| effect of light and oxygen and adaptation to changing light conditions in a photosynthetic mutant in which the lhii complex of rhv. sulfidophilum was heterologously expressed in a strain of rb. capsulatus whose puc operon was deleted. | in this paper we show the effect of oxygen and light on the expression of the photosynthetic apparatus of a mutant heterologously expressing the puc operon. this mutant was obtained by introducing in trans an expression plasmid, bearing the puc a, b, and c genes of rhv. sulfidophilum, as well as its own promoter, in an lhii(-) mutant of rb. capsulatus. the results showed that oxygen and light repressed lhii expression. even low-light intensities lowered the lhii content to undetectable levels by ... | 2002 | 12177744 |
| [growth of phototrophic bacterium rhodobacter sphaeroides and formation of carotenoids on mineral water "dzhermuk"]. | a possibility to use thermal carbon sulphate-hydrocarbonate mineral waters "dzhermuk" as the basis of nutrient medium for growing has been established. no distinct correlation was observed between biomass accumulation and carotenoids formation: maximum yields of the biomass is registered under microaetrophilic growth conditions, while that of carotenoids--under anaerobic conditions. maximum synthesis of carotenoids is observed at illumination of 1000-1500 lx, more intensive illumination (3000 lx ... | 2002 | 12190021 |
| rhizobium sin-1 lipopolysaccharide (lps) prevents enteric lps-induced cytokine production. | endotoxin (lipopolysaccharide (lps)), a component of gram-negative bacteria, is among the most potent proinflammatory substances known. the lipid-a region of this molecule initiates the production of multiple host-derived inflammatory mediators, including cytokines (e.g. tumor necrosis factor-alpha (tnfalpha)). it has been a continuous effort to identify methods of interfering with the interaction between enteric lps and inflammatory cells using natural and synthetic lps analogs. some of these l ... | 2002 | 12193596 |
| genetic determination of polyhydroxyalkanoate metabolism in rhodobacter capsulatus sb1003. | a cluster of four genes was identified in the rhodobacter capsulatus genome that is involved in pha metabolism. these genes encode the pha granule-associated protein (pha2), the regulator for granule formation (pha1), the pha synthase (phac) and the pha depolymerase (orfx). two other genes, namely those encoding beta-ketothiolase (phaa) and acetoacetyl-coa reductase (phab), are not linked to this cluster. | 2002 | 12194204 |
| the entry point of the k-proton-transfer pathway in cytochrome c oxidase. | cytochrome c oxidase is a redox-driven proton pump. the enzyme has two proton input pathways, leading from the solution on the n-side to the binuclear center. one of these pathways, the k-pathway, is used for proton uptake upon reduction of the binuclear center. it is also important for local charge compensation during reaction of the fully reduced enzyme with o2. two different locations have been proposed to constitute the entry point of the k-pathway: near s(i-299) or near e(ii-101), respectiv ... | 2002 | 12196018 |
| cobalamin (vitamin b(12)) biosynthesis in rhodobacter capsulatus. | in rhodobacter capsulatus, cobalamin biosynthesis has been shown to occur when the bacteria are grown either aerobically or anaerobically. however, a comparison of the main cobalamin biosynthetic operon found within r. capsulatus would suggest that the encoded proteins belong to the oxygen-dependent pathway for cobalamin biosynthesis, although, significantly, no homologue of the essential mono-oxygenase cobg has yet been detected. nonetheless, within this main cob operon is found a large open re ... | 2002 | 12196155 |
| the first non-turnover voltammetric response from a molybdenum enzyme: direct electrochemistry of dimethylsulfoxide reductase from rhodobacter capsulatus. | the first direct voltammetric response from a molybdenum enzyme under non-turnover conditions is reported. cyclic voltammetry of dimethylsulfoxide reductase from rhodobacter capsulatus reveals a reversible mo(vi/v) response at +161 mv followed by a reversible mo(v/iv) response at -102 mv versus nhe at ph 8. the higher potential couple exhibits a ph dependence consistent with protonation upon reduction to the mo(v) state and we have determined the p k(a) for this semi-reduced species to be 9.0. t ... | 2002 | 12203025 |
| supramolecular organisation of the photosynthetic chain in anoxygenic bacteria. | this minireview summarizes our present view of the supramolecular organization of the photosynthetic apparatus of rhodobacter sphaeroides and rhodobacter capsulatus. these two species present a close association between two reaction centers (rcs), one cytochrome (cyt) bc(1) and one cyt c. in r. sphaeroides, the rcs are only partially surrounded by lh1 complexes. this open ring of lh1 complexes is required for an efficient photoinduced cyclic electron transfer only under conditions where the quin ... | 2002 | 12206892 |
| influence of structure, ph and membrane potential on proton movement in cytochrome oxidase. | cytochrome c oxidase (cco) reconstituted into phospholipid vesicles and subject to a membrane potential, exhibits different characteristics than the free enzyme, with respect to effects of mutations, ph, inhibitors, and native structural differences between cco from different species. the results indicate that the membrane potential influences the conformation of cco and the direction of proton movement in the exit path. the importance of the protein structure above the hemes in proton exit, bac ... | 2002 | 12206898 |
| molecular characterization of functional modules of plasmid pwks1 of paracoccus pantotrophus dsm 11072. | the complete nucleotide sequence of the small, cryptic plasmid pwks1 (2697 bp) of paracoccus pantotrophus dsm 11072 was determined. the g+c content of the sequence of this plasmid was 62 mol%. analysis revealed that over 80% of the plasmid genome was covered by two orfs, orf1 and orf2, which were capable of encoding putative peptides of 44.1 and 37.8 kda, respectively. mutational analysis showed that orf2 was crucial for plasmid replication. the translational product of orf2 shared local homolog ... | 2002 | 12213930 |
| interdependent expression of the cconoqp-rdxbhis loci in rhodobacter sphaeroides 2.4.1. | the rdxbhis gene cluster of rhodobacter sphaeroides 2.4.1, located downstream of the cconoqp operon encoding the cbb(3) cytochrome c oxidase, is required for the posttranscriptional modification of the cbb(3) cytochrome c oxidase. the cbb(3) cytochrome c oxidase is the main terminal oxidase under microaerobic conditions, as well as a component of the signal transduction pathway controlling photosynthesis gene expression. because of the intimate functional and positional relationships of the ccon ... | 2002 | 12218019 |
| the nucleotide sequence of gltd gene encoding the small subunit of rhodobacter sphaeroides glutamate synthase. | we have determined the complete nucleotide sequence of a 2 387 bp chromosomal sali-ecori fragment, which contains the structural gene (gltd) for the small subunit of rhodobacter sphaeroides glutamate synthase, as well as the 5'- and 3'-flanking regions. an open reading frame of 1 242 base pairs was identified as the r. sphaeroides gltd gene. the mw of the small subunit, as deduced from the nucleotide sequence, was estimated to be 44 kd. a comparison of the nucleotide sequence revealed a high sim ... | 1997 | 12219208 |
| protein dynamics: imidazole and 2-mercaptoethanol binding to the rhodobacter capsulatus cytochrome c(2) mutant, glycine 95 proline. | the class i c-type cytochromes can bind exogenous ligands in the oxidized state, with the kinetics of ligand binding providing information on naturally occurring intramolecular dynamics. typically, nitrogenous bases are used as ligands; however, it is less well known that 2-mercaptoethanol (bme), a commonly used cytochrome reducing agent, can form a complex with the heme. to better understand the cytochrome-mercaptan interaction, we have investigated the kinetics of binding of bme to wild type a ... | 2002 | 12220527 |
| tuning of the redox potential of the primary electron donor in reaction centres of purple bacteria: effects of amino acid polarity and position. | mutation of residues his l168 and phe m197 in the reaction centre from rhodobacter sphaeroides has an unusually strong effect on the mid-point redox potential (e(m)) of the pair of bacteriochlorophylls that form the primary donor of electrons, tuning e(m) over a range of nearly 250 mv. this effect is correlated to the accompanying change in the permanent dipole of the l168 or m197 residue, suggesting it is mediated by changes in charge-dipole interactions. comparisons with mutations made at a va ... | 2002 | 12220655 |
| effects of oxygen on the dark recombination between photoreduced secondary quinone and oxidized bacteriochlorophyll in rhodobacter sphaeroides reaction centers. | the influence of duration of exposure to actinic light (from 1 sec to 10 min) and temperature (from 3 to 35 degrees c) on the temporary stabilization of the photomobilized electron in the secondary quinone acceptor (qb) locus of rhodobacter sphaeroides reaction centers (rc) was studied under aerobic or anaerobic conditions. optical spectrophotometry and esr methods were used. the stabilization time increased significantly upon increasing the exposure duration under aerobic conditions. the stabil ... | 2002 | 12223089 |
| effect of addition of rhodobacter sp. to activated-sludge reactors treating piggery wastewater. | under aerobic conditions, the decay rates of purple nonsulfur bacteria (rhodobacter sp.) in the light and dark follow first-order kinetics with rate constants of 0.22 and 0.32 day(-1), respectively. the performance of the conventional activated-sludge reactor (casr) treating anaerobically pretreated piggery wastewater (656-1.110 mg chemical oxygen demand, cod/l) can be enhanced by the addition of rhodobacter sp. by performing regressive and statistical analyses using the proposed model and exper ... | 2001 | 12230169 |
| appa is a blue light photoreceptor that antirepresses photosynthesis gene expression in rhodobacter sphaeroides. | photosynthetic bacteria regulate photosystem synthesis in response to alterations in oxygen tension and light intensity. in this study we show that the ppsr repressor from rhodobacter sphaeroides binds to dna in a redox-dependent manner through the formation/breakage of an intramolecular disulfide bond. we also demonstrate that ppsr is antagonized by the flavin-containing antirepressor, appa, that is capable of breaking the disulfide bond in oxidized ppsr as well as forming a stable appa-ppsr(2) ... | 2002 | 12230978 |
| mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis. | biological sulfide oxidation is a reaction occurring in all three domains of life. one enzyme responsible for this reaction in many bacteria has been identified as sulfide:quinone oxidoreductase (sqr). the enzyme from rhodobacter capsulatus is a peripherally membrane-bound flavoprotein with a molecular mass of approximately 48 kda, presumably acting as a homodimer. in this work, sqr from rb. capsulatus has been modified with an n-terminal his tag and heterologously expressed in and purified from ... | 2002 | 12269799 |
| tactic responses to oxygen in the phototrophic bacterium rhodobacter sphaeroides ws8n. | the temporal and spatial behavior of a number of mutants of the photosynthetic, facultative anaerobe rhodobacter sphaeroides to both step changes and to gradients of oxygen was analyzed. wild-type cells, grown under a range of conditions, showed microaerophilic behavior, accumulating in a 1.3-mm band about 1.3 mm from the meniscus of capillaries. evidence suggests this is the result of two signaling pathways. the strength of any response depended on the growth and incubation conditions. deletion ... | 2002 | 12270816 |
| charge separation induces conformational changes in the photosynthetic reaction centre of purple bacteria. | x-ray structures of the wild-type reaction centre from rhodobacter sphaeroides have been determined to a resolution of 1.87 a in the neutral (dark) state and to 2.06 a in the charge-separated (light-excited) state. whereas the overall protein structures of both states are rather similar, the domain around the secondary quinone shows significant shifts. the quinone molecule itself is observed at two different positions. in the neutral state, 55% of the quinone is located distally and 45% proximal ... | 2002 | 12351882 |
| three semidominant barley mutants with single amino acid substitutions in the smallest magnesium chelatase subunit form defective aaa+ hexamers. | many enzymes of the bacteriochlorophyll and chlorophyll biosynthesis pathways have been conserved throughout evolution, but the molecular mechanisms of the key steps remain unclear. the magnesium chelatase reaction is one of these steps, and it requires the proteins bchi, bchd, and bchh to catalyze the insertion of mg(2+) into protoporphyrin ix upon atp hydrolysis. structural analyses have shown that bchi forms hexamers and belongs to the atpases associated with various cellular activities (aaa( ... | 2002 | 12357035 |
| the four different sigma(54) factors of rhodobacter sphaeroides are not functionally interchangeable. | the sigma(54) factor is highly conserved in a large number of bacterial species. from the complete genome sequence of rhodobacter sphaeroides, it was possible to identify four different sequences encoding potentially functional sigma(54) factors. in this work, we provide evidence that one of these copies (rpon2) is specifically required to express the flagellar genes in this bacterium. a mutant strain carrying a lesion in the rpon2 gene was unable to swim even though the rpon1 and rpon3 proteins ... | 2002 | 12366832 |
| bluf: a novel fad-binding domain involved in sensory transduction in microorganisms. | a novel fad-binding domain, bluf, exemplified by the n-terminus of the appa protein from rhodobacter sphaeroides, is present in various proteins, primarily from bacteria. the bluf domain is involved in sensing blue-light (and possibly redox) using fad and is similar to the flavin-binding pas domains and cryptochromes. the predicted secondary structure reveals that the bluf domain is a novel fad-binding fold. | 2002 | 12368079 |
| conservation of the biotin regulon and the bira regulatory signal in eubacteria and archaea. | biotin is a necessary cofactor of numerous biotin-dependent carboxylases in a variety of microorganisms. the strict control of biotin biosynthesis in escherichia coli is mediated by the bifunctional bira protein, which acts both as a biotin-protein ligase and as a transcriptional repressor of the biotin operon. little is known about regulation of biotin biosynthesis in other bacteria. using comparative genomics and phylogenetic analysis, we describe the biotin biosynthetic pathway and the bira r ... | 2002 | 12368242 |
| a system for the heterologous expression of complex redox proteins in rhodobacter capsulatus: characterisation of recombinant sulphite:cytochrome c oxidoreductase from starkeya novella. | the phototrophic purple non-sulfur bacterium rhodobacter capsulatus expresses a wide variety of complex redox proteins in response to changing environmental conditions. here we report the construction and evaluation of an expression system for recombinant proteins in that organism which makes use of the dor promoter from the same organism. a generic expression vector, pdorex, was constructed and used to express sulphite:cytochrome c oxidoreductase from starkeya novella, a heterodimeric protein c ... | 2002 | 12372602 |
| reductive effect of h(2) uptake and poly-beta-hydroxybutyrate formation on nitrogenase-mediated h(2) accumulation of rhodobacter sphaeroides according to light intensity. | nitrogenase-mediated h(2) accumulation of rhodobacter sphaeroides under photoheterotrophic conditions is reduced directly by the hydrogenase activity catalyzing h(2) uptake and indirectly by energy-demanding metabolic processes such as poly-beta-hydroxybutyrate (phb) formation. h(2) accumulation of r. sphaeroides was examined during cell growth under illumination of 15, 7, and 3 w/m(2). mutations in either hupsl (h(2)-uptake hydrogenase) or phbc (phb synthase) had no effect on nitrogenase activi ... | 2002 | 12382056 |
| comparative characterization of repabc-type replicons of paracoccus pantotrophus composite plasmids. | the repabc replicons have an unusual structure, since they carry genes coding for partitioning (repa, repb) and replication (repc) proteins, which are organized in an operon. so far, the presence of these compact bi-functional modules has been reported only in the megaplasmids of the rhizobiaceae and within the plasmid ptav1 (107kb) of paracoccus versutus. we studied the distribution of repabc-type replicons within bacteria belonging to the genus paracoccus. we found that repabc replicons occur ... | 2002 | 12383730 |
| vibrational spectroscopy favors a unique qb binding site at the proximal position in wild-type reaction centers and in the pro-l209 --> tyr mutant from rhodobacter sphaeroides. | in the various x-ray structures of native reaction centers (rcs) from the photosynthetic bacterium rhodobacter sphaeroides, two distinct main binding sites (distal and proximal) for the secondary quinone q(b) have been described in the literature. the movement of q(b) from its distal to proximal position has been proposed to account for the conformational gate limiting the rate of the first electron transfer from the primary quinone q(a-) to q(b). recently, q(b) was found to bind in the proximal ... | 2002 | 12390017 |
| the hfq-like protein nrfa of the phototrophic purple bacterium rhodobacter capsulatus controls nitrogen fixation via regulation of nifa and anfa expression. | the rhodobacter capsulatus nrfa gene product exhibits extensive similarity to the nif (nitrogen fixation) regulatory factor nrfa of azorhizobium caulinodans and the nucleoid-associated protein hfq of escherichia coli. mutational analysis revealed that, in contrast to the situation in a. caulinodans, nrfa is not essential for diazotrophic growth of r. capsulatus, but it is required for maximal growth rates with n(2) as sole nitrogen source via either molybdenum nitrogenase or the alternative nitr ... | 2002 | 12399038 |
| evolutionary implications of phylogenetic analyses of the gene transfer agent (gta) of rhodobacter capsulatus. | the gene transfer agent (gta) of the a-proteobacterium rhodobacter capsulatus is a cell-controlled genetic exchange vector. genes that encode the gta structure are clustered in a 15-kb region of the r. capsulatus chromosome, and some of these genes show sequence similarity to known bacteriophage head and tail genes. however, the production of gta is controlled at the level of transcription by a cellular two-component signal transduction system. this paper describes homologues of both the gta str ... | 2002 | 12399927 |
| characterization of the flgg operon of rhodobacter sphaeroides ws8 and its role in flagellum biosynthesis. | in this work, we show evidence regarding the functionality of a large cluster of flagellar genes in rhodobacter sphaeroides. the genes of this cluster, flgghijkl and orf-1, are mainly involved in the formation of the basal body, and flgk and flgl encode the hook-associated proteins hap1 and hap3. in general, these genes showed a good similarity as compared with those reported for salmonella enterica. however, flgj and flgk showed particular features that make them unique among the flagellar sequ ... | 2002 | 12401220 |
| protein-lipid interactions in the purple bacterial reaction centre. | the purple bacterial reaction centre uses the energy of sunlight to power energy-requiring reactions such as the synthesis of atp. during the last 20 years, a combination of x-ray crystallography, spectroscopy and mutagenesis has provided a detailed insight into the mechanism of light energy transduction in the bacterial reaction centre. in recent years, structural techniques including x-ray crystallography and neutron scattering have also been used to examine the environment of the reaction cen ... | 2002 | 12409196 |
| spin-lattice relaxation of coupled metal-radical spin-dimers in proteins: application to fe(2+)-cofactor (q(a)(-.), q(b)(-.), phi(-.)) dimers in reaction centers from photosynthetic bacteria. | the spin-lattice relaxation times (t(1)) for the reduced quinone acceptors q(a)(-.) and q(b)(-.), and the intermediate pheophytin acceptor phi(-.), were measured in native photosynthetic reaction centers (rc) containing a high spin fe(2+) (s = 2) and in rcs in which fe(2+) was replaced by diamagnetic zn(2+). from these data, the contribution of the fe(2+) to the spin-lattice relaxation of the cofactors was determined. to relate the spin-lattice relaxation rate to the spin-spin interaction betwee ... | 2002 | 12414679 |
| a mutation in subunit i of cytochrome oxidase from rhodobacter sphaeroides results in an increase in steady-state activity but completely eliminates proton pumping. | the heme-copper oxidases convert the free energy liberated in the reduction of o(2) to water into a transmembrane proton electrochemical potential (protonmotive force). one of the essential structural elements of the enzyme is the d-channel, which is thought to be the input pathway, both for protons which go to form h(2)o ("chemical protons") and for protons that get translocated across the lipid membrane ("pumped protons"). the d-channel contains a chain of water molecules extending about 25 a ... | 2002 | 12416987 |
| overexpression of ccl1-2 can bypass the need for the putative apocytochrome chaperone cych during the biogenesis of c-type cytochromes. | in gram-negative bacteria, including rhodobacter capsulatus, the membrane protein cych acts as a putative apocytochrome chaperone during the biogenesis of c-type cytochromes. cych-null mutants are unable to produce various c-type cytochromes and sustain photosynthetic (ps) growth that requires the cytochromes c1 and c2 or cy. however, ps+ revertants are readily obtained only on minimal, but not on enriched, medium. to obtain further information about the biogenesis of c-type cytochromes, these s ... | 2002 | 12421312 |
| the third chemotaxis locus of rhodobacter sphaeroides is essential for chemotaxis. | the purple photosynthetic bacterium rhodobacter sphaeroides has three loci encoding multiple homologues of the bacterial chemosensory proteins: 13 putative chemoreceptors, four chew, four chea, six chey, two cheb and three cher. previously, studies have shown that, although deletion of cheop1 led to only minor changes in behaviour, deletion of cheop2 led to a loss of taxis. the third locus encodes two chea, one cher, one cheb, one chew, one chey, a putative cytoplasmic chemoreceptor (tlpt) and a ... | 2002 | 12421313 |
| phosphotransfer in rhodobacter sphaeroides chemotaxis. | the two-component sensing system controlling bacterial chemotaxis is one of the best studied in biology. rhodobacter sphaeroides has a complex chemosensory pathway comprising two histidine protein kinases (cheas) and eight downstream response regulators (six cheys and two chebs) rather than the single copies of each as in escherichia coli. we used in vitro analysis of phosphotransfer to start to determine why r.sphaeroides has these multiple homologues. chea(1) and chea(2) contain all the key mo ... | 2002 | 12421557 |
| inhibition of acetate and propionate assimilation by itaconate via propionyl-coa carboxylase in isocitrate lyase-negative purple bacterium rhodospirillum rubrum. | itaconate is known as a potent inhibitor of isocitrate lyase. unexpectedly, itaconate was a strong inhibitor of acetate and propionate assimilation in isocitrate lyase-negative purple non-sulfur bacterium rhodospirillum rubrum. it was shown that in cell extracts of r. rubrum itaconate inhibited propionyl-coa carboxylase (pcc) activity. the participation of pcc in propionate assimilation in r. rubrum is well-documented, but the inhibition of acetate assimilation suggests that pcc is also involved ... | 2002 | 12423751 |
| long-chain acyl-homoserine lactone quorum-sensing regulation of rhodobacter capsulatus gene transfer agent production. | many proteobacteria use acyl-homoserine lactones as quorum-sensing signals. traditionally, biological detection systems have been used to identify bacteria that produce acyl-homoserine lactones, although the specificities of these detection systems can limit discovery. we used a sensitive approach that did not require a bioassay to detect production of long-acyl-chain homoserine lactone production by rhodobacter capsulatus and paracoccus denitrificans. these long-chain acyl-homoserine lactones a ... | 2002 | 12426339 |
| differential expression of the co2 fixation operons of rhodobacter sphaeroides by the prr/reg two-component system during chemoautotrophic growth. | in rhodobacter sphaeroides, the two cbb operons encoding duplicated calvin-benson bassham (cbb) co2 fixation reductive pentose phosphate cycle structural genes are differentially controlled. in attempts to define the molecular basis for the differential regulation, the effects of mutations in genes encoding a subunit of cbb3 cytochrome oxidase, ccop, and a global response regulator, prra (rega), were characterized with respect to co2 fixation (cbb) gene expression by using translational lac fusi ... | 2002 | 12426354 |
| up-regulated expression of the cbb(i) and cbb(ii) operons during photoheterotrophic growth of a ribulose 1,5-bisphosphate carboxylase-oxygenase deletion mutant of rhodobacter sphaeroides. | in a rhodobacter sphaeroides ribulose 1,5-bisphosphate carboxylase-oxygenase deletion strain that requires an exogenous electron donor for photoheterotrophic growth, transcription of the genes of the calvin-benson-bassham (cbb) cycle was increased. this finding pointed to a potential physiological effector that enhances the capability of the positive transcriptional activator cbbr to mediate cbb transcription. this effector is most likely ribulose 1,5-bisphosphate or a metabolite derived from th ... | 2002 | 12426361 |
| the h-ns-like protein hvra modulates expression of nitrogen fixation genes in the phototrophic purple bacterium rhodobacter capsulatus by binding to selected nif promoters. | genetic analyses based on chromosomal lac fusions to nitrogen fixation (nif) genes demonstrated that nifa-dependent transcriptional activation of expression of rhodobacter capsulatus nifh and nifb1 was negatively modulated by hvra, whereas regulation of rpon, nifa1, and nifa2 was independent of hvra. expression of hvra itself was not influenced by a mutation in ntrc, which is absolutely essential for n(2) fixation. furthermore, hvra accumulated to comparable levels in the presence and absence of ... | 2002 | 12435496 |
| mutation of alphaphe55 of methylamine dehydrogenase alters the reorganization energy and electronic coupling for its electron transfer reaction with amicyanin. | methylamine dehydrogenase (madh) possesses an alpha(2)beta(2) structure with each smaller beta subunit possessing a tryptophan tryptophylquinone (ttq) prosthetic group. phe55 of the alpha subunit is located where the substrate channel from the enzyme surface opens into the active site. site-directed mutagenesis of alphaphe55 has revealed roles for this residue in determining substrate specificity and binding monovalent cations at the active site. it is now shown that the alphaf55a mutation also ... | 2002 | 12437349 |
| nuclear wave packet motion between p* and p(+)b(a)(-) potential surfaces with a subsequent electron transfer to h(a) in bacterial reaction centers at 90 k. electron transfer pathway. | in rhodobacter sphaeroides r-26 reaction centers (rcs) the nuclear wave packet induced by 25 fs excitation at 90 k moves on the primary electron donor p* potential energy hypersurface with initial frequency at approximately 130 cm(-1) (monitored by stimulated emission measurement). at the long-wavelength side of p* stimulated emission at 935 nm the wave packet is transferred to the surface with p(+)b(a)(-) character at 120, 380, 1.2 fs, etc. delays (monitored by measurement of the primary electr ... | 2002 | 12437359 |
| whole-genome analysis of photosynthetic prokaryotes. | the process of photosynthesis has had profound global-scale effects on earth; however, its origin and evolution remain enigmatic. here we report a whole-genome comparison of representatives from all five groups of photosynthetic prokaryotes and show that horizontal gene transfer has been pivotal in their evolution. excluding a small number of orthologs that show congruent phylogenies, the genomes of these organisms represent mosaics of genes with very different evolutionary histories. we have al ... | 2002 | 12446909 |
| modulation of the midpoint potential of the [2fe-2s] rieske iron sulfur center by qo occupants in the bc1 complex. | following addition of myxothiazol to antimycin-treated chromatophores from rhodobacter sphaeroides poised at an ambient redox potential (e(h)) of approximately 300 mv, the amplitude of the flash-induced cytochrome c(1) oxidation in the ms range increased, indicating a decrease in the availability of electrons from the immediate donor to c(1), the rieske iron-sulfur protein (isp). because the effect was seen only over the limited e(h) range, we conclude that it is due to a decrease in the apparen ... | 2002 | 12450404 |
| tlpc, a novel chemotaxis protein in rhodobacter sphaeroides, localizes to a discrete region in the cytoplasm. | tlpc is encoded in the second chemotaxis operon of rhodobacter sphaeroides. this protein shows some homology to membrane-spanning chemoreceptors of many bacterial species but, unlike these, is essential for r. sphaeroides chemotaxis to all compounds tested. genomic replacement of tlpc with a c-terminal gfp fusion demonstrated that tlpc localized to a discrete cluster within the cytoplasm. immunogold electron microscopy also showed that tlpc localized to a cytoplasmic electron-dense region. corre ... | 2002 | 12453209 |
| the influence of detergents on the solubility of membrane proteins. | the relationship between the effect of detergents and amphiphiles on protein solubility and their use in crystallization solutions was examined for the reaction center from rhodobacter sphaeroides. measurement by a centrifugation assay of the solubility of the reaction center as a function of ionic strength revealed dramatic differences in the intrinsic solubility at zero ionic strength in the presence of various detergents and amphiphiles. high protein-solubility values were found for beta-octy ... | 2002 | 12454467 |
| characterization of a novel enoyl-acyl carrier protein reductase of diazaborine-resistant rhodobacter sphaeroides mutant. | rhodobacter sphaeroides contains two enoyl-acyl carrier protein (acp) reductases, fabi(1) and fabi(2). however, fabi(1) displays most of the cellular enzyme activity. the spontaneous diazaborine-resistant mutation was mapped as substitution of glutamine for proline 155 (p155q) of fabi(1). the mutation of fabi(1)[p155q] increased the specificity constants (k(cat)/k(m)) for crotonyl-acp and nadh by more than 2-fold, while the site-directed mutation g95s (fabi(1)[g95s]), corresponding to the well-k ... | 2002 | 12459184 |
| the dmpc lipid phase transition influences differently the first and the second electron transfer reactions in bacterial reaction centers. | photosynthetic reaction centers (rcs) from rhodobacter sphaeroides were incorporated in dimyristoylphosphatidylcholine (dmpc) liposomes. the first and second electron transfer rates (k(ab)(1) and k(ab)(2), respectively) between the first and the second quinone electron acceptors have been measured as a function of temperature, across the phase transition of dmpc (23 degrees c). the eyring plots of k(ab)(1) display straight lines. in contrast, the eyring plots for k(ab)(2) in proteoliposomes show ... | 2002 | 12459469 |
| spectroscopic and oxidation-reduction properties of rhodobacter capsulatus cytochrome c1 and its m183k and m183h variants. | two variants of the cytochrome c1 component of the rhodobacter capsulatus cytochrome bc1 complex, in which met183 (an axial heme ligand) was replaced by lysine (m183k) or histidine (m183h), have been analyzed. electron paramagnetic resonance (epr) and magnetic circular dichroism (mcd) spectra of the intact complex indicate that the histidine/methionine heme ligation of the wild-type cytochrome is replaced by histidine/lysine ligation in m183k and histidine/histidine ligation in m183h. variable a ... | 2002 | 12460675 |
| asymmetric conductivity of engineered porins. | positively charged peptide segments of 16 and 18 residues were inserted at a periplasmic turn of the porin from rhodobacter blasticus in order to form an electric field-dependent plug. the x-ray diffraction analysis of a mutant confirmed that the structure of the porin had remained intact and that the insert was mobile. incorporation experiments of single molecules into lipid bilayers showed that the distribution of electric conduction increments depended on the field polarity. the observed dist ... | 2002 | 12468713 |
| rnase e is involved in 5'-end 23s rrna processing in alpha-proteobacteria. | in rhodobacter capsulatus and rhizobium leguminosarum, an internal transcribed spacer consisting of helices 9 and 10 is removed during 23s rrna processing, which leads to the occurrence of a 5.8s-like rrna. the particular rrna maturation steps are not known, with exception of the initial rnase iii cleavage in helix 9. we found that gc-rich stem-loop structures of helix 9, which are released by rnase iii, are immediately degraded. the degradation of helix 10 is slower and its kinetics differs in ... | 2002 | 12470646 |
| the molecular chain of electron transfer in the primary act of bacterial photosynthesis as determined using femtosecond spectroscopy. | | 2002 | 12474802 |
| determination of proton transfer rates by chemical rescue: application to bacterial reaction centers. | the bacterial reaction center (rc) converts light into chemical energy through the reduction of an internal quinone molecule q(b) to q(b)h(2). in the native rc, proton transfer is coupled to electron transfer and is not rate-controlling. consequently, proton transfer is not directly observable, and its rate was unknown. in this work, we present a method for making proton transfer rate-controlling, which enabled us to determine its rate. the imidazole groups of the his-h126 and his-h128 proton do ... | 2002 | 12475220 |
| influence of the protein environment on the properties of a tyrosyl radical in reaction centers from rhodobacter sphaeroides. | the influence of the local environment on the formation of a tyrosyl radical was investigated in modified photosynthetic reaction centers from rhodobacter sphaeroides. the reaction centers contain a tyrosine residue placed approximately 10 a from a highly oxidizing bacteriochlorophyll dimer. measurements by both optical and electron paramagnetic resonance spectroscopy revealed spectral features that are assigned as arising primarily from an oxidized bacteriochlorophyll dimer at low ph values and ... | 2002 | 12484763 |
| on the involvement of the water-polaron mechanism in energy trapping by reaction centers of purple bacteria. | a locus for binding a mobile water molecule was searched for in the immediate vicinity of the special pair in the reaction center. using the proteus pc-program (a part of the grasp package) atomic structures of the reaction centers were analyzed in purple bacteria rhodopseudomonas viridis and rhodobacter sphaeroides. in both structures the loci for binding mobile water molecules were found at the distance of about 4.5 a from the middle of the special pair in the reaction center. the reorientatio ... | 2002 | 12495417 |
| effect of isotope substitution and controlled dehydration on the photoinduced electron transport reactions of quinone acceptors and multiheme cytochrome c in bacterial photosynthetic reaction center. | isotope substitution of h2o by 2h2o causes an increase in the rate of dark recombination between photooxidized bacteriochlorophyll (p+) and reduced primary quinone acceptor in rhodobacter sphaeroides reaction centers (rc) at room temperature. the isotopic effect declines upon decreasing the temperature. dehydration of rc complexes of ectothiorhodospira shaposhnikovii chromatophores containing multiheme cytochrome c causes a decrease in the efficiency of transfer of a photomobilized electron betw ... | 2002 | 12495430 |
| the two photocycles of photoactive yellow protein from rhodobacter sphaeroides. | the absorption spectrum of the photoactive yellow protein from rhodobacter sphaeroides (r-pyp) shows two maxima, absorbing at 360 nm (r-pyp(360)) and 446 nm (r-pyp(446)), respectively. both forms are photoactive and part of a temperature- and ph-dependent equilibrium (haker, a., hendriks, j., gensch, t., hellingwerf, k. j., and crielaard, w. (2000) febs lett. 486, 52-56). at 20 degrees c, for pyp characteristic, the 446-nm absorbance band displays a photocycle, in which the depletion of the 446- ... | 2003 | 12496261 |
| afm characterization of tilt and intrinsic flexibility of rhodobacter sphaeroides light harvesting complex 2 (lh2). | atomic force microscopy (afm) has developed into a powerful tool to investigate membrane protein surfaces in a close-to-native environment. here we report on the surface topography of rhodobacter sphaeroides light harvesting complex 2 (lh2) reconstituted into two-dimensional crystals. these photosynthetic trans-membrane proteins formed cylindrical oligomeric complexes, which inserted tilted into the lipid membrane. this peculiar packing of an integral membrane protein allowed us to determine oli ... | 2003 | 12498803 |
| [slow photoinduced changes in reaction centers of rhodobacter sphaeroides r-26 by holographic interferometry]. | using the on-line holographic interferometry, changes in the refraction index of illuminated solutions containing the rhodobacter sphaeroides r-26 reaction centers isolated from membranes by detergents of ionic and nonionic nature were registered. factors affecting the refraction index of these solutions were analyzed. it was shown that the photoinduced changes in this parameter are due to structural changes in the molecular complex of reaction centers. the results of measurements of the kinetic ... | 2002 | 12500559 |
| site-directed mutagenesis of dimethyl sulfoxide reductase from rhodobacter capsulatus: characterization of a y114 --> f mutant. | a system for expressing site-directed mutants of the molybdenum enzyme dimethyl sulfoxide reductase from rhodobacter capsulatus in the natural host was constructed. this system was used to generate and express dimethyl sulfoxide reductase with a y114f mutation. the y114f mutant had an increased k(cat) and increased k(m) toward both dimethyl sulfoxide and trimethylamine n-oxide compared to the native enzyme, and the value of k(cat)/k(m) was lower for both substrates in the mutant enzyme. the y114 ... | 2002 | 12501205 |
| production of ubiquinone-10 using bacteria. | among the bacterial strains known to contain ubiquinone-10, three strains, agrobacterium tumefaciens ky-3085 (atcc4452), paracoccus denitrificans ky-3940 (atcc19367) and rhodobacter sphaeroides ky-4113 (ferm-p4675), were selected as excellent producers of this ubiquinone. the ubiquinone-10 production by the agrobacterium and rhodobacter strains was affected by aeration. an ethionine-resistant mutant (m-37) derived from a. tumefaciens ky-3085 promoted increased production of ubiquinone-10 (20% hi ... | 1998 | 12501289 |
| a preliminary report of phylogenetic diversity of bacterial strains isolated from marine creatures. | bacterial diversity among marine creatures, especially molluscs, as a source for searching out novel lineages of bacteria, was studied. marine creatures were collected at the coasts of the kanto area in japan. a total of 116 strains of bacteria were isolated from the intestines of 19 species of marine creatures includings molluscs, pisces and protochordata. partial sequencing of 16s rdna revealed that most of the isolates belonged to the gamma subclass of the proteobacteria and cytophaga-flavoba ... | 2002 | 12501435 |
| biotin sulfoxide reductase: tryptophan 90 is required for efficient substrate utilization. | rhodobacter sphaeroides f. sp. denitrificans biotin sulfoxide reductase (bsor) catalyzes the reduction of d-biotin d-sulfoxide to biotin and contains the molybdopterin guanine dinucleotide (mgd) cofactor as its sole prosthetic group. comparison of the primary sequences of bsor and the closely related enzyme dimethyl sulfoxide reductase (dmsor) indicated a number of conserved residues, including an active-site tryptophan residue (w90), which has been suggested to be involved in hydrogen bonding t ... | 2003 | 12504898 |
| farnesyl diphosphate synthase gene of three phototrophic bacteria and its use as a phylogenetic marker. | farnesyl diphosphate (fpp) synthase is essential not only for phototrophic bacteria in carotenoid biosynthesis, but also for non-phototrophic bacteria in the biosynthesis of physiologically important compounds. the gene encoding fpp synthase was assessed as a molecular marker to investigate the intermingled relationship between the phototropic and non-phototropic bacteria in the alpha-proteobacteria based on 16s rrna analysis. the fpp synthase amino acid sequences from three phototropic bacteria ... | 2002 | 12508853 |
| features of rhodobacter sphaeroides ccmfh. | in this study, the in vivo function and properties of two cytochrome c maturation proteins, ccmf and ccmh from rhodobacter sphaeroides, were analyzed. strains lacking ccmh or both ccmf and ccmh are unable to grow under anaerobic conditions where c-type cytochromes are required, demonstrating their critical role in the assembly of these electron carriers. consistent with this observation, strains lacking both ccmf and ccmh are deficient in c-type cytochromes when assayed under permissive growth c ... | 2003 | 12511487 |
| think like a bacterium. conference on bacterial neural networks. | | 2003 | 12524513 |
| effect of famoxadone on photoinduced electron transfer between the iron-sulfur center and cytochrome c1 in the cytochrome bc1 complex. | famoxadone is a new cytochrome bc(1) q(o) site inhibitor that immobilizes the iron-sulfur protein (isp) in the b conformation. the effects of famoxadone on electron transfer between the iron-sulfur center (2fe-2s) and cyt c(1) were studied using a ruthenium dimer to photoinitiate the reaction. the rate constant for electron transfer in the forward direction from 2fe-2s to cyt c(1) was found to be 16,000 s(-1) in bovine cyt bc(1). binding famoxadone decreased this rate constant to 1,480 s(-1), co ... | 2003 | 12525495 |
| self-regulation phenomena applied to bacterial reaction centers: 2. nonequilibrium adiabatic potential: dark and light conformations revisited. | experimental and theoretical results in support of nonlinear dynamic behavior of photosynthetic reaction centers under light-activated conditions are presented. different conditions of light adaptation allow for preparation of reaction centers in either of two different conformational states. these states were detected both by short actinic flashes and by the switching of the actinic illumination level between different stationary state values. in the second method, the equilibration kinetics of ... | 2003 | 12547795 |
| rhodobacter capsulatus 1-deoxy-d-xylulose 5-phosphate synthase: steady-state kinetics and substrate binding. | 1-deoxy-d-xylulose 5-phosphate synthase (dxp synthase) catalyzes the thiamine diphosphate (tpp)-dependent condensation of pyruvate and d-glyceraldehyde 3-phosphate (gap) to yield dxp in the first step of the methylerythritol phosphate pathway for isoprenoid biosynthesis. steady-state kinetic constants for dxp synthase calculated from the initial velocities measured at varying concentrations of substrates were as follows: k(cat) = 1.9 +/- 0.1 s(-1), k(m)(gap) = 0.068 +/- 0.001 mm, and k(m)(pyruva ... | 2003 | 12549936 |
| sequence analysis reveals new membrane anchor of reaction centre-bound cytochromes possibly related to pufx. | most of the bacterial photosynthetic reaction centres known to date contain a cytochrome subunit with four covalently bound haem groups. in the case of blastochloris viridis, this reaction centre subunit is anchored in the membrane by a lipid molecule covalently attached to the cysteine which forms the n-terminus of the mature protein after processing by a signal peptidase. we show that posttranslational n-terminal cleavage of the cytochrome subunit does not occur in the aerobic photosynthetic b ... | 2003 | 12560097 |
| isolation and molecular characterization of pmg160, a mobilizable cryptic plasmid from rhodobacter blasticus. | a 3.4-kb cryptic plasmid was obtained from a new isolate of rhodobacter blasticus. this plasmid, designated pmg160, was mobilizable by the conjugative strain escherichia coli s17.1 into rhodobacter sphaeroides, rhodobacter capsulatus, and rhodopseudomonas palustris. it replicated in the latter strains but not in rhodospirillum rubrum, rhodocyclus gelatinosus, or bradyrhizobium species. plasmid pmg160 was stably maintained in r. sphaeroides for more than 100 generations in the absence of selectio ... | 2003 | 12570988 |
| characterization of the interaction of rhodobacter capsulatus cytochrome c peroxidase with charge reversal mutants of cytochrome c(2). | steady-state kinetics for the reaction of rhodobacter capsulatus bacterial cytochrome c peroxidase (bccp) with its substrate cytochrome c(2) were investigated. the rb. capsulatus bccp is dependent on calcium for activation as previously shown for the pseudomonas aeruginosa bccp and paracoccus denitrificans enzymes. furthermore, the activity shows a bell-shaped ph dependence with optimum at ph 7.0. enzyme activity is greatest at low ionic strength and drops off steeply as ionic strength increases ... | 2003 | 12573282 |
| intramolecular proton-transfer reactions in a membrane-bound proton pump: the effect of ph on the peroxy to ferryl transition in cytochrome c oxidase. | in the membrane-bound redox-driven proton pump cytochrome c oxidase, electron- and proton-transfer reactions must be coupled, which requires controlled modulation of the kinetic and/or thermodynamic properties of proton-transfer reactions through the membrane-spanning part of the protein. in this study we have investigated proton-transfer reactions through a pathway that is used for the transfer of both substrate and pumped protons in cytochrome c oxidase from rhodobacter sphaeroides. specifical ... | 2003 | 12578361 |
| protein-protein interactions between cytochrome b and the fe-s protein subunits during qh2 oxidation and large-scale domain movement in the bc1 complex. | the ubihydroquinone:cytochrome (cyt) c oxidoreductase, or bc(1) complex, and its homologue the b(6)f complex are key components of respiratory and photosynthetic electron transport chains as they contribute to the generation of an electrochemical gradient used by the atp synthase to produce atp. the bc(1) complex has two catalytic domains, ubihydroquinone oxidation (q(o)) and ubiquinone reduction (q(i)) sites, that are located on each side of the membrane. the key to the energetic efficiency of ... | 2003 | 12578362 |
| substitutions for glutamate 101 in subunit ii of cytochrome c oxidase from rhodobacter sphaeroides result in blocking the proton-conducting k-channel. | two functional input pathways for protons have been characterized in the heme-copper oxidases: the d-channel and the k-channel. these two proton-conducting channels have different functional roles and have been defined both by x-ray crystallography and by the characterization of site-directed mutants. whereas the entrance of the d-channel is well-defined as d132(i) (subunit i; rhodobacter sphaeroides numbering), the entrance of the k-channel has not been clearly defined. previous mutagenesis stu ... | 2003 | 12578386 |
| quinone reduction via secondary b-branch electron transfer in mutant bacterial reaction centers. | symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (p) and terminating in quinone acceptors (q)-are common features of photosynthetic reaction centers (rc). experimental observations show activity of only one of them-the a branch-in wild-type bacterial rcs. in a mutant rc, we now demonstrate that electron transfer can occur along the entire, normally inactive b-branch pathway to reduce the terminal acceptor q(b) on the time scale of nanoseconds. the ... | 2003 | 12578387 |
| b-side charge separation in bacterial photosynthetic reaction centers: nanosecond time scale electron transfer from hb- to qb. | we report time-resolved optical measurements of the primary electron transfer reactions in rhodobacter capsulatus reaction centers (rcs) having four mutations: phe(l181) --> tyr, tyr(m208) --> phe, leu(m212) --> his, and trp(m250) --> val (denoted yfhv). following direct excitation of the bacteriochlorophyll dimer (p) to its lowest excited singlet state p, electron transfer to the b-side bacteriopheophytin (h(b)) gives p(+)h(b)(-) in approximately 30% yield. when the secondary quinone (q(b)) sit ... | 2003 | 12590589 |
| redox and light regulation of gene expression in photosynthetic prokaryotes. | all photosynthetic organisms control expression of photosynthesis genes in response to alterations in light intensity as well as to changes in cellular redox potential. light regulation in plants involves a well-defined set of red- and blue-light absorbing photoreceptors called phytochrome and cryptochrome. less understood are the factors that control synthesis of the plant photosystem in response to changes in cellular redox. among a diverse set of photosynthetic bacteria the best understood re ... | 2003 | 12594923 |
| interactions of the cbbii promoter-operator region with cbbr and rega (prra) regulators indicate distinct mechanisms to control expression of the two cbb operons of rhodobacter sphaeroides. | in a previous study (dubbs, j. m., bird, t. h., bauer, c. e., and tabita, f. r. (2000) j. biol. chem. 275, 19224-19230), it was demonstrated that the regulators cbbr and rega (prra) interacted with both promoter proximal and promoter distal regions of the form i (cbb(i)) promoter operon specifying genes of the calvin-benson-bassham cycle of rhodobacter sphaeroides. to determine how these regulators interact with the form ii (cbb(ii)) promoter, three cbbf(ii)::lacz translational fusion plasmids w ... | 2003 | 12601011 |
| photoreduction of the quinone pool in the bacterial photosynthetic membrane: identification of infrared marker bands for quinol formation. | the photoreduction of the quinone (q) pool in the photosynthetic membrane of the purple bacterium rhodobacter sphaeroides was investigated by steady-state and time-resolved fourier transform infrared difference spectroscopy. the results are consistent with the existence of a homogeneous q pool inside the chromatophore membrane, with a size of around 20 q molecules per reaction center. ir marker bands for the quinone/quinol (q/qh(2)) redox couple were recognized. qh(2) bands are identified at 149 ... | 2003 | 12606050 |
| the position of qb in the photosynthetic reaction center depends on ph: a theoretical analysis of the proton uptake upon qb reduction. | electrostatics-based calculations have been performed to examine the proton uptake upon reduction of the terminal electron acceptor q(b) in the photosynthetic reaction center of rhodobacter sphaeroides as a function of ph and the associated conformational equilibrium. two crystal structures of the reaction center were considered: one structure was determined in the dark and the other under illumination. in the two structures, the q(b) was found in two different positions, proximal or distal to t ... | 2003 | 12609910 |
| an abundant periplasmic protein of the denitrifying phototroph rhodobacter sphaeroides f. sp. denitrificans is psts, a component of an abc phosphate transport system. | to understand a physiological role of an abundant 34-kda periplasmic protein in the denitrifying phototroph rhodobacter sphaeroides f. sp. denitrificans grown in a medium containing malate as the carbon source, the gene for the protein was isolated. the deduced amino acid sequence of the protein had a sequence similarity of 66.2% to that of psts from sinorhizobium meliloti. the downstream sequence of the rhodobacter psts contained five genes similar to pstcab and phoub, and its upstream sequence ... | 2003 | 12610226 |
| the effect of exchange of bacteriopheophytin a with plant pheophytin a on charge separation in y(m210)w mutant reaction centers of rhodobacter sphaeroides at low temperature. | the bacteriopheophytin a molecules at the h(a) and h(b) binding sites of reaction centers (rcs) of the y(m210)w mutant of rhodobacter sphaeroides were chemically exchanged with plant pheophytin a. the y(m210)w mutation slows down the formation of h(a)(-), presumably by raising the free energy level of the p(+)b(a)(-) state above that of p* due to increasing the oxidation potential of the primary electron donor p and lowering the reduction potential of the accessory bacteriochlorophyll b(a). exch ... | 2003 | 12615343 |
| two epr-detectable [4fe-4s] clusters, n2a and n2b, are bound to the nuoi (tyky) subunit of nadh:ubiquinone oxidoreductase (complex i) from rhodobacter capsulatus. | nadh:ubiquinone oxidoreductases (complex i) contain a subunit, tyky in the bovine enzyme and nuoi in the enzyme from rhodobacter capsulatus, which is assumed to bind two [4fe-4s] clusters because it contains two sets of conserved cysteine motifs similar to those found in the 2[4fe-4s] ferredoxins. it was recently shown that the tyky subunit is not an ordinary 2[4fe-4s] ferredoxin, but has a unique amino acid sequence, which is only found in nad(p)h:quinone oxidoreductases and certain membrane-bo ... | 2003 | 12615348 |
| role of rhodobacter sp. strain ps9, a purple non-sulfur photosynthetic bacterium isolated from an anaerobic swine waste lagoon, in odor remediation. | temporal pigmentation changes resulting from the development of a purple color in anaerobic swine waste lagoons were investigated during a 4-year period. the major purple photosynthetic bacterium responsible for these color changes and the corresponding reductions in odor was isolated from nine photosynthetic lagoons. by using morphological, physiological, and phylogenetic characterization methods we identified the predominant photosynthetic bacterium as a new strain of rhodobacter, designated r ... | 2003 | 12620863 |
| identification and in vivo characterization of ppaa, a regulator of photosystem formation in rhodobacter sphaeroides. | a regulatory protein, ppaa, involved in photosystem formation in the anoxygenic phototrophic proteobacterium rhodobacter sphaeroides has been identified and characterized in vivo. based on the phenotypes of cells expressing the ppaa gene in extra copy and on the phenotype of the ppaa null mutant, it was concluded that ppaa activates photopigment production and puc operon expression under aerobic conditions. this is in contrast to the function of the ppaa homologue from rhodobacter capsulatus, ae ... | 2003 | 12624200 |
| thioredoxin 2 is involved in oxidative stress defence and redox-dependent expression of photosynthesis genes in rhodobacter capsulatus. | thioredoxins are small ubiquitous proteins that display different functions mainly via redox-mediated processes. the facultatively photosynthetic bacterium rhodobacter capsulatus harbours at least two genes for thioredoxin 1 and 2, trxa and trxc. it is demonstrated that thioredoxin 2 of r. capsulatus can partially replace the thioredoxin 1 function as a hydrogen donor for methionine sulfoxide reductase but cannot replace thioredoxin 1 as a subunit of phage t7 dna polymerase. by inactivating the ... | 2003 | 12624204 |
| disease-related mutations in cytochrome c oxidase studied in yeast and bacterial models. | mitochondrial cytochrome c oxidase is a key protonmotive component of the respiratory chain. mutations in the mitochondrially-encoded subunits of the complex have been reported in association with a range of diseases. in this work we used yeast and bacterial mutants to assess the effect of human mutations in subunit 1 (l196i) and subunit 3 (g78s, a200t, delta f94-f98, f251l and w249stop). while the stop mutation at the c-terminus of subunit 3 and the short deletion were highly deleterious and ab ... | 2003 | 12631280 |
| excitation relaxation in the chemically modified photosynthetic reaction center from rhodobacter sphaeroides 601. | the ultrafast excitation relaxation in the sodium borohydride-treated reaction center of rhodobacter sphaeroides 601 was investigated with selective excitation. from the femtosecond pump-probe measurement at 790 nm, the excitation relaxation demonstrates a biexponential decay with time constants of about 200 fs and 1.4 ps. by comparison with the result from sodium ascorbate-pretreated modified rs601, it could be concluded that the dynamical trace at 790 nm mainly originates from the contribution ... | 2003 | 12632210 |
| a novel h-ns-like protein from an antarctic psychrophilic bacterium reveals a crucial role for the n-terminal domain in thermal stability. | we describe here new members of the h-ns protein family identified in a psychrotrophic acinetobacter spp. bacterium collected in siberia and in a psychrophilic psychrobacter spp. bacterium collected in antarctica. both are phylogenetically closely related to the hvra and spb rhodobacter transcriptional regulators. their amino acid sequence shares 40% identity, and their predicted secondary structure displays a structural and functional organization in two modules similar to that of h-ns in esche ... | 2003 | 12637536 |
| characterization of a tungsten-substituted nitrogenase isolated from rhodobacter capsulatus. | in the phototrophic non-sulfur bacterium rhodobacter capsulatus, the biosynthesis of the conventional mo-nitrogenase is strictly mo-regulated. significant amounts of both dinitrogenase and dinitrogenase reductase were only formed when the growth medium was supplemented with molybdate (1 microm). during cell growth under mo-deficient conditions, tungstate, at high concentrations (1 mm), was capable of partially (approximately 25%) substituting for molybdate in the induction of nitrogenase synthes ... | 2003 | 12667075 |
| redox potential of quinones in photosynthetic reaction centers from rhodobacter sphaeroides: dependence on protonation of glu-l212 and asp-l213. | the absolute values of the one-electron redox potentials of the two quinones (q(a) and q(b)) in bacterial photosynthetic reaction centers from rhodobacter sphaeroides were calculated by evaluating the electrostatic energies from the solution of the linearized poisson-boltzmann equation at ph 7.0. the redox potential for q(a) was calculated to be between -173 and -160 mv, which is close to the lowest measured values that are assumed to refer to nonequilibrated protonation patterns in the redox st ... | 2003 | 12667079 |
| rhodobacter sphaeroides has a family ii pyrophosphatase: comparison with other species of photosynthetic bacteria. | the cytoplasmic pyrophosphatase from rhodobacter sphaeroides was purified and characterized. the enzyme is a homodimer of 64 kda. the n-terminus was sequenced and used to obtain the complete pyrophosphatase sequence from the preliminary genome sequence of rba. sphaeroides, showing extensive sequence similarity to family ii or class c pyrophosphatases. the enzyme hydrolyzes only mg-pp(i) and mn-pp(i) with a k(m) of 0.35 mm for both substrates. it is not activated by free mg (2+), in contrast to t ... | 2003 | 12669192 |
| recombinant rhodobacter capsulatus xanthine dehydrogenase, a useful model system for the characterization of protein variants leading to xanthinuria i in humans. | rhodobacter capsulatus xanthine dehydrogenase (xdh) forms an (alphabeta)2 heterotetramer and is highly homologous to homodimeric eukaryotic xdhs. the crystal structures of bovine xdh and r. capsulatus xdh showed that the two proteins have highly similar folds. we have developed an efficient system for the recombinant expression of r. capsulatus xdh in escherichia coli. the recombinant protein shows spectral features and a range of substrate specificities similar to bovine milk xanthine oxidase. ... | 2003 | 12670960 |
| chemiluminescent-based methods to detect subpicomole levels of c-type cytochromes. | a variety of luminol-based substrates and either an autoradiographic film or a charge-coupled device (ccd) imaging system were used for chemiluminescence detection of c-type cytochromes. the pierce femto peroxidase substrate was at least 10 times more sensitive when using film than the highly cited 3,3('),5,5(')-tetramethylbenzidine (benzidine derivative) staining method and 50 times more sensitive when using a ccd imaging system. film or ccd imaging result in highly sensitive and quantitative s ... | 2003 | 12672416 |
| "green-like" and "red-like" rubisco cbbl genes in rhodobacter azotoformans. | we found that rhodobacter azotoformans ifo 16436t contains two different cbbl genes coding form i ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) large subunits. one gene is located within a "green-like" group of the rubisco phylogenetic tree, and the other is located within a "red-like" group. this is the first report that one organism contains both green-like and red-like rubisco genes. moreover, by pcr using primers which amplify two green-like and red-like cbbl genes alternatively ... | 2003 | 12679539 |
| electron transport dynamics at the quinone acceptor site of bacterial photosynthetic reaction centers as probed using fast temperature changes. | methods of laser-induced temperature jumps and fast freezing were used for testing the rates of thermoinduced conformational transitions of reaction center (rc) complexes in chromatophores and isolated rc preparations of various photosynthesizing purple bacteria. an electron transfer reaction from primary to secondary quinone acceptors was used as a probe of electron transport efficiency. the thermoinduced transition of the acceptor complex to the conformational state facilitating electron trans ... | 2003 | 12679860 |
| coupling of nuclear wavepacket motion and charge separation in bacterial reaction centers. | the mechanism of the charge separation and stabilization of separated charges was studied using the femtosecond absorption spectroscopy. it was found that nuclear wavepacket motions on potential energy surface of the excited state of the primary electron donor p* leads to a coherent formation of the charge separated states p(+)b(a)(-), p(+)h(a)(-) and p(+)h(b)(-) (where b(a), h(b) and h(a) are the primary and secondary electron acceptors, respectively) in native, pheophytin-modified and mutant r ... | 2003 | 12681478 |