Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| comparative study of spectral flexibilities of bacterial light-harvesting complexes: structural implications. | this work presents a comparative study of the frequencies of spectral jumping of individual light-harvesting complexes of six different types: lh2 of rhodopseudomonas acidophila, rhodobacter sphaeroides, and rhodospirillum molischianum; lh1 of rhodobacter sphaeroides; and two "domain swap mutants" of lh2 of rhodobacter sphaeroides: paclh1 and paclh2mol, in which the alpha-polypeptide c-terminus is exchanged with the corresponding sequence from lh1 of rhodobacter sphaeroides or lh2 of rhodospiril ... | 2006 | 16399835 |
| analysis of hemf gene function and expression in rhodobacter sphaeroides 2.4.1. | the hemf gene of rhodobacter sphaeroides 2.4.1 is predicted to code for an oxygen-dependent coproporphyrinogen iii oxidase. we found that a hemf- mutant strain is unable to grow under aerobic conditions. we also determined that hemf expression is controlled by oxygen, which is mediated, at least in part, by the response regulatory protein prra. | 2006 | 16385070 |
| tetrapyrrole biosynthesis in rhodobacter capsulatus is transcriptionally regulated by the heme-binding regulatory protein, hbrl. | we demonstrate that the expression of hem genes in rhodobacter capsulatus is transcriptionally repressed in response to the exogenous addition of heme. a high-copy suppressor screen for regulators of hem gene expression resulted in the identification of an lysr-type transcriptional regulator, called hbrl, that regulates hem promoters in response to the availability of heme. hbrl is shown to activate the expression of hema and hemz in the absence of exogenous hemin and repress hemb expression in ... | 2006 | 16452440 |
| structural and mutagenesis studies on the cytochrome c peroxidase from rhodobacter capsulatus provide new insights into structure-function relationships of bacterial di-heme peroxidases. | cytochrome c peroxidases (ccp) play a key role in cellular detoxification by catalyzing the reduction of hydrogen peroxide to water. the di-heme ccp from rhodobacter capsulatus is the fastest enzyme (1060 s(-1)), when tested with its physiological cytochrome c substrate, among all di-heme ccps characterized to date and has, therefore, been an attractive target to investigate structure-function relationships for this family of enzymes. here, we combine for the first time structural studies with s ... | 2006 | 16314410 |
| effects of substrate analogues and ph on manganese superoxide dismutases. | the effect of the substrate analogues azide and fluoride on the manganese(ii) zero-field interactions of different manganese-containing superoxide dismutases (sod) was measured using high-field electron paramagnetic resonance spectroscopy. two cambialistic types, proteins that are active with manganese or iron, were studied along with two that were only active with iron and another that was only active with manganese. it was found that azide was able to coordinate directly to the pentacoordinate ... | 2006 | 16460038 |
| carotenoid-bacteriochlorophyll energy transfer in lh2 complexes studied with 10-fs time resolution. | in this report, we present a study of carotenoid-bacteriochlorophyll energy transfer processes in two peripheral light-harvesting complexes (known as lh2) from purple bacteria. we use transient absorption spectroscopy with approximately 10 fs temporal resolution, which is necessary to observe the very fast energy relaxation processes. by comparing excited-state dynamics of the carotenoids in organic solvents and inside the lh2 complexes, it has been possible to directly evaluate their energy tra ... | 2006 | 16428274 |
| identification of two gene loci involved in poly-beta-hydroxybutyrate production in rhodobacter sphaeroides fj1. | polyhydroxyalkanoates (phas), biopolyesters of hydroxyl fatty acids, are synthesized and deposited as cytoplasmic inclusions in many bacteria. we isolated a poly-beta-hydroxybutyrate (phb)-producing bacterium designated rhodobacter sphaeroides fj1. to characterize phb biosynthesis in this organism, we isolated the genes encoding proteins involved in phb metabolism. | 2006 | 16440119 |
| investigation of the effects of different carotenoids on the absorption and cd signals of light harvesting 1 complexes. | absorption and circular dichroism (cd) spectra of light-harvesting (lh)1 complexes from the purple bacteria rhodobacter (rba.) sphaeroides and rhodospirillum (rsp.) rubrum are presented. the complexes exhibit very low intensity, highly nonconservative, near-infrared (nir) cd spectra. absorption and cd spectra from several mutant and reconstituted lh1 complexes, with the carotenoid neurosporene and the precursor phytoene replacing the wild-type (wt) carotenoids, are also examined. the experiments ... | 2006 | 16494350 |
| the observation of ultrafast excited-state dynamical evolution in b800- partially or completely released lh2 of rhodobacter sphaeroides 601 at room temperature. | photodynamics of two kinds of peripheral antenna complexes (lh2 of rhodobacter sphaeroides, native lh2 (rs601) and b800-released lh2 where b800-bchls were partially or completely removed with different ph treatments), were studied using femtosecond pump-probe technique at different laser wavelengths. the obtained results for these samples with different b800/b850 ratios demonstrated that under the excitation around b800 nm, the photoabsorption and photobleaching dynamics were caused by the direc ... | 2006 | 16494502 |
| design of a minimal polypeptide unit for bacteriochlorophyll binding and self-assembly based on photosynthetic bacterial light-harvesting proteins. | we introduce lh1beta24, a minimal 24 amino acid polypeptide that binds and assembles bacteriochlorophylls (bchls) in micelles of octyl beta-glucoside (og) into complexes with spectral properties that resemble those of b820, a universal intermediate in the assembly of native purple bacterial light-harvesting complexes (lhs). lh1beta24 was designed by a survey of sequences and crystal structures of bacterial lh proteins from different organisms combined with currently available information from in ... | 2006 | 16475799 |
| community structures and activities of nitrifying and denitrifying bacteria in industrial wastewater-treating biofilms. | the bacterial community structure, in situ spatial distributions and activities of nitrifying and denitrifying bacteria in biofilms treating industrial wastewater were investigated by combination of the 16s rrna gene clone analysis, fluorescence in situ hybridization (fish) and microelectrodes. these results were compared with the nitrogen removal capacity of the industrial wastewater treatment plant (iwtp). both nitrification and denitrification occurred in the primary denitrification (pd) tank ... | 2006 | 16477661 |
| small weak acids reactivate proton transfer in reaction centers from rhodobacter sphaeroides mutated at aspl210 and aspm17. | in reaction centers of rhodobacter sphaeroides, site-directed mutagenesis has implicated several acidic residues in the delivery of protons to the secondary quinone (q(b)) during reduction to quinol. in a double mutant (asp(l210) --> asn + asp(m17) --> asn) that is severely impaired in proton transfer capability over a wide ph range, proton transfer was "rescued" by added weak acids. for low pk(a) acids the total concentration of salt required near neutral ph was high. the ionic strength effect ... | 2006 | 16354664 |
| the solution structure of the appa bluf domain: insight into the mechanism of light-induced signaling. | the transcriptional antirepressor appa from the photosynthetic bacterium rhodobacter sphaeroides senses both the light climate and the intracellular redox state. under aerobic conditions in the dark, appa binds to and thereby blocks the function of ppsr, a transcriptional repressor. absorption of a blue photon dissociates appa from ppsr and allows the latter to repress photosynthesis gene expression. the n terminus of appa contains sequence homology to flavin-containing photoreceptors that belon ... | 2006 | 16323221 |
| ecophysiology and molecular phylogeny of bacteria isolated from alkaline two-phase olive mill wastes. | the use of two-phase centrifugal decanters has been widely adopted in the olive oil extraction industry in order to reduce the huge quantities of wastewaters produced during the traditional three-phase extraction process. the resulting sludge-like byproduct, widely known as "alpeorujo", has a ph of 4-6, low water activity (a(w)) and high phytotoxicity. addition of ca(oh)(2) to alpeorujo, which is commonly performed at the olive oil mill to handle disposal problems related to acidic ph and odor e ... | 2006 | 16307869 |
| heavy metal ion influence on the photosynthetic growth of rhodobacter sphaeroides. | the potential of purple non-sulphur bacteria for bioremediation was assessed by investigating the ability of rhodobacter sphaeroides strain r26.1 to grow photosynthetically in heavy metal contaminated environments. bacterial cultures were carried out in artificially polluted media, enriched with the transition metal ions hg2+, cu2+, fe2+, ni2+, co2+, moo4(2-), and cro4(2-) in millimolar concentration range. for each investigated ion the effect on growth parameters was evaluated. the analysis of ... | 2006 | 16081134 |
| application of time-resolved polarization fluorescence spectroscopy in the femtosecond range to photosynthetic systems. | time-resolved polarization fluorescence spectroscopy in the femtosecond range was applied to a photosynthetic antenna system. specific signals of excited states were obtained by simultaneous measurements of fluorescence rise and decay curves and polarized spectroscopy. relaxation processes of carotenoids, energy transfer from carotenoids to chlorophyll (chl) a, and energy migration among pigment pools of chl a and chl b were clearly resolved. two new characteristics of carotenoid molecules were ... | 2007 | 16643087 |
| overexpression and characterization of the rhodobacter sphaeroides pufx membrane protein in escherichia coli. | heterologous expression of the pufx membrane protein from purple photosynthetic bacterium rhodobacter sphaeroides was attempted by using escherichia (e.) coli cells. the pufx was overexpressed as a recombinant protein with a histidine tag added to the carboxyl terminus, and can be extracted from the cell membrane by various detergents. circular dichroism measurements showed that the expressed pufx protein had alpha-helix contents of 29% in organic solvents and 22-26% in 0.8-2.0% (w/v) n-octyl be ... | 2007 | 16752956 |
| biotransformation of isoeugenol to vanillin by pseudomonas putida ie27 cells. | the ability to produce vanillin and/or vanillic acid from isoeugenol was screened using resting cells of various bacteria. the vanillin- and/or vanillic-acid-producing activities were observed in strains belonging to the genera achromobacter, aeromonas, agrobacerium, alcaligenes, arthrobacter, bacillus, micrococcus, pseudomonas, rhodobacter, and rhodococcus. strain ie27, a soil isolate showing the highest vanillin-producing activity, was identified as pseudomonas putida. we optimized the culture ... | 2007 | 16944125 |
| enthalpy/entropy driven activation of the first interquinone electron transfer in bacterial photosynthetic reaction centers embedded in vesicles of physiologically important phospholipids. | the thermodynamics and kinetics of light-induced electron transfer in bacterial photosynthetic rcs are sensitive to physiologically important lipids (phosphatidylcholine, cardiolipin and phosphatidylglycerol) in the environment. the analysis of the temperature-dependence of the rate of the p(+)q(a)(-)q(b)-->p(+)q(a)q(b)(-) interquinone electron transfer revealed high enthalpy change of activation in zwitterionic or neutral micelles and vesicles and low enthalpy change of activation in vesicles c ... | 2007 | 16713374 |
| global regulation of photosynthesis and respiration by fnrl: the first two targets in the tetrapyrrole pathway. | fnr is a regulator that controls the expression of a variety of genes in response to oxygen limitation in bacteria. to assess the role of fnr in photosynthesis in rubrivivax gelatinosus, a strain carrying a null mutation in fnrl was constructed. it was unable to grow anaerobically in the light, but, intriguingly, it was able to produce photosynthetic complexes under high oxygenation conditions. the mutant lacked all c-type cytochromes normally detectable in microaerobically-grown wild type cells ... | 2007 | 17178720 |
| importance of widespread gene transfer agent genes in alpha-proteobacteria. | the gene transfer agent produced by rhodobacter capsulatus (rcgta) is a model for several virus-like elements that seem to function solely for mediating gene exchange. several genes that encode rcgta are clearly related to bacteriophage genes but the cellular regulatory mechanisms that control rcgta production indicate that rcgta is more than just a defective prophage. genome sequencing projects show that seemingly functional rcgta-like structural gene clusters are present in many other species ... | 2007 | 17184993 |
| spectropotentiometric and structural analysis of the periplasmic nitrate reductase from escherichia coli. | the escherichia coli napa (periplasmic nitrate reductase) contains a [4fe-4s] cluster and a mo-bis-molybdopterin guanine dinucleotide cofactor. the napa holoenzyme associates with a di-heme c-type cytochrome redox partner (napb). these proteins have been purified and studied by spectropotentiometry, and the structure of napa has been determined. in contrast to the well characterized heterodimeric napab systems ofalpha-proteobacteria, such as rhodobacter sphaeroides and paracoccus pantotrophus, t ... | 2007 | 17130127 |
| toll-like receptor 4 signalling is neither sufficient nor required for oxidised phospholipid mediated induction of interleukin-8 expression. | toll-like receptor (tlr)-4 signalling has been shown to accelerate atherosclerosis. as oxidised phospholipids are present in atherosclerotic plaque and have been shown to modulate tlr4 signalling, we investigated the role of oxidised 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (oxpapc) in the regulation of tlr 1, 2, 4 and 6 signalling. | 2007 | 16982060 |
| the thiol:disulfide oxidoreductase dsbb mediates the oxidizing effects of the toxic metalloid tellurite (teo32-) on the plasma membrane redox system of the facultative phototroph rhodobacter capsulatus. | the highly toxic oxyanion tellurite (teo3(2-)) is a well known pro-oxidant in mammalian and bacterial cells. this work examines the effects of tellurite on the redox state of the electron transport chain of the facultative phototroph rhodobacter capsulatus, in relation to the role of the thiol:disulfide oxidoreductase dsbb. under steady-state respiration, the addition of tellurite (2.5 mm) to membrane fragments generated an extrareduction of the cytochrome pool (c- and b-type hemes); further, in ... | 2007 | 17098900 |
| the critical role of a hydrogen bond between gln63 and trp104 in the blue-light sensing bluf domain that controls appa activity. | appa is a novel blue-light receptor that controls photosynthetic gene expression in the purple bacterium rhodobacter sphaeroides. the photocycle reaction of the light-sensing domain, bluf, is unique in the sense that a few hydrogen bond rearrangements are accompanied by only slight structural changes of the bound chromophore. however, the exact features of the hydrogen bond network around the active site are still the subject of some controversy. here we present biochemical and genetic evidence ... | 2007 | 17399741 |
| in vitro assembly of a prohead-like structure of the rhodobacter capsulatus gene transfer agent. | the gene transfer agent (gta) is a phage-like particle capable of exchanging double-stranded dna fragments between cells of the photosynthetic bacterium rhodobacter capsulatus. here we show that the major capsid protein of gta, expressed in e. coli, can be assembled into prohead-like structures in the presence of calcium ions in vitro. transmission electron microscopy (tem) of uranyl acetate staining material and thin sections of glutaraldehyde-fixed material demonstrates that these associates h ... | 2007 | 17408713 |
| symmetry matters for the electronic structure of core complexes from rhodopseudomonas palustris and rhodobacter sphaeroides pufx-. | low-temperature (1.4 k), single-molecule fluorescence-excitation spectra have been recorded for individual reaction center-light-harvesting 1 complexes from rhodopseudomonas palustris and the pufx(-) strain of rhodobacter sphaeroides. more than 80% of the complexes from rb. sphaeroides show only broad absorption bands, whereas nearly all of the complexes from rps. palustris also have a narrow line at the low-energy end of their spectrum. we describe how the presence of this narrow feature indica ... | 2007 | 17416676 |
| kinetic variations determine the product pattern of phytoene desaturase from rubrivivax gelatinosus. | in bacteria and fungi, the degree of carotenoid desaturation is determined by a single enzyme, the crti-type phytoene desaturase. in different organisms, this enzyme can carry out either three, four or even five desaturation steps. the purple bacterium rubrivivax gelatinosus is the only known species in which reaction products of a 3-step and a 4-step desaturation (i.e. neurosporene and lycopene derivatives) accumulate simultaneously. the properties of this phytoene desaturation to catalyze neur ... | 2007 | 17428435 |
| energy and electron transfer in the photosynthetic reaction center complex of acidiphilium rubrum containing zn-bacteriochlorophyll a studied by femtosecond up-conversion spectroscopy. | a photosynthetic reaction center (rc) complex was isolated from a purple bacterium, acidiphilium rubrum. the rc contains bacteriochlorophyll a containing zn as a central metal (zn-bchl a) and bacteriopheophytin a (bphe a) but no mg-bchl a. the absorption peaks of the zn-bchl a dimer (p(zn)), the accessory zn-bchl a (b(zn)), and bphe a (h) at 4 k in the rc showed peaks at 875, 792, and 753 nm, respectively. these peaks were shorter than the corresponding peaks in rhodobacter sphaeroides rc that h ... | 2007 | 17169326 |
| [screening and identification of a photosynthetic bacterium reducing selenite to red elemental selenium]. | selenium is essential element for humans and animals but is very toxic at higher concentrations. in four inorganic states of selenate [seo4 2- ( vi)], selenite [seo3 2- (iv)], elemental selenium [se (0)] and selenide [se2- (- ii )], selenite is well known to be more soluble and higher toxic than other three forms. many microorganisms have the capacity to reduce selenite to red elemental selenium, which provide the potential to cope with the detoxification of pollution and to use the biological a ... | 2007 | 17436622 |
| ultrafast dynamics and excited state spectra of open-chain carotenoids at room and low temperatures. | many of the spectroscopic features and photophysical properties of carotenoids are explained using a three-state model in which the strong visible absorption of the molecules is associated with an s0 (1(1)ag-) --> s2 (1(1)bu+) transition, and the lowest lying singlet state, s1 (2(1)ag-), is a state into which absorption from the ground state is forbidden by symmetry. however, semiempirical and ab initio quantum calculations have suggested additional excited singlet states may lie either between ... | 2007 | 17441762 |
| genome analyses of three strains of rhodobacter sphaeroides: evidence of rapid evolution of chromosome ii. | three strains of rhodobacter sphaeroides of diverse origin have been under investigation in our laboratory for their genome complexities, including the presence of multiple chromosomes and the distribution of essential genes within their genomes. the genome of r. sphaeroides 2.4.1 has been completely sequenced and fully annotated, and now two additional strains (atcc 17019 and atcc 17025) of r. sphaeroides have been sequenced. thus, genome comparisons have become a useful approach in determining ... | 2007 | 17172323 |
| the inside ph determines rates of electron and proton transfer in vesicle-reconstituted cytochrome c oxidase. | cytochrome c oxidase is the terminal enzyme in the respiratory chains of mitochondria and many bacteria where it translocates protons across a membrane thereby maintaining an electrochemical proton gradient. results from earlier studies on detergent-solubilized cytochrome c oxidase have shown that individual reaction steps associated with proton pumping display ph-dependent kinetics. here, we investigated the effect of ph on the kinetics of these reaction steps with membrane-reconstituted cytoch ... | 2007 | 17466260 |
| biosorption and bioreduction of trivalent aurum by photosynthetic bacteria rhodobacter capsulatus. | biosorption has been shown to be an eco-friendly approach to remove heavy metal ions. in this study, the photosynthetic bacteria rhodobacter capsulatus was screened and found to have strong ability to adsorb au(iii). the maximum specific uptake of living cells was over 92.43 mg haucl(4)/g dry weight of cell in the logarithmic phase. biosorpion ability would be enhanced by an acidic environment. as the main cations, during biosorption the quantity of mg(2+) exchanged was more than na(+). biosorbe ... | 2007 | 17713815 |
| femtosecond spectroscopy of the primary charge separation in reaction centers of chloroflexus aurantiacus with selective excitation in the qy and soret bands. | the primary charge separation and electron-transfer processes of photosynthesis occur in the reaction center (rc). isolated rcs of the green filamentous anoxygenic phototrophic bacterium chloroflexus aurantiacus were studied at room temperature by using femtosecond transient absorption spectroscopy with selective excitation. upon excitation in the q(y) absorbance band of the bacteriochlorophyll (bchl) dimer (p) at 865 nm, a 7.0 +/- 0.5 ps kinetic component was observed in the 538 nm region (q(x) ... | 2007 | 17715904 |
| ph modulates the quinone position in the photosynthetic reaction center from rhodobacter sphaeroides in the neutral and charge separated states. | the structure of the photosynthetic reaction-center from rhodobacter sphaeroides has been determined at four different ph values (6.5, 8.0, 9.0, 10.0) in the neutral and in charge separated states. at ph 8.0, in the neutral state, we obtain a resolution of 1.87 a, which is the best ever reported for the bacterial reaction center protein. our crystallographic data confirm the existence of two different binding positions of the secondary quinone (qb). we observe a new orientation of qb in its dist ... | 2007 | 17570397 |
| in vitro assessment of gastrointestinal viability of two photosynthetic bacteria, rhodopseudomonas palustris and rhodobacter sphaeroides. | the objectives of this study were to assess the potential of two photosynthetic bacteria (psb), rhodopseudomonas palustris hz0301 and rhodobacter sphaeroides hz0302, as probiotics in aquaculture. the viability of hz0301 and hz0302 in simulated gastric transit conditions (ph 2.0, ph 3.0 and ph 4.0 gastric juices) and in simulated small intestinal transit conditions (ph 8.0, with or without 0.3% bile salts) was tested. the effects of hz0301 and hz0302 on the viability and permeability of intestina ... | 2007 | 17726751 |
| x-ray absorption studies of zn2+ binding sites in bacterial, avian, and bovine cytochrome bc1 complexes. | binding of zn2+ has been shown previously to inhibit the ubiquinol cytochrome c oxidoreductase (cyt bc1 complex). x-ray diffraction data in zn-treated crystals of the avian cyt bc1 complex identified two binding sites located close to the catalytic qo site of the enzyme. one of them (zn01) might interfere with the egress of protons from the qo site to the aqueous phase. using zn k-edge x-ray absorption fine-structure spectroscopy, we report here on the local structure of zn2+ bound stoichiometri ... | 2007 | 17573435 |
| on the effects of pufx on the absorption properties of the light-harvesting complexes of rhodobacter sphaeroides. | some species of purple bacteria as, e.g., rhodobacter sphaeroides contain the protein pufx. concurrently, the light harvesting complexes 1 (lh1) form dimers of open rings. in mutants without pufx, the lh1s are closed rings and photosynthesis breaks down, because the ubiquinone exchange at the reaction center is blocked. however, the main purpose of the lh1 is light harvesting. we therefore investigate the effects that the pufx-induced dimerization has on the absorption properties of the core com ... | 2007 | 17766331 |
| membrane sequestration of pii proteins and nitrogenase regulation in the photosynthetic bacterium rhodobacter capsulatus. | both rhodobacter capsulatus pii homologs glnb and glnk were found to be necessary for the proper regulation of nitrogenase activity and modification in response to an ammonium shock. as previously reported for several other bacteria, ammonium addition triggered the amtb-dependent association of glnk with the r. capsulatus membrane. native polyacrylamide gel electrophoresis analysis indicates that the modification/demodification of one pii homolog is aberrant in the absence of the other. in a gln ... | 2007 | 17586647 |
| stabilization of charge separation and cardiolipin confinement in antenna-reaction center complexes purified from rhodobacter sphaeroides. | the reaction center-light harvesting complex 1 (rc-lh1) purified from the photosynthetic bacterium rhodobacter sphaeroides has been studied with respect to the kinetics of charge recombination and to the phospholipid and ubiquinone (uq) complements tightly associated with it. in the antenna-rc complexes, at 6.5<ph<9.0, p(+)q(b)(-) recombines with a ph independent average rate constant <k> more than three times smaller than that measured in lh1-deprived rcs. at increasing ph values, for which <k> ... | 2007 | 17588528 |
| [synthesis of bacteriochlorophyll a by the purple nonsulfur bacterium rhodobacter capsulatus]. | the ability of purple nonsulfur bacteria rhodobacter capsulatus b10 to synthesize bacteriochlorophyll under phototrophic and dark conditions was studied. the modes for cultivation in the dark with oxygen limitation in a continuous culture at d = 0.1 h(-1) were selected. the yield of biomass reached 20 g/l; the bacteriochlorophyll a output of the process amounted to 16.6 mg/l h(-1). | 2007 | 17476808 |
| crystallographic location and mutational analysis of zn and cd inhibitory sites and role of lipidic carboxylates in rescuing proton path mutants in cytochrome c oxidase. | cytochrome c oxidase (cco) transfers protons from the inner surface of the enzyme to the buried o2 reduction site through two different pathways, termed k and d, and from the outer surface via an undefined route. these proton paths can be inhibited by metals such as zinc or cadmium, but the sites of inhibition have not been established. anomalous difference fourier analyses of rhodobacter sphaeroides cco crystals, with cadmium added, reveal metal binding sites that include the proposed initial p ... | 2007 | 17477548 |
| orientation-resolving pulsed electron dipolar high-field epr spectroscopy on disordered solids: i. structure of spin-correlated radical pairs in bacterial photosynthetic reaction centers. | distance and relative orientation of functional groups within protein domains and their changes during chemical reactions determine the efficiency of biological processes. in this work on disordered solid-state electron-transfer proteins, it is demonstrated that the combination of pulsed high-field epr spectroscopy at the w band (95 ghz, 3.4 t) with its extensions to peldor (pulsed electron-electron double resonance) and ridme (relaxation-induced dipolar modulation enhancement) offers a powerful ... | 2007 | 17497913 |
| the unusually strong hydrogen bond between the carbonyl of q(a) and his m219 in the rhodobacter sphaeroides reaction center is not essential for efficient electron transfer from q(a)(-) to q(b). | in native reaction centers (rcs) from photosynthetic purple bacteria the primary quinone (qa) and the secondary quinone (qb) are interconnected via a specific his-fe-his bridge. in rhodobacter sphaeroides rcs the c4=o carbonyl of qa forms a very strong hydrogen bond with the protonated npi of his m219, and the ntau of this residue is in turn coordinated to the non-heme iron atom. the second carbonyl of qa is engaged in a much weaker hydrogen bond with the backbone n-h of ala m260. in previous wo ... | 2007 | 17497939 |
| a haem cofactor is required for redox and light signalling by the appa protein of rhodobacter sphaeroides. | the appa protein of rhodobacter sphaeroides is unique in its ability to sense and transmit redox signals as well as light signals. by functioning as antagonist to the ppsr transcriptional repressor, it regulates the expression of photosynthesis genes in response to these environmental stimuli. here we show binding of the cofactor haem to a domain in the c-terminal part of appa and redox activity of bound haem. this is supported by the findings that: (i) the c-terminal domain of appa (appadeltan) ... | 2007 | 17501930 |
| light-dependent assimilation of trans-cinnamate by rhodobacter sphaeroides ou5. | we present a novel light-dependent metabolism of an aromatic compound (trans-cinnamate) that is assimilatory rather than dissimilatory. light-dependent assimilation of trans-cinnamate was observed by both growing and resting cells of rhodobacter sphaeroides ou5. trans-cinnamate assimilation could be correlated with simultaneous formation of both phenylalanine and tyrosine at near-stoichiometric ratios. trans-cinnamate assimilation was promoted by carbon source and electron donors, such as glucos ... | 2007 | 17503150 |
| postgenomic adventures with rhodobacter sphaeroides. | this review describes some of the recent highlights taken from the studies of rhodobacter sphaeroides 2.4.1. the review is not intended to be comprehensive, but to reflect the bias of the authors as to how the availability of a sequenced and annotated genome, a gene-chip, and proteomic profile as well as comparative genomic analyses can direct the progress of future research in this system. | 2007 | 17506668 |
| comparative genomics and site-directed mutagenesis support the existence of only one input channel for protons in the c-family (cbb3 oxidase) of heme-copper oxygen reductases. | oxygen reductase members of the heme-copper superfamily are terminal respiratory oxidases in mitochondria and many aerobic bacteria and archaea, coupling the reduction of molecular oxygen to water to the translocation of protons across the plasma membrane. the protons required for catalysis and pumping in the oxygen reductases are derived from the cytoplasmic side of the membrane, transferred via proton-conducting channels comprised of hydrogen bond chains containing internal water molecules alo ... | 2007 | 17676874 |
| plasmon waveguide resonance spectroscopic evidence for differential binding of oxidized and reduced rhodobacter capsulatus cytochrome c2 to the cytochrome bc1 complex mediated by the conformation of the rieske iron-sulfur protein. | the dissociation constants for the binding of rhodobacter capsulatus cytochrome c2 and its k93p mutant to the cytochrome bc1 complex embedded in a phospholipid bilayer were measured by plasmon waveguide resonance spectroscopy in the presence and absence of the inhibitor stigmatellin. the reduced form of cytochrome c2 strongly binds to reduced cytochrome bc1 (kd = 0.02 microm) but binds much more weakly to the oxidized form (kd = 3.1 microm). in contrast, oxidized cytochrome c2 binds to oxidized ... | 2007 | 17516628 |
| resolution of the spectroscopy versus crystallography issue for no intermediates of nitrite reductase from rhodobacter sphaeroides. | 2007 | 17685522 | |
| the structure of l-tyrosine 2,3-aminomutase from the c-1027 enediyne antitumor antibiotic biosynthetic pathway. | the sgcc4 l-tyrosine 2,3-aminomutase (sgtam) catalyzes the formation of (s)-beta-tyrosine in the biosynthetic pathway of the enediyne antitumor antibiotic c-1027. sgtam is homologous to the histidine ammonia lyase family of enzymes whose activity is dependent on the methylideneimidazole-5-one (mio) cofactor. unlike the lyase enzymes, sgtam catalyzes additional chemical transformations resulting in an overall stereospecific 1,2-amino shift in the substrate l-tyrosine to generate (s)-beta-tyrosine ... | 2007 | 17516659 |
| the phra gene of rhodobacter sphaeroides encodes a photolyase and is regulated by singlet oxygen and peroxide in a sigma(e)-dependent manner. | the genome of the facultatively photosynthetic bacterium rhodobacter sphaeroides encodes three proteins of the photolyase/cryptochrome family. this paper shows that phra (rsp2143) encodes a functional photolyase, which is an enzyme that repairs uv radiation-induced dna damage in a blue light dependent manner. expression of phra is upregulated in response to light, with no photoreceptor or the photosynthetic electron transport being involved. the results reveal that singlet oxygen and hydrogen pe ... | 2007 | 17526841 |
| phototrophic fe(ii) oxidation promotes organic carbon acquisition by rhodobacter capsulatus sb1003. | anoxygenic phototrophic fe(ii) oxidation is usually considered to be a lithoautotrophic metabolism that contributes to primary production in fe-based ecosystems. in this study, we employed rhodobacter capsulatus sb1003 as a model organism to test the hypothesis that phototrophic fe(ii) oxidation can be coupled to organic carbon acquisition. r. capsulatus sb1003 oxidized fe(ii) under anoxic conditions in a light-dependent manner, but it failed to grow lithoautotrophically on soluble fe(ii). when ... | 2007 | 17693559 |
| bacterial regulatory networks include direct contact of response regulator proteins: interaction of rega and ntrx in rhodobacter capsulatus. | the formation of photosynthetic complexes in facultatively photosynthetic bacteria is controlled by the oxygen tension in the environment. in rhodobacter capsulatus the two-component system regb/rega plays a major role in the redox control of photosynthesis genes but also controls other redox-dependent systems. the response regulator rega is phosphorylated under low oxygen tension and activates the puf and puc operons, which encode pigment binding proteins, by binding to their promoter regions. ... | 2007 | 17693720 |
| measuring electronic coupling in the reaction center of purple photosynthetic bacteria by two-color, three-pulse photon echo peak shift spectroscopy. | one- and two-color, three-pulse photon echo peak shift spectroscopy (1c and 2c3peps) was used to estimate the electronic coupling between the accessory bacteriochlorophyll (b) and the bacteriopheophytin (h) in the reaction center of the purple photosynthetic bacterium rhodobacter sphaeroides as approximately 170 +/- 30 cm-1. this is the first direct experimental determination of this parameter; it is within the range of values found in previously published calculations. the 1c3peps signal of the ... | 2007 | 17530796 |
| signals in solid-state photochemically induced dynamic nuclear polarization recover faster than signals obtained with the longitudinal relaxation time. | during the photocycle of quinone-blocked photosynthetic reaction centers (rcs), photochemically induced dynamic nuclear polarization (photo-cidnp) is produced by polarization transfer from the initially totally electron polarized electron pair and can be observed by 13c magic-angle spinning (mas) nmr as a strong modification of signal intensities. the same processes creating net nuclear polarization open up light-dependent channels for polarization loss. this leads to coherent and incoherent enh ... | 2007 | 17696523 |
| proteomic characterization of the rhodobacter sphaeroides 2.4.1 photosynthetic membrane: identification of new proteins. | the rhodobacter sphaeroides intracytoplasmic membrane (icm) is an inducible membrane that is dedicated to the major events of bacterial photosynthesis, including harvesting light energy, separating primary charges, and transporting electrons. in this study, multichromatographic methods coupled with fourier transform ion cyclotron resonance mass spectrometry, combined with subcellular fractionation, was used to test the hypothesis that the photosynthetic membrane of r. sphaeroides 2.4.1 contains ... | 2007 | 17704227 |
| a beta-galactosidase-based bacterial two-hybrid system to assess protein-protein interactions in the correct cellular environment. | the vast majority of proteins functions in complex with one or more of the same or other proteins, indicating that protein-protein interactions play crucial roles in biology. here, we present a beta-galactosidase reconstitution-based bacterial two-hybrid system in which two proteins of interest are fused to two non-functional but complementing beta-galactosidase truncations (delta alpha and delta omega). the level of complemented beta-galactosidase activity, driven by the protein-protein recogni ... | 2007 | 17539672 |
| comparative in vitro and in vivo studies on long-wavelength photosensitizers derived from bacteriopurpurinimide and bacteriochlorin p6: fused imide ring enhances the in vivo pdt efficacy. | in situ conversion of bacteriochlorophyll-a, present in rhodobacter sphaeroides (rb. sphaeroides) gave bacteriopurpurin-18 in modest yield, which in a sequence of reactions was converted into two series of bacteriochlorins: bacteriopurpurinimide and bacteriopurpurin p6 with and without a fused imide ring system, respectively. to determine the effect of overall lipophilicity in photosensitizing efficacy, these bacteriochlorins were independently reacted with hbr gas and subsequently treated with ... | 2007 | 17705415 |
| exposing the complex iii qo semiquinone radical. | complex iii qo site semiquinone has been assigned pivotal roles in productive energy-conversion and destructive superoxide generation. after a 30-year search, a genetic heme bh knockout arrests this transient semiquinone epr radical, revealing the natural engineering balance pitting energy-conserving, short-circuit minimizing, split electron transfer and catalytic speed against damaging oxygen reduction. | 2007 | 17560537 |
| endor spectroscopy reveals light induced movement of the h-bond from ser-l223 upon forming the semiquinone (q(b)(-)(*)) in reaction centers from rhodobacter sphaeroides. | proton endor spectroscopy was used to monitor local conformational changes in bacterial reaction centers (rc) associated with the electron-transfer reaction dqb --> d+*qb-* using mutant rcs capable of photoreducing qb at cryogenic temperatures. the charge separated state d+*qb-* was studied in mutant rcs formed by either (i) illuminating at low temperature (77 k) a sample frozen in the dark (ground state protein conformation) or (ii) illuminating at room temperature prior to and during freezing ... | 2007 | 17590017 |
| prrc, a sco homologue from rhodobacter sphaeroides, possesses thiol-disulfide oxidoreductase activity. | prrc is a sco homologue in rhodobacter sphaeroides that is associated with prrba, a two-component signal transduction system that induces photosynthesis gene expression in response to a decrease in oxygen tension. although sco proteins have been shown to bind copper the observation that they are structurally-related to thioredoxins suggested that they might possess thiol-disulfide oxidoreductase activity. our results show that prrc reduces cu(2+) to cu(+) and possesses disulfide reductase activi ... | 2007 | 17850796 |
| the flagellar muramidase from the photosynthetic bacterium rhodobacter sphaeroides. | we have characterized open reading frame rsp0072, which is located within the flgg operon in rhodobacter sphaeroides. the amino acid sequence analysis of this gene product showed the presence of a soluble lytic transglycosylase domain. the deletion of the n-terminal region (90 amino acids) of the product of rsp0072 yields a leaky nonmotile phenotype, as determined by swarm assays in soft agar. electron micrographs revealed the lack of flagella in mutant cells. the purified wild-type protein show ... | 2007 | 17873041 |
| flavin-dependent thymidylate synthase thyx activity: implications for the folate cycle in bacteria. | although flavin-dependent thyx proteins show thymidylate synthase activity in vitro and functionally complement thya defects in heterologous systems, direct proof of their cellular functions is missing. using insertional mutagenesis of rhodobacter capsulatus thyx, we constructed the first defined thyx inactivation mutant. phenotypic analyses of the obtained mutant strain confirmed that r. capsulatus thyx is required for de novo thymidylate synthesis. full complementation of the r. capsulatus thy ... | 2007 | 17890305 |
| chemotactic control of the two flagellar systems of rhodobacter sphaeroides is mediated by different sets of chey and flim proteins. | rhodobacter sphaeroides expresses two different flagellar systems, a subpolar flagellum (fla1) and multiple polar flagella (fla2). these structures are encoded by different sets of flagellar genes. the chemotactic control of the subpolar flagellum (fla1) is mediated by three of the six different chey proteins (chey6, chey4, or chey3). we show evidence that chey1, chey2, and chey5 control the chemotactic behavior mediated by fla2 flagella and that rsp6099 encodes the fla2 flim protein. | 2007 | 17890312 |
| identification, characterization and functional expression of a tyrosine ammonia-lyase and its mutants from the photosynthetic bacterium rhodobacter sphaeroides. | a tyrosine ammonia-lyase (tal) enzyme from the photosynthetic bacterium rhodobacter sphaeroides (rstal) was identified, cloned and functionally expressed in escherichia coli, where conversion of tyrosine to p-hydroxycinnamic acid (phca) was demonstrated. the rstal enzyme is implicated in production of phca, which serves as the cofactor for synthesis of the photoactive yellow protein (pyp) in photosynthetic bacteria. the wild type rstal enzyme, while accepting both tyrosine and phenylalanine as s ... | 2007 | 17602252 |
| in vivo and in vitro analysis of the rhodobacter sphaeroides chemotaxis signaling complexes. | this chapter describes both the in vivo and in vitro methods that have been successfully used to analyze the chemotaxis pathways of r. sphaeroides, showing that two operons each encode a complete chemosensory pathway with each forming into independent signaling clusters. the methods used range from in vitro analysis of the chemotaxis phosphorylation reactions to protein localization experiments. in vitro analysis using purified proteins shows a complex pattern of phosphotransfer. however, protei ... | 2007 | 17609142 |
| evaluation of colors in green mutants isolated from purple bacteria as a host for colorimetric whole-cell biosensors. | the change in carotenoid-based bacterial color from yellow to red can be applied to whole-cell biosensors. we generated several green mutants to emphasize the color change in such biosensors. the blue-green crti-deleted mutant, rhodopseudomonas palustris no.711, accumulated the colorless carotenoid precursor, phytoene. green rhodovulum sulfidophilum m31 accumulated neurosporene, a downstream product of phytoene. another green mutant, rhodobacter sphaeroides ga, accumulated neurosporene and chlor ... | 2007 | 17609942 |
| rega control of bacteriochlorophyll and carotenoid synthesis in rhodobacter capsulatus. | we provide in vivo genetic and in vitro biochemical evidence that rega directly regulates bacteriochlorophyll and carotenoid biosynthesis in rhodobacter capsulatus. beta-galactosidase expression assays with a rega-disrupted strain containing reporter plasmids for mg-protoporphyrin ix monomethyl ester oxidative cyclase (bche), mg-protoporphyrin ix chelatase (bchd), and phytoene dehydrogenase (crti) demonstrate rega is responsible for fourfold anaerobic induction of bche, threefold induction of bc ... | 2007 | 17616588 |
| the significance of type ii and prxq peroxiredoxins for antioxidative stress response in the purple bacterium rhodobacter sphaeroides. | two peroxiredoxins, classified as type ii and prxq, were characterized in the purple non-sulfur photosynthetic bacterium rhodobacter sphaeroides. both recombinant proteins showed remarkable thioredoxin-dependent peroxidase activity with broad substrate specificity in vitro. nevertheless, prxq of r. sphaeroides, unlike typical prxqs studied to date, does not contain one of the two conserved catalytic cys residues. we found that r. sphaeroides prxq and other prxq-like proteins from several organis ... | 2007 | 17644813 |
| flash-photolysis of fully reduced and mixed-valence co-bound rhodobacter sphaeroides cytochrome c oxidase: heme spectral shifts. | conformational changes, internal electron transfer, and co rebinding processes in cytochrome c oxidase from rhodobacter sphaeroides reduced to different degrees were investigated. the reactions were followed using a gated optical spectrometric multichannel analyzer. light-induced difference spectra, recorded in the 350-700 nm region over the 100 ns to 1 s time interval, were analyzed by singular value decomposition and global exponential fitting. the photolyzed fully reduced enzyme showed two re ... | 2007 | 17929941 |
| electron phototransfer between photosynthetic reaction centers of the bacteria rhodobacter sphaeroides and semiconductor mesoporous tio2 films. | 2007 | 17933338 | |
| redox potential of the non-heme iron complex in bacterial photosynthetic reaction center. | in bacterial photosynthetic reaction centers (brc), the electron is transferred from the special pair (p) via accessory bacteriochlorophyll (b(a)), bacteriopheopytin (h(a)), the primary quinone (q(a)) to the secondary quinone (q(b)). although the non-heme iron complex (fe complex) is located between q(a) and q(b), it was generally supposed not to be redox-active. involvement of the fe complex in electron transfer (et) was proposed in recent ftir studies [a. remy and k. gerwert, coupling of light ... | 2007 | 17936717 |
| identification of a rhodobacter capsulatus l-cysteine desulfurase that sulfurates the molybdenum cofactor when bound to xdhc and before its insertion into xanthine dehydrogenase. | the molybdenum cofactor (moco) containing enzymes aldehyde oxidase and xanthine dehydrogenase (xdh) require for activity a sulfuration step that inserts a terminal sulfur ligand into moco. xdhc was shown to be essential for the production of active xdh in rhodobacter capsulatus but is itself not a subunit of the purified enzyme. xdhc binds stoichiometric amounts of moco and is further able to transfer its bound moco to xdh. previous work suggested that xdhc particularly stabilizes the sulfurated ... | 2007 | 17649978 |
| a high-throughput strategy to screen 2d crystallization trials of membrane proteins. | electron microscopy of two-dimensional (2d) crystals has demonstrated potential for structure determination of membrane proteins. technical limitations in large-scale crystallization screens have, however, prevented a major breakthrough in the routine application of this technology. dialysis is generally used for detergent removal and reconstitution of the protein into a lipid bilayer, and devices for testing numerous conditions in parallel are not readily available. furthermore, the small size ... | 2007 | 17951070 |
| the equine tlr4/md-2 complex mediates recognition of lipopolysaccharide from rhodobacter sphaeroides as an agonist. | lipopolysaccharide (lps) antagonists inhibit the response of inflammatory cells to lps, presumably by competitive inhibition, and may be of therapeutic value in the treatment of endotoxemia and sepsis. the inhibitory effects of some lps antagonists are restricted to certain host species, however, as the same molecules can have significant endotoxic activity in other species. this species-specific recognition appears to be mediated by toll-like receptor 4 (tlr4) and/or md-2. we have shown previou ... | 2007 | 17956942 |
| ultrafast spectroscopy of biological photoreceptors. | we review recent new insights on reaction dynamics of photoreceptors proteins gained from ultrafast spectroscopy. in blue light sensing using fad (bluf) domains, a hydrogen-bond rearrangement around the flavin chromophore proceeds through a radical-pair mechanism, by which light-induced electron and proton transfer from the protein to flavin result in rotation of a conserved glutamine that switches the hydrogen bond network. femtosecond infrared spectroscopy has shown that in photoactive yellow ... | 2007 | 17959372 |
| heterogeneity of photosynthetic membranes from rhodobacter capsulatus: size dispersion and atp synthase distribution. | the density distribution of photosynthetic membrane vesicles (chromatophores) from rhodobacter capsulatus has been studied by isopicnic centrifugation. the average vesicle diameters, examined by electron microscopy, varied between 61 and 72 nm in different density fractions (70 nm in unfractionated chromatophores). the atp synthase catalytic activities showed maxima displaced toward the higher density fractions relative to bacteriochlorophyll, resulting in higher specific activities in those fra ... | 2007 | 17961501 |
| novel heme-based oxygen sensor with a revealing evolutionary history. | to monitor fluctuations in oxygen concentration, cells use sensory proteins often containing heme cofactors. here, we identify a new class of heme-binding oxygen sensors, reveal their unusual phylogenetic origin, and propose a sensing mode of a member of this class. we show that heme is bound noncovalently to the central region of appa, an oxygen and light sensor from rhodobacter sphaeroides. the addition of oxygen to ferrous appa discoordinated the heme, and subsequent oxygen removal fully rest ... | 2007 | 17660296 |
| time-resolved ft-ir spectroscopy traces signal relay within the blue-light receptor appa. | 2007 | 17623285 | |
| rhodethrin: a novel indole terpenoid ether produced by rhodobacter sphaeroides has cytotoxic and phytohormonal activities. | a novel metabolite was isolated from the culture supernatants of rhodobacter sphaeroides ou5 when grown on l-tryptophan as sole source of nitrogen under photoheterotrophic conditions. it was identified by ir, nmr ((1)h, (13)c) and ms as an indole terpenoid ether [3-hydroxy-6-(1h-indol-3-yloxy)-4-methylhexanoic acid] and is named as rhodethrin. rhodethrin at 0.5 microm gave positive test in auxin bioassay and initiated early rooting in tissue-cultured plants than iaa at 5 microm. rhodethrin has c ... | 2007 | 17636389 |
| role of tyrosine-34 in the anion binding equilibria in manganese(ii) superoxide dismutases. | superoxide dismutases (sods) are proteins specialized in the depletion of superoxide from the cell through disproportionation of this anion into oxygen and hydrogen peroxide. we have used high-field electron paramagnetic resonance (hfepr) to test a two-site binding model for the interaction of manganese-sods with small anions. because tyrosine-34 was thought to act as a gate between these two sites in this model, a tyrosine to phenylalanine mutant of the superoxide dismutase from r. capsulatus w ... | 2007 | 17636871 |
| rhodobacter capsulatus magnesium chelatase subunit bchh contains an oxygen sensitive iron-sulfur cluster. | magnesium chelatase is the first unique enzyme of the bacteriochlorophyll biosynthetic pathway. it consists of three subunits (bchi, bchd, and bchh). amino acid sequence analysis of the rhodobacter capsulatus bchh revealed a novel cysteine motif (393cx2cx3cx14c) that was found in only six other proteobacteria (cx2cx3cx11-14c). the cysteine motif is likely to coordinate an unprecedented [fe-s] cluster. purified bchh demonstrated absorbance in the 460 nm region. this absorbance was abolished in bc ... | 2007 | 17639347 |
| crystal structure of the chromophore binding domain of an unusual bacteriophytochrome, rpbphp3, reveals residues that modulate photoconversion. | bacteriophytochromes rpbphp2 and rpbphp3 from the photosynthetic bacterium rhodopseudomonas palustris work in tandem to modulate synthesis of the light-harvesting complex lh4 in response to light. although rpbphp2 and rpbphp3 share the same domain structure with 52% sequence identity, they demonstrate distinct photoconversion behaviors. rpbphp2 exhibits the "classical" phytochrome behavior of reversible photoconversion between red (pr) and far-red (pfr) light-absorbing states, whereas rpbphp3 ex ... | 2007 | 17640891 |
| transfer of the molybdenum cofactor synthesized by rhodobacter capsulatus moea to xdhc and moba. | the molybdenum cofactor (moco) exists in different variants in the cell and can be directly inserted into molybdoenzymes utilizing the molybdopterin (mpt) form of moco. in bacteria such as rhodobacter capsulatus and escherichia coli, mpt is further modified by attachment of a gmp nucleotide, forming mpt guanine dinucleotide (mgd). in this work, we analyzed the distribution and targeting of different forms of moco to their respective user enzymes by proteins that bind moco and are involved in its ... | 2007 | 17686778 |
| a new ruthenium complex to study single-electron reduction of the pulsed o(h) state of detergent-solubilized cytochrome oxidase. | the first step in the catalytic cycle of cytochrome oxidase, the one-electron reduction of the fully oxidized enzyme, was investigated using a new photoactive binuclear ruthenium complex, [ru(bipyrazine)2]2(quaterpyridine), (ru2z). the aim of the work was to examine differences in the redox kinetics resulting from pulsing the oxidase (i.e., fully reducing the enzyme followed by reoxidation) just prior to photoreduction. recent reports indicate transient changes in the redox behavior of the metal ... | 2007 | 18027981 |
| probing the role of copper in the biosynthesis of the molybdenum cofactor in escherichia coli and rhodobacter sphaeroides. | the crystal structure of cnx1g, an enzyme involved in the biosynthesis of the molybdenum cofactor (moco) in arabidopsis thaliana, revealed the remarkable feature of a copper ion bound to the dithiolene unit of a molybdopterin intermediate (kuper et al. nature 430:803-806, 2004). to characterize further the role of copper in moco biosynthesis, we examined the in vivo and/or in vitro activity of two moco-dependent enzymes, dimethyl sulfoxide reductase (dmsor) and nitrate reductase (nr), from cells ... | 2007 | 17687573 |
| efficient simulation of three-pulse photon-echo signals with application to the determination of electronic coupling in a bacterial photosynthetic reaction center. | a time-nonlocal quantum master equation coupled with a perturbative scheme to evaluate the third-order polarization in the phase-matching direction k(s) = -k(1) + k(2) + k(3) is used to efficiently simulate three-pulse photon-echo signals. the present method is capable of describing photon-echo peak shifts including pulse overlap and bath memory effects. in addition, the method treats the non-markovian evolution of the density matrix and the third-order polarization in a consistent manner, thus ... | 2007 | 17696328 |
| substitution of isoleucine l177 by histidine in rhodobacter sphaeroides reaction center results in the covalent binding of pa bacteriochlorophyll to the l subunit. | in this work, we report the unique case of bacteriochlorophyll (bchl) - protein covalent attachment in a photosynthetic membrane complex caused by a single mutation. the isoleucine l177 was substituted by histidine in the photosynthetic reaction center (rc) of rhodobacter sphaeroides. pigment analysis revealed that one bchl molecule was missing in the acetone-methanol extract of the i(l177)h rcs. sds-page demonstrated that this bchl molecule could not be extracted with organic solvents apparentl ... | 2007 | 18036346 |
| effect of dietary rhodobacter capsulatus on cholesterol concentration and fatty acid composition in broiler meat. | the study was designed to investigate the effects of dietary rhodobacter capsulatus on cholesterol concentration and fatty acid composition in broiler meat. a total of 45 two-week-old male broiler chicks were randomly assigned into 3 treatment groups and fed ad libitum diets supplemented with 0 (control), 0.02, and 0.04% r. capsulatus for a 6-wk feeding period. the results of this study revealed that the supplementation of 0.04% r. capsulatus in diet reduced (p < 0.05) cholesterol and triglyceri ... | 2007 | 17704380 |
| phosphatidylcholine is required for the efficient formation of photosynthetic membrane and b800-850 light-harvesting complex in rhodobacter sphaeroides. | no phosphatidylcholine (pc) was detected in the membrane of rhodobacter sphaeroides pmta mutant (pmta1) lacking phosphatidylethanolamine (pe) n-methyltransferase, whereas pe in the mutant was increased up to the mole % comparable to the combined level of pe and pc of wild type. neither the fatty acid composition nor the fluidity of membrane was altered by pmta mutation. consistently, aerobic and photoheterotrophic growth of pmta1 were not different from wild type. however, pmta1 showed an extend ... | 2007 | 18051772 |
| structural responses to cavity-creating mutations in an integral membrane protein. | x-ray crystallography has been used to investigate the extent of structural changes in mutants of the purple bacterial reaction center that assemble without a particular ubiquinone or bacteriopheophytin cofactor. in the case of the bacteriopheophytin-exclusion mutant, in which ala m149 was replaced by trp (am149w), the quality of protein crystals was improved over that seen in previous work by minimizing illumination, time, and temperature during the purification protocol and carrying out crysta ... | 2007 | 17711306 |
| probing the flexibility of the bacterial reaction center: the wild-type protein is more rigid than two site-specific mutants. | experimental and theoretical studies have stressed the importance of flexibility for protein function. however, more local studies of protein dynamics, using temperature factors from crystallographic data or elastic models of protein mechanics, suggest that active sites are among the most rigid parts of proteins. we have used quasielastic neutron scattering to study the native reaction center protein from the purple bacterium rhodobacter sphaeroides, over a temperature range of 4-260 k, in paral ... | 2007 | 18052234 |
| structure of the charge separated state p865(+)q(a)- in the photosynthetic reaction centers of rhodobacter sphaeroides by quantum beat oscillations and high-field electron paramagnetic resonance: evidence for light-induced q(a)- reorientation. | the structure of the secondary radical pair, p865(+)q(a)-, in fully deuterated and zn-substituted reaction centers (rcs) of the purple bacterium rhodobacter sphaeroides r-26 has been determined by high-time resolution and high-field electron paramagnetic resonance (epr). a computer analysis of quantum beat oscillations, observed in a two-dimensional q-band (34 ghz) epr experiment, provides the orientation of the various magnetic tensors of p865(+)q(a)- with respect to a magnetic reference frame. ... | 2007 | 18052250 |
| isolation of sip, a protein that interacts with spb, a possible transcriptional regulatory factor in rhodobacter sphaeroides. | spb is a transcriptional factor in rhodobacter sphaeroides that represses expression of the puf operon under aerobic or semi-aerobic light conditions. here, we identified a 17,500 da protein designated sip (spb interaction protein) that interacts with spb, as determined by binding to an spb-his(x6) fusion protein-ni column. the spb-sip interaction in vivo was confirmed by an immunoprecipitation assay. the level of transcripts and protein of sip did not differ for all growth conditions tested, in ... | 2007 | 17720716 |
| optimization of polyhydroxybutyrate production from a wild type and two mutant strains of rhodobacter sphaeroides using statistical method. | interaction studies using central composite design (ccd) gave the optimum concentrations of acetate at 4 g l(-1) and (nh4)2so4 at 0.01 g l(-1) with an optimum temperature of 35 degrees c. rhodobacter sphaeroides n20 gave the highest phb (7.8 g l(-1)) and biomass (dcw) (8.2 g l(-1)) values compared to the wild type strain and the mutant strain u7. the ccd results predicted that the optimum medium for the mutant strain n20 consisted of 3.90 g l(-1) acetate, 0.01 g l(-1) (nh4)2so4 at 33.5 degrees c ... | 2007 | 17765994 |
| atomic resolution structures of rieske iron-sulfur protein: role of hydrogen bonds in tuning the redox potential of iron-sulfur clusters. | the rieske [2fe-2s] iron-sulfur protein of cytochrome bc(1) functions as the initial electron acceptor in the rate-limiting step of the catalytic reaction. prior studies have established roles for a number of conserved residues that hydrogen bond to ligands of the [2fe-2s] cluster. we have constructed site-specific variants at two of these residues, measured their thermodynamic and functional properties, and determined atomic resolution x-ray crystal structures for the native protein at 1.2 a re ... | 2007 | 17223530 |
| following photoinduced dynamics in bacteriorhodopsin with 7-fs impulsive vibrational spectroscopy. | sub-10-fs laser pulses are used to impulsively photoexcite bacteriorhodopsin (br) suspensions and probe the evolution of the resulting vibrational wave packets. fourier analysis of the spectral modulations induced by transform-limited as well as linearly chirped excitation pulses allows the delineation of excited- and ground-state contributions to the data. on the basis of amplitude and phase variations of the modulations as a function of the dispersed probe wavelength, periodic modulations in a ... | 2007 | 17227016 |
| cytochrome c(2) exit strategy: dissociation studies and evolutionary implications. | small, water-soluble, type c cytochromes form a transient network connecting major bioenergetic membrane protein complexes in both photosynthesis and respiration. in the photosynthesis cycle of rhodobacter sphaeroides, cytochrome c2 (cyt c2) docks to the reaction center (rc), undergoes electron transfer, and exits for the cytochrome bc1 complex. translations of cyt c2 about the rc-cyt c2 docking interface and surrounding membrane reveal possible exit pathways. a pathway at a minimal elevation al ... | 2007 | 17228920 |