P2. Both transfection experiments and infection of eukaryotic cells with ExoU-secreting bacteria show that ExoU ubiquitination results in its co-localization with endosomal markers. This could reflect an attempt of the infected cell to target ExoU for degradation in order to protect itself from its aggressive cytotoxic action

Architecture of a PKS-NRPS hybrid megaenzyme involved in the biosynthesis of the genotoxin colibactin

International audienceThe genotoxin colibactin produced by Escherichia coli is involved in the development of colorectal cancers. This secondary metabolite is synthesized by a multi-protein machinery, mainly composed of non-ribosomal peptide synthetase (NRPS)/polyketide synthase (PKS) enzymes. In order to decipher the function of a PKS-NRPS hybrid enzyme implicated in a key step of colibactin biosynthesis, we conducted an extensive structural characterization of the ClbK megaenzyme. Here we present the crystal structure of the complete trans-AT PKS module of ClbK showing structural specificities of hybrid enzymes. In addition, we report the SAXS solution structure of the full-length ClbK hybrid that reveals a dimeric organization as well as several catalytic chambers. These results provide a structural framework for the transfer of a colibactin precursor through a PKS-NRPS hybrid enzyme and can pave the way for re-engineering PKS-NRPS hybrid megaenzymes to generate diverse metabolites with many applications

Structural-functional analysis of the oligomeric protein R-phycoerythrin

The structure of phycobiliproteins and their spatial organization in the phycobilisome provide the environment for high efficiency in light harvesting and conduction towards photosystem II. This article focuses on the analysis of R-phycoerythrin, a light harvesting hexameric phycobiliprotein that is part of the phycobilisomes. The interaction surfaces and the environment of the chromophores of R-phycoerythrin were studied in order to explain its structural stability and spectroscopic sensitivity, properties revealed by perturbation experiments. Three interaction surfaces are described (ab), (ab)3 and (ab)6. The analysis shows the importance of a subunits in the interaction between trimers, the homodimeric nature of the monomer (ab) and also the presence of anchor points in every interaction surface studied: a18Phe and b18Tyr for (ab), b76Asn for (ab)3 and a25Asn for (ab)6 . Side chains of arginine, lysine or glutamine residues are located in the proximity of the chromophores providing the correct stabilization of their carboxylates. Aspartic acids residues are associated through H-bonds to the N atom of the two central rings of the tetrapyrrolic chromophores. Changes in the spectroscopic properties are observed in perturbation experiments, confirming the spatial requirement for an efficient resonance energy transfer among chromophores and through the phycobilisom

MreB and MurG as scaffolds for the cytoplasmic steps of peptidoglycan biosynthesis.

International audiencePeptidoglycan is a major determinant of cell shape in bacteria, and its biosynthesis involves the concerted action of cytoplasmic, membrane-associated and periplasmic enzymes. Within the cytoplasm, Mur enzymes catalyse the first steps leading to peptidoglycan precursor biosynthesis, and have been suggested as being part of a multicomponent complex that could also involve the transglycosylase MurG and the cytoskeletal protein MreB. In order to initialize the characterization of a potential Mur interaction network, we purified MurD, MurE, MurF, MurG and MreB from Thermotoga maritima and characterized their interactions using membrane blotting and surface plasmon resonance. MurD, MurE and MurF all recognize MurG and MreB, but not each other, while the two latter proteins interact. In addition, we solved the crystal structures of MurD, MurE and MurF, which indicate that their C-termini display high conformational flexibilities. The differences in Mur conformations could be important parameters for the stability of an intracytoplasmic murein biosynthesis complex

Bacterial secretins: Mechanisms of assembly and membrane targeting

International audienceSecretion systems are employed by bacteria to transport macromolecules across membranes without compromising their integrities. Processes including virulence, colonization, and motility are highly dependent on the secretion of effector molecules toward the immediate cellular environment, and in some cases, into the host cytoplasm. In Type II and Type III secretion systems, as well as in Type IV pili, homomultimeric complexes known as secretins form large pores in the outer bacterial membrane, and the localization and assembly of such 1 MDa molecules often relies on pilotins or accessory proteins. Significant progress has been made toward understanding details of interactions between secretins and their partner proteins using approaches ranging from bacterial genetics to cryo electron microscopy. This review provides an overview of the mode of action of pilotins and accessory proteins for T2SS, T3SS, and T4PS secretins, highlighting recent near-atomic resolution cryo-EM secretin complex structures and underlining the importance of these interactions for secretin functionality

Flexibility of thiamine diphosphate revealed by kinetic crystallographic studies of the reaction of pyruvate-ferredoxin oxidoreductase with pyruvate.

International audiencePyruvate-ferredoxin oxidoreductases (PFOR) are unique among thiamine pyrophosphate (ThDP)-containing enzymes in giving rise to a rather stable cofactor-based free-radical species upon the decarboxylation of their first substrate, pyruvate. We have obtained snapshots of unreacted and partially reacted (probably as a tetrahedral intermediate) pyruvate-PFOR complexes at different time intervals. We conclude that pyruvate decarboxylation involves very limited substrate-to-product movements but a significant displacement of the thiazolium moiety of ThDP. In this respect, PFOR seems to differ substantially from other ThDP-containing enzymes, such as transketolase and pyruvate decarboxylase. In addition, exposure of PFOR to oxygen in the presence of pyruvate results in significant inhibition of catalytic activity, both in solution and in the crystals. Examination of the crystal structure of inhibited PFOR suggests that the loss of activity results from oxime formation at the 4' amino substituent of the pyrimidine moiety of ThDP