| trapped water molecule in the charge separation of a bacterial reaction center. | low-frequency oscillations in the absorption spectrum at 1020 nm, connected to the primary charge separation process in rhodobacter sphaeroides, have been shown by yakovlev et al. to be caused by rotational motion of an interstitial water molecule called "water-a". the same water molecule was shown by potter et al. to increase the rate of charge separation by a factor of 8. we have carried out geometry optimization of water-a and its nearest atoms in the protein pocket, using density functional ... | 2008 | 18761433 |
| replacement of bacteriopheophytin in reaction centers from rhodobacter sphaeroides rs601 with plant pheophytin. | in the presence of acetone and an excess of exogenous plant pheophytins, bacteriopheophytins in the reaction centers from rhodobacter sphaeroides rs601 were replaced by pheophytins at sites h(a) and h(b), when incubated at 43.5 degrees c for more than 15 min. the substitution of bacteriopheophytins in the reaction centers was 50% and 71% with incubation of 15 and 60 min, respectively. in the absorption spectra of pheophytin-replaced reaction centers (phe rcs), bands assigned to the transition mo ... | 2000 | 18763112 |
| structural requirements for key residues and auxiliary portions of a bluf domain. | blrb in rhodobacter sphaeroides is a single domain, flavin-based blue light sensor protein in the bluf family of photoreceptors. consistent with other members of this family, blue light excitation induces a putative signaling state characterized by a 10 nm red shift in the uv-visible absorbance spectrum. structural and spectroscopic characterization of truncated blrb constructs establishes that the c-terminal 50 amino acids of this protein are essential to its structural integrity despite not be ... | 2008 | 18771279 |
| proton pumping mechanism in cytochrome c oxidase. | two different issues, important for the pumping mechanism of cyctochrome c oxidase, have been addressed in the present study. one of them concerns the nature of two key proton transfer transition states. a simple electrostatic model is used to suggest that the transition state (ts) for transfer to the pump-site should be positively charged, while the one for transfer to the binuclear center should be charge-neutral. the character of the former ts will guarantee that the protons will be pumped to ... | 2008 | 18774786 |
| compensatory thio-redox interactions between dsba, ccda and ccmg unveil the apocytochrome c holdase role of ccmg during cytochrome c maturation. | during cytochrome c maturation (ccm), the dsba-dependent thio-oxidative protein-folding pathway is thought to introduce a disulphide bond into the haem-binding motif of apocytochromes c. this disulphide bond is believed to be reduced through a thio-reductive pathway involving the ccm components ccda (dsbd), ccmg and ccmh. here, we show in rhodobacter capsulatus that in the absence of dsba cytochrome c levels were decreased and ccda or ccmg or the putative glutathione transporter cyddc was not ne ... | 2008 | 18786143 |
| kinetic analyses of the magnesium chelatase provide insights into the mechanism, structure, and formation of the complex. | the metabolic pathway known as (bacterio)chlorophyll biosynthesis is initiated by magnesium chelatase (bchi, bchd, bchh). this first step involves insertion of magnesium into protoporphyrin ix (proto), a process requiring atp hydrolysis. structural information shows that the bchi and bchd subunits form a double hexameric enzyme complex, whereas bchh binds proto and can be purified as bchh-proto. we utilized the rhodobacter capsulatus magnesium chelatase subunits using continuous magnesium chelat ... | 2008 | 18790730 |
| regb/rega, a global redox-responding two-component system. | the regb-rega 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, has been identified to be the ubiquinone pool in the membrane. regulation of regb autophos ... | 2008 | 18792686 |
| rhodobacter sphaeroides haem protein: a novel cytochrome with nitric oxide dioxygenase activity. | rhodobacter sphaeroides produces a novel cytochrome, designated as shp (sphaeroides haem protein), that is unusual in having asparagine as a redox-labile haem ligand. the gene encoding shp is contained within an operon that also encodes a dhc (dihaem cytochrome c) and a membrane-associated cytochrome b. dhc and shp have been shown to have high affinity for each other at low ionic strength (kd=0.2 microm), and dhc is able to reduce shp very rapidly. the reduced form of the protein, shp2+ (reduced ... | 2008 | 18793176 |
| expression characterization and actual function of the second pucba in rhodobacter sphaeroides. | the puc2ba operon of rhodobacter sphaeroides is highly similar to the original puc1ba operon. genetic, biochemical and spectroscopic approaches were used to investigate the function of puc2ba; the puc1ba and puc2ba structural genes were amplified and cloned into the prk415 vector controlled by the puc promoter from r. sphaeroides, which was then introduced into r. sphaeroides mutant strains. the results indicated that puc2ba was normally expressed and puc2ba-encoded polypeptides were assembled i ... | 2009 | 18798732 |
| the genome of rhodobacter sphaeroides strain 2.4.1 encodes functional cobinamide salvaging systems of archaeal and bacterial origins. | bacteria and archaea use distinct pathways for salvaging exogenous cobinamide (cbi), a precursor of adenosylcobalamin (coenzyme b(12)). the bacterial pathway depends on a bifunctional enzyme with kinase and guanylyltransferase activities (cobp in aerobic adenosylcobalamin synthesizers) to convert adenosylcobinamide (adocbi) to adocbi-guanosine diphosphate (adocbi-gdp) via an adocbi-phosphate intermediate. archaea lack cobp, and use a different strategy for the synthesis of adocbi-gdp. archaea cl ... | 2008 | 18808385 |
| physiology of phototrophic iron(ii)-oxidizing bacteria: implications for modern and ancient environments. | phototrophic iron(ii) [fe(ii)]-oxidizing bacteria are present in modern environments and evidence suggests that this metabolism was present already on early earth. we determined fe(ii) oxidation rates depending on ph, temperature, light intensity, and fe(ii) concentration for three phylogenetically different phototrophic fe(ii)-oxidizing strains (purple nonsulfur bacterium rhodobacter ferrooxidans sp. strain sw2, purple sulfur bacterium thiodictyon sp. strain f4, and green sulfur bacterium chlor ... | 2008 | 18811650 |
| epr, endor, and special triple measurements of p(*+) in wild type and modified reaction centers from rb. sphaeroides. | the influence of the protein environment on the primary electron donor, p, a bacteriochlorophyll a dimer, of reaction centers from rhodobacter sphaeroides, has been investigated using electron paramagnetic resonance and electron nuclear double resonance spectroscopy. these techniques were used to probe the effects on p that are due to alteration of three amino acid residues, his l168, asn l170, and asn m199. the introduction of glu at l168, asp at l170, or asp at m199 changes the oxidation/reduc ... | 2009 | 18819016 |
| [on the electron stabilization within the quinone acceptor part of rhodobacter sphaeroides photosynthetic reaction centers]. | the time evolution of the photoinduced differential absorption spectrum of isolated rhodobacter sphaeroides photosynthetic reaction centers was investigated. the measurements were carried out in the spectral region of 400-500 nm on the time scale of up to 200 microseconds. the spectral changes observed can be interpreted in terms of the effects of proton shift along hydrogen bonds between the primary quinone acceptor and the protein. a theoretical analysis of the spectrum time evolution was perf ... | 2008 | 18819279 |
| ethylmalonyl-coa mutase from rhodobacter sphaeroides defines a new subclade of coenzyme b12-dependent acyl-coa mutases. | coenzyme b(12)-dependent mutases are radical enzymes that catalyze reversible carbon skeleton rearrangement reactions. here we describe rhodobacter sphaeroides ethylmalonyl-coa mutase (ecm), a novel member of the family of coenzyme b(12)-dependent acyl-coa mutases, that operates in the recently discovered ethylmalonyl-coa pathway for acetate assimilation. ecm is involved in the central reaction sequence of this novel pathway and catalyzes the transformation of ethylmalonyl-coa to methylsuccinyl- ... | 2008 | 18819910 |
| evaluation of performance and microbial ecology of sequencing batch reactor and membrane bioreactor treating thin-film transistor liquid crystal display wastewater. | in taiwan, a substantial amount of thin-film transistor liquid crystal display (tft-lcd) wastewater is produced daily due to an increasing production of the opto-electronic industry in recent years. the main components of tft-lcd wastewater include dimethyl sulphoxide (dmso), monoethanolamine (mea), and tetra-methyl ammonium hydroxide (tmah), which are recognized as non-or slow-biodegradable organic compounds and limited information is available regarding their biological treatablility. this stu ... | 2008 | 18824808 |
| characterization of ornithine and glutamine lipids extracted from cell membranes of rhodobacter sphaeroides. | the identification and structural characterization of a series of ornithine lipids extracted from the cell membranes of wild-type rhodobacter sphaeroides, as well as from a glycerophosphocholine-deficient strain, have been achieved by multistage tandem mass spectrometry of their protonated and deprotonated precursor ions in a linear quadrupole ion trap. systematic examination of the multistage gas-phase fragmentation reactions of these ions, combined with the use of hydrogen/deuterium exchange, ... | 2009 | 18835523 |
| cytotoxic activities of extracts and compounds from viscum coloratum and its transformation products by rhodobacter sphaeroides. | the bioassay-oriented fractionation of mistletoe crude extracts (mcee) using 75% ethanol and culture products of mistletoe transformed by rhodobacter sphaeroides, a photosynthetic bacterium (psbt), revealed that the high cytotoxic activities were due to the petroleum ether extracts (pes) and the acid-precipitated proteins from the aqueous extracts (aqs) of mcee and psbt. the isolated triterpenes may account for the activities of the pes of mcee and psbt, respectively. extraction of mcee using pe ... | 2009 | 18839075 |
| spectrally silent light induced conformation change in photosynthetic reaction centers. | spectrally silent conformation change after photoexcitation of photosynthetic reaction centers isolated from rhodobacter sphaeroides r-26 was observed by the optical heterodyne transient grating technique. the signal showed spectrally silent structural change in photosynthetic reaction centers followed by the primary p+bph- charge separation and this change remains even after the charge recombination. without bound quinone to the rc, the conformation change relaxes with about 28micros lifetime. ... | 2008 | 18840436 |
| accumulation of chlorophyllous pigments esterified with the geranylgeranyl group and photosynthetic competence in the ct2256-deleted mutant of the green sulfur bacterium chlorobium tepidum. | green sulfur bacteria contain chlorophyllous pigments, chlorophyll (chl) apd and bacteriochlorophyll (bchl) ap, esterified with delta2,6-phytadienol and phytol, respectively, which would be produced by reduction of the geranylgeranyl group at the c-17 propionate residue. in the genome of chlorobium tepidum, two paralogous genes presumably encoding geranylgeranyl reductase, ct1232 and ct2256, are found. the deletion mutants of the ct1232 and ct2256 genes were constructed using an insertional inac ... | 2008 | 18846281 |
| functional expression of nitrogenase-like protochlorophyllide reductase from rhodobacter capsulatus in escherichia coli. | dark-operative protochlorophyllide oxidoreductase (dpor) is a nitrogenase-like enzyme catalyzing d-ring reduction of protochlorophyllide in chlorophyll and bacteriochlorophyll biosynthesis. dpor consists of two components, l-protein and nb-protein, which are structurally related to nitrogenase fe-protein and mofe-protein, respectively. neither fe-protein nor mofe-protein is expressed as an active form in escherichia coli due to the requirement of many nif proteins for the assembly of the metallo ... | 2008 | 18846289 |
| regulation of aerobic photosystem synthesis in the purple bacterium rhodospirillum centenum by crtj and aerr. | genes coding for putative crtj and aerr homologs were identified and characterized in the purple photosynthetic bacterium rhodospirillum centenum (also known as rhodocista centenaria), an organism that synthesizes photopigments even under highly aerated conditions. mutational analysis indicated that in rsp. centenum, gene crtj codes for a repressor for photosynthesis gene expression as in rhodobacter capsulatus, which exhibits a high level of oxygen repression of photosystem synthesis. in contra ... | 2008 | 18846293 |
| correlating ultrafast function with structure in single crystals of the photosynthetic reaction center. | femtosecond transient absorbance spectroscopy was applied to the study of primary electron transfer in single reaction center crystals from rhodobacter sphaeroides. polarized transient absorption spectra of individual crystals are shown to correlate with polarized ground-state absorption spectra and to track cofactor transition moment directions calculated from the crystallographic structure. electron transfer from the bacteriochlorophyll dimer to the bacteriopheophytin acceptor was found to be ... | 2008 | 18847224 |
| proton-dependent electron transfer from cua to heme a and altered epr spectra in mutants close to heme a of cytochrome oxidase. | eukaryotic cytochrome c oxidase (cco) and homologous prokaryotic forms of rhodobacter and paraccocus differ in the epr spectrum of heme a. it was noted that a histidine ligand of heme a (h102) is hydrogen bonded to serine in rhodobacter (s44) and paraccocus ccos, in contrast to glycine in the bovine enzyme. mutation of s44 to glycine shifts the heme a epr signal from g(z) = 2.82 to 2.86, closer to bovine heme a at 3.03, without modifying other properties. mutation to aspartate, however, results ... | 2008 | 18847227 |
| theoretical investigation of the electronic asymmetry of the special pair cation radical in the photosynthetic type-ii reaction center. | the electronic asymmetry of the special pair cation radical in the photosynthetic reaction center was studied, using density functional calculations with a polarizable continuum model and a point charge model as the protein environment. the calculated spin density distribution between the halves of the special pair from rhodobacter sphaeroides agreed well with the experimental value due to the protein polarity effect. the differences in the specific orientations of the ester carbonyl groups of t ... | 2008 | 18847236 |
| understanding chlorophylls: central magnesium ion and phytyl as structural determinants. | phytol, a c20 alcohol esterifying the c-17(3) propionate, and mg2+ ion chelated in the central cavity, are conservative structural constituents of chlorophylls. to evaluate their intramolecular structural effects we prepared a series of metal- and phytyl-free derivatives of bacteriochlorophyll a and applied them as model chlorophylls. a detailed spectroscopic study on the model pigments reveals meaningful differences in the spectral characteristics of the phytylated and non-phytylated pigments. ... | 2008 | 18848915 |
| heterologous synthesis and assembly of functional lhii antenna complexes from rhodovulum sulfidophilum in rhodobacter sphaeroides mutant. | the light harvesting complexes, including lhii and lhi, are the important components of photosynthetic apparatus. rhodovulum (rdv.) sulfidophilum and rhodobacter (r.) sphaeroides belong to two genera of photosynthetic bacteria, and they are very different in some physiological characteristics and light harvesting complexes structure. the lhii structural genes (pucbsas) from rdv. sulfidophilum and the lhi structural genes (pufba) from r. sphaeroides were amplified, and cloned into an expression v ... | 2009 | 18850303 |
| purification and characterization of 3,4-dihydroxyphenylalanine oxidative deaminase from rhodobacter sphaeroides ou5. | an enzyme involved in the catabolism of 3,4-dihydroxyphenylalanine (dopa) was isolated from rhodobacter sphaeroides ou5. the enzyme catalyzes the formation of 3,4-dihydroxyphenylpyruvic acid (dopp) and ammonia from dopa. formation of ammonia by dopa oxidative deaminase was o2 dependent and the enzyme isolated to its homogeneity has 100% affinity for dopa. dopa oxidative deaminase is functional at low concentrations of the substrate (< 100 micromol.l(-1)) and is independent of nadh. the molecular ... | 2008 | 18923551 |
| hierarchical regulation of photosynthesis gene expression by the oxygen-responsive prrba and appa-ppsr systems of rhodobacter sphaeroides. | in the facultatively phototrophic proteobacterium rhodobacter sphaeroides, formation of the photosynthetic apparatus is oxygen dependent. when oxygen tension decreases, the response regulator prra of the global two-component prrba system is believed to directly activate transcription of the puf, puh, and puc operons, encoding structural proteins of the photosynthetic complexes, and to indirectly upregulate the photopigment biosynthesis genes bch and crt. decreased oxygen also results in inactiva ... | 2008 | 18931128 |
| excitation wavelength dependence of primary charge separation in reaction centers from rhodobacter sphaeroides. | the excitation wavelength dependence of the initial electron transfer rate in both wild type and mutant reaction centers from rhodobacter sphaeroides has been studied between 840 and 920 nm as a function of temperature (10-295 k). the dynamics of primary charge separation show no resolvable excitation wavelength dependence at room temperature over this spectral range. a small variation in rate with excitation wavelength is observed at cryogenic temperatures. the low temperature results cannot be ... | 2008 | 18939793 |
| organisation and function of the phaeospirillum molischianum photosynthetic apparatus. | we have investigated the organisation of the photosynthetic apparatus in phaeospirillum molischianum, using biochemical fractionation and functional kinetic measurements. we show that only a fraction of the atp-synthase is present in the membrane regions which contain most of the photosynthetic apparatus and that, despite its complicated stacked structure, the intracytoplasmic membrane delimits a single connected space. we find that the diffusion time required for a quinol released by the reacti ... | 2008 | 18948077 |
| intrinsic uncoupling in the atp synthase of escherichia coli. | the atp hydrolysis activity and proton pumping of the atp synthase of escherichia coli in isolated native membranes have been measured and compared as a function of adp and pi concentration. the atp hydrolysis activity was inhibited by pi with an half-maximal effect at 140 microm, which increased progressively up in the millimolar range when the adp concentration was progressively decreased by increasing amounts of an adp trap. in addition, the relative extent of this inhibition decreased with d ... | 2008 | 18952048 |
| the road to the crystal structure of the cytochrome bc1 complex from the anoxigenic, photosynthetic bacterium rhodobacter sphaeroides. | the advantages of using bacterial systems to study the mechanism and function of cytochrome bc (1) complexes do not extend readily to their structural investigations. high quality crystals of bacterial complexes have been difficult to obtain despite the enzymes' smaller sizes and simpler subunit compositions compared to their mitochondrial counterparts. in the course of the structure determination of the bc (1) complex from r. sphaeroides, we observed that the growth of only low quality crystals ... | 2008 | 18953640 |
| movement of the iron-sulfur head domain of cytochrome bc(1) transiently opens the catalytic q(o) site for reaction with oxygen. | cytochrome bc(1), a key enzyme of biological energy conversion, generates or uses a proton motive force through the q cycle that operates within the two chains of cofactors that embed two catalytic quinone oxidation/reduction sites, the q(o) site and the q(i) site. the q(o) site relies on the joint action of two cofactors, the iron-sulfur (fes) cluster and heme b(l). side reactions of the q cycle involve a generation of superoxide which is commonly thought to be a product of an oxidation of a hi ... | 2008 | 18956890 |
| heavy metal ions inhibit molybdoenzyme activity by binding to the dithiolene moiety of molybdopterin in escherichia coli. | molybdenum insertion into the dithiolene group on the 6-alkyl side-chain of molybdopterin is a highly specific process that is catalysed by the moea and moga proteins in escherichia coli. ligation of molybdate to molybdopterin generates the molybdenum cofactor, which can be inserted directly into molybdoenzymes binding the molybdopterin form of the molybdenum cofactor, or is further modified in bacteria to form the dinucleotide form of the molybdenum cofactor. the ability of various metals to bi ... | 2008 | 18959753 |
| mathematical model for the analytical signal of an herbicide sensor based on the reaction centre of rhodobacter sphaeroides. | this paper introduces a mathematical model which makes it possible both to determine the concentration of photosynthetic herbicides and to obtain a quantitative parameter in order to compare their activity using a previously described sensing system. the working principle involves the changes in absorption properties at 860nm of the reaction centre (rc) isolated from the bacteria rhodobacter sphaeroides when photosynthetic herbicides are present. the method has been used for the determination an ... | 2005 | 18969839 |
| coenzyme binding and hydride transfer in rhodobacter capsulatus ferredoxin/flavodoxin nadp(h) oxidoreductase. | ferredoxin-nadp(h) reductases catalyse the reversible hydride/electron exchange between nadp(h) and ferredoxin/flavodoxin, comprising a structurally defined family of flavoenzymes with two distinct subclasses. those present in gram-negative bacteria (fprs) display turnover numbers of 1-5 s(-1) while the homologues of cyanobacteria and plants (fnrs) developed a 100-fold activity increase. we investigated nucleotide interactions and hydride transfer in rhodobacter capsulatus fpr comparing them to ... | 2009 | 18973834 |
| the hupr receiver domain crystal structure in its nonphospho and inhibitory phospho states. | hydrogen uptake protein regulator (hupr) is a member of the nitrogen regulatory protein c (ntrc) family of response regulators. these proteins activate transcription by rna polymerase (rnap) in response to a change in environment. this change is detected through the phosphorylation of their receiver domain as part of a two-component signalling pathway. hupr is an unusual member of this family as it activates transcription when unphosphorylated, and transcription is inhibited by phosphorylation. ... | 2009 | 18977359 |
| rpoh(ii) activates oxidative-stress defense systems and is controlled by rpoe in the singlet oxygen-dependent response in rhodobacter sphaeroides. | photosynthetic organisms need defense systems against photooxidative stress caused by the generation of highly reactive singlet oxygen ((1)o(2)). here we show that the alternative sigma factor rpoh(ii) is required for the expression of important defense factors and that deletion of rpoh(ii) leads to increased sensitivity against exposure to (1)o(2) and methylglyoxal in rhodobacter sphaeroides. the gene encoding rpoh(ii) is controlled by rpoe, and thereby a sigma factor cascade is constituted. we ... | 2009 | 18978062 |
| functional analysis of a large non-conserved region of flgk (hap1) from rhodobacter sphaeroides. | the single subpolar flagellum of rhodobacter sphaeroides shows an enlarged hook-filament junction. one of the two proteins that compose this section of the filament is hap1(rs) (flgk(rs)) it contains a central non-conserved region of 860 amino acids that makes this protein about three times larger than its homologue in salmonella enterica serovar typhimurium. we investigated the role of this central portion of the unusually large hap1 protein of r. sphaeroides by monitoring the effects of serial ... | 2009 | 19003427 |
| [distribution of bacteriochlorophyll between the pigment-protein complexes of the sulfur photosynthesizing bacterium allochromatium minutissimum depending on light intensity at different temperatures]. | variation of the distribution of bacteriochlorophyll a (bchl a) between external antenna (lh2) and core complexes (lhl + rc) of the photosynthetic membrane of the sulfur bacterium allochromatium minutissimum was studied at light intensities of 5 and 90 wt/m2 in the temperature range of 12-43 degrees c. the increase of light intensity was shown to result in a 1.5- to 2-times increase of a photosynthetic unit (psu). psu sizes pass through a maximum depending on growth temperature, and the increase ... | 2008 | 19004340 |
| [effect of growth conditions on electrophysical properties of rhodobacter capsulatus pg cells]. | electrophysical characteristics of cells of the phototrophic bacterium rhodobacter capsulatus pg grown in complete hutner medium in light or dark were found to differ depending on the composition of their lipopolysaccharides (lps). under dark cultivation, the cells synthesized lps with a shortened structure that determined the electrophoretic properties of cell surfaces. the observed decrease in the effective high-frequency electroconductivity of the dark-grown cells is assumed to be due to a de ... | 2008 | 19004345 |
| major mo(v) epr signature of rhodobacter sphaeroides periplasmic nitrate reductase arising from a dead-end species that activates upon reduction. relation to other molybdoenzymes from the dmso reductase family. | enzymes of the dmso reductase family use a mononuclear mo-bis(molybdopterin) cofactor (moco) to catalyze a variety of oxo-transfer reactions. much functional information on nitrate reductase, one of the most studied members of this family, has been gained from epr spectroscopy, but this technique is not always conclusive because the signature of the moco is heterogeneous, and which signals correspond to active species is still unsure. we used site-directed mutagenesis, epr and protein film volta ... | 2008 | 19006273 |
| crystal structure of the l protein of rhodobacter sphaeroides light-independent protochlorophyllide reductase with mgadp bound: a homologue of the nitrogenase fe protein. | the l protein (bchl) of the dark-operative protochlorophyllide reductase (dpor) from rhodobacter sphaeroides has been purified from an azotobacter vinelandii expression system; its interaction with nucleotides has been examined, and the x-ray structure of the protein has been determined with bound mgadp to 1.6 a resolution. dpor catalyzes the reduction of protochlorophyllide to chlorophyllide, a reaction critical to the biosynthesis of bacteriochlorophylls. the dpor holoenzyme is comprised of tw ... | 2008 | 19006326 |
| a bifunctional kinase-phosphatase in bacterial chemotaxis. | phosphorylation-based signaling pathways employ dephosphorylation mechanisms for signal termination. histidine to aspartate phosphosignaling in the two-component system that controls bacterial chemotaxis has been studied extensively. rhodobacter sphaeroides has a complex chemosensory pathway with multiple homologues of the escherichia coli chemosensory proteins, although it lacks homologues of known signal-terminating chey-p phosphatases, such as chez, chec, fliy or chex. here, we demonstrate th ... | 2008 | 19020080 |
| gene transfer agent (gta) genes reveal diverse and dynamic roseobacter and rhodobacter populations in the chesapeake bay. | within the bacterial class alphaproteobacteria, the order rhodobacterales contains the roseobacter and rhodobacter clades. roseobacters are abundant and play important biogeochemical roles in marine environments. roseobacter and rhodobacter genomes contain a conserved gene transfer agent (gta) gene cluster, and gta-mediated gene transfer has been observed in these groups of bacteria. in this study, we investigated the genetic diversity of these two groups in chesapeake bay surface waters using a ... | 2009 | 19020557 |
| primary charge separation in the reaction centers of rhodobacter sphaeroides mutants l153hy and l153hy+m182hl. | | 2008 | 19024567 |
| complete genome sequence of rhodobacter sphaeroides kd131. | rhodobacter sphaeroides is a purple nonsulfur photosynthetic bacterium that is considered a possible source of h(2) production. r. sphaeroides kd131, which was isolated from sea mud in south korea, was found to produce high levels of h(2). here we report the complete and annotated genome sequence of r. sphaeroides kd131. | 2009 | 19028901 |
| serine in bluf domains displays spectral importance in computational models. | the bluf (blue-light sensing using flavine) domain of the appa photoreceptor protein from rhodobacter sphaeroides was modelled by using quantum chemical chromophore plus amino acid models at the (td-)b3lyp/6-31g * level of theory. the models were based on nmr structures, and further refined by charmm force field molecular dynamics simulations. the goal is to explain the total redshift by about 10nm in the uv/vis spectra of bluf domains after illumination, and to relate it to structural changes. ... | 2009 | 19036599 |
| molecular scale photodiode composed of recombinant ferredoxin/chlorophyll a heterostructure. | photoelectrical rectifying property of biomolecular heterostructures is investigated in molecular scale. recombinant ferredoxin and chlorophyll a were used as an electron acceptor and a sensitizer respectively in the molecular layer by mimicking photosynthesis. a self-assembled monolayer of recombinant ferredoxin was formed on au surface, and then chlorophyll a was deposited onto the recombinant ferredoxin layer by langmuir-blodgett method. the formation of recombinant ferredoxin/chlorophyll a h ... | 2008 | 19049051 |
| spectroscopic and computational studies of nitrite reductase: proton induced electron transfer and backbonding contributions to reactivity. | a combination of spectroscopy and dft calculations has been used to define the geometric and electronic structure of the nitrite bound type 2 (t2) copper site at high and low ph in nitrite reductase from rhodobacter sphaeroides. at high ph there is no electron transfer from reduced type 1 (t1) to the nitrite bound t2 copper, while protonation triggers t1 --> t2 electron transfer and generation of no. the dft calculated reaction coordinate for the n-o bond cleavage in nitrite reduction by the red ... | 2009 | 19053185 |
| interaction between cytochrome c2 and the photosynthetic reaction center from rhodobacter sphaeroides: role of interprotein hydrogen bonds in binding and electron transfer. | the role of short-range hydrogen bond interactions at the interface between electron transfer proteins cytochrome c(2) (cyt) and the reaction center (rc) from rhodobacter sphaeroides was studied by mutation (to ala) of rc residues asn m187, asn m188, and gln l258 which form interprotein hydrogen bonds to cyt in the cyt-rc complex. the largest decrease in binding constant k(a) (8-fold) for a single mutation was observed for asn m187, which forms an intraprotein hydrogen bond to the key residue ty ... | 2008 | 19053264 |
| soluble proteome investigation of cobalt effect on the carotenoidless mutant of rhodobacter sphaeroides. | to investigate the surviving capability of rhodobacter sphaeroides under phototrophic conditions in the presence of high cobalt concentration and its influence on the photosynthetic apparatus biosynthesis. | 2009 | 19054232 |
| vectorial proton transfer coupled to reduction of o2 and no by a heme-copper oxidase. | the heme-copper oxidase (hcuo) superfamily consists of integral membrane proteins that catalyze the reduction of either oxygen or nitric oxide. the hcuos that reduce o(2) to h(2)o couple this reaction to the generation of a transmembrane proton gradient by using electrons and protons from opposite sides of the membrane and by pumping protons from inside the cell or organelle to the outside. the bacterial no-reductases (nor) reduce no to n(2)o (2no + 2e(-) + 2h(+) --> n(2)o + h(2)o), a reaction a ... | 2008 | 19074284 |
| protein-protein interactions between cbbr and rega (prra), transcriptional regulators of the cbb operons of rhodobacter sphaeroides. | cbbr and rega (prra) are transcriptional regulators of the cbb(i) and cbb(ii) (calvin-benson-bassham co(2) fixation pathway) operons of rhodobacter sphaeroides. both proteins interact specifically with promoter sequences of the cbb operons. rega has four dna binding sites within the cbb(i) promoter region, with the cbbr binding site and rega binding site 1 overlapping each other. this study demonstrated that cbbr and rega interact and form a discrete complex in vitro, as illustrated by gel mobil ... | 2009 | 19077171 |
| photoproduction of hydrogen by rhodobacter capsulatus from thermophilic fermentation effluent. | rhodobacter capsulatus was used for the phototrophic hydrogen production on effluent solution derived from the thermophilic fermentation of miscanthus hydrolysate by thermotoga neapolitana. pretreatments such as centrifugation, dilution, buffer addition, ph adjustment and sterilization were suggested for the effluent before being fed to the photofermentation. batch-wise experiments showed that r. capsulatus grows and produces hydrogen on the pretreated effluent solution. moreover, it was found t ... | 2009 | 19082632 |
| mediated electrochemistry of dimethyl sulfoxide reductase from rhodobacter capsulatus. | electrochemically driven catalysis of the bacterial enzyme dimethyl sulfoxide (dmso) reductase (rhodobacter capsulatus) has been studied using the macrocyclic complex (trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)cobalt(iii) as a mediator. in the presence of both dmso and dmso reductase, the normal transient co(iii/ii) voltammetric response of the complex is transformed into an amplified and sigmoidal (steady-state) waveform characteristic of a catalytic ec' mechanism. at l ... | 2009 | 19082848 |
| growth arrest of synechocystis sp. pcc6803 by superoxide generated from heterologously expressed rhodobacter sphaeroides chlorophyllide a reductase. | the photosynthetic growth of synechocystis sp. pcc6803 ceased upon expression of rhodobacter sphaeroides chlorophyllide a reductase (cor). however, an increase in cytosolic superoxide dismutase level in the recombinant synechocystis sp. pcc6803 completely reversed the growth cessation. this demonstrates that cor generates superoxide in synechocystis sp. pcc6803. considering the dissolved oxygen (do) level suitable for cor, the intracellular do of this oxygenic photosynthetic cell appears to be l ... | 2009 | 19084011 |
| density functional studies of the spin density distribution of the p865 cation radical in the reaction center of rb sphaeroides. | density functional calculations are used to calculate the spin density distribution for the p865 dimer cation radical in the rb sphaeroides reaction center. comparison between calculated and experimental hyperfine couplings is performed where good agreement is found for the four nitrogen and 121 proton methyl group hyperfine couplings. overall, the spin density ratio between the two halves is in agreement with experimental determinations, although the calculations suggest that significant differ ... | 2008 | 19086272 |
| proton environment of reduced rieske iron-sulfur cluster probed by two-dimensional eseem spectroscopy. | the proton environment of the reduced [2fe-2s] cluster in the water-soluble head domain of the rieske iron-sulfur protein (isf) from the cytochrome bc(1) complex of rhodobacter sphaeroides has been studied by orientation-selected x-band 2d eseem. the 2d spectra show multiple cross-peaks from protons, with considerable overlap. samples in which (1)h(2)o water was replaced by (2)h(2)o were used to determine which of the observed peaks belong to exchangeable protons, likely involved in hydrogen bon ... | 2009 | 19099453 |
| proteomic analysis and identification of the structural and regulatory proteins of the rhodobacter capsulatus gene transfer agent. | the gene transfer agent of rhodobacter capsulatus (gta) is a unique phage-like particle that exchanges genetic information between members of this same species of bacterium. besides being an excellent tool for genetic mapping, the gta has a number of advantages for biotechnological and nanoengineering purposes. to facilitate the gta purification and identify the proteins involved in gta expression, assembly and regulation, in the present work we construct and transform into r. capsulatus y262 a ... | 2009 | 19105630 |
| epr evidence of cyanide binding to the mn(mg) center of cytochrome c oxidase: support for cu(a)-mg involvement in proton pumping. | we examined the anion binding behavior of the mg(mn) site in cytochrome c oxidase to test a possible role of this center in proton pumping. rhodobacter sphaeroides grown in a mn(ii)-rich medium replaces the intrinsic mg(ii) ion with an epr-detectable mn(ii) ion without change in activity. due to its close proximity and a shared ligand, oxidized cu(a) is spin-coupled to the mn(ii) ion, affecting the epr spectrum. an examination of both bovine and r.s. oxidase crystal structures reveals a hydrogen ... | 2009 | 19108635 |
| mechanism of substrate and inhibitor binding of rhodobacter capsulatus xanthine dehydrogenase. | rhodobacter capsulatus xanthine dehydrogenase (xdh) is an (alphabeta)(2) heterotetrameric cytoplasmic enzyme that resembles eukaryotic xanthine oxidoreductases in respect to both amino acid sequence and structural fold. to obtain a detailed understanding of the mechanism of substrate and inhibitor binding at the active site, we solved crystal structures of r. capsulatus xdh in the presence of its substrates hypoxanthine, xanthine, and the inhibitor pterin-6-aldehyde using either the inactive des ... | 2009 | 19109249 |
| substrate orientation and catalysis at the molybdenum site in xanthine oxidase: crystal structures in complex with xanthine and lumazine. | xanthine oxidoreductase is a ubiquitous cytoplasmic protein that catalyzes the final two steps in purine catabolism. we have previously investigated the catalytic mechanism of the enzyme by rapid reaction kinetics and x-ray crystallography using the poor substrate 2-hydroxy-6-methylpurine, focusing our attention on the orientation of substrate in the active site and the role of arg-880 in catalysis. here we report additional crystal structures of as-isolated, functional xanthine oxidase in the c ... | 2009 | 19109252 |
| unusual temperature dependence of photosynthetic electron transfer due to protein dynamics. | the initial electron transfer rate and protein dynamics in wild type and five mutant reaction centers from rhodobacter sphaeroides have been studied as a function of temperature (10-295 k). detailed kinetic measurements of initial electron transfer in rhodobacter sphaeroides reaction centers can be quantitatively described by a reaction diffusion formalism at all temperatures from 10 to 295 k. in this model, the time course of electron transfer is determined by the ability of the protein to inte ... | 2009 | 19115814 |
| light-activated cytotoxic compounds from malaysian microorganisms for photodynamic therapy of cancer. | photodynamic therapy (pdt) is a promising cancer treatment which involves activation of a photosensitizing drug with light to produce reactive oxygen species that kill tumors without causing damage to unirradiated normal tissues. to date, only photofrin, foscan and levulan have been approved for clinical treatment of cancer. tropical habitats such as those found in malaysia are attractive sources of new therapeutic compounds as tremendous chemical diversity is found in a large number of plants, ... | 2009 | 19125347 |
| low-temperature studies of electron transfer to the m side of yfh reaction centers from rhodobacter capsulatus. | there have been extensive experimental and theoretical studies of the temperature dependence of the rates of electron transfer between the cofactors associated primarily with the l polypeptide (or a branch) in the bacterial photosynthetic reaction center (rc). the focus of this paper is to gain further insight into the temperature dependence of rate of initial electron transfer to the parallel cofactor chain associated mainly with the m polypeptide (or b branch), which is inactive in the native ... | 2009 | 19132840 |
| catalytic properties of the expressed acyclic carotenoid 2-ketolases from rhodobacter capsulatus and rubrivivax gelatinosus. | purple photosynthetic bacteria synthesize the acyclic carotenoids spheroidene and spirilloxanthin which are ketolated to spheroidenone and 2,2'-diketospirilloxanthin under aerobic growth. for the studies of the catalytic reaction of the ketolating enzyme, the crta genes from rubrivivax gelatinosus and rhodobacter capsulatus encoding acyclic carotenoid 2-ketolases were expressed in escherichia coli to functional enzymes. with the purified enzyme from the latter, the requirement of molecular oxyge ... | 2009 | 19136077 |
| coenzyme q10 production by rhodobacter sphaeroides in stirred tank and in airlift bioreactor. | a higher coenzyme q(10) (coq(10)) concentration of 25.04 mg/l was found in airlift bioreactor than the value of 18.11 mg/l obtained in stirred tank under the aerobic-dark cultivation of rhodobacter sphaeroides. aeration rate didn't show obvious impact to coq(10) production in airlift bioreactor. the fed-batch operation in airlift bioreactor could increase the biomass concentration and led to the maximum coq(10) concentration of 33.91 mg/l measured, but a lower coq(10) cell content (3.5 mg coq(10 ... | 2009 | 19153771 |
| profile hidden markov models for analyzing similarities and dissimilarities in the bacterial reaction center and photosystem ii. | the bacterial photosynthetic reaction center is the evolutionary ancestor of the photosystem ii reaction center. these proteins share the same fold and perform the same biological function. nevertheless, the details of their molecular reaction mechanism differ. it is of significant biological and biochemical interest to determine which functional characteristics are conserved at the level of the protein sequences. since the level of sequence identity between the bacterial photosynthetic reaction ... | 2009 | 19159220 |
| identification of ftir bands due to internal water molecules around the quinone binding sites in the reaction center from rhodobacter sphaeroides. | the bacterial reaction center (rc) is a membrane protein complex that performs photosynthetic electron transfer from a bacteriochlorophyll dimer to quinone acceptors q(a) and q(b). q(b) accepts electrons from the primary quinone, q(a), in two sequential electron transfer reactions coupled to uptake of a proton from solution. it has been suggested that water molecules along the proton uptake pathway are protonated upon quinone reduction on the basis of ftir difference spectra [breton, j., and nab ... | 2009 | 19161296 |
| lateral proton transfer between the membrane and a membrane protein. | proton transport across biological membranes is a key step of the energy conservation machinery in living organisms, and it has been proposed that the membrane itself plays an important role in this process. in the present study we have investigated the effect of incorporation of a proton transporter, cytochrome c oxidase, into a membrane on the protonation kinetics of a fluorescent ph-sensitive probe attached at the surface of the protein. the results show that proton transfer to the probe was ... | 2009 | 19166299 |
| different biochemical mechanisms ensure network-wide balancing of reducing equivalents in microbial metabolism. | to sustain growth, the catabolic formation of the redox equivalent nadph must be balanced with the anabolic demand. the mechanisms that ensure such network-wide balancing, however, are presently not understood. based on 13c-detected intracellular fluxes, metabolite concentrations, and cofactor specificities for all relevant central metabolic enzymes, we have quantified catabolic nadph production in agrobacterium tumefaciens, bacillus subtilis, escherichia coli, paracoccus versutus, pseudomonas f ... | 2009 | 19181802 |
| confinement of cardiolipin and ubiquinone in reaction-center core complexes purified from the photosynthetic bacterium rhodobacter sphaeroides. | the core complex formed by the reaction center and the light harvesting complex 1 (rc-lh1) was purified from the photosynthetic bacterium rhodobacter sphaeroides. we analyzed the lipid and ubiquinone (uq) complements copurifying with the rc-lh1 complex and with the peripheral antenna (lh2). in rc-lh1 uq was almost ten times more concentrated than in the lh2 and in the native membranes from which the complexes were extracted. the fractional lipid composition of the rc-lh1 complex also differed fr ... | 2007 | 19192623 |
| [isolation and purification of malate dehydrogenase isoforms from phototrophic purple bacteria rhodobacter sphaeroides and rhodopseudomonas palustris]. | a five-step procedure was used to obtain electrophoretically pure preparations of malate dehydrogenase (ec 1.1.1.37) from rhodobacter sphaeroides and rhodopseudomonas palustris. the procedure included extraction, ammonium sulfate fractionation, gel filtration, and ion exchange and gel permeation chromatography. the enzyme was found to exist in two isoforms, dimeric and tetrameric, formed by the oligomerization of identical subunits. the isoforms are assumed to be involved in different metabolic ... | 2008 | 19198073 |
| kinetics of in vivo bacteriochlorophyll fluorescence yield and the state of photosynthetic apparatus of purple bacteria. | the light-induced electron transport in purple bacterium rhodobacter sphaeroides was studied in vivo by means of kinetic difference absorption spectroscopy and kinetics of bacteriochlorophyll fluorescence yield. measurements of redox state of the oxidised primary donor and cytochrome c and the membrane potential revealed a complex pattern of changes of the electron flow. effects of the membrane potential on the fluorescence yield were also analysed, and a model for the fluorescence induction cur ... | 2009 | 19199074 |
| characterization of d-tagatose-3-epimerase from rhodobacter sphaeroides that converts d-fructose into d-psicose. | a non-characterized gene, previously proposed as the d-tagatose-3-epimerase gene from rhodobacter sphaeroides, was cloned and expressed in escherichia coli. its molecular mass was estimated to be 64 kda with two identical subunits. the enzyme specificity was highest with d-fructose and decreased for other substrates in the order: d-tagatose, d-psicose, d-ribulose, d-xylulose and d-sorbose. its activity was maximal at ph 9 and 40 degrees c while being enhanced by mn(2+). at ph 9 and 40 degrees c, ... | 2009 | 19205890 |
| rna degradation in archaea and gram-negative bacteria different from escherichia coli. | exoribonucleolytic and endoribonucleolytic activities are important for controlled degradation of rna and contribute to the regulation of gene expression at the posttranscriptional level by influencing the half-lives of specific messenger rnas. the rna half-lives are determined by the characteristics of the rna substrates and by the availability and the properties of the involved proteins-ribonucleases and assisting polypeptides. much is known about rna degradation in eukarya and bacteria, but t ... | 2009 | 19215775 |
| a mitochondrial dna mutation linked to colon cancer results in proton leaks in cytochrome c oxidase. | an increasing number of cancer types have been found to be linked to specific mutations in the mitochondrial dna, which result in specific structural changes of the respiratory enzyme complexes. in this study, we have investigated the effect of 2 such mutations identified in colon cancer patients, leading to the amino acid substitutions ser458pro and gly125asp in subunit i of cytochrome c oxidase (complex iv) [greaves et al. (2006) proc natl acad sci usa 103:714-719]. we introduced these mutatio ... | 2009 | 19218458 |
| mutant reaction centers of rhodobacter sphaeroides i(l177)h with strongly bound bacteriochlorophyll a: structural properties and pigment-protein interactions. | methods of photoinduced fourier transform infrared (ftir) difference spectroscopy and circular dichroism were employed for studying features of pigment-protein interactions caused by replacement of isoleucine l177 by histidine in the reaction center (rc) of the site-directed mutant i(l177)h of rhodobacter sphaeroides. a functional state of pigments in the photochemically active cofactor branch was evaluated with the method of photo-accumulation of reduced bacteriopheophytin h(a)(-). the results ... | 2009 | 19232051 |
| microscopic pka analysis of glu286 in cytochrome c oxidase (rhodobacter sphaeroides): toward a calibrated molecular model. | as stringent tests for the molecular model and computational protocol, microscopic pk(a) calculations are performed for the key residue, glu286, in cytochrome c oxidase (cco) using a combined quantum mechanical/molecular mechanical (qm/mm) potential and a thermodynamic integration protocol. the impact of the number of water molecules in the hydrophobic cavity and protonation state of several key residues (e.g., his334, cu(b)-bound water, and prd(a3)) on the computed microscopic pk(a) values of g ... | 2009 | 19243111 |
| trapping the p+b(l)- initial intermediate state of charge separation in photosynthetic reaction centers from rhodobacter capsulatus. | the short-lived (<1 ps) initial intermediate state p(+)b(l)(-) in the photoinduced charge separation process of the bacterial photosynthetic reaction center has been trapped in two d(ll)-based rhodobacter capsulatus mutants that have tyr at position m208 and lack the bacteriopheophytin electron acceptor h(l). transient state p(+)b(l)(-) is characterized by a 1017 nm bacteriochlorophyll anion absorption band and decays by charge recombination with a lifetime of several hundred picoseconds at 295 ... | 2009 | 19245209 |
| relaxation mechanism of molecular systems containing hydrogen bonds and free energy temperature dependence of reaction of charges recombination within rhodobacter sphaeroides rc. | the mechanism of protonic relaxation is shown to take place in molecular systems containing hydrogen bonds. the mechanism arises from the proton redistribution between two stable states on hydrogen bond lines. this redistribution occurs due to changes of hydrogen bond double well potential, brought about by changes of the electronic state of a molecular system. a characteristic of the relaxation process is that it takes place due to the proton tunneling along hydrogen bonds. the charge shift cau ... | 2009 | 19247510 |
| functional hydration and conformational gating of proton uptake in cytochrome c oxidase. | cytochrome c oxidase couples the reduction of dioxygen to proton pumping against an electrochemical gradient. the d-channel, a 25-a-long cavity, provides the principal pathway for the uptake of chemical and pumped protons. a water chain is thought to mediate the relay of protons via a grotthuss mechanism through the d-channel, but it is interrupted at n139 in all available crystallographic structures. we use free-energy simulations to examine the proton uptake pathway in the wild type and in sin ... | 2009 | 19248790 |
| active site of cytochrome cbb3. | cytochrome cbb(3) is the most distant member of the heme-copper oxidase family still retaining the following major feature typical of these enzymes: reduction of molecular oxygen to water coupled to proton translocation across the membrane. the thermodynamic properties of the six redox centers, five hemes and a copper ion, in cytochrome cbb(3) from rhodobacter sphaeroides were studied using optical and epr spectroscopy. the low spin heme b in the catalytic subunit was shown to have the highest m ... | 2009 | 19252222 |
| across membrane communication between the q(o) and q(i) active sites of cytochrome bc(1). | the ubihydroquinone:cytochrome c oxidoreductase (cyt bc(1)) contains two catalytically active domains, termed the hydroquinone oxidation (q(o)) and quinone reduction (q(i)) sites, which are distant from each other by over 30 a. previously, we have reported that binding of inhibitors to the q(i) site on one (n) side of the energy-transducing membrane changes the local environment of the iron-sulfur (fe/s) protein subunit residing in the q(o) site on the other (p) side of the lipid bilayer [cooley ... | 2009 | 19254042 |
| atomic force microscopy studies of native photosynthetic membranes. | in addition to providing the earliest surface images of a native photosynthetic membrane at submolecular resolution, examination of the intracytoplasmic membrane (icm) of purple bacteria by atomic force microscopy (afm) has revealed a wide diversity of species-dependent arrangements of closely packed light-harvesting (lh) antennae, capable of fulfilling the basic requirements for efficient collection, transmission, and trapping of radiant energy. a highly organized architecture was observed with ... | 2009 | 19265434 |
| cultivation of rhodobacter sphaeroides in the stirred bioreactor with different feeding strategies for coq(10) production. | the logistic growth model combined with the luedeking-piret equation was adopted in this study to model the batch production of coq(10) in the cultivation of rhodobacter sphaeroides. the simulation results indicated that coq(10) production was a primary metabolite. as being a primary metabolite, a longer cell growing stage would tend to accumulate more biomass and lead to a higher coq(10) concentration being produced. in this context, a fed-batch operation by molasses feeding was performed to in ... | 2010 | 19277486 |
| proton-transfer pathways in photosynthetic reaction centers analyzed by profile hidden markov models and network calculations. | in the bacterial reaction center (brc) of rhodobacter sphaeroides, the key residues of proton transfer to the secondary quinone (q(b)) are known. also, several possible proton entry points and proton-transfer pathways have been proposed. however, the mechanism of the proton transfer to q(b) remains unclear. the proton transfer to q(b) in the brc of blastochloris viridis is less explored. to analyze whether the brcs of different species use the same key residues for proton transfer to q(b), we de ... | 2009 | 19285988 |
| the petite purple photosynthetic powerpack. | photoreaction centres are nature's solar batteries. these nanometre-scale power producers are responsible for transducing the energy of sunlight into a form that can be used by biological systems, thereby powering most of the biological activity on the planet. although to the layman the word 'photosynthesis' is usually associated with green plants, much of our understanding of the molecular basis of biological transduction of light energy has come from studies of purple photosynthetic bacteria. ... | 2009 | 19290870 |
| the local electric field within phospholipid membranes modulates the charge transfer reactions in reaction centres. | three different cholesterol derivatives and phloretin, known to affect the local electric field in phospholipid membranes, have been introduced into rhodobacter sphaeroides reaction centre-containing phospholipid liposomes. we show that cholesterol and 6-ketocholestanol significantly slow down the interquinone first electron transfer (approximately 10 times), whereas phloretin and 5-cholesten-3beta-ol-7-one leave the kinetics essentially unchanged. interestingly, the two former compounds have be ... | 2009 | 19306840 |
| development of a dynamic delivery method for in vitro bioassays. | measuring the biological activity of hydrophobic chemicals using in vitro assays is challenging because their aqueous solubility is low and the high density of bio-suspensions strongly decreases the bioavailability of hydrophobic pollutants. dynamic dosing by partitioning from a stable polymer has a potential to overcome these limitations. poly(dimethylsiloxane) (pdms) was chosen due to its documented bio-compatibility and excellent partitioning properties. pdms sheets were loaded with five poly ... | 2009 | 19324392 |
| [enzymes of the citramalate cycle in rhodospirillum rubrum]. | rhodospirillum rubrum is among the bacteria that can assimilate acetate in the absence of isocitrate lyase, the key enzyme of glyoxylate shunt. previously we have suggested the functioning of a new anaplerotic cycle of acetate assimilation in this bacterium: citramalate cycle, where acetyl-coa is oxidized to glyoxylate. this work has demonstrated the presence of all the key enzymes of this cycle in r. rubrum extracts: citramalate synthase catalyzing condensation of acetyl-coa and pyruvate with t ... | 2009 | 19334594 |
| lipopolysaccharide from rhodobacter capsulatus suppresses the effect of endotoxins from various e. coli chemotypes on the priming and apoptosis of human neutrophils. | | 2009 | 19341104 |
| internal charge transfer in cytochrome c oxidase at a limited proton supply: proton pumping ceases at high ph. | in the membrane-bound enzyme cytochrome c oxidase, electron transfer from cytochrome c to o(2) is linked to proton uptake from solution to form h(2)o, resulting in a charge separation across the membrane. in addition, the reaction drives pumping of protons across the membrane. | 2009 | 19344748 |
| effect of subunit iv on superoxide generation by rhodobacter sphaeroides cytochrome bc(1) complex. | previous studies indicate that the three-subunit cytochrome bc(1) core complex of rhodobacter sphaeroides contains a fraction of the electron transfer activity of the wild-type enzyme. addition of subunit iv to the core complex increases electron transfer activity to the same level as that of the wild-type complex. this activity increase may result from subunit iv preventing electron leakage, from the low potential electron transfer chain, and reaction with molecular oxygen, producing superoxide ... | 2009 | 19348783 |
| laterally mobile, functionalized self-assembled monolayers at the fluorous-aqueous interface in a plug-based microfluidic system: characterization and testing with membrane protein crystallization. | this paper describes a method to generate functionalizable, mobile self-assembled monolayers (sams) in plug-based microfluidics. control of interfaces is advancing studies of biological interfaces, heterogeneous reactions, and nanotechnology. sams have been useful for such studies, but they are not laterally mobile. lipid-based methods, though mobile, are not easily amenable to setting up the hundreds of experiments necessary for crystallization screening. here we demonstrate a method, complemen ... | 2009 | 19354215 |
| static and dynamic protein impact on electronic properties of light-harvesting complex lh2. | a comparative analysis of the temperature dependence of the absorption spectra of the lh2 complexes from different species of photosynthetic bacteria, i.e., rhodobacter sphaeroides, rhodoblastus acidophilus, and phaeospirillum molischianum, was performed in the temperature range from 4 to 300 k. qualitatively, the temperature dependence is similar for all of the species studied. the spectral bandwidths of both b800 and b850 bands increases with temperature while the band positions shift in oppos ... | 2008 | 19367872 |
| identification of the binding site of the {sigma}54 hetero-oligomeric fleq/flet activator in the flagellar promoters of rhodobacter sphaeroides. | expression of the flagellar genes in rhodobacter sphaeroides is dependent on one of the four sigma-54 factors present in this bacterium and on the enhancer binding proteins (ebps) fleq and flet. these proteins, in contrast to other well-characterized ebps, carry out activation as a hetero-oligomeric complex. to further characterize the molecular properties of this complex we mapped the binding sites or upstream activation sequences (uass) of six different flagellar promoters. in most cases the u ... | 2009 | 19372156 |
| in vivo analysis of cobinamide salvaging in rhodobacter sphaeroides strain 2.4.1. | the genome of rhodobacter sphaeroides encodes the components of two distinct pathways for salvaging cobinamide (cbi), a precursor of adenosylcobalamin (adocbl, coenzyme b(12)). one pathway, conserved among bacteria, depends on a bifunctional kinase/guanylyltransferase (cobp) enzyme to convert adenosylcobinamide (adocbi) to adocbi-phosphate (adocbi-p), an intermediate in de novo adocbl biosynthesis. the other pathway, of archaeal origin, depends on an adocbi amidohydrolase (cbiz) enzyme to genera ... | 2009 | 19376876 |
| comparative metagenomics of daphnia symbionts. | shotgun sequences of dna extracts from whole organisms allow a comprehensive assessment of possible symbionts. the current project makes use of four shotgun datasets from three species of the planktonic freshwater crustaceans daphnia: one dataset from clones of d. pulex and d. pulicaria and two datasets from one clone of d. magna. we analyzed these datasets with three aims: first, we search for bacterial symbionts, which are present in all three species. second, we search for evidence for cyanob ... | 2009 | 19383155 |