| carboxyl-terminal processing may be essential for production of active nife hydrogenase in azotobacter vinelandii. | the nife hydrogenase from azotobacter vinelandii is a membrane-bound alpha beta heterodimer that can oxidize h2 to protons and electrons and thereby provide energy. genes encoding the alpha and beta subunits, hoxg and hoxk respectively, followed by thirteen contiguous accessory genes potentially involved in h2 oxidation, have been previously sequenced. mutations in some of these accessory genes give rise to inactive enzyme containing an alpha subunit with decreased electrophoretic mobility. mass ... | 1992 | 1516712 |
| covalent structure of the diheme cytochrome subunit and amino-terminal sequence of the flavoprotein subunit of flavocytochrome c from chromatium vinosum. | the complete sequence of the 21-kda cytochrome subunit of the flavocytochrome c (fc) from the purple phototrophic bacterium chromatium vinosum has been determined to be as follows: eptaemltnncagchg thgnsvgpaspsiaqmdpmvfvevmegfksgeias timgriakgystadfekmagyfkqqtyqpakqsf dtaladtgaklhdkycekchveggkpladeedy hilagqwtpylqyamsdfreerrpmekkmaskl rellkaegdagldalfafyasqq. the sequence is the first example of a diheme cytochrome in a flavocytochrome complex. although the locations of the heme binding sites an ... | 1991 | 1649169 |
| altered nitrogenase mofe proteins from azotobacter vinelandii. analysis of mofe proteins having amino acid substitutions for the conserved cysteine residues within the beta-subunit. | the regions surrounding the three strictly conserved cysteine residues (positions 70, 95 and 153) in the beta-subunit of the azotobacter vinelandii nitrogenase mofe protein have been proposed to provide p-cluster environments [dean, setterquist, brigle, scott, laird & newton (1990) mol. microbiol. 4, 1505-1512]. in the present study, each of these cysteine residues was individually substituted by either serine or alanine by site-directed mutagenesis of the nifk gene, which encodes the mofe prote ... | 1991 | 1650185 |
| electron transfer proteins of the purple phototrophic bacterium, rhodopseudomonas rutila. | the soluble electron transfer protein content of rhodopseudomonas rutila was found to consist of two basic cytochromes and a (4fe-4s) ferredoxin. cytochrome c' was easily identified by its characteristic high spin absorption spectra. the native molecular weight is 29,000 and the subunit is 14,000. cytochrome c-550 has low spin absorption spectra and a high redox potential (376 mv) typical of cytochromes c2. the molecular weight is about 14,000. the ferredoxin is apparently a dimer (43,000) of ap ... | 1991 | 1654788 |
| temperature effects on the mgatp-induced electron transfer between the nitrogenase proteins from azotobacter vinelandii. | the temperature dependence of the pre-steady-state mgatp-dependent electron transfer from the mofe protein to the fe protein of the nitrogenase from azotobacter vinelandii has been investigated between 6 degrees c and 31 degrees c by stopped-flow spectrophotometry. below 14 degrees c, the data are consistent with a model in which interaction of mgatp with nitrogenase is fast and irreversible, and is followed by reversible electron transfer. from the extent and from the rate of the absorbance cha ... | 1992 | 1521527 |
| taxonomic relationship of some members of azotobacteraceae based on their protein profiles. | analysis of protein profiles of the members of azotobacteraceae suggests that the genus azotobacter consists of a heterogeneous group of bacteria, of which azotobacter beijerinekii should possibly be separated to a new genus. azomonas agilis and azomonas macrocytogenes are only 26 percent related to each other. | 1992 | 1527705 |
| transcriptional regulation of cytochrome d in nitrogen-fixing azotobacter vinelandii. evidence that up-regulation during n2 fixation is independent of nifa but dependent on ntra. | cytochrome d has been postulated to be the "respiratory protection" oxidase of azotobacter vinelandii, allowing this organism to fix nitrogen under aerobic growth conditions. we have previously cloned and characterized the structural genes for the a. vinelandii cytochrome d (cyda and cydb). the cyd genes are co-transcribed, yielding an mrna of approximately 3.6 kilobase pairs. the level of the cyd message was 2-3-fold higher in cells that were fixing nitrogen, as compared with non-nitrogen-fixin ... | 1991 | 1660468 |
| nitrogenase structure: where to now? | | 1992 | 1529351 |
| crystallographic structure of the nitrogenase iron protein from azotobacter vinelandii. | the nitrogenase enzyme system catalyzes the atp (adenosine triphosphate)-dependent reduction of dinitrogen to ammonia during the process of nitrogen fixation. nitrogenase consists of two proteins: the iron (fe)-protein, which couples hydrolysis of atp to electron transfer, and the molybdenum-iron (mofe)-protein, which contains the dinitrogen binding site. in order to address the role of atp in nitrogen fixation, the crystal structure of the nitrogenase fe-protein from azotobacter vinelandii has ... | 1992 | 1529353 |
| structural models for the metal centers in the nitrogenase molybdenum-iron protein. | structural models for the nitrogenase femo-cofactor and p-clusters are proposed based on crystallographic analysis of the nitrogenase molybdenum-iron (mofe)-protein from azotobacter vinelandii at 2.7 angstrom resolution. each center consists of two bridged clusters; the femo-cofactor has 4fe:3s and 1mo:3fe:3s clusters bridged by three non-protein ligands, and the p-clusters contain two 4fe:4s clusters bridged by two cysteine thiol ligands. six of the seven fe sites in the femo-cofactor appear to ... | 1992 | 1529354 |
| the nifu, nifs and nifv gene products are required for activity of all three nitrogenases of azotobacter vinelandii. | strains with mutations in 23 of the 30 genes and open reading frames in the major nif gene cluster of a. vinelandii were tested for ability to grow on n-free medium with molybdenum (nif phenotype), with vanadium (vnf phenotype), or with neither metal present (anf phenotype). as reported previously, nife, nifn, nifu, nifs and nifv mutants were nif- (failed to grow on molybdenum) while nifm mutants were nif-, vnf- and anf-. nifv, nifs, and nifu mutants were found to be unable to grow on medium wit ... | 1992 | 1538703 |
| two open reading frames (orfs) identified near the hydrogenase structural genes in azotobacter vinelandii, the first orf may encode for a polypeptide similar to rubredoxins. | sequencing of 744 base pairs (bp) of a cloned section of dna from azotobacter vinelandii reveals two complete, closely-spaced open reading frames (orf1 and orf2). both orfs are transcribed from the same dna strand as that of the structural genes for hydrogenase (hoxk and hoxg, menon, a.l. et al. (1990) gene 96, 67-74), and are located downstream from the latter genes. the distance between the end of hoxg and the beginning of orf1 is approx. 3.0 kilobases (kb). most of the deduced amino acid sequ ... | 1992 | 1581355 |
| reconstitution of pyruvate dehydrogenase multienzyme complexes based on chimeric core structures from azotobacter vinelandii and escherichia coli. | two unique restriction sites were introduced by site-directed mutagenesis at identical positions in the dna encoding the dihydrolipoyltransacetylase (e2p) components of the pyruvate dehydrogenase complex from azotobacter vinelandii and from escherichia coli. in this manner each dna chain could be cut into three parts, coding for the lipoyl domain, which consists of three lipoyl subdomains, the binding domain and the core-forming catalytic domain, respectively. chimeric e2p components were constr ... | 1992 | 1597183 |
| regulation of nitrogenase-2 in azotobacter vinelandii by ammonium, molybdenum, and vanadium. | under diazotrophic conditions in the absence of molybdenum and in the presence of vanadium, azotobacter vinelandii reduces n2 to nh4+ by using nitrogenase-2, a v-containing enzyme complex encoded by vnfh (the gene for dinitrogenase reductase-2), and vnfdgk (the genes for dinitrogenase-2 subunits). accumulation of the vnfhorffd and vnfdgk transcripts occurred under mo-deficient conditions in the presence and absence of v; however, in the case of vnfdgk, the protein products only accumulated in th ... | 1992 | 1597411 |
| purification and cellular localization of wild type and mutated dihydrolipoyltransacetylases from azotobacter vinelandii and escherichia coli expressed in e. coli. | wild type dihydrolipoyltransacetylase(e2p)-components from the pyruvate dehydrogenase complex of a. vinelandii or e. coli, and mutants of a. vinelandii e2p with stepwise deletions of the lipoyl domains or the alanine- and proline-rich region between the binding and the catalytic domain have been overexpressed in e. coli tg2. the high expression of a. vinelandii wild type e2p (20% of cellular protein) and of a mutant enzyme with two lipoyl domains changed the properties of the inner bacterial mem ... | 1992 | 1554745 |
| functional analysis of the cysteine motifs in the ferredoxin-like protein fdxn of rhizobium meliloti involved in symbiotic nitrogen fixation. | the rhizobium meliloti fdxn gene, which is part of the nifa-nifb-fdxn operon, is absolutely required for symbiotic nitrogen fixation. the deduced sequence of the fdxn protein is characterized by two cysteine motifs typical of bacterial-type ferredoxins. the fix-phenotype of an r. meliloti fdxn::[tc] mutant could be rescued by the r. leguminosarum fdxn gene, whereas no complementation was observed with nif-associated genes encoding ferredoxins from bradyrhizobium japonicum, azotobacter vinelandii ... | 1992 | 1603075 |
| fe2+ and phosphate interactions in bacterial ferritin from azotobacter vinelandii. | fe2+ binding to both apo- and holo- bacterial ferritin from azotobacter vinelandii (avbf) was measured as a function of ph under carefully controlled anaerobic conditions. fe2+ binding to apo-avbf is strongly ph dependent with 25 fe2+ ions/apo-avbf binding tightly at ph 5.5 and over 150 fe2+/apo-avbf at ph 9.0. holo-avbf gave a similar ph-dependent binding profile with over 400 fe2+/avbf binding at ph of 9.0. proton release per fe2+ bound to either avbf protein increases with increasing ph until ... | 1992 | 1610815 |
| identification of six open reading frames from a region of the azotobacter vinelandii genome likely involved in dihydrogen metabolism. | we reported earlier the identification of two azotobacter vinelandii open reading frames (orfs), orf1 and orf2, downstream from the hydrogenase structural genes (chen, j.c. and mortenson, l.e. (1992) biochim. biophys. acta 1131, 122-124). sequencing of 6008 base pairs of dna immediately downstream from orf2 revealed six additional orfs (orf3 through orf8). all six orfs are transcribed from the same dna strand as that of the orf1 and orf2. deduced amino acid sequences of orf3 through orf5, and th ... | 1992 | 1610901 |
| excretion of ammonium by a nifl mutant of azotobacter vinelandii fixing nitrogen. | a mutation in the gene upstream of nifa in azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. the resulting mutant, mv376, produced nitrogenase constitutively in the presence of 15 mm ammonium. when introduced into a nifh-lacz fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. the gene upstream of nifa is therefore designated nifl because of its similarity to the klebsiella pneumoniae nifl gene in ... | 1992 | 1622243 |
| nucleotide sequences and genetic analysis of hydrogen oxidation (hox) genes in azotobacter vinelandii. | azotobacter vinelandii contains a heterodimeric, membrane-bound [nife]hydrogenase capable of catalyzing the reversible oxidation of h2. the beta and alpha subunits of the enzyme are encoded by the structural genes hoxk and hoxg, respectively, which appear to form part of an operon that contains at least one further potential gene (open reading frame 3 [orf3]). in this study, determination of the nucleotide sequence of a region of 2,344 bp downstream of orf3 revealed four additional closely space ... | 1992 | 1624446 |
| structural determination of alginic acid and the effects of calcium binding as determined by high-field n.m.r. | the nature of the solution conformations of the alginic acid components d-mannuronan (poly-mana) and l-guluronan (poly-gula) from azotobacter vinelandii were investigated by both one- and two-dimensional n.m.r. methods. unequivocal proton assignments for both polymers as well as their constituent monomer units were made based on chemical-shift theory, coupling constant analysis, and nuclear overhauser enhancement measurements. these data were used to investigate the interactions of poly-gula and ... | 1992 | 1633597 |
| lipoamide dehydrogenase from azotobacter vinelandii: site-directed mutagenesis of the his450-glu455 diad. kinetics of wild-type and mutated enzymes. | three amino acid residues in the active site of lipoamide dehydrogenase from azotobacter vinelandii were replaced with other residues. his450, the active-site base, was replaced with ser, tyr or phe. pro451, from x-ray analysis found to be in cis conformation positioning the backbone carbonyl of his450 close to n3 of the flavin, was changed to ala. glu455, from x-ray analysis expected to be involved in modulating the pka of the base (his450), was replaced with asp and gln. the general conclusion ... | 1992 | 1633804 |
| alginates: biosyntheses and some structure-function relationships relevant to biomedical and biotechnological applications. | | 1992 | 1633956 |
| membrane-structuring properties of bacterial long-chain alkylresorcinols. | to investigate the mechanism by which 5-n-alkyl(c19-c25)-resorcinols synthesized by certain bacteria of the azotobacter genus affect the lipid bilayers of cellular membranes, planar bimolecular membranes were formed from these alkyl-resorcinols and from mixtures of those and typical bacterial phospholipids such as phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. the electrical properties and, in some instances, the stability of the prepared membranes have been studied. ... | 1992 | 1637847 |
| comparison of the dynamical structures of lipoamide dehydrogenase and glutathione reductase by time-resolved polarized flavin fluorescence. | time-resolved polarized fluorescence spectroscopy has been applied to the bound fad in the structurally related flavoproteins lipoamide dehydrogenase from azotobacter vinelandii (lipdh-av) and glutathione reductase (gr) from human erythrocytes. the fluorescence parameters as obtained from the maximum entropy analysis differ considerably in both enzymes, reflecting the unique properties of the flavin microenvironment. three conformational substates are revealed in lipdh-av and five in gr. almost ... | 1992 | 1643038 |
| hydrazine is a product of dinitrogen reduction by the vanadium-nitrogenase from azotobacter chroococcum. | during the enzymic reduction of n2 to nh3 by mo-nitrogenase, free hydrazine (n2h4) is not detectable, but an enzyme-bound intermediate can be made to yield n2h4 by quenching the enzyme during turnover [thorneley, eady & lowe (1978) nature (london) 272, 557-558]. in contrast, we show here that the v-nitrogenase of azotobacter chroococcum produces a small but significant amount of free n2h4 (up to 0.5% of the electron flux resulting in n2 reduction) as a product of the reduction of n2. the amount ... | 1991 | 1859374 |
| molecular relaxation spectroscopy of flavin adenine dinucleotide in wild type and mutant lipoamide dehydrogenase from azotobacter vinelandii. | the temperature dependence of the fluorescence emission spectra of flavin adenine dinucleotide bound to lipoamide dehydrogenase from azotobacter vinelandii shows that the protein matrix in the vicinity of the prosthetic group is rigid on a nanosecond time scale in a medium of high viscosity (80% glycerol). the active site of a deletion mutant of this enzyme, which lacks 14 c-terminal amino acids, is converted from a solid-state environment (on the nanosecond time scale of fluorescence) into a st ... | 1992 | 1643039 |
| the hoxz gene of the azotobacter vinelandii hydrogenase operon is required for activation of hydrogenase. | the roles of the product of the hoxz gene immediately downstream of the hydrogenase gene (hoxkg) in azotobacter vinelandii were investigated by constructing and characterizing a mutant with the center of the hoxz gene deleted. the strain lacking the functional hoxz gene product exhibited a low rate of h2 oxidation with o2 as the electron acceptor relative to that of the wild-type strain. nevertheless, when the enzyme was exogenously activated and methylene blue was used as the electron acceptor ... | 1992 | 1644756 |
| dependence of oxygen-tolerant nitrogenase activity on divalent cations in azotobacter vinelandii. | nitrogenase activity of washed azotobacter vinelandii cells was enhanced by the addition of ca2+ and mg2+, and the enhancement increased with the o2 concentration. in assays provided with a level of o2 that was initially supraoptimal and inhibitory to nitrogenase activity, the addition of ca2+ or mg2+ affected both the maximum respiration rate (vmax) of the cells and the apparent affinity [ks(o2)] of cell respiration for o2. changes in these parameters correlated with changes in nitrogenase acti ... | 1992 | 1577706 |
| cloning, characterization, and expression in escherichia coli of the genes encoding the cytochrome d oxidase complex from azotobacter vinelandii. | azotobacter vinelandii is a free-living nitrogen-fixing bacterium that has one of the highest respiratory rates of all aerobic organisms. based on various physiological studies, a d-type cytochrome has been postulated to be the terminal oxidase of a vigorously respiring but apparently uncoupled branch of the electron transport system in the membranes of this organism. we cloned and characterized the structural genes of the two subunits of this oxidase. the deduced amino acid sequences of both su ... | 1991 | 1655703 |
| site-directed mutagenesis of azotobacter vinelandii ferredoxin i. changes in [4fe-4s] cluster reduction potential and reactivity. | we have used site-directed mutagenesis to obtain two variants of azotobacter vinelandii ferredoxin i (avfdi), whose x-ray structures are now available. in the c20a protein, a ligand to the [4fe-4s] cluster was removed whereas in the c24a mutant a free cysteine next to that cluster was removed. like native fdi, both mutants contain one [4fe-4s] cluster and one [3fe-4s] cluster. the structure of c24a is very similar to that of native fdi, while the structure of c20a is rearranged in the region of ... | 1991 | 1657971 |
| the product of the nitrogen fixation regulatory gene nfrx of azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnd in enteric bacteria. | we sequenced the nitrogen fixation regulatory gene nfrx from azotobacter vinelandii, mutations in which cause a nif- phenotype, and found that it encodes a 105-kda protein (nfrx), the n terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnd in escherichia coli. in vivo complementation experiments demonstrate that the glnd and nfrx products are functionally interchangeable. a vinelandii nfrx thus appears to encode a uridylyltransferase-u ... | 1991 | 1683868 |
| lipoamide dehydrogenase from azotobacter vinelandii: site-directed mutagenesis of the his450-glu455 diad. spectral properties of wild type and mutated enzymes. | three amino acid residues in the active site of lipoamide dehydrogenase from azotobacter vinelandii were replaced by other residues. his450, the active-site base, was changed into ser, tyr and phe. pro451, in cis conformation, was changed into ala. glu455 was replaced with asp and gln. absorption, fluorescence and cd spectroscopy of the mutated enzymes in their oxidized state (eox) showed only minor changes with respect to the wild-type enzyme, whereas considerable changes were observed in the s ... | 1991 | 1684937 |
| distribution of alginate gene sequences in the pseudomonas rrna homology group i-azomonas-azotobacter lineage of superfamily b procaryotes. | chromosomal dna from group i pseudomonas species, azotobacter vinelandii, azomonas macrocytogens, xanthomonas campestris, serpens flexibilis, and three enteric bacteria was screened for sequences homologous to four pseudomonas aeruginosa alginate (alg) genes (alga, pmm, algd, and algr1). all the group i pseudomonas species tested (including alginate producers and nonproducers) contained sequences homologous to all the p. aeruginosa alg genes used as probes, with the exception of p. stutzeri, whi ... | 1990 | 1689562 |
| unification of the ferritin family of proteins. | ferritin is the iron-storage protein of eukaryotic organisms. the nucleotide sequence encoding azotobacter vinelandii bacterioferritin, a hemoprotein, was determined. the deduced amino acid sequence reveals a high degree of identity with escherichia coli bacterioferritin and a striking similarity to eukaryotic ferritins. moreover, derivation of a global alignment shows that virtually all key residues specifying the unique structural motifs of eukaryotic ferritin are conserved or conservatively s ... | 1992 | 1549605 |
| production of exocellular polysaccharide by azotobacter chroococcum. | environmental conditions affect the production of extracellular polysaccharide by azotobacter chroococcum atcc 4412. production of exocellular polymer from a variety of carbon sources depended on the air flow rate. a high sucrose concentration in medium (8%) markedly favored expopolysaccharide production, which reached 14 g/l in about 72 h. in cell suspensions incubated in the presence of 8% sucrose in a nitrogen-free medium, biopolymer final concentration of 9 g/l corresponds to 68 g/g biomass. ... | 1991 | 1768080 |
| the catalytic domain of the dihydrolipoyl transacetylase component of the pyruvate dehydrogenase complex from azotobacter vinelandii and escherichia coli. expression, purification, properties and preliminary x-ray analysis. | partial sequences of the dihydrolipoyl transacetylase component (e2p) of the pyruvate dehydrogenase complex from azotobacter vinelandii and escherichia coli, containing the catalytic domain, were cloned in puc plasmids and over-expressed in e. coli tg2. a high expression of a homogeneous protein was only detectable for e2p mutants consisting of the catalytic domain and the alanine-proline-rich sequence between a putative binding region for the peripheral components and the catalytic domain (apa- ... | 1991 | 1935951 |
| simultaneous uptake of galactose and glucose by azotobacter vinelandii. | azotobacter vinelandii growing on galactosides induced two distinct permeases for glucose and galactose. the apparent vmax and km of the galactose permease were 16 nmol galactose/min per 10(10) cells and 0.5 mm, respectively. the apparent vmax and km of the glucose permease were 7.8 nmol glucose/min per 10(10) cells and 0.04 mm, respectively. excess glucose had no effect on the galactose uptake. however, excess galactose inhibited glucose transport. the galactosides-induced glucose permease also ... | 1991 | 1799437 |
| structure of the major exopolysaccharide produced by azotobacter beijerinckii b-1615. | a. beijerinckii strain b-1615 produced two acidic exopolysaccharides in the ratio approximately 9:1. the minor polysaccharide contained mannuronic and guluronic acids in the ratio 2.3:1 and is a bacterial alginate. the major polysaccharide consisted of d-galactose, l-rhamnose, and pyruvic acid in the ratios 2:1:1 and was acetylated. on the basis of methylation analysis, and 1h- and 13c-n.m.r. spectroscopy of the polysaccharide before and after removal of the pyruvic acid residues and o-deacetyla ... | 1991 | 1813106 |
| characterization of the pyoverdines of azotobacter vinelandii atcc 12837 with regard to heterogeneity. | azotobacter vinelandii strain atcc 12837 produces peptide siderophores of the general class known as pyoverdines. in the past, it was assumed that a single well-defined pyoverdine was produced by each parent microorganism. however, there are a number of reports of incompletely characterized pyoverdines that demonstrate heterogeneity in pyoverdine preparations obtained from a single organism, but the nature of this phenomena has not been explained. this study shows that a. vinelandii does indeed ... | 1991 | 1838001 |
| sequence and structural organization of a nif a-like gene and part of a nifb-like gene of herbaspirillum seropedicae strain z78. | the deduced amino acid sequence derived from the sequence of a fragment of dna from the free-living diazotroph herbaspirillum seropedicae was aligned to the homologous protein sequences encoded by the nifa genes from azorhizobium caulinodans, rhizobium leguminosarum, rhizobium meliloti and klebsiella pneumoniae. high similarity was found in the central domain and in the c-terminal region. the h. seropedicae putative nifa sequence was also found to contain an interdomain linker similar to that co ... | 1991 | 1840608 |
| nucleotide sequence of the fixabc region of azorhizobium caulinodans ors571: similarity of the fixb product with eukaryotic flavoproteins, characterization of fixx, and identification of nifw. | the nucleotide sequence of a 4.1 kb dna fragment containing the fixabc region of azorhizobium caulinodans was established. the three gene products were very similar to the corresponding polypeptides of rhizobium meliloti. the c-terminal domains of both fixb products displayed a high degree of similarity with the alpha-subunits of rat and human electron transfer flavoproteins, suggesting a role for the fixb protein in a redox reaction. two open reading frames (orf) were found downstream of fixc. ... | 1991 | 1850088 |
| tn5 mutagenesis and insertion replacement in azotobacter vinelandii. | tn5 insertion mutants of azotobacter vinelandii were isolated using vectors pjb4ji (incp) and pgs9 (incn). a procedure to replace tn5 (kmr) by its nontransposing derivative tn5-131 (tcr) was developed. for the replacement, a colel derivative harboring tn5-131 (prz131) was conjugally mobilized by the incn plasmid pcu101 into a. vinelandii strains containing tn5. both plasmids are unable to be maintained in a. vinelandii, but the transient presence of prz131 allows recombination between the incomi ... | 1991 | 1852019 |
| does ferredoxin i (azotobacter) represent a novel class of dna-binding proteins that regulate gene expression in response to cellular iron(ii)? | azotobacter vinelandii (av) and chroococcum (ac) ferredoxin i contain [3fe-4s]1 + 0 and [4fe-4s]2+1+ clusters, when isolated aerobically, which undergo one-electron redox cycles at potentials of -460 +/- 10 mv (vs she) at ph 8.3 and -645 +/- 10 mv, respectively. the x-ray structure of fd i (av) reveals that the n-terminal half of the polypeptide folds as a sandwich of beta-strands which enclose the iron-sulphur clusters. the c-terminal sequence contains an amphiphilic alpha-helix of four turns w ... | 1991 | 1855590 |
| direct electrochemistry of two genetically distinct flavodoxins isolated from azotobacter chroococcum grown under nitrogen-fixing conditions. | two genetically distinct flavodoxins, designated acflda and acfldb, were isolated from azotobacter chroococcum (mcd1155) grown under nitrogen-fixing conditions. acflda and acfldb differ in their midpoint potentials for the semiquinone-hydroquinone couple (em -305 mv and -520 mv respectively). only acfldb was competent to act as an electron donor to the mo-containing nitrogenase of a. chroococcum. the n-terminal amino acid sequence (20 residues) of acfldb was identical with that predicted from th ... | 1991 | 1859358 |
| structural studies of the extracellular polysaccharide elaborated by azotobacter vinelandii strain 1484. | the structure of the extracellular polysaccharide from azotobacter vinelandii strain 1484 has been investigated, specific degradations and n.m.r. spectroscopy being the main methods used. it is concluded that the polysaccharide is composed of tetrasaccharide repeating-units having the following structure, [sequence: see text] in which sug is 3-deoxy-d-threo-hexulosonic acid. the polysaccharide also contains a non-stoichiometric amount of o-acetyl groups, distributed over at least two positions. | 1991 | 1878880 |
| refined crystal structure of lipoamide dehydrogenase from azotobacter vinelandii at 2.2 a resolution. a comparison with the structure of glutathione reductase. | the structure of lipoamide dehydrogenase from azotobacter vinelandii has been refined by the molecular dynamics technique to an r-factor of 19.8% at 2.2 a resolution. in the final model, the root-mean-square deviation from ideality is 0.02 a for bond lengths and 3.2 degrees for bond angles. the asymmetric unit comprises two subunits, each consisting of 466 amino acid residues and the prosthetic group fad, plus 512 solvent molecules. the last ten amino acid residues of both chains are not visible ... | 1991 | 1880807 |
| effects of homocitrate, homocitrate lactone, and fluorohomocitrate on nitrogenase in nifv- mutants of azotobacter vinelandii. | azotobacter vinelandii dj71, which contains a mutation in the nifv gene, was derepressed for nitrogenase in the presence of homocitrate. when dinitrogenase was isolated from this culture, it was found to be identical to the wild-type dinitrogenase. however, when the same nifv- strain was derepressed in the presence of erythrofluorohomocitrate, a homocitrate analog which produces a nitrogenase with wild-type properties in vitro, the isolated dinitrogenase was characteristic of the nifv- enzyme. t ... | 1991 | 1885520 |
| nucleotide sequence and genetic analysis of the azotobacter chroococcum nifusvwzm gene cluster, including a new gene (nifp) which encodes a serine acetyltransferase. | nucleotide sequence was obtained for a region of 7,099 bp spanning the nifu, nifs, nifv, nifw, nifz, and nifm genes from azotobacter chroococcum. chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. the genes are tightly clustered and ordered as in klebsiella pneumoniae except for two additional open reading frames (orfs) between nifv and nifw. the arrangement of genes in a. chro ... | 1991 | 1885524 |
| broad-host-range properties of plasmid rk2: importance of overlapping genes encoding the plasmid replication initiation protein trfa. | the trfa gene, encoding the essential replication initiation protein of the broad-host-range plasmid rk2, possesses an in-frame overlapping arrangement. this results in the production of trfa proteins of 33 and 44 kda, respectively. utilizing deletion and site-specific mutagenesis to alter the trfa operon, we compared the replication of an rk2-origin plasmid in several distantly related gram-negative bacteria when supported by both trfa-44 and trfa-33, trfa-33 alone, or trfa-44/98l (a mutant for ... | 1991 | 1885553 |
| degradation of 2,4,6-trichlorophenol by azotobacter sp. strain gp1. | a bacterium which utilizes 2,4,6-trichlorophenol (tcp) as a sole source of carbon and energy was isolated from soil. the bacterium, designated strain gp1, was identified as an azotobacter sp. tcp was the only chlorinated phenol which supported the growth of the bacterium. resting cells transformed monochlorophenols, 2,6-dichlorophenol, and 2,3,6-trichlorophenol. phenol and a number of phenolic compounds, including 4-methylphenol, all of the monohydroxybenzoates, and several dihydroxybenzoates, w ... | 1991 | 1892382 |
| a method for preparing analytically pure sodium dithionite. dithionite quality and observed nitrogenase-specific activities. | sodium dithionite (na2s2o4) is widely used as a reductant in biochemical studies, but has not been available in its pure form. a convenient, detailed procedure is given for the recrystallization of commercial dithionite from 0.1 m naoh-methanol under anaerobic conditions. twice-recrystallized dithionite had a purity of 99 +/- 1% by uv spectroscopy (a315) and elemental analysis. the influence of dithionite quality on the apparent reduction activities of the nitrogenase components (av1 and av2) fr ... | 1991 | 1892862 |
| primary structure of a 7fe ferredoxin from streptomyces griseus. | the complete primary structure of a streptomyces griseus (atcc 13273) 7fe ferredoxin, which can couple electron transfer between spinach ferredoxin reductase and s. griseus cytochrome p-450soy for nadph-dependent substrate oxidation, has been determined by edman degradation of the whole protein and peptides derived by staphylococcus aureus v8 proteinase and trypsin digestion. the protein consists of 105 amino acids and has a calculated molecular weight, including seven irons and eight sulfurs, o ... | 1990 | 2106913 |
| aerobically purified hydrogenase from azotobacter vinelandii: activity, activation, and spectral properties. | the hydrogenase from azotobacter vinelandii is typically purified under anaerobic conditions. in this work, the hydrogenase was purified aerobically. the yields were low (about 2%) relative to those of the anaerobic purification (about 20%). the rate of enzyme activity depended upon the history of the enzyme. the enzyme preparations were active as isolated in h2 oxidation, and isotope exchange. the activity increased during the assay to a new maximal level (turnover activation). treatment with r ... | 1991 | 1898001 |
| molecular analysis of an anion pump: purification of the arsc protein. | the ars operon of resistance plasmid r773 encodes an anion-translocating atpase which catalyzes extrusion of the oxyanions arsenite, antimonite, and arsenate, thus providing resistance to the toxic compounds. although both arsenite and arsenate contain arsenic, they have different chemical properties. in the absence of the arsc gene the pump transports arsenite and antimonite, oxyanions with the +iii oxidation state of arsenic or antimony. the complex neither transports nor provides resistance t ... | 1991 | 1703401 |
| transcriptional regulation by metals of structural genes for azotobacter vinelandii nitrogenases. | azotobacter vinelandii has three nitrogenases: a molybdenum (mo) nitrogenase, a vanadium (v) nitrogenase, and a third nitrogenase (nitrogenase-3), which apparently lacks mo and v. mo represses synthesis of both v nitrogenase and nitrogenase-3, and in the absence of mo, v represses synthesis of nitrogenase-3. we have investigated transcriptional regulation of the three nitrogenases by metals using northern analysis and probes specific for transcripts of each of the three nitrogenases. our results ... | 1991 | 1714037 |
| ionic interactions in the nitrogenase complex. properties of fe-protein containing substitutions for arg-100. | a series of azotobacter vinelandii strains have been constructed in which the nitrogenase fe-protein (av2) was altered by substitutions for arg-100. this invariant residue is a likely partner in a salt bridge with the mofe-protein and, in some species, is the site of reversible regulation by adp-ribosylation (pope, m. r., murrell, s. a., and ludden, p. w. (1985) proc. natl. acad. sci. u. s. a. 82, 3173-3177). although we find that arginine is the optimum amino acid, other residues in this positi ... | 1992 | 1740419 |
| selective removal of molybdenum traces from growth media of n2-fixing bacteria. | a new method for the selective removal of traces of molybdenum from growth media of n2-fixing bacteria (rhodobacter capsulatus and klebsiella pneumoniae) was developed. this method is based on the filtration of nutrient solutions through a layer of activated carbon (pulverized charcoal). the adsorption of mo (molybdate) to activated carbon was optimal if a charcoal suspension (50 g/liter) was degassed by boiling before use and if the ph of the solutions, which had to be purified, was adjusted to ... | 1991 | 1908197 |
| interaction of lipoamide dehydrogenase with the dihydrolipoyl transacetylase component of the pyruvate dehydrogenase complex from azotobacter vinelandii. | the interaction between lipoamide dehydrogenase (e3) and dihydrolipoyl transacetylase (e2p) from the pyruvate dehydrogenase complex was studied during the reconstitution of monomeric e3 apoenzymes from azotobacter vinelandii and pseudomonas fluorescens. the dimeric form of e3 is not only essential for catalysis but also for binding to the e2p core, because the apoenzymes as well as a monomeric holoenzyme from p. fluorescens, which can be stabilized as an intermediate at 0 degree c, do not bind t ... | 1991 | 1908777 |
| purification and molecular cloning of succinyltransferase of the rat alpha-ketoglutarate dehydrogenase complex. absence of a sequence motif of the putative e3 and/or e1 binding site. | full-length cdna clones for succinyltransferase of the rat alpha-ketoglutarate dehydrogenase complex were isolated from rat heart cdna libraries in lambda gt11. the cdna clones were identified as those for rat succinyltransferase by the identity of their predicted amino acid sequence with the nh2-terminal amino acid sequence of rat succinyltransferase determined by protein chemical analysis and the known amino acid sequence of bovine succinyltransferase. the clone with the longest cdna consisted ... | 1991 | 1918017 |
| carotenoid desaturases from rhodobacter capsulatus and neurospora crassa are structurally and functionally conserved and contain domains homologous to flavoprotein disulfide oxidoreductases. | the characteristic red color of some photosynthetic bacteria and the orange color of neurospora conidia is due to the presence of carotenoids, photoprotective pigments synthesized by plants, algae, bacteria, and fungi. generally, carotenoids are tetraterpenes in which absorption of visible light and photoprotection are mediated by a chain of conjugated double bonds, the chromophore, which is formed by successive desaturations of phytoene, a colorless precursor. the genes al-1 and crti mediate th ... | 1990 | 2144293 |
| molecular analysis of an essential gene upstream of rpon in rhizobium ngr234. | rhizobium sp. ngr234 is a broad-host range strain. the rpon gene of this organism encodes a sigma factor which is a primary co-regulator of endosymbiosis. we characterized the locus upstream of rpon, and identified a contiguous open reading frame, here termed orf1. dna sequence analysis of this orf showed that it encoded a polypeptide highly conserved with a corresponding orf of rhizobium meliloti. the gene product contained two atp/gtp binding pockets. codon usage in the orf and the nitrogenase ... | 1991 | 1936948 |
| nucleotide sequence and mutational analysis of the vnfenx region of azotobacter vinelandii. | the nucleotide sequence (3,600 bp) of a second copy of nifenx-like genes in azotobacter vinelandii has been determined. these genes are located immediately downstream from vnfa and have been designated vnfenx. the vnfenx genes appear to be organized as a single transcriptional unit that is preceded by a potential rpon-dependent promoter. while the nifen genes are thought to be evolutionarily related to nifdk, the vnfen genes appear to be more closely related to nifen than to either nifdk, vnfdk, ... | 1991 | 1938952 |
| crystallographic analysis of two site-directed mutants of azotobacter vinelandii ferredoxin. | the crystal structure of the c24a mutant of azotobacter vinelandii 7fe ferredoxin (fdi) has been solved and refined at 2.0-a resolution. the structure is isomorphous to native fdi except at the site of mutation where a24 moves toward the [4fe-4s] cluster. in spite of this inefficient packing results: three of five van der waals contacts from the s gamma of c24 in native fdi are lost and the remaining two become longer. consequently, the [4fe-4s] cluster is either disordered or has a higher tempe ... | 1991 | 1939185 |
| molecular analysis of the azotobacter vinelandii glna gene encoding glutamine synthetase. | the gene encoding glutamine synthetase (gs), glna, was cloned from azotobacter vinelandii on a 6-kb ecori fragment that also carries the ntrbc genes. the dna sequence of 1,952 bp including the gs-coding region was determined. an open reading frame of 467 amino acids indicated a gene product of mr 51,747. transcription of glna occurred from a c residue located 32 bases upstream of an atg considered to be the initiator codon because (i) it had a nearby potential ribosome-binding site and (ii) an o ... | 1990 | 1977737 |
| complementation of a pleiotropic nif-gln regulatory mutant of rhodospirillum rubrum by a previously unrecognized azotobacter vinelandii regulatory locus. | a spontaneous pleiotropic nif- mutation in rhodospirillum rubrum has been partially characterized biochemically and by complementation analysis with recombinant plasmids carrying azotobacter vinelandii dna in the vicinity of orf12 [jacobson et al. (1989) j. bacteriol 171: 1017-1027]. in addition to being unable to grow on n2 as a nitrogen source the phenotypic characterization of this and other metronidazole enriched spontaneous mutants showed (a) no nitrogenase activity, (b) the absence of nifh ... | 1990 | 1980582 |
| detection of alternative nitrogenases in aerobic gram-negative nitrogen-fixing bacteria. | strains of aerobic, microaerobic, nonsymbiotic, and symbiotic dinitrogen-fixing bacteria were screened for the presence of alternative nitrogenase (n2ase) genes by dna hybridization between genomic dna and dna encoding structural genes for components 1 of three different enzymes. a nifdk gene probe was used as a control to test for the presence of the commonly occurring mo-fe n2ase, a vnfdgk gene probe was used to show the presence of v-fe n2ase, and an anfdgk probe was used to detect fe n2ase. ... | 1991 | 1987127 |
| site-directed mutagenesis of the dihydrolipoyl transacetylase component (e2p) of the pyruvate dehydrogenase complex from azotobacter vinelandii. binding of the peripheral components e1p and e3. | site-directed mutagenesis was performed in the protease-sensitive region, between the lipoyl and catalytic domains and in the catalytic domain, of the dihydrolipoyl transacetylase component (e2p) of the pyruvate dehydrogenase complex from azotobacter vinelandii. the interaction of the mutated enzymes with the peripheral components pyruvate dehydrogenase (e1p) and lipoamide dehydrogenase (e3) was studied by gel filtration experiments, analytical ultracentrifugation and reconstitution of the pyruv ... | 1991 | 1765097 |
| oxidation-reduction potentials of ferredoxin-nadp+ reductase and flavodoxin from anabaena pcc 7119 and their electrostatic and covalent complexes. | the oxidation-reduction potentials of ferredoxin-nadp+ reductase and flavodoxin from the cyanobacterium anabaena pcc 7119 were determined by potentiometry. the potentials at ph 7 for the oxidized flavodoxin/flavodoxin semiquinone couple (e2) and the flavodoxin semiquinone/hydroquinone couple (e1) were -212 mv and -436 mv, respectively. e1 was independent of ph above about ph 7, but changed by approximately -60 mv/ph below about ph 6, suggesting that the fully reduced protein has a redox-linked p ... | 1991 | 1765067 |
| the conformational stability of the redox states of lipoamide dehydrogenase from azotobacter vinelandii. | the conformational stability of holo-lipoamide and apo-lipoamide dehydrogenase from azotobacter vinelandii was studied by thermoinactivation, unfolding and limited proteolysis. the oxidized holoenzyme is thermostable, showing a melting temperature, tm = 80 degrees c. the thermal stability of the holoenzyme drastically decreases upon reduction. unlike the oxidized and lipoamide two-electron reduced enzyme species, the nadh four-electron reduced enzyme is highly sensitive to unfolding by urea. los ... | 1991 | 1765065 |
| melibiose is hydrolyzed exocellularly by an inducible exo-alpha-galactosidase in azotobacter vinelandii. | azotobacter vinelandii hydrolyzed melibiose exocellularly, leading to an accumulation of free glucose and galactose in the medium. this enzyme could also be induced by galactose, raffinose, and stachyose. the alpha-galactosidase activity could be detected quantitatively by using p-nitrophenyl-alpha-galactopyranoside as a substrate for intact cells. chloramphenicol totally inhibited the induction of this enzyme. however, benzyl alcohol inhibited the secretion of this enzyme but did not inhibit th ... | 1990 | 2167631 |
| identification of sulfurtransferase enzymes in azotobacter vinelandii. | rhodanese and 3-mercaptopyruvate sulphurtransferase have been identified in a. vinelandii. two distinct active fractions of the two sulphur transferases were obtained after fplc ion-exchange chromatography of material partially purified from crude extracts. rhodanese has been purified to homogeneity, and it consists of one polypeptide chain of mr ca 25,000. a partial purification of 3-mercaptopyruvate sulphurtransferase was obtained. | 1991 | 1991505 |
| kinetic analysis of the interaction of nitric oxide with the membrane-associated, nickel and iron-sulfur-containing hydrogenase from azotobacter vinelandii. | the effects of nitric oxide (no) on the membrane-associated form of the nickel and iron-sulfur-containing hydrogenase from azotobacter vinelandii have been investigated. in the presence of h2 and an electron acceptor (turnover conditions), no acts as a noncompetitive inhibitor vs. methylene blue (ki = 12 microm). there is no element of competition between no and h2, implying that the site of no action is not the h2-activating site of the hydrogenase. when the membrane-associated hydrogenase is i ... | 1991 | 1998716 |
| circular dichroism and magnetic circular dichroism of azotobacter vinelandii ferredoxin i. | room temperature circular dichroism (cd) and low temperature magnetic circular dichroism (mcd) spectra of air-oxidized and dithionite-reduced azotobacter vinelandii ferredoxin i (fdi), a [( 4fe-4s]2+/1+, [3fe-4s]1+/0) protein, are reported. unlike the cd of oxidized fdi, the cd of dithionite-reduced fdi exhibits significant ph dependence, consistent with protonation-deprotonation at or near the cluster reduced: the [3fe-4s] cluster. the mcd of reduced fdi, which originates in the paramagnetic re ... | 1991 | 2009261 |
| transition-state analysis of a vmax mutant of amp nucleosidase by the application of heavy-atom kinetic isotope effects. | the transition state of the vmax mutant of amp nucleosidase from azotobacter vinelandii [leung, h. b., & schramm, v. l. (1981) j. biol. chem. 256, 12823-12829] has been characterized by heavy-atom kinetic isotope effects in the presence and absence of mgatp, the allosteric activator. the enzyme catalyzes hydrolysis of the n-glycosidic bond of amp at approximately 2% of the rate of the normal enzyme with only minor changes in the km for substrate, the activation constant for mgatp, and the ki for ... | 1991 | 2021651 |
| the n-terminal and c-terminal portions of nifv are encoded by two different genes in clostridium pasteurianum. | the nifv gene products from azotobacter vinelandii and klebsiella pneumoniae share a high level of primary sequence identity and are proposed to catalyze the synthesis of homocitrate. while searching for potential nif (nitrogen fixation) genes within the genomic region located downstream from the nifn-b gene of clostridium pasteurianum, we observed two open reading frames (orfs) whose deduced amino acid sequences exhibit nonoverlapping sequence identity to different portions of the nifv gene pro ... | 1991 | 2022611 |
| the alpha-ketoacid dehydrogenase complexes. sequence similarity of rat pyruvate dehydrogenase with escherichia coli and azotobacter vinelandii alpha-ketoglutarate dehydrogenase. | the pyruvate dehydrogenase complex and the alpha-ketoglutarate dehydrogenase complex are multienzyme complexes consisting of three different enzymes. no significant similarity has been reported among the dehydrogenases which are component enzymes of these complexes, despite the presence of homology among the other component enzymes. here we isolated cdnas for the alpha and beta subunits of rat pyruvate dehydrogenase and they exhibited a significant similarity of the amino acid sequences among ra ... | 1991 | 2025639 |
| on the fad-induced dimerization of apo-lipoamide dehydrogenase from azotobacter vinelandii and pseudomonas fluorescens. kinetics of reconstitution. | the apoenzymes of lipoamide dehydrogenase from pig heart and from pseudomonas fluorescens were prepared at ph 2.7 and ph 4.0, respectively, using a hydrophobic interaction chromatography procedure recently developed for lipoamide dehydrogenase from azotobacter vinelandii and other flavoproteins [van berkel et al. (1988) eur. j. biochem. 178, 197-207]. the apoenzyme from pig heart, having 5% of residual activity, shows an equilibrium between the monomeric and dimeric species. both the yield and t ... | 1991 | 2029906 |
| the delta nifb (or delta nife) femo cofactor-deficient mofe protein is different from the delta nifh protein. | we have examined three strains of azotobacter vinelandii, which contain defined deletions within the nifh, nifb, or nife genes. all three strains accumulate inactive femo cofactor-deficient forms of the mofe protein of nitrogenase. these forms can be activated in vitro by addition of isolated femo cofactor in n-methylformamide. although the phenotypes of these strains are superficially the same, our characterizations demonstrate that the femo cofactor-deficient mofe protein synthesized by the de ... | 1991 | 2037604 |
| molecular biology studies of the uptake hydrogenase of rhodobacter capsulatus and rhodocyclus gelatinosus. | in the photosynthetic bacteria, as in other n2-fixing bacteria, two main enzymes are involved in h2 metabolism: nitrogenase, which catalyses the photoproduction of h2, and a membrane-bound (nife) hydrogenase, which functions as an h2-uptake enzyme. the structural genes for rhodobacter capsulatus and rhodocyclus gelatinosus uptake hydrogenases were isolated and sequenced. they present the same organization, with the gene encoding the small subunit (hups) (molecular masses 34.2 and 34.6 kda, respe ... | 1990 | 2094292 |
| expression, nucleotide sequence and mutational analysis of two open reading frames in the nif gene region of anabaena sp. strain pcc7120. | a 1.8 kb transcript corresponding to a region of the anabaena 7120 chromosome 4 kb downstream of the nifhdk operon appears 12-18 h after heterocyst induction. the dna corresponding to this transcript was sequenced and found to contain two open reading frames, designated orf 1 and orf 2. two polypeptides, of 30 kda and 13 kda, encoded by these orfs were expressed in escherichia coli. an apparent start site for the transcript, detected by s1 nuclease protection, was located 42 bp upstream of the a ... | 1990 | 2115111 |
| physical, chemical and immunological properties of the bacterioferritins of escherichia coli, pseudomonas aeruginosa and azotobacter vinelandii. | the 70-amino-acid-residue n-terminal sequence of the bacterioferritin (bfr) of azotobacter vinelandii was determined and shown to be highly similar to the n-terminal sequences of the escherichia coli and nitrobacter winogradskyi bacterioferritins. electrophoretic and immunological analyses further indicate that the bacterioferritins of e. coli, a. vinelandii and pseudomonas aeruginosa are closely related. a novel, two-subunit assembly state that predominates over the 24-subunit form of bfr at lo ... | 1991 | 1904771 |
| the gene encoding dinitrogenase reductase 2 is required for expression of the second alternative nitrogenase from azotobacter vinelandii. | under diazotrophic conditions in the absence of molybdenum (mo) and vanadium (v), azotobacter vinelandii reduces n2 to nh4+ by using nitrogenase 3 (encoded by anfhdgk). however, dinitrogenase reductase 2 (encoded by vnfh) is also expressed under these conditions even though this protein is a component of the v-containing alternative nitrogenase. mutant strains that lack dinitrogenase reductase 2 (vnfh-) grow slower than the wild-type strain in n-free, mo-, and v-deficient medium. in this medium, ... | 1991 | 1906063 |
| bacterial siderophores: structures of pyoverdins pt, siderophores of pseudomonas tolaasii ncppb 2192, and pyoverdins pf, siderophores of pseudomonas fluorescens ccm 2798. identification of an unusual natural amino acid. | pyoverdins were isolated and characterized respectively from the cultures of pseudomonas tolaasii ncppb 2192 (pyoverdins pt, pt a, and pt b) and pseudomonas fluorescens ccm 2798 (pyoverdins pf/1, pf/2, pf, pf/3/1, and pf/3/2) each grown in iron-deficient conditions. their structures were established by using fab-ms, nmr, and cd techniques. these siderophores are chromopeptides, and all but one (pyoverdin pf/3/3) possess at the n-terminal end of their peptide chain the same chromophore that has b ... | 1990 | 2125501 |
| [bacterial regrowth in drinking water. iv. bacterial flora in fresh and stagnant water in drinking water purification and in the drinking water distribution system]. | six dead end water pipes were installed inside a zurich drinking water plant and five others over a distance of 12 km along the distribution system and the water was left stagnating in there for 2 weeks. a total of 1508 bacteria from fresh and stagnating water were isolated and identified. of these, 241 bacterial isolates from the distribution system were examined using the nutrient-tolerance test, i.e. testing the ability to grow in tap water and in media with low and very high nutrient content ... | 1990 | 2261054 |
| growth of azotobacter vinelandii with correlation of coulter cell size, flow cytometric parameters, and ultrastructure. | when azotobacter vinelandii is grown under nitrogen-fixing conditions, the mean cell volume fluctuates from 2.7 to 6.6 microns 3 as determined using a coulter counter. when nh4cl is supplied as nitrogen source, the mean cell volume fluctuates from 4.6 to 7.4 microns3. parallel experiments using flow cytometric measurements show similar characteristic fluctuations in the narrow forward angle light scattering signal and also in cellular protein content as determined using fluorescein isothiocyanat ... | 1990 | 2125552 |
| genomic imprinting in microorganisms. | genomic imprinting is an epigenetic mark introduced on a dna molecule without alteration of the base sequence. upon replication, the primary mark is propagated to the daughter dna molecules. epigenetic dna modification often serves as a regulatory signal and may play a crucial role in many developmental processes. although this mode of gene regulation was first discovered in multicellular eukaryotes, cases of imprinting have been recently found in lower eukaryotes, bacteria and phage. thus it ma ... | 1990 | 2144972 |
| a 31p-nuclear-magnetic-resonance study of nadph-cytochrome-p-450 reductase and of the azotobacter flavodoxin/ferredoxin-nadp+ reductase complex. | 31p-nuclear-magnetic-resonance spectroscopy has been employed to probe the structure of the detergent-solubilized form of liver microsomal nadph--cytochrome-p-450 reductase. in addition to the resonances due to the fmn and fad coenzymes, additional phosphorus resonances are observed and are assigned to the tightly bound adenosine 2'-phosphate (2'-amp) and to phospholipids. the phospholipid content was found to vary with the preparation; however, the 2'-amp resonance was observed in all preparati ... | 1990 | 2115440 |
| structural and chemical properties of a flavodoxin from anabaena pcc 7119. | structural and chemical properties of a flavodoxin from anabaena pcc 7119 are described. the first 36 residues of the amino-terminal amino acid sequence have been determined and show extensive homology with flavodoxins isolated from other sources. anabaena flavodoxin exhibits a net negative change (-3) in the helix-1 segment as found with other cyanobacterial flavodoxins synechococcus 6301 (anacystis nidulans) and nostoc mac, but in contrast to the net positive charge found in this region in the ... | 1990 | 2119231 |
| analysis of azotobacter vinelandii strains containing defined deletions in the nifd and nifk genes. | strains of azotobacter vinelandii which contain defined deletions within the nifd and nifk genes which encode, respectively, the alpha and beta subunits of the mofe protein of nitrogenase were analyzed. when synthesized without its partner, the beta subunit accumulated as a soluble beta 4 tetramer. in contrast, when the alpha subunit was present without its partner, it accumulated primarily as an insoluble aggregate. the solubility of this protein was increased by the presence of a form of the b ... | 1990 | 2120192 |
| genetic characterization of the stabilizing functions of a region of broad-host-range plasmid rk2. | one of the regions responsible for the stable inheritance of the broad-host-range plasmid rk2 is contained within the psti c fragment, located from coordinates 30.8 to 37.0 kb (p.n. saurugger, o. hrabak, h. schwab, and r.m. lafferty, j. biotechnol. 4:333-343, 1986). genetic analysis of this 6.2-kb region demonstrated that no function was present that stabilized by selectively killing plasmid-free segregants. the sequence from 36.0 to 37.0 kb mediated a twofold increase in plasmid copy number, bu ... | 1990 | 2121707 |
| role for the nitrogenase mofe protein alpha-subunit in femo-cofactor binding and catalysis. | two components constitute mo-dependent nitrogenase (ec 1.18.6.1)--the fe protein (a homodimer encoded by nifh) and the mofe protein (an alpha 2 beta 2 tetramer encoded by nifdk). the mofe protein provides the substrate-binding site and probably contains six prosthetic groups of two types--four fe-s centres and two fe- and mo-containing cofactors. to determine the distribution and catalytic function of these metalloclusters, we and others are attempting to change the catalytic and spectroscopic f ... | 1990 | 2153269 |
| site-directed mutagenesis of azotobacter vinelandii ferredoxin i: [fe-s] cluster-driven protein rearrangement. | azotobacter vinelandii ferredoxin i is a small protein that contains one [4fe-4s] cluster and one [3fe-4s] cluster. recently the x-ray crystal structure has been redetermined and the fdxa gene, which encodes the protein, has been cloned and sequenced. here we report the site-directed mutation of cys-20, which is a ligand of the [4fe-4s] cluster in the native protein, to alanine and the characterization of the protein product by x-ray crystallographic and spectroscopic methods. the data show that ... | 1990 | 2153958 |
| precursor activation in a pyoverdine biosynthesis. | the siderophore produced by azotobacter vinelandii strain uw belongs to a large family of peptidic siderophores collectively called pyoverdines. the biosynthesis of the peptidyl moiety of this siderophore was shown to involve activation of the constituent amino acids as their adenylates, as demonstrated by amino acid-dependent atp-[32p]pyrophosphate exchange. the enzyme system responsible for this activation was partially purified by chromatographic techniques. | 1990 | 2156571 |
| pulsed electron paramagnetic resonance studies of the interaction of mg-atp and d2o with the iron protein of nitrogenase. | mg-atp binds to the iron protein component of nitrogenase. the magnetic field dependence of the linear electric field effect (lefe) in pulsed epr is consistent with a single 4fe-4s cluster. the lefe is virtually unaltered when mg-atp is bound. electron spin echo envelope modulation techniques were employed to evaluate the possibility of a magnetic interaction between 31p of mg-atp and the fe-s center of the iron protein. none was detected. however, weak modulations possibly attributable to pepti ... | 1990 | 2159783 |
| apodinitrogenase: purification, association with a 20-kilodalton protein, and activation by the iron-molybdenum cofactor in the absence of dinitrogenase reductase. | the azotobacter vinelandii mutant strain uw45 contains a mutation in the nifb gene and produces an inactive dinitrogenase protein that can be activated by the addition of purified iron-molybdenum cofactor (femoco). this femoco-deficient dinitrogenase (apo i) has now been purified 96-fold to greater than 95% purity and is femoco-activatable to 2200 nmol of c2h2 reduced/(min.mg of protein). the apo i complex was found to contain two molecules of a 20-kda protein, in addition to the alpha 2 beta 2 ... | 1990 | 2162195 |
| cloning and mutagenesis of genes encoding the cytochrome bd terminal oxidase complex in azotobacter vinelandii: mutants deficient in the cytochrome d complex are unable to fix nitrogen in air. | the genome of azotobacter vinelandii contains dna sequences homologous to the structural genes for the escherichia coli cytochrome bd terminal oxidase complex. two recombinant clones bearing cyda- and cydb-like sequence were isolated from an a. vinelandii gene library and subcloned into the plasmid vector pacyc184. physical mapping demonstrated that the cyda- and cydb-like regions in a. vinelandii are contiguous. the cydab and flanking dna was mutagenized by the insertion of tn5-b20. mutations i ... | 1990 | 2170336 |
| complementation of escherichia coli sigma 54 (ntra)-dependent formate hydrogenlyase activity by a cloned thiobacillus ferrooxidans ntra gene. | the ntra gene of thiobacillus ferrooxidans was cloned by complementation of an escherichia coli ntra mutant that was unable to produce gas via the sigma 54 (ntra)-dependent formate hydrogenlyase pathway. analysis of the dna sequence showed that the t. ferrooxidans ntra gene coded for a protein of 475 amino acids (calculated mr, 52,972). the t. ferrooxidans ntra protein had 49, 44, 33, and 18% amino acid similarity with the ntra proteins of klebsiella pneumoniae, azotobacter vinelandii, rhizobium ... | 1990 | 2198257 |
| study of vitreoscilla globin (vgb) gene expression and promoter activity in e. coli through transcriptional fusion. | bacterial hemoglobin (vthb) is produced by the gram-negative bacterium, vitreoscilla, in large quantity in response to hypoxic environmental conditions. the vgb gene coding for vthb has been cloned in e. coli where it is expressed strongly by its natural promoter. the expression of the vgb gene in vitreoscilla is transcriptionally regulated by oxygen. when e. coli cells were shifted from 20% to 5% oxygen, vgb specific transcript increased. in e. coli cells with plasmids carrying transcriptional ... | 1990 | 2198533 |
| genes required for formation of the apomofe protein of klebsiella pneumoniae nitrogenase in escherichia coli. | a binary plasmid system was used to produce nitrogenase components in escherichia coli and subsequently to define a minimum set of nitrogen fixation (nif) genes required for the production of the iron-molybdenum cofactor (femoco) reactivatable apomolybdenum-iron (apomofe) protein of nitrogenase. the active mofe protein is an alpha 2 beta 2 tetramer containing two femoco clusters and 4 fe4s4 p centers (for review see, orme-johnson, w.h. (1985) annu. rev. biophys. biophys. chem. 14, 419-459). the ... | 1990 | 2203791 |