PMID(sorted descending)
conversion of organic acids to h(2) by rhodospirillaceae grown with glutamate or dinitrogen as nitrogen source.axenic cultures of rhodopseudomonas capsulata. rhodospirillum rubrum, and rhodomicrobium vannielii grown with glutamate as the nitrogen source converted lactate, acetate, and butyrate to h(2) and co(2). conversion rates ranged from 100 to 926 ml h(2) l(r) (-1) day(-1) (where l(r) is the reactor contents), and efficiencies varied from 23 to 100% when grown with n(2), conversion rates up to 760 ml h(2) l(r) (-1) day(-1) and efficiencies up to 100%were achieved. upon aging, cultures appear to rapid ...198318548621
redox-state dynamics of ubiquinone-10 imply cooperative regulation of photosynthetic membrane expression in rhodospirillum is now well established that, for photosynthetic bacteria, the aerobic-to-microaerophilic transition activates the membrane-bound sensor kinase regb, which subsequently phosphorylates the transcriptional activator rega, thereby inducing elevated levels of intracellular photosynthetic membranes. the mechanism of regb activation--in particular, the role of ubiquinone-10--is controversial at present. one problem here is that very limited quantitative in vivo data for the response of the ubiquino ...200818487324
formation of a cross-linking complex of dinitrogenase reductase-activating glycohydrolase (drag) with membrane proteins from rhodospirillum rubrum chromatophores.association of dinitrogenase reductase-activating glycohydrolase (drag) with membrane proteins of chromatophores has been investigated. the formation of a multicomponent complex between drag and membrane proteins was demonstrated in the presence of glutaraldehyde and edc/nhs (n-(3-dimethylaminopropyl)-n -ethylcarbodiimide hydrochloride/hydroxy-2,5-dioxopyrrolidine-3-sulfonic acid sodium salt). complex formation was observed both in native chromatophore membrane and in chromatophores treated with ...200818298373
thermodynamics of the beta(2) association in light-harvesting complex i of rhodospirillum rubrum. implication of peptide identity in dimer stability.the core light-harvesting lh1 protein from rhodospirillum rubrum can dissociate reversibly in the presence of n-octyl-beta-d-glucopyranoside into smaller subunit forms, exhibiting a dramatic blue-shift in absorption. during this process, two main species are observed: a dimer that absorbs at 820 nm (b820) and a monomer absorbing at 777 nm (b777). in the presence of n-octyl-beta-d-glucopyranoside, we have previously shown that the b820 form is not only constituted by the alphabeta heterodimer alo ...200818266761
binding and reaction studies with adenine nucleotides on purified coupling factor from rhodospirillum rubrum.equilibrium binding studies with atpase isolated from rhodospirillum rubum chromotophores have been carried out using gel filtration. binding experiments with variable concentrations of [14c]adp show a biphasic saturation curve. with a parameter fitting computer program the dissociation constants for two distinct binding sites are determined as 7 x 10(-6) and 9 x 10(-5) m, respectively. the enzyme-bound radioactivity is recovered as adp (80-90%), and the rest is converted to amp and atp. in the ...197718265745
intermolecular vibrational coherence in the bacteriochlorophyll proteins b777 and b820 from rhodospirillum rubrum.the low-frequency vibrational coherence in the bacteriochlorophyll (bchl)-containing subunit proteins b777 and b820 from the lh1 light-harvesting complex isolated from rhodospirillum rubrum g9 exhibits rapidly damped modulation components arising from intermolecular, formally nonbonding interactions between the bchl macrocycle and polar groups in the surrounding detergent or protein. the vibrational coherence observed in the monomeric b777 system resembles that observed previously with bchl in a ...200818181604
rhodospirillum rubrum: utilization of condensed corn solubles for poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) production.this study sought to develop a less expensive medium for growth of the polyhydroxyalkanoate-producing bacterium rhodospirillum rubrum from the ethanol production coproduct, condensed corn solubles (ccs).200818179537
biosilicification of dual-fusion enzyme immobilized on magnetic nanoparticle.rapid recovery, immobilization, and silica encapsulation of a dual-fusion enzyme was achieved by using iminodiacetic acid (ida) modified magnetic nanoparticle as a carrier. d-amino acid oxidase (daao) of rhodosporidium toruloides was used as a model enzyme in which a silica-precipitating peptide r5 and a metal ion complexing peptide (his)(6) were fused to its n- and c-terminal, respectively. after charging the magnetic particle with cu(2+), the dual-fusion daao of 0.43 g could be directly recove ...200818078291
mesaconyl-coenzyme a hydratase, a new enzyme of two central carbon metabolic pathways in bacteria.the coenzyme a (coa)-activated c5-dicarboxylic acids mesaconyl-coa and beta-methylmalyl-coa play roles in two as yet not completely resolved central carbon metabolic pathways in bacteria. first, these compounds are intermediates in the 3-hydroxypropionate cycle for autotrophic co2 fixation in chloroflexus aurantiacus, a phototrophic green nonsulfur bacterium. second, mesaconyl-coa and beta-methylmalyl-coa are intermediates in the ethylmalonyl-coa pathway for acetate assimilation in various bacte ...200818065535
cloning and characterization of monofunctional catalase from photosynthetic bacterium rhodospirillum rubrum this study, an approx. 2.5-kb gene fragment including the catalase gene from rhodospirillum rubrum s1 was cloned and characterized. the determination of the complete nucleotide sequence revealed that the cloned dna fragment was organized into three open reading frames, designated as orf1, catalase, and orf3 in that order. the catalase gene consisted of 1,455 nucleotides and 484 amino acids, including the initiation and stop codons, and was located 326 bp upstream in the opposite direction of ...200718062223
phylogenomics and signature proteins for the alpha proteobacteria and its main groups.alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. however, for these bacteria as a whole and for all of its major subgroups (viz. rhizobiales, rhodobacterales, rhodospirillales, rickettsiales, sphingomonadales and caulobacterales), very few or no distinctive molecular or biochemical characteristics are known.200718045498
directed evolution of rubisco in escherichia coli reveals a specificity-determining hydrogen bond in the form ii enzyme.ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) occupies a critical position in photosynthetic co2-fixation and consequently has been the focus of intense study. crystal-structure-guided site-directed mutagenesis studies have met with limited success in engineering kinetic improvements to rubisco, highlighting our inadequate understanding of structural constraints at the atomic level that dictate the enzyme's catalytic chemistry. bioselection provides an alternative random mutagenic ap ...200718004873
a novel peroxiredoxin activity is located within the c-terminal end of rhodospirillum rubrum adenylyltransferase.adenylyltransferase (glne) catalyzes the reversible adenylylation of glutamine synthetase. in this report we present, for the first time, evidence for a peroxiredoxin activity of rhodospirillum rubrum glne, through the carboxyl-terminal ahpc/thiol-specific antioxidant (tsa) domain. the combination of glne and ahpc/tsa domains within the same polypeptide constitutes a unique domain architecture that has not previously been identified among proteobacteria.200817951375
differences in carbon isotope discrimination of three variants of d-ribulose-1,5-bisphosphate carboxylase/oxygenase reflect differences in their catalytic mechanisms.the carboxylation kinetic (stable carbon) isotope effect was measured for purified d-ribulose-1,5-bisphosphate carboxylases/oxygenases (rubiscos) with aqueous co(2) as substrate by monitoring rayleigh fractionation using membrane inlet mass spectrometry. this resulted in discriminations (delta) of 27.4 +/- 0.9 per thousand for wild-type tobacco rubisco, 22.2 +/- 2.1 per thousand for rhodospirillum rubrum rubisco, and 11.2 +/- 1.6 per thousand for a large subunit mutant of tobacco rubisco in whic ...200717925403
electrostatic effect of surfactant molecules on bacteriochlorophyll a and carotenoid binding sites in the lh1 complex isolated from rhodospirillum rubrum s1 probed by stark spectroscopy.the lh1 complexes were isolated from the purple photosynthetic bacterium rhodospirillum rubrum strain s1. they were initially solubilized using ldao and then purified in the presence of triton x-100. the purified complexes were then either used directly or following an exchange into ldao. stark spectroscopy was applied to probe the electrostatic field around the bacteriochlorophyll a (bchl a) and carotenoid binding sites in the lh1 complexes surrounded by these two different surfactant molecules ...200817922213
physiological versatility of the genus rhodocista.a new purple bacterium (strain t4), capable of heterotrophic aerobic and phototrophic anaerobic growth, was isolated from waste water of a noodle factory near hanoi, vietnam. a comparison of 16s rdna sequences revealed its association with the genus rhodocista. the isolate, tentatively named "rhodocista hanoiensis", forms cysts after growth on butyrate-containing plates at 42 degrees c. the vegetative cells form short (under aerobic conditions) or long curve-shaped rods. in contrast to other spe ...200717913074
probing binding site of bacteriochlorophyll a and carotenoid in the reconstituted lh1 complex from rhodospirillum rubrum s1 by stark spectroscopy.stark spectroscopy is a powerful technique to investigate the electrostatic interactions between pigments as well as between the pigments and the proteins in photosynthetic pigment-protein complexes. in this study, stark spectroscopy has been used to determine two nonlinear optical parameters (polarizability change tr(deltaalpha) and static dipole-moment change |deltamu| upon photoexcitation) of isolated and of reconstituted lh1 complexes from the purple photosynthetic bacterium, rhodospirillum ...200817912603
substitution of tyrosine 146 in the di component of proton-translocating transhydrogenase leads to reversible dissociation of the active dimer into inactive monomers.transhydrogenase couples the redox reaction between nadh and nadp+ to proton translocation across a membrane. the protein has three components: di binds nadh, diii binds nadp+, and dii spans the membrane. transhydrogenase is a "dimer" of two di-dii-diii "monomers"; x-ray structures suggested that the two catalytic sites alternate during turnover. invariant tyr146 in recombinant di of rhodospirillum rubrum transhydrogenase was substituted with phe and ala (proteins designated di.y146f and di.y146 ...200717911104
green and orange cdte quantum dots as effective ph-sensitive fluorescent probes for dual simultaneous and independent detection of of the most highlighted and fastest moving interfaces of nanotechnology is the application of quantum dots (qds) in biology. the unparalleled advantages of the size-tunable fluorescent emission and the simultaneous excitation at a single wavelength make qds the great possibility for use in optical encoding detection. in this paper, we report that green and orange cdte qds as convenient, cheap, reversible, and effective ph-sensitive fluorescent probes could monitor the proton (h+) flux driven ...200717887667
on the effects of pufx on the absorption properties of the light-harvesting complexes of rhodobacter sphaeroides.some species of purple bacteria as, e.g., rhodobacter sphaeroides contain the protein pufx. concurrently, the light harvesting complexes 1 (lh1) form dimers of open rings. in mutants without pufx, the lh1s are closed rings and photosynthesis breaks down, because the ubiquinone exchange at the reaction center is blocked. however, the main purpose of the lh1 is light harvesting. we therefore investigate the effects that the pufx-induced dimerization has on the absorption properties of the core com ...200717766331
evidence for a nitrogenase system in the photosynthetic bacterium rhodospirillum rubrum. 194917743273
photoproduction of molecular hydrogen by rhodospirillum rubrum. 194917743272
engineering of a type iii rubisco from a hyperthermophilic archaeon in order to enhance catalytic performance in mesophilic host cells.the hyperthermophilic archaeon thermococcus kodakaraensis harbors a type iii ribulose 1,5-bisphosphate carboxylase/oxygenase (rbc(tk)). it has previously been shown that rbc(tk) is capable of supporting photoautotrophic and photoheterotrophic growth in a mesophilic host cell, rhodopseudomonas palustris delta3, whose three native rubisco genes had been disrupted. here, we have examined the enzymatic properties of rbc(tk) at 25 degrees c and have constructed mutant proteins in order to enhance its ...200717675435
specificity and regulation of interaction between the pii and amtb1 proteins in rhodospirillum rubrum.the nitrogen regulatory protein p(ii) and the ammonia gas channel amtb are both found in most prokaryotes. interaction between these two proteins has been observed in several organisms and may regulate the activities of both proteins. the regulation of their interaction is only partially understood, and we show that in rhodospirillum rubrum one p(ii) homolog, glnj, has higher affinity for an amtb(1)-containing membrane than the other two p(ii) homologs, glnb and glnk. this interaction strongly f ...200717644595
purification and reconstitution of pyp-phytochrome with biliverdin and 4-hydroxycinnamic acid.pyp-phytochrome (ppr) is a unique photoreceptor that contains a blue light-absorbing photoactive yellow protein (pyp) domain, a red light-absorbing phytochrome domain, and a histidine kinase domain. this chapter describes overexpression of ppr in a strain of escherichia coli that allows covalent attachment of substoichiometric amounts of biliverdin in vivo. ppr is then fully reconstituted with biliverdin, followed by attachment of 4-hydroxycinnamic acid (p-coumaric acid), in vitro. holo-ppr with ...200717628140
the photoactivated pyp domain of rhodospirillum centenum ppr accelerates the recovery of the bacteriophytochrome domain after white light illumination.ppr from the purple phototrophic bacterium, rhodospirillum centenum (also known as rhodocista centenaria), is a hybrid of photoactive yellow protein (pyp), bacteriophytochrome (bph), and histidine kinase (hk) domains. the holo-ppr (containing both chromophores) exhibits characteristic absorption maxima at 435 nm due to the pyp domain and at 400, 642, and 701 nm due to the bph domain. illumination of the ppr with white light causes a bleach of both pyp and bph absorbance; weak blue light primaril ...200717590020
biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium: rhodopirillum rubrum.hydrogen may be considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. bioconversion of synthesis gas (syngas) to hydrogen was demonstrated in continuous stirred tank bioreactor (cstbr) utilizing acetate as a carbon source. an anaerobic photosynthetic bacterium, rhodospirillum rubrum catalyzed water-gas shift reaction which was applied for the bioconversion of syngas to hydrogen. the continuous fermentation of syngas in the bioreactor wa ...200817582763
the emitting state of tryptophan in proteins with highly blue-shifted fluorescence. 200717539030
ferripyochelin uptake genes are involved in pyochelin-mediated signalling in pseudomonas response to iron starvation, pseudomonas aeruginosa produces the siderophore pyochelin. when secreted to the extracellular environment, pyochelin chelates iron and transports it to the bacterial cytoplasm via its specific outer-membrane receptor fpta and the inner-membrane permease fptx. exogenously added pyochelin also acts as a signal which induces the expression of the pyochelin biosynthesis and uptake genes by activating pchr, a cytoplasmic regulatory protein of the arac/xyls family. the ...200717464065
h+-ppases: yesterday, today and tomorrow.suggestions by calvin about a role of inorganic pyrophosphate (ppi) in early photosynthesis and by lipmann that ppi may have been the original energy-rich phosphate donor in biological energy conversion, were followed in the mid-1960s by experimental results with isolated chromatophore membranes from the purple photosynthetic bacterium rhodospirillum rubrum. ppi was shown to be hydrolysed in an uncoupler stimulated reaction by a membrane-bound inorganic pyrophosphatase (ppase), to be formed at t ...200717454298
[screening and identification of a photosynthetic bacterium reducing selenite to red elemental selenium].selenium is essential element for humans and animals but is very toxic at higher concentrations. in four inorganic states of selenate [seo4 2- ( vi)], selenite [seo3 2- (iv)], elemental selenium [se (0)] and selenide [se2- (- ii )], selenite is well known to be more soluble and higher toxic than other three forms. many microorganisms have the capacity to reduce selenite to red elemental selenium, which provide the potential to cope with the detoxification of pollution and to use the biological a ...200717436622
the activity of adenylyltransferase in rhodospirillum rubrum is only affected by alpha-ketoglutarate and unmodified pii proteins, but not by glutamine, in vitro.ammonium assimilation is tightly regulated in nitrogen-fixing bacteria; the target of regulation is primarily the activity of the key enzyme glutamine synthetase that is regulated by reversible covalent modification by amp groups in reactions catalysed by the bifunctional adenylyltransferase (atase). the properties and regulation of atase from escherichia coli have been studied in great detail. we have investigated the regulation of atase from rhodospirillum rubrum, a photosynthetic nitrogen-fix ...200717419734
[the structural diversity of lipid a from gram-negative bacteria].the majority of gram-negative bacteria are pathogenic to humans and animals. lipopolysaccharide (lps) is the most biologically active component of these microorganisms. this compound is also called endotoxin to emphasize its negative impact on a macroorganism. lipid a, one of the three structural components of the lps molecule, is responsible for the pathophysiological effects associated with gram-negative bacteria infections. although lipid a is considered the conservative component of endotoxi ...200717369779
in vitro studies of the uridylylation of the three pii protein paralogs from rhodospirillum rubrum: the transferase activity of r. rubrum glnd is regulated by alpha-ketoglutarate and divalent cations but not by glutamine.p(ii) proteins have been shown to be key players in the regulation of nitrogen fixation and ammonia assimilation in bacteria. the mode by which these proteins act as signals is by being in either a form modified by ump or the unmodified form. the modification, as well as demodification, is catalyzed by a bifunctional enzyme encoded by the glnd gene. the regulation of this enzyme is thus of central importance. in rhodospirillum rubrum, three p(ii) paralogs have been identified. in this study, we ...200717337583
solution structure of the rhodobacter sphaeroides pufx membrane protein: implications for the quinone exchange and protein-protein interactions.pufx membrane protein is found in rhodobacter species of purple photosynthetic bacteria and has been known to play an essential role in ubiquinone/ubiquinol exchange between the reaction center and cytochrome bc1 complex and also contribute to the dimerization of the reaction center-light-harvesting core complex. we have determined the solution structure of the rhodobacter sphaeroides pufx using multidimensional nmr spectroscopy. the pufx, functionally expressed in escherichia coli, forms a stab ...200717335288
structure-based hypothesis on the activation of the co-sensing transcription factor cooa.the cooa family of proteins are prokaryotic co-sensing transcription factors that regulate the expression of genes involved in the utilization of co as an energy source. they are homodimeric proteins that contain two hemes. each monomer contains an n-terminal heme-binding domain and a c-terminal dna-binding domain. binding of co to the heme leads to activation by a large reorientation of the dna-binding domain such that the dna-binding domain is in position for specific dna recognition. the crys ...200717327664
structures of the di2diii1 complex of proton-translocating transhydrogenase with bound, inactive analogues of nadh and nadph reveal active site geometries.transhydrogenase couples the redox reaction between nadh and nadp+ to proton translocation across a membrane. the enzyme comprises three components; di binds nad(h), diii binds nadp(h), and dii spans the membrane. the 1,4,5,6-tetrahydro analogue of nadh (designated h2nadh) bound to isolated di from rhodospirillum rubrum transhydrogenase with similar affinity to the physiological nucleotide. binding of either nadh or h2nadh led to closure of the di mobile loop. the 1,4,5,6-tetrahydro analogue of ...200717323922
single-enzyme conversion of fmnh2 to 5,6-dimethylbenzimidazole, the lower ligand of b12.the synthesis of 5,6-dimethylbenzimidazole (dmb), the lower ligand of coenzyme b(12), has remained elusive. we report in vitro and in vivo evidence that the blub protein of the photosynthetic bacterium rhodospirillum rubrum is necessary and sufficient for catalysis of the o(2)-dependent conversion of fmnh(2) to dmb. the product of the reaction (dmb) was isolated by using reverse-phase high-pressure liquid chromatography, and its identity was established by uv-visible spectroscopy and ms. no meta ...200717301238
crystal structure of co-sensing transcription activator cooa bound to exogenous ligand imidazole.cooa is a co-dependent transcriptional activator and transmits a co-sensing signal to a dna promoter that controls the expression of the genes responsible for co metabolism. cooa contains a b-type heme as the active site for sensing co. co binding to the heme induces a conformational change that switches cooa from an inactive to an active dna-binding form. here, we report the crystal structure of an imidazole-bound form of cooa from carboxydothermus hydrogenoformans (ch-cooa). in the resting for ...200717292914
mutations within the c-terminus of the gamma subunit of the photosynthetic f1-atpase activate mgatp hydrolysis and attenuate the stimulatory oxyanion effect.two highly conserved amino acid residues near the c-terminus within the gamma subunit of the mitochondrial atp synthase form a "catch" with an anionic loop on one of the three beta subunits within the catalytic alphabeta hexamer of the f1 segment [abrahams, j. p., leslie, a. g. w., lutter, r., and walker, j. e. (1994) nature 370, 621-628]. forming the catch is considered to be an essential step in cooperative nucleotide binding leading to gamma subunit rotation. the analogous residues, arg304 an ...200717288458
molecular assembly of artificial photosynthetic antenna core complex on an amino-terminated ito electrode.bacterial photosynthetic membrane proteins, light-harvesting antenna complex (lh1), reaction center (rc), and their combined 'core' complex (lh1-rc) are functional elements in the primary photosynthetic events, i.e., capturing and transferring light energy and subsequent charge separation. these photosynthetic units (psus) isolated from rhodospirillum rubrum (rs. rubrum) were assembled onto an ito electrode modified with 3-aminopropyltriethoxysilane (aps-ito). the near ir absorption spectra of p ...200717142019
co-dependent h2 evolution by rhodospirillum rubrum: role of codh:coof complex.upon exposure to co during anaerobic growth, the purple phototrophic bacterium rhodospirillum rubrum expresses a co-oxidizing h(2) evolving enzymatic system. the co-oxidizing enzyme, carbon monoxide dehydrogenase (codh), has been purified and extensively characterized. however the electron transfer pathway from codh to the co-induced hydrogenase that evolves h(2) is not well understood. coof is an fe-s protein that is the proposed mediator of electron transfer between codh and the co-induced hyd ...200617123462
self-assembled monolayer of light-harvesting core complexes of photosynthetic bacteria on an amino-terminated ito electrode.light-harvesting antenna core (lh1-rc) complexes isolated from rhodospirillum rubrum and rhodopseudomonas palustris were successfully self-assembled on an ito electrode modified with 3-aminopropyltriethoxysilane. near infra-red (nir) absorption, fluorescence, and ir spectra of these lh1-rc complexes indicated that these lh1-rc complexes on the electrode were stable on the electrode. an efficient energy transfer and photocurrent responses of these lh1-rc complexes on the electrode were observed u ...200617111238
dna binding by an imidazole-sensing cooa variant is dependent on the heme redox state.cooa is a transcription factor from rhodospirillum rubrum that is regulated by the binding of the small molecule effector, co, to a heme moiety in the protein. the heme in cooa is axially ligated by two endogenous donors in the fe(iii) and fe(ii) states of the protein, and co binding to the fe(ii) state results in replacement of the distal ligand. reduction of the heme in the absence of co results in a ligand switch on the proximal side, in which a cysteine thiolate in the fe(iii) state is repla ...200717082920
analysis of ancient sequence motifs in the h-ppase family.the unique family of membrane-bound proton-pumping inorganic pyrophosphatases, involving pyrophosphate as the alternative to atp, was investigated by characterizing 166 members of the uniprotkb/swiss-prot + uniprotkb/trembl databases and available completed genomes, using sequence comparisons and a hidden markov model based upon a conserved 57-residue region in the loop between transmembrane segments 5 and 6. the hidden markov model was also used to search the approximately one million sequences ...200617054711
growth of rhodospirillum rubrum on synthesis gas: conversion of co to h2 and examine the potential use of synthesis gas as a carbon and energy source in fermentation processes, rhodospirillum rubrum was cultured on synthesis gas generated from discarded seed corn. the growth rates, growth and poly-beta-hydroxyalkanoates (pha) yields, and co oxidation/h(2) evolution rates were evaluated in comparison to the rates observed with an artificial synthesis gas mixture. depending on the gas conditioning system used, synthesis gas either stimulated or inhibited co-oxidation ra ...200717054121
possible pathway for ubiquinone shuttling in rhodospirillum rubrum revealed by molecular dynamics the last decade, the structures of many components of the photosynthetic apparatus of purple bacteria, as well as the mutual organization of these components within the purple membrane, were resolved. one key question that emerged concerned the assembly of the core complex consisting of the reaction center (rc) and the light-harvesting 1 (lh1) complex. in some species, like rhodobacter sphaeroides, the ring-shaped lh1 complex was found to be open, whereas other species, like rhodospirillum ru ...200717028136
functions of carotenoids in xanthorhodopsin and archaerhodopsin, from action spectra of photoinhibition of cell respiration.the recent discovery of a carotenoid light-harvesting antenna in xanthorhodopsin, a retinal-based proton pump in salinibacter ruber, made use of photoinhibition of respiration in whole cells to obtain action spectra [balashov et al. science 309, (2005) 2061-2064]. here we provide further details of this phenomenon, and compare action spectra in three different systems where carotenoids have different functions or efficiencies of light-harvesting. the kinetics of light-induced inhibition of respi ...200617020745
mori-zwanzig memory analysis in single-molecule spectroscopy.we study the dynamical behavior of the rhodospirillum molischianum lh2 complex based on intensity time series obtained from single-molecule spectroscopy experiments. this is achieved by reconstructing the memory function describing the time-dependent fluctuations of the excited states. we conclude that the apparent stochastic evolution of the dynamics is controlled by at least two different non-markovian main processes.200616986896
bacterial lateral flagella: an inducible flagella system.flagella are complex surface organelles that allow bacteria to move towards favourable environments and that contribute to the virulence of pathogenic bacteria through adhesion and biofilm formation on host surfaces. there are a few bacteria that possess functional dual flagella systems, such as vibrio parahaemolyticus, some mesophilic aeromonas spp., rhodospirillum centenum and azospirillum brasilense. these bacteria are able to express both a constitutive polar flagellum required for swimming ...200616978346
dynamics and diffusion in photosynthetic membranes from rhodospirillum photometricum.photosynthetic organisms drive their metabolism by converting light energy into an electrochemical gradient with high efficiency. this conversion depends on the diffusion of quinones within the membrane. in purple photosynthetic bacteria, quinones reduced by the reaction center (rc) diffuse to the cytochrome bc(1) complex and then return once reoxidized to the rc. in rhodospirillum photometricum the rc-containing core complexes are found in a disordered molecular environment, with fixed light-ha ...200616950840
roles of the heme and heme ligands in the activation of cooa, the co-sensing transcriptional activator.cooa of rhodospirillum rubrum is a co-sensing, heme-containing transcriptional activator that regulates the expression of the genes responsible for co oxidation. we randomized the codons for residues 75-77 of cooa which include two proximal heme ligands, screened for both co-dependent and co-independent variants, and characterized in vivo and in vitro properties of selected cooa variants. the analysis showed that small residues at position 75 are critical and that, as previously suspected, his77 ...200616889751
heme displacement mechanism of cooa activation: mutational and raman spectroscopic evidence.the heme-containing protein cooa of rhodospirillum rubrum regulates the expression of genes involved in co oxidation. cooa binds its target dna sequence in response to co binding to its heme. activity measurements and resonance raman (rr) spectra are reported for cooa variants that bind dna even in the absence of co, those in which the wild-type residues at the 121-126 positions, tscmrt, are replaced by the residues ayllrl or ryllrl, and also for variants that bind dna poorly in the presence of ...200616873369
effect of mutation on the dissociation and recombination dynamics of co in transcriptional regulator cooa: a picosecond infrared transient absorption study.the co ligation process in a mutant (h77g) of cooa, the co-sensing transcriptional regulator in rhodospirillum rubrum, is studied with femtosecond time-resolved transient absorption spectroscopy in the mid-infrared region. following photolyzing excitation, a transient bleach in the vibrational region of bound co due to the co photodissociation is detected. in contrast to the spectra of the wild-type (wt) cooa, the transient bleach spectra of h77g cooa show a bimodal shape with peaks shifting to ...200616866371
theoretical prediction of spectral and optical properties of bacteriochlorophylls in thermally disordered lh2 antenna complexes.a general approach for calculating spectral and optical properties of pigment-protein complexes of known atomic structure is presented. the method, that combines molecular dynamics simulations, quantum chemistry calculations, and statistical mechanical modeling, is demonstrated by calculating the absorption and circular dichroism spectra of the b800-b850 bacteriochlorophylls of the lh2 antenna complex from rs. molischianum at room temperature. the calculated spectra are found to be in good agree ...200616863329
mechanically driven proton conduction in single delta-free order to observe mechanically driven proton flux in f(0)f(1)-atpase coupled with artificial driven rotation on f(1) simultaneously, a double channel observation system was established. an artificial delta-free f(0)f(1)-atpase was constructed with alpha(3), beta(3), epsilon, gamma, and c(n) subunits as rotator and a, b(2) as stator. the chromatophore was immobilized on the glass surface through biotin-streptavidin-biotin system, and the magnetic bead was attached to the beta subunit of delta-f ...200616844089
catalytic by-product formation and ligand binding by ribulose bisphosphate carboxylases from different phylogenies.during catalysis, all rubisco (d-ribulose-1,5-bisphosphate carboxylase/oxygenase) enzymes produce traces of several by-products. some of these by-products are released slowly from the active site of rubisco from higher plants, thus progressively inhibiting turnover. prompted by observations that form i rubisco enzymes from cyanobacteria and red algae, and the form ii rubisco enzyme from bacteria, do not show inhibition over time, the production and binding of catalytic by-products was measured t ...200616822231
effect of amtb homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in rhodospirillum rubrum.the amtb protein transports uncharged nh(3) into the cell, but it also interacts with the nitrogen regulatory protein p(ii), which in turn regulates a variety of proteins involved in nitrogen fixation and utilization. three p(ii) homologues, glnb, glnk and glnj, have been identified in the photosynthetic bacterium rhodospirillum rubrum, and they have roles in at least four overlapping and distinct functions, one of which is the post-translational regulation of nitrogenase activity. in r. rubrum, ...200616804182
two pathways of electron transport to nitrogenase in rhodospirillum rubrum: the major pathway is dependent on the fix gene the photosynthetic bacterium rhodospirillum rubrum, as in many other diazotrophs, electron transport to nitrogenase has not been characterized in great detail. in this study, we show that there are two pathways operating in r. rubrum. the products of the fix genes constitute the major pathway operating under heterotrophic conditions, whereas a pyruvate:ferredoxin oxidoreductase, encoded by the nifj gene, may play a central role under anaerobic conditions in the dark. in both systems, ferredox ...200616790015
the poor growth of rhodospirillum rubrum mutants lacking pii proteins is due to an excess of glutamine synthetase activity.the p(ii) family of proteins is found in all three domains of life and serves as a central regulator of the function of proteins involved in nitrogen metabolism, reflecting the nitrogen and carbon balance in the cell. the genetic elimination of the genes encoding these proteins typically leads to severe growth problems, but the basis of this effect has been unknown except with escherichia coli. we have analysed a number of the suppressor mutations that correct such growth problems in rhodospiril ...200616762025
overexpression and characterization of the rhodobacter sphaeroides pufx membrane protein in escherichia coli.heterologous expression of the pufx membrane protein from purple photosynthetic bacterium rhodobacter sphaeroides was attempted by using escherichia (e.) coli cells. the pufx was overexpressed as a recombinant protein with a histidine tag added to the carboxyl terminus, and can be extracted from the cell membrane by various detergents. circular dichroism measurements showed that the expressed pufx protein had alpha-helix contents of 29% in organic solvents and 22-26% in 0.8-2.0% (w/v) n-octyl be ...200716752956
the role of the dna-binding domains in cooa activation.carbon monoxide oxidation activator protein (cooa) is a dimeric carbon monoxide (co) binding transcription factor that in the presence of co promotes the transcription of genes involved in co oxidation in rhodospirillum rubrum. the off state (inactive) of fe(ii) cooa has his and pro as the two axial heme ligands. in contrast, in the on state, which is active in dna binding, the pro ligand bond has been replaced by co. this occurs by the transient loss of the pro ligand, thus generating a pentaco ...200616752905
microbial diversity in maras salterns, a hypersaline environment in the peruvian andes.maras salterns are located 3,380 m above sea level in the peruvian andes. these salterns consist of more than 3,000 little ponds which are not interconnected and act as crystallizers where salt precipitates. these ponds are fed by hypersaline spring water rich in sodium and chloride. the microbiota inhabiting these salterns was examined by fluorescence in situ hybridization (fish), 16s rrna gene clone library analysis, and cultivation techniques. the total counts per milliliter in the ponds were ...200616751493
a conserved mechanism controls translation of rubisco large subunit in different photosynthetic organisms.we previously proposed a mechanism for control of rubisco expression and assembly during oxidative stress in chlamydomonas reinhardtii. the n terminus of the large subunit (lsu) comprises an rna recognition motif (rrm) that is normally buried in the protein, but becomes exposed under oxidizing conditions when the glutathione pool shifts toward its oxidized form. thus, de novo translation and assembly of rubisco lsu stop with similar kinetics and the unpaired small subunit (ssu) is rapidly degrad ...200616731581
purification and characterization of a catalase from photosynthetic bacterium rhodospirillum rubrum s1 grown under anaerobic conditions.the photosynthetic bacterium, rhodospirillum rubrum s1, when grown under anaerobic conditions, generated three different types of catalases. in this study, we purified and characterized the highest molecular weight catalase from the three catalases. the total specific catalase activity of the crude cell extracts was 88 u/mg. after the completion of the final purification step, the specific activity of the purified catalase was 1,256 u/mg. the purified catalase evidenced an estimated molecular ma ...200616728955
modeling proline ligation in the heme-dependent co sensor, cooa, using small-molecule analogs.cooa, the only protein known to employ proline as a heme ligand, is a co-activated transcription factor found in the bacterium rhodospirillum rubrum. proline is a heme ligand in both the fe(iii) and fe(ii) states; the sixth ligand is cysteinate in fe(iii) cooa and histidine in fe(ii) cooa. when co binds to fe(ii) cooa, it selectively replaces the proline ligand, activating the protein. the proposed roles of proline are to stabilize the heme pocket during the redox-mediated ligand switch and to f ...200616724227
simple determination of the co(2)/o(2) specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase by the specific radioactivity of [c]glycerate 3-phosphate.a new method is presented for measurement of the co(2)/o(2) specificity factor of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco). the [(14)c]3-phosphoglycerate (pga) from the rubisco carboxylase reaction and its dilution by the rubisco oxygenase reaction was monitored by directly measuring the specific radioactivity of pga. (14)co(2) fixation with rubisco occurred under two reaction conditions: carboxylase with oxygenase with 40 micromolar co(2) in o(2)-saturated water and carboxylase ...199216668709
nitrogenase activity and amounts of nitrogenase proteins in a frankia-alnus incana symbiosis subjected to darkness.effects of prolonged darkness on nitrogenase activity in vivo, nitrogenase activity in vitro, and the amounts of nitrogenase proteins were studied in symbiotic frankia. plants of alnus incana (l.) moench in symbiosis with a local source of frankia were grown for 9 to 10 weeks in an 18/6 hour light/darkness cycle. after 12 hours of a light period, the plants were exposed to darkness for up to 40 hours. nitrogenase activity (acetylene reduction activity) of intact plants was measured repeatedly. f ...199116668058
analysis of chromophytic and rhodophytic ribulose-1,5-bisphosphate carboxylase indicates extensive structural and functional similarities among evolutionarily diverse algae.ribulose-1,5-bisphosphate carboxylase (rubisco) from the algae olisthodiscus luteus (chromophyte) and griffithsia pacifica (rhodophyte) are remarkably similar to each other. however, both enzymes differ significantly in the structure and function when compared to rubisco from green algae and land plants. analysis of purified rubisco from o. luteus and g. pacifica indicates that the size of the holoenzyme and stoichiometry of the 55 and 15 kilodalton subunit polypeptides are approximately 550 kil ...198916667160
effect of betaine on enzyme activity and subunit interaction of ribulose-1,5-bisphosphate carboxylase/oxygenase from aphanothece halophytica.the presence of betaine, a quaternary ammonium compound, at a concentration (0.5 molar) reported to accumulate inside aphanothece halophytica in response to increasing external salinity, slightly promoted ribulose-1,5-bisphosphate (rubp) carboxylase activity. kcl at 0.25 molar inhibited rubp carboxylase about 55%. betaine relieved the inhibition by 0.25 m kcl and the original uninhibited activity was restored at 1 m betaine. other osmoregulatory solutes such as sucrose and glycerol also reduced ...198616664941
kinetic variance of ribulose-1,5-bisphosphate carboxylase/oxygenase isolated from diverse taxonomic sources : ii. analysis by two dual label methods.two dual label methods were used to investigate kinetic variability of ribulose 1,5-bisphosphate (rubp) carboxylase/oxygenase (ec in addition to using [1-(14)c,5-(3)h]rubp (method 1), we describe here the detailed assay with (14)co(2) and [5-(3)h]rubp (method 2), which generates [(3)h,(14)c]3-phosphoglyceric acid and unlabeled (noncontaminating) phosphoglycolate; the carboxylase/oxygenase activity ratio (v(c)/v(o)) is calculated from (3)h/(14)c ratios of substrates and products. v(c)/ ...198416663680
phosphofructokinase activities in photosynthetic organisms : the occurrence of pyrophosphate-dependent 6-phosphofructokinase in plants and algae.a pyrophosphate-dependent phosphofructokinase (ppi-pfk) activity is detectable in extracts of a wide variety of primitive and advanced plants, the charalean algae, and in the photosynthetic bacterium, rhodospirillum rubrum. angiosperms with extractable ppi-pfk activities 4- to 70-fold higher than the respective atp-pfk activities tend to be succulent and to exhibit cam. even though ppi-pfk activity is not detected in crude extracts of some well known cam plants, e.g. plants in the crassulaceae, ...198316662776
oxidation of c-type cytochromes by the membrane-bound cytochrome oxidase (cytochrome aa(3)) of blue-green algae.respiratory particles containing an aa(3)-type cytochrome oxidase were prepared from anacystis nidulans, synechocystis 6714, synechococcus lividus, anabaena variabilis, nostoc sp. strain mac, nostoc muscorum, and mastigocladus laminosus. oxidation of c-type cytochromes by membrane preparations of the different blue-green algae was observed using purified cytochromes from horse heart, candida krusei, tuna, saccharomyces oviformis, rhodospirillum rubrum, rhodospirillum molischianum, rhodopseudomon ...198216662253
carbon isotope fractionation by ribulose-1,5-bisophosphate carboxylase from various organisms.carbon isotope fractionation by structurally and catalytically distinct ribulose-1,5-bisphosphate carboxylases from one eucaryotic and four procaryotic organisms has been measured under nitrogen. the average fractionation for 40 experiments was -34.1 per thousand with respect to the delta(13)c of the dissolved co(2) used, although average fractionations for each enzyme varied slightly: spinach carboxylase, -36.5 per thousand; hydrogenomonas eutropha, -38.7 per thousand; agmenellum quadruplicatum ...197816660363
influence of light intensity on reductive pentose phosphate cycle activity during photoheterotrophic growth of rhodospirillum rubrum.light intensity during growth affects the proportion of carbon dioxide fixed by the reductive pentose phosphate cycle relative to that incorporated via c(4) acids in acetate phototrophs of rhodospirillum rubrum. with cells grown at high light intensity (9000 lux) the specific activities of ribulose-1, 5-diphosphate and propionyl coa carboxylases were increased compared with cells grown at low light intensity (1500 lux), although pyruvate carboxylase activity was unaltered.kinetic experiments wit ...197216658151
biosynthesis of the methoxylated carotenoids in rhodospirillum rubrum. 196416655991
photooxidase activity of heated chromatophores of rhodospirillum rubrum. 196216655619
studies on nitrogen fixation and photosynthesis of rhodospirillum rubrum. 195916655226
the effect of light on the oxygen metabolism of the photosynthetic bacterium, rhodospirillum rubrum. 195416654634
a hybrid of the transhydrogenases from rhodospirillum rubrum and mycobacterium tuberculosis catalyses rapid hydride transfer but not the complete, proton-translocating reaction.all transhydrogenases appear to have three components: di, which binds nad(h), and diii, which binds nadp(h), protrude from the membrane, and dii spans the membrane. however, the polypeptide composition of the enzymes varies amongst species. the transhydrogenases of mycobacterium tuberculosis and of rhodospirillum rubrum have three polypeptides. sequence analysis indicates that an ancestral three-polypeptide enzyme evolved into transhydrogenases with either two polypeptides (such as the escheric ...200616624251
distance between two active-site lysines of ribulose bisphosphate carboxylase from rhodospirillum the absence of a three-dimensional structure of ribulose-bisphosphate carboxylase/oxygenase [3-phospho-d-glycerate carboxy-lyase(dimerizing), ec], we have probed the distance between two active-site lysyl residues (lys-166 and lys-329) of the rhodospirillum rubrum enzyme with 4,4'-diisothiocyano-2,2'-disulfonate stilbene, a covalent cross-linking reagent that spans 12 a. the reagent rapidly inactivated the carboxylase, and a competitive inhibitor provided substantial protection. to r ...198616593786
structural studies of the primary donor cation radical p(870) in reaction centers of rhodospirillum rubrum by electron-nuclear double resonance in solution.the light-induced cation radical of the primary electron donor, p(870) (+.), in photosynthetic reaction centers from rhodospirillum rubrum g-9, has been investigated by electron-nuclear double resonance (endor) in liquid aqueous solution. the measured hyperfine coupling constants are assigned to specific molecular positions by partial deuteration. comparison with the bacteriochlorophyll a cation radical shows different reduction factors of the individual coupling constants deviating from the val ...198416593428
c nuclear magnetic resonance study of the co(2) activation of ribulosebisphosphate carboxylase from rhodospirillum rubrum.ribulosebisphosphate carboxylase [3-phospho-d-glycerate carboxy-lyase (dimerizing), ec] from rhodospirillum rubrum is activated by co(2) and mg(2+). (13)c nmr spectra were determined for the unactivated enzyme and for enzyme that had been activated by (13)co(2) and mg(2+). in addition to the expected resonance for h(13)co(3) (-)/co(3) (2-) at 161.8 ppm downfield from tetramethylsilane, the spectrum of the activated enzyme shows a broad resonance at 164.9 ppm. analogy with previous nmr s ...197916592618
regulation of l-isoleucine biosynthesis in the photosynthetic bacterium rhodospirillum rubrum. 196616591426
epr in chromatophores from rhodospirillum rubrum and in quantasomes from spinach chloroplasts. 196216590952
some observations on the synthesis and function of the photosynthetic apparatus in rhodospirillum rubrum. 196016590780
subcellular particulate systems and the photochemical apparatus of rhodospirillum rubrum. 195916590502
the role of invariant amino acid residues at the hydride transfer site of proton-translocating transhydrogenase.transhydrogenase couples proton translocation across a membrane to hydride transfer between nadh and nadp+. previous x-ray structures of complexes of the nucleotide-binding components of transhydrogenase ("di2diii1" complexes) indicate that the dihydronicotinamide ring of nadh can move from a distal position relative to the nicotinamide ring of nadp+ to a proximal position. the movement might be responsible for gating hydride transfer during proton translocation. we have mutated three invariant ...200616533815
enzymic systems proposed to be involved in the dissimilatory reduction of selenite in the purple non-sulfur bacteria rhodospirillum rubrum and rhodobacter capsulatus.various enzymic systems, such as nitrite reductase, sulfite reductase and glutathione reductase, have been proposed for, or suspected to be involved in, the reduction of selenite in bacteria. as alphaproteobacteria have been shown to be highly tolerant to transition metal oxyanions, it seemed interesting to investigate the hypothetical involvement of these different enzymes in the reduction of selenite in the purple non-sulfur bacteria rhodospirillum rubrum and rhodobacter capsulatus. the hypoth ...200616514153
calculation of absorption spectra for light-harvesting systems using non-markovian approaches as well as modified redfield theory.for an ensemble of b850 rings of the light-harvesting system lh2 of purple bacteria the linear absorption spectrum is calculated. using different markovian and non-markovian, time-dependent and time-independent methods based on second-order perturbation theory in the coupling between the excitonic system and its surrounding environment as well as the modified redfield theory, the influence of the shape of the spectral density on the linear absorption spectrum is demonstrated for single samples a ...200616512738
investigation of the effects of different carotenoids on the absorption and cd signals of light harvesting 1 complexes.absorption and circular dichroism (cd) spectra of light-harvesting (lh)1 complexes from the purple bacteria rhodobacter (rba.) sphaeroides and rhodospirillum (rsp.) rubrum are presented. the complexes exhibit very low intensity, highly nonconservative, near-infrared (nir) cd spectra. absorption and cd spectra from several mutant and reconstituted lh1 complexes, with the carotenoid neurosporene and the precursor phytoene replacing the wild-type (wt) carotenoids, are also examined. the experiments ...200616494350
identification of rhodospirillum rubrum glnb variants that are altered in their ability to interact with different targets in response to nitrogen status rhodospirillum rubrum, nifa, the transcriptional activator for the nif genes, is posttranslationally activated only by the uridylylated form of glnb, one of three p(ii) homologs in the organism. we have used the yeast two-hybrid system to detect variants of glnb that interact better with nifa than does wild-type glnb. when examined for physiological effects in r. rubrum, these glnb* variants activated nifa in the presence of nh(4)(+), which normally blocks nifa activation completely, and in t ...200616484197
quantum chemical simulation of excited states of chlorophylls, bacteriochlorophylls and their complexes.the present review describes the use of quantum chemical methods in estimation of structures and electronic transition energies of photosynthetic pigments in vacuum, in solution and imbedded in proteins. monomeric mg-porphyrins, chlorophylls and bacteriochlorophylls and their solvent 1:1 and 1:2 complexes were studied. calculations were performed for mg-porphyrin, mg-chlorin, mg-bacteriochlorin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), d and bacteriochlorophylls a, b, c, d, e, f, ...200616482307
design of a minimal polypeptide unit for bacteriochlorophyll binding and self-assembly based on photosynthetic bacterial light-harvesting proteins.we introduce lh1beta24, a minimal 24 amino acid polypeptide that binds and assembles bacteriochlorophylls (bchls) in micelles of octyl beta-glucoside (og) into complexes with spectral properties that resemble those of b820, a universal intermediate in the assembly of native purple bacterial light-harvesting complexes (lhs). lh1beta24 was designed by a survey of sequences and crystal structures of bacterial lh proteins from different organisms combined with currently available information from in ...200616475799
hexacoordination of bacteriochlorophyll in photosynthetic antenna lh1.the ability of chlorophylls to coordinate ligands is of fundamental structural importance for photosynthetic pigment-protein complexes, where in virtually all cases the pigment is thought to be in a pentacoordinated state. in this study, the correlation of the q(x) transition energy with the coordination state of the central metal in bacteriochlorophyll is applied in investigating the pigment coordination state in bacterial photosynthetic antenna lh1. to facilitate a detailed spectral analysis i ...200616460037
three-dimensional structure of ribulose-1,5-bisphosphate carboxylase/oxygenase from rhodospirillum rubrum at 2.9 a resolution.the three-dimensional structure of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) from rhodospirillum rubrum has been determined at 2.9 a resolution by x-ray crystallographic methods. the mir-electron density map was substantially improved by two-fold non-crystallographic symmetry averaging. the polypeptide chains in the dimer were traced using a graphics display system with the help of the bones option in frodo. the dimer has approximate dimensions of 50 x 72 x 105 a. the enzyme subu ...198616453738
a site-specific mutation within the active site of ribulose-1,5-bisphosphate carboxylase of rhodospirillum vitro mutagenic techniques have generated an asp-->glu substitution at residue 198 adjacent to the carbamate-divalent metal ion binding site of rhodospirillum rubrum ribulose 1,5-bisphosphate carboxylase. a single c-->a nucleotide change in the coding strand created the mutant and introduced a new ecori restriction site on the expression plasmid prr2119. although the carboxylase:oxygenase ratio remained the same, the mutant enzyme had slightly altered kinetic properties. the e.p.r. spectra of ...198416453576
micro-scale open-tube capillary separations of functional proteins.this article describes a novel technique whereby fully functional proteins or multiprotein complexes are efficiently extracted from biological samples to chemically derivatized walls of fused-silica open-tube capillary columns. proteins are eluted with very high yields into elution volumes that are smaller in volume than the internal volume of the open-tube capillary column itself, thereby achieving 100-fold increases in target protein concentrations from starting samples of less than 1 ml. the ...200616448620
evidence for displacements of the c-helix by co ligation and dna binding to cooa revealed by uv resonance raman spectroscopy.the uv and visible resonance raman spectra are reported for cooa from rhodospirillum rubrum, which is a transcriptional regulator activated by growth in a co atmosphere. co binding to heme in its sensor domain causes rearrangement of its dna-binding domain, allowing binding of dna with a specific sequence. the sensor and dna-binding domains are linked by a hinge region that follows a long c-helix. uv resonance raman bands arising from trp-110 in the c-helix revealed local movement around trp-110 ...200616439368
metabolic regulation of nitrogen fixation in rhodospirillum rubrum.nitrogenase activity in rhodospirillum rubrum is post-translationally regulated by drag (dinitrogenase reductase glycohydrolase) and drat (dinitrogenase reductase adp-ribosylation transferase). when a sudden increase in fixed nitrogen concentration or energy depletion is sensed by the cells, drag is inactivated and drat activated. we propose that the regulation of drag is dependent on its location in the cell and the presence of an ammonium-sensing protein.200616417510
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