| 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 |
| catabolism of l-phenylalanine and l-tyrosine by rhodobacter sphaeroides ou5 occurs through 3,4-dihydroxyphenylalanine. | rhodobacter sphaeroides ou5 utilized l-phenylalanine as sole source of nitrogen for growth. the metabolites of l-phenylalanine catabolism, i.e. 4-hydroxy phenylalanine (l-tyrosine), 3,4-dihydroxyphenylalanine (dopa), 3,4-dihydroxyphenyl-pyruvic acid (dopp), 3,4-dihydroxyphenyllactic acid (dopla), 3,4-dihydroxyphenyl-acetic acid (dopac) and 3,4-dihydroxybenzoic acid (pc), were identified using liquid chromatography-mass spectroscopy (lc-ms). with 2-oxoglutarate as an amino acceptor, dopa aminotra ... | 2007 | 17616348 |
| hydrogen bonds between nitrogen donors and the semiquinone in the qi-site of the bc1 complex. | the ubisemiquinone stabilized at the qi-site of the bc1 complex of rhodobacter sphaeroides forms a hydrogen bond with a nitrogen from the local protein environment, tentatively identified as ring n from his-217. the interactions of 14n and 15n have been studied by x-band (approximately 9.7 ghz) and s-band (3.4 ghz) pulsed epr spectroscopy. the application of s-band spectroscopy has allowed us to determine the complete nuclear quadrupole tensor of the 14n involved in h-bond formation and to assig ... | 2007 | 17616531 |
| 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 |
| two stereoisomers of spheroidene in the rhodobacter sphaeroides r26 reaction center: a dft analysis of resonance raman spectra. | from a theoretical analysis of the resonance raman spectra of 19 isotopomers of spheroidene reconstituted into the reaction center (rc) of rhodobacter sphaeroides r26, we conclude that the carotenoid in the rc occurs in two configurations. the normal mode underlying the resonance raman transition at 1239 cm(-1), characteristic for spheroidene in the rc, has been identified and found to uniquely refer to the cis nature of the 15,15' carbon-carbon double bond. detailed analysis of the isotope-indu ... | 2007 | 17617552 |
| time-resolved ft-ir spectroscopy traces signal relay within the blue-light receptor appa. | | 2007 | 17623285 |
| purification and assays of rhodobacter capsulatus regb-rega two-component signal transduction system. | two-component signal-transduction systems, composed of a histidine-sensor kinase and a dna-binding response regulator, allow bacteria to detect environmental changes and adjust cellular physiology to live more efficiently in a broad distribution of niches. although many two-component signal-transduction systems are known, a limited number of signals that stimulate these systems have been discovered. this chapter describes the purification and characterization of the predominant two-component sig ... | 2007 | 17628139 |
| 13c chemical shift map of the active cofactors in photosynthetic reaction centers of rhodobacter sphaeroides revealed by photo-cidnp mas nmr. | 13c photo-cidnp mas nmr studies have been performed on reaction centers (rcs) of rhodobacter sphaeroides wild type (wt) that have been selectively labeled with an isotope using [5-13c]-delta-aminolevulinic acid.hcl in all the bchl and bphe cofactors at positions c-4, c-5, c-9, c-10, c-14, c-15, c-16, and c-20. 13c cp/mas nmr and 13c-13c dipolar correlation photo-cidnp mas nmr provide a chemical shift map of the cofactors involved in the electron transfer process in the rc at the atomic scale. th ... | 2007 | 17630781 |
| 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 |
| 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 |
| 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 |
| 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 |
| access to the active site of periplasmic nitrate reductase: insights from site-directed mutagenesis and zinc inhibition studies. | the periplasmic nitrate reductase (napab), a member of the dmso reductase superfamily, catalyzes the first step of the denitrification process in bacteria. in this heterodimer, a di-heme napb subunit is associated to the catalytic napa subunit that binds a [4fe-4s] cluster and a bis(molybdopterin guanine dinucleotide) cofactor. here, we report the kinetic characterization of purified mutated heterodimers from rhodobacter sphaeroides. by combining site-directed mutagenesis, redox potentiometry, e ... | 2007 | 17676770 |
| 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 |
| effects of slow substrate binding and release in redox enzymes: theory and application to periplasmic nitrate reductase. | for redox enzymes, the technique called protein film voltammetry makes it possible to determine the entire profile of activity against driving force by having the enzyme exchanging directly electrons with the rotating-disc electrode onto which it is adsorbed. both the potential location of the catalytic response and its detailed shape report on the sequence of catalytic events, electron transfers and chemical steps, but the models that have been used so far to decipher this signal lack generalit ... | 2007 | 17676894 |
| resolution of the spectroscopy versus crystallography issue for no intermediates of nitrite reductase from rhodobacter sphaeroides. | | 2007 | 17685522 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| the highly toxic oxyanion tellurite (teo (3) (2-) ) enters the phototrophic bacterium rhodobacter capsulatus via an as yet uncharacterized monocarboxylate transport system. | the facultative phototroph rhodobacter capsulatus takes up the highly toxic oxyanion tellurite when grown under both photosynthetic and respiratory growth conditions. previous works on escherichia coli and r. capsulatus suggested that tellurite uptake occurred through a phosphate transporter. here we present evidences indicating that tellurite enters r. capsulatus cells via a monocarboxylate transport system. indeed, intracellular accumulation of tellurite was inhibited by the addition of monoca ... | 2008 | 17713758 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| rhodobacter vinaykumarii sp. nov., a marine phototrophic alphaproteobacterium from tidal waters, and emended description of the genus rhodobacter. | a rod-shaped, phototrophic, purple non-sulfur bacterium was isolated in pure culture from seawater collected from the seashore of visakhapatnam, on the east coast of india, in a medium that contained 2 % nacl (w/v). strain ja123(t) was gram-negative and non-motile and had a requirement for nacl. photo-organoheterotrophic and chemo-organoheterotrophic growth occurred with organic compounds as carbon sources and electron donors. photolithoautotrophic, chemolithoautotrophic and fermentative growth ... | 2007 | 17766859 |
| a conserved structural module regulates transcriptional responses to diverse stress signals in bacteria. | a transcriptional response to singlet oxygen in rhodobacter sphaeroides is controlled by the group iv sigma factor sigma(e) and its cognate anti-sigma chrr. crystal structures of the sigma(e)/chrr complex reveal a modular, two-domain architecture for chrr. the chrr n-terminal anti-sigma domain (asd) binds a zn(2+) ion, contacts sigma(e), and is sufficient to inhibit sigma(e)-dependent transcription. the chrr c-terminal domain adopts a cupin fold, can coordinate an additional zn(2+), and is requi ... | 2007 | 17803943 |
| protein shape and crowding drive domain formation and curvature in biological membranes. | folding, curvature, and domain formation are characteristics of many biological membranes. yet the mechanisms that drive both curvature and the formation of specialized domains enriched in particular protein complexes are unknown. for this reason, studies in membranes whose shape and organization are known under physiological conditions are of great value. we therefore conducted atomic force microscopy and polarized spectroscopy experiments on membranes of the photosynthetic bacterium rhodobacte ... | 2008 | 17827217 |
| azoreductase from rhodobacter sphaeroides as1.1737 is a flavodoxin that also functions as nitroreductase and flavin mononucleotide reductase. | previously reported azoreductase (azr) from rhodobacter sphaeroides as1.1737 was shown to be a flavodoxin possessing nitroreductase and flavin mononucleotide (fmn) reductase activities. the structure model of azr constructed with swiss-model displayed a flavodoxin-like fold with a three-layer alpha/beta/alpha structure. with nitrofurazone as substrate, the optimal ph value and temperature were 7.0 and 50 degrees c, respectively. azr could reduce a number of nitroaromatic compounds including 2,4- ... | 2007 | 17846764 |
| 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 |
| atomic-level structural and functional model of a bacterial photosynthetic membrane vesicle. | the photosynthetic unit (psu) of purple photosynthetic bacteria consists of a network of bacteriochlorophyll-protein complexes that absorb solar energy for eventual conversion to atp. because of its remarkable simplicity, the psu can serve as a prototype for studies of cellular organelles. in the purple bacterium rhodobacter sphaeroides the psu forms spherical invaginations of the inner membrane, approximately 70 nm in diameter, composed mostly of light-harvesting complexes, lh1 and lh2, and rea ... | 2007 | 17895378 |
| met23lys mutation in subunit gamma of f(o)f(1)-atp synthase from rhodobacter capsulatus impairs the activation of atp hydrolysis by protonmotive force. | h(+)-f(o)f(1)-atp synthase couples proton flow through its membrane portion, f(o), to the synthesis of atp in its headpiece, f(1). upon reversal of the reaction the enzyme functions as a proton pumping atpase. even in the simplest bacterial enzyme the atpase activity is regulated by several mechanisms, involving inhibition by mgadp, conformational transitions of the epsilon subunit, and activation by protonmotive force. here we report that the met23lys mutation in the gamma subunit of the rhodob ... | 2007 | 17904517 |
| the photosystem of rhodobacter sphaeroides assembles with zinc bacteriochlorophyll in a bchd (magnesium chelatase) mutant. | a rhodobacter sphaeroides bchd (magnesium chelatase) mutant was studied to determine the properties of its photosystem in the absence of bacteriochlorophyll (bchl). western blots of reaction center h, m, and l (rc h/m/l) proteins from mutant membranes showed levels of 12% rc h, 32% rc l, and 46% rc m relative to those of the wild type. tricine-sds-page revealed 52% light-harvesting complex alpha chain and 14% beta chain proteins compared to those of the wild type. pigment analysis of bchd cells ... | 2007 | 17910480 |
| biophysical and biochemical characterization of reconstituted and purified rhodobacter sphaeroides cytochrome c oxidase in phospholipid vesicles sheds insight into its functional oligomeric structure. | discontinuous sucrose gradient ultracentrifugation was used to separate liposomes containing rhodobacter sphaeroides cytochrome c oxidase (pcov) from liposomes devoid of the enzyme, and the biophysical and biochemical properties of pcov were compared to unpurified liposomes containing cytochrome c oxidase (cov). isolated and purified r. sphaeroides cytochrome c oxidase (cox) was reconstituted into asolectin phospholipid vesicles by cholate dialysis, and this preparation was purified further on a ... | 2007 | 17910921 |
| comparison of the fluorescence kinetics of detergent-solubilized and membrane-reconstituted lh2 complexes from rps. acidophila and rb. sphaeroides. | picosecond time-resolved fluorescence spectroscopy has been used in order to compare the fluorescence kinetics of detergent-solubilized and membrane-reconstituted light-harvesting 2 (lh2) complexes from the purple bacteria rhodopseudomonas (rps.) acidophila and rhodobacter (rb.) sphaeroides. lh2 complexes were reconstituted in phospholipid model membranes at different lipid:protein-ratios and all samples were studied exciting with a wide range of excitation densities. while the detergent-solubil ... | 2008 | 17912609 |
| crystal structure of an unusual thioredoxin protein with a zinc finger domain. | many gram-negative bacteria have two cytoplasmic thioredoxins, thioredoxin-1 and -2, encoded by the trxa and trxc genes, respectively. both thioredoxins have the highly conserved wcgpc motif and function as disulfide-bond reductases. however, thioredoxin-2 has unique features: it has an n-terminal motif that binds a zinc ion, and its transcription is under the control of oxyr, which allows it to be up-regulated under oxidative stress. here, we report the crystal structure of thioredoxin-2 from r ... | 2007 | 17913712 |
| spectroscopic and kinetic studies of y114f and w116f mutants of me2so reductase from rhodobacter capsulatus. | mutants of the active site residues trp-116 and tyr-114 of the molybdenum-containing me(2)so reductase from rhodobacter capsulatus have been examined spectroscopically and kinetically. the y114f mutant has an increased rate constant for oxygen atom transfer from me(2)so to reduced enzyme, the result of lower stability of the e(red).me(2)so complex. the absorption spectrum of this species (but not that of either oxidized or reduced enzyme) is significantly perturbed in the mutant relative to wild ... | 2007 | 17921142 |
| rhodobacter capsulatus olsa is a bifunctional enzyme active in both ornithine lipid and phosphatidic acid biosynthesis. | the rhodobacter capsulatus genome contains three genes (olsa [plsc138], plsc316, and plsc3498) that are annotated as lysophosphatidic acid (1-acyl-sn-glycerol-3-phosphate) acyltransferase (agpat). of these genes, olsa was previously shown to be an o-acyltransferase in the second step of ornithine lipid biosynthesis, which is important for optimal steady-state levels of c-type cytochromes (s. aygun-sunar, s. mandaci, h.-g. koch, i. v. j. murray, h. goldfine, and f. daldal. mol. microbiol. 61:418- ... | 2007 | 17921310 |
| the pucc protein of rhodobacter capsulatus mitigates an inhibitory effect of light-harvesting 2 alpha and beta proteins on light-harvesting complex 1. | rhodobacter capsulatus contains lhaa and pucc genes that have been implicated in light-harvesting complex 1 and 2 (lh1 and lh2) assembly. the proteins encoded by these genes, and homologues in other photosynthetic organisms, have been classified as the bacteriochlorophyll delivery (bcd) family of the major facilitator superfamily. a new bcd family phylogenetic tree reveals that several pucc, lhaa and orf428-related sequences each form separate clusters, while plant and cyanobacterial homologues ... | 2008 | 17922301 |
| atomic force microscopy reveals multiple patterns of antenna organization in purple bacteria: implications for energy transduction mechanisms and membrane modeling. | recent topographs of the intracytoplasmic membrane (icm) of purple bacteria obtained by atomic force microscopy (afm) have provided the first surface views of the native architecture of a multicomponent biological membrane at submolecular resolution, representing an important landmark in structural biology. a variety of species-dependent, closely packed arrangements of light-harvesting (lh) complexes was revealed: the most highly organized was found in rhodobacter sphaeroides in which the periph ... | 2008 | 17922302 |
| linear and nonlinear optical responses in bacteriochlorophyll a. | nonlinear optical responses of bacteriochlorophyll a (bchl a) were investigated by means of the three-pulse four-wave mixing (fwm) technique under the resonant excitation into the q ( y ) band. the experimental results are explained by a theoretical model calculation including the brownian oscillation mode of the solvent. we have determined the spectral density, which is the most important function with which to calculate optical signals. the linear absorption spectrum can be reproduced fairly w ... | 2008 | 17926140 |
| development of a solar-powered microbial fuel cell. | to understand factors that impact solar-powered electricity generation by rhodobacter sphaeroides in a single-chamber microbial fuel cell (mfc). | 2008 | 17927750 |
| site-directed mutagenesis of five conserved residues of subunit i of the cytochrome cbb3 oxidase in rhodobacter capsulatus. | cytochrome cbb(3) oxidase is a member of the heme-copper oxidase superfamily that catalyses the reduction of molecular oxygen to the water and conserves the liberated energy in the form of a proton gradient. comparison of the amino acid sequences of subunit i from different classes of heme-copper oxidases showed that transmembrane helix viii and the loop between transmembrane helices ix and x contain five highly conserved polar residues; ser333, ser340, thr350, asn390 and thr394. to determine th ... | 2007 | 17927903 |
| 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 |
| a new method for isolating physiologically active mg-protoporphyrin monomethyl ester, the substrate of the cyclase enzyme of the chlorophyll biosynthetic pathway. | mg-protoporphyrin monomethyl ester (mpe) is a biosynthetic intermediate of chlorophyll and converted by mpe cyclase to protochlorophyllide. limited availability of mpe has so far hampered cyclase research. in a new, simplified, method mpe was prepared from freeze dried bche mutant rhodobacter capsulatus db575 cells by extraction with acetone/h(2)o/25% nh(3). isolated mpe was identified by absorption and fluorescence spectroscopy, and its purity was analyzed by hplc. the extracted mpe was dried a ... | 2007 | 17949988 |
| 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 |
| transcriptome dynamics during the transition from anaerobic photosynthesis to aerobic respiration in rhodobacter sphaeroides 2.4.1. | rhodobacter sphaeroides 2.4.1 is a facultative photosynthetic anaerobe that grows by anoxygenic photosynthesis under anaerobic-light conditions. changes in energy generation pathways under photosynthetic and aerobic respiratory conditions are primarily controlled by oxygen tensions. in this study, we performed time series microarray analyses to investigate transcriptome dynamics during the transition from anaerobic photosynthesis to aerobic respiration. major changes in gene expression profiles ... | 2008 | 17965166 |
| photo-cidnp mas nmr beyond the t1 limit by fast cycles of polarization extinction and polarization generation. | in nanosecond-laser flash photo-cidnp mas nmr, polarization generation (pg) proceeds much faster than longitudinal spin relaxation. with a nanosecond-laser setup linked to the nmr console the repetition time of the experiment is then limited by the minimum recycle delay of the nmr spectrometer and the maximum repetition rate of laser flashes. these limits can only be reached if polarization left after the nmr experiment is completely canceled before the next laser flash. we introduce a presatura ... | 2008 | 17967555 |
| biomass-supported palladium catalysts on desulfovibrio desulfuricans and rhodobacter sphaeroides. | a rhodobacter sphaeroides-supported dried, ground palladium catalyst ("rs-pd(0)") was compared with a desulfovibrio desulfuricans-supported catalyst ("dd-pd(0)") and with unsupported palladium metal particles made by reduction under h2 ("chem-pd(0)"). cell surface-located clusters of pd(0) nanoparticles were detected on both d. desulfuricans and r. sphaeroides but the size and location of deposits differed among comparably loaded preparations. these differences may underlie the observation of di ... | 2008 | 17969153 |
| redox interaction of mn-bicarbonate complexes with reaction centres of purple bacteria. | it is found that dark reduction of photooxidized primary electron donor p870+ in reaction centres from purple anoxygenic bacteria (two non-sulphur fe-oxidizing rhodovulum iodosum and rhodovulum robiginosum, rhodobacter sphaeroides r-26 and sulphur alkaliphilic thiorhodospira sibirica) is accelerated upon the addition of mn2+ jointly with bicarbonate (30-75 mm). the effect is not observed if mn2+ and hco3(-) have been replaced by mg2+ and hco2(-), respectively. the dependence of the effect on bic ... | 2008 | 17971330 |
| rhodobacter changlensis sp. nov., a psychrotolerant, phototrophic alphaproteobacterium from the himalayas of india. | a gram-negative, non-motile, oval to rod-shaped, psychrotolerant, phototrophic, purple non-sulfur bacterium (designated strain ja139t) was isolated from a snow sample from changla pass in the indian himalayas. strain ja139t had vesicular-type intracytoplasmic membrane structures and contained bacteriochlorophyll a and most probably spheroidene-like carotenoids. biotin, niacin and thiamine were required for growth of strain ja139t. phylogenetic analysis on the basis of 16s rrna gene sequences sho ... | 2007 | 17978219 |
| the gntr-like regulator taur activates expression of taurine utilization genes in rhodobacter capsulatus. | rhodobacter capsulatus can efficiently grow with taurine as the sole sulfur source. the products of the tpa-taur-xsc gene region are essential for this activity. taur, a mocr-like member of the gntr superfamily of transcriptional regulators, activates tpa transcription, as shown by analysis of wild-type and taur mutant strains carrying a tpa-lacz reporter fusion. activation of the tpa promoter requires taurine but is not inhibited by sulfate, which is the preferred sulfur source. taur directly b ... | 2008 | 17981966 |
| directed formation of micro- and nanoscale patterns of functional light-harvesting lh2 complexes. | the precision placement of the desired protein components on a suitable substrate is an essential prelude to any hybrid "biochip" device, but a second and equally important condition must also be met: the retention of full biological activity. here we demonstrate the selective binding of an optically active membrane protein, the light-harvesting lh2 complex from rhodobacter sphaeroides, to patterned self-assembled monolayers at the micron scale and the fabrication of nanometer-scale patterns of ... | 2007 | 17985885 |
| 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 |
| ultrafast structural dynamics in bluf domains: transient infrared spectroscopy of appa and its mutants. | the structural dynamics following photoexcitation of a photosensing bluf (blue light sensing using fad) domain protein have been investigated by ultrafast transient infrared spectroscopy. specifically, the transcriptional antirepressor appa from rhodobacter sphaeroides has been studied in the light and dark adapted forms and in photoactive and inactive mutants w104f and q63l. a transient absorption has been observed at 1666 cm(-1) which is a marker mode for the photoactive state of the protein. ... | 2007 | 18031038 |
| mutation of a single residue, beta-glutamate-20, alters protein-lipid interactions of light harvesting complex ii. | it is well established that assembly of the peripheral antenna complex, lh2, is required for proper photosynthetic membrane biogenesis in the purple bacterium rhodobacter sphaeroides. the underlying interactions are, as yet, not understood. here we examined the relationship between the morphology of the photosynthetic membrane and the lipid-protein interactions at the lh2-lipid interface. the non-bilayer lipid, phosphatidylethanolamine, is shown to be highly enriched in the boundary lipid phase ... | 2008 | 18034796 |
| 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 |
| electron spin relaxation enhancement measurements of interspin distances in human, porcine, and rhodobacter electron transfer flavoprotein-ubiquinone oxidoreductase (etf-qo). | electron transfer flavoprotein-ubiquinone oxidoreductase (etf-qo) is a membrane-bound electron transfer protein that links primary flavoprotein dehydrogenases with the main respiratory chain. human, porcine, and rhodobacter sphaeroides etf-qo each contain a single [4fe-4s](2+,1+) cluster and one equivalent of fad, which are diamagnetic in the isolated enzyme and become paramagnetic on reduction with the enzymatic electron donor or with dithionite. the anionic flavin semiquinone can be reduced fu ... | 2008 | 18037314 |
| inhibitor-complexed structures of the cytochrome bc1 from the photosynthetic bacterium rhodobacter sphaeroides. | the cytochrome bc(1) complex (bc(1)) is a major contributor to the proton motive force across the membrane by coupling electron transfer to proton translocation. the crystal structures of wild type and mutant bc(1) complexes from the photosynthetic purple bacterium rhodobacter sphaeroides (rsbc(1)), stabilized with the quinol oxidation (q(p)) site inhibitor stigmatellin alone or in combination with the quinone reduction (q(n)) site inhibitor antimycin, were determined. the high quality electron ... | 2008 | 18039651 |
| colorful niches of phototrophic microorganisms shaped by vibrations of the water molecule. | the photosynthetic pigments of phototrophic microorganisms cover different regions of the solar light spectrum. utilization of the light spectrum can be interpreted in terms of classical niche theory, as the light spectrum offers opportunities for niche differentiation and allows coexistence of species absorbing different colors of light. however, which spectral niches are available for phototrophic microorganisms? here, we show that the answer is hidden in the vibrations of the water molecule. ... | 2007 | 18043638 |
| phylogenomics and signature proteins for the alpha proteobacteria and its main groups. | alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. however, for these bacteria as a whole and for all of its major subgroups (viz. rhizobiales, rhodobacterales, rhodospirillales, rickettsiales, sphingomonadales and caulobacterales), very few or no distinctive molecular or biochemical characteristics are known. | 2007 | 18045498 |
| estimation of binding parameters for the protein-protein interaction using a site-directed spin labeling and epr spectroscopy. | sensitivity of the electron paramagnetic resonance (cw epr) to molecular tumbling provides potential means for studying processes of molecular association. it uses spin-labeled macromolecules, whose cw epr spectra may change upon binding to other macromolecules. when a spin-labeled molecule is mixed with its liganding partner, the epr spectrum constitutes a linear combination of spectra of the bound and unbound ligand (as seen in our example of spin-labeled cytochrome c(2) interacting with cytoc ... | 2008 | 18049817 |
| molecular assembly of zn porphyrin complexes using synthetic light-harvesting model polypeptides. | synthetic single alpha-helix hydrophobic polypeptides, which have similar amino acid sequences to the hydrophobic core in the native light-harvesting 1-beta polypeptide from rhodobacter sphaeroides, formed zn porphyrin complexes on a gold electrode, as well as in n-octyl-beta-glucoside micelles: this process is dependent on the structure of the pigments and the polypeptides. interestingly, an enhanced photoelectric current was observed when zn mesoporphyrin monomer complexed with the synthetic l ... | 2008 | 18049908 |
| 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 |
| low-temperature pulsed epr study at 34 ghz of the triplet states of the primary electron donor p865 and the carotenoid in native and mutant bacterial reaction centers of rhodobacter sphaeroides. | the photosynthetic charge separation in bacterial reaction centers occurs predominantly along one of two nearly symmetric branches of cofactors. low-temperature epr spectra of the triplet states of the chlorophyll and carotenoid pigments in the reaction center of rhodobacter sphaeroides r-26.1, 2.4.1 and two double-mutants gd(m203)/aw(m260) and lh(m214)/aw(m260) have been recorded at 34 ghz to investigate the relative activities of the "a" and "b" branches. the triplet states are found to derive ... | 2007 | 18052205 |
| 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 |
| structural elements involved in proton translocation by cytochrome c oxidase as revealed by backbone amide hydrogen-deuterium exchange of the e286h mutant. | cytochrome c oxidase is the terminal electron acceptor in the respiratory chains of aerobic organisms and energetically couples the reduction of oxygen to water to proton pumping across the membrane. the mechanisms of proton uptake, gating, and pumping have yet to be completely elucidated at the molecular level for these enzymes. for rhodobacter sphaeroides cytco (cytochrome aa3), it appears as though the e286 side chain of subunit i is a branching point from which protons are shuttled either to ... | 2008 | 18052347 |
| 5-aminolevulinic acid biosynthesis in escherichia coli coexpressing nadp-dependent malic enzyme and 5-aminolevulinate synthase. | 5-aminolevulinate (ala) synthase (e.c. 2.3.1.37), which mediates the pyridoxal phosphate-dependent condensation of glycine and succinyl-coa, encoded by the rhodobacter sphaeroides hema gene, enables escherichia coli strains to produce ala at a low level. to study the effect of the enhanced c4 metabolism of e. coli on ala biosynthesis, nadp-dependent malic enzyme (maeb, e.c. 1.1.1.40) was coexpressed with ala synthase in e. coli. the concentration of ala was two times greater in cells coexpressin ... | 2007 | 18062242 |
| mesaconyl-coenzyme a hydratase, a new enzyme of two central carbon metabolic pathways in bacteria. | the coenzyme a (coa)-activated c5-dicarboxylic acids mesaconyl-coa and beta-methylmalyl-coa play roles in two as yet not completely resolved central carbon metabolic pathways in bacteria. first, these compounds are intermediates in the 3-hydroxypropionate cycle for autotrophic co2 fixation in chloroflexus aurantiacus, a phototrophic green nonsulfur bacterium. second, mesaconyl-coa and beta-methylmalyl-coa are intermediates in the ethylmalonyl-coa pathway for acetate assimilation in various bacte ... | 2008 | 18065535 |
| cyclic dimeric gmp signaling and regulation of surface-associated developmental programs. | | 2008 | 18065536 |
| crystal structure of a protein, structurally related to glycosyltransferases, encoded in the rhodobacter blasticus atp operon. | the f1-atp synthase atp operon in the proteobacterium rhodobacter blasticus contains six open reading frames, encoding six hypothetical proteins. five of these subunits, in the stoichiometry (alphabeta)3gamma delta epsilon make up the catalytic f1-atp synthase complex similarly in bacteria, chloroplasts and mitochondria. the sixth gene of the r. blasticus atp operon, urf6, shows very little sequence homology to any protein of known structure or function. the gene has previously been cloned, the ... | 2008 | 18067873 |
| a new cryo-em single-particle ab initio reconstruction method visualizes secondary structure elements in an atp-fueled aaa+ motor. | the generation of ab initio three-dimensional (3d) models is a bottleneck in the studies of large macromolecular assemblies by single-particle cryo-electron microscopy. we describe here a novel method, in which established methods for two-dimensional image processing are combined with newly developed programs for joint rotational 3d alignment of a large number of class averages (rad) and calculation of 3d volumes from aligned projections (volrec). we demonstrate the power of the method by recons ... | 2008 | 18068723 |
| impact of mutations on the midpoint potential of the [4fe-4s]+1,+2 cluster and on catalytic activity in electron transfer flavoprotein-ubiquinone oxidoreductase (etf-qo). | electron-transfer flavoprotein-ubiquinone oxidoreductase (etf-qo) is an iron-sulfur flavoprotein that accepts electrons from electron-transfer flavoprotein (etf) and reduces ubiquinone from the q-pool. etf-qo contains a single [4fe-4s]2+,1+ cluster and one equivalent of fad, which are diamagnetic in the isolated oxidized enzyme and can be reduced to paramagnetic forms by enzymatic donors or dithionite. mutations were introduced by site-directed mutagenesis of amino acids in the vicinity of the i ... | 2008 | 18069858 |
| structural basis for the pufx-mediated dimerization of bacterial photosynthetic core complexes. | in rhodobacter (rba.) sphaeroides, the subunit pufx is involved in the dimeric organization of the core complex. here, we report the 3d reconstruction at 12 a by cryoelectron microscopy of the core complex of rba. veldkampii, a complex of approximately 300 kda without symmetry. the core complex is monomeric and constituted by a light-harvesting complex 1 (lh1) ring surrounding a uniquely oriented reaction center (rc). the lh1 consists of 15 resolved alpha/beta heterodimers and is interrupted. wi ... | 2007 | 18073116 |
| superoxide generation by chlorophyllide a reductase of rhodobacter sphaeroides. | chlorophyllide a reductase of rhodobacter sphaeroides, which were reconstituted with the purified subunits of bchx, bchy, and bchz, reduced ring b of chlorophyllide a using nadh under anaerobic conditions. interestingly, suppressor mutations rescuing the inability of r. sphaeroides fe-sod mutant to grow in succinate-based minimal medium were predominantly mapped to bchz subunit of chlorophyllide a reductase. the enzyme is labile in the presence of o(2). however, it generates superoxide at low o( ... | 2008 | 18079120 |
| hydrogen and polyhydroxybutyrate producing abilities of microbes from diverse habitats by dark fermentative process. | thirty five bacterial isolates from diverse environmental sources such as contaminated food, nitrogen rich soil, activated sludges from pesticide and oil refineries effluent treatment plants were found to belong to bacillus, bordetella, enterobacter, proteus, and pseudomonas sp. on the basis of 16s rrna gene sequence analysis. under dark fermentative conditions, maximum hydrogen (h(2)) yields (mol/mol of glucose added) were recorded to be 0.68 with enterobacter aerogenes egu16 followed by 0.63 w ... | 2008 | 18083024 |
| optimisation of nmr dynamic models i. minimisation algorithms and their performance within the model-free and brownian rotational diffusion spaces. | the key to obtaining the model-free description of the dynamics of a macromolecule is the optimisation of the model-free and brownian rotational diffusion parameters using the collected r (1), r (2) and steady-state noe relaxation data. the problem of optimising the chi-squared value is often assumed to be trivial, however, the long chain of dependencies required for its calculation complicates the model-free chi-squared space. convolutions are induced by the lorentzian form of the spectral dens ... | 2008 | 18085410 |
| employing rhodobacter sphaeroides to functionally express and purify human g protein-coupled receptors. | g protein-coupled receptors (gpcrs) represent the largest class of cell surface receptors and play crucial roles in many cellular and physiological processes. functional production of recombinant gpcrs is one of the main bottlenecks to obtaining structural information. here, we report the use of a novel bacterial expression system based on the photosynthetic bacterium rhodobacter sphaeroides for the production of human recombinant gpcrs. the advantage of employing r. sphaeroides as a host lies i ... | 2008 | 18095871 |
| ammonia-induced formation of an amtb-glnk complex is not sufficient for nitrogenase regulation in the photosynthetic bacterium rhodobacter capsulatus. | a series of rhodobacter capsulatus amtb variants were created and assessed for effects on ammonia transport, formation of amtb-glnk complexes, and regulation of nitrogenase activity and nifh adp-ribosylation. confirming previous reports, h193 and h342 were essential for ammonia transport and the replacement of aspartate 185 with glutamate reduced ammonia transport. several amino acid residues, f131, d334, and d335, predicted to be critical for amtb activity, are shown here for the first time by ... | 2008 | 18156251 |