Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| exploring recombinant flavonoid biosynthesis in metabolically engineered escherichia coli. | flavonoids are important plant-specific secondary metabolites synthesized from 4-coumaroyl coenzyme a (coa), derived from the general phenylpropanoid pathway, and three malonyl-coas. the synthesis involves a plant type iii polyketide synthase, chalcone synthase. we report the cloning and coexpression in escherichia coli of phenylalanine ammonia lyase, cinnamate-4-hydroxylase, 4-coumarate:coa ligase, and chalcone synthase from the model plant arabidopsis thaliana. simultaneous expression of all f ... | 2004 | 15185374 |
| regb/rega, a highly conserved redox-responding global two-component regulatory system. | the reg regulon from rhodobacter capsulatus and rhodobacter sphaeroides encodes proteins involved in numerous energy-generating and energy-utilizing processes such as photosynthesis, carbon fixation, nitrogen fixation, hydrogen utilization, aerobic and anaerobic respiration, denitrification, electron transport, and aerotaxis. the redox signal that is detected by the membrane-bound sensor kinase, regb, appears to originate from the aerobic respiratory chain, given that mutations in cytochrome c o ... | 2004 | 15187184 |
| the proton-driven rotor of atp synthase: ohmic conductance (10 fs), and absence of voltage gating. | the membrane portion of f(0)f(1)-atp synthase, f(0), translocates protons by a rotary mechanism. proton conduction by f(0) was studied in chromatophores of the photosynthetic bacterium rhodobacter capsulatus. the discharge of a light-induced voltage jump was monitored by electrochromic absorption transients to yield the unitary conductance of f(0). the current-voltage relationship of f(0) was linear from 7 to 70 mv. the current was extremely proton-specific (>10(7)) and varied only slightly ( ap ... | 2004 | 15189903 |
| protein dynamics in the region of the sixth ligand methionine revealed by studies of imidazole binding to rhodobacter capsulatus cytochrome c2 hinge mutants. | all class i c-type cytochromes studied to date undergo a dynamic process in the oxidized state, which results in the transient breaking of the iron-methionine-sulfur bond and sufficient movement to allow the binding of exogenous ligands (imidazole in this work). in the case of rhodobacter capsulatus cytochrome c(2), the sixth heme ligand met96 and up to 14 flanking residues (positions 88-100, termed the hinge region), located between two relatively rigid helical regions, may be involved in struc ... | 2004 | 15196014 |
| reconstitution of the rhodobacter sphaeroides cbb3-prrba signal transduction pathway in vitro. | the prrba two-component system in rhodobacter sphaeroides 2.4.1, which is composed of the prrb histidine kinase and the prra response regulator, controls the expression of all of the photosynthesis genes, either directly or indirectly, in response to changes in oxygen tension. in vivo under aerobic conditions it is the cbb(3) cytochrome c oxidase which generates an inhibitory signal preventing the accumulation of activated prra. using purified cbb(3) cytochrome c oxidase, prrb, and prra, we demo ... | 2004 | 15196036 |
| variation of ser-l223 hydrogen bonding with the qb redox state in reaction centers from rhodobacter sphaeroides. | ser-l223 is close to ubiquinone (q(b)) in the b-branch of the bacterial photosynthetic reaction center (brc) from rhodobacter (rb) sphaeroides. therefore, the presence of a hydrogen bond (h bond) between the two was naturally proposed from the crystal structure. the hydrogen bonding pattern of q(b) from the light-exposed structure was studied by generating hydrogen atom coordinates based on the charmm force field. in the q(b) neutral charge state (q(b)(0)), no h bond was found between the oxygen ... | 2004 | 15212556 |
| expression and characteristics of the gene encoding azoreductase from rhodobacter sphaeroides as1.1737. | a gene that encodes a protein with azoreductase activity was obtained by pcr amplification from rhodobacter sphaeroides as1.1737. the enzyme, with a molecular weight of 18.7 kd, was heterologously expressed in escherichia coli and its azoreductase activity was characterized. furthermore, the reduction mechanism of azo dyes catalyzed by the azoreductase was studied in detail. the presence of a hydrazo-intermediate was identified, which provided a convincing evidence for the assumption that azo dy ... | 2004 | 15212802 |
| a novel arabidopsis thaliana protein is a functional peripheral-type benzodiazepine receptor. | a key element in the regulation of mammalian steroid biosynthesis is the 18 kda peripheral-type benzodiazepine receptor (pbr), which mediates mitochondrial cholesterol import. pbr also possess an affinity to the tetrapyrrole metabolite protoporphyrin. the bacterial homolog to the mammalian pbr, the rhodobacter tspo (crtk) protein, was shown to be involved in the bacterial tetrapyrrole metabolism. looking for a similar mitochondrial import mechanism in plants, protein sequences from arabidopsis a ... | 2004 | 15215507 |
| construction and validation of the rhodobacter sphaeroides 2.4.1 dna microarray: transcriptome flexibility at diverse growth modes. | a high-density oligonucleotide dna microarray, a genechip, representing the 4.6-mb genome of the facultative phototrophic proteobacterium, rhodobacter sphaeroides 2.4.1, was custom-designed and manufactured by affymetrix, santa clara, calif. the genechip contains probe sets for 4,292 open reading frames (orfs), 47 rrna and trna genes, and 394 intergenic regions. the probe set sequences were derived from the genome annotation generated by oak ridge national laboratory after extensive revision, wh ... | 2004 | 15231807 |
| temperature and cryoprotectant influence secondary quinone binding position in bacterial reaction centers. | we have determined the first de novo position of the secondary quinone qb in the rhodobacter sphaeroides reaction center (rc) using phases derived by the single wavelength anomalous dispersion method from crystals with selenomethionine substitution. we found that in frozen rc crystals, qb occupies primarily the proximal binding site. in contrast, our room temperature structure showed that qb is largely in the distal position. both data sets were collected in dark-adapted conditions. we estimate ... | 2004 | 15251460 |
| functional activity of human monocytes exposed to lipopolysaccharides of different structure. | 2004 | 15255137 | |
| the nitrogen-fixing gene (nifh) of rhodopseudomonas palustris: a case of lateral gene transfer? | nitrogen fixation is catalysed by some photosynthetic bacteria. this paper presents a phylogenetic comparison of a nitrogen fixation gene (nifh) with the aim of elucidating the processes underlying the evolutionary history of rhodopseudomonas palustris. in the nifh phylogeny, strains of rps. palustris were placed in close association with rhodobacter spp. and other phototrophic purple non-sulfur bacteria belonging to the alpha-proteobacteria, separated from its close relatives bradyrhizobium jap ... | 2004 | 15256566 |
| atr-ftir spectroscopy studies of iron-sulfur protein and cytochrome c1 in the rhodobacter capsulatus cytochrome bc1 complex. | redox transitions in the rhodobacter capsulatus cytochrome bc(1) complex were investigated by perfusion-induced attenuated total reflection-fourier transform infrared (atr-ftir) spectroscopy combined with synchronous visible spectroscopy, in both the wild type and a cytochrome c(1) point mutant, m183k, in which the midpoint potential of heme was lowered from the wild-type value of 320 mv to 60 mv. overall redox difference spectra of the wild type and m183k mutant were essentially identical, indi ... | 2004 | 15260490 |
| metal ion modulated electron transfer in photosynthetic proteins. | photosynthetic purple bacterial reaction center (rc) proteins are ideal native systems for addressing basic questions regarding the nature of biological electron transfer because both the protein structure and the electron-transfer reactions are well-characterized. metal ion binding to the rc can affect primary photochemistry and provides a probe for understanding the involvement of local protein environments in electron transfer. the rc has two distinct transition metal ion binding sites, the w ... | 2004 | 15260506 |
| biochemical study of multiple chey response regulators of the chemotactic pathway of rhodobacter sphaeroides. | the six copies of the response regulator chey from rhodobacter sphaeroides bind to the switch protein flim. phosphorylation by acetyl phosphate (acp) was detected by tryptophan fluorescence quenching in three of the four cheys that contain this residue. autophosphorylation with ac(32)p was observed in five chey proteins. we also show that all of the chey genes are expressed simultaneously; therefore, in vivo all of the chey proteins could bind to flim to control the chemotactic response. consequ ... | 2004 | 15262956 |
| composition and activity of the rhodobacter capsulatus degradosome vary under different oxygen concentrations. | the influence of changes in temperature or oxygen tension during growth of rhodobacter capsulatus on the composition and activity of the degradosome, an rna-processing protein complex, was investigated. only minor differences in the amount of specific proteins of the complex were observed after a decrease or increase of the temperature, but dramatic variations were detectable during growth at different oxygen concentrations. in particular, the amount of the transcription factor rho, which was pr ... | 2004 | 15263819 |
| towards higher-throughput membrane protein production for structural genomics initiatives. | integral membrane proteins present unparalleled challenges for structural genomics programs. samples from this class of proteins are not only difficult to produce in quantities sufficient for analysis by x-ray diffraction or nmr, but their hydrophobic properties add extra dimension to their purification and subsequent crystallization. new systems that seek to tackle the production problems are in development. in our laboratory, one such strategy exploits the unique physiology of the rhodobacter ... | 2004 | 15263855 |
| "cystope tagging" for labeling and detection of recombinant protein expression. | a labeling and detection method, based on the addition of a single cysteine residue at the c terminus of a recombinant protein and the subsequent sulfhydryl-specific michael addition to the double bond of maleimide and its derivatives, was developed. the method was named "cystope tagging." sorbit dehydrogenase (sdh) from rhodobacter sphaeroides, a member of the short-chain dehydrogenase family of proteins that contains three inherent cysteines, was used as a model recombinant protein. by labelin ... | 2004 | 15265732 |
| the role of active site glutamate residues in catalysis of rhodobacter capsulatus xanthine dehydrogenase. | xanthine dehydrogenase (xdh) from the bacterium rhodobacter capsulatus catalyzes the hydroxylation of xanthine to uric acid with nad+ as the electron acceptor. r. capsulatus xdh forms an (alphabeta)2 heterotetramer and is highly homologous to homodimeric eukaryotic xanthine oxidoreductases. here we first describe reductive titration and steady state kinetics on recombinant wild-type r. capsulatus xdh purified from escherichia coli, and we then proceed to evaluate the catalytic importance of the ... | 2004 | 15265866 |
| exciton exciton annihilation dynamics in chromophore complexes. ii. intensity dependent transient absorption of the lh2 antenna system. | using the multiexciton density matrix theory of excitation energy transfer in chromophore complexes developed in a foregoing paper [j. chem. phys. 118, 746 (2003)], the computation of ultrafast transient absorption spectra is presented. beside static disorder and standard mechanisms of excitation energy dissipation the theory incorporates exciton exciton annihilation (eea) processes. to elucidate signatures of eea in intensity dependent transient absorption data the approach is applied to the b8 ... | 2004 | 15268371 |
| interactions between the rhodobacter sphaeroides ecf sigma factor, sigma(e), and its anti-sigma factor, chrr. | rhodobacter sphaeroides sigma(e) is a member of the extra cytoplasmic function sigma factor (ecf) family, whose members have been shown to regulate gene expression in response to a variety of signals. the functions of ecf family members are commonly regulated by a specific, reversible interaction with a cognate anti-sigma factor. in r.sphaeroides, sigma(e) activity is inhibited by chrr, a member of a newly discovered family of zinc containing anti-sigma factors. we used gel filtration chromatogr ... | 2004 | 15276828 |
| loktanella salsilacus gen. nov., sp. nov., loktanella fryxellensis sp. nov. and loktanella vestfoldensis sp. nov., new members of the rhodobacter group, isolated from microbial mats in antarctic lakes. | a taxonomic study was performed on 26 strains isolated from microbial mats in antarctic lakes of the vestfold hills and the mcmurdo dry valleys. phylogenetic analysis based on 16s rrna gene sequences placed these strains within the rhodobacter group of the alpha-subclass of the proteobacteria. sequence similarity values for the strains with their nearest phylogenetic neighbours (jannaschia, octadecabacter and ketogulonicigenium) ranged between 94.0 and 95.8%. dna-dna hybridizations and compariso ... | 2004 | 15280301 |
| probing light-induced conformational transitions in bacterial photosynthetic reaction centers embedded in trehalose-water amorphous matrices. | the coupling between electron transfer and protein dynamics has been studied in photosynthetic reaction centers (rc) from rhodobacter sphaeroides by embedding the protein into room temperature solid trehalose-water matrices. electron transfer kinetics from the primary quinone acceptor (q(a)(-)) to the photoxidized donor (p(+)) were measured as a function of the duration of photoexcitation from 20 ns (laser flash) to more than 1 min. decreasing the water content of the matrix down to approximatel ... | 2004 | 15282174 |
| resonance raman detection of the fe2+-c-n modes in heme-copper oxidases: a probe of the active site. | resonance raman spectroscopy has been employed to investigate the reduced cyano complexes of cytochrome aa(3) from bovine heart and rhodobacter sphaeroides and of cytochrome bo(3) from e. coli. in the aa(3)-type oxidases, the frequency of the fe-cn stretching mode is located at 468 cm(-1), and the bending fe-c-n vibration, at 500 cm(-1). the fully reduced cytochrome bo(3)-cn complex gives rise to a stretching vibration at 468 cm(-1), a bending vibration at 491 cm(-1), and a stretching c-n vibrat ... | 2004 | 15285666 |
| a single-amino-acid lid renders a gas-tight compartment within a membrane-bound transporter. | proteins undergo structural fluctuations between nearly isoenergetic substates. such fluctuations are often intimately linked with the functional properties of proteins. however, in some cases, such as in transmembrane ion transporters, the control of the ion transport requires that the protein is designed to restrict the motions in specific regions. in this study, we have investigated the dynamics of a membrane-bound respiratory oxidase, which acts both as an enzyme catalyzing reduction of o(2) ... | 2004 | 15289603 |
| a eukaryotic bluf domain mediates light-dependent gene expression in the purple bacterium rhodobacter sphaeroides 2.4.1. | the flavin-binding bluf domain functions as a blue-light receptor in eukaryotes and bacteria. in the photoreceptor protein photo-activated adenylyl cyclase (pac) from the flagellate euglena gracilis, the bluf domain is linked to an adenylyl cyclase domain. the pac protein mediates a photophobic response. in the appa protein of rhodobacter sphaeroides, the bluf domain is linked to a downstream domain without similarity to known proteins. appa functions as a transcriptional antirepressor, controll ... | 2004 | 15292515 |
| stereoselective oxidation of aliphatic diols and reduction of hydroxy-ketones with galactitol dehydrogenase from rhodobacter sphaeroides d. | from the rhodobacter sphaeroides mutant d a galactitol dehydrogenase (gdh) was isolated and characterized in an earlier investigation (1). the enzyme expressed activity with a wide spread substrate spectrum, like sugars, sugar alcohols, secondary alcohols or the corresponding ketones and it can be used for the production of the rare sugar l-tagatose by regioselective oxidation of galactitol (2). this study focuses on the preparation of optically pure aliphatic diols by oxidation of one enantiome ... | 2003 | 15296184 |
| active site geometry and substrate recognition of the molybdenum hydroxylase quinoline 2-oxidoreductase. | the soil bacterium pseudomonas putida 86 uses quinoline as a sole source of carbon and energy. quinoline 2-oxidoreductase (qor) catalyzes the first metabolic step converting quinoline to 2-oxo-1,2-dihydroquinoline. qor is a member of the molybdenum hydroxylases. the molybdenum ion is coordinated by two ene-dithiolate sulfur atoms, two oxo-ligands, and a catalytically crucial sulfido-ligand, whose position in the active site was controversial. the 1.8 a resolution crystal structure of qor indicat ... | 2004 | 15296736 |
| structure of the photochemical reaction centre of a spheroidene-containing purple-bacterium, rhodobacter sphaeroides y, at 3 a resolution. | the crystal structure of the photochemical reaction centre from rhodobacter sphaeroides y, a carotenoid-containing wild-type purple bacterium, has been determined at 3 a resolution. this membrane complex consists of three subunits (281, 307 and 260 residues, respectively) and ten cofactors. it was crystallized in presence of beta-d-octylglucoside. the crystals are orthorhombic with unit-cell dimensions, a = 143.7, b = 139.8, c = 78.7 a, space group p2(1)2(1)2(1) with four molecules in the unit c ... | 1995 | 15299304 |
| crystallization and x-ray structure determination of cytochrome c2 from rhodobacter sphaeroides in three crystal forms. | cytochrome c(2) serves as the secondary electron donor that reduces the photo-oxidized bacteriochlorophyll dimer in photosynthetic bacteria. cytochrome c(2) from rhodobacter sphaeroides has been crystallized in three different forms. at high ionic strength, crystals of a hexagonal space group (p6(1)22) were obtained, while at low ionic strength, triclinic (p1) and tetragonal (p4(1)2(1)2) crystals were formed. the three-dimensional structures of the cytochrome in all three crystal forms have been ... | 1994 | 15299423 |
| phase diagram determination to elucidate the crystal growth of the photoreaction center from rhodobacter sphaeroides. | solubility curves (a phase diagram) of an amorphous precipitate and the orthorhombic crystals of a membrane protein, the photoreaction center from rhodobacter sphaeroides, were determined. with the phase diagram, the process of crystal growth of the membrane protein was elucidated within a general physicochemical framework, and justification was provided of hitherto empirically selected crystallization conditions. | 1994 | 15299429 |
| preliminary crystallographic studies of dimethylsulfoxide reductase from rhodobacter capsulatus. | dimethylsulfoxide reductase from the photosynthetic bacterium rhodobacter capsulatus has been crystallized in two similar forms which are suitable for x-ray structure determination. both crystals forms belong to space group p4(1)22 or p4(3)22, with cell dimensions a = b = 80.81, c = 229.75 a (type i crystals) or a = b = 89.30, c = 230.05 a (type ii crystals) and one molecule in the asymmetric unit. diffraction has been observed to at least 2.0 a in type i crystals and to 2.6 a in type ii crystal ... | 1996 | 15299743 |
| crystallization and preliminary x-ray study of a new crystal form of cytochrome c' from rhodobacter capsulatus. | a new crystal form of diheme cytochrome c' from rhodobacter capsulatus has been obtained and preliminary crystallographic experiments have been performed. the crystals belong to the space group p2(1)2(1)2 with unit-cell dimensions of a = 47.82, b = 72.59, c = 34.32 a. the assumption that an asymmetric unit of the crystal contains one half of the homodimer molecule indicates that the monomers in the dimeric molecule may be related by a crystallographic twofold axis. crystals diffract up to 1.7 a ... | 1996 | 15299745 |
| structure of cytochrome c' from rhodobacter capsulatus strain st louis: an unusual molecular association induced by bridging zn ions. | rhodobacter capsulatus strain st louis cytochrome c' (rccp-sl) has been crystallized and the structure solved by molecular replacement. it was refined at 2.1 a resolution to an r value of 18.4%, and compared with rhodobacter capsulatus strain m110 cytochrome c' (rccp-m110). although these two proteins are very similar in sequence and structure, the intermolecular interaction is largely different. in rccp-m110, the molecules dimerize through interaction of helix b to form an antiparallel arrangem ... | 1997 | 15299853 |
| light and redox control of photosynthesis gene expression in bradyrhizobium: dual roles of two ppsr. | the two closely related bacteria bradyrhizobium and rhodopseudomonas palustris show an unusual mechanism of regulation of photosystem formation by light thanks to a bacteriophytochrome that antirepresses the regulator ppsr. in these two bacteria, we found out, unexpectedly, that two ppsr genes are present. we show that the two bradyrhizobium ppsr proteins exert antagonistic effects in the regulation of photosystem formation with a classical repressor role for ppsr2 and an unexpected activator ro ... | 2004 | 15304477 |
| hydrogen production from propionate by rhodopseudomonas capsulata. | hydrogen production from propionate at various concentrations by rhodopseudomonas capsulata, a purple nonsulfur bacterium, was studied at a temperature of 31 degrees c, a ph of 7.0, and an illumination intensity of 3000 lux. among the six levels of propionate, 3.84 g/l was found to be the optimum propionate concentration for h2 production in terms of substrate utilization efficiency, h2 percentage, cumulative h2 production, and h2 yield. a modified gompertz equation was able to describe properly ... | 2004 | 15304766 |
| [an oligonucleotide primer system for amplification of the ribulose-1,5-bisphosphate carboxylase/oxygenase genes of bacteria of various taxonomic groups]. | based on the analysis of genbank nucleotide sequences of the cbbl and cbbm genes, coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubpc), the key enzyme of the calvin cycle, a primer system was designed that allows about 800-bp-long fragments of these genes to be pcr-ampliflied in various photo- and chemotrophic bacteria. the efficiency of the designed primer system in detection of rubpc genes was demonstrated in pcr with dna of taxonomically diverse bacteria pos ... | 2004 | 15315232 |
| the reaction center h subunit is not required for high levels of light-harvesting complex 1 in rhodospirillum rubrum mutants. | the gene (puha) encoding the h subunit of the reaction center (rc) was deleted by site-directed interposon mutagenesis by using a kanamycin resistance cassette lacking transcriptional terminators to eliminate polar effects in both the wild-type strain rhodospirillum rubrum s1 and the carotenoid-less strain r. rubrum g9. the puha interposon mutants were incapable of photoheterotrophic growth but grew normally under aerobic chemoheterotrophic conditions. absorption spectroscopy and sodium dodecyl ... | 2004 | 15317762 |
| molecular and functional characterization of the azorhizobium caulinodans ors571 hydrogenase gene cluster. | in this work, we report the cloning and sequencing of the azorhizobium caulinodans ors571 hydrogenase gene cluster. sequence analysis revealed the presence of 20 open reading frames huptuvhypfhupslcdfghjk hypabhuprhypcdehupe. the physical and genetic organization of a. caulinodans ors571 hydrogenase system suggests a close relatedness to that of rhodobacter capsulatus. in contrast to the latter species, a gene homologous to rhizobium leguminosarum hupe was identified downstream of the hyp operon ... | 2004 | 15321689 |
| hydroxylamine assimilation by rhodobacter capsulatus e1f1. requirement of the hcp gene (hybrid cluster protein) located in the nitrate assimilation nas gene region for hydroxylamine reduction. | rhodobacter capsulatus e1f1 grows phototrophically with nitrate as nitrogen source. using primers designed for conserved motifs in bacterial assimilatory nitrate reductases, a 450-bp dna was amplified by pcr and used for the screening of a genomic library. a cosmid carrying an insert with four sali fragments of 2.8, 4.1, 4.5, and 5.8 kb was isolated, and dna sequencing revealed that it contains a nitrate assimilation (nas) gene region, including the hcp gene coding for a hybrid cluster protein ( ... | 2004 | 15322098 |
| physiological ligands adp and pi modulate the degree of intrinsic coupling in the atp synthase of the photosynthetic bacterium rhodobacter capsulatus. | the proton-pumping and the atp hydrolysis activities of the atp synthase of rhodobacter capsulatus have been compared as a function of the adp and p(i) concentrations. the proton pumping was measured either with the transmembrane ph difference probe, 9-amino-6-chloro-2-methoxyacridine, or with the transmembrane electric potential difference probe, bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol, obtaining consistent results. the comparison indicates that an intrinsic uncoupling of atp syntha ... | 2004 | 15323572 |
| thioredoxin can influence gene expression by affecting gyrase activity. | the expression of many genes of facultatively photosynthetic bacteria of the genus rhodobacter is controlled by the oxygen tension. among these are the genes of the puf and puc operons, which encode proteins of the photosynthetic apparatus. previous results revealed that thioredoxins are involved in the regulated expression of these operons, but it remained unsolved as to the mechanisms by which thioredoxins affect puf and puc expression. here we show that reduced trxa of rhodobacter capsulatus ... | 2004 | 15328368 |
| the native architecture of a photosynthetic membrane. | in photosynthesis, the harvesting of solar energy and its subsequent conversion into a stable charge separation are dependent upon an interconnected macromolecular network of membrane-associated chlorophyll-protein complexes. although the detailed structure of each complex has been determined, the size and organization of this network are unknown. here we show the use of atomic force microscopy to directly reveal a native bacterial photosynthetic membrane. this first view of any multi-component ... | 2004 | 15329728 |
| atp induces large quaternary rearrangements in a cage-like chaperonin structure. | the chaperonins, a family of molecular chaperones, are large oligomeric proteins that bind nonnative intermediates of protein folding. they couple the release and correct folding of their ligands to the binding and hydrolysis of atp. chaperonin 60 (cpn60) is a decatetramer (14-mer) of 60 kd subunits. folding of some ligands also requires the cooperation of cpn10, a heptamer of 10 kd subunits. | 1993 | 15335746 |
| bacterial acetone carboxylase is a manganese-dependent metalloenzyme. | bacterial acetone carboxylase catalyzes the atp-dependent carboxylation of acetone to acetoacetate with the concomitant production of amp and two inorganic phosphates. the importance of manganese in rhodobacter capsulatus acetone carboxylase has been established through a combination of physiological, biochemical, and spectroscopic studies. depletion of manganese from the r. capsulatus growth medium resulted in inhibition of acetone-dependent but not malate-dependent cell growth. under normal gr ... | 2004 | 15337755 |
| the role of extra fragment at the c-terminal of cytochrome b (residues 421-445) in the cytochrome bc1 complex from rhodobacter sphaeroides. | sequence alignment of cytochrome b of the cytochrome bc1 complex from various sources reveals that bacterial cytochrome b contain an extra fragment at the c terminus. to study the role of this fragment in bacterial cytochrome bc1 complex, rhodobacter sphaeroides mutants expressing his-tagged cytochrome bc1 complexes with progressive deletion from this fragment (residues 421-445) were generated and characterized. the cytbdelta-(433-445) bc1 complex, in which 13 residues from the c-terminal end of ... | 2004 | 15339929 |
| regulation of hem gene expression in rhodobacter capsulatus by redox and photosystem regulators rega, crtj, fnrl, and aerr. | biosynthetic pathways for heme and chlorophyll share common intermediates from 5-aminolevulinic acid through protoporphyrin ix. to obtain a better understanding of how photosynthetic organisms coordinate heme and chlorophyll biosynthesis, we have undertaken detailed analysis of the expression pattern of numerous heme biosynthesis genes in the purple photosynthetic bacterium rhodobacter capsulatus. beta-galactosidase reporter assays demonstrated that expression of hema, hemb, hemc, heme and hemz ... | 2004 | 15351643 |
| studies on the interaction of nadph with rhodobacter sphaeroides biotin sulfoxide reductase. | rhodobacter sphaeroides biotin sulfoxide reductase (bsor) contains the bis(molybdopterin guanine dinucleotide)molybdenum cofactor and catalyzes the reduction of d-biotin-d-sulfoxide to biotin. this protein is the only member of the dimethyl sulfoxide reductase family of molybdopterin enzymes that utilizes nadph as the direct electron donor to the catalytic mo center. kinetic studies using stopped-flow spectrophotometry indicate that bsor reduction by nadph (>1000 s(-1)) is faster than steady-sta ... | 2004 | 15366932 |
| nmr structural model of the interaction of herbicides with the photosynthetic reaction center from rhodobacter sphaeroides. | the interaction of the herbicides acifluorfen and paraquat with the photosynthetic reaction center from rhodobacter sphaeroides has been studied by nmr relaxation measurements. interaction in aqueous solution has been demonstrated by evaluating motional features of the bound form through cross-relaxation terms of protons at fixed distances on the herbicides. contributions to longitudinal nonselective relaxation rates different from the proton-proton dipolar relaxation were inferred, most probabl ... | 2004 | 15368575 |
| napf is a cytoplasmic iron-sulfur protein required for fe-s cluster assembly in the periplasmic nitrate reductase. | the periplasmic nitrate reductase (nap) is wide-spread in proteobacteria. napa, the nitrate reductase catalytic subunit, contains a mo-bismgd cofactor and one [4fe-4s] cluster. the nap gene clusters in many bacteria, including rhodobacter sphaeroides dsm158, contain an napf gene, disruption of which drastically decreases both in vitro and in vivo nitrate reductase activities. in spite its importance in the nap system, napf has never been characterized biochemically, and its role remains unknown. ... | 2004 | 15371424 |
| similarities between the abiotic reduction of selenite with glutathione and the dissimilatory reaction mediated by rhodospirillum rubrum and escherichia coli. | various mechanisms have been proposed to explain the biological dissimilatory reduction of selenite (seo3(2-)) to elemental selenium (se(o)), although none is without controversy. glutathione, the most abundant thiol in the eukaryotic cells, the cyanobacteria, and the alpha, beta, and gamma groups of the proteobacteria, has long been suspected to be involved in selenium metabolism. experiments with the phototrophic alpha proteobacterium rhodospirillum rubrum showed that the rate of selenite redu ... | 2004 | 15371444 |
| dehydration of (r)-2-hydroxyacyl-coa to enoyl-coa in the fermentation of alpha-amino acids by anaerobic bacteria. | several clostridia and fusobacteria ferment alpha-amino acids via (r)-2-hydroxyacyl-coa, which is dehydrated to enoyl-coa by syn-elimination. this reaction is of great mechanistic interest, since the beta-hydrogen, to be eliminated as proton, is not activated (pk 40-50). a mechanism has been proposed, in which one high-energy electron acts as cofactor and transiently reduces the electrophilic thiol ester carbonyl to a nucleophilic ketyl radical anion. the 2-hydroxyacyl-coa dehydratases are two-c ... | 2004 | 15374661 |
| temporary stabilization of electron on quinone acceptor side of reaction centers from the bacterium rhodobacter sphaeroides wild type and mutant sa(l223) depending on duration of light activation. | the dark reduction of photooxidized bacteriochlorophyll (p+) by photoreduced secondary quinone acceptor (qb-) in isolated reaction centers (rc) from the bacterium rhodobacter sphaeroides wild type and mutant strain sa(l223) depending on the duration of light activation of rc was studied. the kinetics of the dark reduction of p+ decreased with increasing light duration, which is probably due to conformational changes occurring under prolonged light activation in rc from the wild type bacterium. i ... | 2004 | 15377269 |
| acquirement and characterization of a carotenoid mutant (gm309) of rhodobacter sphaeroides 601. | a green mutant was obtained among the chemically induced mutants of rhodobacter sphaeroides 601 (rs601) and named gm309. a blue shift of 20 nm of the carotenoid absorption spectrum was found in the light-harvesting complex ii (lh2) of gm309. different from lh2 of rs601, it was found that the carotenoids in gm309-lh2 changed to be neurosporene by mutation. neurosporene lacks a conjugate double bond, compared with the spheroidene in rs601-lh2 which has ten conjugate double bonds. as shown by absor ... | 2004 | 15382676 |
| transmembrane charge separation during the ferryl-oxo -> oxidized transition in a nonpumping mutant of cytochrome c oxidase. | the n139d mutant of cytochrome c oxidase from rhodobacter sphaeroides retains full steady state oxidase activity but completely lacks proton translocation coupled to turnover in reconstituted liposomes (pawate, a. s., morgan, j., namslauer, a., mills, d., brzezinski, p., ferguson-miller, s., and gennis, r. b. (2002) biochemistry 41, 13417-13423). here, time-resolved electron transfer and vectorial charge translocation in the ferryl-oxo --> oxidized transition (transfer of the 4th electron in the ... | 2004 | 15385565 |
| properties of an intracellular poly(3-hydroxybutyrate) depolymerase (phaz1) from rhodobacter spheroides. | the gene of an intracellular poly(3-hydroxybutyrate) (iphb) depolymerase from rhodobacter sphaeroides was cloned and sequenced. the nucleotide sequence of the cloned gene was homologous to that of the iphb depolymerase gene from ralstonia eutropha h16 (phaz1(reu)) and the gene was designated phaz1(rsh). phaz1(rsh) was purified from e. coli harboring an expression vector containing phaz1(rsh) and its properties were examined. phaz1(rsh) degraded amorphous phb granules, and the 3-hydroxybutyrate t ... | 2004 | 15386104 |
| negatively charged residues and hydrogen bonds tune the ligand histidine pka values of rieske iron-sulfur proteins. | rieske proteins carry a redox-active iron-sulfur cluster, which is bound by two histidine and two cysteine side chains. the reduction potential of rieske proteins depends on ph. this ph dependence can be described by two pk(a) values, which have been assigned to the two iron-coordinating histidines. rieske proteins are commonly grouped into two major classes: rieske proteins from quinol-oxidizing cytochrome bc complexes, in which the ligand histidines titrate in the physiological ph range, and b ... | 2004 | 15449929 |
| [a discrepancy between the experimental and theoretical data on energy migration from b800 to b850 in lh-2 antennary complexes in purple bacteria]. | a discrepancy between the times of excitation transfer from b800 to b850 bacteriochlorophyll fractions in lh-2 complexes of purple bacteria was revealed. the experimental value (0.7-0.8 ps from literature sources) are at least four times lower than that (> 3.2 ps) calculated theoretically on the basis of recently obtained atomic structure of lh2. possible reasons for this discrepancy are discussed. | 2004 | 15458248 |
| dependence of tyrosine oxidation in highly oxidizing bacterial reaction centers on ph and free-energy difference. | the ph and temperature dependences of tyrosine oxidation were measured in reaction centers from mutants of rhodobacter sphaeroides containing a tyrosine residue near a highly oxidizing bacteriochlorophyll dimer. under continuous illumination, a rapid increase in the absorption change at 420 nm was observed because of the formation of a charge-separated state involving the oxidized dimer and reduced primary quinone, followed by a slow absorption decrease attributed to tyrosine oxidation. both the ... | 2004 | 15461463 |
| protein/lipid interaction in the bacterial photosynthetic reaction center: phosphatidylcholine and phosphatidylglycerol modify the free energy levels of the quinones. | the role of characteristic phospholipids of native membranes, phosphatidylcholine (pc), phosphatidylglycerol (pg), and cardiolipin (cl), was studied in the energetics of the acceptor quinone side in photosynthetic reaction centers of rhodobacter sphaeroides. the rates of the first, k(ab)(1), and the second, k(ab)(2), electron transfer and that of the charge recombination, k(bp), the free energy levels of q(a)(-)q(b) and q(a)q(b)(-) states, and the changes of charge compensating protein relaxatio ... | 2004 | 15461464 |
| the glutathione-glutaredoxin system in rhodobacter capsulatus: part of a complex regulatory network controlling defense against oxidative stress. | mutants with defects in components of the glutathione-glutaredoxin (gsh/grx) system of rhodobacter capsulatus were constructed to study its role in defense against oxidative stress and the redox-dependent formation of photosynthetic complexes. the lack of the glutaredoxin 3 gene (grxc) or the glutathione synthetase b gene (gshb) resulted in lower growth rates under aerobic conditions and higher sensitivity to oxidative stress, confirming the role of the gsh/grx system in oxidative stress defense ... | 2004 | 15466032 |
| detoxification of hydrogen peroxide and expression of catalase genes in rhodobacter. | the two related facultatively photosynthetic bacteria rhodobacter sphaeroides and rhodobacter capsulatus show different sensitivities against peroxide stress. r. sphaeroides is able to tolerate higher concentrations of h2o2 and exhibits higher catalase activity than r. capsulatus. the kate gene of r. sphaeroides and the katg gene of r. capsulatus are strongly induced by h2o2. this induction depends on the presence of the oxyr protein, which is able to bind to the promoter regions of these genes. ... | 2004 | 15470122 |
| chemotaxis in rhodobacter sphaeroides requires an atypical histidine protein kinase. | rhodobacter sphaeroides has a complex chemosensory system comprising two classic cheas, two atypical cheas, and eight response regulators (six cheys and two chebs). the classic cheas, chea(1) and chea(2), have similar domain structures to escherichia coli chea, whereas the atypical cheas, chea(3) and chea(4), lack some of the domains found in e. coli chea. chea(2), chea(3), and chea(4) are all essential for chemotaxis. here we demonstrate that chea(3) and chea(4) are both unable to undergo atp-d ... | 2004 | 15485885 |
| quantification of denitrifying bacteria in soils by nirk gene targeted real-time pcr. | denitrification, the reduction of nitrate to nitrous oxide or dinitrogen, is the major biological mechanism by which fixed nitrogen returns to the atmosphere from soil and water. microorganisms capable of denitrification are widely distributed in the environment but little is known about their abundance since quantification is performed using fastidious and time-consuming mpn-based approaches. we used real-time pcr to quantify the denitrifying nitrite reductase gene (nirk), a key enzyme of the d ... | 2004 | 15488276 |
| "paraffin wax-overlay of pour plate", a method for the isolation and enumeration of purple non-sulfur bacteria. | a modification of pour plate technique with an overlay of wax was used for isolation and enumeration of purple non-sulfur bacteria (pnsb) with equal efficiency as that of agar shake culture. the total count of pnsb ranged from 10(5)-10(8) cfu g dry soil(-1) and belonged to the genera of rhodobacter, rhodopseudomonas, rhodocista and rubrivivax. | 2004 | 15488284 |
| heme o synthase and heme a synthase from bacillus subtilis and rhodobacter sphaeroides interact in escherichia coli. | cytochrome c oxidase requires multiple heme and copper cofactors to catalyze the reduction of molecular oxygen to water. although significant progress has been made in understanding the transport and incorporation of the copper ions, considerably less is known about the trafficking and insertion of the heme cofactors. heme o synthase (hos) and heme a synthase (has) from rhodobacter sphaeroides (cox10 and cox15, respectively) and bacillus subtilis (ctab and ctaa, respectively) have been cloned an ... | 2004 | 15491161 |
| active site structure and redox processes of cytochrome c oxidase immobilised in a novel biomimetic lipid membrane on an electrode. | membrane-bound cytochrome c oxidase was attached to an electrode via a his-tag linker and studied by surface enhanced resonance raman spectroscopy, demonstrating intact redox site structures and electron transfer between the electrode and the immobilized enzyme. | 2004 | 15514773 |
| responses of the rhodobacter sphaeroides transcriptome to blue light under semiaerobic conditions. | exposure to blue light of the facultative phototrophic proteobacterium rhodobacter sphaeroides grown semiaerobically results in repression of the puc and puf operons involved in photosystem formation. to reveal the genome-wide effects of blue light on gene expression and the underlying photosensory mechanisms, transcriptome profiles of r. sphaeroides during blue-light irradiation (for 5 to 135 min) were analyzed. expression of most photosystem genes was repressed upon irradiation. downregulation ... | 2004 | 15516587 |
| light-harvesting complex 1 stabilizes p+qb- charge separation in reaction centers of rhodobacter sphaeroides. | the kinetics of charge recombination following photoexcitation by a laser pulse have been analyzed in the reaction center-light harvesting complex 1 (rc-lh1) purified from the photosynthetic bacterium rhodobacter sphaeroides. in rc-lh1 core complexes isolated from photosynthetically grown cells p(+)q(b)(-) recombines with an average rate constant, k approximately 0.3 s(-1), more than three times smaller than that measured in rc deprived of the lh1 (k approximately 1 s(-1)). a comparable, slowed ... | 2004 | 15518570 |
| transition state and encounter complex for fast association of cytochrome c2 with bacterial reaction center. | electrostatic interactions strongly enhance the electron transfer reaction between cytochrome (cyt) c(2) and reaction center (rc) from photosynthetic bacteria, yielding a second-order rate constant, k(2) approximately 10(9) s(-1).m(-1), close to the diffusion limit. the proposed mechanism involves an encounter complex (ec) stabilized by electrostatic interactions, followed by a transition state (ts), leading to the bound complex active in electron transfer. the effect of electrostatic interactio ... | 2004 | 15520377 |
| structure of the dimeric pufx-containing core complex of rhodobacter blasticus by in situ atomic force microscopy. | we have studied photosynthetic membranes of wild type rhodobacter blasticus, a closely related strain to the well studied rhodobacter sphaeroides, using atomic force microscopy. high-resolution atomic force microscopy topographs of both cytoplasmic and periplasmic surfaces of lh2 and rc-lh1-pufx (rc, reaction center) complexes were acquired in situ. the lh2 is a nonameric ring inserted into the membrane with the 9-fold axis perpendicular to the plane. the core complex is an s-shaped dimer compos ... | 2005 | 15522874 |
| identification and characterization of a novel vitamin b12 (cobalamin) biosynthetic enzyme (cobz) from rhodobacter capsulatus, containing flavin, heme, and fe-s cofactors. | one of the most intriguing steps during cobalamin (vitamin b12) biosynthesis is the ring contraction process that leads to the extrusion of one of the integral macrocyclic carbon atoms from the tetrapyrrole-derived framework. the aerobic cobalamin pathway requires the action of a monooxygenase called cobg (precorrin-3b synthase), which generates a hydroxylactone intermediate that is subsequently ring-contracted by cobj. however, in the photosynthetic bacterium rhodobacter capsulatus, which harbo ... | 2005 | 15525640 |
| [a network of hydrogen bonds in the reaction centers of rhodobacter sphaeroides serves as a regulatory factor of the temperature dependence of the recombination rate constant of photooxidized bacteriochlorophyll and primary quinone acceptors]. | the dark recombination rate constant for the photooxidized bacteriochlorophyll (p) and reduced primary quinone acceptor (qa) in the photosynthetic reaction centers (rc) from purple bacterium rhodobacter sphaeroides depends nonmonotonically on temperature. the time of this reaction is approximately 100 ms at 270-300 k and decreases as the temperature both increases and decreases beyond this temperature range. it is known that the dome-shaped dependence of the thermodynamic stability on temperatur ... | 2004 | 15526466 |
| [the temperature dependence of high-resolution 1h nmr spectra of rhodobacter sphaeroides photosynthetic reaction centres in a temperature range of 25-40 degrees c]. | high-resolution 1h-nmr spectra registered within a temperature range of 25-40 degrees c revealed a nonmonotonous dome-shaped temperature dependence of the ratio between integral nmr signal intensities determined at ppm intervals 2.5-4.5 and 0.2-2.5 with a maximum at 30 degrees c. this may be due to rc structural changes accompanying the temperature rise and accelerating the recombination reaction between oxidized bacteriochlorophyll and reduced primary quinone at temperatures above 30 degrees c. | 2004 | 15526467 |
| effects of the metalloid oxyanion tellurite (teo32-) on growth characteristics of the phototrophic bacterium rhodobacter capsulatus. | this work examines the effects of potassium tellurite (k2teo3) on the cell viability of the facultative phototroph rhodobacter capsulatus. there was a growth mode-dependent response in which cultures anaerobically grown in the light tolerate the presence of up to 250 to 300 microg of tellurite (teo3(2-)) per ml, while dark-grown aerobic cells were inhibited at tellurite levels as low as 2 microg/ml. the tellurite sensitivity of aerobic cultures was evident only for growth on minimal salt medium, ... | 2004 | 15528523 |
| elimination of polarity in the carotenoid terminus promotes the exposure of b850-binding sites (tyr 44, 45) and ans-mediated energy transfer in lh2 complexes of rhodobacter sphaeroides. | carotenoids in the peripheral light-harvesting complexes (lh2) of the green mutant (gm309) of rhodobacter sphaeroides were identified as containing neurosporenes, which lack the polar ch(3)o group, compared to spheroidenes in native-lh2 of r. sphaeroides 601. after lh2 complexes were treated with 1-anilino-8-naphthalene sulfonate (ans), new energy transfer pathways from ans or tryptophan to carotenoids were discovered in both native- and gm309-lh2. the carotenoid fluorescence intensity of gm309- ... | 2004 | 15530435 |
| trapped tyrosyl radical populations in modified reaction centers from rhodobacter sphaeroides. | the photosynthetic reaction center from the purple bacterium rhodobacter sphaeroides has been modified such that the bacteriochlorophyll dimer, when it becomes oxidized after light excitation, is capable of oxidizing tyrosine residues. one factor in this ability is a high oxidation-reduction midpoint potential for the dimer, although the location and protein environment of the tyrosine residue appear to be critical as well. these factors were tested in a series of mutants, each of which contains ... | 2004 | 15533042 |
| loktanella hongkongensis sp. nov., a novel member of the alpha-proteobacteria originating from marine biofilms in hong kong waters. | a gram-negative, non-motile, non-spore-forming, short rod-shaped bacterium (ust950701-009p(t)) was isolated from a marine biofilm in hong kong waters. colonies are pink in colour, convex with a smooth surface and entire edge. brown diffusible pigment is produced. whitish colonies, with otherwise identical morphology, emerge from every culture upon ageing. the white colonies can be maintained as separate cultures (ust950701-009w) without turning pink. ust950701-009p(t) and ust950701-009w have ide ... | 2004 | 15545471 |
| positive and negative transcriptional regulators of glutathione-dependent formaldehyde metabolism. | a glutathione (gsh)-dependent pathway is used for formaldehyde metabolism by a wide variety of prokaryotes and eukaryotes. in this pathway, s-hydroxymethylglutathione, produced by the reaction of formaldehyde with the thiolate moiety of glutathione, is the substrate for a gsh-dependent formaldehyde dehydrogenase (gsh-fdh). while expression of gsh-fdh often increases in the presence of metabolic or exogenous sources of formaldehyde, little is known about the factors that regulate this response. h ... | 2004 | 15547263 |
| effector-mediated interaction of cbbri and cbbrii regulators with target sequences in rhodobacter capsulatus. | in rhodobacter capsulatus, genes encoding enzymes of the calvin-benson-bassham reductive pentose phosphate pathway are located in the cbb(i) and cbb(ii) operons. each operon contains a divergently transcribed lysr-type transcriptional activator (cbbr(i) and cbbr(ii)) that regulates the expression of its cognate cbb promoter in response to an as yet unidentified effector molecule(s). both cbbr(i) and cbbr(ii) were purified, and the ability of a variety of potential effector molecules to induce ch ... | 2004 | 15547275 |
| structural intermediate in the photocycle of a bluf (sensor of blue light using fad) protein slr1694 in a cyanobacterium synechocystis sp. pcc6803. | slr1694 in synechocystis sp. pcc6803 is a family of blue-light photoreceptors based on flavin adenine dinucleotide (fad) called bluf (sensor of blue light using fad) proteins, which include appa from rhodobacter sphaeroides and pac from euglena gracilis. illumination of dark-state slr1694 at 15 degrees c reversibly induced a signaling light state characterized by the red shift in the uv-visible spectrum and by the light-induced fourier transform infrared (ftir) difference spectrum for structural ... | 2004 | 15554705 |
| neosynthesis of cardiolipin in rhodobacter sphaeroides under osmotic stress. | the phospholipid composition of rhodobacter sphaeroides cells resuspended in various hypertonic solutions has been examined by thin-layer chromatography and esi mass spectrometry. r. sphaeroides responds to hyperosmotic stress by increasing the amount of cardiolipin in the membranes; this phenomenon occurs in spheroplasts also. cardiolipin increases quickly and continuously during the time when the cells are resuspended in hypertonic medium. the optimum of stimulation of the neosynthesis of card ... | 2004 | 15554714 |
| rhodobacter capsulatus porphobilinogen synthase, a high activity metal ion independent hexamer. | the enzyme porphobilinogen synthase (pbgs), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. this paper reports new information on the metal ion independence and quaternary structure of pbgs from the photosynthetic bacterium rhodobacter capsulatus. | 2004 | 15555082 |
| chromophore composition of a heterologously expressed bluf-domain. | upon heterologous expression of the bluf (for: blue-light sensing using flavin) domain from appa, a transcriptional anti-repressor from rhodobacter sphaeroides, in escherichia coli, photoactive holo-protein is formed through non-covalent binding of a flavin. whereas it is generally assumed that fad is the physiological chromophore of this photo-perception domain in vivo, e. coli can (and does) insert, depending on the growth conditions, all naturally occurring flavins, i.e. riboflavin, fmn and f ... | 2004 | 15570388 |
| effects of expression of hema and hemb genes on production of porphyrin in propionibacterium freudenreichii. | the genus propionibacterium has a wide range of probiotic activities that are exploited in dairy and fermentation systems such as cheeses, propionic acid, and tetrapyrrole compounds. in order to improve production of tetrapyrrole compounds, we expressed the hema gene, which encodes delta-aminolevulinic acid (ala) synthase from rhodobacter sphaeroides, and the hemb gene, which encodes porphobilinogen (pbg) synthase from propionibacterium freudenreichii subsp. shermanii ifo12424, either monocistro ... | 2004 | 15574962 |
| molybdenum-containing hydroxylases. | unlike monooxygenases, molybdenum-containing hydroxylases catalyze the hydroxylation of carbon centers using oxygen derived ultimately from water, rather than o(2), as the source of the oxygen atom incorporated into the product, and do not require an external source of reducing equivalents. the mechanism by which this interesting chemistry takes place has been the subject of investigation for some time, and in the last several years the chemical course of the reaction has become increasingly wel ... | 2005 | 15581570 |
| crystallization and preliminary x-ray diffraction analysis of ferredoxin-nadp(h) reductase from rhodobacter capsulatus. | ferredoxin-nadp(h) reductase (272 amino acids) from rhodobacter capsulatus (fpr) has recently been postulated to be involved in the antioxidant response and to facilitate the provision of reduced flavodoxin for the reduction of nitrogenase. crystallization trials of recombinant fpr were carried out at 291 k by the hanging-drop vapour-diffusion method. orthorhombic crystals (unit-cell parameters a = 69.3, b = 93.6, c = 103.5 a) were obtained. however, their diffraction pattern was not satisfactor ... | 2004 | 15583382 |
| reconstitution and replacement of bacteriochlorophyll a molecules in photosynthetic reaction centers. | reaction centers (rcs) of the photosynthetic bacterium rhodobacter sphaeroides r-26 were reconstituted in liposomes after release of pigments (bacteriochlorophyll a (bchla) and bacteriopheophytin a (bphea)) by treatment with acetone. as shown by absorption and circular dichroism spectroscopies, the reconstituted rcs had the same arrangement of pigments as the native rc and exhibited photoactivity of the special pair. the recovery yield of rcs of up to 30% was achieved by addition of 7.8-fold exc ... | 2004 | 15598894 |
| localization of mreb in rhodobacter sphaeroides under conditions causing changes in cell shape and membrane structure. | mreb is thought to be a bacterial actin homolog that defines the morphology of rod-shaped bacteria. rhodobacter sphaeroides changes shape, from a rod to coccobacillus, and undergoes extensive cytoplasmic membrane invagination when it switches from aerobic to photoheterotrophic growth. the role of mreb in defining r. sphaeroides shape was therefore investigated. attempts at deleting or insertionally inactivating mreb were unsuccessful under all growth conditions. immunofluorescence microscopy sho ... | 2005 | 15601688 |
| identification of two new genes involved in diazotrophic growth via the alternative fe-only nitrogenase in the phototrophic purple bacterium rhodobacter capsulatus. | growth of rhodobacter capsulatus with molecular dinitrogen as the sole n source via the alternative fe-only nitrogenase requires all seven gene products of the anfhdgk-1-2-3 operon. in contrast to mutant strains carrying lesions in the structural genes of nitrogenase (anfh, anfd, anfg, and anfk), strains defective for either anf1, anf2, or anf3 are still able to reduce the artificial substrate acetylene, although with diminished activity. to obtain further information on the role of anf1, we scr ... | 2005 | 15601692 |
| the long-range organization of a native photosynthetic membrane. | photosynthesis relies on the delicate interplay between a specific set of membrane-bound pigment-protein complexes that harvest and transport solar energy, execute charge separation, and conserve the energy. we have investigated the organization of the light-harvesting (lh) and reaction-center (rc) complexes in native bacterial photosynthetic membranes of the purple bacterium rhodobacter sphaeroides by using polarized light spectroscopy, linear dichroism (ld) on oriented membranes. these ld meas ... | 2004 | 15601770 |
| binding of oxidized and reduced cytochrome c2 to photosynthetic reaction centers: plasmon-waveguide resonance spectroscopy. | the dissociation constants for the binding of oxidized and reduced wild-type cytochrome c(2) from rhodobacter capsulatus and the lysine 93 to proline mutant of cytochrome c(2) to photosynthetic reaction centers (rhodobacter sphaeroides) has been measured to high precision using plasmon-waveguide resonance spectroscopy. for the studies reported, detergent-solubilized photosynthetic reaction center was exchanged into a phosphatidylcholine lipid bilayer to approximate the physiological environment. ... | 2004 | 15610035 |
| specific radiation damage illustrates light-induced structural changes in the photosynthetic reaction center. | the photosynthetic reaction center of the purple non-sulfur bacterium blastochloris viridis was frozen in the presence and absence of illumination. differences in the resulting datasets are monitored using the difference fourier method. radiation damage is localized to those parts of the protein that are significant for electron transfer, and show changes that are sensitive to oxidation and protonation state. | 2004 | 15612703 |
| multiple scattering x-ray absorption studies of zn2+ binding sites in bacterial photosynthetic reaction centers. | binding of transition metal ions to the reaction center (rc) protein of the photosynthetic bacterium rhodobacter sphaeroides has been previously shown to slow light-induced electron and proton transfer to the secondary quinone acceptor molecule, q(b). on the basis of x-ray diffraction at 2.5 angstroms resolution a site, formed by asph124, hish126, and hish128, has been identified at the protein surface which binds cd(2+) or zn(2+). using zn k-edge x-ray absorption fine structure spectroscopy we ... | 2004 | 15613631 |
| evidence for electron equilibrium between the two hemes bl in the dimeric cytochrome bc1 complex. | structural analysis of the dimeric mitochondrial cytochrome bc1 complex suggests that electron transfer between inter-monomer hemes bl-bl may occur during bc1 catalysis. such electron transfer may be facilitated by the aromatic pairs present between the two bl hemes in the two symmetry-related monomers. to test this hypothesis, r. sphaeroides mutants expressing his6-tagged bc1 complexes with mutations at three aromatic residues (phe-195, tyr-199, and phe-203), located between two bl hemes, were ... | 2004 | 15615714 |
| a molecular dynamics study of water chain formation in the proton-conducting k channel of cytochrome c oxidase. | the formation of water chains in cytochrome c oxidase (cco) is studied by molecular dynamics (md). focus is on water chains in the k channel that can supply a proton to the binuclear center (the heme a3 fe/cub region), the site of o2 reduction. by assessing the presence of chains of any length on a short time scale (0.1 ps), a view of the kinds of chains and their persistence is obtained. chains from the entry of the channel on the inner membrane to thr359 (rhodobacter sphaeroides numbering) are ... | 2005 | 15620374 |
| proton slip in the atp synthase of rhodobacter capsulatus: induction, proton conduction, and nucleotide dependence. | fof1-atp synthase converts two energetic "currencies" of the cell (atp and protonmotive force, pmf) by coupling two rotary motors/generators. their coupling efficiency is usually very high. uncoupled proton leakage (slip) has only been observed in chloroplast enzyme at unphysiologically low nucleotide concentration. we investigated the properties of proton slip in chromatophores (sub-bacterial vesicles) from rhodobacter capsulatus in the single-enzyme-per-vesicle mode. the membrane was energized ... | 2005 | 15620379 |
| energetics of quinone-dependent electron and proton transfers in rhodobacter sphaeroides photosynthetic reaction centers. | proteins bind redox cofactors, modifying their electrochemistry and affinity by specific interactions of the binding site with each cofactor redox state. photosynthetic reaction centers from rhodobacter sphaeroides have three ubiquinone-binding sites, q(a), and proximal and distal q(b) sites. ubiquinones, which can be doubly reduced and bind 2 protons, have 9 redox states. however, only q and q(-) are seen in the q(a) site and q, q(-), and qh(2) in the proximal q(b) site. the distal q(b) functio ... | 2005 | 15628848 |
| membrane insertion of rhodopseudomonas acidophila light harvesting complex 2 investigated by high resolution afm. | light harvesting complexes 2 (lh2) are the peripheral antenna proteins in the bacterial photosynthetic apparatus and are built of alpha/beta-heterodimers containing three bacteriochlorophylls and two carotenoids each. previously, we have found in 2d-crystals that the complexes could be inserted within the membrane with a tilt with respect to the membrane plane (rhodobacter sphaeroides) or without tilt (rubrivivax gelatinosus). to investigate whether the tilted insertion represents the native sta ... | 2005 | 15629659 |
| functional consequences of the organization of the photosynthetic apparatus in rhodobacter sphaeroides: ii. a study of pufx- membranes. | in the bacterium r. sphaeroides, the polypeptide pufx is indispensable for photosynthetic growth. its deletion is known to have important consequences on the organization of the photosynthetic apparatus. in the wild-type strain, complexes between the reaction center (rc) and the antenna (light-harvesting complex 1 (lh1)) are associated in dimers, and lh1 does not fully encircle the rc. in the absence of pufx, the complexes become monomeric, and the lh1 ring closes around the rc. we analyzed the ... | 2005 | 15632163 |