| crystal structures of an oxygen-binding cytochrome c from rhodobacter sphaeroides. | the photosynthetic bacterium rhodobacter sphaeroides produces a heme protein (shp), which is an unusual c-type cytochrome capable of transiently binding oxygen during autooxidation. similar proteins have not only been observed in other photosynthetic bacteria but also in the obligate methylotroph methylophilus methylotrophus and the metal reducing bacterium shewanella putrefaciens. a three-dimensional structure of shp was derived using the multiple isomorphous replacement phasing method. besides ... | 2000 | 10821858 |
| effects of acid ph and urea on the spectral properties of the lhii antenna complex from the photosynthetic bacterium ectothiorhodospira sp. | the aim of this study was to investigate the spectral modifications of the lhii antenna complex from the purple bacterium ectothiorhodospira sp. upon acid ph titration both in the presence and absence of urea. a blue shift specifically and reversibly affected the b850 band around ph 5.5-6.0 suggesting that a histidine residue most probably participated in the in vivo absorption red shifting mechanism. this transition was observed in the presence and absence of urea. under strong chaotropic condi ... | 2000 | 10824108 |
| disruption of a gene essential for sulfoquinovosyldiacylglycerol biosynthesis in sinorhizobium meliloti has no detectable effect on root nodule symbiosis. | the sulfolipid sulfoquinovosyldiacylglycerol is commonly found in the thylakoid membranes of photosynthetic bacteria and plants. while there is a good correlation between the occurrence of sulfolipid and photosynthesis, a number of exceptions are known. most recently, sulfoquinovosyldiacylglycerol was discovered in the non-photosynthetic, root nodule-forming bacterium sinorhizobium meliloti. this discovery raised the questions of the phylogenetic origin of genes essential for the biosynthesis of ... | 2000 | 10830266 |
| dimethylsulfoxide reductase: an enzyme capable of catalysis with either molybdenum or tungsten at the active site. | dmso reductase (dmsor) from rhodobacter capsulatus, well-characterised as a molybdoenzyme, will bind tungsten. protein crystallography has shown that tungsten in w-dmsor is ligated by the dithiolene group of the two pyranopterins, the oxygen atom of ser147 plus another oxygen atom, and is located in a very similar site to that of molybdenum in mo-dmsor. these conclusions are consistent with w l(iii)-edge x-ray absorption, epr and uv/visible spectroscopic data. w-dmsor is significantly more activ ... | 2000 | 10835270 |
| anaerobic chlorophyll isocyclic ring formation in rhodobacter capsulatus requires a cobalamin cofactor. | the isocyclic ring of bacteriochlorophyll (bchl) is formed by the conversion of mg-protoporphyrin monomethyl ester (mpe) to protochlorophyllide (pchlide). similarities revealed by blast searches with the putative anaerobic mpe-cyclase bche suggested to us that this protein also uses a cobalamin cofactor. we found that vitamin b(12) (b(12))-requiring mutants of the blue and blub genes of rhodobacter capsulatus, grown without b(12), accumulated mg-porphyrins. laser desorption/ionization time-of-fl ... | 2000 | 10841582 |
| localized control of proton transfer through the d-pathway in cytochrome c oxidase: application of the proton-inventory technique. | in the reaction cycle of cytochrome c oxidase from rhodobacter sphaeroides, one of the steps that are coupled to proton pumping, the oxo-ferryl-to-oxidized transition (f --> o), displays a large kinetic deuterium isotope effect of about 7. in this study we have investigated in detail the dependence of the kinetics of this reaction step ¿k(fo)(chi) on the fraction (chi) d(2)o in the enzyme solution (proton-inventory technique). according to a simplified version of the gross-butler equation, from ... | 2000 | 10841765 |
| deletion of the 6-kda subunit affects the activity and yield of the bc1 complex from rhodovulum sulfidophilum. | the cytochrome bc1 complex from rhodovulum sulfidophilum purifies as a four-subunit complex: the cytochrome b, cytochrome c1 and rieske iron-sulphur proteins, which are encoded together in the fbc operon, as well as a 6-kda protein. the gene encoding the 6-kda protein, named fbcs, has been identified. it is located within the sox operon, which encodes the subunits of sarcosine oxidase. the encoded 6-kda protein is very hydrophobic and is predicted to form a single transmembrane helix. it shows n ... | 2000 | 10848994 |
| self-assembling photosynthetic reaction centers on electrodes for current generation. | photosynthetic reaction centers (rcs) made from photosynthetic organisms can be used in solar batteries because their molecules cause light-induced charge separation. we present a simple immobilization system of the intact rcs from rhodobacter sphaeroides on an electrode that uses nickel ligand binding by the hexameric histidine tag on h subunit (hhisrc). the binding constant of hhisrc to the nickel-nitrilotriacetic acid (ni-nta) chip measured with a surface plasmon resonance instrument was 1.6 ... | 2000 | 10849806 |
| effect of light/dark cycle on bacterial hydrogen production by rhodobacter sphaeroides rv. from hour to second range. | hydrogen production by photosynthetic bacteria provides an efficient energy conversion method under low light intensity. however, under strong illumination, such as midday sunlight, the efficiency drops. this prevents the method from being applied industrially. to overcome this problem, we examined a method to thin out the excessive illumination. light was given intermittently to reduce the total energy flux. the on/off ratio was set at 1/1 throughout the study, so that the time average of the l ... | 2000 | 10849809 |
| a new inhibitor of the coq-dependent redox reactions in mitochondria and chromatophores. | the effects of 3,4-dimethoxyphenyl-1-amylketone (dpk) on the coq-dependent stages of the electron transport systems in mitochondria and rhodobacter sphaeroides chromatophores were studied. the two systems contain the complete q-cycle. the sensitivities of the q-cycles of two electron transport systems to antimycin, myxothiazole, and other inhibitors are virtually indistinguishable from one another, but these systems have different coq reduction processes. the dependence of the inhibition extent ... | 2000 | 10851035 |
| cyanobacterial sulfide-quinone reductase: cloning and heterologous expression. | the gene encoding sulfide-quinone reductase (sqr; e.c.1.8.5.'), the enzyme catalyzing the first step of anoxygenic photosynthesis in the filamentous cyanobacterium oscillatoria limnetica, was cloned by use of amino acid sequences of tryptic peptides as well as sequences conserved in the rhodobacter capsulatus sqr and in an open reading frame found in the genome of aquifex aeolicus. sqr activity was also detected in the unicellular cyanobacterium aphanothece halophytica following sulfide inductio ... | 2000 | 10852862 |
| genetic and phenotypic analyses of the rdx locus of rhodobacter sphaeroides 2.4.1. | previously, we reported that rdxb, encoding a likely membrane-bound two [4fe-4s]-containing center, is involved in the aerobic regulation of photosystem gene expression in rhodobacter sphaeroides 2.4.1. to further investigate the role of rdxb as well as other genes of the rdxbhis operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the rdx genes. using both puc and puf operon lacz fusions to monitor photosystem gene expression, under ... | 2000 | 10852880 |
| specific mutagenesis of the rieske iron-sulfur protein in rhodobacter sphaeroides shows that both the thermodynamic gradient and the pk of the oxidized form determine the rate of quinol oxidation by the bc(1) complex. | in the rieske iron-sulfur protein (isp) of the ubiquinol:cytochrome c(2) oxidoreductase (bc(1) complex) of rhodobacter sphaeroides, residue tyr 156 is located close to the iron-sulfur cluster. previous studies of the equivalent residue in both saccharomyces cerevisiae [denke, e., merbitz-zahradnik, t., hatzfeld, o. m., snyder, c. h., link, t. a., and trumpower, b. l. (1998) j. biol. chem. 273, 9085-9093] and paracoccus denitrificans [schroter, t., hatzfeld, o. m., gemeinhardt, s., korn, m., frie ... | 2000 | 10858292 |
| -deltag(ab) and ph dependence of the electron transfer from p(+)q(a)(-)q(b) top(+)q(a)q(b)(-) in rhodobacter sphaeroides reaction centers. | the electron transfer from the reduced primary quinone (q(a)(-)) to the secondary quinone (q(b)) can occur in two phases with a well-characterized 100 micros component (tau(2)) and a faster process occurring in less than 10 micros (tau(1)). the fast reaction is clearly seen when the native ubiquinone-10 at q(a) is replaced with naphthoquinones. the dependence of tau(1) on the free-energy difference between the p(+)q(a)(-)q(b) and p(+)q(a)q(b)(-) states (-) and on the ph was measured using naphth ... | 2000 | 10858293 |
| quinone-dependent delayed fluorescence from the reaction center of photosynthetic bacteria. | millisecond delayed fluorescence from the isolated reaction center of photosynthetic bacteria rhodobacter sphaeroides was measured after single saturating flash excitation and was explained by thermal repopulation of the excited bacteriochlorophyll dimer from lower lying charge separated states. three exponential components (fastest, fast, and slow) were found with lifetimes of 1.5, 102, and 865 ms and quantum yields of 6.4 x 10(-9), 2.2 x 10(-9), and 2.6 x 10(-9) (ph 8.0), respectively. while t ... | 2000 | 10866934 |
| synchrotron radiation diffraction from two-dimensional protein crystals at the air/water interface. | protein structure determination by classical x-ray crystallography requires three-dimensional crystals that are difficult to obtain for most proteins and especially for membrane proteins. an alternative is to grow two-dimensional (2d) crystals by adsorbing proteins to ligand-lipid monolayers at the surface of water. this confined geometry requires only small amounts of material and offers numerous advantages: self-assembly and ordering over micrometer scales is easier to obtain in two dimensions ... | 2000 | 10866975 |
| purification and reconstitution of an integral membrane protein, the photoreaction center of rhodobacter sphaeroides, using synthetic sugar esters. | detergents are indispensable reagents for the extraction and solubilization of integral membrane proteins, but their removal from a reconstituted phospholipid-protein complex is usually desirable. in this paper, we describe a novel method in which the synthetic sugar esters 6-o-octanoyl-beta-d-glucose (og) or 6-o-octanoyl-beta-d-mannose (om) are used as detergents for both the isolation and the rapid reconstitution of the photosynthetic reaction center protein of rhodobacter sphaeroides. followi ... | 2000 | 10868287 |
| [relation between structural-dynamic organization of reaction centers in rhodobacter sphaeroides and picosecond steps of photosynthesis]. | the effect of deuteration, and the addition of glycerol and dimethylsulfoxide on the redox midpoint potential em of bacteriochlorophyll of the special pair ¿pmpl¿, the rate of energy migration from bacteriopheophytin hm to ¿pmpl¿, and electron transfer from ¿pmpl¿ to hl and from hl to quinone qa in reaction centers of rhodobacter sphaeroides was studied. it was shown that h2o-->d2o substitution did not change em of the special pair, while the addition of 70% glycerol and 35% dimethylsulfoxide (v ... | 2000 | 10872058 |
| functional analysis of the clpatpase clpa of brucella suis, and persistence of a knockout mutant in balb/c mice. | the protein clpa belongs to a diverse group of polypeptides named clpatpases, which are highly conserved, and which include several molecular chaperones. in this study the gene encoding the 91 kda protein b-clpa of the facultative intracellular pathogen brucella suis, which showed 70% identity to clpa of rhodobacter blasticus, was identified and sequenced. following heterologous expression in escherichia coli strains sg1126 (deltaclpa) and sg1127 (deltalon deltaclpa), b-clpa replaced the functio ... | 2000 | 10878125 |
| regulation of nitrogenase activity in rhodobacter capsulatus under dark microoxic conditions. | rhodobacter capsulatus modulates its in vivo nitrogenase activity in the light in response to the addition of nh4+ in a variety of ways: with adp-ribosylation of the fe-protein of nitrogenase, with a switch-off response that is independent of adp-ribosylation, and with a "magnitude response." in the light, these responses are differentially shown by cultures that differ in the degree of their nitrogen limitation. here we examined the response of these culture types to the addition of nh4+ under ... | 2000 | 10896216 |
| analysis of rdxa and involvement of additional genes encoding nad(p)h flavin oxidoreductase (frxa) and ferredoxin-like protein (fdxb) in metronidazole resistance of helicobacter pylori. | metronidazole (mtz) is a critical ingredient of modern multidrug therapies for helicobacter pylori infection. mtz resistance reduces the effectiveness of these combinations. although null mutations in a rdxa gene that encodes oxygen-insensitive nad(p)h nitroreductase was reported in mtz-resistant h. pylori, an intact rdxa gene has also been reported in mtz-resistant h. pylori, suggesting that additional mtz resistance mechanisms exist in h. pylori. we explored the nature of mtz resistance among ... | 2000 | 10898687 |
| mechanism of metronidazole resistance in helicobacter pylori: comparison of the rdxa gene sequences in 30 strains. | the rdxa gene of 30 independently isolated helicobacter pylori strains was sequenced. a comparison of the rdxa sequences revealed a higher percentage of amino acid substitutions in the corresponding protein than in other housekeeping genes. out of 122 point mutations, 41 were missense and 4 were nonsense. a resistant strain with a nucleotide insertion in the rdxa sequence was also found. with the exception of the point mutations and the insertion generating a stop signal, no particular nucleotid ... | 2000 | 10898705 |
| coupling ion specificity of chimeras between h(+)- and na(+)-driven motor proteins, motb and pomb, in vibrio polar flagella. | we have shown that a hybrid motor consisting of proton-type rhodobacter sphaeroides mota and sodium-type vibrio: alginolyticus pomb, motx and moty, can work as a sodium-driven motor in vibrio: cells. in this study, we tried to substitute the b subunits, which contain a putative ion-binding site in the transmembrane region. rhodobacter sphaeroides motb did not work with either mota or poma in vibrio cells. therefore, we constructed chimeric proteins (momb), which had n-terminal motb and c-termina ... | 2000 | 10899118 |
| 2-(1,3-dithian-2-yl)benzaldehyde and n-[2-[2-(1,3-dioxan-2-yl)phenoxy]ethyl]phthalimide. | | 2000 | 10902029 |
| toxicity of n-containing heterocyclic aromatic compounds and their utilization for growth by a few purple non-sulfur bacteria. | | 2000 | 10903362 |
| multiple regulators and their interactions in vivo and in vitro with the cbb regulons of rhodobacter capsulatus. | the cbb(i) and cbb(ii) operons encode structural genes which are important for carbon dioxide fixation via the calvin-benson-bassham reductive pentose phosphate pathway in rhodobacter capsulatus. each operon is regulated by cognate lysr-type transcriptional activators, cbbr(i) and cbbr(ii), with the product of the cbbr(i) gene, cbbr(i), able to control its own transcription under some growth conditions. furthermore, cbbr(i) may at least partially regulate the cbb(ii) operon, with significant, ye ... | 2000 | 10903856 |
| comments on identification of a hydrogen bond in the phe-m197-->tyr mutant reaction center of the photosynthetic purple bacterium rhodobacter sphaeroides by x-ray crystallography and ftir spectroscopy (febs 23044). | | 2000 | 10908736 |
| corrigendum to: identification of a hydrogen bond in the phe-m197-->tyr mutant reaction center of the photosynthetic purple bacterium rhodobacter sphaeroides by x-ray crystallography and ftir spectroscopy (febs 23044). | | 2000 | 10908737 |
| trfa-dependent inner membrane-associated plasmid rk2 dna synthesis and association of trfa with membranes of different gram-negative hosts. | trfa, the replication initiator protein of broad-host-range plasmid rk2, was tested for its ability to bind to the membrane of four different gram-negative hosts in addition to escherichia coli: pseudomonas aeruginosa, pseudomonas putida, salmonella enterica serovar typhimurium, and rhodobacter sphaeroides. cells harboring trfa-encoding plasmids were fractionated into soluble, inner membrane, and outer membrane fractions. the fractions were subjected to western blotting, and the blots were probe ... | 2000 | 10913068 |
| electrochromic detection of a coherent component in the formation of the charge pair p(+)h(l)(-) in bacterial reaction centers. | we demonstrate coupling of an intraprotein electron transfer reaction to coherent vibrational motions. the kinetics of charge separation toward the radical pair state p(+)h(l)(-) were studied in reaction centers of rhodobacter sphaeroides at 15 k. the electrochromic shift of the bacteriochlorophyll monomers is the most prominent spectral feature associated with this charge displacement. the newly reported absolute absorption spectrum of the p(+)h(l)(-) state is discussed in terms of this shift. ... | 2000 | 10913241 |
| probing the ubihydroquinone primary energy conversion site in the rhodobacter capsulatus cytochrome bc1 complex. | | 1999 | 10917644 |
| ubiquinone and inhibitor sites in complex i: one, two or three? | | 1999 | 10917651 |
| reduction and protonation of the secondary quinone acceptor of rhodobacter sphaeroides photosynthetic reaction center: kinetic model based on a comparison of wild-type chromatophores with mutants carrying arg-->ile substitution at sites 207 and 217 in the l-subunit. | after the light-induced charge separation in the photosynthetic reaction center (rc) of rhodobacter sphaeroides, the electron reaches, via the tightly bound ubiquinone qa, the loosely bound ubiquinone q(b) after two subsequent flashes of light, q(b) is reduced to ubiquinol q(b)h2, with a semiquinone anion q-(b) formed as an intermediate after the first flash. we studied q(b)h2 formation in chromatophores from rb. sphaeroides mutants that carried arg-->ile substitution at sites 207 and 217 in the ... | 2000 | 10924896 |
| the natural product capsaicin inhibits photosynthetic electron transport at the reducing side of photosystem ii and purple bacterial reaction center: structural details of capsaicin binding. | capsaicin, a natural quinone analog, was found to block electron transport, in both plant photosystem ii (psii) and bacterial reaction center (rc) from rhodobacter sphaeroides, at the qb site. the mode of action of capsaicin was investigated by o2 evolution measurements and fluoresence induction studies in the case of psii, and flash-induced absorbance spectroscopy in the case of the bacterial rc. structural details of capsaicin binding to the bacterial rc complex were determined by x-ray crysta ... | 2000 | 10924900 |
| diphenylene iodonium as an inhibitor for the hydrogenase complex of rhodobacter capsulatus. evidence for two distinct electron donor sites. | the photosynthetic bacterium rhodobacter capsulatus synthesises a membrane-bound [nife] hydrogenase encoded by the h2 uptake hydrogenase (hup)slc structural operon. the hups and hupl genes encode the small and large subunits of hydrogenase, respectively; hupc encodes a membrane electron carrier protein which may be considered as the third subunit of the uptake hydrogenase. in wolinella succinogenes, the hydc gene, homologous to hupc, has been shown to encode a low potential cytochrome b which me ... | 2000 | 10924909 |
| conformational relaxation following reduction of the photoactive bacteriopheophytin in reaction centers from balstochloris viridis. influence of mutations at position m208. | the photochemically trapped bacteriopheophytin (bph) b radical anion in the active branch (phi(*-)a) of reaction centers (rcs) from blastochloris (formerly called rhodopseudomonas) viridis is characterized by 1h-endor as well as optical absorption spectroscopy. the two site-directed mutants yf(m208) and yl(m208), in which tyrosine at position m208 is replaced by phenylalanine and leucine, respectively, are investigated and compared with the wild type. the residue at m208 is in close proximity to ... | 2000 | 10924911 |
| characterisation of a rrhodobacter sphaeroides gene that encodes a product resembling eescherichia coli cytochrome b(561) and r. sphaeroides cytochrome b(562). | analysis of the photoactive yellow protein (pyp) gene region of rhodobacter sphaeroides has revealed the presence of an additional open reading frame, orfd, that had not previously been identified. here we report the location of this new gene and the predicted amino acid sequence of the encoded protein. the translation product resembles a group of small cytochrome b-like proteins, including escherichia coli cytochrome b(561), r. sphaeroides cytochrome b(562), and two new cytochrome b(561)-like p ... | 2000 | 10930745 |
| inverted behavioural responses in wild-type rhodobacter sphaeroides to temporal stimuli. | both aerobically and photosynthetically grown wild-type rhodobacter sphaeroides swarmed through soft nutrient agar. however, individual aerobically and photosynthetically grown tethered cells showed different responses to steps in concentrations of some attractants. photosynthetically grown cells showed little response to a step-up in attractant, but large response to a step-down. aerobically grown cells showed a large but opposite response to a step-up of chemoeffectors such as succinate and as ... | 2000 | 10930755 |
| identification and localization of a methyl-accepting chemotaxis protein in rhodobacter sphaeroides. | genes coding for a classical membrane spanning chemoreceptor (mcpg) and a response regulator (chey4) were identified in a region of rhodobacter sphaeroides dna unlinked to either of the two previously identified chemosensory operons. immunogold electron microscopy had shown that the expression of chemoreceptors in r. sphaeroides varies with growth conditions. using gfp fused to the newly identified mcpg, we examined the targeting of this single methyl-accepting chemotaxis protein (mcp) under dif ... | 2000 | 10931275 |
| in vivo and in vitro analysis of rega response regulator mutants of rhodobacter capsulatus. | in the facultative photosynthetic bacterium rhodobacter capsulatus, the transcription of genes encoding pigment binding proteins is tightly regulated in response to the oxygen partial pressure by the regb/ rega two component system. after a shift from high to low oxygen tension, the response regulator rega enhances transcription of the puf and puc operon coding for the reaction center, light-harvesting complex i (lhi), and lhii proteins. various rega mutant strains were analyzed in this study. i ... | 2000 | 10937438 |
| dna binding of wild type rega protein and its differential effect on the expression of pigment binding proteins in rhodobacter capsulatus. | the transcription of genes encoding pigment binding proteins in the facultative photosynthetic bacterium rhodobacter capsulatus is regulated in response to oxygen partial pressure. previous results identified rega and regb as members of a two component system involved in oxygen dependent synthesis of the photosynthetic apparatus. here we demonstrate that rega differentially controls the transcription of the puf and pucoperons which encode proteins of the lhi and lhii antenna complexes, respectiv ... | 2000 | 10939249 |
| rnase iii processing of intervening sequences found in helix 9 of 23s rrna in the alpha subclass of proteobacteria. | we provide experimental evidence for rnase iii-dependent processing in helix 9 of the 23s rrna as a general feature of many species in the alpha subclass of proteobacteria (alpha-proteobacteria). we investigated 12 rhodobacter, rhizobium, sinorhizobium, rhodopseudomonas, and bartonella strains. the processed region is characterized by the presence of intervening sequences (ivss). the 23s rdna sequences between positions 109 and 205 (escherichia coli numbering) were determined, and potential seco ... | 2000 | 10940010 |
| redox signaling: globalization of gene expression. | here we show that the extent of electron flow through the cbb(3) oxidase of rhodobacter sphaeroides is inversely related to the expression levels of those photosynthesis genes that are under control of the prrba two-component activation system: the greater the electron flow, the stronger the inhibitory signal generated by the cbb(3) oxidase to repress photosynthesis gene expression. using site-directed mutagenesis, we show that intramolecular electron transfer within the cbb(3) oxidase is involv ... | 2000 | 10944106 |
| serine 121 is an essential amino acid for biotin sulfoxide reductase functionality. | rhodobacter sphaeroides f. sp. denitrificans biotin sulfoxide reductase (bsor) catalyzes the reduction of d-biotin d-sulfoxide (bso) to biotin, an important step in oxidized vitamin salvaging. in addition to bso, the enzyme also catalyzes the reduction of a variety of other substrates, including methionine sulfoxide, with decreased efficiencies, suggesting a potential role as a general cell protector against oxidative damage. recombinant bsor, expressed as a glutathione s-transferase fusion prot ... | 2000 | 10948204 |
| analysis of the expression of the rhodobacter sphaeroides lexa gene. | the regulation of the rhodobacter sphaeroides lexa gene has been analyzed using both gel-mobility experiments and lacz gene fusions. pcr-mediated mutagenesis demonstrated that the second gaac motif in the sequence gaacn7gaacn7gaac located upstream of the r. sphaeroides lexa gene is absolutely necessary for its dna damage-mediated induction. moreover, mutagenesis of either the first or the third gaac motif in this sequence reduced, but did not abolish, the inducibility of the r. sphaeroides lexa ... | 2000 | 10954081 |
| oxidation-reduction properties of disulfide-containing proteins of the rhodobacter capsulatus cytochrome c biogenesis system. | oxidation-reduction titrations for the active-site disulfide/dithiol couples of the helx- and ccl2-encoded proteins involved in cytochrome c biogenesis in the purple non-sulfur bacterium rhodobacter capsulatus have been carried out. the r. capsulatus helx and ccl2 proteins are predicted to function as part of a dithiol/disulfide cascade that reduces a disulfide on the apocytochromes c so that two cysteine thiols are available to form thioether linkages between the heme prosthetic group and the p ... | 2000 | 10956006 |
| electron transfer between the quinones in the photosynthetic reaction center and its coupling to conformational changes. | the electron transfer between the two quinones q(a) and q(b) in the bacterial photosynthetic reaction center (brc) is coupled to a conformational rearrangement. recently, the x-ray structures of the dark-adapted and light-exposed brc from rhodobacter sphaeroides were solved, and the conformational changes were characterized structurally. we computed the reaction free energy for the electron transfer from to q(b) in the x-ray structures of the dark-adapted and light-exposed brc from rb. sphaeroid ... | 2000 | 10956039 |
| metronidazole activation is mutagenic and causes dna fragmentation in helicobacter pylori and in escherichia coli containing a cloned h. pylori rdxa(+) (nitroreductase) gene. | much of the normal high sensitivity of wild-type helicobacter pylori to metronidazole (mtz) depends on rdxa (hp0954), a gene encoding a novel nitroreductase that catalyzes the conversion of mtz from a harmless prodrug to a bactericidal agent. here we report that levels of mtz that partially inhibit growth stimulate forward mutation to rifampin resistance in rdxa(+) (mtz(s)) and also in rdxa (mtz(r)) h. pylori strains, and that expression of rdxa in escherichia coli results in equivalent mtz-indu ... | 2000 | 10960092 |
| the flagellar filament of rhodobacter sphaeroides: ph-induced polymorphic transitions and analysis of the flic gene. | flagellar motility in rhodobacter sphaeroides is notably different from that in other bacteria. r. sphaeroides moves in a series of runs and stops produced by the intermittent rotation of the flagellar motor. r. sphaeroides has a single, plain filament whose conformation changes according to flagellar motor activity. conformations adopted during swimming include coiled, helical, and apparently straight forms. this range of morphological transitions is larger than that in other bacteria, where fi ... | 2000 | 10960108 |
| cumulant analysis of charge recombination kinetics in bacterial reaction centers reconstituted into lipid vesicles. | the kinetics of charge recombination between the primary photoxidized donor (p(+)) and the secondary reduced quinone acceptor (q(b)(-)) have been studied in reaction centers (rcs) from the purple photosynthetic bacterium rhodobacter sphaeroides incorporated into lecithin vesicles containing large ubiquinone pools over the temperature range 275 k </= t </= 307 k. to account for the non-exponential kinetics of p(+) re-reduction observed following a flash, a new approach has been developed, based o ... | 2000 | 10968981 |
| self-regulation phenomena in bacterial reaction centers. i. general theory. | a model for light-induced charge separation in a donor-acceptor system of the reaction center of photosynthetic bacteria is described. this description is predicated on a self-regulation of the flow of photo-activated electrons due to self-consistent, slow structural rearrangements of the macromolecule. effects of the interaction between the separated charges and the slow structural modes of the biomolecule may accumulate during multiple, sequential charge transfer events. this accumulation prod ... | 2000 | 10968988 |
| fine tuning bacterial chemotaxis: analysis of rhodobacter sphaeroides behaviour under aerobic and anaerobic conditions by mutation of the major chemotaxis operons and chey genes. | rhodobacter sphaeroides chemotaxis is significantly more complex than that of enteric bacteria. rhodobacter sphaeroides has multiple copies of chemotaxis genes (two chea, one cheb, two cher, three chew, five chey but no chez), controlling a single 'stop-start' flagellum. the growth environment controls the level of expression of different groups of genes. tethered cell analysis of mutants suggests that chey(4) and chey(5) are the motor-binding response regulators. the histidine protein kinase ch ... | 2000 | 10970853 |
| inactivation of the gene for phospholipid n-methyltransferase in sinorhizobium meliloti: phosphatidylcholine is required for normal growth. | in phosphatidylcholine (pc)-containing prokaryotes, only the methylation pathway of pc biosynthesis was thought to occur. however, a second choline-dependent pathway for pc formation, the pc synthase (pcs) pathway, exists in sinorhizobium (rhizobium) meliloti in which choline is condensed with cdp-diacylglyceride. here, we characterize the methylation pathway of pc biosynthesis in s. meliloti. a mutant deficient in phospholipid n-methyltransferase (pmt) was complemented with a s. meliloti gene b ... | 2000 | 10972799 |
| the crystal structure of the escherichia coli moba protein provides insight into molybdopterin guanine dinucleotide biosynthesis. | the molybdenum cofactor (moco) is found in a variety of enzymes present in all phyla and comprises a family of related molecules containing molybdopterin (mpt), a tricyclic pyranopterin with a cis-dithiolene group, as the invariant essential moiety. mpt biosynthesis involves a conserved pathway, but some organisms perform additional reactions that modify mpt. in eubacteria, the cofactor is often present in a dinucleotide form combining mpt and a purine or pyrimidine nucleotide via a pyrophosphat ... | 2000 | 10978347 |
| mechanism of assembly of the bis(molybdopterin guanine dinucleotide)molybdenum cofactor in rhodobacter sphaeroides dimethyl sulfoxide reductase. | a fully defined in vitro system has been developed for studying the mechanism of assembly of the bis(molybdopterin guanine dinucleotide)molybdenum cofactor in rhodobacter sphaeroides dimethyl sulfoxide reductase (dmsor). r. sphaeroides dmsor expressed in a moba(-) escherichia coli strain lacks molybdopterin and molybdenum but contains a full complement of guanine in the form of gmp and gdp. escherichia coli moba, molybdopterin-mo, gtp, and mgcl(2) are required and sufficient for the in vitro act ... | 2000 | 10978348 |
| confirmation of the involvement of protein domain movement during the catalytic cycle of the cytochrome bc1 complex by the formation of an intersubunit disulfide bond between cytochrome b and the iron-sulfur protein. | to study the essentiality of head domain movement of the rieske iron-sulfur protein (isp) during bc(1) catalysis, rhodobacter sphaeroides mutants expressing his-tagged cytochrome bc(1) complexes with three pairs of cysteines engineered (one cysteine each) on the interface between cytochrome b and isp, a185c(cytb)/k70c(isp), i326c(cytb)/g165c(isp), and t386c(cytb)/k164c(isp), were generated and characterized. formation of an intersubunit disulfide bond between cytochrome b and isp is detected in ... | 2000 | 10978350 |
| femtosecond dynamics of the forbidden carotenoid s1 state in light-harvesting complexes of purple bacteria observed after two-photon excitation. | time-resolved excited-state absorption intensities after direct two-photon excitation of the carotenoid s(1) state are reported for light-harvesting complexes of purple bacteria. direct excitation of the carotenoid s(1) state enables the measurement of subsequent dynamics on a fs time scale without interference from higher excited states, such as the optically allowed s(2) state or the recently discovered dark state situated between s(1) and s(2). the lifetimes of the carotenoid s(1) states in t ... | 2000 | 10984512 |
| characteristics of the aerobic respiratory chains of the microaerophiles campylobacter jejuni and helicobacter pylori. | the respiratory chain enzymes of microaerophilic bacteria should play a major role in their adaptation to growth at low oxygen tensions. the genes encoding the putative nadh:quinone reductases (ndh-1), the ubiquinol:cytochrome c oxidoreductases (bc1 complex) and the terminal oxidases of the microaerophiles campylobacter jejuni and helicobacter pylori were analysed to identify structural elements that may be required for their unique energy metabolism. the gene clusters encoding ndh-1 in both c. ... | 2000 | 10985736 |
| rhodobaca bogoriensis gen. nov. and sp. nov., an alkaliphilic purple nonsulfur bacterium from african rift valley soda lakes. | from enrichment cultures established for purple nonsulfur bacteria using water and sediment samples from lake bogoria and crater lake, two soda lakes in the african rift valley, three strains of purple nonsulfur bacteria were isolated; strain lbb1 was studied in detail. cells of strain lbb1 were motile and spherical to rod-shaped, suggesting a relationship to rhodobacter or rhodovulum species, and the organism was capable of both phototrophic and chemotrophic growth on a wide variety of organic ... | 2000 | 10985738 |
| reversible dissociation of thiolate ligands from molybdenum in an enzyme of the dimethyl sulfoxide reductase family. | much is unknown concerning the role of thiolate ligands of molybdenum in molybdopterin enzymes. it has been suggested that thiolate dissociation from molybdenum is part of the catalytic mechanism of bis-molybdopterin enzymes of the dimethyl sulfoxide reductase (dmsor) family. for dmsor from rhodobacter capsulatus, thiolate dissociation has therefore been investigated crystallographically, by uv/visible spectroscopy, and by enzyme assays. when crystallized from sodium citrate, all four thiolates ... | 2000 | 10985771 |
| the orf162b sequence of rhodobacter capsulatus encodes a protein required for optimal levels of photosynthetic pigment-protein complexes. | the orf162b sequence, the second open reading frame 3' of the reaction center (rc) h protein gene puha in the rhodobacter capsulatus photosynthesis gene cluster, is shown to be transcribed from a promoter located 5' of puha. a nonpolar mutation of orf162b was generated by replacing most of the coding region with an antibiotic resistance cartridge. although the mutant strain initiated rapid photosynthetic growth, growth slowed progressively and cultures often entered a pseudostationary phase. the ... | 2000 | 10986247 |
| evaluation of nitrofurantoin combination therapy of metronidazole-sensitive and -resistant helicobacter pylori infections in mice. | the main objectives of this study were to determine whether the nitroreductase enzyme encoded by the rdxa gene of helicobacter pylori was responsible for reductive activation of nitrofurantoin and whether a triple-therapy regimen with nitrofurantoin was able to eradicate metronidazole-sensitive and -resistant h. pylori infections from mice. the susceptibilities to nitrofurantoin of parent and isogenic rdxa mutant strains (three pairs), as well as a series of matched metronidazole-sensitive and - ... | 2000 | 10991835 |
| sigma(54) promoters control expression of genes encoding the hook and basal body complex in rhodobacter sphaeroides. | gene expression of the flagellar system is tightly controlled by external stimuli or intracellular signals. a general picture of this regulation has been obtained from studies of salmonella enterica serovar typhimurium. however, these regulatory mechanisms do not apply to all bacterial groups. in this study, we have investigated regulation of the flagellar genetic system in rhodobacter sphaeroides. deletion analysis, site-directed mutagenesis, and 5'-end mapping were conducted in order to identi ... | 2000 | 11004178 |
| conformational relaxation following reduction of the photoactive bacteriopheophytin in reaction centers from blastochloris viridis. influence of mutations at position m208. | the photochemically trapped bacteriopheophytin (bph) b radical anion in the active branch (phi(a)(&z.rad;-)) of reaction centers (rcs) from blastochloris (formerly called rhodopseudomonas) viridis is characterized by 1h-endor as well as optical absorption spectroscopy. the two site-directed mutants yf(m208) and yl(m208), in which tyrosine at position m208 is replaced by phenylalanine and leucine, respectively, are investigated and compared with the wild type. the residue at m208 is in close prox ... | 2000 | 11004434 |
| re-emerging structures: continuing crystallography of the bacterial reaction centre. | the reaction centre is nature's solar battery, and is found in a number of variations on a common theme in plants, algae and photosynthetic bacteria. during the last 20 years, a combination of x-ray crystallography, spectroscopy and mutagenesis has provided increasingly detailed insights into the mechanism of light energy transduction in the bacterial reaction centre. this mini-review looks at the application of x-ray crystallography to the bacterial reaction centre, focussing in particular on r ... | 2000 | 11004458 |
| proton-coupled electron transfer at the q(o) site: what type of mechanism can account for the high activation barrier? | in rhodobacter sphaeroides, transfer of the first electron in quinol oxidation by the bc(1) complex shows kinetic features (a slow rate (approx. 1.5 x 10(3)/s), high activation energy (approx. 65 kj/mol) and reorganization energy, lambda (2.5 v)) that are unexpected from marcus theory and the distances shown by the structures. reduction of the oxidized iron-sulfur protein occurs after formation of the enzyme-substrate complex, and involves a h-transfer in which the electron transfer occurs throu ... | 2000 | 11004463 |
| proton transfer from glutamate 286 determines the transition rates between oxygen intermediates in cytochrome c oxidase. | we have investigated the electron-proton coupling during the peroxy (p(r)) to oxo-ferryl (f) and f to oxidised (o) transitions in cytochrome c oxidase from rhodobacter sphaeroides. the kinetics of these reactions were investigated in two different mutant enzymes: (1) ed(i-286), in which one of the key residues in the d-pathway, e(i-286), was replaced by an aspartate which has a shorter side chain than that of the glutamate and, (2) ml(ii-263), in which the redox potential of cu(a) is increased b ... | 2000 | 11004473 |
| primary structure characterization of a rhodocyclus tenuis diheme cytochrome c reveals the existence of two different classes of low-potential diheme cytochromes c in purple phototropic bacteria. | the complete amino acid sequence of a 26-kda low redox potential cytochrome c-551 from rhodocyclus tenuis was determined by a combination of edman degradation and mass spectrometry. there are 240 residues including two heme binding sites at positions 41, 44, 128, and 132. there is no evidence for gene doubling. the only known homolog of rc. tenuis cytochrome c-551 is the diheme cytochrome c-552 from pseudomonas stutzeri which contains 268 residues and heme binding sites at nearly identical posit ... | 2000 | 11019819 |
| structure of rsri methyltransferase, a member of the n6-adenine beta class of dna methyltransferases. | dna methylation is important in cellular, developmental and disease processes, as well as in bacterial restriction-modification systems. methylation of dna at the amino groups of cytosine and adenine is a common mode of protection against restriction endonucleases afforded by the bacterial methyltransferases. the first structure of an n:6-adenine methyltransferase belonging to the beta class of bacterial methyltransferases is described here. the structure of m. rsr:i from rhodobacter sphaeroides ... | 2000 | 11024175 |
| substrate binding in vitro and kinetics of rsri [n6-adenine] dna methyltransferase. | rsr:i [n:6-adenine] dna methyltransferase (m.rsr:i), which recognizes gaattc and is a member of a restriction-modification system in rhodobacter sphaeroides, was purified to >95% homogeneity using a simplified procedure involving two ion exchange chromatographic steps. electrophoretic gel retardation assays with purified m.rsr:i were performed on unmethylated, hemimethylated, dimethylated or non-specific target dna duplexes (25 bp) in the presence of sinefungin, a potent inhibitory analog of ado ... | 2000 | 11024176 |
| a plausible mechanism of electron transfer between quinones in photosynthetic reaction centers. | the mechanism of long-range electron transfer between the primary and the secondary quinone of photosynthetic reaction centers has been investigated, with particular attention on the role of the iron-histidine bridge. computations suggest that in such a system, where the molecular subunits are packed together by h-bonds, a mobile electron, injected on one end of the chain, can be carried to the other end by switching the positions of the h-bonded hydrogens. energy estimates would suggest that th ... | 2000 | 11027482 |
| magnetoselection effects in epr spectra of the primary-donor triplet state in reaction centers of the phototrophic bacterium rhodobacter sphaeroides r26. | | 2000 | 11029028 |
| characterization of the hydrogen-deuterium exchange activities of the energy-transducing hupsl hydrogenase and h(2)-signaling hupuv hydrogenase in rhodobacter capsulatus. | rhodobacter capsulatus synthesizes two homologous protein complexes capable of activating molecular h(2), a membrane-bound [nife] hydrogenase (hupsl) linked to the respiratory chain, and an h(2) sensor encoded by the hupuv genes. the activities of hydrogen-deuterium (h-d) exchange catalyzed by the hupsl-encoded and the hupuv-encoded enzymes in the presence of d(2) and h(2)o were studied comparatively. whereas hupsl is in the membranes, hupuv activity was localized in the soluble cytoplasmic frac ... | 2000 | 11029418 |
| molybdate-dependent expression of dimethylsulfoxide reductase in rhodobacter capsulatus. | expression of the dimethylsulfoxide respiratory (dor) operon of rhodobacter is regulated by oxygen, light intensity and availability of substrate. since dimethylsulfoxide reductase contains a pterin molybdenum cofactor, the role of molybdate in the regulation of dor operon expression was investigated. in this report we show that the molybdate-responsive transcriptional regulator, mopb, and molybdate are essential for maximal dimethylsulfoxide reductase activity and expression of a dora::lacz tra ... | 2000 | 11034280 |
| pigment-protein architecture in the light-harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment-protein arrangement? | structural analysis of crystallized peripheral (lh2) and core antenna complexes (lh1) of purple bacteria has revealed circular aggregates of high rotational symmetry (c8, c9 and c16, respectively). quantum-chemical calculations indicate that in particular the waterwheel-like arrangements of pigments should show characteristic structure-sensitive spectroscopic behavior in the near infrared absorption region. laser-spectroscopic data obtained with non-crystallized, isolated lh2 of rhodospirillum m ... | 2000 | 11034303 |
| mouse-colonizing helicobacter pylori ss1 is unusually susceptible to metronidazole due to two complementary reductase activities. | in most strains of helicobacter pylori, mutational inactivation of the rdxa (hp0954) gene, which encodes a nitroreductase that converts metronidazole (mtz) from a harmless prodrug to a mutagenic and bacteriocidal product, is sufficient to make this pathogen resistant to clinically significant levels of mtz. here we report that ss1, a strain with the special ability to colonize mice, is unusual in being susceptible to very low concentrations of mtz (0.5 microgram/ml) and in being especially diffi ... | 2000 | 11036035 |
| efficient exchange of the primary quinone acceptor q(a) in isolated reaction centers of rhodopseudomonas viridis. | a key step in the conversion of solar energy into chemical energy by photosynthetic reaction centers (rcs) occurs at the level of the two quinones, q(a) and q(b), where electron transfer couples to proton transfer. a great deal of our understanding of the mechanisms of these coupled reactions relies on the seminal work of okamura et al. [okamura, m. y., isaacson, r. a., & feher, g. (1975) proc. natl. acad. sci. usa 88, 3491-3495], who were able to extract with detergents the firmly bound ubiquin ... | 1997 | 11038584 |
| [effect of dipyridamole on recombination of photooxidized bacteriochlorophylla and photoreduced primary quinone in reactive centers of purple bacteria and degradation of form m412 of bacteriorhodopsin]. | it is shown that the addition of dipyridamole (2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido[5,4d]py rim idine) (up to 10(-4) m) leads to a drastic acceleration of the dark recombination reaction between photooxidized bacteriochlorophyll and photoreduced primary quinone in reaction centers of rhodobacter sphaeroides. the value of the acceleration is similar to that registered under cryogenic temperatures. the extent of the effect of dipyridamole derivatives depended on their structure. in wil ... | 2000 | 11040971 |
| identification of the structural subunits required for formation of the metal centers in subunit i of cytochrome c oxidase of rhodobacter sphaeroides. | genetic manipulation of the aa(3)-type cytochrome c oxidase of rhodobacter sphaeroides was used to determine the minimal structural subunit associations required for the assembly of the heme a and copper centers of subunit i. in the absence of the genes for subunits ii and iii, expression of the gene for subunit i in rb. sphaeroides allowed purification of a form of free subunit i (subunit i(a)()) that contained a single heme a. no copper was present in this protein, indicating that the heme a(3 ... | 2000 | 11041864 |
| an examination of how structural changes can affect the rate of electron transfer in a mutated bacterial photoreaction centre. | a series of reaction centres bearing mutations at the (phe) m197 position were constructed in the photosynthetic bacterium rhodobacter sphaeroides. this residue is adjacent to the pair of bacteriochlorophyll molecules (p(l) and p(m)) that is the primary donor of electrons (p) in photosynthetic light-energy transduction. all of the mutations affected the optical and electrochemical properties of the p bacteriochlorophylls. a mutant reaction centre with the change phe m197 to arg (fm197r) was crys ... | 2000 | 11042110 |
| redox-related conformational changes in rhodobacter capsulatus cytochrome c2. | weft-noesy and transfer weft-noesy nmr spectra were used to determine the heme proton assignments for rhodobacter capsulatus ferricytochrome c2. the fermi contact and pseudo-contact contributions to the paramagnetic effect of the unpaired electron in the oxidized state were evaluated for the heme and ligand protons. the chemical shift assignments for the 1h and 15n nmr spectra were obtained by a combination of 1h-1h and 1h-15n two-dimensional nmr spectroscopy. the short-range nuclear overhauser ... | 2000 | 11045628 |
| effect of dipyridamole on the recombination kinetics between photooxidized bacteriochlorophyll and photoreduced primary quinone in reaction centres of purple bacteria. | the action of dipyridamole (dip) on dark recombination between the photooxidized special pair bacteriochlorophyll bchl2+ and reduced primary quinone acceptor q(a)- in the reaction centres (rcs) of the bacteria rhodobacter sphaeroides was studied in the presence of different detergents (ldao, triton x-100, sodium cholate, sodium dodecyl sulfate). dip accelerated this reaction approximately 4-5-fold. in rcs with the extracted h-subunit, the effect of dip was observed at lower concentrations. the p ... | 2000 | 11051080 |
| fate of selenate and selenite metabolized by rhodobacter sphaeroides. | cultures of a purple nonsulfur bacterium, rhodobacter sphaeroides, amended with approximately 1 or approximately 100 ppm selenate or selenite, were grown phototrophically to stationary phase. analyses of culture headspace, separated cells, and filtered culture supernatant were carried out using gas chromatography, x-ray absorption spectroscopy, and inductively coupled plasma spectroscopy-mass spectrometry, respectively. while selenium-amended cultures showed much higher amounts of seo(3)(2-) bio ... | 2000 | 11055934 |
| an imperfect inverted repeat is critical for dna binding of the response regulator regr of bradyrhizobium japonicum. | regr is the response regulator of the regsr two-component regulatory system in bradyrhizobium japonicum. the only target known so far is the fixr-nifa operon, encoding the redox-responsive transcription factor nifa, which activates many genes required for symbiotic nitrogen fixation in soybean nodules. in previous in vivo studies, we identified a 32 bp upstream activating sequence located around position -68, which is essential for regr-dependent expression of the fixr-nifa operon. here, we used ... | 2000 | 11058113 |
| respiratory pathways of rhodobacter sphaeroides 2.4.1(t): identification and characterization of genes encoding quinol oxidases. | rhodobacter sphaeroides 2.4.1(t) respires aerobically via a branched respiratory chain consisting of both cytochrome c oxidases and quinol oxidases. here, genes from chromosome ii encoding two distinct quinol oxidases have been characterized. the qoxba genes encode a putative heme-copper quinol oxidase, whereas the qxtab genes encode a quinol oxidase homologous to the cyanide-insensitive oxidase of pseudomonas aeruginosa. no phenotype was observed for mutations in either oxidase in the wild-type ... | 2000 | 11064196 |
| dipyridamole and its derivatives modify the kinetics of the electron transport in reaction centers from rhodobacter sphaeroides. | a well known vasodilator dipyridamole (dip), 2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido[5,4-d]pyrim idine, and its derivatives have recently been shown as potential co-activators (modulators) in the phenomenon of multidrug resistance (mdr) in cancer therapy. they inhibit the specific function of a transmembrane p-glycoprotein responsible for the ex-flux of anti-cancer drugs from tumor cells. to clarify molecular mechanisms of the anti-mdr activity of dip and its two derivatives, ra25 and r ... | 2000 | 11073318 |
| identification of the proton pathway in bacterial reaction centers: both protons associated with reduction of qb to qbh2 share a common entry point. | the reaction center from rhodobacter sphaeroides uses light energy for the reduction and protonation of a quinone molecule, q(b). this process involves the transfer of two protons from the aqueous solution to the protein-bound q(b) molecule. the second proton, h(+)(2), is supplied to q(b) by glu-l212, an internal residue protonated in response to formation of q(a)(-) and q(b)(-). in this work, the pathway for h(+)(2) to glu-l212 was studied by measuring the effects of divalent metal ion binding ... | 2000 | 11078513 |
| involvement of cd14 and beta2-integrins in activating cells with soluble and particulate lipopolysaccharides and mannuronic acid polymers. | lipopolysaccharide (lps) and related bacterial products can be recognized by host inflammatory cells in a particulate, bacterium-bound form, as well as in various soluble, released forms. in the present study we have compared the mechanisms used by lps, detoxified lps (dlps), and mannuronic acid polymers (m-polymers), in solution or covalently linked to particles, in stimulating monocytes to tumor necrosis factor (tnf) production. the addition of recombinant lps binding protein (lbp) and/or solu ... | 2000 | 11083794 |
| aspartate-187 of cytochrome b is not needed for dccd inhibition of ubiquinol: cytochrome c oxidoreductase in rhodobacter sphaeroides chromatophores. | n,n'-dicyclohexylcarbodiimide (dccd) has been reported to inhibit steady-state proton translocation by cytochrome bc(1) and b(6)f complexes without significantly altering the rate of electron transport, a process referred to as decoupling. in chromatophores of the purple bacterium rhodobacter sphaeroides, this has been associated with the specific labeling of a surface-exposed aspartate-187 of the cytochrome b subunit of the bc(1) complex [wang et al. (1998) arch. biochem. biophys. 352, 193-198] ... | 2000 | 11087372 |
| fourier transform infrared evidence of proton uptake by glutamate l212 upon reduction of the secondary quinone qb in the photosynthetic reaction center from rhodobacter capsulatus. | the photoreduction of the secondary quinone q(b) in native reaction centers (rcs) of rhodobacter capsulatus and in rcs from the glul212 --> gln and glul212 --> ala mutants has been investigated at ph 7 in (1)h(2)o and (2)h(2)o by light-induced fourier transform infrared (ftir) difference spectroscopy. the q(b)(-)/q(b) ftir difference spectra reflect changes of quinone-protein interactions and of protonation state of carboxylic acid groups as well as reorganization of the protein upon electron tr ... | 2000 | 11087422 |
| formation of the "peroxy" intermediate in cytochrome c oxidase is associated with internal proton/hydrogen transfer. | when dioxygen is reduced to water by cytochrome c oxidase a sequence of oxygen intermediates are formed at the reaction site. one of these intermediates is called the "peroxy" (p) intermediate. it can be formed by reacting the two-electron reduced (mixed-valence) cytochrome c oxidase with dioxygen (called p(m)), but it is also formed transiently during the reaction of the fully reduced enzyme with oxygen (called p(r)). in recent years, evidence has accumulated to suggest that the o-o bond is cle ... | 2000 | 11087423 |
| characterization of a major cluster of nif, fix, and associated genes in a sugarcane endophyte, acetobacter diazotrophicus. | a major 30.5-kb cluster of nif and associated genes of acetobacter diazotrophicus (syn. gluconacetobacter diazotrophicus), a nitrogen-fixing endophyte of sugarcane, was sequenced and analyzed. this cluster represents the largest assembly of contiguous nif-fix and associated genes so far characterized in any diazotrophic bacterial species. northern blots and promoter sequence analysis indicated that the genes are organized into eight transcriptional units. the overall arrangement of genes is most ... | 2000 | 11092875 |
| the dipyridamole effect on the photoactive bacteriochlorophyll interaction with quinone acceptors in reaction centers of purple bacteria. | the effect of dipyridamole (10(-6)-10(-3) m) on the photomobilized electron transport in the system of quinone acceptors q(a)-q(b) of isolated photosynthetic reaction centers of rhodobacter sphaeroides and on its temporary stabilization on q(b) was studied. depending on the type of the detergent present in the reaction center (lauryl dimethylamine oxide, triton x-100, sodium dodecyl sulfate, and sodium cholate), dipyridamole could increase the time of the electron transfer to q(b). the dipyridam ... | 2000 | 11093579 |
| divergent mechanisms of 5' 23s rrna ivs processing in the alpha-proteobacteria. | widespread occurrence of a separate small rna derived from the 5'-end of 23s rrna and of an intervening sequence (ivs) which separates this domain from the main segment of 23s rrna in the alpha-proteobacteria implies that processing reactions which act to excise the ivs are also maintained in this group. we previously characterized the first example of processing of this ivs in rhodopseudomonas palustris, which is classified with the bradyrhizobia in this case, ivs excision occurs by a multistep ... | 2000 | 11095671 |
| behavioral responses of rhodobacter sphaeroides to linear gradients of the nutrients succinate and acetate. | rhodobacter sphaeroides cells were tethered by their flagella and subjected to increasing and decreasing nutrient gradients. using motion analysis, changes in flagellar motor rotation were measured and the responses of the cells to the chemotactic gradients were determined. the steepness and concentration ranges of increasing and decreasing gradients were varied, and the bacterial responses were measured. this allowed the limits of gradients that would invoke changes in flagellar behavior to be ... | 2000 | 11097888 |
| a homologue of the tryptophan-rich sensory protein tspo and fixl regulate a novel nutrient deprivation-induced sinorhizobium meliloti locus. | a nutrient deprivation-induced locus in sinorhizobium meliloti strain 1021 was identified by use of a tn5-luxab reporter gene transposon. the tagged locus is comprised of two open reading frames (orfs) designated ndia and ndib for nutrient deprivation-induced genes a and b. comparison of the deduced amino acid sequences of both ndia and ndib to the protein databases failed to reveal similarity to any known genes. the expression of the ndi locus was found to be induced by carbon and nitrogen depr ... | 2000 | 11097914 |
| coordinated, differential expression of two genes through directed mrna cleavage and stabilization by secondary structures. | metabolic engineering and multisubunit protein production necessitate the expression of multiple genes at coordinated levels. in bacteria, genes for multisubunit proteins or metabolic pathways are often expressed in operons under the control of a single promoter; expression of the genes is coordinated by varying transcript stability and the rate of translation initiation. we have developed a system to place multiple genes under the control of a single promoter and produce proteins encoded in tha ... | 2000 | 11097920 |
| characterization of a rhodobacter capsulatus reaction center mutant that enhances the distinction between spectral forms of the initial electron donor. | a large scale mutation of the rhodobacter capsulatus reaction center m-subunit gene, sym2-1, has been constructed in which amino acid residues m205-m210 have been changed to the corresponding l subunit amino acids. two interconvertable spectral forms of the initial electron donor are observed in isolated reaction centers from this mutant. which conformation dominates depends on ionic strength, the nature of the detergent used, and the temperature. reaction centers from this mutant have a ground- ... | 2000 | 11101294 |
| preferential binding of equine ferricytochrome c to the bacterial photosynthetic reaction center from rhodobacter sphaeroides. | redox titration of horse heart cytochrome c (cyt c), in the presence of varying concentrations of detergent-solubilized photosynthetic reaction center (rc) from rhodobacter sphaeroides, revealed an rc concentration-dependent decrease in the measured cyt c midpoint potential that is indicative of a 3.6 +/- 0.2-fold stronger binding affinity of oxidized cytochrome to a single binding site. this effect was correlated with preferential binding in the functional complex by redox titration of the frac ... | 2000 | 11101298 |
| ubiquinone binding, ubiquinone exclusion, and detailed cofactor conformation in a mutant bacterial reaction center. | the x-ray crystal structure of a rhodobacter sphaeroides reaction center with the mutation ala m260 to trp (am260w) has been determined. diffraction data were collected that were 97.6% complete between 30.0 and 2.1 a resolution. the electron density maps confirm the conclusions of a previous spectroscopic study, that the q(a) ubiquinone is absent from the am260w reaction center (ridge, j. p., van brederode, m. e., goodwin, m. g., van grondelle, r., and jones, m. r. (1999) photosynthesis res. 59, ... | 2000 | 11106481 |