| membrane curvature induced by aggregates of lh2s and monomeric lh1s. | the photosynthetic apparatus of purple bacteria is contained within organelles called chromatophores, which form as extensions of the cytoplasmic membrane. the shape of these chromatophores can be spherical (as in rhodobacter sphaeroides), lamellar (as in rhodopseudomonas acidophila and phaeospirillum molischianum), or tubular (as in certain rb. sphaeroides mutants). chromatophore shape is thought to be influenced by the integral membrane proteins light harvesting complexes i and ii (lh1 and lh2 ... | 2009 | 19948127 |
| enhanced bio-hydrogen production from corncob by a two-step process: dark- and photo-fermentation. | enhanced bio-hydrogen production from pretreated corncob by integrating dark-fermentation with photo-fermentation process was investigated in this study. in the first step, the maximum bio-hydrogen yield and rate from corncob by dark-fermentation was 120.3+/-5.2 ml h(2)/g-corncob and 150 ml h(2)/(lh), respectively. in the second step, a hydrogen yield of 713.6+/-44.1 ml h(2)/g-cod was obtained from digesting the effluent of dark-fermentation by photosynthetic bacteria. meanwhile, cod removal eff ... | 2010 | 19963373 |
| identification, functional studies, and genomic comparisons of new members of the nnrr regulon in rhodobacter sphaeroides. | analysis of the rhodobacter sphaeroides 2.4.3 genome revealed four previously unidentified sequences similar to the binding site of the transcriptional regulator nnrr. expression studies demonstrated that three of these sequences are within the promoters of genes, designated paz, noref, and cdga, in the nnrr regulon, while the status of the fourth sequence, within the tat operon promoter, remains uncertain. nnrv, under control of a previously identified nnrr site, was also identified. paz encode ... | 2010 | 19966004 |
| acetate permease (actp) is responsible for tellurite (teo32-) uptake and resistance in cells of the facultative phototroph rhodobacter capsulatus. | the highly toxic oxyanion tellurite has to enter the cytoplasm of microbial cells in order to fully express its toxicity. here we show that in the phototroph rhodobacter capsulatus, tellurite exploits acetate permease (actp) to get into the cytoplasm and that the levels of resistance and uptake are linked. | 2010 | 19966028 |
| crystal structure of bacterioferritin from rhodobacter sphaeroides. | iron is essential for the survival of organisms, but either excess or deficient levels of iron induce oxidative stress, thereby causing cell damage. as a result, iron regulation is essential for proper cell growth and proliferation in most organisms. bacterioferritin is a ferritin-like family protein that contains a heme molecule and a ferroxidase site at the di-iron center. this protein plays a primary role in intracellular iron storage for iron homeostasis, as well as in the maintenance of iro ... | 2010 | 19968959 |
| light harvesting complex ii b850 excitation dynamics. | the dynamics of excitation energy transfer within the b850 ring of light harvesting complex 2 from rhodobacter sphaeroides and between neighboring b850 rings is investigated by means of dissipative quantum mechanics. the assumption of boltzmann populated donor states for the calculation of intercomplex excitation transfer rates by generalized forster theory is shown to give accurate results since intracomplex exciton relaxation to near-boltzmann population exciton states occurs within a few pico ... | 2009 | 20001083 |
| one-step purification of functional light-harvesting 2 complex from rhodobacter sphaeroides. | most common method for isolation of light-harvesting 2 complex (lh2) is very time-consuming. in our present work functional lh2 complex was one-step rapidly purified from rhodobacter sphaeroides by metal-ion affinity chromatography. the purified lh2 complex exhibited high activity in light absorption and energy transfer. our present work provides an efficient approach for preparation of functional lh2 complex. | 2010 | 20015026 |
| the electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-cidnp 13c nmr. | composed of the two bacteriochlorophyll cofactors, p(l) and p(m), the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of rhodobacter sphaeroides. under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. the occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-cidnp). this effect can be use ... | 2009 | 20018724 |
| modifications of protein environment of the [2fe-2s] cluster of the bc1 complex: effects on the biophysical properties of the rieske iron-sulfur protein and on the kinetics of the complex. | the rate-determining step in the overall turnover of the bc(1) complex is electron transfer from ubiquinol to the rieske iron-sulfur protein (isp) at the q(o)-site. structures of the isp from rhodobacter sphaeroides show that serine 154 and tyrosine 156 form h-bonds to s-1 of the [2fe-2s] cluster and to the sulfur atom of the cysteine liganding fe-1 of the cluster, respectively. these are responsible in part for the high potential (e(m)(,7) approximately 300 mv) and low pk(a) (7.6) of the isp, w ... | 2010 | 20023300 |
| ascochlorin is a novel, specific inhibitor of the mitochondrial cytochrome bc1 complex. | ascochlorin is an isoprenoid antibiotic that is produced by the phytopathogenic fungus ascochyta viciae. similar to ascofuranone, which specifically inhibits trypanosome alternative oxidase by acting at the ubiquinol binding domain, ascochlorin is also structurally related to ubiquinol. when added to the mitochondrial preparations isolated from rat liver, or the yeast pichia (hansenula) anomala, ascochlorin inhibited the electron transport via coq in a fashion comparable to antimycin a and stigm ... | 2010 | 20025846 |
| comparison of different mixed cultures for bio-hydrogen production from ground wheat starch by combined dark and light fermentation. | composition of the mixed culture was varied in combined dark-light fermentation of wheat powder starch in order to improve hydrogen gas formation rate and yield. heat-treated anaerobic sludge and pure culture of clostridium beijerinckii (dsmz 791t) were combined with two different light fermentation bacteria of rhodobacter sphaeroides (rs-nrrl and rs-rv) in order to select a more suitable mixture resulting in high hydrogen yield and formation rate. a combination of the anaerobic sludge and rs-nr ... | 2010 | 20033469 |
| light harvesting, energy transfer and electron cycling of a native photosynthetic membrane adsorbed onto a gold surface. | photosynthetic membranes comprise a network of light harvesting and reaction center pigment-protein complexes responsible for the primary photoconversion reactions: light absorption, energy transfer and electron cycling. the structural organization of membranes of the purple bacterial species rb. sphaeroides has been elucidated in most detail by means of polarized light spectroscopy and atomic force microscopy. here we report a functional characterization of native and untreated membranes of the ... | 2010 | 20036635 |
| coproporphyrin excretion and low thiol levels caused by point mutation in the rhodobacter sphaeroides s-adenosylmethionine synthetase gene. | a spontaneous mutant of rhodobacter sphaeroides f. sp. denitrificans il-106 was found to excrete a large amount of a red compound identified as coproporphyrin iii, an intermediate in bacteriochlorophyll and heme synthesis. the mutant, named porf, is able to grow under phototrophic conditions but has low levels of intracellular cysteine and glutathione and overexpresses the cysteine synthase cysk. the expression of molybdoenzymes such as dimethyl sulfoxide (dmso) and nitrate reductases is also af ... | 2010 | 20038586 |
| the apparent malate synthase activity of rhodobacter sphaeroides is due to two paralogous enzymes, (3s)-malyl-coenzyme a (coa)/{beta}-methylmalyl-coa lyase and (3s)- malyl-coa thioesterase. | assimilation of acetyl coenzyme a (acetyl-coa) is an essential process in many bacteria that proceeds via the glyoxylate cycle or the ethylmalonyl-coa pathway. in both assimilation strategies, one of the final products is malate that is formed by the condensation of acetyl-coa with glyoxylate. in the glyoxylate cycle this reaction is catalyzed by malate synthase, whereas in the ethylmalonyl-coa pathway the reaction is separated into two proteins: malyl-coa lyase, a well-known enzyme catalyzing t ... | 2010 | 20047909 |
| deciphering chemotaxis pathways using cross species comparisons. | chemotaxis is the process by which motile bacteria sense their chemical environment and move towards more favourable conditions. escherichia coli utilises a single sensory pathway, but little is known about signalling pathways in species with more complex systems. | 2010 | 20064255 |
| [use of the standard theory of electronic transitions in the description of oscillations in the kinetics of electron transfer in reaction centers of purple bacteria]. | the standard theory of the electron transfer between donor and acceptor molecules was used to describe oscillations in the reduction kinetics of the intermediate electron acceptor ba and the primary electron acceptor ha. the kinetics of the reduction of ba and ha were simulated on the basis of the model in which one and two accepting modes were used. a principal experiment is offered for the selection of the suitable theory for adequate description of oscillations in the kinetics of electron tra ... | 2009 | 20067182 |
| the influence of hydrogen bonds on the electronic structure of light-harvesting complexes from photosynthetic bacteria. | the influence of hydrogen bonds on the electronic structure of the light-harvesting i complex from rhodobacter sphaeroides has been examined by site-directed mutagenesis, steady-state optical spectroscopy, and fourier-transform resonance raman spectroscopy. shifts of 4-23 nm in the q(y) absorption band were observed in seven mutants with single or double changes at leu alpha44, trp alpha43, and trp beta48. resonance raman spectra were consistent with the loss of a hydrogen bond with the alterati ... | 2010 | 20067231 |
| structural and spectroscopic consequences of hexacoordination of a bacteriochlorophyll cofactor in the rhodobacter sphaeroides reaction center . | the structural and functional consequences of changing the coordination state of one of the bacteriochlorophyll (bchl) cofactors in the purple bacterial reaction center have been explored. a combination of steady state spectroscopy and x-ray crystallography was used to demonstrate that mutagenesis of residue 181 of the l-polypeptide from phe to arg (fl181r) causes the bchl at the accessory (b(b)) position on the so-called inactive cofactor branch to become hexacoordinated, with no significant ch ... | 2010 | 20112981 |
| a pathogenic mutation in cytochrome c oxidase results in impaired proton pumping while retaining o(2)-reduction activity. | in this work we have investigated the effect of a pathogenic mitochondrial dna mutation found in human colon cells, at a functional-molecular level. the mutation results in the amino-acid substitution tyr19his in subunit i of the human cytco and it is associated with respiratory deficiency. it was introduced into rhodobacter sphaeroides, which carries a cytochrome c oxidase (cytochrome aa(3)) that serves as a model of the mitochondrial counterpart. the residue is situated in the middle of a path ... | 2010 | 20117076 |
| dependence of catalytic activity on driving force in solution assays and protein film voltammetry: insights from the comparison of nitrate reductase mutants. | rhodobacter sphaeroides periplasmic nitrate reductase (rs napab) is one of the enzymes whose assays give odd results: in spectrophotometric assays with methyl viologen as the electron donor, the activity increases as the reaction progresses, whereas the driving force provided by the soluble redox partner decreases; in protein film voltammetry (pfv), whereby the enzyme directly exchanges electrons with an electrode, the activity of napab decreases at large overpotential, whereas a monotonic incre ... | 2010 | 20146468 |
| conductometric method for the rapid characterization of the substrate specificity of amine-transaminases. | amine-transaminases (atas, omega-transaminases, omega-ta) are plp-dependent enzymes that catalyze amino group transfer reactions. in contrast to the widespread and well-known amino acid-transaminases, atas are able to convert substrates lacking an alpha-carboxylic functional group. they have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, which are frequently used as building blocks for the preparation of numerous pharmaceuticals. ha ... | 2010 | 20148590 |
| optimized enzymatic preparation of 1-deoxy-d-xylulose 5-phosphate. | the preparation of 1-deoxy-d-xylulose 5-phosphate, the key intermediate of mep biosynthetic pathway for terpenoids by using recombinant 1-deoxy-d-xylulose 5-phosphate synthase of rhodobacter capsulatus was optimized. the simple one-pot synthesis coupling with a newly established ion-exchange purification process affords the target compound with more than 80% yield and high purity (>95%). the procedure can also be employed to synthesize isotope labeled 1-deoxy-d-xylulose 5-phosphate by using isot ... | 2010 | 20149406 |
| exploring electron spin-spin interactions of paramagnetic iron and radical cations of bacteriochlorophyll from oxidized lh1 in the presence of electron transfer in the frozen state. | cation free radicals of bacteriochlorophyll (bchl(+)) are formed in the light harvesting complex 1 (lh1) of photosynthetic bacteria upon oxidation by potassium ferricyanide. unusually narrow epr line widths are observed for bchl(+) in the frozen state. these narrow line widths are consistent with a molecular-wire behavior where rapid electron/hole transfer occurs between the bchl constituents of the pigment array responsible for light harvesting in bacterial photosynthesis. however, in addition ... | 2010 | 20151665 |
| structural model and excitonic properties of the dimeric rc-lh1-pufx complex from rhodobacter sphaeroides. | the light-harvesting apparatus of the purple bacterial photosynthetic unit consists of a pool of peripheral light-harvesting complexes that transfer excitation energy to a reaction center (rc) via the surrounding pigment-protein complex lh1. recent electron microscopy and atomic force microscopy studies have revealed that rc-lh1 units of rhodobacter sphaeroides form membrane-bending dimeric complexes together with the polypeptide pufx. we present a structural model for these rc-lh1-pufx dimeric ... | 2009 | 20161332 |
| using structural information to change the phosphotransfer specificity of a two-component chemotaxis signalling complex. | two-component signal transduction pathways comprising histidine protein kinases (hpks) and their response regulators (rrs) are widely used to control bacterial responses to environmental challenges. some bacteria have over 150 different two-component pathways, and the specificity of the phosphotransfer reactions within these systems is tightly controlled to prevent unwanted crosstalk. one of the best understood two-component signalling pathways is the chemotaxis pathway. here, we present the 1.4 ... | 2010 | 20161720 |
| bio-hydrogen production using a two-stage fermentation process. | a two-stage fermentation process consisting of dark and photo-fermentation periods was carried out in a batch reactor. in the first stage, glucose was fermented in the dark stage using clostridium saccharoperbutylacetonicum n1-4 (atcc 13564; csn1-4) to produce acetate, co2 and h2. the acetate produced in the first stage is fermented to h2 and co2 by rhodobacter sphaeroides ncimb 8253 for further hydrogen production in the second, illuminated stage. the yield of hydrogen in the first stage was ab ... | 2009 | 20180320 |
| variable proton-pumping stoichiometry in structural variants of cytochrome c oxidase. | cytochrome c oxidase is a multisubunit membrane-bound enzyme, which catalyzes oxidation of four molecules of cytochrome c2+ and reduction of molecular oxygen to water. the electrons are taken from one side of the membrane while the protons are taken from the other side. this topographical arrangement results in a charge separation that is equivalent to moving one positive charge across the membrane for each electron transferred to o2. in this reaction part of the free energy available from o2 re ... | 2010 | 20184858 |
| partial steps of charge translocation in the nonpumping n139l mutant of rhodobacter sphaeroides cytochrome c oxidase with a blocked d-channel. | the n139l substitution in the d-channel of cytochrome oxidase from rhodobacter sphaeroides results in an approximately 15-fold decrease in the turnover number and a loss of proton pumping. time-resolved absorption and electrometric assays of the f --> o transition in the n139l mutant oxidase result in three major findings. (1) oxidation of the reduced enzyme by o(2) shows approximately 200-fold inhibition of the f --> o step (k approximately 2 s(-1) at ph 8) which is not compatible with enzyme t ... | 2010 | 20192226 |
| targeting the active site gate to yield hyperactive variants of 5-aminolevulinate synthase. | the rate of porphyrin biosynthesis in mammals is controlled by the activity of the pyridoxal 5'-phosphate-dependent enzyme 5-aminolevulinate synthase (ec 2.3.1.37). based on the postulate that turnover in this enzyme is controlled by conformational dynamics associated with a highly conserved active site loop, we constructed a variant library by targeting imperfectly conserved noncatalytic loop residues and examined the effects on product and porphyrin production. functional loop variants of the ... | 2010 | 20194506 |
| coenzyme q10 production in a 150-l reactor by a mutant strain of rhodobacter sphaeroides. | for the commercial production of coq(10), batch-type fermentations were attempted in a 150-l fermenter using a mutant strain of r. sphaeroides. optimum temperature and initial aeration rate were found to be 30 degrees c and 2 vvm, respectively. under optimum fermentation conditions, the maximum value of specific coq(10) content was achieved reproducibly as 6.34 mg/g dcw after 24 h, with 3.02 g/l of dcw. during the fermentation, aeration shift (from the adequate aeration at the early growth phase ... | 2010 | 20195885 |
| an investigation of slow charge separation in a tyrosine m210 to tryptophan mutant of the rhodobacter sphaeroides reaction center by femtosecond mid-infrared spectroscopy. | energy and electron transfer in a tyrosine m210 to tryptophan (ym210w) mutant of the rhodobacter sphaeroides reaction center (rc) were investigated through time-resolved visible pump/mid-infrared (mid-ir) probe spectroscopy at room temperature, with the aim to further characterize the primary charge separated states in the rc. this mutant is known to display slow and multi-exponential charge separation, and was used in earlier work to prove the existence of an alternative route for charge separa ... | 2010 | 20200747 |
| action spectroscopy on dense samples of photosynthetic reaction centers of rhodobacter sphaeroides wt based on nanosecond laser-flash c photo-cidnp mas nmr. | photochemically induced dynamic nuclear polarization magic-angle spinning nuclear magnetic resonance (photo-cidnp mas nmr) allows for the investigation of the electronic structure of the photochemical machinery of photosynthetic reaction centers (rcs) at atomic resolution. for such experiments, either continuous radiation from white xenon lamps or green laser pulses are applied to optically dense samples. in order to explore their optical properties, optically thick samples of isolated and quino ... | 2010 | 20208980 |
| atp-induced conformational dynamics in the aaa+ motor unit of magnesium chelatase. | mg-chelatase catalyzes the first committed step of the chlorophyll biosynthetic pathway, the atp-dependent insertion of mg(2+) into protoporphyrin ix (ppix). here we report the reconstruction using single-particle cryo-electron microscopy of the complex between subunits bchd and bchi of rhodobacter capsulatus mg-chelatase in the presence of adp, the nonhydrolyzable atp analog amppnp, and atp at 7.5 a, 14 a, and 13 a resolution, respectively. we show that the two aaa+ modules of the subunits form ... | 2010 | 20223218 |
| functional prokaryotic rubisco from an oceanic metagenomic library. | culture-independent studies have indicated that there is significant diversity in the ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) enzymes used by marine, freshwater, and terrestrial autotrophic bacteria. surprisingly, little is known about the catalytic properties of many environmentally significant rubisco enzymes. because one of the goals of rubisco research is to somehow modify or select for rubisco molecules with improved kinetic properties, a facile means to isolate functional ... | 2010 | 20228113 |
| long-range energy propagation in nanometer arrays of light harvesting antenna complexes. | here we report the first observation of long-range transport of excitation energy within a biomimetic molecular nanoarray constructed from lh2 antenna complexes from rhodobacter sphaeroides. fluorescence microscopy of the emission of light after local excitation with a diffraction-limited light beam reveals long-range transport of excitation energy over micrometer distances, which is much larger than required in the parent bacterial system. the transport was established from the influence of act ... | 2010 | 20232894 |
| overlapping alternative sigma factor regulons in the response to singlet oxygen in rhodobacter sphaeroides. | organisms performing photosynthesis in the presence of oxygen have to cope with the formation of highly reactive singlet oxygen ((1)o(2)) and need to mount an adaptive response to photooxidative stress. here we show that the alternative sigma factors rpoh(i) and rpoh(ii) are both involved in the (1)o(2) response and in the heat stress response in rhodobacter sphaeroides. we propose rpoh(ii) to be the major player in the (1)o(2) response, whereas rpoh(i) is more important for the heat stress resp ... | 2010 | 20304993 |
| blocking the k-pathway still allows rapid one-electron reduction of the binuclear center during the anaerobic reduction of the aa3-type cytochrome c oxidase from rhodobacter sphaeroides. | the k-pathway is one of the two proton-input channels required for function of cytochrome c oxidase. in the rhodobacter sphaeroides cytochrome c oxidase, the k-channel starts at glu101 in subunit ii, which is at the surface of the protein exposed to the cytoplasm, and runs to tyr288 at the heme a3/cub active site. mutations of conserved, polar residues within the k-channel block or inhibit steady state oxidase activity. a large body of research has demonstrated that the k-channel is required to ... | 2010 | 20307488 |
| endor study of charge migration in photosynthetic arrays of rhodobacter sphaeroides. | the chemistry of bacterial photosynthesis begins in the photosynthetic reaction centre (rc), a protein complex containing a series of electron donor and acceptor molecules. although the pigments of the rc can absorb light to operate the photochemistry, the bulk of the light is captured in special pigmented proteins, the light harvesting complexes (lhcs), that then transfer the energy to the rc. ordinarily, the lhcs do not participate in chemical reactions during photosynthesis such that lhcs do ... | 2010 | 20340122 |
| derepressive effect of nh4+ on hydrogen production by deleting the glna1 gene in rhodobacter sphaeroides. | purple non-sulfur (pns) bacteria produce hydrogen by photofermentation of organic acids in wastewater. however, nh(4)(+) in wastewater may inhibit hydrogen synthesis by repressing the expression and activity of nitrogenase, the enzyme catalyzing hydrogen production in pns bacteria. in this study, the rhodobacter sphaeroides 6016 glna gene encoding glutamine synthetase (gs) was knocked out by homologous recombination, and the effects on hydrogen production and nitrogenase activity were examined. ... | 2010 | 20340141 |
| b-branch electron transfer in the photosynthetic reaction center of a rhodobacter sphaeroides quadruple mutant. q- and w-band electron paramagnetic resonance studies of triplet and radical-pair cofactor states. | the directionality of light-induced charge transfer in bacterial photosynthetic reaction centers (rcs) with respect to their a and b cofactor branches is still poorly understood on the electronic level. a prominent example is primary electron transfer in the rcs from the purple bacterium rb. sphaeroides. site-directed mutants with specific alterations of the cofactor binding sites with respect to the native system can deliver useful information toward a better understanding of the directionality ... | 2010 | 20345158 |
| ferredoxin molecular thin film with intrinsic switching mechanism for biomemory application. | a biomemory device consisting of cysteine modified ferredoxin molecules which possess a memory effect via a charge transfer mechanism was developed. for achieving an efficient bioelectronic device, cysteine modified ferredoxin was developed by embodying cysteine residues in ferredoxin by site--directed mutagenesis method to directly coordinate with the gold (au) surface without use of any additional linkers. the thin film formation of ferredoxin molecules on au electrode is confirmed by surface ... | 2010 | 20358926 |
| ctpa, a copper-translocating p-type atpase involved in the biogenesis of multiple copper-requiring enzymes. | the ctpa (ccoi) gene product, a putative inner membrane copper-translocating p1b-type atpase present in many bacteria, has been shown to be involved only in the cbb(3) assembly in rhodobacter capsulatus and bradyrhizobium japonicum. ctpa was disrupted in rubrivivax gelatinosus, and the mutants showed a drastic decrease in both cbb(3) and caa(3) oxidase activities. inactivation of ctpa results also in a decrease in the amount of the nitrous oxide reductase, nosz. this pleiotropic phenotype could ... | 2010 | 20363758 |
| loss of the response regulator ctra causes pleiotropic effects on gene expression but does not affect growth phase regulation in rhodobacter capsulatus. | the purple nonsulfur photosynthetic bacterium rhodobacter capsulatus has been extensively studied for its metabolic versatility as well as for production of a gene transfer agent called rcgta. production of rcgta is highest in the stationary phase of growth and requires the response regulator protein ctra. the ctra protein in caulobacter crescentus has been thoroughly studied for its role as an essential, master regulator of the cell cycle. although the ctra protein in r. capsulatus shares a hig ... | 2010 | 20363938 |
| decoherence dynamics of coherent electronic excited states in the photosynthetic purple bacterium rhodobacter sphaeroides. | in this paper, we present a theoretical description to the quantum coherence and decoherence phenomena of energy transfer in photosynthesis observed in a recent experiment [science 316, 1462 (2007)]. as a successive two-color laser pulses with selected frequencies cast on a sample of the photosynthetic purple bacterium rb. sphaeroides two resonant excitations of electrons in chromophores can be generated. however, this effective two-level subsystem will interact with its protein environment and ... | 2010 | 20365398 |
| examination of stability of mutant photosynthetic reaction center of rhodobacter sphaeroides i(l177)h and determination of location of bacteriochlorophyll covalently bound to the protein. | we demonstrated earlier that as a result of the i(l177)h mutation in the photosynthetic reaction center (rc) of the bacterium rhodobacter sphaeroides, one of the bacteriochlorophylls (bchl) binds with the l-subunit, simultaneously raising coordination stability of the central magnesium atom of the bacteriochlorophyll associated with the protein. in this study, spectral properties of wild type rc and i(l177)h in the presence of urea and sds as well as at 48 degrees c were examined. it is shown th ... | 2010 | 20367608 |
| femtosecond absorption band formation at 1080 and 1020 nm as an indication of charge-separated states p(a)delta+ p7(b)delta- and p+ b(a)- in photosynthetic reaction centers of the purple bacterium rhodobacter sphaeroides. | | 2010 | 20380157 |
| the effect of aeration, agitation and light on biohydrogen production by rhodobacter sphaeroides ncimb 8253. | photo fermentation is a biological process that can be applied for hydrogen production. the process is environmental friendly which is operated under mild conditions using renewable resources. in order to increase yield of h2 produced by rhodobacter sphaeroides, some experimental factors that may enhance h2 production were studied. the effect of operating parameters including agitation, aeration and light on hydrogen production using r. sphaeroides ncimb 8253 was investigated. rhodobacter sphaer ... | 2009 | 20384278 |
| expression of bacterial tyrosine ammonia-lyase creates a novel p-coumaric acid pathway in the biosynthesis of phenylpropanoids in arabidopsis. | some flavonoids are considered as beneficial compounds because they exhibit anticancer or antioxidant activity. in higher plants, flavonoids are secondary metabolites that are derived from phenylpropanoid biosynthetic pathway. a large number of phenylpropanoids are generated from p-coumaric acid, which is a derivative of the primary metabolite, phenylalanine. the first two steps in the phenylpropanoid biosynthetic pathway are catalyzed by phenylalanine ammonia-lyase and cinnamate 4-hydroxylase, ... | 2010 | 20396902 |
| x-ray crystal structure of the light-independent protochlorophyllide reductase. | photosynthetic organisms adopt two different strategies for the reduction of the c17 = c18 double bond of protochlorophyllide (pchlide) to form chlorophyllide a, the direct precursor of chlorophyll a (refs 1-4). the first involves the activity of the light-dependent pchlide oxidoreductase, and the second involves the light-independent (dark-operative) pchlide oxidoreductase (dpor). dpor is a nitrogenase-like enzyme consisting of two components, l-protein (a bchl dimer) and nb-protein (a bchn-bch ... | 2010 | 20400946 |
| homology modeling and docking study of xanthine oxidase of arthrobacter sp. xl26. | hyperuricemia is a condition of defective purine metabolism characterized with elevated serum uric acid (ua) level that further leads to gout and gouty nephrolithiasis disorders. gout is a world wide distributed rheumatic disease comprises 1% of the total population and still is in increasing state. one of the factors contributing to overproduction of ua is the hydroxylation of xanthine catalyzed by xanthine oxidase (xo). in the present study, 3d modeling of arthrobacter sp. xl26 (xodb) protein ... | 2010 | 20403378 |
| structural insight into substrate differentiation of the sugar-metabolizing enzyme galactitol dehydrogenase from rhodobacter sphaeroides d. | galactitol 2-dehydrogenase (gatdh) belongs to the protein superfamily of short-chain dehydrogenases. as an enzyme capable of the stereo- and regioselective modification of carbohydrates, it exhibits a high potential for application in biotechnology as a biocatalyst. we have determined the crystal structure of the binary form of gatdh in complex with its cofactor nad(h) and of the ternary form in complex with nad(h) and three different substrates. the active form of gatdh constitutes a homo-tetra ... | 2010 | 20410293 |
| eukaryotic behaviour of a prokaryotic energy-transducing membrane: fully detached vesicular organelles arise by budding from the rhodobacter sphaeroides intracytoplasmic photosynthetic membrane. | a major feature that distinguishes prokaryotic organisms from eukaryotes is their less complex internal structure, in which all membrane-associated functions are thought to be present within a continuous lipid-protein bilayer, rather than with distinct organelles. contrary to this notion, as described by tucker and co-workers in this issue of molecular microbiology, the application of cryo-electron tomography to the purple bacterium rhodobacter sphaeroides has demonstrated a heretofore unrecogni ... | 2010 | 20412442 |
| complete genome sequence of the photosynthetic purple nonsulfur bacterium rhodobacter capsulatus sb 1003. | rhodobacter capsulatus sb 1003 belongs to the group of purple nonsulfur bacteria. its genome consists of a 3.7-mb chromosome and a 133-kb plasmid. the genome encodes genes for photosynthesis, nitrogen fixation, utilization of xenobiotic organic substrates, and synthesis of polyhydroxyalkanoates. these features made it a favorite research tool for studying these processes. here we report its complete genome sequence. | 2010 | 20418398 |
| decoupling mutations in the d-channel of the aa(3)-type cytochrome c oxidase from rhodobacter sphaeroides suggest that a continuous hydrogen-bonded chain of waters is essential for proton pumping. | the aa(3)-type cytochrome c oxidase from rhodobacter sphaeroides utilizes two proton-input channels to provide all the protons for chemistry (water formation) and proton pumping. the d-channel is responsible for the uptake of all pumped protons, four protons per o(2). several substitutions of either n139 or n207, near the entrance of the d-channel, were previously reported to decouple the proton pump from oxidase activity. in this work, the characteristics of additional mutations in this region ... | 2010 | 20441187 |
| structural refinement of a key tryptophan residue in the bluf photoreceptor appa by ultraviolet resonance raman spectroscopy. | the flavin-adenine-dinucleotide-binding bluf domain constitutes a new class of blue-light receptors, and the n-terminal domain of appa is a representative of this family. the bluf domain is of special interest because it uses a rigid flavin rather than an isomerizable chromophore, such as a rhodopsin or phytochrome, for its light-activation process. crystal and solution structures of several bluf domains were recently obtained, and their overall structures are consistent. however, there is a key ... | 2010 | 20441759 |
| membrane invagination in rhodobacter sphaeroides is initiated at curved regions of the cytoplasmic membrane, then forms both budded and fully detached spherical vesicles. | the purple phototrophic bacteria synthesize an extensive system of intracytoplasmic membranes (icm) in order to increase the surface area for absorbing and utilizing solar energy. rhodobacter sphaeroides cells contain curved membrane invaginations. in order to study the biogenesis of icm in this bacterium mature (icm) and precursor (upper pigmented band - upb) membranes were purified and compared at the single membrane level using electron, atomic force and fluorescence microscopy, revealing fun ... | 2010 | 20444085 |
| binding of imidazole to the heme of cytochrome c1 and inhibition of the bc1 complex from rhodobacter sphaeroides: i. equilibrium and modeling studies. | we have used imidazole (im) and n-methylimidazole (meim) as probes of the heme-binding cavity of membrane-bound cytochrome (cyt) c(1) in detergent-solubilized bc(1) complex from rhodobacter sphaeroides. imidazole binding to cyt c(1) substantially lowers the midpoint potential of the heme and fully inhibits bc(1) complex activity. temperature dependences showed that binding of im (k(d) approximately 330 microm, 25 degrees c, ph 8) is enthalpically driven (deltah(0) = -56 kj/mol, deltas(0) = -121 ... | 2010 | 20448035 |
| binding of imidazole to the heme of cytochrome c1 and inhibition of the bc1 complex from rhodobacter sphaeroides: ii. kinetics and mechanism of binding. | the kinetics of imidazole (im) and n-methylimidazole (meim) binding to oxidized cytochrome (cyt) c(1) of detergent-solubilized bc(1) complex from rhodobacter sphaeroides are described. the rate of formation of the cyt c(1)-im complex exhibited three separated regions of dependence on the concentration of imidazole: (i) below 8 mm im, the rate increased with concentration in a parabolic manner; (ii) above 20 mm, the rate leveled off, indicating a rate-limiting conformational step with lifetime ap ... | 2010 | 20448037 |
| relevance of individual mo-box nucleotides to dna binding by the related molybdenum-responsive regulators mopa and mopb in rhodobacter capsulatus. | either of two related molybdenum-responsive regulators, mopa and mopb, of rhodobacter capsulatus is sufficient to repress the nitrogen-fixation gene anfa. in contrast, mopa (but not mopb) activates mop, which codes for a molybdate (mo)-binding molbindin. both regulators bind to conserved cis-regulatory elements called mo-boxes. single-base substitution of two highly conserved nucleotides within the anfa-mo-box (t21c and c24t) had little effect on regulator binding and anfa expression as shown by ... | 2010 | 20455946 |
| myoglobin embedded in saccharide amorphous matrices: water-dependent domains evidenced by small angle x-ray scattering. | we report small angle x-ray scattering (saxs) measurements performed on samples of carboxy-myoglobin (mbco) embedded in low-water trehalose glasses. results showed that, in such samples, "low-protein" trehalose-water domains are present, surrounded by a protein-trehalose-water background; such finding is supported by infrared spectroscopy (ftir) measurements. these domains, which do not appear in the absence of the protein and in analogous sucrose systems, preferentially incorporate the incoming ... | 2010 | 20463993 |
| a plug-based microfluidic system for dispensing lipidic cubic phase (lcp) material validated by crystallizing membrane proteins in lipidic mesophases. | this paper presents a plug-based microfluidic system to dispense nanoliter-volume plugs of lipidic cubic phase (lcp) material and subsequently merge the lcp plugs with aqueous plugs. this system was validated by crystallizing membrane proteins in lipidic mesophases, including lcp. this system allows for accurate dispensing of lcp material in nanoliter volumes, prevents inadvertent phase transitions that may occur due to dehydration by enclosing lcp in plugs, and is compatible with the traditiona ... | 2010 | 20473353 |
| assessment of an internal reference gene in rhodobacter sphaeroides grown under cobalt exposure. | aim of this study is the identification of an appropriate internal reference gene to quantify gene transcripts isolated from rhodobacter (r.) sphaeroides cells grown in presence of high concentrations of cobalt ions. rna was isolated using a commercial kit protocol ad-hoc modified. several primer pairs were used to perform reverse transcription pcr and real-time pcr to assess the suitable internal reference gene whose expression is not affected by cobalt ions, identified with the gene rsp0154.th ... | 2010 | 20473961 |
| photosynthetic bacteria treatment of synthetic soybean wastewater: direct degradation of macromolecules. | in order to investigate the possibility of photosynthetic bacteria (psb) to degrade macromolecules directly and to find an economic psb wastewater treatment method without energy input, a new strain of psb, z08, was used to treat synthetic soybean wastewater. coagulation and yeast were used as pretreatment when needed. results showed that z08 directly degraded soybean wastewater under natural conditions without extra light or oxygen supply. after 72 h, cod reduced by 95.7%, macromolecules decrea ... | 2010 | 20483591 |
| elucidating mtbe degradation in a mixed consortium using a multidisciplinary approach. | the structure and function of a microbial community capable of biodegrading methyl-tert-butyl ether (mtbe) was characterized using compound-specific stable isotope analysis (csia), clone libraries and stable isotope probing of proteins (protein-sip). the enrichment culture (us3-m), which originated from a gasoline-impacted site in the united states, has been enriched on mtbe as the sole carbon source. the slope of isotopic enrichment factors (epsilon(c) of -2.29+/-0.03 per thousand; epsilon(h) o ... | 2010 | 20491917 |
| in vivo effects on photosynthesis gene expression of base pair exchanges in the gene encoding the light-responsive bluf domain of appa in rhodobacter sphaeroides. | the rhodobacter sphaeroides protein appa has the unique quality of sensing and transmitting light and redox signals. by acting as antirepressor to the ppsr protein, it acts as a major regulator in photosynthesis gene expression. in this study, we show that by introducing amino acid exchanges into the appa protein, the in vivo activity as an antirepressor can be greatly altered. the tryptophan 104 to phenylalanine (w104f) base exchange greatly diminished blue-light sensitivity of the bluf domain. ... | 2010 | 20497366 |
| a structural model for across membrane coupling between the qo and qi active sites of cytochrome bc1. | the two spatially distant quinone-binding sites of the ubihydroquinone: cytochrome c oxidoreductase (cyt bc(1)) complex have been shown to influence one another in some fashion. this transmembrane communication alters cofactor and redox partner binding interactions and could potentially influence the timing or 'concerted' steps involved in the steady-state turnover of the homodimeric enzymes. yet, despite several lines of evidence corroborating the coupling of the quinone binding active sites to ... | 2010 | 20513347 |
| cultivation-dependent and -independent characterization of microbial community producing polyhydroxyalkanoates from raw-glycerol. | high substrate costs decrease the profitability of polyhydroxyalkanoates (phas) production, and thus low-cost carbon substrates coming from agricultural and industrial residuals are tested for the production of these biopolymers. among them crude glycerol, formed as a byproduct during biodiesel production, seems to be the most promising source of carbon. the object of this study was to characterize the mixed population responsible for the conversion of crude glycerol into phas by the cultivation ... | 2010 | 20519907 |
| mutagenic analysis of cox11 of rhodobacter sphaeroides: insights into the assembly of cu(b) of cytochrome c oxidase. | the cu(i) chaperone cox11 is required for the insertion of cu(b) into cytochrome c oxidase (cco) of mitochondria and many bacteria, including rhodobacter sphaeroides. exploration of the copper binding stoichiometry of r. sphaeroides cox11 led to the finding that an apparent tetramer of both mitochondrial and bacterial cox11 binds more copper than the sum of the dimers, providing another example of the flexibility of copper binding by cu(i)-s clusters. site-directed mutagenesis has been used to i ... | 2010 | 20524628 |
| specificity of localization and phosphotransfer in the chea proteins of rhodobacter sphaeroides. | specificity of protein-protein interactions plays a vital role in signal transduction. the chemosensory pathway of rhodobacter sphaeroides comprises multiple homologues of chemotaxis proteins characterized in organisms such as escherichia coli. three chea homologues are essential for chemotaxis in r. sphaeroides under laboratory conditions. these cheas are differentially localized to two chemosensory clusters, one at the cell pole and one in the cytoplasm. the polar chea, chea(2), has the same d ... | 2010 | 20525091 |
| redesign, reconstruction, and directed extension of the brevibacterium linens c40 carotenoid pathway in escherichia coli. | in this study, the carotenoid biosynthetic pathways of brevibacterium linens dsmz 20426 were reconstructed, redesigned, and extended with additional carotenoid-modifying enzymes of other sources in a heterologous host escherichia coli. the modular lycopene pathway synthesized an unexpected carotenoid structure, 3,4-didehydrolycopene, as well as lycopene. extension of the novel 3,4-didehydrolycopene pathway with the mutant pantoea lycopene cyclase crty(2) and the rhodobacter spheroidene monooxyge ... | 2010 | 20525861 |
| chipd: a web tool to design oligonucleotide probes for high-density tiling arrays. | chipd is a web server that facilitates design of dna oligonucleotide probes for high-density tiling arrays, which can be used in a number of genomic applications such as chip-chip or gene-expression profiling. the server implements a probe selection algorithm that takes as an input, in addition to the target sequences, a set of parameters that allow probe design to be tailored to specific applications, protocols or the array manufacturer's requirements. the algorithm optimizes probes to meet thr ... | 2010 | 20529880 |
| nitrogen and molybdenum control of nitrogen fixation in the phototrophic bacterium rhodobacter capsulatus. | the vast majority of the purple nonsulfur photosynthetic bacteria are diazotrophs, but the details of the complex regulation of the nitrogen fixation process are well understood only for a few species. here we review what is known of the well-studied rhodobacter capsulatus, which contains two different nitrogenases, a standard mo-nitrogenase and an alternative fe-nitrogenase, and which has overlapping transcriptional control mechanisms with regard to the presence of fixed nitrogen, oxygen, and m ... | 2010 | 20532735 |
| proteomic analysis of the developing intracytoplasmic membrane in rhodobacter sphaeroides during adaptation to low light intensity. | although the primary photochemical events in the facultative photoheterotrophic purple bacterium rhodobacter sphaeroides are now well understood, comparatively little is known about how their photosynthetic apparatus is assembled. here we present a proteomic analysis of the intracytoplasmic membrane (icm) assembly process during adaptation to lowered light intensity, in which the size of the photosynthetic units is greatly expanded by addition of the light-harvesting 2 (lh2) peripheral antenna c ... | 2010 | 20532741 |
| a glimpse into the proteome of phototrophic bacterium rhodobacter capsulatus. | a first glimpse into the proteome of rhodobacter capsulatus revealed more than 450 (with over 210 cytoplasmic and 185 extracytoplasmic known as well as 55 unknown) proteins that are identified with high degree of confidence using nlc-ms/ms analyses. the accumulated data provide a solid platform for ongoing efforts to establish the proteome of this species and the cellular locations of its constituents. they also indicate that at least 40 of the identified proteins, which were annotated in genome ... | 2010 | 20532742 |
| the tetrapyrrole biosynthetic pathway and its regulation in rhodobacter capsulatus. | the purple anoxygenic photosynthetic bacterium rhodobacter capsulatus is capable of growing in aerobic or anaerobic conditions, in the dark or using light, etc. achieving versatile metabolic adaptations from respiration to photosynthesis requires the use of tetrapyrroles such as heme and bacteriochlorophyll, in order to carry oxygen, to transfer electrons, and to harvest light energy. a third tetrapyrrole, cobalamin (vitamin b(12)), is synthesized and used as a cofactor for many enzymes. heme, b ... | 2010 | 20532744 |
| the gene transfer agent of rhodobacter capsulatus. | when rhodobacter capsulatus cultures enter the stationary phase of growth, particles of the gene transfer agent (rcgta) are released from cells. the morphology of rcgta resembles that of a small, tailed bacteriophage, with a protein capsid surrounding a ~4 kb linear, double-stranded fragment of dna. however, the dna present consists of random segments of the r. capsulatus genome, which may be transferred to another strain of r. capsulatus. the recipient in rcgta-mediated gene transduction may ac ... | 2010 | 20532745 |
| integrative control of carbon, nitrogen, hydrogen, and sulfur metabolism: the central role of the calvin-benson-bassham cycle. | nonsulfur purple (nsp) photosynthetic bacteria use the calvin-benson-bassham (cbb) reductive pentose phosphate pathway for the reduction of co(2) via ribulose 1,5-bisphosphate (rubp) carboxylase-oxygenase (rubisco), as a means to build cell mass during chemoautotrophic or photoautotrophic conditions. in addition, the cbb pathway plays an important role in maintaining redox balance during photoheterotrophic growth conditions. in this communication we describe protein-protein interactions between ... | 2010 | 20532746 |
| three-dimensional structure of tspo by electron cryomicroscopy of helical crystals. | the 18 kda tspo protein is a polytopic mitochondrial outer membrane protein involved in a wide range of physiological functions and pathologies, including neurodegeneration and cancer. the pharmacology of tspo has been extensively studied, but little is known about its biochemistry, oligomeric state, and structure. we have expressed, purified, and characterized a homologous protein, tspo from rhodobacter sphaeroides, and reconstituted it as helical crystals. using electron cryomicroscopy and sin ... | 2010 | 20541505 |
| effects of ethanol, formaldehyde, and gentle heat fixation in confocal resonance raman microscopy of purple nonsulfur bacteria. | resonance raman microscopy is well suited to examine living bacterial samples without further preparation. therefore, comparatively little thought has been given to its compatibility with common fixation methods. however, fixation of cell samples is a very important tool in the microbiological sciences, allowing the preservation of samples in a specific condition for further examination, future measurements, transport, or later reference. we examined the effects of three common fixatives-ethanol ... | 2011 | 20544803 |
| functional replacement of yeast flavocytochrome b(2) with bacterial l-lactate dehydrogenase. | using yeast genetic complementation, we show here that rhodobacter sphaeroidesl-lactate dehydrogenase can functionally replace flavocytochrome b(2) in saccharomyces cerevisiae, only when a matrix-targeting signal of flavocytochrome b(2) is fused with the bacterial enzyme. the recombinant l-lactate dehydrogenase may add alternative route of mitochondrial electron transport other than flavocytochrome b(2). | 2010 | 20547335 |
| [isolation and characterization of pigment-protein complexes from rhodobacter azotoformans]. | in order to reveal the relationships of compositions and content of pigment in pigment-protein complexes (ppc) and hydrogen photoevolution from anoxygenic phototrophic bacteria. | 2010 | 20560353 |
| absorbance changes accompanying the fast fluorescence induction in the purple bacterium rhodobacter sphaeroides. | the authors present a study of the fluorescence and absorbance transients occurring in whole cells of purple nonsulfur bacterium rhodobacter sphaeroides on the millisecond timescale under pulsed actinic illumination. the fluorescence induction curve is interpreted in terms of combination of effects of redox changes in the reaction center and the membrane potential. the results of this study support the view that the membrane potential act predominantly to increase the fluorescence yield. advanta ... | 2010 | 20574750 |
| occurrence and sequence of sphaeroides heme protein and diheme cytochrome c in purple photosynthetic bacteria in the family rhodobacteraceae. | sphaeroides heme protein (shp) was discovered in the purple photosynthetic bacterium, rhodobacter sphaeroides, and is the only known c-type heme protein that binds oxygen. although initially not believed to be widespread among the photosynthetic bacteria, the gene has now been found in more than 40 species of proteobacteria and generally appears to be regulated. rb. sphaeroides is exceptional in not having regulatory genes associated with the operon. we have thus analyzed additional purple bacte ... | 2010 | 20587053 |
| similarity of cytochrome c oxidases in different organisms. | most of biological oxygen reduction is catalyzed by the heme-copper oxygen reductases. these enzymes are redox-driven proton pumps that take part in generating the proton gradient in both prokaryotes and mitochondria that drives synthesis of atp. the enzymes have been divided into three evolutionarily-related groups: the a-, b-, and c-families. recent comparative studies suggest that all oxygen reductases perform the same chemistry for oxygen reduction and comprise the same essential elements of ... | 2010 | 20589635 |
| mechanisms of oxygen inhibition of nirk expression in rhodobacter sphaeroides. | r. sphaeroides strain 2.4.3, when lacking the cbb(3) oxidase, is unable to transition from aerobic respiration to denitrification using cellular respiration as a means of reducing oxygen levels. this is due to an inability to express nirk, the gene encoding nitrite reductase. under certain photosynthetic conditions this strain can transition from aerobic to nitrate respiration, demonstrating that nirk expression can occur in the absence of a functional cbb(3) oxidase. if oxygen levels are reduce ... | 2010 | 20595263 |
| biological synthesis of size-controlled cadmium sulfide nanoparticles using immobilized rhodobacter sphaeroides. | size-controlled cadmium sulfide nanoparticles were successfully synthesized by immobilized rhodobacter sphaeroides in the study. the dynamic process that cd(2+) was transported from solution into cell by living r. sphaeroides was characterized by transmission electron microscopy (tem). culture time, as an important physiological parameter for r. sphaeroides growth, could significantly control the size of cadmium sulfide nanoparticles. tem demonstrated that the average sizes of spherical cadmium ... | 2009 | 20596372 |
| high-resolution x-ray observation of unstained samples by a newly developed sgxm. | analytical methods with nanometre-scale resolution are indispensable in various scientific fields, including biology, chemistry and nanotechnology. one suitable tool, the soft x-ray microscope, provides high spatial resolution of unstained specimens. recently, we developed an x-ray microscope called a scanning electron generation x-ray microscope (sgxm). this system had attached additional x-ray detection equipment to the scanning electron microscope (sem). here, we describe a new sample stage c ... | 2010 | 20601766 |
| coupling of collective motions of the protein matrix to vibrations of the non-heme iron in bacterial photosynthetic reaction centers. | non-heme iron is a conservative component of type ii photosynthetic reaction centers of unknown function. we found that in the reaction center from rba. sphaeroides it exists in two forms, high and low spin ferrous states, whereas in rsp. rubrum mostly in a low spin state, in line with our earlier finding of its low spin state in the algal photosystem ii reaction center (burda et al., 2003). the temperature dependence of the non-heme iron displacement studied by mössbauer spectroscopy shows that ... | 2010 | 20603098 |
| the measured and calculated affinity of methyl- and methoxy-substituted benzoquinones for the q(a) site of bacterial reaction centers. | quinones play important roles in mitochondrial and photosynthetic energy conversion acting as intramembrane, mobile electron, and proton carriers between catalytic sites in various electron transfer proteins. they display different affinity, selectivity, functionality, and exchange dynamics in different binding sites. the computational analysis of quinone binding sheds light on the requirements for quinone affinity and specificity. the affinities of 10 oxidized, neutral benzoquinones were measur ... | 2010 | 20607696 |
| femtosecond stage of electron transfer in reaction centers of the triple mutant sl178k/gm203d/lm214h of rhodobacter sphaeroides. | coherent processes in an initial phase of charge transfer in reaction centers (rcs) of the triple mutant s(l178)k/g(m203)d/l(m214)h of rhodobacter sphaeroides were investigated by difference (light - dark) absorption spectroscopy with 18 fsec time resolution. electron transfer in the b cofactor branch is activated in this mutant, while the a-branch electron transfer is slowed in comparison with native rcs of rba. sphaeroides. a bulk of absorption difference spectra was analyzed in the 940-1060 n ... | 2010 | 20618129 |
| a powerful hybrid puc operon promoter tightly regulated by both iptg and low oxygen level. | rhodobacter sphaeroides has been intensively studied and provides an excellent model for studying both photosynthesis and membrane development. the photosynthetic apparatus (lh2 and lh1-rc complexes) can be synthesized in large scale and integrated into the intracytoplasmic membrane system under specific conditions, which thus provides us insight to utilize the puc or(and) puf operon to heterologously express recombinant proteins in the intracytoplasmic membrane using rb. sphaeroides as a novel ... | 2010 | 20618143 |
| discrimination between two possible reaction sequences that create potential risk of generation of deleterious radicals by cytochrome bc₁. implications for the mechanism of superoxide production. | in addition to its bioenergetic function of building up proton motive force, cytochrome bc₁ can be a source of superoxide. one-electron reduction of oxygen is believed to occur from semiquinone (sq(o)) formed at the quinone oxidation/reduction q(o) site (q(o)) as a result of single-electron oxidation of quinol by the iron-sulfur cluster (fes) (semiforward mechanism) or single-electron reduction of quinone by heme b(l) (semireverse mechanism). it is hotly debated which mechanism plays a major rol ... | 2010 | 20637719 |
| dimerisation of the rhodobacter sphaeroides rc-lh1 photosynthetic complex is not facilitated by a gxxxg motif in the pufx polypeptide. | in purple photosynthetic bacteria the initial steps of light energy transduction take place in an rc-lh1 complex formed by the photochemical reaction centre (rc) and the lh1 light harvesting pigment-protein. in rhodobacter sphaeroides, the rc-lh1 complex assembles in a dimeric form in which two rcs are surrounded by an s-shaped lh1 antenna. there is currently debate over the detailed architecture of this dimeric rc-lh1 complex, with particular emphasis on the location and precise function of a m ... | 2010 | 20646993 |
| activated q-cycle as a common mechanism for cytochrome bc1 and cytochrome b6f complexes. | cytochrome bc(1)-complexes of animals and bacteria (hereafter bc(1)), as well as related cytochrome b(6)f complexes of plants and cyanobacteria (hereafter bf) are dimeric quinol:cytochrome c/plastocyanin oxidoreductases capable of translocating protons across energy-converting membranes. the commonly accepted q-cycle mechanism suggests that these enzymes oxidize two quinol molecules in their catalytic centers p to yield one quinol molecule in another catalytic center n. earlier, based upon data ... | 2010 | 20650262 |
| an electronic bus bar lies in the core of cytochrome bc1. | the ubiquinol-cytochrome c oxidoreductases, central to cellular respiration and photosynthesis, are homodimers. high symmetry has frustrated resolution of whether cross-dimer interactions are functionally important. this has resulted in a proliferation of contradictory models. here, we duplicated and fused cytochrome b subunits, and then broke symmetry by introducing independent mutations into each monomer. electrons moved freely within and between monomers, crossing an electron-transfer bridge ... | 2010 | 20651150 |
| excitation transfer connectivity in different purple bacteria: a theoretical and experimental study. | photosynthetic membranes accommodate densely packed light-harvesting complexes which absorb light and convey excitation to the reaction center (rc). the relationship between the fluorescence yield (phi) and the fraction (x) of closed rcs is informative about the probability for an excitation reaching a closed rc to be redirected to another rc. in this work, we have examined in this respect membranes from various bacteria and searched for a correlation with the arrangement of the light-harvesting ... | 2010 | 20655292 |
| photosynthetic vesicle architecture and constraints on efficient energy harvesting. | photosynthetic chromatophore vesicles found in some purple bacteria constitute one of the simplest light-harvesting systems in nature. the overall architecture of chromatophore vesicles and the structural integration of vesicle function remain poorly understood despite structural information being available on individual constituent proteins. an all-atom structural model for an entire chromatophore vesicle is presented, which improves upon earlier models by taking into account the stoichiometry ... | 2010 | 20655834 |
| proton motive force in rhodobacter sphaeroides under anaerobic conditions in the dark. | in order to examine the mediatory role of proton motive force (∆p) or proton atpase in h₂ production by rhodobacter sphaeroides, ∆p was determined under anaerobic conditions in the dark, and the atpase activity has been studied in r. sphaeroides strain a-10, isolated from arzni mineral springs in armenia. membrane potential (∆φ) was measured from the distribution of tetraphenylphosphonium cation; ph gradient (∆ph) was the difference between the external and cytoplasmic ph values, and the latter ... | 2011 | 20658137 |
| reconstruction of the core and extended regulons of global transcription factors. | the processes underlying the evolution of regulatory networks are unclear. to address this question, we used a comparative genomics approach that takes advantage of the large number of sequenced bacterial genomes to predict conserved and variable members of transcriptional regulatory networks across phylogenetically related organisms. specifically, we developed a computational method to predict the conserved regulons of transcription factors across alpha-proteobacteria. we focused on the crp/fnr ... | 2010 | 20661434 |
| early detection of mercury contamination by fluorescence induction of photosynthetic bacteria. | the induction (sudden dark-to-light transition) of fluorescence of photosynthetic bacteria has proved to be sensitive tool for early detection of mercury (hg(2+)) contamination of the culture medium. the major characteristics of the induction (dark, variable and maximum fluorescence levels together with rise time) offer an easier, faster and more informative assay of indication of the contamination than the conventional techniques. the inhibition of hg(2+) is stronger in the light than in the da ... | 2010 | 20664861 |