Central Role of the Copper-Binding Motif in the Complex Mechanism of Action of Ixosin: Enhancing Oxidative Damage and Promoting Synergy with Ixosin B

Ticks transmit multiple pathogens to different hosts without compromising their health. Their ability to evade microbial infections is largely a result of their effective innate immune response including various antimicrobial peptides. Therefore, a deep understanding of how ticks (and other arthropod vectors) control microbial loads could lead to the design of broad-spectrum antimicrobial agents. In this paper we study the role of the amino-terminal copper and nickel (ATCUN)-binding sequence in the peptide ixosin, isolated from the salivary glands of the hard tick Ixodes sinensis. Our results indicate that the ATCUN motif is not essential to the potency of ixosin, but is indispensable to its oxidative mechanism of action. Specifically, the ATCUN motif promotes dioxygen- and copper-dependent lipid (per)­oxidation of bacterial membranes in a temporal fashion coinciding with the onset of bacterial death. Microscopy and studies on model membranes indicate that the oxidized phospholipids are utilized as potential targets of ixosin B (another tick salivary gland peptide) involving its delocalization to the bacterial membrane, thus resulting in a synergistic effect. Our proposed mechanism of action highlights the centrality of the ATCUN motif to ixosin’s mechanism of action and demonstrates a novel way in which (tick) antimicrobial peptides (AMPs) utilize metal ions in its activity. This study suggests that ticks employ a variety of effectors to generate an amplified immune response, possibly justifying its vector competence

N-terminal Dbl domain of the RhoGEF, Kalirin.

Guanine nucleotide exchange factors (GEF) promote the release of GDP from GTPases, thus allowing the free GTPase molecule to bind the more abundant GTP molecule. In the GTP-bound state, the GTPase elicits signal transduction by acting on its effector proteins. Spontaneous release of GDP is a slow process and the catalysis of the GDP release by a GEF is generally a prerequisite for efficient signaling (Vetter and Wittinghofer 2001). The structurally related GEFs form subfamilies that regulate a specific family of GTPase proteins. GEFs that activate Rho GTPases have been implicated in cancer and mental retardation. RhoGEFs are a relatively large family, and many of the *69 human RhoGEFs were discovered based on their oncogenic activation in cancer and cancer models. The catalytic components of RhoGEFs are referred to as Dbl homology domains, after the screen that identified the protein Dbl encoded by the diffuse B-cell lymphoma (dbl) oncogene (Eva and Aaronson 1985). Thus the RhoGEF family is a potential target for treating tumors and cancer

Backbone and side chain NMR assignments of Geobacillus stearothermophilus ZapA allow identification of residues that mediate the interaction of ZapA with FtsZ

Bacterial division begins with the formation of a contractile protein ring at midcell, which constricts the bacterial envelope to generate two daughter cells. The central component of the division ring is FtsZ, a tubulin-like protein capable of self-assembling into filaments which further associate into a higher order structure known as the Z ring. Proteins that bind to FtsZ play a crucial role in the formation and regulation of the Z ring. One such protein is ZapA, a widely conserved 21 kDa homodimeric protein that associates with FtsZ filaments and promotes their bundling. Although ZapA was discovered more than a decade ago, the structural details of its interaction with FtsZ remain unknown. In this work, backbone and side chain NMR assignments for the Geobacillus stearothermophilus ZapA homodimer are described. We titrated FtsZ into (NH)-N-15-H-2-ZapA and mapped ZapA residues whose resonances are perturbed upon FtsZ binding. This information provides a structural understanding of the interaction between FtsZ and ZapA

To Supply of Allowable Trains Movement Speed on a Floating Bridge

Горбатюк, Ю. М. До питання допустимої швидкості руху поїздів по наплавних мостах / Ю. М. Горбатюк, К. І. Солдатов, В. Є. Артьомов // Мости та тунелі: теорія, дослідження, практика. — 2014. — Вип. 6. — С. 24—34. — Бібліогр. в кінці ст.UK: Мета. В публікації наведені результати розрахунків прогонових будов для наплавних мостів. Метою даного дослідження є визначення: максимально допустимої швидкості руху транспорту, яка не призводила б до появи наднормативних напружень і деформацій в конструкціях моста. Методика. В роботі використовується порівняльний метод, аналітичні методи розрахунку мостів, розрахунки на міцність, витривалість, максимальні дотичні напруження. Результати. Збільшення довжини понтону навіть на 1м. (з 10,5 до 11,5 м) супроводжується зниженням переміщень (та інших похідних параметрів напружено-деформованого стану) прогонової будови у 4, 7, 9 разів; за певних розмірів понтонів система значно втрачає стабільність у водному середовищі; висота перерізу понтону не суттєво впливає на стан прогонової будови плавучої системи; швидкість течії водотоку суттєво впливає на напружено-деформований стан наплавного моста; аналіз фазових траєкторій свідчить, що коливання наплавного моста у водному середовищі мають періодичний, але не зовсім стабільний характер; Наукова новизна. Дослідження дозволяє зробити новий крок в детальному моделюванні роботи наплавного мосту з урахуванням швидкості руху тимчасового навантаження. Практична значимість. Враховуючи те, що єдиного нормативного документу, який регламентував би порядок визначення швидкісних режимів руху залізничного і автомобільного транспорту по наплавних мостах в Україні, наразі не існує, публікація дає змогу зробити ряд висновків, що є універсальними для розрахунку допустимої швидкості руху по наплавних мостах.RU: Цель. В публикации приведены результаты расчетов пролетных строений для наплавных мостов. Целью данного исследования является определение: максимально допустимой скорости движения транспорта, которая не приводила бы к появлению сверхнормативных напряжений и деформаций в конструкциях моста. Методика. В работе используется сравнительный метод, аналитические методы расчета мостов, расчеты на прочность, выносливость, максимальные касательные напряжения. Результаты. Увеличение длины понтона даже на 1 м (с 10,5 до 11,5 м) сопровождается снижением перемещений (и других производных параметров напряженно-деформированного состояния) пролетного строения в 4, 7, 9 раз; при определенных размерах понтонов система значительно теряет стабильность в водной среде; высота сечения понтона не существенно влияет на состояние пролетного строения плавучей системы; скорость течения водотока существенно влияет на напряженно-деформированное состояние наплавного моста; анализ фазовых траекторий свидетельствует, что колебания наплавного моста в водной среде имеют периодический, но не совсем стабильный характер. Научная новизна. Исследование позволяет сделать новый шаг в детальном моделировании работы наплавного моста с учетом скорости движения временной нагрузки. Практическая значимость. Учитывая то, что единого нормативного документа, регламентирующего порядок определения скоростных режимов движения железнодорожного и автомобильного транспорта по наплавных мостах в Украине, пока не существует, публикация позволяет сделать ряд выводов, которые являются универсальными для расчета допустимой скорости движения по наплавным мостам.EN: Purpose. This publication presents the results of calculations spans for floating bridges. Аim of this study is to determine the maximum speed of the vehicle, which did not lead to abnormal appearance to stresses and strains in the construction of the bridge. Methodology. This paper uses the comparative method, analytical methods for calculating bridges calculations of strength, endurance, maximum shear stress. Findings. Increasing the length of pontoon even at 1m. (from 10,5 to 11,5 m) is accompanied by a decrease in displacement (and other derived parameters of the stress-strain state) span 4, 7, 9 times; for a certain size pontoons system loses much stability in the aquatic environment; section height pontoon not significantly affect the state span floating system; watercourse flow velocity significantly affects the stress-strain state of the floating bridge; The analysis of phase trajectories shows that fluctuations floating bridge in the aquatic environment are periodic, but not quite stable nature. Originality. Research allows you to make a new step in the detailed modeling of the floating bridge considering the velocity of temporary load. Practical value. Given that a single regulatory document that would regulate the procedure for determining Movement speed rail and road transport on floating bridges in Ukraine does not exist, the publication allows you to draw some conclusions that are universal to calculate allowable speed on floating bridges

Integrin β3 Phosphorylation Dictates Its Complex with the Shc Phosphotyrosine-binding (PTB) Domain*

Adaptor protein Shc plays a key role in mitogen-activated protein kinase (MAPK) signaling pathway, which can be mediated through a number of different receptors including integrins. By specifically recognizing the tyrosine-phosphorylated integrin β3, Shc has been shown to trigger integrin outside-in signaling, although the structural basis of this interaction remains nebulous. Here we present the detailed structural analysis of Shc phosphotyrosine-binding (PTB) domain in complex with the bi-phosphorylated β3integrin cytoplasmic tail (CT). We show that this complex is primarily defined by the phosphorylation state of the integrin C-terminal Tyr759, which fits neatly into the classical PTB pocket of Shc. In addition, we have identified a novel binding interface which concurrently accommodates phosphorylated Tyr747 of the highly conserved NPXY motif of β3. The structure represents the first snapshot of an integrin cytoplasmic tail bound to a target for mediating the outside-in signaling. Detailed comparison with the known Shc PTB structure bound to a target TrkA peptide revealed some significant differences, which shed new light upon the PTB domain specificity

1, 3-γ-Silyl-elimination in electron-deficient cationic systems.

Placement of an electron-withdrawing trifluoromethyl group (–CF3) at a putative cationic centre enhances γ-silyl neighbouring-group participation (NGP). In stark contrast to previously studied γ-silyl-substituted systems, the preferred reaction pathway is 1,3-γ-silyl elimination, giving ring closure over solvent substitution or alkene formation. The scope of this cyclopropanation reaction is explored for numerous cyclic and acyclic examples, proving this method to be a viable approach to preparing CF3-substituted cyclopropanes and bicyclic systems, both containing quaternary centres. Rate-constants, kinetic isotope effects, and quantum mechanical calculations provided evidence for this enhancement and further elaborated the disparity in the reaction outcome between these systems and previously studied γ-silyl systems

Mapping the phosphoinositide-binding site on chick cofilin explains how PIP2 regulates the cofilin-actin interaction

Cofilin plays a key role in the choreography of actin dynamics via its ability to sever actin filaments and increase the rate of monomer dissociation from pointed ends. The exact manner by which phosphoinositides bind to cofilin and inhibit its interaction with actin has proven difficult to ascertain. We determined the structure of chick cofilin and used NMR chemical shift mapping and structure-directed mutagenesis to unambiguously locate its recognition site for phosphoinositides (Pis). This structurally unique recognition site requires both the acyl chain and head group of the PI for a productive interaction, and it is not inhibited by phosphorylation of cofilin. We propose that the interaction of cofilin with membrane-bound Pis abrogates its binding to both actin and actin-interacting protein 1, and facilitates spatiotemporal regulation of cofilin activity