| lipopolysaccharide structure influences the macrophage response via cd14-independent and cd14-dependent pathways. | cd14, a protein expressed on the surface of monocytes and neutrophils, is a major receptor for lipopolysaccharide (lps). studies with normal and cd14-deficient macrophages show that responses to low concentrations of lps require expression of cd14, whereas responses to high concentrations of lps are cd14-independent. since lps isolated from different bacterial species shows structural variability, studies were performed to determine whether differences in lps structure influence cd14-dependent a ... | 1999 | 10194066 |
| electron and proton transfer on the acceptor side of the reaction center in chromatophores of rhodobacter capsulatus: evidence for direct protonation of the semiquinone state of qb. | 1. the absorption changes associated with the formation of p+qbred (qbred stands for the semiquinone state of the secondary quinone acceptor) were investigated in chromatophores of rhodobacter capsulatus. marked modifications of the semiquinone spectrum were observed when the ph was lowered from 7 to 5. these modifications match those expected for a complete conversion of qbred from the anionic state qb- at ph 7 to the neutral protonated state qbh at ph 5. similar modifications were observed in ... | 1999 | 10194376 |
| lipopolysaccharide from an escherichia coli htrb msbb mutant induces high levels of mip-1 alpha and mip-1 beta secretion without inducing tnf-alpha and il-1 beta. | to identify a lipopolysaccharide (lps) that retains the capacity to induce beta-chemokine secretion without the concomitant activation of pyrogenic cytokines. | 1998 | 10195249 |
| a new cytochrome subunit bound to the photosynthetic reaction center in the purple bacterium, rhodovulum sulfidophilum. | the nucleotide sequence of the puf operon, which contains the genes encoding the b870 light-harvesting protein and the reaction center complex of the purple photosynthetic bacterium, rhodovulum sulfidophilum, was determined. the operon, which consisted of six genes, pufq, pufb, pufa, pufl, pufm, and pufc, is a new variety in photosynthetic bacteria in the sense that pufq and pufc coexist. the amino acid sequence of the cytochrome subunit of the reaction center deduced from the pufc sequence reve ... | 1999 | 10196154 |
| transcription activation by cooa, the co-sensing factor from rhodospirillum rubrum. the interaction between cooa and the c-terminal domain of the alpha subunit of rna polymerase. | cooa, a member of the camp receptor protein (crp) family, is a co-sensing transcription activator from rhodospirillum rubrum that binds specific dna sequences in response to co. the location of the cooa-binding sites relative to the start sites of transcription suggested that the cooa-dependent promoters are analogous to class ii crp-dependent promoters. in this study, we developed an in vivo cooa reporter system in escherichia coli and an in vitro transcription assay using rna polymerases (rnap ... | 1999 | 10196160 |
| isolation of helicobacter pylori genes that modulate urease activity. | helicobacter pylori urease, a nickel-requiring metalloenzyme, hydrolyzes urea to nh3 and co2. we sought to identify h. pylori genes that modulate urease activity by constructing php8080, a plasmid which encodes both h. pylori urease and the nixa nickel transporter. escherichia coli se5000 and dh5alpha transformed with php8080 resulted in a high-level urease producer and a low-level urease producer, respectively. an h. pylori dna library was cotransformed into se5000 (php8080) and dh5alpha (php80 ... | 1999 | 10198012 |
| the membrane-attached electron carrier cytochrome cy from rhodobacter sphaeroides is functional in respiratory but not in photosynthetic electron transfer. | rhodobacter species are useful model organisms for studying the structure and function of c type cytochromes (cyt c), which are ubiquitous electron carriers with essential functions in cellular energy and signal transduction. among these species, rhodobacter capsulatus has a periplasmic cyt c2rc and a membrane-bound bipartite cyt cyrc. these electron carriers participate in both respiratory and photosynthetic electron-transfer chains. on the other hand, until recently, rhodobacter sphaeroides wa ... | 1999 | 10200265 |
| distribution of atpase and atp-to-adp phosphate exchange activities in magnesium chelatase subunits of chlorobium vibrioforme and synechocystis pcc6803. | insertion of magnesium into protoporphyrin ix is a complex atp-dependent reaction catalysed by the enzyme mg-chelatase. three separate proteins (mg-chelatase subunits), designated as d, h and i, are involved in the chelation reaction. the genes encoding the mg-chelatase subunits of the green sulfur bacterium chlorobium vibrioforme and of the cyanobacterium synechocystis strain pcc6803 were expressed in escherichia coli. the recombinant proteins were purified, tested for atpase and phosphate exch ... | 1999 | 10201094 |
| effects of mutation of the conserved glutamic acid-286 in subunit i of cytochrome c oxidase from rhodobacter sphaeroides. | we have studied the effects of mutations, e286q and e286d, of the conserved glutamate in subunit i of cytochrome c oxidase from rhodobacter sphaeroides with a view to evaluating the role of this residue in redox-linked proton translocation. the mutation e286d did not have any dramatic effects on enzyme properties and retained 50% of wild-type catalytic activity. for e286q a fraction of the binuclear center was trapped in an unreactive, spectrally distinct form which is most likely due to misfold ... | 1999 | 10213633 |
| characterization of the photoreduction of the secondary quinone qb in the photosynthetic reaction center from rhodobacter capsulatus with ftir spectroscopy | the photoreduction of the secondary quinone acceptor qb in reaction centers (rcs) of the photosynthetic bacteria rhodobacter (rb.) capsulatus has been investigated by light-induced ftir difference spectroscopy in 1h2o and 2h2o. the q-b/qb ftir spectra reflect reorganization of the protein upon electron transfer, changes of protonation state of carboxylic acid groups, and (semi)quinone-protein interactions. as expected from the conservation of most of the amino acids near qb in the rcs from rb. c ... | 1999 | 10216167 |
| determination of the paracoccus denitrificans sos box. | by gel retardation experiments with crude cell extracts of paracoccus denitrificans it was demonstrated that a protein specifically binds to the promoter of the p. denitrificans reca gene. pcr mutagenesis of the reca promoter showed that the gaacn7gaac motif is required for the formation of the dna-protein complex. this protein also binds to the gttcn7gttc motif, which is present in the promoter of the p. denitrificans uvra gene. mutational analysis of the promoter regions of both p. denitrifica ... | 1999 | 10217491 |
| role of xdhc in molybdenum cofactor insertion into xanthine dehydrogenase of rhodobacter capsulatus. | rhodobacter capsulatus xanthine dehydrogenase (xdh) is composed of two subunits, xdha and xdhb. immediately downstream of xdhb, a third gene was identified, designated xdhc, which is cotranscribed with xdhab. interposon mutagenesis revealed that the xdhc gene product is required for xdh activity. however, xdhc is not a subunit of active xdh, which forms an alpha2beta2 heterotetramer in r. capsulatus. it was shown that xdhc neither is a transcriptional regulator for xdh gene expression nor influe ... | 1999 | 10217763 |
| the complete genome sequence of the streptomyces temperate phage straight phic31: evolutionary relationships to other viruses. | the completed genome sequence of the temperate streptomyces phage straight phic31 is reported. straight phic31 contains genes that are related by sequence similarities to several other dsdna phages infecting many diverse bacterial hosts, including escherichia, arthrobacter, mycobacterium, rhodobacter, staphylococcus, bacillus, streptococcus, lactobacillus and lactococcus. these observations provide further evidence that dsdna phages from diverse bacterial hosts are related and have had access to ... | 1999 | 10219087 |
| reorientation of the acetyl group of the photoactive bacteriopheophytin in reaction centers of rhodobacter sphaeroides: an endor/triple resonance study. | the freeze-trapped bacteriopheophytin alpha radical anion phi(*)a- has been investigated by 1h-endor/special triple resonance spectroscopy in photosynthetic reaction centers of rhodobacter sphaeroides, in which the tyr at position m210 had been replaced by either phe, leu, his or trp. in the wild type reaction center and the mutants yf(m210) and yw(m210) two distinct states of phi(*)a-, denoted i(*)1- and i(*)2-, can be stabilized below 200 k. the state i(*)1 is metastable and relaxes to i(*)2- ... | 1999 | 10219879 |
| anaerobic purification and characterization of nitrous oxide reductase from rhodobacter sphaeroides f. sp. denitrificans il106. | the nitrous oxide reductase from the photodenitrifier, rhodobacter sphaeroides f. sp. denitrificans il106, has been purified under anaerobic conditions. the specific activity of the enzyme was 78 micromol nitrous oxide reduced per min per mg protein, which was approximately 80% higher than that of the aerobic form. the enzyme purified anaerobically retained most of its activity after aerobic storage at 4 degrees c for 2 months without any additives. visible absorption spectra of the rhodobacter ... | 1999 | 10220576 |
| involvement in denitrification of the napkefdabc genes encoding the periplasmic nitrate reductase system in the denitrifying phototrophic bacterium rhodobacter sphaeroides f. sp. denitrificans. | seven genes, napkefdabc, encoding the periplasmic nitrate reductase system were cloned from the denitrifying phototrophic bacterium rhodobacter sphaeroides f. sp. denitrificans il106. two transmembrane proteins, napk and nape, an iron-sulfur protein napf, a soluble protein napd, a catalytic subunit of nitrate reductase precursor napa, a soluble c-type diheme cytochrome precursor napb, and a membrane-anchored c-type tetraheme cytochrome napc were deduced as the gene products. every mutant in whic ... | 1999 | 10227138 |
| fast reversible electron transfer for photosynthetic reaction center from wild type rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film. | direct reversible electron transfer for photosynthetic reaction center from wild type rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film was observed in this work. the redox potential e0' = 0.46 v vs. nhe for first primary donor redox couple p/p+ was accurately measured from reversible cv or swv peaks, which were quite close to those obtained from optic redox titration method. reaction center (rc) in film was found re-constituted in such an ordered way that the orient ... | 1999 | 10228576 |
| the phylogenetic relationships of caulobacter, asticcacaulis and brevundimonas species and their taxonomic implications. | the phylogenetic relationships among the species of caulobacter, asticcacaulis and brevundimonas were studied by comparison of their 16s rdna sequences. the analysis of almost complete sequences confirmed the early evolutionary divergence of the freshwater and marine species of caulobacter reported previously [stahl, d. a., key, r., flesher, b. & smit, j. (1992). j bacteriol 174, 2193-2198]. the freshwater species formed two distinct clusters. one cluster contained the species caulobacter bacter ... | 1999 | 10319468 |
| investigation on the detergent role in the function of secondary quinone in bacterial reaction centers. | in this paper are reported studies on the detergent role in isolated reaction centers (rc) from rhodobacter sphaeroides, over a large range of lauryldimethylamino-n-oxide (ldao) concentrations, in influencing the thermodynamics of the quinone exchange reaction as well as the protein aggregation. the occurrence of the quinone exchange reaction between the qb-binding site (where qb is the second quinone molecule of two in the rc) and the ubiquinone 0 dissolved in the different environments (water, ... | 1999 | 10336619 |
| bacteriochlorin-protein interactions in native b800-b850, b800 deficient and b800-bchla(p)-reconstituted complexes from rhodopseudomonas acidophila, strain 10050. | recently, a method which allows the selective release and removal of the 800 nm absorbing bacteriochlorophyll a (b800) molecules from the lh2 complex of rhodopseudomonas acidophila strain 10050 has been described [fraser, n.j. (1999) ph.d. thesis, university of glasgow, uk]. this procedure also allows the reconstitution of empty binding sites with the native pigment bchla(p), esterified with phytol. we have investigated the bacteriochlorophylla-protein interactions in native, b800 deficient (or ... | 1999 | 10338146 |
| identification of the proton pathway in bacterial reaction centers: inhibition of proton transfer by binding of zn2+ or cd2+. | the reaction center (rc) from rhodobacter sphaeroides converts light into chemical energy through the light induced two-electron, two-proton reduction of a bound quinone molecule qb (the secondary quinone acceptor). a unique pathway for proton transfer to the qb site had so far not been determined. to study the molecular basis for proton transfer, we investigated the effects of exogenous metal ion binding on the kinetics of the proton-assisted electron transfer kab(2) (qa-*qb-* + h+ --> qa(qbh)- ... | 1999 | 10339562 |
| the molybdenum cofactor biosynthesis protein moba from rhodobacter capsulatus is required for the activity of molybdenum enzymes containing mgd, but not for xanthine dehydrogenase harboring the mpt cofactor. | the requirement of moba for molybdoenzymes with different molybdenum cofactors was analyzed in rhodobacter capsulatus. moba is essential for dmso reductase and nitrate reductase activity, both enzymes containing the molybdopterin guanine dinucleotide cofactor (mgd), but not for active xanthine dehydrogenase, harboring the molybdopterin cofactor. in contrast to the mob locus of escherichia coli and r. sphaeroides, the mobb gene is not located downstream of moba in r. capsulatus. the moba gene is ... | 1999 | 10339814 |
| aspartate-132 in cytochrome c oxidase from rhodobacter sphaeroides is involved in a two-step proton transfer during oxo-ferryl formation. | the aspartate-132 in subunit i (d(i-132)) of cytochrome c oxidase from rhodobacter sphaeroides is located on the cytoplasmic surface of the protein at the entry point of a proton-transfer pathway used for both substrate and pumped protons (d-pathway). replacement of d(i-132) by its nonprotonatable analogue asparagine (dn(i-132)) has been shown to result in a reduced overall activity of the enzyme and impaired proton pumping. the results from this study show that during oxidation of the fully red ... | 1999 | 10346904 |
| the reaction center-lh1 antenna complex of rhodobacter sphaeroides contains one pufx molecule which is involved in dimerization of this complex. | the pufx membrane protein is essential for photosynthetic growth of rhodobacter sphaeroides wild-type cells. pufx is associated with the reaction center-light harvesting 1 (rc-lh1) core complex and plays a key role in lateral ubiquinone/ubiquinol transfer. we have determined the pufx/rc stoichiometry by quantitative western blot analysis and rc photobleaching. independent of copy number effects and growth conditions, one pufx molecule per rc was observed in native membranes as well as in deterge ... | 1999 | 10346905 |
| autophosphorylation, phosphotransfer, and dna-binding properties of the regb/rega two-component regulatory system in rhodobacter capsulatus. | in the purple, photosynthetic bacterium, rhodobacter capsulatus, the regb/rega two-component system is required for activation of several anaerobic processes, such as synthesis of the photosynthetic apparatus and assimilation of co2 and n2. it is believed that regb is an integral membrane histidine kinase that monitors the external environment. under anaerobic growth conditions, it transduces a signal through phosphorylation of the response regulator, rega, which then induces target gene express ... | 1999 | 10347192 |
| cytochrome c" from the obligate methylotroph methylophilus methylotrophus, an unexpected homolog of sphaeroides heme protein from the phototroph rhodobacter sphaeroides. | the complete primary structure of an unusual soluble cytochrome c isolated from the obligate methylotrophic bacterium methylophilus methylotrophus has been determined to contain 124 amino acids and to have an average molecular mass of 14293.0 da. the sequence has two unusual features: firstly, the location of the heme-binding cysteines is far downstream from the n-terminus, namely at positions 49 and 52; secondly, an extra pair of cysteine residues is present near the c-terminus. in both respect ... | 1999 | 10354493 |
| topological analysis of the membrane-localized redox-responsive sensor kinase prrb from rhodobacter sphaeroides 2.4.1. | photosynthesis gene expression in rhodobacter sphaeroides is controlled in part by the two-component (prr) regulatory system composed of a membrane-bound sensor kinase (prrb) and a response regulator (prra). hydropathy profile-based computer analysis predicted that the prrb polypeptide could contain six membrane-spanning domains at its amino terminus and a hydrophilic, cytoplasmic carboxyl terminus. both the localization and the topology of the prrb sensor kinase have been studied by generating ... | 1999 | 10358089 |
| primary charge separation routes in the bchl:bphe heterodimer reaction centers of rhodobacter sphaeroides. | energy transfer and the primary charge separation process are studied as a function of excitation wavelength in membrane-bound reaction centers of rhodobacter sphaeroides in which the excitonically coupled bacteriochlorophyll homodimer is converted to a bacteriochlorophyll-bacteriopheophytin heterodimer, denoted d [bylina, e. j., and youvan, d. c. (1988) proc. natl. acad. sci. u.s. a. 85, 7226]. in the hm202l heterodimer reaction center, excitation of d using 880 nm excitation light results in a ... | 1999 | 10360952 |
| time for a fresh look at the bacterial chromosome. | | 1999 | 10366858 |
| a six-stranded double-psi beta barrel is shared by several protein superfamilies. | six-stranded beta barrels with a pseudo-twofold axis are found in several proteins. one group comprises a greek-key structure with all strands antiparallel; an example is the n-terminal domain of ferredoxin reductase. others involve parallel strands forming two psi structures (the double-psi beta barrel). a recently discovered example of the latter class is aspartate-alpha-decarboxylase (adc) from escherichia coli, a pyruvoyl-dependent tetrameric enzyme involved in the synthesis of pantothenate. | 1999 | 10368289 |
| biomass monitoring using impedance spectroscopy. | the biomass density in biotechnological processes is often determined by indirect and manual methods. electrical impedance spectroscopy can provide online viable biomass density estimators. in this work, we present two linear estimators obtained with this technique. four different microorganisms were measured. the detection threshold was approximately 1 g/l (dry weight) for bacteria and 0.5 g/l for yeast. liposome suspensions were also used to validate the methods. the monitoring of the continuo ... | 1999 | 10372178 |
| energy level of p+b- with respect to p* found from recombination fluorescence measurements in pheophytin-modified reaction centres. | recent studies of reaction centres from rhodobacter sphaeroides (r-26), in which bacteriopheophytins a were replaced by plant pheophytins a, have shown that at low temperature the excited state of primary electron donor p* is converted to the state p+b-(a) (where b(a) is a bacteriochlorophyll a monomer in branch a) which has a long lifetime (about 600 ps [8]). this allows the direct measurement of the free energy difference between p* and p+b-(a) using the temperature dependence of the recombina ... | 1998 | 10379640 |
| effect of deuteration and cryosolvents on the energy transduction in primary processes of photosynthesis. | effects of cryosolvents and d2o/h2o substitution on the reaction centres (rcs) isolated from photosynthetic bacteria were studied with respect to the role of intra-protein hydrogen bonds in the primary photosynthetic electron transfer. as a result of such treatment of rcs, the charge separation rate between the photoactive bacteriochlorophyll (p2 dimer) and bacteriopheophytin and the rate of electron transfer to the primary quinone slowed down. the energy migration rate from bacteriopheophytin ( ... | 1998 | 10379643 |
| how photosynthetic bacteria harvest solar energy. | | 1999 | 10383951 |
| the "green" form i ribulose 1,5-bisphosphate carboxylase/oxygenase from the nonsulfur purple bacterium rhodobacter capsulatus. | form i ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) of the calvin-benson-bassham cycle may be divided into two broad phylogenetic groups, referred to as red-like and green-like, based on deduced large subunit amino acid sequences. unlike the form i enzyme from the closely related organism rhodobacter sphaeroides, the form i rubisco from r. capsulatus is a member of the green-like group and closely resembles the enzyme from certain chemoautotrophic proteobacteria and cyanobacteria. a ... | 1999 | 10383960 |
| the structure of chromatophores from purple photosynthetic bacteria fused with lipid-impregnated collodion films determined by near-field scanning optical microscopy. | lipid-impregnated collodion (nitrocellulose) films have been frequently used as a fusion substrate in the measurement and analysis of electrogenic activity in biological membranes and proteoliposomes. while the method of fusion of biological membranes or proteoliposomes with such films has found a wide application, little is known about the structures formed after the fusion. yet, knowledge of this structure is important for the interpretation of the measured electric potential. to characterize ... | 1999 | 10386595 |
| substitution of the sixth axial ligand of rhodobacter capsulatus cytochrome c1 heme yields novel cytochrome c1 variants with unusual properties. | the cytochrome (cyt) c1 heme of the ubihydroquinone:cytochrome c oxidoreductase (bc1 complex) is covalently attached to two cysteine residues of the cyt c1 polypeptide chain via two thioether bonds, and the fifth and sixth axial ligands of its iron atom are histidine (h) and methionine (m), respectively. the latter residue is m183 in rhodobacter capsulatus cyt c1, and previous mutagenesis studies revealed its critical role for the physicochemical properties of cyt c1 [gray, k. a., davidson, e., ... | 1999 | 10387032 |
| calculated protein and proton motions coupled to electron transfer: electron transfer from qa- to qb in bacterial photosynthetic reaction centers. | reaction centers from rhodobacter sphaeroides were subjected to monte carlo sampling to determine the boltzmann distribution of side-chain ionization states and positions and buried water orientation and site occupancy. changing the oxidation states of the bacteriochlorophyll dimer electron donor (p) and primary (qa) and secondary (qb) quinone electron acceptors allows preparation of the ground (all neutral), p+qa-, p+qb-, p0qa-, and p0qb- states. the calculated proton binding going from ground ... | 1999 | 10387071 |
| reactions of dimethylsulfoxide reductase from rhodobacter capsulatus with dimethyl sulfide and with dimethyl sulfoxide: complexities revealed by conventional and stopped-flow spectrophotometry. | improved assays for the molybdenum enzyme dimethylsulfoxide reductase (dmsor) with dimethyl sulfoxide (dmso) and with dimethyl sulfide (dms) as substrates are described. maximum activity was observed at ph 6.5 and below and at 8.3, respectively. rapid-scan stopped-flow spectrophotometry has been used to investigate the reduction of the enzyme by dms to a species previously characterized by its uv-visible spectrum [mcalpine, a. s., mcewan, a. g., and bailey, s. (1998) j. mol. biol. 275, 613-623], ... | 1999 | 10387097 |
| the lhialpha and lhiialpha complexes in association with phospholipids are able to be inserted in heavy membranes of rhodobacter capsulatus b10. | we show in this paper that a complex constituted by phospholipids and lhi and lhii alpha polypeptides was inserted in a heavy membrane fraction in a nonextractable form, indicating a transmembrane localization. the best accepting membranes originated from aerobically grown cells. addition of atp during the insertion inhibited this reaction 25 to 30% in heavy membranes isolated from aerobically grown cells (hmaer) and a higher inhibition (60 to 65%) was detected when using heavy membranes isolate ... | 1999 | 10387115 |
| photosynthetic bradyrhizobia from aeschynomene spp. are specific to stem-nodulated species and form a separate 16s ribosomal dna restriction fragment length polymorphism group. | we obtained nine bacterial isolates from root or collar nodules of the non-stem-nodulated aeschynomene species a. elaphroxylon, a. uniflora, or a. schimperi and 69 root or stem nodule isolates from the stem-nodulated aeschynomene species a. afraspera, a. ciliata, a. indica, a. nilotica, a. sensitiva, and a. tambacoundensis from various places in senegal. these isolates, together with 45 previous isolates from various aeschynomene species, were studied for host-specific nodulation within the genu ... | 1999 | 10388707 |
| phylogenetic analysis of particle-attached and free-living bacterial communities in the columbia river, its estuary, and the adjacent coastal ocean. | the columbia river estuary is a dynamic system in which estuarine turbidity maxima trap and extend the residence time of particles and particle-attached bacteria over those of the water and free-living bacteria. particle-attached bacteria dominate bacterial activity in the estuary and are an important part of the estuarine food web. pcr-amplified 16s rrna genes from particle-attached and free-living bacteria in the columbia river, its estuary, and the adjacent coastal ocean were cloned, and 239 ... | 1999 | 10388721 |
| uphill energy transfer in lh2-containing purple bacteria at room temperature | uphill energy transfer in the lh2-containing purple bacteria rhodopseudomonas acidophila, rhodopseudomonas palustris, rhodobacter sphaeroides, chromatium vinosum and chromatium purpuratum was studied by stationary fluorescence spectroscopy at room temperature upon selective excitation of the b800 pigments of lh2 and the b880 pigments of lh1 at 803 nm and 900 nm, respectively. the resulting fluorescence spectra differed significantly at wavelengths shorter than the fluorescence maximum but agreed ... | 1999 | 10393258 |
| p+ha- charge recombination reaction rate constant in rhodobacter sphaeroides reaction centers is independent of the p/p+ midpoint potential. | the kinetics of the p+ha- (oxidized donor, reduced bacteriopheophytin acceptor) recombination reaction was measured in a series of reaction center mutants of rhodobacter sphaeroides with altered p/p+ midpoint potentials between 410 and 765 mv. the time constant for p+ha- recombination was found to range between 14 and 26 ns and was essentially independent of p/p+ midpoint potential. previous work has shown that the time constant for initial electron transfer in these mutants at room temperature ... | 1999 | 10393555 |
| characterisation of the enzymatic and rna-binding properties of the rhodobacter sphaeroides 2.4.1. rho homologue. | the escherichia coli rho is a transcription termination factor with complex enzymatic properties. rho is a near-universal prokaryotic transcription factor, but very few non-enteric rho factors have been studied. the expression and enzymatic activity of rho from the gc-rich, gram-negative bacterium rhodobacter sphaeroides was characterised. poly(c)-activated atp hydrolysis, multimerisation and the abundance of the r. sphaeroides rho were similar to the e. coli rho. the r. sphaeroides rho was a dn ... | 1999 | 10395924 |
| structural and functional analyses of photosynthetic regulatory genes rega and regb from rhodovulum sulfidophilum, roseobacter denitrificans, and rhodobacter capsulatus. | genes coding for putative rega, regb, and senc homologues were identified and characterized in the purple nonsulfur photosynthetic bacteria rhodovulum sulfidophilum and roseobacter denitrificans, species that demonstrate weak or no oxygen repression of photosystem synthesis. this additional sequence information was then used to perform a comparative analysis with previously sequenced rega, regb, and senc homologues obtained from rhodobacter capsulatus and rhodobacter sphaeroides. these are photo ... | 1999 | 10400577 |
| heterologous expression of correctly assembled methylamine dehydrogenase in rhodobacter sphaeroides. | the biosynthesis of methylamine dehydrogenase (madh) from paracoccus denitrificans requires four genes in addition to those that encode the two structural protein subunits, maub and maua. the accessory gene products appear to be required for proper export of the protein to the periplasm, synthesis of the tryptophan tryptophylquinone (ttq) prosthetic group, and formation of several structural disulfide bonds. to accomplish the heterologous expression of correctly assembled madh, eight genes from ... | 1999 | 10400578 |
| regulated expression of a highly conserved regulatory gene cluster is necessary for controlling photosynthesis gene expression in response to anaerobiosis in rhodobacter capsulatus. | we utilized primer extension analysis to demonstrate that the divergently transcribed regb and senc-rega-hvra transcripts contain stable 5' ends 43 nucleotides apart within the regb-senc intergenic region. dna sequence analysis indicates that this region contains two divergent promoters with overlapping sigma70 type -35 and -10 promoter recognition sequences. in vivo analysis of expression patterns of regb::lacz and senc-rega-hvra::lacz reporter gene fusions demonstrates that the regb and senc-r ... | 1999 | 10400592 |
| the role of the rdxa gene in the evolution of metronidazole resistance in helicobacter pylori. | it was recently demonstrated that inactivation of the rdxa gene, which encodes an oxygen-insensitive nadph nitroreductase, is associated with the development of resistance to metronidazole by helicobacter pylori. in order to further evaluate the contribution of rdxa to metronidazole resistance, the sequence of the rdxa gene was determined for a series of metronidazole-sensitive and -resistant isolates derived from a single, metronidazole-sensitive strain using an h. pylori mouse model. these str ... | 1999 | 10404313 |
| a novel mechanism for the regulation of photosynthesis gene expression by the tspo outer membrane protein of rhodobacter sphaeroides 2.4.1. | a bacterial homolog of the mammalian mitochondrial benzodiazepine receptor, the tryptophan-rich sensory protein (tspo) has been previously demonstrated to negatively affect the transcriptional expression of several photosynthesis genes of rhodobacter sphaeroides. to identify components of the signal transduction pathway from the outer membrane-localized tspo to the dna-active transcription factor(s), we examined the involvement of tspo in the regulation of tetrapyrrole metabolism in r. sphaeroid ... | 1999 | 10409680 |
| mutational analysis of the dimethylsulfoxide respiratory (dor) operon of rhodobacter capsulatus. | four genes, dorc, dord, dorb and dorr of the dmso respiratory gene cluster of rhodobacter capsulatus have been identified and sequenced. dorc encodes a pentahaem c-type cytochrome of the nirt class and the derived dorc protein sequence shows highest similarity to torc from the escherichia coli trimethylamine-n-oxide (tmao) respiratory system. mutagenesis of dorc resulted in the loss of a 46 kda haem-staining polypeptide from membranes of r. capsulatus. dord encodes a protein with highest sequenc ... | 1999 | 10411268 |
| characterization of a molybdenum cofactor biosynthetic gene cluster in rhodobacter capsulatus which is specific for the biogenesis of dimethylsulfoxide reductase. | the dmso reductase of rhodobacter capsulatus contains a pterin molybdenum cofactor (moco) and is located in the periplasm. dna sequence analysis identified four genes involved in the biosynthesis of the moco (moaa, moad, moeb and moac) immediately downstream of the dor (dmso respiratory) gene cluster. rhodobacter capsulatus moaa was expressed in escherichia coli as a his6-tagged protein. although, the expressed protein formed inclusion bodies, epr spectroscopy showed that moaa contains a [3fe-4s ... | 1999 | 10411269 |
| in vitro activation and repression of photosynthesis gene transcription in rhodobacter capsulatus. | it has been known for over half a century that anoxygenic photosynthetic bacteria maximally synthesize their photosystems in the absence of oxygen. during the last decade, it has become clear that this regulation is largely at the transcriptional level, with photosynthesis genes expressed only under anaerobic conditions. we describe here in vitro reconstitution of activation and repression of three photosynthesis promoters, bch (bacteriochlorophyll biosynthesis), puc (light-harvesting ii apoprot ... | 1999 | 10411758 |
| primary charge separation routes in the bchl:bphe heterodimer reaction centers of rhodobacter sphaeroides. | | 1999 | 10413534 |
| comparative sequence analysis of the dna packaging, head, and tail morphogenesis modules in the temperate cos-site streptococcus thermophilus bacteriophage sfi21. | the temperate streptococcus thermophilus bacteriophage sfi21 possesses 15-nucleotide-long cohesive ends with a 3' overhang that reconstitutes a cos-site with twofold hyphenated rotational symmetry. over the dna packaging, head and tail morphogenesis modules, the sfi21 sequence predicts a gene map that is strikingly similar to that of lambdoid coliphages in the absence of any sequence similarity. a nearly one to one gene correlation was found with the phage lambda genes nu1 to h, except for gene ... | 1999 | 10417259 |
| selective release, removal, and reconstitution of bacteriochlorophyll a molecules into the b800 sites of lh2 complexes from rhodopseudomonas acidophila 10050. | a method is described which allows the selective release and removal of the bchla-b800 molecules from the lh2 complex of rhodopseudomonas acidophila 10050. this procedure also allows reconstitution of approximately 80% of the empty binding sites with native bchla. as shown by circular dichroism spectroscopy, the overall structures of the b850-only and reconstituted complexes are not affected by the pigment-exchange procedure. the pigments reconstituted into the b800 sites can also efficiently tr ... | 1999 | 10423247 |
| transformations in flagellar structure of rhodobacter sphaeroides and possible relationship to changes in swimming speed. | rhodobacter sphaeroides is a photosynthetic bacterium which swims by rotating a single flagellum in one direction, periodically stopping, and reorienting during these stops. free-swimming r. sphaeroides was examined by both differential interference contrast (dic) microscopy, which allows the flagella of swimming cells to be seen in vivo, and tracking microscopy, which tracks swimming patterns in three dimensions. dic microscopy showed that when rotation stopped, the helical flagellum relaxed in ... | 1999 | 10438751 |
| transcript cleavage, attenuation, and an internal promoter in the rhodobacter capsulatus puc operon. | the stoichiometry of the structural proteins of the photosynthetic apparatus in purple photosynthetic bacteria is achieved primarily by complex regulation of the levels of mrna encoding the different proteins, which has been studied in the greatest detail in the puf operon. here we investigated the transcriptional and posttranscriptional regulation of the puc operon, which encodes the peripheral light harvesting complex lhii. we show that, analogous to the puf operon, a primary transcript encodi ... | 1999 | 10438767 |
| cloning and mapping of the cdna for human sarcosine dehydrogenase, a flavoenzyme defective in patients with sarcosinemia. | sarcosine dehydrogenase is a liver mitochondrial matrix flavoenzyme that is defective in patients with sarcosinemia, a rare autosomal metabolic defect characterized by elevated levels of sarcosine in blood and urine. some patients also exhibit mental retardation and growth failure. a full-length cdna for human sarcosine dehydrogenase was isolated from an adult liver cdna library. the first 22 residues in the deduced amino acid sequence exhibit features expected for a mitochondrial targeting sequ ... | 1999 | 10444331 |
| simulating proton translocations in proteins: probing proton transfer pathways in the rhodobacter sphaeroides reaction center. | a general method for simulating proton translocations in proteins and for exploring the role of different proton transfer pathways is developed and examined. the method evaluates the rate constants for proton transfer processes using the energetics of the relevant proton configurations. the energies (deltag((m))) of the different protonation states are evaluated in two steps. first, the semimicroscopic version of the protein dipole langevin dipole (pdld/s) method is used to evaluate the intrinsi ... | 1999 | 10450091 |
| a human putative suv3-like rna helicase is conserved between rhodobacter and all eukaryotes. | we have cloned and sequenced a cdna of the human homologue of the saccharomyces cerevisiae suv3 putative rna helicase which is indispensable for mitochondrial function in yeast. the human suv-3-like protein has a typical mitochondrial leader sequence. northern blot data and analysis of ests in the data banks indicate that this human gene (supv3l1) is expressed in practically all tissues, though at different levels. sequence homology analysis has shown a strong conservation of the protein in a nu ... | 1999 | 10453991 |
| pseudomonas aeruginosa exoenzyme s stimulates murine lymphocyte proliferation in vitro. | the exuberant immunoinflammatory response that is associated with pseudomonas aeruginosa infection is the major source of the morbidity and mortality in cystic fibrosis (cf) patients. previous studies have established that an exoproduct of p. aeruginosa (exoenzyme s) is a mitogen for human t lymphocytes and activates a larger percentage of t cells than most superantigens, which may contribute to the immunoinflammatory response. an animal model would facilitate studies of the pathophysiologic con ... | 1999 | 10456907 |
| conformation of bacteriochlorophyll molecules in photosynthetic proteins from purple bacteria. | fourier transform near-infrared resonance raman spectroscopy can be used to obtain information on the bacteriochlorophyll a (bchl a) molecules responsible for the redmost absorption band in photosynthetic complexes from purple bacteria. this technique is able to distinguish distortions of the bacteriochlorin macrocycle as small as 0.02 a, and a systematic analysis of those vibrational modes sensitive to bchl a macrocycle conformational changes was recently published [näveke et al. (1997) j. rama ... | 1999 | 10460167 |
| an engineered cytochrome b6c1 complex with a split cytochrome b is able to support photosynthetic growth of rhodobacter capsulatus. | the ubihydroquinone-cytochrome c oxidoreductase (or the cytochrome bc1 complex) from rhodobacter capsulatus is composed of the fe-s protein, cytochrome b, and cytochrome c1 subunits encoded by peta(fbcf), petb(fbcb), and petc(fbcc) genes organized as an operon. in the work reported here, petb(fbcb) was split genetically into two cistrons, petb6 and petbiv, which encoded two polypeptides corresponding to the four amino-terminal and four carboxyl-terminal transmembrane helices of cytochrome b, res ... | 1999 | 10464208 |
| helix packing in polytopic membrane proteins: role of glycine in transmembrane helix association. | the nature and distribution of amino acids in the helix interfaces of four polytopic membrane proteins (cytochrome c oxidase, bacteriorhodopsin, the photosynthetic reaction center of rhodobacter sphaeroides, and the potassium channel of streptomyces lividans) are studied to address the role of glycine in transmembrane helix packing. in contrast to soluble proteins where glycine is a noted helix breaker, the backbone dihedral angles of glycine in transmembrane helices largely fall in the standard ... | 1999 | 10465772 |
| pathways for proton release during ubihydroquinone oxidation by the bc(1) complex. | quinol oxidation by the bc(1) complex of rhodobacter sphaeroides occurs from an enzyme-substrate complex formed between quinol bound at the q(o) site and the iron-sulfur protein (isp) docked at an interface on cytochrome b. from the structure of the stigmatellin-containing mitochondrial complex, we suggest that hydrogen bonds to the two quinol hydroxyl groups, from glu-272 of cytochrome b and his-161 of the isp, help to stabilize the enzyme-substrate complex and aid proton release. reduction of ... | 1999 | 10468555 |
| observation of the protonated semiquinone intermediate in isolated reaction centers from rhodobacter sphaeroides: implications for the mechanism of electron and proton transfer in proteins. | a proton-activated electron transfer (paet) mechanism, involving a protonated semiquinone intermediate state, had been proposed for the electron-transfer reaction k(2)ab [q(a)(-)(*)q(b)(-)(*) + h(+) <--> q(a)(-)(*)(q(b)h)(*) --> q(a)(q(b)h)(-)] in reaction centers (rcs) from rhodobacter sphaeroides [graige, m. s., paddock, m. l., bruce, m. l., feher, g., and okamura, m. y. (1996) j. am. chem. soc. 118, 9005-9016]. confirmation of this mechanism by observing the protonated semiquinone (q(b)h)(*) ... | 1999 | 10471298 |
| m-side electron transfer in reaction center mutants with a lysine near the nonphotoactive bacteriochlorophyll. | we report the primary charge separation events in a series of rhodobacter capsulatus reaction centers (rcs) that have been genetically modified to contain a lysine near the bacteriochlorophyll molecule, bchl(m), on the nonphotoactive m-side of the rc. using wild type and previously constructed mutants as templates, we substituted lys for the native ser residue at position 178 on the l polypeptide to make the s(l178)k single mutant, the s(l178)k/g(m201)d and s(l178)k/l(m212)h double mutants, and ... | 1999 | 10471304 |
| detection of genes for periplasmic nitrate reductase in nitrate respiring bacteria and in community dna. | a nested pcr primed by four degenerate oligonucleotides was developed for the specific amplification of sequences from the napa gene encoding the periplasmic nitrate reductase. this approach was used to amplify fragments of the napa gene from 10 pseudomonas species and one moraxella sp., previously shown to be able to express the periplasmic nitrate reductase activity, from rhodobacter capsulatus and from community dna extracted from a fresh-water sediment. amino acid sequences encoded by the na ... | 1999 | 10474192 |
| regulation of bacterial photosynthesis genes by oxygen and light. | most bacteria have the capability to adapt to changes in their environment. facultatively phototrophic bacteria like rhodobacter can switch from aerobic respiration to anoxygenic photosynthesis in the absence of oxygen. the formation of the photosynthetic apparatus is primarily regulated by oxygen tension. the amount of photosynthetic complexes is influenced by the light intensity in anaerobic cultures. this review focuses on the molecular mechanisms involved in the regulation of rhodobacter pho ... | 1999 | 10481079 |
| inactivation and regulation of the aerobic c(4)-dicarboxylate transport (dcta) gene of escherichia coli. | the gene (dcta) encoding the aerobic c(4)-dicarboxylate transporter (dcta) of escherichia coli was previously mapped to the 79-min region of the linkage map. the nucleotide sequence of this region reveals two candidates for the dcta gene: f428 at 79.3 min and the o157a-o424-o328 (or orfqmp) operon at 79.9 min. the f428 gene encodes a homologue of the sinorhizobium meliloti and rhizobium leguminosarum h(+)/c(4)-dicarboxylate symporter, dcta, whereas the orfqmp operon encodes homologues of the aer ... | 1999 | 10482502 |
| characterization of the rhodobacter sphaeroides 5-aminolaevulinic acid synthase isoenzymes, hema and hemt, isolated from recombinant escherichia coli. | the hema and hemt genes encoding 5-aminolaevulinic acid synthase (alas) from the photosynthetic bacterium rhodobacter sphaeroides, were cloned to allow high expression in escherichia coli. both hema and hemt appeared to be active in vivo as plasmids carrying the respective genes complemented an e. coli hema strain (glutamyl-trna reductase deficient). the over-expressed isoenzymes were isolated and purified to homogeneity. isolated hema was soluble and catalytically active whereas hemt was largel ... | 1999 | 10491185 |
| immunogenicity of outer membrane proteins in a lipopolysaccharide-deficient mutant of neisseria meningitidis: influence of adjuvants on the immune response. | the immunogenicity of outer membrane complexes (omcs) or heat-inactivated bacteria of a lipopolysaccharide (lps)-deficient mutant derived from meningococcal strain h44/76 was studied. the immune response in balb/c mice to the major outer membrane proteins was poor compared to the immune response elicited by wild-type immunogens. however, addition of external h44/76 lps to mutant omcs entirely restored the immune response. by using an lps-deficient mutant, it may be possible to substitute a less ... | 1999 | 10496868 |
| activity of the molybdopterin-containing xanthine dehydrogenase of rhodobacter capsulatus can be restored by high molybdenum concentrations in a moea mutant defective in molybdenum cofactor biosynthesis. | during the screening for rhodobacter capsulatus mutants defective in xanthine degradation, one tn5 mutant which was able to grow with xanthine as a sole nitrogen source only in the presence of high molybdate concentrations (1 mm), a phenotype resembling escherichia coli moga mutants, was identified. unexpectedly, the corresponding tn5 insertion was located within the moea gene. partial dna sequence analysis and interposon mutagenesis of regions flanking r. capsulatus moea revealed that no furthe ... | 1999 | 10498704 |
| nitrite and nitrous oxide reductase regulation by nitrogen oxides in rhodobacter sphaeroides f. sp. denitrificans il106. | we have cloned the nap locus encoding the periplasmic nitrate reductase in rhodobacter sphaeroides f. sp. denitrificans il106. a mutant with this enzyme deleted is unable to grow under denitrifying conditions. biochemical analysis of this mutant shows that in contrast to the wild-type strain, the level of synthesis of the nitrite and n(2)o reductases is not increased by the addition of nitrate. growth under denitrifying conditions and induction of n oxide reductase synthesis are both restored by ... | 1999 | 10498715 |
| identification of mycobacterium tuberculosis rnas synthesized in response to phagocytosis by human macrophages by selective capture of transcribed sequences (scots). | a widely applicable, positive cdna selection method was developed to identify rnas synthesized by mycobacterium tuberculosis in response to phagocytosis by cultured human primary macrophages. cdnas for sige and sigh (alternative sigma factors), acea (isocitrate lyase), pona (class i penicillin-binding protein), pks2 (polyketide synthase), uvra (uvrabc endonuclease), and ctpv (putative cation transporter) were obtained from macrophage-grown bacteria. cdnas for orfs rv3070, rv3483c, rv0903c (encod ... | 1999 | 10500215 |
| site-directed mutagenesis of the response regulator dmsr for the dmscba operon expression in rhodobacter sphaeroides f. sp. denitrificans: an essential residue of proline-130 in the linker. | dmsr protein is a member of the ompr response regulator subfamily that activates the transcription of the dmscba operon in rhodobacter sphaeroides f. sp. denitrificans. by site-directed mutagenesis some functional amino acid residues were investigated in dmsr, which consists of the n-terminal regulatory and the c-terminal dna-binding domains and the linker connecting the two domains. the substitution of p130s in the linker caused decreases of both dna-binding and transcriptional activator activi ... | 1999 | 10500244 |
| regulation of divergent transcription from the uvra-ssb promoters in sinorhizobium meliloti. | the sinorhizobium meliloti uvra gene was isolated by complementation of a rhodobacter sphaeroides uvra- mutant. dna sequencing of the region upstream of the s. meliloti uvra gene reveals the presence of the ssb gene in the opposite transcriptional orientation. pcr-mediated mutagenesis demonstrated that expression of these two genes is inducible by dna damage, and depends, in both cases, on the direct repeat gttcn7gttc (cited according to the direction of uvra transcription). comparison of the se ... | 1999 | 10503543 |
| excited-state electronic asymmetry of the special pair in photosynthetic reaction center mutants: absorption and stark spectroscopy. | the electronic absorption line shape and stark spectrum of the lowest energy q(y)() transition of the special pair in bacterial reaction centers contain a wealth of information on mixing with charge transfer states and electronic asymmetry. both vary greatly in mutants that perturb the chemical composition of the special pair, such as the heterodimer mutants, and in mutants that alter interactions between the special pair and the surrounding reaction center protein, such as those that add or rem ... | 1999 | 10508398 |
| multiple chromosomes in bacteria. the yin and yang of trp gene localization in rhodobacter sphaeroides 2.4.1. | the existence of multiple chromosomes in bacteria has been known for some time. yet the extent of functional solidarity between different chromosomes remains unknown. to examine this question, we have surveyed the well-described genes of the tryptophan biosynthetic pathway in the multichromosomal photosynthetic eubacterium rhodobacter sphaeroides 2.4.1. the genome of this organism was mutagenized using tn5, and strains that were auxotrophic for tryptophan (trp(-)) were isolated. pulsed-field gel ... | 1999 | 10511537 |
| electron paramagnetic resonance studies of zinc-substituted reaction centers from rhodopseudomonas viridis. | the primary quinone acceptor radical anion q(a)(-)(*) (a menaquinone-9) is studied in reaction centers (rcs) of rhodopseudomonas viridis in which the high-spin non-heme fe(2+) is replaced by diamagnetic zn(2+). the procedure for the iron substitution, which follows the work of debus et al. [debus, r. j., feher, g., and okamura, m. y. (1986) biochemistry 25, 2276-2287], is described. in rps. viridisan exchange rate of the iron of approximately 50% +/- 10% is achieved. time-resolved optical spectr ... | 1999 | 10512634 |
| hybrid motor with h(+)- and na(+)-driven components can rotate vibrio polar flagella by using sodium ions. | the bacterial flagellar motor is a molecular machine that converts ion flux across the membrane into flagellar rotation. the coupling ion is either a proton or a sodium ion. the polar flagellar motor of the marine bacterium vibrio alginolyticus is driven by sodium ions, and the four protein components, poma, pomb, motx, and moty, are essential for motor function. among them, poma and pomb are similar to mota and motb of the proton-driven motors, respectively. poma shows greatest similarity to mo ... | 1999 | 10515922 |
| sulfide-quinone reductase from rhodobacter capsulatus: requirement for growth, periplasmic localization, and extension of gene sequence analysis. | the entire sequence of the 3.5-kb fragment of genomic dna from rhodobacter capsulatus which contains the sqr gene and a second complete and two further partial open reading frames has been determined. a correction of the previously published sqr gene sequence (m. schütz, y. shahak, e. padan, and g. hauska, j. biol. chem. 272:9890-9894, 1997) which in the deduced primary structure of the sulfide-quinone reductase changes four positive into four negative charges and the number of amino acids from ... | 1999 | 10515944 |
| cloning and sequence analysis of the gene encoding methylophilus methylotrophus cytochrome c", a unique protein with a perpendicular orientation of the histidinyl ligands. | cytochrome c" from methylophilus methylotrophus is an unusual monohaem protein that undergoes a major redox-linked spin-state transition: one of the two axial histidines bound to the iron in the oxidised form is detached upon reduction and a proton is taken up. a 3.5-kb dna fragment, containing the gene encoding cytochrome c" (cyca), has been cloned and sequenced. the cytochrome c" gene codes for a pre-protein with a typical prokaryotic 20-residue signal sequence, suggesting that the protein is ... | 1999 | 10524262 |
| in rhodobacter sphaeroides reaction centers, mutation of proline l209 to aromatic residues in the vicinity of a water channel alters the dynamic coupling between electron and proton transfer processes. | the x-ray crystallographic structure of the photosynthetic reaction center from rhodobacter sphaeroides obtained at high resolution has revealed a number of internal water molecules (ermler, u., fritzsch, g., buchanan, s. k., and michel, h. (1994) structure 2, 925-936; stowell, m. h. b., mcphillips, t. m., rees, d. c., soltis, s. m., abresch, e., and feher, g. (1997) science 276, 812-816). some of them are organized into distinct hydrogen-bonded water chains that connect q(b) (the terminal quino ... | 1999 | 10529190 |
| electrochemical and spectroscopic investigations of the cytochrome bc1 complex from rhodobacter capsulatus. | the cytochrome bc(1) complex from rhodobacter capsulatus was investigated by protein electrochemistry and visible/ir spectroscopy. infrared difference spectra, which represent redox-induced conformational changes of cofactors and their protein environments, show signals of the hemes, the quinone q(i), and small conformational changes of the protein backbone. furthermore, band features were tentatively assigned to protonated aspartic or glutamic acids involved in the redox transition of each of t ... | 1999 | 10529191 |
| rhodobacter sphaeroides phosphoribulokinase: identification of lysine-165 as a catalytic residue and evaluation of the contributions of invariant basic amino acids to ribulose 5-phosphate binding. | rhodobacter sphaeroides phosphoribulokinase (prk) is inactivated upon exposure to pyridoxal phosphate/sodium borohydride, suggesting a reactive lysine residue. protection is afforded by a combination of the substrate atp and the allosteric activator nadh, suggesting that the targeted lysine maps within the active site. prk contains two invariant lysines, k53 and k165. prk-k53m retains sensitivity to pyridoxal phosphate, implicating k165 as the target of this reagent. prk-k165m retains wild-type ... | 1999 | 10529247 |
| identification, sequencing and structural analysis of a nifa-like gene of acetobacter diazotrophicus. | a recombinant plasmid, pad101, containing a dna fragment of acetobacter diazotrophicus strain pal5 was isolated by its ability to restore nif+ phenotype to a nifa- ntrc- double mutant of azotobacter vinelandii. hybridization with the nifa genes of azospirillum brasilense located the nifa gene more precisely to specific fragments of pad101. dna sequencing of appropriate subclones of pad101 revealed that the nifa gene was adjacent to the nifb gene in a. diazotrophicus, and the 5' end of the nifb g ... | 1999 | 10530336 |
| studies on the adp-ribose pyrophosphatase subfamily of the nudix hydrolases and tentative identification of trgb, a gene associated with tellurite resistance. | four nudix hydrolase genes, ysa1 from saccharomyces cerevisiae, orf209 from escherichia coli, yqkg from bacillus subtilis, and hi0398 from hemophilus influenzae were amplified, cloned into an expression vector, and transformed into e. coli. the expressed proteins were purified and shown to belong to a subfamily of nudix hydrolases active on adp-ribose. comparison with other members of the subfamily revealed a conserved proline 16 amino acid residues downstream of the nudix box, common to all of ... | 1999 | 10542272 |
| the photosynthetic apparatus of rhodobacter sphaeroides. | functional and ultrastructural studies have indicated that the components of the photosynthetic apparatus of rhodobacter sphaeroides are highly organized. this organization favors rapid electron transfer that is unimpeded by reactant diffusion. the light-harvesting complexes only partially surround the photochemical reaction center, which ensures an efficient shuttling of quinones between the photochemical reaction center and the bc1 complex. | 1999 | 10542422 |
| insertion of mini-is605 and deletion of adjacent sequences in the nitroreductase (rdxa) gene cause metronidazole resistance in helicobacter pylori nctc11637. | we found that nctc11637, the type strain of helicobacter pylori, the causative agent of peptic ulcer disease and an early risk factor for gastric cancer, is metronidazole resistant. dna transformation, pcr-based restriction analysis, and dna sequencing collectively showed that the metronidazole resistance of this strain was due to mutation in rdxa (gene hp0954 in the full genome sequence of h. pylori 26695) and that resistance did not depend on mutation in any of the other genes that had previou ... | 1999 | 10543743 |
| protein dynamics: imidazole binding to class i c-type cytochromes. | the oxidized cytochrome c(2) from the purple phototrophic bacteria, rhodobacter sphaeroides and rhodobacter capsulatus, bind the neutral species of imidazole (k(a) = 1440 +/- 40 m(-1)) 50 times more strongly than does horse mitochondrial cytochrome c (k(a) = 30 +/- 1 m(-1)). the kinetics of imidazole binding are consistent with a change in rate-limiting step at high ligand concentrations for all three proteins. this is attributed to a conformational change leading to breakage of the iron-methion ... | 1999 | 10545200 |
| effect of inhibitors on the ubiquinone binding capacity of the primary energy conversion site in the rhodobacter capsulatus cytochrome bc(1) complex. | a key issue concerning the primary conversion (q(o)) site function in the cytochrome bc(1) complex is the stoichiometry of ubiquinone/ubihydroquinone occupancy. previous evidence suggests that the q(o) site is able to accommodate two ubiquinone molecules, the double occupancy model [ding, h., robertson, d. e., daldal, f., and dutton, p. l. (1992) biochemistry 31, 3144-3158]. in the recently reported crystal structures of the cytochrome bc(1) complex, no electron density was identified in the q(o ... | 1999 | 10555979 |
| proton transfer from the bulk to the bound ubiquinone q(b) of the reaction center in chromatophores of rhodobacter sphaeroides: retarded conveyance by neutral water. | the mechanism of proton transfer from the bulk into the membrane protein interior was studied. the light-induced reduction of a bound ubiquinone molecule q(b) by the photosynthetic reaction center is accompanied by proton trapping. we used kinetic spectroscopy to measure (i) the electron transfer to q(b) (at 450 nm), (ii) the electrogenic proton delivery from the surface to the q(b) site (by electrochromic carotenoid response at 524 nm), and (iii) the disappearance of protons from the bulk solut ... | 1999 | 10557290 |
| magnesium insertion by magnesium chelatase in the biosynthesis of zinc bacteriochlorophyll a in an aerobic acidophilic bacterium acidiphilium rubrum. | to elucidate the mechanism for formation of zinc-containing bacteriochlorophyll a in the photosynthetic bacterium acidiphilium rubrum, we isolated homologs of magnesium chelatase subunits (bchi, -d, and -h). a. rubrum bchi and -h were encoded by single genes located on the clusters bchp-orf168-bchi-bchd-orf320-crti and bchf-n-b-h-l as in rhodobacter capsulatus, respectively. the deduced sequences of a. rubrum bchi, -d, and -h had overall identities of 59. 8, 40.5, and 50.7% to those from rba. ca ... | 1999 | 10559247 |
| characterization of adp-glucose pyrophosphorylase from rhodobacter sphaeroides 2.4.1: evidence for the involvement of arginine in allosteric regulation. | adp-glucose pyrophosphorylase (adpglc ppase, ec 2.7.7.27) from rhodobacter sphaeroides 2.4.1 has been purified to near homogeneity. the enzyme reacted in western blots to polyclonal antibodies raised against other bacterial adpglc ppases. the purified enzyme was found to be activated by fructose 6-phosphate, fructose 1,6-bisphosphate, and pyruvate and inhibited by phosphate, phosphoenolpyruvate, adp, and pyridoxal phosphate. kinetic studies indicate that amp, while having little effect on kineti ... | 1999 | 10562432 |
| identification of the allosteric regulatory site in bacterial phosphoribulokinase. | bacterial phosphoribulokinases (prks) are octameric members of the adenylate kinase family of enzymes. the enzyme is allosterically activated by nadh and allosterically inhibited by amp. we have determined the crystal structure of prk from rhodobacter sphaeroides bound to the atp analogue amp-pcp to a resolution of 2.6 a. the structure reveals that the atp analogue does not bind to the canonical atp site found in adenylate kinase family members. rather, the amp-pcp binds in two different orienta ... | 1999 | 10563798 |
| activation of the cyca p2 promoter for the rhodobacter sphaeroides cytochrome c2 gene by the photosynthesis response regulator. | the rhodobacter sphaeroides photosynthesis response regulator, prra, positively regulates cyca p2 expression. deletion analysis has identified sequences within 73 bp upstream of the transcription initiation site that are required for the activation of cyca p2 by prra. a mutant form of the rhodobacter capsulatus prra homologue, whose activity is independent of phosphorylation (rega*), protects an approximately 26 bp region of cyca p2 that is centred at approximately -50 from dnase digestion, and ... | 1999 | 10564521 |
| the energy landscape for ubihydroquinone oxidation at the q(o) site of the bc(1) complex in rhodobacter sphaeroides. | activation energies for partial reactions involved in oxidation of quinol by the bc(1) complex were independent of ph in the range 5. 5-8.9. formation of enzyme-substrate complex required two substrates, ubihydroquinone binding from the lipid phase and the extrinsic domain of the iron-sulfur protein. the activation energy for ubihydroquinone oxidation was independent of the concentration of either substrate, showing that the activated step was in a reaction after formation of the enzyme-substrat ... | 1999 | 10567355 |
| cloning and functional expression of the d-beta-hydroxybutyrate dehydrogenase gene of rhodobacter sp. dsmz 12077. | nucleotide sequence and biochemical analysis of d-beta-hydroxybutyrate dehydrogenase (ec 1.1.1.30), isolated from rhodobacter sp., indicate functional oligomers composed of subunits of 257 amino acids with a calculated m(r) of 26,800 and a pi of 5.90. compared to mammalian short-chain alcohol dehydrogenases, the bacterial enzyme lacks a c-terminal lipid anchor domain and was found to be highly active upon expression in escherichia coli even without lipid supplement. the recombinant enzyme could ... | 1999 | 10570813 |