Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin co-receptor assemblies.

Cullin RING-type E3 ubiquitin ligases SCFTIR1/AFB1-5 and their AUX/IAA targets perceive the phytohormone auxin. The F-box protein TIR1 binds a surface-exposed degron in AUX/IAAs promoting their ubiquitylation and rapid auxin-regulated proteasomal degradation. Here, by adopting biochemical, structural proteomics and in vivo approaches we unveil how flexibility in AUX/IAAs and regions in TIR1 affect their conformational ensemble allowing surface accessibility of degrons. We resolve TIR1·auxin·IAA7 and TIR1·auxin·IAA12 complex topology, and show that flexible intrinsically disordered regions (IDRs) in the degron's vicinity, cooperatively position AUX/IAAs on TIR1. We identify essential residues at the TIR1 N- and C-termini, which provide non-native interaction interfaces with IDRs and the folded PB1 domain of AUX/IAAs. We thereby establish a role for IDRs in modulating auxin receptor assemblies. By securing AUX/IAAs on two opposite surfaces of TIR1, IDR diversity supports locally tailored positioning for targeted ubiquitylation, and might provide conformational flexibility for a multiplicity of functional states.

Understanding the disrupting mechanism of the Tau aggregation motif "306 VQIVYK311 " by phenylthiazolyl-hydrazides inhibitors.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by the abnormal processing of the Tau and the amyloid precursor proteins. The unusual aggregation of Tau is based on the formation of intermolecular ß-sheets through two motifs: 275 VQIINK280 and 306 VQIVYK311 . Phenylthiazolyl-hydrazides (PTHs) are capable of inhibiting/disassembling Tau aggregates. However, the disaggregation mechanism of Tau oligomers by PTHs is still unknown. In this work, we studied the disruption of the oligomeric form of the Tau motif 306 VQIVYK311 by PTHs through molecular docking, molecular dynamics, and free energy calculations. We predicted hydrophobic interactions as the major driving forces for the stabilization of Tau oligomer, with V306 and I308 being the major contributors. Nonpolar component of the binding free energy is essential to stabilize Tau-PTH complexes. PTHs disrupted mainly the van der Waals interactions between the monomers, leading to oligomer destabilization. Destabilization of full Tau filament by PTHs and emodin was not observed in the sampled 20 ns; however, in all cases, the nonpolar component of the binding free energy is essential for the formation of Tau filament-PTH and Tau filament-emodin. These results provide useful clues for the design of more effective Tau-aggregation inhibitors.

Design of a Helical-Stabilized, Cyclic, and Nontoxic Analogue of the Peptide Cm-p5 with Improved Antifungal Activity.

Following the information obtained by a rational design study, a cyclic and helical-stabilized analogue of the peptide Cm-p5 was synthetized. The cyclic monomer showed an increased activity in vitro against Candida albicans and Candida parapsilosis, compared to Cm-p5. Initially, 14 mutants of Cm-p5 were synthesized following a rational design to improve the antifungal activity and pharmacological properties. Antimicrobial testing showed that the activity was lost in each of these 14 analogues, suggesting, as a main conclusion, that a Glu-His salt bridge could stabilize Cm-p5 helical conformation during the interaction with the plasma membrane. A derivative, obtained by substitution of Glu and His for Cys, was synthesized and oxidized with the generation of a cyclic monomer with improved antifungal activity. In addition, two dimers were generated during the oxidation procedure, a parallel and antiparallel one. The dimers showed a helical secondary structure in water, whereas the cyclic monomer only showed this conformation in SDS. Molecular dynamic simulations confirmed the helical stabilizations for all of them, therefore indicating the possible essential role of the Glu-His salt bridge. In addition, the antiparallel dimer showed a moderate activity against Pseudomonas aeruginosa and a significant activity against Listeria monocytogenes. Neither the cyclic monomer nor the dimers were toxic against macrophages or THP-1 human cells. Due to its increased capacity for fungal control compared to fluconazole, its low cytotoxicity, together with a stabilized α-helix and disulfide bridges, that may advance its metabolic stability, and in vivo activity, the new cyclic Cm-p5 monomer represents a potential systemic antifungal therapeutic candidate.

In silico identification of new potentially active brassinosteroid analogues.

Brassinosteroids (BRs) are hormones found in a wide range of plant species, they are synthesized at low concentrations and are essential for normal growth and development. These phytohormones are recognized by the Leucine-rich-repeat ectodomain of the receptor-like-kinase BRI1 which leads to subsequent downstream signaling mediating plant growth/development. In spite of the advantages that BRs offer, their extraction from natural sources is highly expensive, which constitutes one of its major limitations. Thus, the design and synthesis of structural and/or functional analogues of BRs with higher activity and lower cost has a great practical significance in world agriculture. In this matter, in silico methods, such as molecular docking, are valuable tools for the prediction and design of new compounds with improved activity. In this work we performed molecular docking simulations of 20 synthetic steroids in order to identify active compounds. Contact based analysis, level of exposure of polar groups to the solvent and binding affinity were the parameters used to consider if a synthetic steroid was active. Our results suggested that 17 out of a total of 20 of the analyzed steroids can potentially activate BRI1 receptor.

Ausencia de efectos de la terapia floral aplicada a adultos jóvenes con el fin de mejorar su memoria / Lack of effects of flower therapy applied to young adults to improve their memory function

Se realizó un estudio experimental controlado a doble ciegas para comprobar la efectividad atribuida a las llamadas esencias florales de Bach para mejorar las funciones de memoria. Para ello se administró una mezcla de 5 flores (Chestnut Bud, Red Chestnut, Wild Oat, Honey Suckle y Clematis) obtenidas de la Farmacia Homeopática (23 esq. a M, Vedado La Habana) a estudiantes de 1er año de la Universidad de La Habana. Se constituyeron 3 grupos, uno sin tratamiento y los otros dos que recibieron 4 aplicaciones diarias durante 10 días de 4 gotas sublinguales de la mezcla floral o un placebo que fue el vehículo en que se preparan y conservan las flores. Para evaluar el efecto aludido se aplicó a todos los participantes un test de memoria (test de Rey) en días sucesivos. En el primer día les fue presentada una lista de 15 palabras y se recogió por escrito la cantidad de palabras correctas que fueron capaces de evocar de forma inmediata. Este procedimiento se repitió 5 veces y se notó un incremento progresivo en el número de aciertos. Al día siguiente se les entregó una historieta escrita que contenía, dispersas entre otras, las 15 palabras de la lista y se le pidió subrayar las que pudieran identificar como pertenecientes a esa lista. El análisis estadístico de los resultados (ANOVA) no permitió identificar diferencias significativas entre los grupos en ninguna de las pruebas. Estos resultados no apoyan la hipótesis de que tales preparados ejerzan un efecto real y sugieren que su posible éxito en algunos casos es de tipo placebo.

An experimental double blind controlled study was carried out to confirm the effectiveness of the so-called Bach flower essences in the improvement of memory functions. To this end, a five flower mixture (Chesnut, Bud, Red Chesnut, Wild Oat, Honey Suckle and Clematis) obtained from homeopathic drugstore located in Havana was administered to first-year university students at the University of Havana. Three groups were created, one without treatment and the two other groups received 4 daily doses for 10 days at a rate of 4 drops sublingually of the flower mixture or the placebo in which flower are prepared and preserved. To assess the effect, a memory test (Rey´s test) was applied to the participants in the subsequent days. The first day, they were given a list of 15 words and the number of correct words that they were able to remember immediately was recorded in writing. This method was repeated 5 times; there was a progressive increase in the number of correct words remembered. On the following day, they were given some cartoon story containing among other the 15 words from the list and the participants were asked to identify them. The Statistical analysis (ANOVA) of the results did not show significant differences among the groups in none of the tests. These results did not support the hypothesis that these flower mixtures have a real impact and suggested that their possible success in some cases be of placebo-type.

Ausencia de efectos de la terapia floral aplicada a adultos jóvenes con el fin de mejorar su memoria / Lack of effects of flower therapy applied to young adults to improve their memory function

Se realizó un estudio experimental controlado a doble ciegas para comprobar la efectividad atribuida a las llamadas esencias florales de Bach para mejorar las funciones de memoria. Para ello se administró una mezcla de 5 flores (Chestnut Bud, Red Chestnut, Wild Oat, Honey Suckle y Clematis) obtenidas de la Farmacia Homeopática (23 esq. a M, Vedado La Habana) a estudiantes de 1er año de la Universidad de La Habana. Se constituyeron 3 grupos, uno sin tratamiento y los otros dos que recibieron 4 aplicaciones diarias durante 10 días de 4 gotas sublinguales de la mezcla floral o un placebo que fue el vehículo en que se preparan y conservan las flores. Para evaluar el efecto aludido se aplicó a todos los participantes un test de memoria (test de Rey) en días sucesivos. En el primer día les fue presentada una lista de 15 palabras y se recogió por escrito la cantidad de palabras correctas que fueron capaces de evocar de forma inmediata. Este procedimiento se repitió 5 veces y se notó un incremento progresivo en el número de aciertos. Al día siguiente se les entregó una historieta escrita que contenía, dispersas entre otras, las 15 palabras de la lista y se le pidió subrayar las que pudieran identificar como pertenecientes a esa lista. El análisis estadístico de los resultados (ANOVA) no permitió identificar diferencias significativas entre los grupos en ninguna de las pruebas. Estos resultados no apoyan la hipótesis de que tales preparados ejerzan un efecto real y sugieren que su posible éxito en algunos casos es de tipo placebo(AU)

An experimental double blind controlled study was carried out to confirm the effectiveness of the so-called Bach flower essences in the improvement of memory functions. To this end, a five flower mixture (Chesnut, Bud, Red Chesnut, Wild Oat, Honey Suckle and Clematis) obtained from homeopathic drugstore located in Havana was administered to first-year university students at the University of Havana. Three groups were created, one without treatment and the two other groups received 4 daily doses for 10 days at a rate of 4 drops sublingually of the flower mixture or the placebo in which flower are prepared and preserved. To assess the effect, a memory test (Rey´s test) was applied to the participants in the subsequent days. The first day, they were given a list of 15 words and the number of correct words that they were able to remember immediately was recorded in writing. This method was repeated 5 times; there was a progressive increase in the number of correct words remembered. On the following day, they were given some cartoon story containing among other the 15 words from the list and the participants were asked to identify them. The Statistical analysis (ANOVA) of the results did not show significant differences among the groups in none of the tests. These results did not support the hypothesis that these flower mixtures have a real impact and suggested that their possible success in some cases be of placebo-type(AU)