Cytochrome bd as antioxidant redox enzyme

One of the main functions of enzyme complexes that constitute electron transport (respiratory) chains of organisms is to maintain cellular redox homeostasis by oxidizing reducing equivalents, NADH and quinol. Cytochrome bd is a unique terminal oxidase of the chains of many bacteria including pathogenic species. This redox enzyme couples the oxidation of ubiquinol or menaquinol by molecular oxygen to the generation of proton motive force, a universal energy currency. The latter is used by the organism to produce ATP, another cellular energy currency, via oxidative phosphorylation. Escherichia coli contains two bd–type oxidases, bd-I and bd-II, encoded by the cydAB and appCB operons, respectively. Surprisingly, both bd enzymes make a further contribution to molecular mechanisms of maintaining the appropriate redox balance in the bacterial cell by means of elimination of reactive oxygen species, such as hydrogen peroxide. This review summarizes recent data on the redox-modulated H 2 O 2 -scavenging activities of cytochromes bd-I and bd-II from E. coli. The possibility of such antioxidant properties in cytochromes bd from other bacteria is also discussed

The terminal oxidase cytochrome bd-I confers carbon monoxide resistance to Escherichia coli cells

Carbon monoxide (CO) plays a multifaceted role in the physiology of organisms, from poison to signaling molecule. Heme proteins, including terminal oxidases, are plausible CO targets. Three quinol oxidases terminate the branched aerobic respiratory chain of Escherichia coli. These are the heme-copper cytochrome bo3 and two copper-lacking bd-type cytochromes, bd-I and bd-II. All three enzymes generate a proton motive force during the four-electron oxygen reduction reaction that is used for ATP production. The bd-type oxidases also contribute to mechanisms of bacterial defense against various types of stresses. Here we report that in E. coli cells, at the enzyme concentrations tested, cytochrome bd-I is much more resistant to inhibition by CO than cytochrome bd-II and cytochrome bo3. The apparent half-maximal inhibitory concentration values, IC50, for inhibition of O2 consumption of the membrane-bound bd-II and bo3 oxidases by CO at-150 & mu;M O2 were estimated to be 187.1 & PLUSMN; 11.1 and 183.3 & PLUSMN; 13.5 & mu;M CO, respectively. Under the same conditions, the maximum inhibition observed with the membrane-bound cytochrome bd-I was 20 & PLUSMN; 10% at-200 & mu;M CO

Cytochrome bd oxidase and nitric oxide: from reaction mechanisms to bacterial physiology.

International audience; Experimental evidence suggests that the prokaryotic respiratory cytochrome bd quinol oxidase is responsible for both bioenergetic functions and bacterial adaptation to different stress conditions. The enzyme, phylogenetically unrelated to the extensively studied heme-copper terminal oxidases, is found in many commensal and pathogenic bacteria. Here, we review current knowledge on the catalytic intermediates of cytochrome bd and their reactivity towards nitric oxide (NO). Available information is discussed in the light of the hypothesis that, owing to its high NO dissociation rate, cytochrome bd confers resistance to NO-stress, thereby providing a strategy for bacterial pathogens to evade the NO-mediated host immune attack

Optimization of insulation in ventilated hinged facade systems

The system of hinged ventilated facades is available for a long time and is now widely used in the construction of new and reconstruction of existing buildings for various purposes. As practice shows, the problems associated with the operation of these facade systems are usually caused by mistakes in the design, selection of components and installation of the system. Ventilated facade is a multi-layered enclosing structure, which includes a layer of insulation. Mineral wool slabs are ideal for this facade system, as it has low thermal conductivity, resistance to temperature changes and excellent vapor permeability, which allows to fully open the potential of a ventilated air layer. In the article two ways of installation of thermal insulation are considered: single-layer and two-layer with different types of air interlayer: closed, weakly and strongly ventilated. In accordance with the requirements of Russian and European regulatory documents, the effect of gaps between the thermal insulation plates in a single-layer and two-layer design on the reduction of the heat transfer resistance of hinged facade systems with an air gap was estimated by calculating 2-dimensional temperature fields. The coefficient of thermotechnic uniformity was also defined. As a result, optimal variants of thermal insulation and types of bases for fixing thermal insulation are suggested

Cytochrome bd oxidase from Escherichia coli displays high catalase activity: An additional defense against oxidative stress

AbstractCytochrome bd oxygen reductase from Escherichia coli has three hemes, b558, b595 and d. We found that the enzyme, as-prepared or in turnover with O2, rapidly decomposes H2O2 with formation of approximately half a mole of O2 per mole of H2O2. Such catalase activity vanishes upon cytochrome bd reduction, does not compete with the oxygen-reductase activity, is insensitive to NO, CO, antimycin-A and N-ethylmaleimide (NEM), but is inhibited by cyanide (Ki ∼2.5μM) and azide. The activity, possibly associated with heme-b595, was also observed in catalase-deficient E. coli cells following cytochrome bd over-expression suggesting a protective role against oxidative stress in vivo

Efficiency Comparison of Thermal Insulation Schemes in the Hinged Ventilated Facades Systems

The article deals with the problems associated with the quality of thermal insulation mounting in hinged ventilated facades, and first of all associated with the gaps between thermal insulation panels. According to STO NOSTROY 2.14.67-2012 "Hinged facade systems with air gap. Work on the installation. General requirements for the production and control of work" the acceptable value of the unfilled seam is 2 mm. In reality, it is impossible to achieve the required width of the gap between the plates, and additional heat losses appear on single-layer thermal insulation schemes. The influence of the gaps between thermal insulation plates on the reduced total thermal resistance of the external wall with the hinged ventilated facade system is estimated using Russian and European calculation methods. The calculations were made in accordance with SP 50.13330.2012, SP 230.1325800.2015 and EN ISO 6946. Two outer wall constructions made of monolithic reinforced concrete and masonry from aerated concrete blocks and three options for insulation – single-layered and two double-layered – were adopted for the analysis. Optimal variants of thermal insulation and types of bases for fixing thermal insulation are offered. Three types of air layers are reviewed according to EN ISO 6946, and the third type – highly ventilated layer – is taken to calculations. The results of calculations of two-dimensional temperature fields, linear heat transfer coefficients, heat transfer performance uniformity factors and reduced total thermal resistances for 16 combinations of gaps in thermal insulation and bases are presented

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in oneelectron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (t,1.5 ms) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (t,16 ms). It returns from the b-hemes to heme d with t,180 ms. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (t,16 ms) yielding a transient hexacoordinate state (CO-Fe2+ -L). Then the ligand slowly (t,30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (t,20 ms), some heme b558 (t,0.2–3 ms), and finally migrates from heme d to heme b595 (t,24 ms) in ,5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions

Программное обеспечение для обработки научных исследований влияния окружающей среды на орнитофауну г. Вольнянск

The article provides a detailed description he materials, instruments and technological tools that he uses in the research of avifauna in Vilnyansk. On the basis of the analysis of scientific sources during the autumn, winter and spring accounting of avifauna of accounting sites of the city the methods of average maximum hearing of birds, route methods of accounting, cartographic and combined accounting were applied. In the processing of statistical and graphical data, the software package Microsoft Office, a collection of audio files, GIS products technologies Google Earth, Google Maps, Photoshop and applied software STATISTICA. When building maps for Vilnyansk town, taking into account its physical and geographical features, were used products Google Maps and Google Earth, which allowed to create a map of the city divided by squares 500x500meters to account the areas of observation, as well as to make calculations of the size of the areas of these biotopes, in which there was a record of birds. Using STATISTICA package allowed to establish the dependence of individuals, species diversity of avifauna on environmental factors and factors (temperature characteristics, dates of observations), to establish correlation indicators, as well as the dynamics of the number of birds. Thanks to the effects of the Google Earth program, a detailed analysis of the city facilities (social infrastructure, both part of the residential and natural landscapes) was carried out. As a result of these studies, a general mapping of the bird observation area was created, the sizes of habitats were calculated for the subsequent drawing of individuals of one species or another in their areas, taking into account the elements of the urban landscapes (private development areas, northern part of the city, central and southern areas), dynamics analysis the number of birds during the autumn-winter period 2017/2018 and established correlation coefficients that allowed establishing a relationship between ambient temperature, weather conditions and population disappeared.У статті наведено опис інформаційних технологій, які було використано у процесі дослідження орнітофауни м. Вільнянськ Запорізької обл. На основі аналізу наукових джерел під час осінньо-зимового обліку орнітофауни застосовувались методи маршрутного (прокладення транссект на короткі та довгі відстані), картографічного (створення мап пробних ділянок та нанесення на них особин з визначенням їх щільності) і комбінованого (поєднання елементів двох попередніх) обліку. У процесі оброблювання даних було застосовано програмне забезпечення пакету Microsoft Office, Google Earth, Google Maps і статистичний пакет STATISTICA. У результаті цих досліджень було створено загальну картосхему району спостережень за птахами, розраховані розміри площ біотопів для подальшого нанесення особин на їх ділянки з урахуванням елементів урболандшафтів, проведено аналіз динаміки чисельності птахів за осінньо-зимовий період 2017/2018 рр. та визначено коефіцієнти кореляції, які дозволили встановити залежність між температурою і метеоумовами та популяційними показниками.В статье приведено описание информационных технологий, которые были использованы в процессе исследования орнитофауны г. Вольнянск Запорожской обл. На основе анализа научных источников во время осенне-зимнего учета орнитофауны применялись методы маршрутного (прокладка транссект на малые и большие расстояния), картографического (создание карт пробных участков и нанесения на них особей с определением их плотности) и комбинированного (сочетание элементов двух предыдущих) учета. В процессе обработки данных было применено программное обеспечение пакета Microsoft Office, а также Google Earth, Google Maps и статистический пакет STATISTICA. В результате этих исследований была создана общая картосхема района наблюдений за птицами, рассчитаны размеры площадей биотопов для дальнейшего нанесения особей на их участки с учетом элементов урболандшафтов, проведен анализ динамики численности птиц за осенне-зимний период 2017/2018 гг. и определены коэффициенты корреляции, которые позволили установить зависимость между температурой и метеоусловиями и популяционными показателями

Impact of Hydrogen Sulfide on Mitochondrial and Bacterial Bioenergetics

This review focuses on the effects of hydrogen sulfide (H2S) on the unique bioenergetic molecular machines in mitochondria and bacteria—the protein complexes of electron transport chains and associated enzymes. H2S, along with nitric oxide and carbon monoxide, belongs to the class of endogenous gaseous signaling molecules. This compound plays critical roles in physiology and pathophysiology. Enzymes implicated in H2S metabolism and physiological actions are promising targets for novel pharmaceutical agents. The biological effects of H2S are biphasic, changing from cytoprotection to cytotoxicity through increasing the compound concentration. In mammals, H2S enhances the activity of FoF1-ATP (adenosine triphosphate) synthase and lactate dehydrogenase via their S-sulfhydration, thereby stimulating mitochondrial electron transport. H2S serves as an electron donor for the mitochondrial respiratory chain via sulfide quinone oxidoreductase and cytochrome c oxidase at low H2S levels. The latter enzyme is inhibited by high H2S concentrations, resulting in the reversible inhibition of electron transport and ATP production in mitochondria. In the branched respiratory chain of Escherichia coli, H2S inhibits the bo3 terminal oxidase but does not affect the alternative bd-type oxidases. Thus, in E. coli and presumably other bacteria, cytochrome bd permits respiration and cell growth in H2S-rich environments. A complete picture of the impact of H2S on bioenergetics is lacking, but this field is fast-moving, and active ongoing research on this topic will likely shed light on additional, yet unknown biological effects