| hydrogen bonds between nitrogen donors and the semiquinone in the q(b) site of bacterial reaction centers. | photosynthetic reaction centers from rhodobacter sphaeroides have identical ubiquinone-10 molecules functioning as primary (q(a)) and secondary (q(b)) electron acceptors. x-band 2d pulsed epr spectroscopy, called hyscore, was applied to study the interaction of the q(b) site semiquinone with nitrogens from the local protein environment in natural and (15)n uniformly labeled reactions centers. (14)n and (15)n hyscore spectra of the q(b) semiquinone show the interaction with two nitrogens carrying ... | 2010 | 20672818 |
| primary electron transfer in reaction centers of ym210l and ym210l/hl168l mutants of rhodobacter sphaeroides. | the role of tyrosine m210 in charge separation and stabilization of separated charges was studied by analyzing of the femtosecond oscillations in the kinetics of decay of stimulated emission from p* and of a population of the primary charge separated state p(+)b(a)(-) in ym210l and ym210l/hl168l mutant reaction centers (rcs) of rhodobacter sphaeroides in comparison with those in native rba. sphaeroides rcs. in the mutant rcs, tyrm210 was replaced by leu. the hl168l mutation placed the redox pote ... | 2010 | 20673206 |
| the ppaa/aerr regulators of photosynthesis gene expression from anoxygenic phototrophic proteobacteria contain heme-binding schic domains. | the schic domain of the b12-binding domain family present in the rhodobacter sphaeroides appa protein binds heme and senses oxygen. here we show that the predicted schic domain ppaa/aerr regulators also bind heme and respond to oxygen in vitro, despite their low sequence identity with appa. | 2010 | 20675482 |
| study of interactions between mycobacterium tuberculosis proteins: sigk and anti-sigk. | the development of novel antituberculosis therapeutic molecules is a global health concern. complex gene expression in mycobacterium tuberculosis is mediated mainly by various sigma factors. the sigk protein binds to rna polymerase, facilitating the expression of genes encoding the antigenic proteins mpt70 and mpt83. the anti-sigk protein is a negative regulator of sigk and inhibits the initiation of transcription. this study focuses on the interactions between sigk and the n-terminal domain of ... | 2011 | 20676709 |
| effects of karaya saponin and rhodobacter capsulatus on yolk cholesterol in laying hens. | 1. it has been reported that karaya saponin and rhodobacter capsulatus individually have hypocholesterolaemic activity in laying hens. this study focuses on the effect of adding karaya saponin with r. capsulatus to hen's diet with regard to serum and egg yolk cholesterol and triglycerides. 2. a total of 56 boris brown laying hens were divided into 7 groups at 20 weeks of age. combinations of 25, 50, 75 mg kg(-1) karaya saponin and r. capsulatus 200 and 400 mg kg(-1) were used as treatment groups ... | 2010 | 20680876 |
| field evidence for the potential of rhodobacter capsulatus as biofertilizer for flooded rice. | in a previous study, we evaluated the effects of inoculating rice plants with the phototrophic purple nonsulfur bacterium rhodobacter capsulatus (rc) on growth and yield of rice in pots and lysimeter experiments and the results obtained have been highly encouraging. in this study, we carried out two field experiments: one in the experimental farm of the faculty of agriculture, fayoum university, and the second in a farmer's field in kafr el-sheikh, to assess the effects of rc on growth and yield ... | 2011 | 20697715 |
| multiconformation continuum electrostatics analysis of the effects of a buried asp introduced near heme a in rhodobacter sphaeroides cytochrome c oxidase. | cytochrome c oxidase (cco) reduces o(2) to water via a series of proton-coupled electron transfers, generating a transmembrane electrochemical gradient. coupling electron and proton transfer requires changing the pk(a) values of buried residues at each stage in the reaction cycle. heme a is a key cofactor in the cco electron transfer chain. mutation of ser44 to asp has been reported [mills, d. a., et al. (2008) biochemistry 47, 11499-11509], changing the hydrogen bond acceptor from his102, the h ... | 2010 | 20701325 |
| the simulation of interquinone charge transfer in a bacterial photoreaction center highlights the central role of a hydrogen-bonded non-heme iron complex. | we consider electron transfer between the quinones q(a) and q(b), one of the final steps in the photoinduced charge separation in the photoreaction center of rhodobacter sphaeroides. the system is described by a model with atomic resolution using classical force fields and a carefully parameterized tight-binding hamiltonian. the rates estimated for direct interquinone charge transfer hopping involving a non-heme iron complex bridging the quinones and superexchange based on the geometry of the ph ... | 2011 | 20709018 |
| immobilization of porphyrin derivatives with a defined distance and orientation onto a gold electrode using synthetic light-harvesting α-helix hydrophobic polypeptides. | molecular assembly of zn-porphyrin pigments on a gold electrode using synthetic 1α-helix hydrophobic polypeptides which have similar amino acid sequences to the hydrophobic core in the native photosynthetic light-harvesting (lh) 1-β polypeptide from rhodobacter sphaeroides has been achieved. this method is clearly successful in allowing assembly of porphyrins together with lh1 type functional complexes with a defined distance and orientation on the electrode. in this case, the photocurrent direc ... | 2010 | 20735025 |
| native architecture of the photosynthetic membrane from rhodobacter veldkampii. | the photosynthetic membrane in purple bacteria contains several pigment-protein complexes that assure light capture and establishment of the chemiosmotic gradient. the bioenergetic tasks of the photosynthetic membrane require the strong interaction between these various complexes. in the present work, we acquired the first images of the native outer membrane architecture and the supramolecular organization of the photosynthetic apparatus in vesicular chromatophores of rhodobacter (rb.) veldkampi ... | 2011 | 20797440 |
| chlorophyll biosynthesis: spotlight on protochlorophyllide reduction. | photosynthetic organisms require chlorophyll or bacteriochlorophyll for their light trapping and energy transduction activities. the biosynthetic pathways of chlorophyll and bacteriochlorophyll are similar in most of their early steps, except for the reduction of protochlorophyllide (pchlide) to chlorophyllide. whereas angiosperms make use of a light-dependent enzyme, cyanobacteria, algae, bryophytes, pteridophytes and gymnosperms contain an additional, light-independent enzyme dubbed dark-opera ... | 2010 | 20801074 |
| modeling chemotaxis reveals the role of reversed phosphotransfer and a bi-functional kinase-phosphatase. | understanding how multiple signals are integrated in living cells to produce a balanced response is a major challenge in biology. two-component signal transduction pathways, such as bacterial chemotaxis, comprise histidine protein kinases (hpks) and response regulators (rrs). these are used to sense and respond to changes in the environment. rhodobacter sphaeroides has a complex chemosensory network with two signaling clusters, each containing a hpk, chea. here we demonstrate, using a mathematic ... | 2010 | 20808885 |
| in situ identification and imaging of bacterial polymer nanogranules by infrared nanospectroscopy. | we have employed atomic force microscope-based infrared spectroscopy (afm-ir) to spatially map energy storage polymers inside individual bacteria rhodobacter capsulatus. afm-ir allows chemical mapping of sub-cellular features with a spatial resolution of <100 nm. we have used key absorption bands of the energy storage polymer polyhydroxybutyrate (phb) known from ftir to spatially map the molecular distribution of phb inside bacteria. we have also compared ftir measurements on bulk phb with afm-i ... | 2010 | 20820491 |
| identification of a gene essential for protoporphyrinogen ix oxidase activity in the cyanobacterium synechocystis sp. pcc6803. | protoporphyrinogen oxidase (protox) catalyses the oxidation of protoporphyrinogen ix to protoporphyrin ix during the synthesis of tetrapyrrole molecules. protox is encoded by the hemy gene in eukaryotes and by the hemg gene in many γ-proteobacteria, including escherichia coli. it has been suggested that other bacteria possess a yet unidentified type of protox. to identify a unique bacterial gene encoding protox, we first introduced the arabidopsis hemy gene into the genome of the cyanobacterium, ... | 2010 | 20823222 |
| catellibacterium caeni sp. nov., and reclassification of rhodobacter changlensis anil kumar et al. 2007 as catellibacterium changlense comb. nov. | a novel non-sporulating, non-motile, catalase- and oxidase-positive, strictly aerobic, gram-negative, rod-shaped bacterial strain, designated dca-1t, was isolated from activated sludge collected from a butachlor wastewater treatment facility. the strain was able to degrade about 85 % of 100 mg l-1 butachlor within 5 days incubation. growth occurred in the presence of 0-6 % (w/v) nacl [optimum, 1 % (w/v) nacl] and at ph 5.5-9.0 (optimum, ph 7.0) and at 15-35 °c (optimum, 25-30°c). vesicular inter ... | 2010 | 20833880 |
| bacterial photosynthetic reaction centers in trehalose glasses: coupling between protein conformational dynamics and electron-transfer kinetics as studied by laser-flash and high-field epr spectroscopies. | the coupling between electron transfer (et) and the conformational dynamics of the cofactor−protein complex in photosynthetic reaction centers (rcs) from rhodobacter sphaeroides in water/glycerol solutions or embedded in dehydrated poly(vinyl alcohol) (pva) films or trehalose glasses is reported. matrix effects were studied by time-resolved 95 ghz high-field electron paramagnetic resonance (epr) spectroscopy at room (290 k) and low (150 k) temperature. et from the photoreduced quinone acceptor ( ... | 2010 | 20839819 |
| a rhodobacter capsulatus member of a universal permease family imports molybdate and other oxyanions. | molybdenum (mo) is an important trace element that is toxic at high concentrations. to resolve the mechanisms underlying mo toxicity, rhodobacter capsulatus mutants tolerant to high mo concentrations were isolated by random transposon tn5 mutagenesis. the insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. during growth under mo-replete conditions, the wild-type strain accumulated consid ... | 2010 | 20851900 |
| novel activity of rhodobacter sphaeroides spheroidene monooxygenase crta expressed in escherichia coli. | the spheroidene monooxygenase crta of rhodobacter sphaeroides introduces a keto group and/or hydroxy group at the ends of nonnative substrates in escherichia coli, resulting in the production of novel oxocarotenoids. the heme-containing crta is not a p450 enzyme but a new type of oxygenase. | 2010 | 20851979 |
| aniline-induced tryptophan production and identification of indole derivatives from three purple bacteria. | growth on aniline by three purple non-sulfur bacteria (rhodospirillum rubrum atcc 11170, rhodobacter sphaeroides dsm 158, and rubrivivax benzoatiliticus ja2) as nitrogen, or carbon source could not be demonstrated. however in its presence, production of indole derivatives was observed with all the strains tested. at least 14 chromatographically (hplc) distinct peaks were observed at the absorption maxima of 275-280 nm from aniline induced cultures. five major indoles were identified based on hpl ... | 2010 | 20852980 |
| a bipartite s unit of an ecf-type cobalt transporter. | ecf-class transporters comprise abundant importers for micronutrients such as vitamins and transition-metal ions, and for intermediates of salvage pathways in bacteria and archaea. they are composed of abc atpases (a units), a conserved transmembrane protein (t unit) and a substrate-specific transmembrane protein (s unit or core transporter). here we analyzed the function of an ecf-type co(2+) transporter (cbimnqo) and, in particular, the derived bipartite s unit cbimn. cbimn was characterized a ... | 2010 | 20868747 |
| biotechnological potential of the ethylmalonyl-coa pathway. | the ethylmalonyl-coa pathway is central to the carbon metabolism of many α-proteobacteria, like rhodobacter sphaeroides and methylobacterium extorquens as well as actinomycetes, like streptomyces spp. its function is to convert acetyl-coa, a central carbon intermediate, to other precursor metabolites for cell carbon biosynthesis. in contrast to the glyoxylate cycle--another widely distributed acetyl-coa assimilation strategy--the ethylmalonyl-coa pathway contains many unique coa-ester intermedia ... | 2010 | 20882276 |
| effects of light/dark cycle, mixing pattern and partial pressure of h2 on biohydrogen production by rhodobacter sphaeroides zx-5. | the effects of light/dark cycle, mixing pattern and partial pressure of h2 on the growth and hydrogen production of rhodobacter sphaeroides zx-5 were investigated. the results from light/dark cycle culture showed that little or no hydrogen production was observed during the dark periods, and the hydrogen production immediately recovered once illumination was resumed. also, it was found that the optimum condition of shaking velocity was 120 rpm for hydrogen photo-fermentation. meanwhile, shaking ... | 2010 | 20884205 |
| the flagellar protein flil is essential for swimming in rhodobacter sphaeroides. | in this work we characterize the function of the flagellar protein flil in rhodobacter sphaeroides. our results show that flil is essential for motility in this bacterium and that in its absence flagellar rotation is highly impaired. a green fluorescent protein (gfp)-flil fusion forms polar and lateral fluorescent foci that show different spatial dynamics. the presence of these foci is dependent on the expression of the flagellar genes controlled by the master regulator fleq, suggesting that add ... | 2010 | 20889747 |
| complex prokaryotic genome structure: rapid evolution of chromosome ii. | although many bacteria with two chromosomes have been sequenced, the roles of such complex genome structuring are still unclear. to uncover levels of chromosome i (ci) and chromosome ii (cii) sequence divergence, mauve 2.2.0 was used to align the ci- and cii-specific sequences of bacteria with complex genome structuring in two sets of comparisons: the first set was conducted among the ci and cii of bacterial strains of the same species, while the second set was conducted among the ci and cii of ... | 2010 | 20924417 |
| opposing structural changes in two symmetrical polypeptides bring about opposing changes to the thermal stability of a complex integral membrane protein. | the relationship between membrane protein structure and thermal stability has been examined in the reaction centre from the bacterium rhodobacter sphaeroides, a complex membrane protein comprising three polypeptide chains and 10 cofactors. the core of this protein exhibits an approximate twofold symmetry, the cofactors being held in two membrane-spanning branches by two polypeptides, termed l and m, that have very similar folds. in assays of the thermal stability of wild-type and mutant reaction ... | 2010 | 20933495 |
| histidine is involved in coupling proton uptake to electron transfer in photosynthetic proteins. | in photosynthesis, the central step in transforming light energy into chemical energy is the coupling of light-induced electron transfer to proton uptake and release. despite intense investigations of different photosynthetic protein complexes, including the photosystem ii (ps ii) in plants and the reaction center (rc) in bacteria, the molecular details of this fundamental process remain incompletely understood. in the rc of rhodobacter (rb.) sphaeroides, fast formation of the charge separated s ... | 2010 | 20934775 |
| experimental evidence that the membrane-spanning helix of pufx adopts a bent conformation that facilitates dimerisation of the rhodobacter sphaeroides rc-lh1 complex through n-terminal interactions. | the pufx polypeptide is an integral component of some photosynthetic bacterial reaction center-light harvesting 1 (rc-lh1) core complexes. many aspects of the structure of pufx are unresolved, including the conformation of its long membrane-spanning helix and whether c-terminal processing occurs. in the present report, nmr data recorded on the rhodobacter sphaeroides pufx in a detergent micelle confirmed previous conclusions derived from equivalent data obtained in organic solvent, that the α-he ... | 2010 | 20937243 |
| the electron transfer flavoprotein: ubiquinone oxidoreductases. | electron transfer flavoprotein: ubiqionone oxidoreductase (etf-qo) is a component of the mitochondrial respiratory chain that together with electron transfer flavoprotein (etf) forms a short pathway that transfers electrons from 11 different mitochondrial flavoprotein dehydrogenases to the ubiquinone pool. the x-ray structure of the pig liver enzyme has been solved in the presence and absence of a bound ubiquinone. this structure reveals etf-qo to be a monotopic membrane protein with the cofacto ... | 2010 | 20937244 |
| redox homeostasis phenotypes in rubisco-deficient rhodobacter sphaeroides via ensemble modeling. | photosynthetic bacteria are capable of carrying out the fundamental biological processes of carbon dioxide assimilation and photosynthesis. in this work, ensemble modeling (em) was used to examine the behavior of mutant strains of the nonsulfur purple photosynthetic bacterium rhodobacter sphaeroides containing a blockage in the primary co(2) assimilatory pathway, which is responsible for cellular redox balance. when the calvin-benson-bassham (cbb) pathway is nonfunctional, spontaneous adaptive m ... | 2010 | 20939096 |
| the putative assembly factor ccoh is stably associated with the cbb3-type cytochrome oxidase. | cytochrome oxidases are perfect model substrates for analyzing the assembly of multisubunit complexes because the need for cofactor incorporation adds an additional level of complexity to their assembly. cbb(3)-type cytochrome c oxidases (cbb(3)-cox) consist of the catalytic subunit ccon, the membrane-bound c-type cytochrome subunits ccoo and ccop, and the ccoq subunit, which is required for cbb(3)-cox stability. biogenesis of cbb(3)-cox proceeds via ccoqp and ccono subcomplexes, which assemble ... | 2010 | 20952576 |
| measurement of uroporphyrinogen decarboxylase activity. | uroporphyrinogen decarboxylase (urod) catalyzes decarboxylation of the four acetate side chains of urophyrinogen to form coproporphyrinogen. activity of urod can be measured using an enzymatically prepared substrate or a chemically prepared one. for the former, bacterial porphobilinogen deaminase is prepared and used to prepare the porphyrinogen substrate for the enzymatic assay. erythrocyte lysates can be used to measure hemoglobin content as an indicator of urod activity. | 2001 | 20954157 |
| bchj and bchm interact in a 1 : 1 ratio with the magnesium chelatase bchh subunit of rhodobacter capsulatus. | substrate channeling between the enzymatic steps in the (bacterio)chlorophyll biosynthetic pathway catalyzed by magnesium chelatase (bchi/chli, bchd/chld and bchh/chlh subunits) and s-adenosyl-l-methionine:magnesium-protoporphyrin ix o-methyltransferase (bchm/chlm) has been suggested. this involves delivery of magnesium-protoporphyrin ix from the bchh/chlh subunit of magnesium chelatase to bchm/chlm. stimulation of bchm/chlm activity by bchh/chlh has previously been shown, and physical interacti ... | 2010 | 20955518 |
| sans investigation of the photosynthetic machinery of chloroflexus aurantiacus. | green photosynthetic bacteria harvest light and perform photosynthesis in low-light environments, and contain specialized antenna complexes to adapt to this condition. we performed small-angle neutron scattering (sans) studies to obtain structural information about the photosynthetic apparatus, including the peripheral light-harvesting chlorosome complex, the integral membrane light-harvesting b808-866 complex, and the reaction center (rc) in the thermophilic green phototrophic bacterium chlorof ... | 2010 | 20959079 |
| electrochemical shift of the carotenoid molecule absorption band as an indicator of processes of energy migration in the reaction center of rhodobacter sphaeroides. | | 2010 | 20960251 |
| intricate role of water in proton transport through cytochrome c oxidase. | cytochrome c oxidase (cytco), the final electron acceptor in the respiratory chain, catalyzes the reduction of o(2) to h(2)o while simultaneously pumping protons across the inner mitochondrial or bacterial membrane to maintain a transmembrane electrochemical gradient that drives, for example, atp synthesis. in this work mutations that were predicted to alter proton translocation and enzyme activity in preliminary computational studies are characterized with extensive experimental and computation ... | 2010 | 20964330 |
| the role of electrode curvature in controlling electron transfer between the photosynthetic reaction center protein and gold nanoelectrodes. | | 2010 | 20973026 |
| culturable rhodobacter and shewanella species are abundant in estuarine turbidity maxima of the columbia river. | measurements of dissolved, ascorbate-reducible and total mn by icp-oes revealed significantly higher concentrations during estuarine turbidity maxima (etm) events, compared with non-events in the columbia river. most probable number (mpn) counts of mn-oxidizing or mn-reducing heterotrophs were not statistically different from that of other heterotrophs (10³ -10⁴ cells ml⁻¹) when grown in defined media, but counts of mn oxidizers were significantly lower in nutrient-rich medium (13 cells ml⁻¹). m ... | 2010 | 20977571 |
| cobalt hexaamine mediated electrocatalytic voltammetry of dimethyl sulfoxide reductase: driving force effects on catalysis. | the bacterial molybdoenzyme dimethyl sulfoxide (dmso) reductase from rhodobacter capsulatus catalyzes the reduction of dmso to dimethyl sulfide in anaerobic respiration. in its native state, dmso reductase is reduced to its active state by a pentaheme cytochrome (dorc). alternatively, we show that dmso reductase catalysis may be driven electrochemically using a series of homologous coordination compounds as mediating synthetic electron donors. all mediators are macrocyclic hexaaminecobalt(ii) co ... | 2010 | 20978811 |
| maltose-neopentyl glycol (mng) amphiphiles for solubilization, stabilization and crystallization of membrane proteins. | the understanding of integral membrane protein (imp) structure and function is hampered by the difficulty of handling these proteins. aqueous solubilization, necessary for many types of biophysical analysis, generally requires a detergent to shield the large lipophilic surfaces of native imps. many proteins remain difficult to study owing to a lack of suitable detergents. we introduce a class of amphiphiles, each built around a central quaternary carbon atom derived from neopentyl glycol, with h ... | 2010 | 21037590 |
| tandem facial amphiphiles for membrane protein stabilization. | we describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles. | 2010 | 21049926 |
| ubiquinol formation in isolated photosynthetic reaction centres monitored by time-resolved differential ftir in combination with 2d correlation spectroscopy and multivariate curve resolution. | two-dimensional correlation analysis was carried out in combination with multivariate curve resolution-alternating least squares (mcr-als) to analyse time-resolved infrared (ir) difference spectra probing photoinduced ubiquinol formation in detergent-isolated reaction centres from rhodobacter sphaeroides. the dynamic 2d ir correlation spectra have not only allowed the determination of the concomitance or non-concomitance of different chemical events through known marker bands but also have helpe ... | 2011 | 21061002 |
| [hydrogen release by recombinant strains of rhodobacter sphaeroides using a modified photosynthetic apparatus]. | hydrogen release by recombinant strains of rhodobacter sphaeroides prk puf dd13 without a peripheral light-harvesting antenna complex and prk puf deltalm1 which is able to synthesize both antenna complexes, both of which were grown in conditions of nitrogen limitation, has been studied. the velocity of hydrogen release depended on light intensity. at high cell concentration (0.91 g l(-1)) of prk puf dd 13, velocity was maximal at 2270 w m(-2) and was equal to 144.7 ml l(-1) h(-1) that evidences ... | 2010 | 21061598 |
| rhodobase, a meta-analytical tool for reconstructing gene regulatory networks in a model photosynthetic bacterium. | we present rhodobase, a web-based meta-analytical tool for analysis of transcriptional regulation in a model anoxygenic photosynthetic bacterium, rhodobacter sphaeroides. the gene association meta-analysis is based on the pooled data from 100 of r. sphaeroides whole-genome dna microarrays. gene-centric regulatory networks were visualized using the starnet approach (jupiter, d.c., vanburen, v., 2008. a visual data mining tool that facilitates reconstruction of transcription regulatory networks. p ... | 2010 | 21070832 |
| a q63e rhodobacter sphaeroides appa bluf domain mutant is locked in a pseudo-light-excited signaling state. | the appa bluf photoreceptor from rhodobacter sphaeroides contains a conserved key residue, gln63, that is thought to undergo a shift in hydrogen-bonding interactions when a bound flavin is light excited. in this study we have characterized two substitution mutants of gln63 (q63e, q63l) in the context of two constructs of the bluf domain that have differing lengths, appa1-126 and appa17-133. q63l mutations in both constructs exhibit a blue-shifted flavin absorption spectrum as well as a loss of t ... | 2010 | 21082791 |
| electron-nuclear and electron-electron double resonance spectroscopies show that the primary quinone acceptor qa in reaction centers from photosynthetic bacteria rhodobacter sphaeroides remains in the same orientation upon light-induced reduction. | reaction centers (rcs) from the photosynthetic bacterium rhodobacter (rb.) sphaeroides r-26 exhibit changes in the recombination kinetics of the charge-separated radical-pair state, p(·+) q(a)(·-), composed of the dimeric bacteriochlorophyll donor p and the ubiquinone-10 acceptor q(a), depending on whether the rcs are cooled to cryogenic temperatures in the dark or under continuous illumination (kleinfeld et al. biochemistry 1984, 23, 5780-5786). structural changes near redox-active cofactors ha ... | 2010 | 21090818 |
| stereoisomeric separation of some flavanones using highly succinate-substituted α-cyclosophoro-octadecaoses as chiral additives in capillary electrophoresis. | α-cyclosophoro-octadecaoses (α-c18), produced by rhodobacter sphaeroides, are mostly homogeneous in size with 18 glucose units per ring as the predominant form. α-c18s are linked by β-(1→4)-linkages and one α-(1→6)-linkage and are also known to be highly substituted by acetyl (0-2 per mol) and/or succinoyl groups (1-7 per mol). we isolated and purified α-c18 and successfully used it in capillary electrophoresis (ce) as a chiral additive for the separation of five flavanones and flavanone-7-o-gly ... | 2010 | 21093852 |
| acetate-dependent photoheterotrophic growth and the differential requirement for the calvin-benson-bassham reductive pentose phosphate cycle in rhodobacter sphaeroides and rhodopseudomonas palustris. | rhodobacter sphaeroides ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco)-deletion strain 16 was capable of photoheterotrophic growth with acetate, while rhodopseudomonas palustris rubisco-deletion strain 2040 could not grow under these conditions. the reason for this difference lies in the fact that rba. sphaeroides and rps. palustris use different pathways for acetate assimilation, the ethylmalonyl-coa pathway, and glyoxylate-bypass cycle, respectively. the ethylmalonyl-coa pathway is ... | 2010 | 21104179 |
| mutagenesis of tyrosine residues within helix vii in subunit i of the cytochrome cbb (3) oxidase from rhodobacter capsulatus. | the cbb (3)-type oxidases are members of the heme-copper oxidase superfamily, distant by sequence comparisons, but sharing common functional characteristics. the cbb (3) oxidases are missing an active-site tyrosine residue that is absolutely conserved in all a and b-type heme-copper oxidases. this tyrosine is known to play a critical role in the catalytic mechanisms of a and b-type oxidases. the absence of this tyrosine in the cbb (3) oxidases raises the possibility that the cbb (3) oxidases uti ... | 2010 | 21107730 |
| anoxygenic photosynthesis and photooxidative stress: a particular challenge for roseobacter. | roseobacter clade aerobic anoxygenic phototrophic bacteria (aanp) are abundant in photic zone environments of marine ecosystems. these bacteria form a photosynthetic apparatus at oxygen saturation, a situation expected to generate high levels of singlet oxygen (¹o₂) when light is present. rhodobacter sphaeroides, an anaerobic anoxygenic phototroph, represses photosynthesis genes at high oxygen tension. here we report that roseobacter denitrificans showed higher sensitivity to ¹o₂ compared with r ... | 2010 | 21108722 |
| on the midpoint potential of the fad chromophore in a bluf-domain containing photoreceptor protein. | the redox-midpoint potential of the fad chromophore in the bluf domain of anti-transcriptional regulator appa from rhodobacter sphaeroides equals ∼-260mv relative to the calomel electrode. altering the structure of its chromophore-binding pocket through site-directed mutagenesis brings this midpoint potential closer to that of free flavin in aqueous solution. the redox-midpoint potential of this bluf domain is intermediate between those of lov domains and cryptochromes, which may rationalize the ... | 2010 | 21110976 |
| bridging the gap: linking molecular simulations and systemic descriptions of cellular compartments. | metabolic processes in biological cells are commonly either characterized at the level of individual enzymes and metabolites or at the network level. often these two paradigms are considered as mutually exclusive because concepts from neither side are suited to describe the complete range of scales. additionally, when modeling metabolic or regulatory cellular systems, often a large fraction of the required kinetic parameters are unknown. this even applies to such simple and extensively studied s ... | 2010 | 21124924 |
| epr study of 1asp-3cys ligated 4fe-4s iron-sulfur cluster in nb-protein (bchn-bchb) of a dark-operative protochlorophyllide reductase complex. | dark-operative protochlorophyllide oxidoreductase, a nitrogenase-like enzyme, contains two [4fe-4s] clusters, one in the l-protein ((bchl)(2)) and the other in the nb-protein ((bchn-bchb)(2)). the reduced nb-cluster in the nb-protein, which is ligated by 1asp/3cys residues, showed a broad s=3/2 electron paramagnetic resonance signal that is rather rare in [4fe-4s] clusters. a 4cys-ligated nb-cluster in the mutated variant bchb-d36c protein, in which the asp36 was replaced by a cys, gave a rhombi ... | 2010 | 21126521 |
| [influence of ldao on the conformation and release of bacteriochlorophyll of peripheral light-harvesting complex (lh2) from rhodobacter azotoformans]. | the aim of this study is to reveal the interaction relationships between lauryl dimethylamine n-oxide (ldao) and peripheral light-harvesting complex (lh2) as well as the influence of ldao on structure and function of lh2. in the present work, the effects of ldao on the conformation and release processes of bacteriochlorophyll (bchl) of lh2 when incubated under different temperature and ph in the presence and absence of ldao were investigated by spectroscopy. the results indicated that (1) the pr ... | 2010 | 21137426 |
| cloning, purification and preliminary crystallographic analysis of cobalamin methyltransferases from rhodobacter capsulatus. | of the 30 biosynthetic steps necessary for the production of cobalamin (vitamin b12), eight involve the addition of s-adenosylmethionine-derived methyl groups to the tetrapyrrole framework. these eight methyl additions are catalysed by six canonical methyltransferase domains and one noncanonical methyltransferase domain. recombinant forms of four methyltransferases from rhodobacter capsulatus, cobj, cobm, cobf and cobl, and of the c-terminal noncanonical domain of cobl (cobl-c) have been crystal ... | 2010 | 21139217 |
| light-induced conformational changes in photosynthetic reaction centers: dielectric relaxation in the vicinity of the dimer. | conformational changes near the bacteriochlorophyll dimer induced by continuous illumination were identified in the wild type and 11 different mutants of reaction centers from rhodobacter sphaeroides. the properties of the bacteriochlorophyll dimer, which has a different hydrogen bonding pattern with the surrounding protein in each mutant, were characterized by steady-state and transient optical spectroscopy. after illumination for 1 min, in the absence of the secondary quinone, the recovery of ... | 2010 | 21141811 |
| energy transfer dynamics in an rc-lh1-pufx tubular photosynthetic membrane. | light absorption and the subsequent transfer of excitation energy are the first two steps of the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (bchls), in photosynthetic bacteria. bchls are anchored in light-harvesting (lh) complexes, such as light-harvesting complex i (lh1), which directly associates with the reaction center (rc), forming the rc-lh1 core complex. in rhodobacter sphaeroides, rc-lh1 core complexes contain an additional protein, pufx, a ... | 2010 | 21152381 |
| regb kinase activity is controlled in part by monitoring the ratio of oxidized to reduced ubiquinones in the ubiquinone pool. | regb is a membrane-spanning sensor kinase responsible for redox regulation of a wide variety of metabolic processes in numerous proteobacterial species. here we show that full-length regb purified from escherichia coli membranes contains bound ubiquinone. four conserved residues in the membrane-spanning domain of regb are shown to have important roles in ubiquinone binding in vitro and redox sensing in vivo. isothermal titration calorimetry measurements, coupled with kinase assays under oxidizin ... | 2010 | 21157513 |
| cloning, expression, and physicochemical characterization of a new diheme cytochrome c from shewanella baltica os155. | the 16-kda diheme cytochrome c from the bacterium shewanella baltica os155 (sb-dhc) was cloned and expressed in escherichia coli and investigated through uv-vis, magnetic circular dichroism, and (1)h nmr spectroscopies and protein voltammetry. the model structure was obtained by means of comparative modeling using the x-ray structure of rhodobacter sphaeroides diheme cytochrome c (rs-dhc) (with a 37% pairwise sequence identity) as a template. sb-dhc folds into two distinct domains, each containi ... | 2010 | 21161306 |
| metal/protein ratio determination in the rhodobacter capsulatus cytoplasmic pyrophosphatase enzyme by particle induced x-ray emission. | inorganic pyrophosphatases are divided in two families, which differ both in structure and mechanism. all of them incorporate in its structure divalent metal cations. in 2003, it was reported for the first time that rhodobacter capsulatus cytoplasmic pyrophosphatase belongs to family ii. it is expected then, that this enzyme contains metal elements in its structure; however, this characterization has not been carried out yet. a fine application of accelerators is the use of proton beams to induc ... | 2010 | 21167875 |
| carboxylate shifts steer interquinone electron transfer in photosynthesis. | understanding the mechanisms of electron transfer (et) in photosynthetic reaction centers (rcs) may inspire novel catalysts for sunlight-driven fuel production. the electron exit pathway of type ii rcs comprises two quinone molecules working in series and in between a non-heme iron atom with a carboxyl ligand (bicarbonate in photosystem ii (psii), glutamate in bacterial rcs). for decades, the functional role of the iron has remained enigmatic. we tracked the iron site using microsecond-resolutio ... | 2010 | 21169354 |
| single and multi-exciton dynamics in aqueous protochlorophyllide aggregates. | in plants, the oxidoreductase enzyme por reduces protochlorophyllide (pchlide) into chlorophyllide (chlide), using nadph as a cofactor. the reduction involves the transfer of two electrons and two protons to the c17═c18 double bond of pchlide, and the reaction is initiated by the absorption of light by pchlide itself. in this work we have studied the excited state dynamics of pchlide dissolved in water, where it forms excitonically coupled aggregates, by ultrafast time-resolved transient absorpt ... | 2010 | 21171640 |
| the prevalence of gene duplications and their ancient origin in rhodobacter sphaeroides 2.4.1. | rhodobacter sphaeroides 2.4.1 is a metabolically versatile organism that belongs to α-3 subdivision of proteobacteria. the present study was to identify the extent, history, and role of gene duplications in r. sphaeroides 2.4.1, an organism that possesses two chromosomes. | 2010 | 21192830 |
| control of lipopolysaccharide biosynthesis by ftsh-mediated proteolysis of lpxc is conserved in enterobacteria but not in all gram-negative bacteria. | despite the essential function of lipopolysaccharides (lps) in gram-negative bacteria, it is largely unknown how the exact amount of this molecule in the outer membrane is controlled. the first committed step in lps biosynthesis is catalyzed by the lpxc enzyme. in escherichia coli, the cellular concentration of lpxc is adjusted by the only essential protease in this organism, the membrane-anchored metalloprotease ftsh. turnover of e. coli lpxc requires a length- and sequence-specific c-terminal ... | 2010 | 21193611 |
| light-generated paramagnetic intermediates in bluf domains. | blue-light sensitive photoreceptory bluf domains are flavoproteins, which regulate various, mostly stress-related processes in bacteria and eukaryotes. the photoreactivity of the flavin adenine dinucleotide (fad) cofactor in three bluf domains from rhodobacter sphaeroides, synechocystis sp. pcc 6803 and escherichia coli have been studied at low temperature using time-resolved electron paramagnetic resonance. photoinduced flavin triplet states and radical-pair species have been detected on a micr ... | 2011 | 21198648 |
| crystallographic and online spectral evidence for role of conformational change and conserved water in cytochrome oxidase proton pump. | crystal structures in both oxidized and reduced forms are reported for two bacterial cytochrome c oxidase mutants that define the d and k proton paths, showing conformational change in response to reduction and the loss of strategic waters that can account for inhibition of proton transfer. in the oxidized state both mutants of the rhodobacter sphaeroides enzyme, d132a and k362m, show overall structures similar to wild type, indicating no long-range effects of mutation. in the reduced state, the ... | 2011 | 21205904 |
| evaluation of a semipolar solvent system as a step toward heteronuclear multidimensional nmr-based metabolomics for 13c-labeled bacteria, plants, and animals. | nuclear magnetic resonance (nmr) has become a key technology in metabolomics, with the use of stable isotope labeling and advanced heteronuclear multidimensional nmr techniques. in this paper, we focus on the evaluation of extraction solvents to improve nmr-based methodologies for metabolomics. line broadening is a serious barrier to detecting signals and the annotation of metabolites using multidimensional nmr. we evaluated a series of nmr solvents for easy and versatile single-step extraction ... | 2011 | 21208007 |
| bacterial genome chimaerism and the origin of mitochondria. | many studies have sought to determine the origin and evolution of mitochondria. although the alphaproteobacteria are thought to be the closest relatives of the mitochondrial progenitor, there is dispute as to what its particular sister group is. some have argued that mitochondria originated from ancestors of the order rickettsiales, or more specifically of the rickettsiaceae family, while others believe that ancestors of the family rhodospirillaceae are also equally likely the progenitors. to re ... | 2011 | 21217797 |
| ultrafast infrared spectroscopy of an isotope-labeled photoactivatable flavoprotein. | the blue light using flavin (bluf) domain photosensors, such as the transcriptional antirepressor appa, utilize a noncovalently bound flavin as the chromophore for photoreception. since the isoalloxazine ring of the chromophore is unable to undergo large-scale structural change upon light absorption, there is intense interest in understanding how the bluf protein matrix senses and responds to flavin photoexcitation. light absorption is proposed to result in alterations in the hydrogen-bonding ne ... | 2011 | 21218799 |
| a novel rhodobacter sphaeroides expression system for real-time evaluation of heterologous protein expression levels. | heterologous protein expression levels can not be evaluated in real-time by experimental procedures commonly used for most expression systems during host cell culture. rb. sphaeroides has provided an ideal system for studying both photosynthesis and membrane development and exhibited potential as a novel expression system. we constructed the puc1ba and puc2ba mutant strain rb. sphaeroides cqu68 and used it as a novel expression system to heterologously express proteins fused to β-subunit of ligh ... | 2011 | 21235482 |
| unusual regulation of a leaderless operon involved in the catabolism of dimethylsulfoniopropionate in rhodobacter sphaeroides. | rhodobacter sphaeroides strain 2.4.1 is a widely studied bacterium that has recently been shown to cleave the abundant marine anti-stress molecule dimethylsulfoniopropionate (dmsp) into acrylate plus gaseous dimethyl sulfide. it does so by using a lyase encoded by dddl, the promoter-distal gene of a three-gene operon, acur-acui-dddl. transcription of the operon was enhanced when cells were pre-grown with the substrate dmsp, but this induction is indirect, and requires the conversion of dmsp to t ... | 2011 | 21249136 |
| the temperature dependence of radiationless transition rates from ab initio computations. | the calculation of radiationless transition rates and of their temperature dependence from first principles is addressed by combining reliable electronic computations of the normal modes of the two electronic states with kubo's generating function approach for the evaluation of the franck-condon weighted density of states. the whole sets of normal modes of the involved cofactors have been employed, taking into account the effects of nuclear equilibrium position displacements, of vibrational freq ... | 2011 | 21258672 |
| intermonomer electron transfer between the low-potential b hemes of cytochrome bc₁. | cytochrome (cyt) bc(1) is a structural dimer with its monomers consisting of the fe-s protein, cyt b, and cyt c(1) subunits. its three-dimensional architecture depicts it as a symmetrical homodimer, but the mobility of the head domain of the fe-s protein indicates that the functional enzyme exists in asymmetrical heterodimeric conformations. here, we report a new genetic system for studying intra- and intermonomer interactions within the cyt bc(1) using the facultative phototrophic bacterium rho ... | 2011 | 21261281 |
| all-atom molecular dynamics simulations reveal significant differences in interaction between antimycin and conserved amino acid residues in bovine and bacterial bc1 complexes. | antimycin a is the most frequently used specific and powerful inhibitor of the mitochondrial respiratory chain. we used all-atom molecular dynamics (md) simulations to study the dynamic aspects of the interaction of antimycin a with the q(i) site of the bacterial and bovine bc(1) complexes embedded in a membrane. the md simulations revealed considerable conformational flexibility of antimycin and significant mobility of antimycin, as a whole, inside the q(i) pocket. we conclude that many of the ... | 2011 | 21281587 |
| signal processing in complex chemotaxis pathways. | bacteria use chemotaxis to migrate towards environments that are better for growth. chemoreceptors detect changes in attractant levels and signal through two-component systems to control swimming direction. this basic pathway is conserved across all chemotactic bacteria and archaea; however, recent work combining systems biology and genome sequencing has started to elucidate the additional complexity of the process in many bacterial species. this article focuses on one of the best understood com ... | 2011 | 21283116 |
| dynamic and reversible self-assembly of photoelectrochemical complexes based on lipid bilayer disks, photosynthetic reaction centers, and single-walled carbon nanotubes. | an aqueous solution containing photosynthetic reaction centers (rcs), membrane scaffold proteins (msps), phospholipids, and single-walled carbon nanotubes (swcnts) solubilized with the surfactant sodium cholate (sc) reversibly self-assembles into a highly ordered structure upon dialysis of the latter. the resulting structure is photoelectrochemically active and consists of 4-nm-thick lipid bilayer disks (nanodisks, nds) arranged parallel to the surface of the swcnt with the rc housed within the ... | 2011 | 21291272 |
| features of rhodobacter sphaeroides chrr required for stimuli to promote the dissociation of s(e)/chrr complexes. | in the photosynthetic bacterium rhodobacter sphaeroides, a transcriptional response to the reactive oxygen species singlet oxygen ((1)o(2)) is mediated by chrr, a zinc metalloprotein that binds to and inhibits the activity of the alternative s factor s(e). we provide evidence that (1)o(2) promotes the dissociation of s(e) from chrr to activate transcription in vivo. to identify what is required for (1)o(2) to promote the dissociation of s(e)/chrr complexes, we analyzed the in vivo properties of ... | 2011 | 21295582 |
| catalase activity of cytochrome c oxidase assayed with hydrogen peroxide-sensitive electrode microsensor. | an iron-hexacyanide-covered microelectrode sensor has been used to continuously monitor the kinetics of hydrogen peroxide decomposition catalyzed by oxidized cytochrome oxidase. at cytochrome oxidase concentration ~1 µm, the catalase activity behaves as a first order process with respect to peroxide at concentrations up to ~300-400 µm and is fully blocked by heat inactivation of the enzyme. the catalase (or, rather, pseudocatalase) activity of bovine cytochrome oxidase is characterized by a seco ... | 2010 | 21314602 |
| functional effects of mutations in cytochrome c oxidase related to prostate cancer. | a number of missense mutations in subunit i of cytochrome c oxidase (cytco) have previously been linked to prostate cancer (petros et al., 2005). to investigate the effects of these mutations at the molecular level, in the present study we prepared four different structural variants of the bacterial rhodobacter sphaeroides cytco (cytochrome aa(3)), each carrying one amino-acid residue replacement corresponding to the following substitutions identified in the above-mentioned study: asn11ser, ala1 ... | 2011 | 21334999 |
| alternative initial proton acceptors for the d pathway of rhodobacter sphaeroides cytochrome c oxidase. | to characterize protein structures that control proton uptake, we assayed forms of cytochrome c oxidase (cco) containing a carboxyl or a thiol group in line with the initial, internal waters of the d pathway for proton transfer in the presence and absence of subunit iii. subunit iii provides approximately half of the protein surrounding the entry region of the d pathway. the n139d/d132n mutant contains a carboxyl group 6 å within the d pathway and lacks the normal, surface-exposed proton accepto ... | 2011 | 21344856 |
| xanthine dehydrogenase electrocatalysis: autocatalysis and novel activity. | the enzyme xanthine dehydrogenase (xdh) from the purple photosynthetic bacterium rhodobacter capsulatus catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid as part of purine metabolism. the native electron acceptor is nad(+) but herein we show that uric acid in its 2-electron oxidized form is able to act as an artificial electron acceptor from xdh in an electrochemically driven catalytic system. hypoxanthine oxidation is also observed with the novel production of uric a ... | 2011 | 21361328 |
| the accumulation of the light-harvesting 2 complex during remodeling of the rhodobacter sphaeroides intracytoplasmic membrane results in a slowing of the electron transfer turnover rate of photochemical reaction centers. | a functional proteomic analysis of the intracytoplasmic membrane (icm) development process was performed in rhodobacter sphaeroides during adaptation from high-intensity illumination to indirect diffuse light. this initiated an accelerated synthesis of the peripheral light-harvesting 2 (lh2) complex relative to that of lh1-reaction center (rc) core particles. after 11 days, icm vesicles (chromatophores) and membrane invagination sites were isolated by rate-zone sedimentation and subjected to cle ... | 2011 | 21366273 |
| energetics for oxidation of a bound manganese cofactor in modified bacterial reaction centers. | the energetics of a mn cofactor bound to modified reaction centers were determined, including the oxidation/reduction midpoint potential and free energy differences for electron transfer. to determine these properties, a series of mutants of rhodobacter sphaeroides were designed that have a metal-ion binding site that binds mn2+ with a dissociation constant of 1 µm at ph 9.0 (thielges et al. (2005) biochemistry 44, 7389-7394). in addition to the mn binding site, each mutant had changes near the ... | 2011 | 21375274 |
| influence of the electric field on the electron transport in photosynthetic reaction centers. | the effect of an electric field on the electron transfer in the bacterial reaction centers is investigated. the rate constants and quantum yields affected by the electric field for wild type (wt) and reaction center (rc) mutant of rhodobacter capsulatus were computed. the dependence of the asymmetry of electron transfer in electric field on the temperature was evaluated. we found stable electron transfer for wt of the reaction center towards an electric field in comparison with the f(l121)d muta ... | 2011 | 21380644 |
| thin film voltammetry of wild type and mutant reaction center proteins from photosynthetic bacteria. | photosynthetic reaction centers (rc) convert light into electrical potential via a series of electron transfers between protein-bound, redox-active cofactors. direct voltammetry was used to characterize the rc protein from rhodobacter sphaeroides and mutants with focus on the primary electron donor (p) cofactor. cyclic voltammetry (cv) and square wave voltammetry (swv) of lipid and polyion films of rcs revealed similar chemically irreversible processes, and starting, switching, or preconditionin ... | 2011 | 21384836 |
| expression, purification, crystallization and preliminary x-ray analysis of the dna-binding domain of rhodobacter capsulatus mopb. | the lysr-type regulator mopb represses transcription of several target genes (including the nitrogen-fixation gene anfa) in rhodobacter capsulatus at high molybdenum concentrations. in this study, the isolated dna-binding domain of mopb (mopbhth) was overexpressed in escherichia coli. purified mopbhth bound the anfa promoter as shown by dna mobility-shift assays, demonstrating the function of the isolated regulator domain. mopbhth was crystallized using the sitting-drop vapour-diffusion method i ... | 2011 | 21393847 |
| reversible binding of metal ions onto bacterial layers revealed by protonation-induced atr-ftir difference spectroscopy. | the ability of microorganisms to adhere to abiotic surfaces and the potentialities of attenuated total reflection fourier transform infrared (atr-ftir) spectroscopy have been exploited to study protonation and heavy metal binding events onto bacterial surfaces. this work represents the first attempt to apply on bacteria the recently developed method known as perfusion-induced atr-ftir difference spectroscopy. such a technique allows measurement of even slight changes in the infrared spectrum of ... | 2011 | 21395289 |
| light-induced conformational changes in photosynthetic reaction centers: redox-regulated proton pathway near the dimer. | the influence of the hydrogen bonds on the light-induced structural changes were studied in the wild type and 11 mutants with different hydrogen bonding patterns of the primary electron donor of reaction centers from rhodobacter sphaeroides. previously, using the same set of mutants at ph 8, a marked light-induced change of the local dielectric constant in the vicinity of the dimer was reported in wild type and in mutants retaining leu l131 that correlated with the recovery kinetics of the charg ... | 2011 | 21410139 |
| hydrogen bonding and spin density distribution in the qb semiquinone of bacterial reaction centers and comparison with the qa site. | in the photosynthetic reaction center from rhodobacter sphaeroides, the primary (q(a)) and secondary (q(b)) electron acceptors are both ubiquinone-10, but with very different properties and functions. to investigate the protein environment that imparts these functional differences, we have applied x-band hyscore, a 2d pulsed epr technique, to characterize the exchangeable protons around the semiquinone (sq) in the q(a) and q(b) sites, using samples of (15)n-labeled reaction centers, with the nat ... | 2011 | 21417328 |
| analysis of in situ manganese(ii) oxidation in the columbia river and offshore plume: linking aurantimonas and the associated microbial community to an active biogeochemical cycle. | the columbia river is a major source of dissolved nutrients and trace metals for the west coast of north america. a large proportion of these nutrients are sourced from the columbia river estuary, where coastal and terrestrial waters mix and resuspend particulate matter within the water column. as estuarine water is discharged off the coast, it transports the particulate matter, dissolved nutrients and microorganisms forming nutrient-rich and metabolically dynamic plumes. in this study, bacteria ... | 2011 | 21418498 |
| energy transfer in an lh4-like light harvesting complex from the aerobic purple photosynthetic bacterium roseobacter denitrificans. | a peripheral light-harvesting complex from the aerobic purple bacterium roseobacter (r.) denitrificans was purified and its photophysical properties characterized. the complex contains two types of pigments, bacteriochlorophyll (bchl) a and the carotenoid (car) spheroidenone and possesses unique spectroscopic properties. it appears to lack the b850 bacteriochlorophyll a q(y) band that is typical for similar light-harvesting complex 2 antennas. circular dichroism and low temperature steady-state ... | 2011 | 21419098 |
| reorientation of cytochrome c2 upon interaction with oppositely charged macromolecules probed by sr epr: implications for the role of dipole moment to facilitate collisions in proper configuration for electron transfer. | the reaction of water-soluble cytochrome c (c(2)) with its physiological redox partners is facilitated by electrostatic attractions between the two protein surfaces. using spin-labeled cytochrome c(2) from rhodobacter capsulatus and pulse electron paramagnetic resonance (epr) measurements we compared spatial orientation of cytochrome c(2) upon its binding to surfaces of opposite charge. we observed that cytochrome c(2) can use its negatively charged "back" side when exposed to interact with posi ... | 2011 | 21431229 |
| [effect of chemical chaperones on properties of lysozyme and the reaction center protein from rhodobacter sphaeroides]. | the influence of three chemical chaperones: glycerol, 4-hexylresorcinol, and 5-methylresorcinol on the structure, equilibrium fluctuations, and the functional activity of the hydrophilic enzyme lysozyme and the transmembrane reaction center (rc) protein from rb. sphaeroides in a broad range of concentrations has been studied. selected chemical chaperones are strongly different by the structure and action on hydrophilic and membrane proteins. the influence of the chemical chaperones (except methy ... | 2011 | 21442881 |
| [investigation of the anaerobic metabolism of rhodobacter capsulatus with a flux model]. | a flux model of the anaerobic metabolism of rhodobacter capsulatus related to hydrogen production has been constructed. the performance of this model has been assessed by comparing the computed metabolic fluxes with experimental values obtained by several research groups who worked on various strains of r. capsulatus and utilized different growth setups. we have investigated the photoheterotrophic metabolism of r. capsulatus on acetate and have shown that in this mode the bacterium can produce h ... | 2011 | 21442889 |
| loss of a conserved tyrosine residue of cytochrome b induces reactive oxygen species production by cytochrome bc1. | production of reactive oxygen species (ros) induces oxidative damages, decreases cellular energy conversion efficiencies, and induces metabolic diseases in humans. during respiration, cytochrome bc(1) efficiently oxidizes hydroquinone to quinone, but how it performs this reaction without any leak of electrons to o(2) to yield ros is not understood. using the bacterial enzyme, here we show that a conserved tyr residue of the cytochrome b subunit of cytochrome bc(1) is critical for this process. s ... | 2011 | 21454570 |
| proton-transport mechanisms in cytochrome c oxidase revealed by studies of kinetic isotope effects. | cytochrome c oxidase (cytco) is a membrane-bound enzyme, which catalyzes the reduction of di-oxygen to water and uses a major part of the free energy released in this reaction to pump protons across the membrane. in the rhodobacter sphaeroides aa3 cytco all protons that are pumped across the membrane, as well as one half of the protons that are used for o2 reduction, are transferred through one specific intraprotein proton pathway, which holds a highly conserved glu286 residue. key questions tha ... | 2011 | 21463601 |
| quantum chemical simulations of excited-state absorption spectra of photosynthetic bacterial reaction center and antenna complexes. | the semiempirical zindo/s cis configuration interaction method has been used to study the ground- and excited-state absorption spectra of wild type and heterodimer m202hl reaction centers from purple bacterium rhodobacter sphaeroides as well as of peripheral lh2 and lh3 light harvesting complexes from purple bacterium rhodopseudomonas acidophila. the calculations well reproduce the experimentally observed excited-state absorption spectra between 1000 and 17,000 cm(-1), despite the necessarily li ... | 2011 | 21466178 |
| cardiolipin deficiency in rhodobacter sphaeroides alters the lipid profile of membranes and of crystallized cytochrome oxidase, but structure and function are maintained. | many recent studies highlight the importance of lipids in membrane proteins, including in the formation of well-ordered crystals. to examine the effect of changes in one lipid, cardiolipin, on the lipid profile and the production, function, and crystallization of an intrinsic membrane protein, cytochrome c oxidase, we mutated the cardiolipin synthase (cls) gene of rhodobacter sphaeroides, causing a >90% reduction in cardiolipin content in vivo and selective changes in the abundances of other lip ... | 2011 | 21476578 |
| combined genetic and metabolic manipulation of lipids in rhodobacter sphaeroides reveals non-phospholipid substitutions in fully active cytochrome c oxidase. | a specific requirement for lipids, particularly cardiolipin (cl), in cytochrome c oxidase (cco) has been reported in many previous studies using mainly in vitro lipid removal approaches in mammalian systems. our accompanying paper shows that cco produced in markedly cl-depleted rhodobacter sphaeroides displays wild-type properties in all respects, likely allowed by quantitative substitution with other negatively charged lipids. to further examine the structural basis for the lipid requirements o ... | 2011 | 21476580 |
| excitation-emission polarization spectroscopy of single light harvesting complexes. | excitation and emission polarization dependence of fluorescence intensity of single lh2 complexes from rhodopseudomonas acidophila 10050 and rhodobacter sphaeroides is reported. the results are presented as two-dimensional polarization plots and interpreted in terms of tilted light harvesting complexes indicating that sample preparation leads to partially oriented lh2 cylinders. an alternative explanation of the observation can be structural deformation. fluorescence intensity of the complexes h ... | 2011 | 21486039 |
| carotenoid excited-state properties in photosynthetic purple bacterial reaction centers: effects of the protein environment. | carotenoid excited-state properties are characterized and compared in reaction centers (rcs) of wild-type (wt) rhodobacter (rb.) sphaeroides , and a mutant vr(l157), in which the near-infrared absorbance band associated with the primary electron donor, p, is missing. energy transfer from the carotenoid (spheroidenone) s(2) and relaxed s(1) excited states to an adjacent monomeric-bacteriochlorophyll is unchanged between wt and the mutant rc samples. however, two other excited states, including a ... | 2011 | 21488646 |