Proteolysis of HCF-1 by Ser/Thr glycosylation-incompetent O-GlcNAc transferase:UDP-GlcNAc complexes

In complex with the cosubstrate UDP-N-acetylglucosamine (UDP-GlcNAc),O-linked-GlcNAc transferase (OGT) catalyzes Ser/ThrO-GlcNAcylation of many cellular proteins and proteolysis of the transcriptional coregulator HCF-1. Such a dual glycosyltransferase-protease activity, which occurs in the same active site, is unprecedented and integrates both reversible and irreversible forms of protein post-translational modification within one enzyme. Although occurring within the same active site, we show here that glycosylation and proteolysis occur through separable mechanisms. OGT consists of tetratricopeptide repeat (TPR) and catalytic domains, which, together with UDP-GlcNAc, are required for both glycosylation and proteolysis. Nevertheless, a specific TPR domain contact with the HCF-1 substrate is critical for proteolysis but not Ser/Thr glycosylation. In contrast, key catalytic domain residues and even a UDP-GlcNAc oxygen important for Ser/Thr glycosylation are irrelevant for proteolysis. Thus, from a dual glycosyltransferase-protease, essentially single-activity enzymes can be engineered both in vitro and in vivo. Curiously, whereas OGT-mediated HCF-1 proteolysis is limited to vertebrate species, invertebrate OGTs can cleave human HCF-1. We present a model for the evolution of HCF-1 proteolysis by OGT

The conserved threonine-rich region of the HCF-1PRO repeat activates promiscuous OGT:UDP-GlcNAc glycosylation and proteolysis activities

O-Linked GlcNAc transferase (OGT) possesses dual glycosyltransferase-protease activities. OGT thereby stably glycosylates serines and threonines of numerous proteins and, via a transient glutamate glycosylation, cleaves a single known substrate-the so-called HCF-1 <sub>PRO</sub> repeat of the transcriptional co-regulator host-cell factor 1 (HCF-1). Here, we probed the relationship between these distinct glycosylation and proteolytic activities. For proteolysis, the HCF-1 <sub>PRO</sub> repeat possesses an important extended threonine-rich region that is tightly bound by the OGT tetratricopeptide-repeat (TPR) region. We report that linkage of this HCF-1 <sub>PRO</sub> -repeat, threonine-rich region to heterologous substrate sequences also potentiates robust serine glycosylation with the otherwise poor R <sub>p</sub> -αS-UDP-GlcNAc diastereomer phosphorothioate and UDP-5S-GlcNAc OGT co-substrates. Furthermore, it potentiated proteolysis of a non-HCF-1 <sub>PRO</sub> -repeat cleavage sequence, provided it contained an appropriately positioned glutamate residue. Using serine- or glutamate-containing HCF-1 <sub>PRO</sub> -repeat sequences, we show that proposed OGT-based or UDP-GlcNAc-based serine-acceptor residue activation mechanisms can be circumvented independently, but not when disrupted together. In contrast, disruption of both proposed activation mechanisms even in combination did not inhibit OGT-mediated proteolysis. These results reveal a multiplicity of OGT glycosylation strategies, some leading to proteolysis, which could be targets of alternative molecular regulatory strategies

Методика перестроения маршрута полета воздушного судна в процессе его выполнения

   A significant number of aviation incidents is related to loss of control in flight and controlled flight into terrain (LOC-I, CFIT, LALT categories). Investigation of these aviation incidents has revealed that these incidents often occur due to the need for rapid changes in flight routes as a result of detecting obstacles, such as thunderstorms, along the aircraft's path. During the determination of alternative routes to circumvent the encountered obstacle, as well as during the implementation process of the chosen rerouted route, the flight crew makes errors due to increased psycho-physiological workload and time constraints. This article presents an approach to the automatic rerouting of the aircraft's flight route to avoid obstacles detected during flight. The algorithm proposed by the authors allows for evaluating the safety of the original route, calculating alternative route options to bypass the obstacles encountered during flight, verifying their feasibility considering the aircraft's flight technical characteristics and control parameter limitations, and selecting the optimal rerouted route based on specific criteria, such as minimizing the increase in the flight route length, reducing additional fuel consumption, time required for implementing the new flight route, etc. Examples of rerouting the flight route of a hypothetical aircraft with detected obstacles along the flight path are provided in the article to demonstrate the algorithm's functionality. It is shown, in particular, that in the considered example, the shortest route for obstacle avoidance is not optimal in terms of time. It is also demonstrated that the safety of flying along the identified alternative rerouted routes depends, among other factors, on the selected flight speed. Therefore, for each calculated rerouted route, the algorithm determines a range of speeds within which the implementation of the obtained rerouted route is possible. This highlights the complexity and non-triviality of the pilot's task of autonomously finding a safe obstacle avoidance route on board the aircraft.   Большое количество авиационных происшествий связано с потерей управления в полете, а также со столкновением с землей в управляемом полете (категории LOC-I, CFIT, LALT). В результате расследования данных авиационных происшествий выявлено, что часто указанные авиационные происшествия обусловлены необходимостью быстрого изменения маршрута полета вследствие выявления на пути следования воздушного судна препятствий, например, грозового фронта. При определении альтернативных маршрутов облета возникшего препятствия, а также впроцессе реализации выбранного маршрута облета экипаж совершает ошибки ввиду повышенной психофизиологической нагрузки и дефицита времени. В данной статье представлен подход к автоматическому перестроению маршрута полета воздушного судна для облета обнаруженных в процессе полета препятствий. Предлагаемый авторами алгоритм позволяет оценить безопасность исходного маршрута, рассчитать варианты альтернативных маршрутов облета обнаруженных впроцессе полета препятствий, проверить их на реализуемость с учетом летно-технических характеристик воздушного судна, ограничений на управляющие параметры, а также выбрать среди найденных маршрутов облета оптимальный с точки зрения какого-либо критерия, например, исходя из минимизации увеличения протяженности маршрута полета, сокращения дополнительных затрат топлива, времени, необходимого на реализацию нового маршрута полета, и т. д. Для демонстрации работоспособности алгоритма в статье представлены примеры перестроения маршрута полета гипотетического воздушного судна с выявленными на пути следования препятствиями. Показано, в частности, что в рассмотренном примере самый короткий маршрут облета препятствий не является оптимальным с точки зрения временных затрат. Также демонстрируется, что безопасность пролета по найденным альтернативным маршрутам облета препятствий зависит в том числе от выбранной скорости полета. Поэтому для каждого рассчитанного маршрута облета препятствий алгоритм определяет диапазон скоростей, в котором возможна реализация полученного маршрута облетапрепятствий. Последнее указывает на сложность и нетривиальность самостоятельного решения задачи поиска безопасного маршрута облета препятствий пилотом на борту воздушного судна

Thio-linked UDP-peptide conjugates as O-GlcNAc transferase inhibitors

O-GlcNAc transferase (OGT) is an essential glycosyltransferase that installs the O-GlcNAc post-translational modification on the nucleocytoplasmic proteome. We report the development of S-linked UDP–peptide conjugates as potent bisubstrate OGT inhibitors. These compounds were assembled in a modular fashion by photoinitiated thiol–ene conjugation of allyl-UDP and optimal acceptor peptides in which the acceptor serine was replaced with cysteine. The conjugate VTPVC­(S-propyl-UDP)­TA (<i>K</i>_i = 1.3 μM) inhibits the OGT activity in HeLa cell lysates. Linear fusions of this conjugate with cell penetrating peptides were explored as prototypes of cell-penetrant OGT inhibitors. A crystal structure of human OGT with the inhibitor revealed mimicry of the interactions seen in the pseudo-Michaelis complex. Furthermore, a fluorophore-tagged derivative of the inhibitor works as a high affinity probe in a fluorescence polarimetry hOGT assay

Современные методы предотвращения выкатываний воздушных судов за пределы взлетно-посадочной полосы

The landing of the aircraft has always been the most challenging and dangerous stage of the flight. In order to make a safe landing, the aircraft (A/C) requires reducing the vertical (at the stage of flare-out) and horizontal (prior to touchdown) components of the aircraft's flight speed vector, which in turn reduces the capabilities to increase lift and limits the crew's ability to perform maneuvers. At the same time, during landing the crew must align the aircraft with the runway (RW) and make a touchdown, subsequent A/C landing roll and stop within a rather limited area, which eventually and particularly, under the effect of contributing adverse factors (piloting errors, wind shear, icing, engine failure, aquaplaning, etc.) can cause the aircraft to overshoot and overrun the RW. Currently, as the analysis of aviation accidents statistics shows, the issue of preventing and alerting aircraft overrun is quite relevant. The search for a solution, in terms of preventing aircraft overrunning the runway (RW), is conducted as at the level of aviation authorities as among aircraft manufacturers, operators. Within the framework of this review, an attempt is made to identify and analyze the key factors affecting the dynamics of aircraft motion during landing, using information about aviation accidents that have occurred over the past few years. Notably, such aspects as a human factor and technical features of the operation of modern jet aircraft, influencing the A/C landing roll, are considered. In addition, special attention is paid to consider the methods of prevention and warning of A/C overrun with highlighting the approaches of passive and active protection. Within the framework of the analysis of active protection techniques, the principles of on-board avionic systems operation of the most major aircraft manufacturers, such as Boeing and Airbus, are considered. As an example of the passive protection, the experience of using special energy-absorbing destructible blocks installed next to the runway threshold, is analyzed.Посадка воздушного судна была и остается наиболее сложным и опасным этапом полета. Для совершения безопасной посадки воздушному судну (ВС) необходимо уменьшить вертикальную (на этапе выравнивания)и горизонтальную (на этапе выдерживания) составляющие вектора скорости полета ВС, что в свою очередь уменьшает возможности по увеличению подъемной силы и ограничивает экипаж в возможностях совершения маневров. Также экипаж во время посадки должен подвести ВС к взлетно-посадочной полосе (ВПП) и совершить касание, последующие пробег и остановку ВС в пределах довольно ограниченной по своим размерам площадки, что в конечном итоге, в частности при воздействии сопутствующих неблагоприятных факторов (ошибки пилотирования, сдвиг ветра, обледенение, отказ двигателя, гидроглиссирование и др.), может привести к перелету и выкатыванию самолетов за пределы ВПП. В настоящее время вопрос возможности предотвращения и предупреждения выкатываний ВС, как показывает анализ статистики авиационных происшествий, достаточно актуален. Поиск решения в части предотвращения выкатываний ВС за пределы ВПП ведется как на уровне авиационных властей, так и на уровнях производителей и эксплуатантов ВС. В рамках данной обзорной статьи предпринята попытка выделить и проанализировать ключевые факторы, влияющие на динамику движения ВС при посадке, используя информацию об авиационных происшествиях, произошедших за последние несколько лет. В частности, рассмотрены такие аспекты, как человеческий фактор и технические особенности работы современных реактивных ВС, влияющие на пробег самолета по полосе. Кроме того, особое внимание в статье уделено рассмотрению методов предотвращения и предупреждения выкатываний ВС с выделением методов пассивной и методов активной защиты. В рамках анализа методов активной защиты рассмотрены принципы работы бортовых электронных систем крупнейших авиапроизводителей, таких как Boeing и Airbus. В качестве примера пассивной защиты проанализирован опыт использования специальных энергопоглощающих разрушаемых блоков, размещаемых после торца ВПП

Experience of treatment of presacral tumors

Aim of investigation. Improvement of presacral tumors treatment results.Material and methods. Data of surgical treatment 21 patients with true presacral tumors, operated in Federal government-financed institution «Ryzhikh State Scientific Center of Coloproctology», Ministry of healthcare of the Russian Federation with 2004 on 2013 was analyzed. Study group included 16 women (76%) and 5 men (24%) with mean age of 46,3±15,1 years.Results. Tumor relapse was revealed in 4 (5,6%) of operated patients, tumors in these cases had various histological structure.Conclusion. Experience of surgical interventions at benign retrorectal presacral tumors allows to consider surgical method as adequate treatment approach. The highest relapse rate was observed at malignant tumors; such patients require the combined treatment at specialized oncologic clinic. The choice of surgical access is determined, first of all, by neoplasm localization

O-GlcNAc transferase invokes nucleotide sugar pyrophosphate participation in catalysis

Protein O-GlcNAcylation is an essential post-translational modification on hundreds of intracellular proteins in metazoa, catalyzed by O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) using unknown mechanisms of transfer and substrate recognition. Through crystallographic snapshots and mechanism-inspired chemical probes, we define how human OGT recognizes the sugar donor and acceptor peptide and uses a new catalytic mechanism of glycosyl transfer, involving the sugar donor α-phosphate as the catalytic base as well as an essential lysine. This mechanism seems to be a unique evolutionary solution to the spatial constraints imposed by a bulky protein acceptor substrate and explains the unexpected specificity of a recently reported metabolic OGT inhibitor. © 2012 Nature America, Inc. All rights reserved

Model wzrostu liczby ludnosci miast uwzgledniajacy migracje

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