| probing biological interfaces by tracing proton passage across them. | the properties of water at the surface, especially at an electrically charged one, differ essentially from those in the bulk phase. here we survey the traits of surface water as inferred from proton pulse experiments with membrane enzymes. in such experiments, protons that are ejected (or captured) by light-triggered enzymes are traced on their way between the membrane surface and the bulk aqueous phase. in several laboratories it has been shown that proton exchange between the membrane surface ... | 2006 | 16761086 |
| new multichannel kinetic spectrophotometer-fluorimeter with pulsed measuring beam for photosynthesis research. | a multichannel kinetic spectrophotometer-fluorimeter with pulsed measuring beam and differential optics has been constructed for measurements of light-induced absorbance and fluorescence yield changes in isolated chlorophyll-proteins, thylakoids and intact cells including algae and photosynthetic bacteria. the measuring beam, provided by a short (2 micros) pulse from a xenon flash lamp, is divided into a sample and reference channel by a broad band beam splitter. the spectrum in each channel is ... | 2006 | 16763876 |
| modulation of proton pumping efficiency in bacterial atp synthases. | the atp synthase in chromatophores of rhodobacter caspulatus can effectively generate a transmembrane ph difference coupled to the hydrolysis of atp. the rate of hydrolysis was rather insensitive to the depletion of adp in the assay medium by an atp regenerating system (phospho-enol-pyruvate (pep) and pyruvate kinase (pk)). the steady state values of deltaph were however drastically reduced as a consequence of adp depletion. the clamped concentrations of adp obtained using different pk activitie ... | 2006 | 16765908 |
| ftir-spectral analysis of two photosynthetic hydrogen-producing [corrected] strains and their extracellular polymeric substances. | the fourier transform infrared (ftir) spectra of the cells of two photosynthetic h(2)-producing strains, rhodoblastus acidophilus and rhodobacter capsulatus, as well as their extracellular polymeric substances (eps), were evaluated. the ftir spectra of r. capsulatus and its eps during its cultivation were also recorded. the main peaks in the spectra, including 1,080 cm(-1) (carbohydrates), 1,250 cm(-1) (nucleic acids), 2,830-2,930 cm(-1) (lipids), 1,660-1,535 cm(-1) (amide i and ii of proteins), ... | 2006 | 16767463 |
| characterization of a mutant strain of rhodovulum sulfidophilum lacking the pufa and pufb genes encoding the polypeptides for the light-harvesting complex 1 (b 870). | contradictory results on the effectiveness of energy transfer from the light harvesting complex 2 (lh2) directly to the reaction center (rc) in mutant strains lacking the core light-harvesting complex 1 (lh1) have been obtained with cells of rhodobacter capsulatus and rhodobacter sphaeroides. a lh1(-) mutant of rhodovulum sulfidophilum, named rslri, was constructed by deletion of the pufba genes, resulting in a kanamycin resistant photosynthetically positive clone. to restore the wild type pheno ... | 2006 | 16775747 |
| interactions between nitrate assimilation and 2,4-dinitrophenol cometabolism in rhodobacter capsulatus e1f1. | the phototrophic, nitrate-photoassimilating bacterium rhodobacter capsulatus e1f1 cometabolizes 2,4-dinitrophenol (dnp) by photoreducing it to 2-amino-4-nitrophenol under anaerobic conditions. dnp uptake and nitrate metabolism share some biochemical features, and in this article we show that both processes are influenced by each other. thus, as was demonstrated for nitrate assimilation, dnp uptake requires a thermolabile periplasmic component. nitrate assimilation is inhibited by dnp, which prob ... | 2006 | 16775785 |
| proton in the well and through the desolvation barrier. | the concept of the membrane proton well was suggested by peter mitchell to account for the energetic equivalence of the chemical (deltaph) and electrical (deltapsi) components of the proton-motive force. the proton well was defined as a proton-conducting crevice passing down into the membrane dielectric and able to accumulate protons in response to the generation either of deltapsi or of deltaph. in this review, the concept of proton well is contrasted to the desolvation penalty of > 500 mev for ... | 2006 | 16780789 |
| a functional hybrid between the cytochrome bc1 complex and its physiological membrane-anchored electron acceptor cytochrome cy in rhodobacter capsulatus. | the membrane integral ubihydroquinone (qh2): cytochrome (cyt) c oxidoreductase (or the cyt bc1 complex) and its physiological electron acceptor, the membrane-anchored cytochrome cy (cyt cy), are discrete components of photosynthetic and respiratory electron transport chains of purple non-sulfur, facultative phototrophic bacteria of rhodobacter species. in rhodobacter capsulatus, it has been observed previously that, depending on the growth condition, absence of the cyt bc1 complex is often corre ... | 2006 | 16781662 |
| activation of the global gene regulator prra (rega) from rhodobacter sphaeroides. | prra is a global transcription regulator activated upon phosphorylation by its cognate kinase prrb in response to low oxygen levels in rhodobacter sphaeroides. here we show by gel filtration, analytical ultracentrifugation, and nmr diffusion measurements that treatment of prra with a phosphate analogue, bef(3)(-), results in dimerization of the protein, producing a protein that binds dna. no dimeric species was observed in the absence of bef(3)(-). upon addition of bef(3)(-), the inhibitory acti ... | 2006 | 16784239 |
| in situ kinetics of cytochromes c1 and c2. | in rhodobacter sphaeroides chromatophores, cytochromes (cyt) c(1) and c(2) have closely overlapping spectra, and their spectral deconvolution provides a challenging task. as a result, analyses of the kinetics of different cytochrome components of the bc(1) complex in purple bacteria usually report only the sum cyt c(1) + cyt c(2) kinetics. here we used newly determined difference spectra of individual components to resolve the kinetics of cyt c(1) and c(2) in situ via a least-squares (ls) deconv ... | 2006 | 16784242 |
| biological synthesis of semiconductor zinc sulfide nanoparticles by immobilized rhodobacter sphaeroides. | a novel, clean biological transformation reaction by immobilized rhodobacter sphaeroides has been developed for the synthesis of zinc sulfide (zns) nanoparticles with an average diameter of 8 nm. the nanoparticles were examined by x-ray diffraction, transmission electron microscopy, energy dispersive analyses of x-rays, uv-vis optical absorption and photoluminescence spectra. the average diameter of zns nanoparticles varied according to the culture time. | 2006 | 16794769 |
| calculated proton uptake on anaerobic reduction of cytochrome c oxidase: is the reaction electroneutral? | cytochrome c oxidase is a transmembrane proton pump that builds an electrochemical gradient using chemical energy from the reduction of o(2). ionization states of all residues were calculated with multi-conformation continuum electrostatics (mcce) in seven anaerobic oxidase redox states ranging from fully oxidized to fully reduced. one long-standing problem is how proton uptake is coupled to the reduction of the active site binuclear center (bnc). the bnc has two cofactors: heme a(3) and cu(b). ... | 2006 | 16800622 |
| inhibition of proton pumping by zinc ions during specific reaction steps in cytochrome c oxidase. | cytochrome c oxidase (cytco) is a redox-driven proton pump in the respiratory chain of mitochondria and many aerobic bacteria. the results from several studies have shown that zinc ions interfere with both the uptake and release of protons, presumably by binding near the orifice of the proton entrance and exit pathways. to elucidate the effect of zn2+ binding on individual electron and proton-transfer reactions, in this study, we have investigated the reaction of the fully reduced r. sphaeroides ... | 2006 | 16806055 |
| free energy profiles for h+ conduction in the d-pathway of cytochrome c oxidase: a study of the wild type and n98d mutant enzymes. | the molecular mechanism for proton conduction in the d-pathway of cytochrome c oxidase (cco) is investigated through the free energy profile, i.e., potential of mean force (pmf) calculations of both the native enzyme and the n98d mutant. the multistate empirical valence bond (ms-evb) model was applied to simulate the interaction of an excess proton with the channel environment. in the study of the wild type enzyme, the pmf reveals the previously proposed proton trap inside the channel; it also s ... | 2006 | 16815239 |
| the brucella abortus cyclic beta-1,2-glucan virulence factor is substituted with o-ester-linked succinyl residues. | brucella periplasmic cyclic beta-1,2-glucan plays an important role during bacterium-host interaction. nuclear magnetic resonance spectrometry analysis, thin-layer chromatography, and deae-sephadex chromatography were used to characterize brucella abortus cyclic glucan. in the present study, we report that a fraction of b. abortus cyclic beta-1,2-glucan is substituted with succinyl residues, which confer anionic character on the cyclic beta-1,2-glucan. the oligosaccharide backbone is substituted ... | 2006 | 16816173 |
| surface proton donors for the d-pathway of cytochrome c oxidase in the absence of subunit iii. | the major proton-transfer pathway into the buried active site of cytochrome c oxidase (cco) is the d-pathway that begins with the subunit i residue asp-132 on the inner protein surface (the cytoplasmic surface of the aa3-type cco of rhodobacter sphaeroides). asp-132 is surrounded by residues from both subunits i and iii. in the absence of subunit iii, cco retains activity, but the functional characteristics of the d-pathway are significantly altered such that the transfer of protons from asp-132 ... | 2006 | 16819830 |
| effect of mutations of five conserved histidine residues in the catalytic subunit of the cbb3 cytochrome c oxidase on its function. | the cbb3 cytochrome c oxidase has the dual function as a terminal oxidase and oxygen sensor in the photosynthetic bacterium, rhodobacter sphaeroides. the cbb3 oxidase forms a signal transduction pathway together with the prrba two-component system that controls photosynthesis gene expression in response to changes in oxygen tension in the environment. under aerobic conditions the cbb3 oxidase generates an inhibitory signal, which shifts the equilibrium of prrb kinase/phosphatase activities towar ... | 2006 | 16820758 |
| comparison of aerobic and photosynthetic rhodobacter sphaeroides 2.4.1 proteomes. | the analysis of proteomes from aerobic and photosynthetic rhodobacter sphaeroides 2.4.1 cell cultures by liquid chromatography-mass spectrometry yielded approximately 6,500 high confidence peptides representing 1,675 gene products (39% of the predicted proteins). the identified proteins corresponded primarily to open reading frames (orfs) contained within the two chromosomal elements of this bacterium, but a significant number were also observed from orfs associated with 5 naturally occurring pl ... | 2006 | 16828186 |
| generation, characterization and crystallization of a highly active and stable cytochrome bc1 complex mutant from rhodobacter sphaeroides. | the availability of the three dimensional structure of mitochondrial enzyme, obtained by x-ray crystallography, allowed a significant progress in the understanding of the structure-function relation of the cytochrome bc(1) complex. most of the structural information obtained has been confirmed by molecular genetic studies of the bacterial complex. despite its small size and simple subunit composition, high quality crystals of the bacterial complex have been difficult to obtain and so far, only l ... | 2006 | 16828701 |
| vibrational coherence in bacterial reaction centers with genetically modified b-branch pigment composition. | femtosecond absorption difference spectroscopy was applied to study the time and spectral evolution of low-temperature (90 k) absorbance changes in isolated reaction centers (rcs) of the hm182l mutant of rhodobacter (rb.) sphaeroides. in this mutant, the composition of the b-branch rc cofactors is modified with respect to that of wild-type rcs by replacing the photochemically inactive bb accessory bacteriochlorophyll (bchl) by a photoreducible bacteriopheophytin molecule (referred to as phib). w ... | 2006 | 16829225 |
| testing the photosynthetic bacterium rhodobacter sphaeroides as heavy metal removal tool. | we present some preliminary results relevant to the ability of the purple non-sulphur bacterium rhodobacter sphaeroides strain r26.1 to sequester heavy metals from contaminated growth media. the microorganism was chosen because of its significant tolerance to relatively high concentrations of the investigated ions ni2+, co2+, cro4(2-), and moo4(2-). in this paper the optimized conditions for the bacterial growth and the sample preparation used to infer the ability of the microorganism to cope wi ... | 2006 | 16836253 |
| scanning electrochemical microscopy of the photosynthetic reaction center of rhodobacter sphaeroides in different environmental systems. | the present work uses a scanning electrochemical microscopy technique to study systems containing the membrane-bound reaction center protein (rc) from the purple photosynthetic bacteria rhodobacter spheroides to chromatophores (spherical reorganization of cell membrane following its mechanical rupture) and liposomes (reconstituted membrane systems at lower degree of complexity). scanning electrochemical microscopy is a useful tool to investigate redox processes involving a rc, because the effect ... | 2006 | 16841928 |
| low-frequency resonance raman studies of the h(m202)g cavity mutant of bacterial photosynthetic reaction centers. | low-frequency (90-435 cm(-1)) nir-excitation (875-900 nm) resonance raman (rr) studies are reported for the h(m202)g cavity mutant of bacterial photosynthetic reaction centers (rcs) from rb. sphaeroides that was first described by goldsmith et al. [(1996) biochemistry 35: 2421-2428]. in this mutant, the his residue that axially ligates the mg ion of the m-side bacteriochlorophyll (bchl) of the special pair primary donor (p) is replaced by a non-ligating gly residue. regardless, the mg ion of p(m ... | 2006 | 16847742 |
| interacting specificity of a histidine kinase and its cognate response regulator: the prrba system of rhodobacter sphaeroides. | using a yeast two-hybrid assay system, it was demonstrated that the four-helix bundle of the rhodobacter sphaeroides prrb histidine kinase both serves as the interaction site for the regulatory domain of its cognate response regulator prra and is the primary determinant of the interaction specificity. the alpha-helix 1 and its flanking turn region within the dimerization domain (dd) of the prrb histidine kinase appear to play an important role in conferring the recognition specificity for the pr ... | 2006 | 16849810 |
| interference, fluctuation, and alternation of electron tunneling in protein media. 1. two tunneling routes in photosynthetic reaction center alternate due to thermal fluctuation of protein conformation. | electron tunneling routes for the electron transfer from the bacteriopheophytin anion to the primary quinone in the bacterial photosynthetic reaction center of rhodobactor sphaeroides are investigated by a combined method of molecular dynamics simulations for the protein conformation fluctuation and quantum chemical calculations for the electronic states of the donor, acceptor, and protein medium. the analysis of the tunneling route is made by mapping interatomic electron tunneling currents for ... | 2005 | 16851182 |
| simulation of electron transfer between cytochrome c2 and the bacterial photosynthetic reaction center: brownian dynamics analysis of the native proteins and double mutants. | electron transfer is essential for bacterial photosynthesis which converts light energy into chemical energy. this paper theoretically studies the interprotein electron transfer from cytochrome c(2) of rhodobacter capsulatus to the photosynthetic reaction center of rhodobacter sphaeroides in native and mutated systems. brownian dynamics is used with an exponential distance-dependent electron-transfer rate model to compute bimolecular rate constants, which are consistent with experimental data wh ... | 2005 | 16851864 |
| "glass transition" near 200 k in the bacterial photosynthetic reaction center protein detected by studying the distances in the transient p+q(a)- radical pair. | the transient radical pair p(+)q(a)(-) in the photosynthetic reaction center from rhodobacter sphaeroides r26 was studied over a wide temperature range using out-of-phase electron spin-echo envelope modulation (eseem) spectroscopy. this method is sensitive to the magnetic dipole-dipole interaction between the two electron spins of the pair and allows precise determination of the distance in the pair p(+)q(a)(-). the out-of-phase data were complemented by normal in-phase eseem spectra from the tw ... | 2005 | 16851865 |
| light-induced structural changes in the active site of the bluf domain in appa by raman spectroscopy. | the flavin-adenine-dinucleotide-binding bluf domain constitutes a new class of blue-light receptors, and the n-terminal domain of appa is a representative of this family. appa functions as a transcriptional antirepressor, controlling the photosynthesis gene expression in the purple bacterium rhodobacter sphaeroides. upon light absorption, appa undergoes a photocycle with a signaling state, which exhibits an approximately 10 nm red shift in the uv-vis absorption spectrum. we have characterized li ... | 2005 | 16852561 |
| interference, fluctuation, and alternation of electron tunneling in protein media. 2. non-condon theory for the energy gap dependence of electron transfer rate. | developing the quantum transition rate theory of prezhdo and rossky (j. chem. phys. 1997, 107, 5863), we produced a new non-condon theory of the rate of electron transfer (et) which happens through a protein medium with conformational fluctuation. the new theory is expressed by a convolution form of the power spectrum for the autocorrelation function of the electronic tunneling matrix element t(da)(t) with quantum correction and the ordinary franck-condon factor. the new theory satisfies the det ... | 2005 | 16852980 |
| electron transfer in the reaction center of the rb. sphaeroides r-26 studied by transient absorption. | electron transfer at the reaction center of the purple photosynthetic bacterium rb. sphaeroides r-26 was measured at room temperature by the time-resolved transient absorption spectroscopy technique with 200 fs temporal resolution. the absorbance changes characteristic of the excited state of the primary donor and extending over the whole spectral range investigated from 350 nm up to 720 nm appeared after excitation with a laser pulse of about 100 fs duration at 800 nm. the time evolution of the ... | 2005 | 16853333 |
| environmental control of primary photochemistry in a mutant bacterial reaction center. | the core structure of the photosynthetic reaction center is quasisymmetric with two potential pathways (called a and b) for transmembrane electron transfer. both the pathway and products of light-induced charge separation depend on local electrostatic interactions and the nature of the excited states generated at early times in reaction centers isolated from rhodobacter sphaeroides. here transient absorbance measurements were recorded following specific excitation of the q(y)() transitions of p ... | 2005 | 16853576 |
| influence of cardiolipin on the functionality of the q(a) site of the photosynthetic bacterial reaction center. | the effect of cardiolipin on the functionality of the q(a) site of a photosynthetic reaction center (rc) was studied in rcs from the purple non-sulfur bacterium rhodobacter sphaeroides by means of time-resolved absorbance measurements. the binding of the ubiquinone-10 to the q(a) site of the rc embedded in cardiolipin or lecithin liposomes has been followed at different temperatures and phospholipid loading. a global fit of the experimental data allowed us to get quite reliable values of the the ... | 2005 | 16853745 |
| acidity of a cu-bound histidine in the binuclear center of cytochrome c oxidase. | cytochrome c oxidase (cco) is a crucial enzyme in the respiratory chain. its function is to couple the reduction of molecular oxygen, which takes place in the fea3-cub binuclear center, to proton translocation across the mitochondrial membrane. although several high-resolution structures of the enzyme are known, the molecular basis of proton pumping activation and its mechanism remain to be elucidated. we examine a recently proposed scheme (j. am. chem. soc. 2004, 126, 1858; febs lett. 2004, 566 ... | 2005 | 16853946 |
| identification of hydrogen bonds to the rieske cluster through the weakly coupled nitrogens detected by electron spin echo envelope modulation spectroscopy. | the interaction of the reduced[2fe-2s] cluster of isolated rieske fragment from the bc1 complex of rhodobacter sphaeroides with nitrogens (14n and 15n) from the local protein environment has been studied by x- and s-band pulsed epr spectroscopy. the two-dimensional electron spin echo envelope modulation spectra of uniformly 15n-labeled protein show two well resolved cross-peaks with weak couplings of approximately 0.3-0.4 and 1.1 mhz in addition to couplings in the range of 6-8 mhz from two coor ... | 2006 | 16854984 |
| transcriptional specificity of rpon1 and rpon2 involves differential recognition of the promoter sequences and specific interaction with the cognate activator proteins. | the four rpon factors of rhodobacter sphaeroides are functionally specialized. in this bacterium, rpon1 and rpon2 are specifically required for the transcription of the nitrogen fixation and flagellar genes, respectively. analysis of the promoter sequences recognized by each of these rpon proteins revealed some significant differences. to investigate the functional relevance of these differences, the flagellar promoter fliop was sequentially mutagenized to resemble the nitrogen fixation promoter ... | 2006 | 16854992 |
| study of an alternate glyoxylate cycle for acetate assimilation by rhodobacter sphaeroides. | organisms, which grow on organic substrates that are metabolized via acetyl-coa, are faced with the problem to form all cell constituents from this c(2)-unit. the problem was solved by the seminal work of kornberg and is known as the glyoxylate cycle. however, many bacteria are known to not contain isocitrate lyase, the key enzyme of this pathway. this problem was addressed in acetate-grown rhodobacter sphaeroides. an acetate-minus mutant identified by transposon mutagenesis was affected in the ... | 2006 | 16856937 |
| ornithine lipid is required for optimal steady-state amounts of c-type cytochromes in rhodobacter capsulatus. | the c-type cytochromes are haemoproteins that are subunits or physiological partners of electron transport chain components, like the cytochrome bc(1) complex or the cbb(3)-type cytochrome c oxidase. their haem moieties are covalently attached to the corresponding apocytochromes via a complex post-translational maturation process. during our studies of cytochrome biogenesis, we uncovered a novel class of mutants that are unable to produce ornithine lipid and that lack several c-type cytochromes. ... | 2006 | 16856942 |
| local electrostatic field induced by the carotenoid bound to the reaction center of the purple photosynthetic bacterium rhodobacter sphaeroides. | electroabsorption (ea) spectra were recorded in the region of the reaction center (rc) qy absorption bands of bacteriochlorophyll (bchl) and bacteriopheophytin, to investigate the effect of carotenoid (car) on the electrostatic environment of the rcs of the purple bacterium rhodobacter (rb.) sphaeroides. two different rcs were prepared from rb. sphaeroides strain r26.1 (r26.1-rc); r26.1 rc lacking car and a reconstituted rc (r26.1-rc+ car) prepared by incorporating a synthetic car (3,4-dihydrosp ... | 2005 | 16866471 |
| the first catalytic step of the light-driven enzyme protochlorophyllide oxidoreductase proceeds via a charge transfer complex. | in chlorophyll biosynthesis protochlorophyllide reductase (por) catalyzes the light-driven reduction of protochlorophyllide (pchlide) to chlorophyllide, providing a rare opportunity to trap and characterize catalytic intermediates at low temperatures. moreover, the presence of a chlorophyll-like molecule allows the use of epr, electron nuclear double resonance, and stark spectroscopies, previously used for the analysis of photosynthetic systems, to follow catalytic events in the active site of p ... | 2006 | 16867988 |
| local stability of rhodobacter capsulatus cytochrome c2 probed by solution phase hydrogen/deuterium exchange and mass spectrometry. | the hydrogen/deuterium exchange kinetics of rhodobacter capsulatus cytochrome c2 have been determined using mass spectrometry. as expected, the relative domain stability was generally similar to that of the cytochrome c2 structural homolog, horse heart cytochrome c, but we were able to find evidence to support the presence of a second, small beta-sheet not found in the horse cytochrome, which stabilizes a structural region dominated by omega loops. importantly, we find that the so-called hinge r ... | 2006 | 16872833 |
| resonance raman characterization of archaeal and bacterial rieske protein variants with modified hydrogen bond network around the [2fe-2s] center. | the rate of quinol oxidation by cytochrome bc(1)/b(6)f complex is in part associated with the redox potential (e(m)) of its rieske [2fe-2s] center, for which an approximate correlation with the number of hydrogen bonds to the cluster has been proposed. here we report comparative resonance raman (rr) characterization of bacterial and archaeal high-potential rieske proteins and their site-directed variants with a modified hydrogen bond network around the cluster. major differences among their rr s ... | 2006 | 16877714 |
| mechanism of carotenoid singlet excited state energy transfer in modified bacterial reaction centers. | ultrafast transient laser spectroscopy has been used to investigate carotenoid singlet excited state energy transfer in various rhodobacter (rb.) sphaeroides reaction centers (rcs) modified either genetically or chemically. the pathway and efficiency of energy transfer were examined as a function of the structures and energies of the donor and acceptor molecules. on the donor side, carotenoids with various extents of pi-electron conjugation were examined. rcs studied include those from the anaer ... | 2006 | 16884279 |
| activity of rhodobacter sphaeroides rpohii, a second member of the heat shock sigma factor family. | we have identified a second rpoh homolog, rpoh(ii), in the alpha-proteobacterium rhodobacter sphaeroides. primary amino acid sequence comparisons demonstrate that r. sphaeroides rpoh(ii) belongs to a phylogenetically distinct group with rpoh orthologs from alpha-proteobacteria that contain two rpoh genes. like its previously identified paralog, rpoh(i), rpoh(ii) is able to complement the temperature-sensitive phenotype of an escherichia coli sigma(32) (rpoh) mutant. in addition, we show that rec ... | 2006 | 16885439 |
| application of the accurate mass and time tag approach to the proteome analysis of sub-cellular fractions obtained from rhodobacter sphaeroides 2.4.1. aerobic and photosynthetic cell cultures. | the high-throughput accurate mass and time (amt) tag proteomic approach was utilized to characterize the proteomes for cytoplasm, cytoplasmic membrane, periplasm, and outer membrane fractions from aerobic and photosynthetic cultures of the gram-nagtive bacterium rhodobacter sphaeroides 2.4.1. in addition, we analyzed the proteins within purified chromatophore fractions that house the photosynthetic apparatus from photosynthetically grown cells. in total, 8,300 peptides were identified with high ... | 2006 | 16889416 |
| identification of amino acid residues essential for reconstitutive activity of subunit iv of the cytochrome bc1 complex from rhodobacter sphaeroides. | a region of subunit iv comprising residues 77-85 is identified as essential for interaction with the core complex to restore the bc(1) activity (reconstitutive activity). recombinant subunit iv mutants with single or multiple alanine substitution at this region were generated and characterized to identify the essential amino acid residues. residues 81-84, with sequence of yryr, are required for reconstitutive activity of subunit iv, because a mutant with these four residues substituted with alan ... | 2006 | 16890186 |
| mutations which decouple the proton pump of the cytochrome c oxidase from rhodobacter sphaeroides perturb the environment of glutamate 286. | mutants that decouple the proton pump of cytochrome c oxidase from rhodobacter sphaeroides are postulated to do so by increasing the pk(a) of glutamate 286, which is 20 angstrom away. the possibility that a conformational change near e286 is induced by the decoupling mutations (n139d and n207d) was investigated by ftir difference spectroscopy. in both decoupled mutants, the reduced-minus-oxidized ftir difference spectra show a shift of 2 cm(-1) to lower frequency of the band resulting from the a ... | 2006 | 16890226 |
| biochemical characterization of the decaprenyl diphosphate synthase of rhodobacter sphaeroides for coenzyme q10 production. | coenzyme q(10) (coq(10)), like other coqs of various organisms, plays indispensable roles not only in energy generation but also in several other processes required for cells' survival. in this study, a gene encoding for a decaprenyl diphosphate synthase (rsdds) was cloned from rhodobacter sphaeroides in escherichia coli. the in vivo catalytic activity and product specificity of rsdds were compared with those of a counterpart enzyme from agrobacterium tumefaciens (atdds) in e. coli as a heterolo ... | 2006 | 16896603 |
| expression and characterization of the assimilatory nadh-nitrite reductase from the phototrophic bacterium rhodobacter capsulatus e1f1. | a nas gene region from rhodobacter capsulatus e1f1 containing the putative nasb gene for nitrite reductase was previously cloned. the recombinant his(6)-nasb protein overproduced in e. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and nadh as electron donors. the apparent k ( m ) values for nitrite and nadh were 0.5 mm and 20 microm, respectively, at the ph and temperature optima (ph 9 and 30 degrees c). the optical spectrum showed features that indicate the p ... | 2006 | 16897035 |
| identification of acetate- or methanol-assimilating bacteria under nitrate-reducing conditions by stable-isotope probing. | stable-isotope probing (sip) was used to identify acetate- or methanol-assimilating bacteria under nitrate-reducing conditions in activated sludge. a sludge sample obtained from wastewater treatment systems was incubated in a denitrifying batch reactor fed with synthetic wastewater containing [(13)c]acetate or [(13)c]methanol as the main carbon source and nitrate as the electron acceptor. we analyzed how growth of bacterial populations was stimulated by acetate or methanol as the external carbon ... | 2006 | 16897304 |
| a specific and versatile genome walking technique. | we describe here a nested pcr-based strategy for genome walking to extend a known sequence region to its uncharacterized flanking regions. this technique involves the use of a partially degenerate primer as a walker primer and a set of nested specific primers to perform two to three successive rounds of nested pcr. to increase the success rate of genome walking, four different walker primers were designed to allow the setup of parallel reactions. this technique was applied to amplify flanking se ... | 2006 | 16914272 |
| redox properties of the rhodobacter sphaeroides transcriptional regulatory proteins ppsr and appa. | redox properties of the photosynthetic gene repressor ppsr and the blue-light photoreceptor/antirepressor appa from rhodobacter sphaeroides have been characterized. redox titrations of ppsr reveal the presence of a two-electron couple, with an e (m) value of -320 mv at ph 7.0, which is likely to arise from the reversible conversion of two cysteine thiols to a disulfide. this e (m) value is very much more negative than the e (m) = -180 mv value measured previously at ph 7.0 for the disulfide/dith ... | 2006 | 16915353 |
| expression of the trxc gene of rhodobacter capsulatus: response to cellular redox status is mediated by the transcriptional regulator oxyr. | despite the importance of thioredoxins in cellular functions, little is known about the regulation of trx genes. to understand the molecular mechanisms involved in the regulation of the rhodobacter capsulatus trxc gene, the expression of this gene was investigated. we describe oxyr-dependent redox regulation of the trxc gene that adjusts the levels of thioredoxins in the cell. | 2006 | 16916895 |
| surface-modulated motion switch: capture and release of iron-sulfur protein in the cytochrome bc1 complex. | in the cytochrome bc(1) complex, the swivel motion of the iron-sulfur protein (isp) between two redox sites constitutes a key component of the mechanism that achieves the separation of the two electrons in a substrate molecule at the quinol oxidation (q(o)) site. the question remaining is how the motion of isp is controlled so that only one electron enters the thermodynamically favorable chain via isp. an analysis of eight structures of mitochondrial bc(1) with bound q(o) site inhibitors reveale ... | 2006 | 16924113 |
| atpase activity associated with the magnesium chelatase h-subunit of the chlorophyll biosynthetic pathway is an artefact. | magnesium chelatase inserts mg2+ into protoporphyrin ix and is the first unique enzyme of the chlorophyll biosynthetic pathway. it is a heterotrimeric enzyme, composed of i- (40 kda), d- (70 kda) and h- (140 kda) subunits. the i- and d-proteins belong to the family of aaa+ (atpases associated with various cellular activities), but only i-subunit hydrolyses atp to adp. the d-subunits provide a platform for the assembly of the i-subunits, which results in a two-tiered hexameric ring complex. howev ... | 2006 | 16928192 |
| single-electron photoreduction of the p(m) intermediate of cytochrome c oxidase. | the p(m)-->f transition of the catalytic cycle of cytochrome c oxidase from bovine heart was investigated using single-electron photoreduction and monitoring the subsequent events using spectroscopic and electometric techniques. the p(m) state of the oxidase was generated by exposing the oxidized enzyme to co plus o2. photoreduction results in rapid electron transfer from heme a to oxoferryl heme a3 with a time constant of about 0.3 ms, as indicated by transients at 605 nm and 580 nm. this rate ... | 2006 | 16938268 |
| role of the pewy glutamate in hydroquinone-quinone oxidation-reduction catalysis in the qo site of cytochrome bc1. | the glutamic acid residue of the conserved pewy motif of the q(o) site of cytochrome bc(1) is widely discussed as central to reversible q(o) site catalysis of two-electron, two-proton hydroquinone-quinone oxidation-reduction. extensive mutation of this glutamate (e295) to a, v, f, h, k, and q in purple photosynthetic rhodobacter capsulatus results in hydroquinone oxidation rates that are between 5 and 50-fold slower than that in the wild type. however, the mutants show little or no detectable ef ... | 2006 | 16939201 |
| functional and structural analysis of the photosynthetic apparatus of rhodobacter veldkampii. | in the widely studied purple bacterium rhodobacter sphaeroides, a small transmembrane protein, named pufx, is required for photosynthetic growth and is involved in the supramolecular dimeric organization of the core complex. we performed a structural and functional analysis of the photosynthetic apparatus of rhodobacter veldkampii, a related species which evolved independently. time-resolved optical spectroscopy of r. veldkampii chromatophores showed that the reaction center shares with r. sphae ... | 2006 | 16939203 |
| biotransformation of isoeugenol to vanillin by pseudomonas putida ie27 cells. | the ability to produce vanillin and/or vanillic acid from isoeugenol was screened using resting cells of various bacteria. the vanillin- and/or vanillic-acid-producing activities were observed in strains belonging to the genera achromobacter, aeromonas, agrobacerium, alcaligenes, arthrobacter, bacillus, micrococcus, pseudomonas, rhodobacter, and rhodococcus. strain ie27, a soil isolate showing the highest vanillin-producing activity, was identified as pseudomonas putida. we optimized the culture ... | 2007 | 16944125 |
| the photosynthetic deficiency due to puhc gene deletion in rhodobacter capsulatus suggests a puhc protein-dependent process of rc/lh1/pufx complex reorganization. | optimal photosynthetic reaction centre (rc) and core antenna (lh1) levels in the purple bacterium rhodobacter capsulatus require the puhc gene. deletion of puhc had little effect on rc and lh1 assembly individually, but significantly inhibited the photosynthetic growth of rc+ lh1- strains, suggesting that maximal rc catalytic activity is puhc-dependent. consistent with post-assembly reorganization of the rc/lh1/pufx core complex by puhc to include latecomer proteins, spatial separation of pufx f ... | 2006 | 16949540 |
| crystal structures of the appa bluf domain photoreceptor provide insights into blue light-mediated signal transduction. | proteins containing a sensor of blue light using fad (bluf) domain control diverse cellular processes, such as gene expression, nucleotide metabolism and motility, by relaying blue light signals to distinct output units. despite its crucial and widespread functions, the mechanism of bluf signal transduction has remained elusive. we determined crystal structures of the dark-adapted state and of a photo-excited, red-shifted photocycle intermediate of the bluf unit of appa, a purple bacterial photo ... | 2006 | 16949615 |
| the cheys of rhodobacter sphaeroides. | the escherichia coli two-component chemosensory pathway has been extensively studied, and its response regulator, chey, has become a paradigm for response regulators. however, unlike e. coli, most chemotactic nonenteric bacteria have multiple chey homologues. the roles and cellular localization of the cheys in rhodobacter sphaeroides were determined. only two cheys were required for chemotaxis, chey(6) and either chey(3) or chey(4). these cheys were partially localized to either of the two chemo ... | 2006 | 16950782 |
| characterization of phototrophic purple nonsulfur bacteria forming colored microbial mats in a swine wastewater ditch. | the community structure of pink-colored microbial mats naturally occurring in a swine wastewater ditch was studied by culture-independent biomarker and molecular methods as well as by conventional cultivation methods. the wastewater in the ditch contained acetate and propionate as the major carbon nutrients. thin-section electron microscopy revealed that the microbial mats were dominated by rod-shaped cells containing intracytoplasmic membranes of the lamellar type. smaller numbers of oval cells ... | 2006 | 16957249 |
| controlling light-use by rhodobacter capsulatus continuous cultures in a flat-panel photobioreactor. | the main bottleneck in scale-up of phototrophic fermentation is the low efficiency of light energy conversion to the desired product, which is caused by an excessive dissipation of light energy to heat. the photoheterotrophic formation of hydrogen from acetate and light energy by the microorganism rhodobacter capsulatus ncimb 11773 was chosen as a case study in this work. a light energy balance was set up, in which the total bacterial light energy absorption is split up and attributed to its des ... | 2006 | 16958141 |
| lipids in photosynthetic reaction centres: structural roles and functional holes. | photosynthetic proteins power the biosphere. reaction centres, light harvesting antenna proteins and cytochrome b(6)f (or bc(1)) complexes are expressed at high levels, have been subjected to an intensive spectroscopic, biochemical and mutagenic analysis, and several have been characterised to an informatively high resolution by x-ray crystallography. in addition to revealing the structural basis for the transduction of light energy, x-ray crystallography has brought molecular insights into the ... | 2007 | 16963124 |
| two chemosensory operons of rhodobacter sphaeroides are regulated independently by sigma 28 and sigma 54. | rhodobacter sphaeroides has a complex chemosensory system, with several loci encoding multiple homologues of the components required for chemosensing in escherichia coli. the operons cheop2 and cheop3 each encode complete pathways, and both are essential for chemosensing. the components of cheop2 are predominantly localized to the cell pole, whereas those encoded by cheop3 are predominantly targeted to a discrete cluster in the cytoplasm. here we show that the expression of the two pathways is r ... | 2006 | 16963577 |
| the role of an extra fragment of cytochrome b (residues 309-326) in the cytochrome bc1 complex from rhodobacter sphaeroides. | in bacterial cytochrome b of the cytochrome bc(1) complex, there is an extra fragment located between the amphipathic helix ef and the transmembrane helix f compared to the mitochondrial counterparts. in this work, mutants at various positions of this extra fragment were generated in rhodobacter sphaeroides in an effort to investigate its specific role in the bacterial bc(1) complex. the total deletion [cytb-delta(309-326)] and alanine substitution [cytb-(309-326)a] mutant complexes have about 2 ... | 2006 | 16964973 |
| immunobiological activities of a new nontoxic lipopolysaccharide from acidiphilium gs18h/atcc55963, a soil isolate from an indian copper mine. | a novel nontoxic lipopolysaccharide (lps) was purified from acidiphilium strain gs18h/atcc55963. the chemical composition of the lipid a part of this lps is distinctly different from that of known lipid a molecules. the lps was investigated to determine its capacity to provide protection against toxic lps or endotoxic shock, as has been reported for other nontoxic lpss (rhodobacter sphaeroides and rhodobacter capsulatus), and also the extent and type of immunomodulatory response in terms of tumo ... | 2006 | 16965358 |
| optimization of activation conditions of rhodobacter sphaeroides in hydrogen generation process. | to examine the effects of the culture age, illuminance intensity and changes in these parameters during activation on hydrogen generation process carried out by purple nonsulfur rhodobacter sphaeroides bacteria. | 2006 | 16968289 |
| an unorthodox bacteriophytochrome from rhodobacter sphaeroides involved in turnover of the second messenger c-di-gmp. | bacteriophytochromes are bacterial photoreceptors that sense red/far red light using the biliverdin chromophore. most bacteriophytochromes work as photoactivated protein kinases. the rhodobacter sphaeroides bacteriophytochrome bphg1 is unconventional in that it has ggdef and eal output domains, which are involved, respectively, in synthesis (diguanylate cyclase) and degradation (phosphodiesterase) of the bacterial second messenger c-di-gmp. the ggdef-eal proteins studied to date displayed either ... | 2006 | 16968704 |
| charge delocalization in the special-pair radical cation of mutant reaction centers of rhodobacter sphaeroides from stark spectra and nonadiabatic spectral simulations. | stark and absorption spectra for the hole-transfer band of the bacteriochlorophyll special pair in the wild-type and l131lh, m160lh, and l131lh/m160lh mutants of the bacterial reaction center of rhodobacter sphaeroides are presented, along with extensive analyses based on nonadiabatic spectral simulations. dramatic changes in the stark spectra are induced by the mutations, changes that are readily interpreted in terms of the redox-energy asymmetry and degree of charge localization in the special ... | 2006 | 16970500 |
| conservation and variation between rhodobacter capsulatus and escherichia coli tat systems. | the tat system allows the translocation of folded and often cofactor-containing proteins across biological membranes. here, we show by an interspecies transfer of a complete tat translocon that tat systems are largely, but not fully, interchangeable even between different classes of proteobacteria. the tat apparatus from the alpha-proteobacterium rhodobacter capsulatus was transferred to a tat-deficient escherichia coli strain, which is a gamma-proteobacterium. similar to that of e. coli, the r. ... | 2006 | 16980457 |
| channeling in sulfate activating complexes. | the synthesis of activated sulfate (adenosine 5'-phosphosulfate, aps) and inorganic pyrophosphate from atp and so4 is remarkably unfavorable: k(eq) approximately 10(-8) under presumed, near-physiological conditions. consequently, atp sulfurylases, which catalyze aps synthesis, suffer approximately 10(8)-fold losses in catalytic efficiency in the forward (aps-synthesis) versus reverse reaction. losses of this magnitude place this catalyst at risk of being unable to supply its nutrients to the cel ... | 2006 | 16981690 |
| toll-like receptor 4 signalling is neither sufficient nor required for oxidised phospholipid mediated induction of interleukin-8 expression. | toll-like receptor (tlr)-4 signalling has been shown to accelerate atherosclerosis. as oxidised phospholipids are present in atherosclerotic plaque and have been shown to modulate tlr4 signalling, we investigated the role of oxidised 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (oxpapc) in the regulation of tlr 1, 2, 4 and 6 signalling. | 2007 | 16982060 |
| photo-cidnp mas nmr in intact cells of rhodobacter sphaeroides r26: molecular and atomic resolution at nanomolar concentration. | photochemically induced dynamic nuclear polarization (photo-cidnp) is observed in photosynthetic reaction centers of the carotenoid-less strain r26 of the purple bacterium rhodobacter sphaeroides by (13)c solid-state nmr at three different magnetic fields (4.7, 9.4, and 17.6 t). the signals of the donor appear enhanced absorptive (positive) and of the acceptor emissive (negative). this spectral feature is in contrast to photo-cidnp data of reactions centers of rhodobacter sphaeroides wildtype re ... | 2006 | 17002374 |
| lipidic sponge phase crystallization of membrane proteins. | bicontinuous lipidic cubic phases can be used as a host for growing crystals of membrane proteins. since the cubic phase is stiff, handling is difficult and time-consuming. moreover, the conventional cubic phase may interfere with the hydrophilic domains of membrane proteins due to the limited size of the aqueous pores. here, we introduce a new crystallization method that makes use of a liquid analogue of the cubic phase, the sponge phase. this phase facilitates a considerable increase in the al ... | 2006 | 17005199 |
| using unnatural protein fusions to engineer resveratrol biosynthesis in yeast and mammalian cells. | resveratrol is a naturally occurring defense compound produced by a limited number of plants in response to stresses. besides cardiovascular benefits, this health-promoting compound has been reported to extend life spans in yeasts, flies, worms, and fish. to biosynthesize resveratrol de novo, tyrosine ammonia lyase (tal), 4-coumarate coa-ligase (4cl), and stilbene synthase (sts) were isolated from rhodobacter sphaeroides, arabidopsis thaliana, and vitis vinifera, respectively. yeast cells expres ... | 2006 | 17017764 |
| epr-endor of the cu(i)no complex of nitrite reductase. | with limited reductant and nitrite under anaerobic conditions, copper-containing nitrite reductase (nir) of rhodobacter sphaeroides yielded endogenous no and the cu(i)no derivative of nir. (14)n- and (15)n-nitrite substrates gave rise to characteristic (14)no and (15)no epr hyperfine features indicating no involvement, and enrichment of nir with (63)cu isotope caused an epr line shape change showing copper involvement. a markedly similar cu(i)nonir complex was made by anaerobically adding a litt ... | 2006 | 17017790 |
| mapping protein dynamics in catalytic intermediates of the redox-driven proton pump cytochrome c oxidase. | redox-driven proton pumps such as cytochrome c oxidase (cco) are fundamental elements of the energy transduction machinery in biological systems. cco is an integral membrane protein that acts as the terminal electron acceptor in respiratory chains of aerobic organisms, catalyzing the four-electron reduction of o2 to h2o. this reduction also requires four protons taken from the cytosolic or negative side of the membrane, with an additional uptake of four protons that are pumped across the membran ... | 2006 | 17023543 |
| selection of photosynthetic bacterium rhodobacter sphaeroides 14f for polyhydroxyalkanoate production with two-stage aerobic dark cultivation. | polyhydroxyalkanoate (pha) production abilities in a two-stage aerobic dark culture of photosynthetic bacteria were investigated at relatively high temperatures (37-40 degrees c). a 14f strain, identified as rhodobacter sphaeroides, showed the highest pha production (3.5 g/l pha with 60% pha content). its productivity was 2-3 times higher than those of other photosynthetic bacteria. | 2006 | 17027875 |
| possible pathway for ubiquinone shuttling in rhodospirillum rubrum revealed by molecular dynamics simulation. | in the last decade, the structures of many components of the photosynthetic apparatus of purple bacteria, as well as the mutual organization of these components within the purple membrane, were resolved. one key question that emerged concerned the assembly of the core complex consisting of the reaction center (rc) and the light-harvesting 1 (lh1) complex. in some species, like rhodobacter sphaeroides, the ring-shaped lh1 complex was found to be open, whereas other species, like rhodospirillum ru ... | 2007 | 17028136 |
| overlapping and specialized functions of the molybdenum-dependent regulators mopa and mopb in rhodobacter capsulatus. | the phototrophic purple bacterium rhodobacter capsulatus encodes two similar but functionally not identical molybdenum-dependent regulator proteins (mopa and mopb), which are known to replace each other in repression of the modabc genes (coding for an abc-type high-affinity mo transport system) and anfa (coding for the transcriptional activator of fe-nitrogenase genes). we identified further mo-regulated (mor) genes coding for a putative abc-type transport system of unknown function (morabc) and ... | 2006 | 17028278 |
| effects of cadmium stress on growth, morphology, and protein expression in rhodobacter capsulatus b10. | the effects of cadmium stress on growth, morphology, and protein expression were investigated in rhodobacter capsulatus b10 using two-dimensional polyacrylamide gel electrophoresis and a scanning electron microscope with an energy dispersive x-ray spectrometer. the bacterium grew in the presence of 150 microm cdcl2 and highly induced heat-shock proteins (groel and dnak), s-adenosylmethionine synthetase, ribosomal protein s1, aspartate aminotransferase, and phosphoglycerate kinase. interestingly, ... | 2006 | 17031048 |
| site-specific conversion of cysteine thiols into thiocyanate creates an ir probe for electric fields in proteins. | the nitrile stretching mode of the thiocyanate moiety is a nearly ideal probe for measuring the local electric field arising from the organized environment of the interior of a protein. nitriles were introduced into three proteins: ribonuclease s (rnase s), human aldose reductase (halr2), and the reaction center (rc) of rhodobacter capsulatus, through a facile synthetic scheme for the transformation of cysteine residues into thiocyanatoalanine. vibrational stark effect spectroscopy and fourier t ... | 2006 | 17031938 |
| new detection method for hydrogen gas for screening hydrogen-producing microorganisms using water-soluble wilkinson's catalyst derivative. | a water-soluble color indicator was developed for the effective screening of hydrogen-producing microorganisms. this indicator consists of a coloring agent and a water-soluble derivative of wilkinson's catalyst. wilkinson's catalyst, tris(triphenylphosphine) rhodium chloride, had been developed as a catalyst for the hydrogenation of olefins. we used a sulfonate of the catalyst for the hydrogenation of coloring agent in an aqueous medium. several coloring agents, such as methyl orange, methyl red ... | 2006 | 17046537 |
| identification of conserved lipid/detergent-binding sites in a high-resolution structure of the membrane protein cytochrome c oxidase. | well ordered reproducible crystals of cytochrome c oxidase (cco) from rhodobacter sphaeroides yield a previously unreported structure at 2.0 a resolution that contains the two catalytic subunits and a number of alkyl chains of lipids and detergents. comparison with crystal structures of other bacterial and mammalian ccos reveals that the positions occupied by native membrane lipids and detergent substitutes are highly conserved, along with amino acid residues in their vicinity, suggesting a more ... | 2006 | 17050688 |
| development of the bacterial photosynthetic apparatus. | anoxygenic photosynthetic bacteria have provided us with crucial insights into the process of solar energy capture, pathways of metabolic and societal importance, specialized differentiation of membrane domains, function or assembly of bioenergetic enzymes, and into the genetic control of these and other activities. recent insights into the organization of this bioenergetic membrane system, the genetic control of this specialized domain of the inner membrane and the process by which potentially ... | 2006 | 17055774 |
| phylogenetic diversity and activity of aerobic heterotrophic bacteria from a hypersaline oil-polluted microbial mat. | the diversity and function of aerobic heterotrophic bacteria (ahb) in cyanobacterial mats have been largely overlooked. we used culture-dependent and molecular techniques to explore the species diversity, degradative capacities and functional guilds of ahb in the photic layer (2mm) of an oil-polluted microbial mat from saudi arabia. enrichment isolation was carried out at different salinities (5% and 12%) and temperatures (28 and 45 degrees c) and on various substrates (acetate, glycolate, spiru ... | 2007 | 17056222 |
| identification of a histidine-tyrosine cross-link in the active site of the cbb3-type cytochrome c oxidase from rhodobacter sphaeroides. | the heme-copper oxidases constitute a superfamily of terminal dioxygen-reducing enzymes located in the inner mitochondrial or in the bacterial cell membrane. the presence of a mechanistically important covalent bond between a histidine ligand of the copper ion (cu(b)) in the active site and a generally conserved tyrosine residue nearby has been shown to exist in the canonical cytochrome c oxidases. however, according to sequence alignment studies, this critical tyrosine is missing from the subfa ... | 2006 | 17060620 |
| stabilization effect of single-walled carbon nanotubes on the functioning of photosynthetic reaction centers. | the interaction between single-walled carbon nanotubes and photosynthetic reaction centers purified from purple bacterium rhodobacter sphaeroides r-26 has been investigated. atomic force microscopy studies provide evidence that reaction center protein can be attached effectively to the nanotubes. the typical diameter of the nanotube is 1-4 nm and 15 +/- 2 nm without and with the reaction centers, respectively. light-induced absorption change measurements indicate the stabilization of the p+(q(a) ... | 2006 | 17064097 |
| nitrogenase fe protein-like fe-s cluster is conserved in l-protein (bchl) of dark-operative protochlorophyllide reductase from rhodobacter capsulatus. | dark-operative protochlorophyllide reductase (dpor) in bacteriochlorophyll biosynthesis is a nitrogenase-like enzyme consisting of l-protein (bchl-dimer) as a reductase component and nb-protein (bchn-bchb-heterotetramer) as a catalytic component. metallocenters of dpor have not been identified. here we report that l-protein has an oxygen-sensitive [4fe-4s] cluster similar to nitrogenase fe protein. purified l-protein from rhodobacter capsulatus showed absorption spectra and an electron paramagne ... | 2006 | 17064695 |
| protein-cofactor interactions in bacterial reaction centers from rhodobacter sphaeroides r-26: ii. geometry of the hydrogen bonds to the primary quinone formula by 1h and 2h endor spectroscopy. | the geometry of the hydrogen bonds to the two carbonyl oxygens of the semiquinone q(a)(. -) in the reaction center (rc) from the photosynthetic purple bacterium rhodobacter sphaeroides r-26 were determined by fitting a spin hamiltonian to the data derived from (1)h and (2)h endor spectroscopies at 35 ghz and 80 k. the experiments were performed on rcs in which the native fe(2+) (high spin) was replaced by diamagnetic zn(2+) to prevent spectral line broadening of the q(a)(. -) due to magnetic cou ... | 2007 | 17071655 |
| genome-enabled analysis of the utilization of taurine as sole source of carbon or of nitrogen by rhodobacter sphaeroides 2.4.1. | a degradative pathway for taurine (2-aminoethanesulfonate) in rhodobacter sphaeroides 2.4.1 was proposed by brüggemann et al. (2004) (microbiology 150, 805-816) on the basis of a partial genome sequence. in the present study, r. sphaeroides 2.4.1 was found to grow exponentially with taurine as the sole source of carbon and energy for growth. when taurine was the sole source of nitrogen in succinate-salts medium, the taurine was rapidly degraded, and most of the organic nitrogen was excreted as t ... | 2006 | 17074891 |
| the thiol:disulfide oxidoreductase dsbb mediates the oxidizing effects of the toxic metalloid tellurite (teo32-) on the plasma membrane redox system of the facultative phototroph rhodobacter capsulatus. | the highly toxic oxyanion tellurite (teo3(2-)) is a well known pro-oxidant in mammalian and bacterial cells. this work examines the effects of tellurite on the redox state of the electron transport chain of the facultative phototroph rhodobacter capsulatus, in relation to the role of the thiol:disulfide oxidoreductase dsbb. under steady-state respiration, the addition of tellurite (2.5 mm) to membrane fragments generated an extrareduction of the cytochrome pool (c- and b-type hemes); further, in ... | 2007 | 17098900 |
| proton uptake in the reaction center mutant l210dn from rhodobacter sphaeroides via protonated water molecules. | the reaction center (rc) of rhodobacter sphaeroides uses light energy to reduce and protonate a quinone molecule, qb (the secondary quinone electron acceptor), to form quinol, qbh2. asp210 in the l-subunit has been shown to be a catalytic residue in this process. mutation of asp210 to asn leads to a deceleration of reoxidation of qa- in the qa-qb --> qaqb- transition. here we determined the structure of the asp210 to asn mutant to 2.5 a and show that there are no major structural differences as ... | 2006 | 17105193 |
| trapped conformational states of semiquinone (d+*qb-*) formed by b-branch electron transfer at low temperature in rhodobacter sphaeroides reaction centers. | the reaction center (rc) from rhodobacter sphaeroides captures light energy by electron transfer between quinones qa and qb, involving a conformational gating step. in this work, conformational states of d+*qb-* were trapped (80 k) and studied using epr spectroscopy in native and mutant rcs that lack qa in which qb was reduced by the bacteriopheophytin along the b-branch. in mutant rcs frozen in the dark, a light induced epr signal due to d+*qb-* formed in 30% of the sample with low quantum yiel ... | 2006 | 17115698 |
| replacing asn207 by aspartate at the neck of the d channel in the aa3-type cytochrome c oxidase from rhodobacter sphaeroides results in decoupling the proton pump. | cytochrome oxidase catalyzes the reduction of o2 to water and conserves the considerable free energy available from this reaction in the form of a proton motive force. for each electron, one proton is electrogenically pumped across the membrane. of particular interest is the mechanism by which the proton pump operates. previous studies of the oxidase from rhodobacter sphaeroides have shown that all of the pumped protons enter the enzyme through the d channel and that a point mutant, n139d, in th ... | 2006 | 17115701 |
| light-induced flipping of a conserved glutamine sidechain and its orientation in the appa bluf domain. | the appa bluf domain is a blue light photoreceptor containing flavin. conserved glutamine 63 is necessary for the photocycle of the protein, and its side chain has been proposed to flip in response to blue light illumination. recently published crystal structures of appa wt and the appa mutant c20s describe contradictory conclusions regarding the orientation of the conserved glutamine 63 side chain in the dark. here, we present evidence from nmr spectroscopy confirming light-induced flipping of ... | 2006 | 17117839 |
| membrane-spanning and periplasmic segments of ccmi have distinct functions during cytochrome c biogenesis in rhodobacter capsulatus. | in gram-negative bacteria, like rhodobacter capsulatus, about 10 membrane-bound components (ccmabcdefghi and ccda) are required for periplasmic maturation of c-type cytochromes. these components perform the chaperoning and thio-oxidoreduction of the apoproteins as well as the delivery and ligation of the heme cofactors. in the absence of any of these components, including ccmi, proposed to act as an apocytochrome c chaperone, r. capsulatus does not have the ability to produce holocytochromes c o ... | 2007 | 17122341 |
| carotenoid radical cation formation in lh2 of purple bacteria: a quantum chemical study. | in lh2 complexes of rhodobacter sphaeroides the formation of a carotenoid radical cation has recently been observed upon photoexcitation of the carotenoid s2 state. to shed more light onto the yet unknown molecular mechanism leading to carotenoid radical formation in lh2, the interactions between carotenoid and bacteriochlorophyll in lh2 are investigated by means of quantum chemical calculations for three different carotenoids--neurosporene, spheroidene, and spheroidenone--using time-dependent d ... | 2006 | 17125392 |
| resilience of rhodobacter sphaeroides cytochrome bc1 to heme c1 ligation changes. | typically, c hemes are bound to the protein through two thioether bonds to cysteines and two axial ligands to the heme iron. in high-potential class i c-type cytochromes, these axial ligands are commonly his-met. a change in this methionine axial ligand is often correlated with a dramatic drop in the heme redox potential and loss of function. here we describe a bacterial cytochrome c with an unusual tolerance to the alternations in the heme ligation pattern. substitution of the heme ligating met ... | 2006 | 17128964 |