Publications

in azotobacter vinelandii, the e1 subunit of the pyruvate dehydrogenase complex binds fpr promoter region dna and ferredoxin i.	in azotobacter vinelandii, deletion of the fdxa gene that encodes a well characterized seven-iron ferredoxin (fdi) is known to lead to overexpression of the fdi redox partner, nadph:ferredoxin reductase (fpr). previous studies have established that this is an oxidative stress response in which the fpr gene is transcriptionally activated to the same extent in response to either addition of the superoxide propagator paraquat to the cells or to fdxa deletion. in both cases, the activation occurs th ...	1999	10535932
purification and biophysical characterization of a new [2fe-2s] ferredoxin from azotobacter vinelandii, a putative [fe-s] cluster assembly/repair protein.	during the purification of site-directed mutant variants of azotobacter vinelandii ferredoxin i (fdi), a pink protein, which was not observed in native fdi preparations, appeared to associate specifically with variants that had mutations in ligands to fdi [fe-s] clusters. that protein, which we designate fdiv, has now been purified. nh(2)-terminal sequence analysis revealed that the protein is the product of a previously described gene, herein designated fdxd, that is in the a. vinelandii iscsua ...	1999	10542283
extended x-ray absorption fine structure studies on periplasmic and intracellular molybdenum-binding proteins.	we have studied the molybdenum k-edge x-ray absorption spectra of mo bound in the mo-binding proteins mop from haemophilus influenzae, modg from azotobacter vinelandii and the escherichia coli mode transcriptional regulatory protein, and compared them with the absorption spectra of a. vinelandii moda and monomeric molybdate. pre-edge and extended fine structure data indicate that the mo-binding proteins with molbindin-like domains bind tetrahedral molybdate with a mo-o distance of 1.76 a. the mo ...	1999	10550687
adaptation and population dynamics of azotobacter vinelandii during aerobic biological treatment of olive-mill wastewater.	olive-mill wastewater (omw) has a high organic and polyphenol content and is resistant to biodegradation. its disposal leads to a major environmental pollution problem in the mediterranean basin. the detoxification of omw following inoculation with azotobacter vinelandii (strain a) was performed for two successive 5-day-period cycles in an aerobic, biowheel-type reactor, under non-sterile conditions. the phytotoxicity of the processed product was reduced by over 90% at the end of both cycles. to ...	1999	10568839
enhanced efficiency of atp hydrolysis during nitrogenase catalysis utilizing reductants that form the all-ferrous redox state of the fe protein.	the amount of mgatp hydrolyzed per pair of electrons transferred (atp/2e) during nitrogenase catalysis (1.0 atm n(2), 30 degrees c) using titanium(iii) citrate (ti(iii)) as reductant was measured and compared to the same reaction using dithionite (dt). atp/2e values near 2.0 for ti(iii) and 5.0 for dt indicate that nitrogenase has a much lower atp requirement using ti(iii) as reductant. using reduced azotobacter vinelandii flavoprotein (avflph(2)), a possible in vivo nitrogenase reductant, atp/2 ...	1999	10572002
the basis of ammonium release in nifl mutants of azotobacter vinelandii.	in azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifla. certain mutations in nifl result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve nifa, the activator of nif gene transcription. we have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium releas ...	1999	10572141
saccharomyces cerevisiae isu1 and isu2: members of a well-conserved gene family for iron-sulfur cluster assembly.	recent studies in bacteria and eukaryotes have led to the identification of several new genes implicated in the biogenesis of iron-sulfur (fe/s) cluster-containing proteins. this report focuses on two genes of bakers yeast saccharomyces cerevisiae, isu1 and isu2, which encode homologues to bacterial iscu and nifu, potential iron-binding or cluster-assembly proteins. as with other yeast genes implicated in fe/s protein assembly, deletion of either isu1 or isu2 results in increased accumulation of ...	1999	10588895
alteration of the reduction potential of the [4fe-4s](2+/+) cluster of azotobacter vinelandii ferredoxin i.	the [4fe-4s](2+/+) cluster of azotobacter vinelandii ferredoxin i (fdi) has an unusually low reduction potential (e(0')) relative to other structurally similar ferredoxins. previous attempts to raise that e(0') by modification of surface charged residues were unsuccessful. in this study mutants were designed to alter the e(0') by substitution of polar residues for nonpolar residues near the cluster and by modification of backbone amides. three fdi variants, p21g, i40n, and i40q, were purified an ...	1999	10593945
analysis of the nifhdk operon and structure of the nifh protein from the unicellular, diazotrophic cyanobacterium, cyanothece strain sp. atcc 51142(1).	cyanothece sp. atcc 51142 is a unicellular, diazotrophic cyanobacterium that demonstrates diurnal rhythms for photosynthesis and n(2) fixation, with peaks of o(2) evolution and nitrogenase activity approximately 12 h out of phase. we cloned and sequenced the nifhdk operon, and determined that the amino acid sequences of all three proteins were highly conserved relative to those of other cyanobacteria and bacteria. however, the fe-protein, encoded by the nifh gene, demonstrated two differences fr ...	1999	10594374
chaotic dynamics of a food web in a chemostat.	we analyze a mathematical model of a simple food web consisting of one predator and two prey populations in a chemostat. monod's model is employed for the dependence of the specific growth rates of the two prey populations on the concentration of the rate-limiting substrate and a generalization of monod's model for the dependence of the specific growth rate of the predator on the concentrations of the prey populations. we use numerical bifurcation techniques to determine the effect of the operat ...	1999	10616281
ralstonia eutropha tf93 is blocked in tat-mediated protein export.	ralstonia eutropha (formerly alcaligenes eutrophus) tf93 is pleiotropically affected in the translocation of redox enzymes synthesized with an n-terminal signal peptide bearing a twin arginine (s/t-r-r-x-f-l-k) motif. immunoblot analyses showed that the catalytic subunits of the membrane-bound [nife] hydrogenase (mbh) and the molybdenum cofactor-binding periplasmic nitrate reductase (nap) are mislocalized to the cytoplasm and to the inner membrane, respectively. moreover, physiological studies s ...	2000	10633089
nifs-directed assembly of a transient [2fe-2s] cluster within the nifu protein.	the nifs and nifu proteins from azotobacter vinelandii are required for the full activation of nitrogenase. nifs is a homodimeric cysteine desulfurase that supplies the inorganic sulfide necessary for formation of the fe-s clusters contained within the nitrogenase component proteins. nifu has been suggested to complement nifs either by mobilizing the fe necessary for nitrogenase fe-s cluster formation or by providing an intermediate fe-s cluster assembly site. as isolated, the homodimeric nifu p ...	2000	10639125
modulating the midpoint potential of the [4fe-4s] cluster of the nitrogenase fe protein.	protein-bound [fes] clusters function widely in biological electron-transfer reactions, where their midpoint potentials control both the kinetics and thermodynamics of these reactions. the polarity of the protein environment around [fes] clusters appears to contribute largely to modulating their midpoint potentials, with local protein dipoles and water dipoles largely defining the polarity. the function of the [4fe-4s] cluster containing fe protein in nitrogenase catalysis is, at least in part, ...	2000	10651628
regulation of dinitrogenase reductase adp-ribosyltransferase and dinitrogenase reductase-activating glycohydrolase by a redox-dependent conformational change of nitrogenase fe protein.	the nitrogenase-regulating enzymes dinitrogenase reductase adp-ribosyltransferase (drat) and dinitrogenase reductase-activating glycohydrolase (drag), from rhodospirillum rubrum, were shown to be sensitive to the redox status of the [fe(4)s(4)](1+/2+) cluster of nitrogenase fe protein from r. rubrum or azotobacter vinelandii. drag had <2% activity with oxidized r. rubrum fe protein relative to activity with reduced fe protein. the activity of drag with oxygen-denatured fe protein or a low molecu ...	2000	10652344
nitrogenase reduction of carbon disulfide: freeze-quench epr and endor evidence for three sequential intermediates with cluster-bound carbon moieties.	freeze-quenching of nitrogenase during reduction of carbon disulfide (cs(2)) was previously shown to result in the appearance of a novel epr signal (g = 2.21, 1.99, and 1.97) not previously associated with any of the oxidation states of the nitrogenase metal clusters. in the present work, freeze-quench x- and q-band epr and q-band (13)c electron nuclear double resonance (endor) spectroscopic studies of nitrogenase during cs(2) reduction disclose the sequential formation of three distinct interme ...	2000	10653657
the replication origin of azotobacter vinelandii.	the putative replication origin of azotobacter vinelandii was cloned as an autonomously replicating fragment after ligation to an antibiotic resistance cartridge. the resulting plasmids could be isolated and labelled by southern hybridisation with the antibiotic resistance cartridge as probe and also visualised by electron microscopy. these plasmids integrated into the chromosome after a few generations, even in the reca mutant of a. vinelandii. the integrated copy of the plasmid was re-isolated ...	2000	10660068
regulation of cytochrome bd expression in the obligate aerobe azotobacter vinelandii by cydr (fnr). sensitivity to oxygen, reactive oxygen species, and nitric oxide.	azotobacter vinelandii is an obligately aerobic bacterium in which aerotolerant nitrogen fixation requires cytochrome bd. regulation of cytochrome bd expression is achieved by cydr (an fnr homologue), which represses transcription of the oxidase genes cydab. cydab mrna was mapped by primer extension; the transcriptional start site was determined, and putative -10 and -35 regions were deduced. two "cydr boxes," one at the +1 site and one upstream of the -35 region, were identified. transcriptiona ...	2000	10671497
hydrolysis of nucleoside triphosphates other than atp by nitrogenase.	the hydrolysis of atp to adp and p(i) is an integral part of all substrate reduction reactions catalyzed by nitrogenase. in this work, evidence is presented that nitrogenases isolated from azotobacter vinelandii and clostridium pasteurianum can hydrolyze mggtp, mgitp, and mgutp to their respective nucleoside diphosphates at rates comparable to those measured for mgatp hydrolysis. the reactions were dependent on the presence of both the iron (fe) protein and the molybdenum-iron (mofe) protein. th ...	2000	10692415
anaerobic and aerobic batch cultivations of saccharomyces cerevisiae mutants impaired in glycerol synthesis.	glycerol is formed as a by-product in production of ethanol and baker's yeast during fermentation of saccharomyces cerevisiae under anaerobic and aerobic growth conditions, respectively. one physiological role of glycerol formation by yeast is to reoxidize nadh, formed in synthesis of biomass and secondary fermentation products, to nad(+). the objective of this study was to evaluate whether introduction of a new pathway for reoxidation of nadh, in a yeast strain where glycerol synthesis had been ...	2000	10705374
azotobacter vinelandii nitrogenases containing altered mofe proteins with substitutions in the femo-cofactor environment: effects on the catalyzed reduction of acetylene and ethylene.	altered mofe proteins of azotobacter vinelandii mo-nitrogenase, with amino acid substitutions in the femo-cofactor environment, were used to probe interactions among c(2)h(2), c(2)h(4), co, and h(2). the altered mofe proteins used were the alpha-195(asn) or alpha-195(gln) mofe proteins, which have either asparagine or glutamine substituting for alpha-histidine-195, and the alpha-191(lys) mofe protein, which has lysine substituting for alpha-glutamine-191. on the basis of k(m) determinations, c(2 ...	2000	10715117
role of a nifs-like protein from the cyanobacterium synechocystis pcc 6803 in the maturation of fes proteins.	in azotobacter vinelandii and escherichia coli nifs or nifs-like proteins are involved in fes protein assembly by mobilizing sulfur from free cysteine. this sulfur together with fe(2+) is then incorporated into apo-fes proteins to form an fes center. a different activity termed c-des [for cyst(e)ine desulfurylase] was recently isolated from the cyanobacterium synechocystis pcc 6714 which also mobilized sulfur and which was able to incorporate the fes center into apoferredoxin. in the genome of t ...	2000	10727236
mutation of cytochrome bd quinol oxidase results in reduced stationary phase survival, iron deprivation, metal toxicity and oxidative stress in azotobacter vinelandii.	azotobacter vinelandii cydab mutants lacking cytochrome bd lost viability in stationary phase, irrespective of temperature, but microaerobiosis or iron addition to stationary phase cultures prevented viability loss. growth on solid medium was inhibited by a diffusible factor from neighbouring cells, and by iron chelators, in(iii) or ga(iii); microaerobic growth overcame inhibition by the extracellular factor. siderophore production and total fe(iii)-chelating activity were not markedly affected ...	2000	10731609
apoflavodoxin (un)folding followed at the residue level by nmr.	the denaturant-induced (un)folding of apoflavodoxin from azotobacter vinelandii has been followed at the residue level by nmr spectroscopy. nh groups of 21 residues of the protein could be followed in a series of 1h-15n heteronuclear single-quantum coherence spectra recorded at increasing concentrations of guanidinium hydrochloride despite the formation of protein aggregate. these nh groups are distributed throughout the whole apoflavodoxin structure. the midpoints of unfolding determined by nmr ...	2000	10739257
kinetic and mutational studies of three nifs homologs from escherichia coli: mechanistic difference between l-cysteine desulfurase and l-selenocysteine lyase reactions.	we have purified three nifs homologs from escherichia coli, csd, csdb, and iscs, that appear to be involved in iron-sulfur cluster formation and/or the biosynthesis of selenophosphate. all three homologs catalyze the elimination of se and s from l-selenocysteine and l-cysteine, respectively, to form l-alanine. these pyridoxal 5'-phosphate enzymes were inactivated by abortive transamination, yielding pyruvate and a pyridoxamine 5'-phosphate form of the enzyme. the enzymes showed non-michaelis-men ...	2000	10739946
role of molybdate and other transition metals in the accumulation of protochelin by azotobacter vinelandii.	both molybdate and iron are metals that are required by the obligately aerobic organism azotobacter vinelandii to survive in the nutrient-limited conditions of its natural soil environment. previous studies have shown that a high concentration of molybdate (1 mm) affects the formation of a. vinelandii siderophores such that the tricatecholate protochelin is formed to the exclusion of the other catecholate siderophores, azotochelin and aminochelin. it has been shown previously that molybdate comb ...	2000	10742245
isolation and characterization of an acetylene-resistant nitrogenase.	a genetic strategy was developed for the isolation of a mutant strain of azotobacter vinelandii that exhibits in vivo nitrogenase activity resistant to inhibition by acetylene. examination of the kinetic features of the altered nitrogenase mofe protein produced by this strain, which has serine substituted for the alpha-subunit gly(69) residue, is consistent with other studies that indicate the mofe protein normally contains at least two acetylene binding/reduction sites. the first of these is a ...	2000	10753963
adp-ribosylation of variants of azotobacter vinelandii dinitrogenase reductase by rhodospirillum rubrum dinitrogenase reductase adp-ribosyltransferase.	in a number of nitrogen-fixing bacteria, nitrogenase is posttranslationally regulated by reversible adp-ribosylation of dinitrogenase reductase. the structure of the dinitrogenase reductase from azotobacter vinelandii is known. in this study, mutant forms of dinitrogenase reductase from a. vinelandii that are affected in various protein activities were tested for their ability to be adp-ribosylated or to form a complex with dinitrogenase reductase adp-ribosyltransferase (drat) from rhodospirillu ...	2000	10762264
the gacs sensor kinase regulates alginate and poly-beta-hydroxybutyrate production in azotobacter vinelandii.	azotobacter vinelandii produces two polymers: the extracellular polysaccharide alginate and the intracellular polyester poly-beta-hydroxybutyrate (phb). a cosmid clone (psmu588) from an a. vinelandii gene library diminished alginate production by a. vinelandii mucoid strain atcc 9046. the nucleotide sequence and predicted amino acid sequence of the locus responsible for the mucoidy suppression revealed 65% identity to pseudomonas gacs, a transmembrane sensor kinase of the two-component regulator ...	2000	10762268
enzyme-mediated sulfide production for the reconstitution of [2fe-2s] clusters into apo-biotin synthase of escherichia coli. sulfide transfer from cysteine to biotin.	we previously showed that biotin synthase in which the (fe-s) cluster was labelled with 34s by reconstitution donates 34s to biotin [b. tse sum bui, d. florentin, f. fournier, o. ploux, a. méjean & a. marquet (1998) febs lett. 440, 226-230]. we therefore proposed that the source of sulfur was very likely the (fe-s) centre. this depletion of sulfur from the cluster during enzymatic reaction could explain the absence of turnover of the enzyme which means that to restore a catalytic activity, the c ...	2000	10785391
the crystal structure of a sulfurtransferase from azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families.	rhodanese is an ubiquitous enzyme that in vitro catalyses the transfer of a sulfur atom from suitable donors to nucleophilic acceptors by way of a double displacement mechanism. during the catalytic process the enzyme cycles between a sulfur-free and a persulfide-containing form, via formation of a persulfide linkage to a catalytic cys residue. in the nitrogen-fixing bacteria azotobacter vinelandii the rhda gene has been identified and the encoded protein functionally characterized as a rhodanes ...	2000	10788330
mutagenic analysis of thr-232 in rhodanese from azotobacter vinelandii highlighted the differences of this prokaryotic enzyme from the known sulfurtransferases.	azotobacter vinelandii rhda uses thiosulfate as the only sulfur donor in vitro, and this apparent selectivity seems to be a unique property among the characterized sulfurtransferases. to investigate the basis of substrate recognition in rhda, we replaced thr-232 with either ala or lys. thr-232 was the target of this study since the corresponding lys-249 in bovine rhodanese has been identified as necessary for catalytic sulfur transfer, and replacement of lys-249 with ala fully inactivates bovine ...	2000	10788632
regulation of biological nitrogen fixation.	biological nitrogen fixation, a process found only in some prokaryotes, is catalyzed by the nitrogenase enzyme complex. bacteria containing nitrogenase occupy an indispensable ecological niche, supplying fixed nitrogen to the global nitrogen cycle. due to this inceptive role in the nitrogen cycle, diazotrophs are present in virtually all ecosystems, with representatives in environments as varied as aerobic soils (e.g., azotobacter species), the ocean surface layer (trichodesmium) and specialized ...	2000	10801900
analysis of genes encoding an alternative nitrogenase in the archaeon methanosarcina barkeri 227.	methanosarcina barkeri 227 possesses two clusters of genes potentially encoding nitrogenases. we have previously demonstrated that one cluster, called nif2, is expressed under molybdenum (mo)-sufficient conditions, and the deduced amino acid sequences for nitrogenase structural genes in that cluster most closely resemble those for the mo nitrogenase of the gram-positive eubacterium clostridium pasteurianum. the previously cloned nifh1 from m. barkeri shows phylogenetic relationships with genes e ...	2000	10809706
modular organization and identification of a mononuclear iron-binding site within the nifu protein.	the nifs and nifu nitrogen fixation-specific gene products are required for the full activation of both the fe-protein and mofe-protein of nitrogenase from azotobacter vinelandii. because the two nitrogenase component proteins both require the assembly of [fe-s]-containing clusters for their activation, it has been suggested that nifs and nifu could have complementary functions in the mobilization of sulfur and iron necessary for nitrogenase-specific [fe-s] cluster assembly. the nifs protein has ...	2000	10819462
bioremediation of olive oil mill wastewater: chemical alterations induced by azotobacter vinelandii.	an environmentally friendly bioremediation system of olive oil mill wastewater (omww) is studied with respect to its physicochemical characteristics and degradation efficiency on major characteristic constituents. the method exploits the biochemical versatility of the dinitrogen fixing bacterium azotobacter vinelandii (strain a) to grow in omww at the expense of its constituents and to transform it into an organic liquid fertilizer. the system eliminates the phytotoxic principles from omww and c ...	2000	10820119
escherichia coli nifs-like proteins provide selenium in the pathway for the biosynthesis of selenophosphate.	selenophosphate synthetase (sps), the seld gene product from escherichia coli, catalyzes the biosynthesis of monoselenophosphate, amp, and orthophosphate in a 1:1:1 ratio from selenide and atp. kinetic characterization revealed the k(m) value for selenide approached levels that are toxic to the cell. our previous demonstration that a se(0)-generating system consisting of l-selenocysteine and the azotobacter vinelandii nifs protein can replace selenide for selenophosphate biosynthesis in vitro su ...	2000	10829016
identification of an fe protein residue (glu146) of azotobacter vinelandii nitrogenase that is specifically involved in femo cofactor insertion.	the fe protein of nitrogenase has three separate functions. much is known about the regions of the protein that are critical to its function as an electron donor to the mofe protein, but almost nothing is known about the regions of the protein that are critical to its functions in either femo cofactor biosynthesis or femo cofactor insertion. using computer modeling and information obtained from fe protein mutants that were made decades ago by chemical mutagenesis, we targeted a surface residue g ...	2000	10837496
kinetic properties of the 2-oxoglutarate dehydrogenase complex from azotobacter vinelandii evidence for the formation of a precatalytic complex with 2-oxoglutarate.	the 2-oxoglutarate dehydrogenase complex was purified from azotobacter vinelandii. the complex consists of three components, 2-oxoglutarate dehydrogenase/decarboxylase (e1o), lipoate succinyltransferase (e2o) and lipoamide dehydrogenase (e3). upon purification, the e3 component dissociates partially from the complex. from reconstitution experiments, the kd for e3 was found to be 26 nm, about 30 times higher than that for the pyruvate dehydrogenase complex. the km values for the substrates 2-oxog ...	2000	10848975
role of the azotobacter vinelandii nitrogenase-protective shethna protein in preventing oxygen-mediated cell death.	azotobacter vinelandii strains lacking the nitrogenase-protective shethna protein lost viability upon carbon-substrate deprivation in the presence of oxygen. this viability loss was dependent upon the n(2)-fixing status of cultures (n(2)-fixing cells lost viability, while non-n(2)-fixing cells did not) and on the ambient o(2) level. supra-atmosheric o(2) tensions (40% partial pressure) decreased the viable cell number of the mutant further, and the mutant had a slightly higher spontaneous mutati ...	2000	10851006
construction and characterization of a heterodimeric iron protein: defining roles for adenosine triphosphate in nitrogenase catalysis.	one molecule of mgatp binds to each subunit of the homodimeric fe protein component of nitrogenase. both mgatp molecules are hydrolyzed to mgadp and p(i) in reactions coupled to the transfer of one electron into the mofe protein component. as an approach to assess the contributions of individual atp binding sites, a heterodimeric fe protein was produced that has an asn substituted for residue 39 in the atp binding domain in one subunit, while the normal asp(39) residue within the other subunit r ...	2000	10852721
the hydrogenase cytochrome b heme ligands of azotobacter vinelandii are required for full h(2) oxidation capability.	the hydrogenase in azotobacter vinelandii, like other membrane-bound [nife] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. the histidines ligating the hemes in this cytochrome b were identified by h(2) oxidation properties of altered proteins produced by site-directed mutagenesis. four fully conserved and four partially conserved histidines in hoxz were substituted with alanine or tyrosine. the roles of these histidines in hoxz heme binding and hydrogena ...	2000	10852874
reactions of azotobacter vinelandii nitrogenase using ti(iii) as reductant.	nitrogenase-catalyzed reactions using ti(iii) were examined under a wide variety of conditions to determine the suitability of ti(iii) to serve as a general nitrogenase reductant. solutions prepared from h2-reduced ticl3, aluminum-reduced ticl3, ticl2, evaporated ticl3 from an hcl, solution, and tif3 were evaluated as reductants. three general types of reactivity were observed. the first showed that, below ti(iii) concentrations of about 0.50 mm, nitrogenase catalysis utilized ti(iii) in a first ...	2000	10857919
atomically defined mechanism for proton transfer to a buried redox centre in a protein.	the basis of the chemiosmotic theory is that energy from light or respiration is used to generate a trans-membrane proton gradient. this is largely achieved by membrane-spanning enzymes known as 'proton pumps. there is intense interest in experiments which reveal, at the molecular level, how protons are drawn through proteins. here we report the mechanism, at atomic resolution, for a single long-range electron-coupled proton transfer. in azotobacter vinelandii ferredoxin i, reduction of a buried ...	2000	10866206
protein folding and stability investigated by fluorescence, circular dichroism (cd), and nuclear magnetic resonance (nmr) spectroscopy: the flavodoxin story.	in this review, the experimental results obtained on the folding and stability of azotobacter vinelandii flavodoxin are summarised. by doing so, three main spectroscopic techniques used to investigate protein folding and stability are briefly introduced. these techniques are: circular dichroism (cd) spectroscopy, fluorescence emission spectroscopy, and nuclear magnetic resonance (nmr) spectroscopy in combination with the hydrogen exchange methodology. results on the denaturant-induced and therma ...	2000	10867188
dual regulation of catecholate siderophore biosynthesis in azotobacter vinelandii by iron and oxidative stress.	azotobacter vinelandii forms both catecholate and azotobactin siderophores during iron-limited growth. azotobactin is repressed by about 3 microm iron, but catecholate siderophore synthesis continues up to a maximum of 10 microm iron. this suggests that catecholate siderophore synthesis is regulated by other factors in addition to the ferric uptake repressor (fur). in this study the first gene required for catecholate siderophore biosynthesis, which encodes an isochorismate synthase (csbc), was ...	2000	10878126
iscu as a scaffold for iron-sulfur cluster biosynthesis: sequential assembly of [2fe-2s] and [4fe-4s] clusters in iscu.	iron-sulfur cluster biosynthesis in both prokaryotic and eukaryotic cells is known to be mediated by two highly conserved proteins, termed iscs and iscu in prokaryotes. the homodimeric iscs protein has been shown to be a cysteine desulfurase that catalyzes the reductive conversion of cysteine to alanine and sulfide. in this work, the time course of iscs-mediated fe-s cluster assembly in iscu was monitored via anaerobic anion exchange chromatography. the nature and properties of the clusters asse ...	2000	10891064
investigation of exchange couplings in [fe3s4]+ clusters by electron spin-lattice relaxation.	we have studied four proteins containing oxidized 3fe clusters ([fe3s4]+, s=1/2, composed of three, antiferromagnetically coupled high-spin ferric ions) by continuous wave (cw) and pulsed epr techniques: azotobacter vinelandii ferredoxin i, desulfovibrio gigas ferredoxin ii, and the 3fe forms of pyrococcus furiosus ferredoxin and aconitase. the 35 ghz (q-band) cw epr signals are simulated to yield experimental g tensors, which either had not been reported, or had been reported only at x-band mic ...	2000	10907748
identification of a second site compensatory mutation in the fe-protein that allows diazotrophic growth of azotobacter vinelandii uw97.	azotobacter vinelandii uw97 is defective in nitrogen fixation due to a replacement of serine at position 44 by phenylalanine in the fe-protein [pulakat, l., hausman, b.s., lei, s. and gavini, n. (1996) j. biol. chem. 271, 1884-1889]. serine residue 44 is located in a conserved domain that links the nucleotide binding site and the mofe-protein docking surface of the fe-protein. therefore, it is possible that the loss of function by a. vinelandii uw97-fe-protein may be caused by global conformatio ...	2000	10922495
functional bradyrhizobium japonicum nifa expression under a hybrid nptii-nifh promoter in e. coli and acetobacter diazotrophicus srt4.	a hybrid promoter consisting of the in tandem fusion of the tn5 nptii and the klebsiella pneumoniae nifh promoters was constructed to study the functionality of the nif genes transcriptional activator nifa from bradyrhizobium japonicum in two different host bacteria. beta-galactosidase experiments in e. coli revealed that the hybrid nptii-nifh promoter can behave as a constitutive or a nifa-inducible promoter depending on the aeration conditions. expression of the b. japonicum nifa from the hybr ...	1998	10932742
mannuronan c-5-epimerases and their application for in vitro and in vivo design of new alginates useful in biotechnology.	the industrially important polysaccharide alginate is a linear copolymer of beta-d-mannuronic acid (m) and alpha-l-guluronic acid (g). it is produced commercially by extraction from brown seaweeds, although some of the bacteria belonging to the genera azotobacter and pseudomonas also synthesize alginates. alginates are synthesized as mannuronan, and varying amounts of the m residues in the polymer are then epimerized to g residues by mannuronan c-5-epimerases. the gel-forming, water-binding, and ...	1999	10937941
influence of dissolved oxygen tension and agitation speed on alginate production and its molecular weight in cultures of azotobacter vinelandii*	the alginate production by azotobacter vinelandii, as well as the molecular weight of the polymer, are strongly influenced by the dissolved oxygen tension (dot) and stirring speed of the culture. under high dot (5% of air saturation), the bacteria produced more alginate (4.5 g/l) than that obtained at low (0.5%) oxygen tension (1.0 g/l) in cultures conducted at 300 rpm. on the other hand, under constant dot (3%), the higher the stirring speed (from 300 to 700 rev./min), the higher the specific g ...	2000	10938418
inactivation of the ampde operon increases transcription of algd and affects morphology and encystment of azotobacter vinelandii.	transcription of algd, encoding gdp-mannose dehydrogenase, the key enzyme in the alginate biosynthetic pathway, is highly regulated in azotobacter vinelandii. we describe here the characterization of a tn5 insertion mutant (ac28) which shows a higher level of expression of an algd::lacz fusion. ac28 cells were morphologically abnormal and unable to encyst. the cloning and nucleotide sequencing of the tn5-disrupted locus in ac28 revealed an operon homologous to the escherichia coli ampde operon. ...	2000	10940024
competitive substrate and inhibitor interactions at the physiologically relevant active site of nitrogenase.	nitrogenase catalyzes the mgatp-dependent reduction of dinitrogen gas to ammonia. in addition to the physiological substrate, nitrogenase catalyzes reduction of a variety of other multiply bonded substrates, such as acetylene, nitrous oxide, and azide. although carbon monoxide (co) is not reduced by nitrogenase, it is a potent inhibitor of all nitrogenase catalyzed substrate reductions except proton reduction. here, we present kinetic parameters for an altered azotobacter vinelandii mofe protein ...	2000	10948195
structure of c42d azotobacter vinelandii fdi. a cys-x-x-asp-x-x-cys motif ligates an air-stable [4fe-4s]2+/+ cluster.	all naturally occurring ferredoxins that have cys-x-x-asp-x-x-cys motifs contain [4fe-4s](2+/+) clusters that can be easily and reversibly converted to [3fe-4s](+/0) clusters. in contrast, ferredoxins with unmodified cys-x-x-cys-x-x-cys motifs assemble [4fe-4s](2+/+) clusters that cannot be easily interconverted with [3fe-4s](+/0) clusters. in this study we changed the central cysteine of the cys(39)-x-x-cys(42)-x-x-cys(45) of azotobacter vinelandii fdi, which coordinates its [4fe-4s](2+/+) clus ...	2000	10961993
effect of oxygen on formation and structure of azotobacter vinelandii alginate and its role in protecting nitrogenase.	the activity of nitrogenase in the nitrogen-fixing bacterium azotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against o(2) by a high respiration rate. in this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in a. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. instead, the formation of alginate appeared to play a decisive role in protecting the nitro ...	2000	10966426
azotobacter vinelandii nitrogenases with substitutions in the femo-cofactor environment of the mofe protein: effects of acetylene or ethylene on interactions with h+, hcn, and cn-.	wild-type and three altered azotobacter vinelandii nitrogenase mofe proteins, with substitutions either at alpha-195(his) (replaced by alpha-195(asn) or alpha-195(gln)) or at alpha-191(gln) (replaced by alpha-191(lys)), were used to probe the interactions of hcn and cn(-), both of which are present in nacn solutions at ph 7.4, with nitrogenase. the first goal was to determine how added c(2)h(2) enhances the rate of ch(4) production from hcn reduction by wild-type nitrogenase. in the absence of c ...	2000	10978172
respiratory protection of nitrogenase in azotobacter species: is a widely held hypothesis unequivocally supported by experimental evidence?	the hypothesis of respiratory protection, originally formulated on the basis of results obtained with azotobacter species, postulates that consumption of o(2) at the surface of diazotrophic prokaryotes protects nitrogenase from inactivation by o(2). accordingly, it is assumed that, at increased ambient o(2) concentrations, nitrogenase activity depends on increased activities of a largely uncoupled respiratory electron transport system. the present review compiles evidence indicating that cellula ...	2000	10978541
azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects.	azospirillum represents the best characterized genus of plant growth-promoting rhizobacteria. other free-living diazotrophs repeatedly detected in association with plant roots, include acetobacter diazotrophicus, herbaspirillum seropedicae, azoarcus spp. and azotobacter. four aspects of the azospirillum-plant root interaction are highlighted: natural habitat, plant root interaction, nitrogen fixation and biosynthesis of plant growth hormones. each of these aspects is dealt with in a comparative ...	2000	10978548
formation of a tight 1:1 complex of clostridium pasteurianum fe protein-azotobacter vinelandii mofe protein: evidence for long-range interactions between the fe protein binding sites during catalytic hydrogen evolution.	it has been well documented that the combination of the mofe protein of azotobacter vinelandii nitrogenase (av1) with the fe protein (cp2) from clostridium pasteurianum nitrogenase produces an inactive, stable complex. however, we report that this heterologous nitrogenase has a low level of activity for h(2) evolution, with a specific activity of 12 nmol min(-)(1) mg(-)(1) of av1. this activity does not arise from contaminating hydrogenase since it required the presence of both cp2 and av1 and s ...	2000	10985789
[granulated preparations of azotobacter in a clay-mineral base].	interaction of azotobacter chroococcum 20 cells with clay minerals increased their viability at supraoptimal temperatures. therefore, clay minerals were used to develop granular bacterial preparations with high viable cell counts and stable compositions during long-term storage. the titers of viable bacteria in the preparations remained 60-70% of the initial level after 12-month storage.	2000	10994201
the role of the mofe protein alpha-125phe and beta-125phe residues in azotobacter vinelandii mofe protein-fe protein interaction.	site-directed mutagenesis and gene-replacement techniques were used to substitute alanine for the mofe protein alpha- and beta-subunit phenylalanine-125 residues both separately and in combination. these residues are located on the surface of the mofe protein near the pseudosymmetric axis of symmetry between the alpha- and beta-subunits. altered mofe proteins that contain an alanine substitution at only one of the respective positions exhibit proton reduction activities of about 25-50% when comp ...	2000	11001089
cloning of the sth gene from azotobacter vinelandii and construction of chimeric soluble pyridine nucleotide transhydrogenases.	the gene encoding the soluble pyridine nucleotide transhydrogenase (sth) of azotobacter vinelandii was cloned and sequenced. this is the third sth gene identified and further defines a new subfamily within the flavoprotein disulfide oxidoreductases. the three sths identified all lack one of the redox active cysteines that are characteristic for this large family of enzymes, and instead they contain a conserved threonine residue at this position. the recombinant a. vinelandii enzyme was purified ...	2000	11004404
evidence for a two-electron transfer using the all-ferrous fe protein during nitrogenase catalysis.	the nitrogenase-catalyzed h(2) evolution and acetylene-reduction reactions using ti(iii) and dithionite (dt) as reductants were examined and compared under a variety of conditions. ti(iii) is known to make the all-ferrous fe protein ([fe(4)s(4)](0)) and lowers the amount of atp hydrolyzed during nitrogenase catalysis by approximately 2-fold. here we further investigate this behavior and present results consistent with the fe protein in the [fe(4)s(4)](0) redox state transferring two electrons ([ ...	2000	11005818
activation of vanadium nitrogenase expression in azotobacter vinelandii dj54 revertant in the presence of molybdenum.	azotobacter vinelandii carries three different and genetically distinct nitrogenase systems on its chromosome. expression of all three nitrogenases is repressed by high concentrations of fixed nitrogen. expression of individual nitrogenase systems is under the control of specific metal availability. we have isolated a novel type of a. vinelandii dj54 revertant, designated a. vinelandii bg54, which carries a defined deletion in the nifh gene and is capable of diazotrophic growth in the presence o ...	2000	11018539
production of b-group vitamins by two azotobacter strains with phenolic compounds as sole carbon source under diazotrophic and adiazotrophic conditions.	azotobacter vinelandii strain atcc 12837 and a. chroococcum strain h23 (cect 4435) were able to grow on n-free or nh4cl-amended chemically-defined (burk's) media, with protocatechuic acid (1-2 mmol 1(-1)) or sodium p-hydroxybenzoate (1-10 mmol 1(-1)) as sole carbon (c) sources. at a concentration of 2 mmol 1(-1), both substrates supported nitrogen fixation (acetylene reduction assay) at similar or higher rates than bacteria grown in control media amended with 2 mmol 1(-1) sodium succinate as c s ...	2000	11021581
comparison of the sequences of the aspergillus nidulans hxb and drosophila melanogaster ma-l genes with nifs from azotobacter vinelandii suggests a mechanism for the insertion of the terminal sulphur atom in the molybdopterin cofactor.	the molybdopterin cofactor (mocf) is required for the activity of a variety of oxidoreductases. the xanthine oxidase class of molybdoenzymes requires the mocf to have a terminal, cyanolysable sulphur ligand. in the sulphite oxidase/nitrate reductase class, an oxygen is present in the same position. mutations in both the ma-l gene of drosophila melanogaster and the hxb gene of aspergillus nidulans result in loss of activities of all molybdoenzymes that necessitate a cyanolysable sulphur in the ac ...	2000	11029694
requirement of homocitrate for the transfer of a 49v-labeled precursor of the iron-vanadium cofactor from vnfx to nif-apodinitrogenase.	a vanadium- and iron-containing cluster has been shown previously to accumulate on vnfx in the azotobacter vinelandii mutant strain ca11.1 (deltanifhdkvnfdgk::spc). in the present study, we show the homocitrate-dependent transfer of (49)v label from vnfx to nif-apodinitrogenase in vitro. this transfer of radiolabel correlates with acquisition of acetylene reduction activity. acetylene is reduced both to ethylene and ethane by the hybrid holodinitrogenase so formed, a feature characteristic of al ...	2001	11053414
role of azotobacter vinelandii muca and mucc gene products in alginate production.	azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. in different bacterial species, the alternative sigma factor sigma(e) regulates the expression of functions related to the extracytoplasmic compartments. in a. vinelandii and pseudomonas aeruginosa, the sigma(e) factor (algu) is essential for alginate production. in both bacteria, the activity of this sigma factor is regulated by the product of the muca, mucb ...	2000	11073894
signal transduction to the azotobacter vinelandii nifl-nifa regulatory system is influenced directly by interaction with 2-oxoglutarate and the pii regulatory protein.	pii-like signal transduction proteins, which respond to the nitrogen status via covalent modification and signal the carbon status through the binding of 2-oxoglutarate, have been implicated in the regulation of nitrogen fixation in several diazotrophs. the nifl-nifa two-component regulatory system, which integrates metabolic signals to fine-tune regulation of nitrogenase synthesis in azotobacter vinelandii, is a potential target for pii-mediated signal transduction. here we demonstrate that the ...	2000	11080151
analysis of steady state fe and mofe protein interactions during nitrogenase catalysis.	steady state kinetic measurements are reported for nitrogenase from azotobacter vinelandii (av) and clostridium pasteurianum (cp) under a variety of conditions, using dithionite as reductant. the specific activities of av1 and cp1 are determined as functions of av2:av1 and cp2:cp1, respectively, at component protein ratios from 0.4 to 50, and conform to a simple hyperbolic rate law for the interaction of av2 with av1 and cp2 with cp1. the specific activities of av2 and cp2 are also measured as a ...	2000	11087938
mechanistic interpretation of the dilution effect for azotobacter vinelandii and clostridium pasteurianum nitrogenase catalysis.	nitrogenase activity for clostridium pasteurianum (cp) at a cp2:cp1 ratio of 1.0 and azotobacter vinelandii (av) at av2:av1 protein ratios (r) of 1, 4 and 10 is determined as a function of increasing mofe protein concentration from 0.01 to 5 microm. the rates of ethylene and hydrogen evolution for these ratios and concentrations were measured to determine the effect of extreme dilution on nitrogenase activity. the experimental results show three distinct types of kinetic behavior: (1) a finite i ...	2000	11087939
kinetics of elementary steps of electron transfer in nitrogenase in the presence of a photodonor.	the kinetics of transfer of two electrons from a photodonor (a system containing eosin and nadh or 4;,5;-dibromofluorescein and nadh) to fe-protein (av2) and the kinetics of transfer of the first and second electrons from av2 to mo-fe-protein (av1) were studied by kinetic laser spectroscopy of nitrogenase from azotobacter vinelandii. the effects of the substrates of nitrogenase (nitrogen, acetylene, and protons) on the intramolecular electron transfer in nitrogenase were studied. analysis of the ...	2000	11092957
dynamic accumulation and degradation of poly(3-hydroxyalkanoate)s in living cells of azotobacter vinelandii uwd characterized by (13)c nmr.	the synthesis and degradation of poly(3-hydroxybutyrate) (phb) and poly(3-hydroxybutyrate-co-hydroxyvalerate) (p(hb-co-hv)) by azotobacter vinelandii uwd were investigated using natural abundance solution (13)c nuclear magnetic resonance (nmr) in vivo in shake flask culture and in fermenter culture. the synthesis and the degradation of poly(3-hydroxyalkanoate)s (pha) monomers hydroxybutyrate (hb) and hydroxyvalerate (hv) had different rates. the amount of hb and hv increased dramatically in the ...	2000	11111035
differential effects on n(2) binding and reduction, hd formation, and azide reduction with alpha-195(his)- and alpha-191(gln)-substituted mofe proteins of azotobacter vinelandii nitrogenase.	in contrast to the wild-type mofe protein, neither the alpha-195(asn) nor the alpha-191(lys) mofe protein catalyzed n(2) reduction to nh(3), when complemented with wild-type fe protein. however, n(2) was bound by the alpha-195(asn) mofe protein and inhibited the reduction of both protons and c(2)h(2). the alpha-191(lys) mofe protein did not interact with n(2). with the alpha-195(asn) mofe protein, the n(2)-induced inhibition of substrate reduction was reversed by removing the n(2). surprisingly, ...	2000	11112544
production of poly(3-hydroxybutyrate) from inexpensive substrates.	two inexpensive substrates, starch and whey were used to produce poly(3-hydroxybutyrate) (phb) in fed-batch cultures of azotobacter chroococcum and recombinant escherichia coli, respectively. oxygen limitation increased phb contents in both fermentations. in fed-batch culture of a. chroococcum, cell concentration of 54 g l(-1) with 46% phb was obtained with oxygen limitation, whereas 71 g l(-1) of cell with 20% phb was obtained without oxygen limitation. the timing of phb biosynthesis in recombi ...	2000	11118585
influence of environmental conditions on the activity of the recombinant mannuronan c-5-epimerase alge2.	the mannuronan c-5-epimerase alge2 is one of a family of ca(2+)-dependent epimerases secreted by azotobacter vinelandii. these enzymes catalyze the conversion of beta-d-mannuronic acid residues (m) to alpha-l-guluronic acid residues (g) in alginate. alge2 had a ph optimum between 6.5 and 7 and a temperature optimum around 55 degrees c. addition of low molecular weight organic compounds, including buffers, amino acids and osmoprotective compounds, affected the activity of the enzyme. the charge, ...	2001	11118599
expression of a cytoplasmic transhydrogenase in saccharomyces cerevisiae results in formation of 2-oxoglutarate due to depletion of the nadph pool.	the intracellular redox state of a cell is to a large extent defined by the concentration ratios of the two pyridine nucleotide systems nadh/nad(+) and nadph/nadp(+) and has a significant influence on product formation in microorganisms. the enzyme pyridine nucleotide transhydrogenase, which can catalyse transfer of reducing equivalents between the two nucleotide systems, occurs in several organisms, but not in yeasts. the purpose of this work was to analyse how metabolism during anaerobic growt ...	2001	11124698
action of azotobacter vinelandii poly-beta-d-mannuronic acid c-5-epimerase on synthetic d-glucuronans.	eleven different glucans (wheat starch, potato amylopectin, potato amylose, pullulan, alternan, regular comb dextran, alpha-cellulose, microcrystalline cellulose, cm-cellulose, chitin, and chitosan) that had their c-6 primary alcohol groups oxidized to carboxyl groups by reaction with 2,2,6,6-tetramethyl-1-piperidine oxoammonium ion (tempo), were reacted with azotobacter vinelandii poly-beta-(1-->4)-d-mannuronic acid c-5-epimerase. all of the oxidized polysaccharides reacted with the c-5-epimera ...	2000	11125837
enriching vermicompost by nitrogen fixing and phosphate solubilizing bacteria.	the effect of inoculation of vermicompost with nitrogen-fixing azotobacter chroococcum strains, azospirillum lipoferum and the phosphate solubilizing pseudomonas striata on n and p contents of the vermicompost was assessed. inoculation of n2 fixing bacteria into vermicompost increased contents of n and p. enriching vermicompost with rock phosphate improved significantly the available p when inoculated with p. striata. during the incubation period, the inoculated bacterial strains proliferated ra ...	2001	11131802
concerted inhibition of the transcriptional activation functions of the enhancer-binding protein nifa by the anti-activator nifl.	the azotobacter vinelandii nifl regulatory flavoprotein responds to the redox, energy and nitrogen status of the cell to inhibit transcriptional activation by the sigman-dependent enhancer binding protein, nifa, via the formation of a nifl-nifa protein complex. the nifa protein contains three domains: an n-terminal domain of unknown function; a central catalytic domain required to couple nucleotide hydrolysis to activation of the sigman-rna polymerase holoenzyme; and a c-terminal dna-binding dom ...	2001	11136467
beta-ketothiolase genes in azotobacter vinelandii.	azotobacter vinelandii is proposed to contain a single beta-ketothiolase activity participating in the formation of acetoacetyl-coa, a precursor for poly-beta-hydroxybutyrate (phb) synthesis, and in beta-oxidation (manchak, j., page, w.j., 1994. control of polyhydroxyalkanoate synthesis in azotobacter vinelandii strain uwd. microbiology 140, 953-963). we designed a degenerate oligonucleotide from a highly conserved region among bacterial beta-ketothiolases and used it to identify bkta, a gene wi ...	2000	11137297
protein-protein interactions in the complex between the enhancer binding protein nifa and the sensor nifl from azotobacter vinelandii.	the enhancer binding protein nifa and the sensor protein nifl from azotobacter vinelandii comprise an atypical two-component regulatory system in which signal transduction occurs via complex formation between the two proteins rather than by the phosphotransfer mechanism, which is characteristic of orthodox systems. the inhibitory activity of nifl towards nifa is stimulated by adp binding to the c-terminal domain of nifl, which bears significant homology to the histidine protein kinase transmitte ...	2001	11157949
alginate formation in azotobacter vinelandii uwd during stationary phase and the turnover of poly-beta-hydroxybutyrate.	azotobacter vinelandii uwd is a mutant of strain uw that is defective in the respiratory oxidation of nadh. this mutation causes an overproduction of polyhydroxyalkanoates (phas), as polyester synthesis is used as an alternative electron sink. since phas have potential for use as natural, biodegradable plastics, studies of physiology related to their production are of interest. alginate production by this strain is limited to < 11 microg (mg cell protein)(-1), which permits high efficiency conve ...	2001	11158365
biosynthesis of poly-beta-hydroxybutyrate (phb) is controlled by cydr (fnr) in the obligate aerobe azotobacter vinelandii.	cydr is an fnr-like protein in the obligatory aerobic nitrogen-fixing bacterium azotobacter vinelandii. the cydr mutant overproduces the cytochrome bd terminal oxidase. using two-dimensional polyacrylamide gel electrophoresis, we showed that beta-ketothiolase and acetoacetyl-coa reductase were also overexpressed in the cydr mutant. fumarase c and a coenzyme a transferase, possibly succinyl-scoa transferase, were decreased in this mutant. enzyme assays confirmed the elevated beta-ketothiolase and ...	2001	11164311
mgatp-bound and nucleotide-free structures of a nitrogenase protein complex between the leu 127 delta-fe-protein and the mofe-protein.	a mutant form of the nitrogenase iron protein with a deletion of residue leu 127, located in the switch ii region of the nucleotide binding site, forms a tight, inactive complex with the nitrogenase molybdenum iron (mofe) protein in the absence of nucleotide. the structure of this complex generated with proteins from azotobacter vinelandii (designated the l127delta-av2-av1 complex) has been crystallographically determined in the absence of nucleotide at 2.2 a resolution and with bound mgatp (int ...	2001	11170380
crystal structure of the all-ferrous [4fe-4s]0 form of the nitrogenase iron protein from azotobacter vinelandii.	the structure of the nitrogenase iron protein from azotobacter vinelandii in the all-ferrous [4fe-4s](0) form has been determined to 2.25 a resolution by using the multiwavelength anomalous diffraction (mad) phasing technique. the structure demonstrates that major conformational changes are not necessary either in the iron protein or in the cluster to accommodate cluster reduction to the [4fe-4s](0) oxidation state. a survey of [4fe-4s] clusters coordinated by four cysteine ligands in proteins o ...	2001	11170381
gene cloning, purification, and characterization of two cyanobacterial nifs homologs driving iron-sulfur cluster formation.	iron-sulfur proteins are essential in the photosynthetic system and many other biological processes. we have isolated and characterized enzymes driving the formation of iron-sulfur clusters from synechocystis sp. pcc6803. two genes (slr0387 and sll0704), showing similarity to nifs of azotobacter vinelandii, were cloned, and their gene products (sscsdl and sscsd2) were purified. they catalyzed the desulfuration of l-cysteine. reconstitution of a [2fe-2s] cluster of cyanobacterial ferredoxin proce ...	2000	11193410
100th american society for microbiology annual meeting.	the 100th asm annual meeting, attended by approximately 10,000 delegates, continued the trend of concentrating on bacteria and antibacterial therapy, mixed with genomics and a diverse number of additional topics. of the various marketable drug classes, the quinolones received attention with respect to susceptibility studies and several drug comparison studies. new marketable drugs were also of interest, especially given the reservoirs of resistance presented by several speakers. drugs in develop ...	2000	11203475
analogue-resistant mutants of azotobacter chroococcum derepressed for nitrogenase activity and early ammonia excretion having potential as inoculants for cereal crops.	spontaneous mutants resistant to methionine sulfoximine (msx), methyl alanine (mal) and methyl ammonium chloride (mac) were derived from a. chroococcum strain a103. msx and mal-resistant mutants expressed 1.73 to 10.98% of the fully derepressed nitrogenase activity when grown in burk's medium containing ammonium acetate. mac-resistant mutants did not express nitrogenase activity in ammonium acetate supplemented medium. the mutants excreted ammonia even after 2 days of growth and some mutants exc ...	2000	11218815
mannuronan c-5 epimerases and cellular differentiation of azotobacter vinelandii.	differentiation in azotobacter vinelandii involves the encystment of the vegetative cell under adverse environmental circumstances and the germination of the resting cell into the vegetative state when growth conditions are satisfactory again. morphologically, the encystment process involves the development of a protective coat around the resting cell. this coat partly consists of multiple layers of alginate, which is a copolymer of beta-d-mannuronic acid (m) and alpha-l-guluronic acid (g). algi ...	2000	11243259
analysis of the poba and pobr genes controlling expression of p-hydroxybenzoate hydroxylase in azotobacter chroococcum.	we report the cloning and analysis of a gene and its cognate regulatory element from a member of the azotobacteriaceae which are involved in the breakdown of an aromatic compound. the genes from azotobacter chroococcum encoding p-hydroxybenzoate hydroxylase (poba) and its regulatory protein (pobr) were cloned from a genomic library and sequenced. sequence analysis of poba revealed homology with other bacterial p-hydroxybenzoate hydroxylase enzymes. residues essential to the structure and functio ...	2001	11245981
electron paramagnetic resonance analysis of different azotobacter vinelandii nitrogenase mofe-protein conformations generated during enzyme turnover: evidence for s = 3/2 spin states from reduced mofe-protein intermediates.	rapid-freezing experiments elicited two transient epr signals, designated 1b and 1c, during azotobacter vinelandii nitrogenase turnover at 23 degrees c and ph 7.4. the first of the signals to form, signal 1b, exhibited g values of 4.21 and 3.76. its formation was at the expense of the starting epr signal (signal 1a with g values of 4.32, 3.66, and 2.01). the second signal to arise, signal 1c, with a characteristic g value of 4.69, formed very slowly and was always of low intensity. both signals ...	2001	11258953
structure and conformation of a novel genetically engineered polysaccharide p2.	a new exocellular polysaccharide (p2) has been produced by the manipulation of a glycosyl transferase gene (acep) involved in the biosynthesis of the polysaccharide acetan by the bacterium acetobacter xylinum strain cke5. the p2 polysaccharide has been studied by methylation analysis, reductive cleavage, and 1h and 13c nmr spectroscopy. the data are consistent with the structure predicted when the acep gene is deactivated: [molecular structure: see text]. the effect of cooling on proton nmr line ...	2001	11270811
glnd and mvin are genes of an essential operon in sinorhizobium meliloti.	to evaluate the role of uridylyl-transferase, the sinorhizobium meliloti glnd gene was isolated by heterologous complementation in azotobacter vinelandii. the glnd gene is cotranscribed with a gene homologous to salmonella mvin. glnd1::omega or mvin1::omega mutants could not be isolated by a powerful sucrose counterselection procedure unless a complementing cosmid was provided, indicating that glnd and mvin are members of an indispensable operon in s. meliloti.	2001	11274131
accumulation of 55fe-labeled precursors of the iron-molybdenum cofactor of nitrogenase on nifh and nifx of azotobacter vinelandii.	iron-molybdenum cofactor (femo-co) biosynthesis involves the participation of several proteins. we have used (55)fe-labeled nifb-co, the specific iron and sulfur donor to femo-co, to investigate the accumulation of protein-bound precursors of femo-co. the (55)fe label from radiolabeled nifb-co became associated with two major protein bands when the in vitro femo-co synthesis reaction was carried out with the extract of an azotobacter vinelandii mutant lacking apodinitrogenase. one of the bands, ...	2001	11279153
interaction of cytochrome bd with carbon monoxide at low and room temperatures: evidence that only a small fraction of heme b595 reacts with co.	azotobacter vinelandii is an obligately aerobic bacterium in which aerotolerant dinitrogen fixation requires cytochrome bd. this oxidase comprises two polypeptide subunits and three hemes, but no copper, and has been studied extensively. however, there remain apparently conflicting reports on the reactivity of the high spin heme b(595) with ligands. using purified cytochrome bd, we show that absorption changes induced by co photodissociation from the fully reduced cytochrome bd at low temperatur ...	2001	11283005
evidence for direct interaction between enzyme i(ntr) and aspartokinase to regulate bacterial oligopeptide transport.	bradyrhizobium japonicum transports oligopeptides and the heme precursor delta-aminolevulinic acid (ala) by a common mechanism. two tn5-induced mutants disrupted in the lysc and ptsp genes were identified based on the inability to use prolyl-glycyl-glycine as a proline source and were defective in [(14)c]ala uptake activity. lysc and ptsp were shown to be proximal genes in the b. japonicum genome. however, rnase protection and in trans complementation analysis showed that lysc and ptsp are trans ...	2001	11287431
functional, biochemical and genetic diversity of prokaryotic nitrate reductases.	prokaryotic nitrate reduction can serve a number of physiological roles and can be catalysed by a number of biochemically distinct nitrate reductases. three distinct nitrate reductase classes can be indentified in prokaryotes, nas, nar and nap. nas is located in the cytoplasmic compartment and participates in nitrogen assimilation. nar is usually a three-subunit complex anchored to the cytoplasmic face of the membrane with its active site located in the cytoplasmic compartment and is involved in ...	2001	11289299
groel-assisted refolding of adrenodoxin during chemical cluster insertion.	chemical reconstitution of recombinant bovine adrenal mitochondrial apoadrenodoxin was carried out in the presence of the nonhomologous chaperone protein groel and of the cochaperone groes, both in the presence and in the absence of atp. the approach used here was different from the one characterizing studies on chaperone activity, as we used an adrenodoxin apoprotein, devoid of the cluster iron and sulfide, rather than a denaturant-unfolded form of the protein, and catalytic amounts of the chap ...	2001	11298762
effect of redox mediators on nitrogenase and hydrogenase activities in azotobacter vinelandii.	in bioelectrochemical studies, redox mediators such as methylene blue, natural red, and thionine are used to studying the redox characteristics of enzymes in the living cell. here we show that nitrogenase activity in azotobacter vinelandii is completely inhibited by oxidized methylene blue (mbo) when the concentration of this mediator in the medium is increased up to 72 microm. this activity in a. vinelandii is somewhat inhibited by a coenzyme, ascorbic acid (aa). however, the nitrogenase activi ...	2000	11307951