Journal articles: 'Norr'

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Büsch, Andrea, Anne Pohlmann, Bärbel Friedrich, and Rainer Cramm. "A DNA Region Recognized by the Nitric Oxide-Responsive Transcriptional Activator NorR Is Conserved in β- and γ-Proteobacteria." Journal of Bacteriology 186, no. 23 (December 1, 2004): 7980–87. http://dx.doi.org/10.1128/jb.186.23.7980-7987.2004.

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ABSTRACT The σ54-dependent regulator NorR activates transcription of target genes in response to nitric oxide (NO) or NO-generating agents. In Ralstonia eutropha H16, NorR activates transcription of the dicistronic norAB operon that encodes NorA, a protein of unknown function, and NorB, a nitric oxide reductase. A constitutively activating NorR derivative (NorR′), in which the N-terminal signaling domain was replaced by MalE, specifically bound to the norAB upstream region as revealed by gel retardation analysis. Within a 73-bp DNA segment protected by MalE-NorR′ in a DNase I footprint assay, three conserved inverted repeats, GGT-(N7)-ACC (where N is any base), that we consider to be NorR-binding boxes were identified. Mutations altering the spacing or the base sequence of these repeats resulted in an 80 to 90% decrease of transcriptional activation by wild-type NorR. Genome database analyses demonstrate that the GT-(N7)-AC core of the inverted repeat is found in several proteobacteria upstream of gene loci encoding proteins of nitric oxide metabolism, including nitric oxide reductase (NorB), flavorubredoxin (NorV), NO dioxygenase (Hmp), and hybrid cluster protein (Hcp).

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Cramm, R., A. Büsch, and K. Strube. "NO-dependent transcriptional activation of gene expression in Ralstonia eutropha H16." Biochemical Society Transactions 34, no. 1 (January 20, 2006): 182–84. http://dx.doi.org/10.1042/bst0340182.

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The σ54-dependent transcriptional regulator NorR of Ralstonia eutropha H16 activates gene expression in response to nitric oxide (NO). The N-terminal domain of NorR is thought to be involved in signal perception. A C112S exchange within this domain abolished promoter activation by the mutated protein, indicating that Cys112 is essential for the signalling mechanism of NorR. The DNA region recognized by NorR contains three copies of a conserved element termed the NorR-box. Alteration of bases within any of the NorR-boxes resulted in a significant decrease in promoter activation. Therefore all three boxes have to be recognized by NorR to activate its target promoter. NorR controls expression of an operon that encodes a redox-active non-haem-iron protein NorA and an NO reductase NorB. NorA exerts a negative effect on signal-dependent promoter activation by NorR. Optical spectroscopy of purified NorA indicates that the reduced protein can react with NO to form a ferrous nitrosyl adduct. Hence, NO binding by NorA opens up the possibility that NorA and NorR compete for NO in the cytoplasm.

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Büsch, A., K. Strube, B. Friedrich, and R. Cramm. "Transcriptional regulation of nitric oxide reduction in Ralstonia eutropha H16." Biochemical Society Transactions 33, no. 1 (February 1, 2005): 193–94. http://dx.doi.org/10.1042/bst0330193.

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Nitric oxide reduction in Ralstonia eutropha H16 is catalysed by the quinol-dependent NO reductase NorB. norB and the adjacent norA form an operon that is controlled by the σ54-dependent transcriptional activator NorR in response to NO. A NorR derivative containing MalE in place of the N-terminal domain binds to a 73 bp region upstream of norA that includes three copies of the putative upstream activator sequence GGT-(N7)-ACC. Mutations altering individual bases of this sequence resulted in an 80–90% decrease in transcriptional activation by wild-type NorR. Similar motifs are present in several proteobacteria upstream of genes encoding proteins of NO metabolism. The N-terminal domain of NorR contains a GAF module and is hypothesized to interact with a signal molecule. A NorR derivative lacking this domain activates the norAB promoter constitutively. Amino acid exchanges within the GAF module identified a cysteine residue that is essential for promoter activation by NorR. Signal sensing by NorR is negatively modulated by the iron-containing protein NorA.

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Truong-Bolduc, Que Chi, Xiamei Zhang, and David C. Hooper. "Characterization of NorR Protein, a Multifunctional Regulator of norA Expression in Staphylococcus aureus." Journal of Bacteriology 185, no. 10 (May 15, 2003): 3127–38. http://dx.doi.org/10.1128/jb.185.10.3127-3138.2003.

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ABSTRACT We characterized a Staphylococcus aureus norA gene expression regulator, NorR, initially identified from its binding to the norA promoter. The norR gene was 444 bp in length, located ∼7 kb upstream from the norA gene, and encoded a predicted 17.6-kDa protein. Overexpression of norR in wild-type S. aureus strain ISP794 led to a fourfold decrease in sensitivity to quinolones and ethidium bromide and an increase in the level of norA transcripts, suggesting that NorR acts as a positive regulator of norA expression. Overexpression of norR in sarA and agr mutants did not alter quinolone sensitivity or levels of norA transcription, indicating that the presence of these two global regulatory systems is necessary for NorR to affect the expression of norA. Insertion and disruption of norR in ISP794 increased resistance to quinolones by 4- to 16-fold but had no effect on norA transcription, suggesting that NorR acts as a repressor for another unidentified efflux pump or pumps. These mutants also exhibited an exaggerated clumping phenotype in liquid media, which was complemented fully by a plasmid-encoded norR gene. Collectively, these results indicate that NorR is a multifunctional regulator, affecting cell surface properties as well as the expression of NorA and likely other multidrug resistance efflux pumps.

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Klink, Andrea, Bettina Elsner, Katja Strube, and Rainer Cramm. "Characterization of the Signaling Domain of the NO-Responsive Regulator NorR from Ralstonia eutropha H16 by Site-Directed Mutagenesis." Journal of Bacteriology 189, no. 7 (February 2, 2007): 2743–49. http://dx.doi.org/10.1128/jb.01865-06.

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ABSTRACT In Ralstonia eutropha H16, the nitric oxide (NO)-responsive transcriptional activator NorR controls the expression of a dicistronic operon that encodes a membrane-bound NO reductase, NorB, and a protein of unknown function, NorA. The N-terminal domain (NTD) of NorR is responsible for perception of the signal molecule, nitric oxide. Thirteen out of 29 conserved residues of the NTD were exchanged by site-directed mutagenesis. Replacement of R63, R72, D93, D96, C112, D130, or F137 strongly decreased NorR-dependent promoter activation, while the exchange of Y95 or H110 led to an increase in promoter activity compared to that of the wild type. A purified truncated NorR comprising only the NTD (NorR-NTD) contained one iron atom per molecule and was able to bind NO in the as-isolated state. Based on the iron content of NorR-NTD proteins with single amino acid replacements, residues R72, D93, D96, C112, and D130 are likely candidates for iron ligands. Residues R63, Y95, and H110 appear not to be involved in NO binding but may take part in subsequent steps of the signal transduction mechanism of NorR.

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Tucker, Nicholas P., Benoît D'Autréaux, David J. Studholme, Stephen Spiro, and Ray Dixon. "DNA Binding Activity of the Escherichia coli Nitric Oxide Sensor NorR Suggests a Conserved Target Sequence in Diverse Proteobacteria." Journal of Bacteriology 186, no. 19 (October 1, 2004): 6656–60. http://dx.doi.org/10.1128/jb.186.19.6656-6660.2004.

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ABSTRACT The Escherichia coli nitric oxide sensor NorR was shown to bind to the promoter region of the norVW transcription unit, forming at least two distinct complexes detectable by gel retardation. Three binding sites for NorR and two integration host factor binding sites were identified in the norR-norV intergenic region. The derived consensus sequence for NorR binding sites was used to search for novel members of the E. coli NorR regulon and to show that NorR binding sites are partially conserved in other members of the proteobacteria.

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Tucker, N. P., B. D'Autréaux, S. Spiro, and R. Dixon. "Mechanism of transcriptional regulation by the Escherichia coli nitric oxide sensor NorR." Biochemical Society Transactions 34, no. 1 (January 20, 2006): 191–94. http://dx.doi.org/10.1042/bst0340191.

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Nitric oxide (NO) is a highly reactive water-soluble gas encountered by bacteria endogenously as an intermediate of denitrification and exogenously as one of the radical species deployed by macrophages against invading pathogens. Bacteria therefore require a mechanism to detoxify NO. Escherichia coli flavorubredoxin and its associated oxidoreductase, encoded by the norV and norW genes respectively, reduces NO to nitrous oxide under anaerobic conditions. Transcription of the norVW genes is activated in response to NO by the σ54-dependent regulator NorR, a member of the prokaryotic enhancer binding protein family. NorR binds co-operatively to three enhancer sites to regulate transcription of both norVW and the divergently transcribed norR gene. In the present paper, we show that disruption of any one of the three GT-(N7)-AC NorR binding sites in the norR–norVW intergenic region prevents both activation of norVW expression and autogenous repression of the norR promoter by NorR. We have recently demonstrated that the N-terminal GAF (cGMP-specific and -stimulated phosphodiesterases, Anabaena adenylate cyclases and Escherichia coli FhlA) domain of NorR contains a non-haem mononuclear iron centre and senses NO by formation of a mono-nitrosyl iron complex. Site-directed mutagenesis has identified candidate protein ligands to the ferrous iron centre in the GAF domain.

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Bush, Matthew, Tamaswati Ghosh, Nicholas Tucker, Xiaodong Zhang, and Ray Dixon. "Transcriptional regulation by the dedicated nitric oxide sensor, NorR: a route towards NO detoxification." Biochemical Society Transactions 39, no. 1 (January 19, 2011): 289–93. http://dx.doi.org/10.1042/bst0390289.

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A flavorubredoxin and its associated oxidoreductase (encoded by norV and norW respectively) detoxify NO (nitric oxide) to form N2O (nitrous oxide) under anaerobic conditions in Escherichia coli. Transcription of the norVW genes is activated in response to NO by the σ54-dependent regulator and dedicated NO sensor, NorR, a member of the bacterial enhancer-binding protein family. In the absence of NO, the catalytic activity of the central ATPase domain of NorR is repressed by the N-terminal regulatory domain that contains a non-haem iron centre. Binding of NO to this centre results in the formation of a mononitrosyl iron species, enabling the activation of ATPase activity. Our studies suggest that the highly conserved GAFTGA loop in the ATPase domain, which engages with the alternative σ factor σ54 to activate transcription, is a target for intramolecular repression by the regulatory domain. Binding of NorR to three conserved enhancer sites upstream of the norVW promoter is essential for transcriptional activation and promotes the formation of a stable higher-order NorR nucleoprotein complex. We propose that enhancer-driven assembly of this oligomeric complex, in which NorR apparently forms a DNA-bound hexamer in the absence of NO, provides a ‘poised’ system for transcriptional activation that can respond rapidly to nitrosative stress.

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Tucker, N., B. D'Autréaux, S. Spiro, and R. Dixon. "DNA binding properties of the Escherichia coli nitric oxide sensor NorR: towards an understanding of the regulation of flavorubredoxin expression." Biochemical Society Transactions 33, no. 1 (February 1, 2005): 181–83. http://dx.doi.org/10.1042/bst0330181.

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Nitric oxide is an intermediate of denitrification, and is one of the radical species deployed by macrophages against invading pathogens, therefore bacterial responses to NO are of considerable importance. The Escherichia coli flavorubredoxin and its associated oxidoreductase reduce NO to nitrous oxide under anaerobic conditions, and are encoded by the norVW transcription unit. Expression of norVW requires the NO sensing regulatory protein NorR and is dependent on RNA polymerase containing the alternative sigma factor, σ54. We have purified NorR and shown that it binds to three sites in the norVW promoter region, located 75–140 bp upstream of the experimentally verified transcription start site. We have also identified two binding sites for the integration host factor, one between the NorR sites and the σ54-RNA polymerase binding site, and a second downstream of the norVW transcription start site. Comparison of the norVW promoters of enteric bacteria along with known and putative NorR-regulated promoters from Vibrio, Ralstonia and Pseudomonas species suggests that NorR binding sites contain an invariant GT(N7)AC motif flanking an AT-rich central region. The identification of a consensus for NorR binding sites will help to elucidate additional members of the NorR regulon.

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10

Zhao, Jujiao, Bo Shang, and Jun Zhai. "N-Doped Graphene as an Efficient Metal-Free Electrocatalyst for Indirect Nitrate Reduction Reaction." Nanomaterials 11, no. 9 (September 17, 2021): 2418. http://dx.doi.org/10.3390/nano11092418.

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N-doped graphene samples with different N species contents were prepared by a two-step synthesis method and evaluated as electrocatalysts for the nitrate reduction reaction (NORR) for the first time. In an acidic solution with a saturated calomel electrode as reference, the pyridinic-N dominant sample (NGR2) had an onset of 0.932 V and a half-wave potential of 0.833 V, showing the superior activity towards the NORR compared to the pyrrolic-N dominant N-doped graphene (onset potential: 0.850 V, half-wave potential: 0.732 V) and the pure graphene (onset potential: 0.698 V, half-wave potential: 0.506 V). N doping could significantly boost the NORR performance of N-doped graphene, especially the contribution of pyridinic-N. Density functional theory calculation revealed the pyridinic-N facilitated the desorption of NO, which was kinetically involved in the process of the NORR. The findings of this work would be valuable for the development of metal-free NORR electrocatalysts.

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11

Nedoma, Robert. "Um uppruna norr. ørhœfi, ørœfi." Orð og tunga 18 (June 1, 2016): 103–9. http://dx.doi.org/10.33112/ordogtunga.18.6.

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This paper deals with the etymology of OWN ør(h)œfi n. ‘wilderness, desert; harbourless coast’ (NIcel. öræfi also ‘shallow [bank]’), a formation with the prefi x ør- ‘out of, away from, very, un-’. Prior suggestions made by Bloomfi eld (: hǫfn ‘harbor’) and Holthausen (: hœfi ‘sth. that is convenient, suitable’)are rejected on phonological, morphological and semantic grounds. Conversly, it is argued that -hœfi is to be connected with OHG huoba, OS hōva ‘farmed land, farm(stead)’ so that OWN ør-hœf-i < PGmc. *uz-hōb-ij a- is an exocentric formation which originally denoted ‘sth. that is away from the farmed land, undeveloped area’, thus ‘wilderness, desert’. Hence, the meaning ‘harbourless coast’ is secondary.

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Pullan, Steven T., Mark D. Gidley, Richard A. Jones, Jason Barrett, Tania M. Stevanin, Robert C. Read, Jeffrey Green, and Robert K. Poole. "Nitric Oxide in Chemostat-Cultured Escherichia coli Is Sensed by Fnr and Other Global Regulators: Unaltered Methionine Biosynthesis Indicates Lack of S Nitrosation." Journal of Bacteriology 189, no. 5 (December 22, 2006): 1845–55. http://dx.doi.org/10.1128/jb.01354-06.

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ABSTRACT We previously elucidated the global transcriptional responses of Escherichia coli to the nitrosating agent S-nitrosoglutathione (GSNO) in both aerobic and anaerobic chemostats, demonstrated the expression of nitric oxide (NO)-protective mechanisms, and obtained evidence of critical thiol nitrosation. The present study was the first to examine the transcriptome of NO-exposed E. coli in a chemostat. Using identical conditions, we compared the GSNO stimulon with the stimulon of NO released from two NO donor compounds {3-[2-hydroxy-1-(1-methyl-ethyl)-2-nitrosohydrazino]-1-propanamine (NOC-5) and 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamine (NOC-7)} simultaneously and demonstrated that there were marked differences in the transcriptional responses to these distinct nitrosative stresses. Exposure to NO did not induce met genes, suggesting that, unlike GSNO, NO does not elicit homocysteine S nitrosation and compensatory increases in methionine biosynthesis. After entry into cells, exogenous methionine provided protection from GSNO-mediated killing but not from NO-mediated killing. Anaerobic exposure to NO led to up-regulation of multiple Fnr-repressed genes and down-regulation of Fnr-activated genes, including nrfA, which encodes cytochrome c nitrite reductase, providing strong evidence that there is NO inactivation of Fnr. Other global regulators apparently affected by NO were IscR, Fur, SoxR, NsrR, and NorR. We tried to identify components of the NorR regulon by performing a microarray comparison of NO-exposed wild-type and norR mutant strains; only norVW, encoding the NO-detoxifying flavorubredoxin and its cognate reductase, were unambiguously identified. Mutation of norV or norR had no effect on E. coli survival in mouse macrophages. Thus, GSNO (a nitrosating agent) and NO have distinct cellular effects; NO more effectively interacts with global regulators that mediate adaptive responses to nitrosative stress but does not affect methionine requirements arising from homocysteine nitrosation.

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Bulatov, Ivan Aleksandrovich. "National Association of Russian Explorers: brief history." Genesis: исторические исследования, no. 2 (February 2021): 8–17. http://dx.doi.org/10.25136/2409-868x.2021.2.35110.

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The subject of this research is the history of development of the National Association of Russian Explorers (NORR) – one of the youth organizations of White émigré. NORR was founded in 1928, and in the 1930s became the largest emigrant youth organization. However, after the World War II it basically ceased its activity. The first members of NORR came from the Scout movement, founding their ideology on the criticism of parent organization. Nevertheless, it did not prevent them from borrowing the most effective methods of scouting and adapt them to their ideology. The ideology was based on the Russian nationalism of imperial type, patriotism and militarism. Peter the Great was selected as the symbol of all the ideas. Leaning on the wide variety of source, including the materials introduced into the scientific discourse for the first time, the article examines the phenomenon of national upbringing in extracurricular organizations. The main conclusion consists in the thesis that the burst in popularity and subsequent decline of the National Association of Russian Explorers were associated namely with the national-patriotic component of upbringing, which was of crucial in the conditions of emigration. The fact that the leader of this association P. N. Bogdanovich, was able to offer a system of Russian national upbringing to general emigrant community was the key factor of its initial success. After World War II, NORR has lost many of its active members and winded down its activity; and the Russian Scouts implemented more national elements into their work, attracting patriotic youth. This brought the activity of NORR to an end.

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Hutchings, Matthew I., Neeraj Mandhana, and Stephen Spiro. "The NorR Protein of Escherichia coli Activates Expression of the Flavorubredoxin Gene norV in Response to Reactive Nitrogen Species." Journal of Bacteriology 184, no. 16 (August 15, 2002): 4640–43. http://dx.doi.org/10.1128/jb.184.16.4640-4643.2002.

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ABSTRACT The Escherichia coli norVW genes encode a flavorubredoxin and NADH:(flavo)rubredoxin reductase, respectively, which are involved in nitric oxide detoxification under anaerobic growth conditions. Here it is shown that the norVW genes also have a role in protection against reactive nitrogen intermediates generated from nitroprusside. Transcription from the norV promoter is activated by the presence of nitroprusside in the growth medium; activation requires the product of a divergently transcribed regulatory gene, norR.

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Truong-Bolduc, Que Chi, and David C. Hooper. "The Transcriptional Regulators NorG and MgrA Modulate Resistance to both Quinolones and β-Lactams in Staphylococcus aureus." Journal of Bacteriology 189, no. 8 (February 2, 2007): 2996–3005. http://dx.doi.org/10.1128/jb.01819-06.

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ABSTRACT MgrA is a known regulator of the expression of several multidrug transporters in Staphylococcus aureus. We identified another regulator of multiple efflux pumps, NorG, by its ability, like that of MgrA, to bind specifically to the promoter of the gene encoding the NorA efflux pump. NorG is a member of the family of the GntR-like transcriptional regulators, and it binds specifically to the putative promoters of the genes encoding multidrug efflux pumps NorA, NorB, NorC, and AbcA. Overexpression of norG produces a threefold increase in norB transcripts associated with a fourfold increase in the level of resistance to quinolones. In contrast, disruption of norG produces no change in the level of transcripts of norA, norB, and norC but causes an increase of at least threefold in the transcript level of abcA, associated with a fourfold increase in resistance to methicillin, cefotaxime, penicillin G, and nafcillin. Overexpression of cloned abcA caused an 8- to 128-fold increase in the level of resistance to all four β-lactam antibiotics. Furthermore, MgrA and NorG have opposite effects on norB and abcA expression. MgrA acts as an indirect repressor for norB and a direct activator for abcA, whereas NorG acts as a direct activator for norB and a direct repressor for abcA.

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Nielsen, Jens Petter. "Nöd och död. Den ryska ockupationen i norr 1809." Nordisk Østforum 34 (2020): 267. http://dx.doi.org/10.23865/noros.v34.2625.

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Wu, Qian, Hao Wang, Shiying Shen, Baibiao Huang, Ying Dai, and Yandong Ma. "Efficient nitric oxide reduction to ammonia on a metal-free electrocatalyst." Journal of Materials Chemistry A 9, no. 9 (2021): 5434–41. http://dx.doi.org/10.1039/d0ta11209g.

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18

Thygesen, Erik, and Lars Gustafsson. "Det sällsamma djuret från norr och andra Science Fiction-berättelser." World Literature Today 64, no. 4 (1990): 656. http://dx.doi.org/10.2307/40146994.

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Strauch, Dieter. "Lundmark, Lennart, Samernas skatteland i Norr- och Västerbotten under 300 år." Zeitschrift der Savigny-Stiftung für Rechtsgeschichte: Germanistische Abteilung 124, no. 1 (August 1, 2007): 646–50. http://dx.doi.org/10.7767/zrgga.2007.124.1.646.

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Sundstrom, Emma. "The Restoration of Norr Malarstrand: A Linear Park of the Stockholm School." Garden History 32, no. 2 (2004): 272. http://dx.doi.org/10.2307/4150386.

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Chisholm, Brian, Michael Blake, and Michael W. Love. "More on Prehistoric Subsistence in the Soconusco Region: Response to Ambrose and Norr." Current Anthropology 34, no. 4 (August 1993): 432–34. http://dx.doi.org/10.1086/204187.

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D'Autréaux, Benoît, Nicholas P. Tucker, Ray Dixon, and Stephen Spiro. "A non-haem iron centre in the transcription factor NorR senses nitric oxide." Nature 437, no. 7059 (September 2005): 769–72. http://dx.doi.org/10.1038/nature03953.

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Bush, Matt, Tamaswati Ghosh, Marta Sawicka, Iain H. Moal, Paul A. Bates, Ray Dixon, and Xiaodong Zhang. "The structural basis for enhancer‐dependent assembly and activation of the AAA transcriptional activator NorR." Molecular Microbiology 95, no. 1 (November 24, 2014): 17–30. http://dx.doi.org/10.1111/mmi.12844.

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Tucker, Nicholas P., Benoît D'Autréaux, Faridoon K. Yousafzai, Shirley A. Fairhurst, Stephen Spiro, and Ray Dixon. "Analysis of the Nitric Oxide-sensing Non-heme Iron Center in the NorR Regulatory Protein." Journal of Biological Chemistry 283, no. 2 (November 14, 2007): 908–18. http://dx.doi.org/10.1074/jbc.m705850200.

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Varela-Raposo, Ana, Catarina Pimentel, Fabio Morais-Silva, Antonio Rezende, Jerônimo C. Ruiz, and Claudina Rodrigues-Pousada. "Role of NorR-like transcriptional regulators under nitrosative stress of the δ-proteobacterium, Desulfovibrio gigas." Biochemical and Biophysical Research Communications 431, no. 3 (February 2013): 590–96. http://dx.doi.org/10.1016/j.bbrc.2012.12.130.

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Truong-Bolduc, Q. C., P. M. Dunman, T. Eidem, and D. C. Hooper. "Transcriptional Profiling Analysis of the Global Regulator NorG, a GntR-Like Protein of Staphylococcus aureus." Journal of Bacteriology 193, no. 22 (September 9, 2011): 6207–14. http://dx.doi.org/10.1128/jb.05847-11.

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The GntR-like protein NorG has been shown to affectStaphylococcus aureusgenes involved in resistance to quinolones and β-lactams, such as those encoding the NorB and AbcA transporters. To identify the target genes regulated by NorG, we carried out transcriptional-profiling assays usingS. aureusRN6390 and its isogenicnorG::catmutant. Our data showed that NorG positively affected the transcription of global regulatorsmgrA,arlS, andsarZ. The three putative drug efflux pump genes most positively affected by NorG were the NorB efflux pump (5.1-fold), the MmpL-like protein SACOL2566 (5.2-fold), and the BcrA-like drug transporter SACOL2525 (5.7-fold) genes. TheS. aureuspredicted MmpL protein showed 53% homology with the MmpL lipid transporter ofMycobacterium tuberculosis, and the putative SACOL2525 protein showed 87% homology with the bacitracin drug transporter BcrA ofStaphylococcus hominis. Two pump genes most negatively affected by NorG were the NorC (4-fold) and AbcA (6-fold) genes. Other categories of genes, such as those participating in amino acid, inorganic ion, or nucleotide transporters and metabolism, were also affected by NorG. Real-time reverse transcription (RT)-PCR assays formgrA,arlS,sarZ,norB,norC,abcA,mmpL, andbcrA-like were carried out to verify microarray data and showed the same level of up- or downregulation by NorG. ThenorGmutant showed a 2-fold increase in resistance to norfloxacin and rhodamine, both substrates of the NorC transporter, which is consistent with the resistance phenotype conferred by overexpression ofnorCon a plasmid. These data indicate that NorG has broad regulatory function inS. aureus.

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Bush, Matthew, Tamaswati Ghosh, Nicholas Tucker, Xiaodong Zhang, and Ray Dixon. "Nitric oxide-responsive interdomain regulation targets the σ54-interaction surface in the enhancer binding protein NorR." Molecular Microbiology 77, no. 5 (August 25, 2010): 1278–88. http://dx.doi.org/10.1111/j.1365-2958.2010.07290.x.

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Mukhopadhyay, P., M. Zheng, L. A. Bedzyk, R. A. LaRossa, and G. Storz. "Prominent roles of the NorR and Fur regulators in the Escherichia coli transcriptional response to reactive nitrogen species." Proceedings of the National Academy of Sciences 101, no. 3 (January 12, 2004): 745–50. http://dx.doi.org/10.1073/pnas.0307741100.

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Tucker, Nicholas P., Tamaswati Ghosh, Matthew Bush, Xiaodong Zhang, and Ray Dixon. "Essential roles of three enhancer sites in σ54-dependent transcription by the nitric oxide sensing regulatory protein NorR." Nucleic Acids Research 38, no. 4 (December 2, 2009): 1182–94. http://dx.doi.org/10.1093/nar/gkp1065.

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Ding, Yanpeng, Yoshikuni Onodera, Jean C. Lee, and David C. Hooper. "NorB, an Efflux Pump in Staphylococcus aureus Strain MW2, Contributes to Bacterial Fitness in Abscesses." Journal of Bacteriology 190, no. 21 (August 22, 2008): 7123–29. http://dx.doi.org/10.1128/jb.00655-08.

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ABSTRACT While remaining a major problem in hospitals, Staphylococcus aureus is now spreading in communities. Strain MW2 (USA400 lineage) and other community methicillin-resistant S. aureus strains most commonly cause skin infections with abscess formation. Multidrug resistance (MDR) efflux pumps contribute to antimicrobial resistance but may also contribute to bacterial survival by removal of environmental toxins. In S. aureus, NorA, NorB, NorC, and Tet38 are chromosomally encoded efflux pumps whose overexpression can confer MDR to quinolones and other compounds (Nor pumps) or tetracyclines alone (Tet38), but the natural substrates of these pumps are not known. To determine the role of these efflux pumps in a natural environment in the absence of antibiotics, we used strain MW2 in a mouse subcutaneous abscess model and compared pump gene expression as determined by reverse transcription-PCR in the abscesses and in vitro. norB and tet38 were selectively upregulated in vivo more than 171- and 24-fold, respectively, whereas norA and norC were downregulated. These changes were associated with an increase in expression of mgrA, which encodes a transcriptional regulator known to affect pump gene expression. In competition experiments using equal inocula of a norB or tet38 mutant and parent strain MW2, each mutant exhibited growth defects of about two- to threefold in vivo. In complementation experiments, a single-copy insertion of norB (but not a single-copy insertion of tet38) in the attB site within geh restored the growth fitness of the norB mutant in vivo. Our findings indicate that some MDR pumps, like NorB, can facilitate bacterial survival when they are overexpressed in a staphylococcal abscess and may contribute to the relative resistance of abscesses to antimicrobial therapy, thus linking bacterial fitness and resistance in vivo.

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Mohannath, Gireesha, Frederic Pontvianne, and Craig S. Pikaard. "Selective nucleolus organizer inactivation in Arabidopsis is a chromosome position-effect phenomenon." Proceedings of the National Academy of Sciences 113, no. 47 (November 7, 2016): 13426–31. http://dx.doi.org/10.1073/pnas.1608140113.

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Nucleolus organizer regions (NORs) are chromosomal loci where hundreds of rRNA genes are clustered. Despite being nearly identical in sequence, specific rRNA genes are selected for silencing during development via choice mechanism(s) that remain unclear. In Arabidopsis thaliana, rRNA gene subtypes that are silenced during development were recently mapped to the NOR on chromosome 2, NOR2, whereas active rRNA genes map to NOR4, on chromosome 4. In a mutant line deficient for ATXR5 or ATXR6-dependent histone H3 lysine 27 (H3K27) monomethylation, we show that millions of base pairs of chromosome 4, including the telomere, TEL4N, and much of NOR4, have been converted to the corresponding sequences of chromosome 2. This genomic change places rRNA genes of NOR2, which are normally silenced, at the position on chromosome 4 where active rRNA genes are normally located. At their new location, NOR2-derived rRNA genes escape silencing, independent of the atxr mutations, indicating that selective rRNA gene silencing is chromosome 2-specific. The chromosome 2 position effect is not explained by the NOR2-associated telomere, TEL2N, which remains linked to the translocated NOR, implicating centromere-proximal sequences in silencing.

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Silva, José Givanildo da, Mariana de Barros, Nataly Diniz de Lima Santos, Patrícia Maria Guedes Paiva, Thiago Henrique Napoleão, Maria José de Sena, Mateus Matiuzzi da Costa, Helinando Pequeno de Oliveira, Maria Aparecida Scatamburlo Moreira, and Rinaldo Aparecido Mota. "Antimicrobial activity of polypyrrole nanoparticles and aqueous extract of Moringa oleifera against Staphylococcus spp. carriers of multi-drug efflux system genes isolated from dairy farms." Journal of Dairy Research 87, no. 3 (August 2020): 309–14. http://dx.doi.org/10.1017/s0022029920000874.

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AbstractOur objectives were to identify genes of the multi-drug efflux system and to evaluate the antimicrobial activities of polypyrrole nanoparticles (PPy-NPs) and aqueous extract of Moringa oleifera against Staphylococcus spp. isolated from dairy farms in Northeast Brazil. Initially, 162 Staphylococcus spp. isolates were subjected to in vitro antimicrobial sensitivity tests. Of these, 35 presented antimicrobial multi-drug resistance phenotypes. These 35 isolates were then referred for the detection of norA, norB, norC, msrA, mgrA, tet-38, and lmrS genes, all of which feature in multi-drug efflux systems. In the isolates carrying the genes, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PPy-NPs and Moringa oleifera aqueous extract were determined. In the molecular analysis of the 35 isolates norA, norC, tet-38, and msrA genes were detected and for the other genes norB, lmrS and mgrA there was no amplification. Antimicrobial activity was verified of PPy-NPs and aqueous extract of Moringa oleifera in Staphylococcus spp. carrying multi-drug efflux system genes. We concluded that there are multi-drug efflux system genes present in the Staphylococcus spp. from the agricultural environment in Northeast Brazil, and that aqueous extract of Moringa oleifera and PPy-NPs show bactericidal activity against these isolates.

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Filenko, N. A., D. F. Browning, and J. A. Cole. "Transcriptional regulation of a hybrid cluster (prismane) protein." Biochemical Society Transactions 33, no. 1 (February 1, 2005): 195–97. http://dx.doi.org/10.1042/bst0330195.

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HCP (hybrid-cluster protein) contains two Fe/S clusters, one of which is a hybrid [4Fe-2S-2O] cluster. Despite intensive study, its physiological function has not been reported. The Escherichia coli hcp gene is located in a two-gene operon with hcr, which encodes an NADH-dependent HCP reductase. E. coli HCP is detected after anaerobic growth with nitrate or nitrite: possible roles for it in hydroxylamine or nitric oxide reduction have been proposed. To study the regulation and role of HCP, an hcp::lacZ fusion was constructed and transformed into fnr, arcA and norR mutant strains of E. coli. Transcription from the hcp promoter was induced during anaerobic growth. Only the fnr mutant was defective in hcp expression. Nitrate- and nitrite-induced transcription from the hcp promoter was activated by the response regulator proteins NarL and NarP. Gel retardation assays were used to show that FNR (fumarate-nitrate regulation) and NarL form a complex with the hcp promoter. Transcription of the hcp-hcr operon initiates at a thymine nucleotide located 31 bp upstream of the translation-initiation codon. HCP has been overexpressed from a recombinant plasmid for physiological studies.

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DeMarco, Carmen E., Laurel A. Cushing, Emmanuel Frempong-Manso, Susan M. Seo, Tinevimbo A. A. Jaravaza, and Glenn W. Kaatz. "Efflux-Related Resistance to Norfloxacin, Dyes, and Biocides in Bloodstream Isolates of Staphylococcus aureus." Antimicrobial Agents and Chemotherapy 51, no. 9 (June 18, 2007): 3235–39. http://dx.doi.org/10.1128/aac.00430-07.

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ABSTRACT Efflux is an important resistance mechanism in Staphylococcus aureus, but its frequency in patients with bacteremia is unknown. Nonreplicate bloodstream isolates were collected over an 8-month period, and MICs of four common efflux pump substrates, with and without the broad-spectrum efflux pump inhibitor reserpine, were determined (n = 232). A reserpine-associated fourfold decrease in MIC was considered indicative of efflux. Strains exhibiting efflux of at least two of the four substrates were identified (“effluxing strains” [n = 114]). For these strains, MICs with or without reserpine for an array of typical substrates and the expression of mepA, mdeA, norA, norB, norC, and qacA/B were determined using quantitative real-time reverse transcription-PCR (qRT-PCR). A fourfold or greater increase in gene expression was considered significant. The most commonly effluxed substrates were ethidium bromide and chlorhexidine (100 and 96% of effluxing strains, respectively). qRT-PCR identified strains overexpressing mepA (5 [4.4%]), mdeA (13 [11.4%]), norA (26 [22.8%]), norB (29 [25.4%]), and norC (19 [16.7%]); 23 strains overexpressed two or more genes. Mutations probably associated with increased gene expression included a MepR-inactivating substitution and norA promoter region insertions or deletions. Mutations possibly associated with increased expression of the other analyzed genes were also observed. Effluxing strains comprised 49% of all strains studied (114/232 strains), with nearly half of these overexpressing genes encoding MepA, MdeA, and/or NorABC (54/114 strains). Reduced susceptibility to biocides may contribute to persistence on environmental surfaces, and efflux of drugs such as fluoroquinolones may predispose strains to high-level target-based resistance.

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Justino, Marta C., Vera M. M. Gonçalves, and Lígia M. Saraiva. "Binding of NorR to three DNA sites is essential for promoter activation of the flavorubredoxin gene, the nitric oxide reductase of Escherichia coli." Biochemical and Biophysical Research Communications 328, no. 2 (March 2005): 540–44. http://dx.doi.org/10.1016/j.bbrc.2005.01.008.

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Bellota-Antón, César, John Munnoch, Kirsty Robb, Katrin Adamczyk, Marco Candelaresi, Anthony W. Parker, Ray Dixon, Matthew I. Hutchings, Neil T. Hunt, and Nicholas P. Tucker. "Spectroscopic analysis of protein Fe–NO complexes." Biochemical Society Transactions 39, no. 5 (September 21, 2011): 1293–98. http://dx.doi.org/10.1042/bst0391293.

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The toxic free radical NO (nitric oxide) has diverse biological roles in eukaryotes and bacteria, being involved in signalling, vasodilation, blood clotting and immunity, and as an intermediate in microbial denitrification. The predominant biological mechanism of detecting NO is through the formation of iron nitrosyl complexes, although this is a deleterious process for other iron-containing enzymes. We have previously applied techniques such as UV–visible and EPR spectroscopy to the analysis of protein Fe–NO complex formation in order to study how NO controls the activity of the bacterial transcriptional regulators NorR and NsrR. These studies have analysed NO-dependent biological activity both in vitro and in vivo using diverse biochemical, molecular and spectroscopic methods. Recently, we have applied ultrafast 2D-IR (two-dimensional IR) spectroscopy to the analysis of NO–protein interactions using Mb (myoglobin) and Cc (cytochrome c) as model haem proteins. The ultrafast fluctuations of Cc and Mb show marked differences, indicating altered flexibility of the haem pockets. We have extended this analysis to bacterial catalase enzymes that are known to play a role in the nitrosative stress response by detoxifying peroxynitrite. The first 2D-IR analysis of haem nitrosylation and perspectives for the future are discussed.

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Truong-Bolduc, Que Chi, Jacob Strahilevitz, and David C. Hooper. "NorC, a New Efflux Pump Regulated by MgrA of Staphylococcus aureus." Antimicrobial Agents and Chemotherapy 50, no. 3 (March 2006): 1104–7. http://dx.doi.org/10.1128/aac.50.3.1104-1107.2006.

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ABSTRACT NorC, a new efflux pump, like NorB, contributes to quinolone resistance that includes resistance to moxifloxacin and sparfloxacin in Staphylococcus aureus. norC expression, like that of norB and tet38, is negatively regulated by MgrA, and overexpression of both norC and norB contributes to the quinolone resistance phenotype of an mgrA mutant.

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Dabrowska, Dorota, Justyna Mozejko-Ciesielska, Tomasz Pokój, and Slawomir Ciesielski. "Transcriptome Changes in Pseudomonas putida KT2440 during Medium-Chain-Length Polyhydroxyalkanoate Synthesis Induced by Nitrogen Limitation." International Journal of Molecular Sciences 22, no. 1 (December 25, 2020): 152. http://dx.doi.org/10.3390/ijms22010152.

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Pseudomonas putida’s versatility and metabolic flexibility make it an ideal biotechnological platform for producing valuable chemicals, such as medium-chain-length polyhydroxyalkanoates (mcl-PHAs), which are considered the next generation bioplastics. This bacterium responds to environmental stimuli by rearranging its metabolism to improve its fitness and increase its chances of survival in harsh environments. Mcl-PHAs play an important role in central metabolism, serving as a reservoir of carbon and energy. Due to the complexity of mcl-PHAs’ metabolism, the manner in which P. putida changes its transcriptome to favor mcl-PHA synthesis in response to environmental stimuli remains unclear. Therefore, our objective was to investigate how the P. putida KT2440 wild type and mutants adjust their transcriptomes to synthesize mcl-PHAs in response to nitrogen limitation when supplied with sodium gluconate as an external carbon source. We found that, under nitrogen limitation, mcl-PHA accumulation is significantly lower in the mutant deficient in the stringent response than in the wild type or the rpoN mutant. Transcriptome analysis revealed that, under N-limiting conditions, 24 genes were downregulated and 21 were upregulated that were common to all three strains. Additionally, potential regulators of these genes were identified: the global anaerobic regulator (Anr, consisting of FnrA, Fnrb, and FnrC), NorR, NasT, the sigma54-dependent transcriptional regulator, and the dual component NtrB/NtrC regulator all appear to play important roles in transcriptome rearrangement under N-limiting conditions. The role of these regulators in mcl-PHA synthesis is discussed.

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Manna, Adhar C., Susham S. Ingavale, MaryBeth Maloney, Willem van Wamel, and Ambrose L. Cheung. "Identification of sarV (SA2062), a New Transcriptional Regulator, Is Repressed by SarA and MgrA (SA0641) and Involved in the Regulation of Autolysis in Staphylococcus aureus." Journal of Bacteriology 186, no. 16 (August 15, 2004): 5267–80. http://dx.doi.org/10.1128/jb.186.16.5267-5280.2004.

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ABSTRACT The expression of genes involved in the pathogenesis of Staphylococcus aureus is known to be controlled by global regulatory loci, including agr, sarA, sae, arlRS, lytSR, and sarA-like genes. Here we described a novel transcriptional regulator called sarV of the SarA protein family. The transcription of sarV is low or undetectable under in vitro conditions but is significantly augmented in sarA and mgrA (norR or rat) (SA0641) mutants. The sarA and mgrA genes act as repressors of sarV expression, as confirmed by transcriptional fusion and Northern analysis data. Purified SarA and MgrA proteins bound specifically to separate regions of the sarV promoter as determined by gel shift and DNase I footprinting assays. The expression of 19 potential target genes involved in autolysis and virulence, phenotypes affected by sarA and mgrA, was evaluated in an isogenic sarV mutant pair. Our data indicated that the sarV gene product played a role regulating some virulence genes and more genes involved in autolysis. The sarV mutant was more resistant to Triton X-100 and penicillin-induced lysis compared to the wild type and the sarA mutant, whereas hyperexpression of sarV in the parental strain or the sarV mutant rendered the resultant strain highly susceptible to lysis. Zymographic analysis of murein hydrolase activity revealed that inactivation of the sarV gene results in decreased extracellular murein hydrolase activity compared to that of wild-type S. aureus. We propose that sarV may be part of the common pathway by which mgrA and sarA gene products control autolysis in S. aureus.

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Truong-Bolduc, Que Chi, and David C. Hooper. "Phosphorylation of MgrA and Its Effect on Expression of the NorA and NorB Efflux Pumps of Staphylococcus aureus." Journal of Bacteriology 192, no. 10 (March 16, 2010): 2525–34. http://dx.doi.org/10.1128/jb.00018-10.

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ABSTRACT MgrA is a global regulator in Staphylococcus aureus that controls the expression of diverse genes encoding virulence factors and multidrug resistance (MDR) efflux transporters. We identified pknB, which encodes the (Ser/Thr) kinase PknB, in the S. aureus genome. PknB was able to autophosphorylate as well as phosphorylate purified MgrA. We demonstrated that rsbU, which encodes a Ser/Thr phosphatase and is involved in the activation of the SigB regulon, was able to dephosphorylate MgrA-P but not PknB-P. Serines 110 and 113 of MgrA were found to be phosphorylated, and Ala substitutions at these positions resulted in reductions in the level of phosphorylation of MgrA. DNA gel shift binding assays using norA and norB promoters showed that MgrA-P was able to bind the norB promoter but not the norA promoter, a pattern which was the reverse of that for unphosphorylated MgrA. The double mutant MgrAS110A-S113A bound to the norA promoter but not the norB promoter. The double mutant led to a 2-fold decrease in norA transcripts and a 2-fold decrease in the MICs of norfloxacin and ciprofloxacin in strain RN6390. Thus, phosphorylation of MgrA results in loss of binding to the norA promoter, but with a gain of the ability to bind the norB promoter. Loss of the ability to phosphorylate MgrA by Ala substitution resulted in increased repression of norA expression and in reductions in susceptibilities to NorA substrates.

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Sánchez-Costa, Mercedes, Alba Blesa, and José Berenguer. "Nitrate Respiration in Thermus thermophilus NAR1: from Horizontal Gene Transfer to Internal Evolution." Genes 11, no. 11 (November 4, 2020): 1308. http://dx.doi.org/10.3390/genes11111308.

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Genes coding for enzymes of the denitrification pathway appear randomly distributed among isolates of the ancestral genus Thermus, but only in few strains of the species Thermus thermophilus has the pathway been studied to a certain detail. Here, we review the enzymes involved in this pathway present in T. thermophilus NAR1, a strain extensively employed as a model for nitrate respiration, in the light of its full sequence recently assembled through a combination of PacBio and Illumina technologies in order to counteract the systematic errors introduced by the former technique. The genome of this strain is divided in four replicons, a chromosome of 2,021,843 bp, two megaplasmids of 370,865 and 77,135 bp and a small plasmid of 9799 pb. Nitrate respiration is encoded in the largest megaplasmid, pTTHNP4, within a region that includes operons for O2 and nitrate sensory systems, a nitrate reductase, nitrate and nitrite transporters and a nitrate specific NADH dehydrogenase, in addition to multiple insertion sequences (IS), suggesting its mobility-prone nature. Despite nitrite is the final product of nitrate respiration in this strain, the megaplasmid encodes two putative nitrite reductases of the cd1 and Cu-containing types, apparently inactivated by IS. No nitric oxide reductase genes have been found within this region, although the NorR sensory gene, needed for its expression, is found near the inactive nitrite respiration system. These data clearly support that partial denitrification in this strain is the consequence of recent deletions and IS insertions in genes involved in nitrite respiration. Based on these data, the capability of this strain to transfer or acquire denitrification clusters by horizontal gene transfer is discussed.

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Day, Jane S. "Prehistoric Settlement Patterns in Costa Rica. Frederick W. Lange and Lynette Norr, editors. Journal of the Steward Anthropological Society, Urbana–Champaign, 1986. viii + 440 pp., figures, references cited. $22.00 (paper)." American Antiquity 54, no. 1 (January 1989): 220. http://dx.doi.org/10.2307/281366.

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Lee, C. M. H., F. R. Tekpetey, D. T. Armstrong, and M. W. Khalil. "Conversion of 5(10)-oestrene-3β,17β-diol to 19-nor-4-ene-3-ketosteroids by luteal cells in vitro: possible involvement of the 3β-hydroxysteroid dehydrogenase/isomerase." Journal of Endocrinology 129, no. 2 (May 1991): 233–43. http://dx.doi.org/10.1677/joe.0.1290233.

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ABSTRACT We have previously suggested that in porcine granulosa cells, a putative intermediate, 5(10)-oestrene-3,17-dione is involved in 4-oestrene-3,17-dione (19-norandrostenedione; 19-norA) and 4-oestren-17β-ol-3-one (19-nortestosterone: 19-norT) formation from C19 aromatizable androgens. In this study, luteal cells prepared from porcine, bovine and rat corpora lutea by centrifugal elutriation were used as a source of 3β-hydroxysteroid dehydrogenase/isomerase in order to investigate the role of this enzyme in the biosynthesis of 19-norsteroids. Small porcine luteal cells made mainly 19-norT and large porcine luteal cells 19-norA from 5(10)-oestrene-3β,17β-diol, the reduced product of the putative intermediate 5(10)-oestrene-3,17-dione. However, neither small nor large cells metabolized androstenedione to 19-norsteroids. Serum and serum plus LH significantly stimulated formation of both 19-norA and 19-norT from 5(10)-oestrene-3β,17β-diol, compared with controls. Inhibitors of the 3β-hydroxysteroid dehydrogenase/isomerase (trilostane and cyanoketone) significantly reduced formation of 19-norT in small porcine luteal cells and 19-norA in large porcine luteal cells, although they were effective at different concentrations in each cell type. In parallel incubations, formation of [4-14C]androstenedione from added [4-14C]dehydroepiandrosterone was also inhibited by cyanoketone in both small and large porcine luteal cells in a dose-dependent manner; however, trilostane (up to 100 μmol/l) did not inhibit androstenedione formation in large porcine luteal cells. In addition, the decrease in progesterone synthesis induced by trilostane and cyanoketone (100 μmol/l each) was accompanied by a parallel accumulation of pregnenolone in both cell types. These results suggest that 3β-hydroxysteroid dehydrogenase/isomerase, or a closely related enzyme, present in small and large porcine luteal cells can convert added 5(10)-3β-hydroxysteroids into 19-nor-4(5)-3-kestosteroids in vitro. In the porcine ovarian follicle, therefore, formation of 19-norA from androstenedione can be envisaged as a two-step enzymatic process: 19-demethylation of androstenedione to produce the putative intermediate 5(10)-oestrene-3,17-dione, and subsequent isomerization to 19-norA. In contrast to granulosa cells, porcine luteal cells synthesized 19-norA or 19-norT only when provided with the appropriate substrate. Unfractionated rat luteal cells also metabolized 5(10)-oestrene-3β,17β-diol to a mixture of 19-norA and 19-norT; conversion was inhibited by trilostane. In addition, small bovine luteal cells synthesized mainly 19-norT and formation was also inhibited by trilostane and cyanoketone. In addition to 19-norA, an unknown metabolite, formed in low amounts by large porcine luteal cells, appears to be related to another steroid which accumulated at high inhibitor concentrations; it may represent 5(10)-oestrene-3,17-dione postulated as a putative intermediate formed during 19-norsteroid biosynthesis. Journal of Endocrinology (1991) 129, 233–243

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44

Heitz-Tokpa, Kathrin, and Prisca Doua Mori. "« Jeudi noir » à Ouangolodougou, extrême nord ivoirien, 4 mai 2017." Afrique contemporaine 263-264, no. 3 (2017): 265. http://dx.doi.org/10.3917/afco.263.0265.

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45

Truong-Bolduc, Q. C., P. M. Dunman, J. Strahilevitz, S. J. Projan, and D. C. Hooper. "MgrA Is a Multiple Regulator of Two New Efflux Pumps in Staphylococcus aureus." Journal of Bacteriology 187, no. 7 (April 1, 2005): 2395–405. http://dx.doi.org/10.1128/jb.187.7.2395-2405.2005.

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ABSTRACT In an analysis of the resistance mechanisms of an mgrA mutant, we identified two genes encoding previously undescribed transporters, NorB and Tet38. norB was 1,392 bp and encoded a predicted 49-kDa protein. When overexpressed, NorB led to an increase in resistance to hydrophilic quinolones, ethidium bromide, and cetrimide and also to sparfloxacin, moxifloxacin, and tetracycline, a resistance phenotype of the mgrA mutant. NorA and NorB shared 30% similarity, and NorB shared 30 and 41% similarities with the Bmr and Blt transporters of Bacillus subtilis, respectively. The second efflux pump was a more selective transporter that we have called Tet38, which had 46% similarity with the plasmid-encoded TetK efflux transporter of S. aureus. tet38 was 1,353 bp and encoded a predicted 49-kDa protein. Overexpression of tet38 produced resistance to tetracycline but not to minocycline and other drugs. norB and tet38 transcription was negatively regulated by MgrA. Limited binding of MgrA to the promoter regions of norB and tet38 was demonstrated by gel shift assays, suggesting that MgrA was an indirect regulator of norB and tet38 expression. The mgrA norB double mutant was reproducibly twofold more susceptible to the tested quinolones than the mgrA mutant. The mgrA tet38 double mutant became more susceptible to tetracycline than the wild-type parent strain. These data demonstrate that overexpression of NorB and Tet38 contribute, respectively, to the hydrophobic quinolone resistance and the tetracycline resistance of the mgrA mutant and that MgrA regulates expression of norB and tet38 in addition to its role in regulation of norA expression.

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46

Allison, Scott T. "Promoting Systematic Information Processing in the Classroom." Teaching of Psychology 19, no. 4 (December 1992): 234–36. http://dx.doi.org/10.1207/s15328023top1904_11.

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This article describes a strategy for sustaining students' attention and systematic information processing. The instructor imbeds an absurdity, called a norm of ridiculosity quotient (NORQ), into the daily presentation for students to detect. The logistics and implications of implementing the NORQ exercise in an advanced seminar class of 18 students are discussed. Pedagogical benefits of the strategy are also considered.

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47

Song, Q. W., and G. L. Huang. "A tentative statistical analysis of flare events observed by NoRH and NoRP." Advances in Space Research 41, no. 8 (January 2008): 1188–90. http://dx.doi.org/10.1016/j.asr.2007.08.035.

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48

Reguero Ugarte, Urtzi. "NOR-NORI-NORK saileko perifrasietako aditz laguntzaileak goi-nafarreraz: azterketa eta proposamen berria / Ditransitive auxiliary verbs in indicative and non-indicative periphrasis in high-Navarrese dialect: an analysis and a new proposal." Anuario del Seminario de Filología Vasca "Julio de Urquijo" 52, no. 1/2 (January 8, 2019): 683. http://dx.doi.org/10.1387/asju.20224.

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Saio honek goi-nafarrerazko NOR-NORI-NORK saileko perifrasietako aditz laguntzaileez dihardu, eta horretarako 1750. urtea baino lehenagoko goi-nafarrerazko lekukotasunetan sistematikoki begiratu dira sail horretako aditz laguntzaileak. Hori dela eta, *eradun, *nin eta *erazan laguntzaileen agerraldiak aztertu eta beren kronologiaz eta hedaduraz proposamen berria egiten da.

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D'EPENOUX, Françoise. "Relations milieu-production. application au pin noir d'autriche sur le versant nord du ventoux." Revue Forestière Française, no. 3 (1994): 223. http://dx.doi.org/10.4267/2042/26536.

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Braker, Gesche, and James M. Tiedje. "Nitric Oxide Reductase (norB) Genes from Pure Cultures and Environmental Samples." Applied and Environmental Microbiology 69, no. 6 (June 2003): 3476–83. http://dx.doi.org/10.1128/aem.69.6.3476-3483.2003.

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ABSTRACT A PCR-based approach was developed to recover nitric oxide (NO) reductase (norB) genes as a functional marker gene for denitrifying bacteria. norB database sequences grouped in two very distinct branches. One encodes the quinol-oxidizing single-subunit class (qNorB), while the other class is a cytochrome bc-type complex (cNorB). The latter oxidizes cytochrome c, and the gene is localized adjacent to norC. While both norB types occur in denitrifying strains, the qnorB type was also found in a variety of nondenitrifying strains, suggesting a function in detoxifying NO. Branch-specific degenerate primer sets detected the two norB types in our denitrifier cultures. Specificity was confirmed by sequence analysis of the norB amplicons and failure to amplify norB from nondenitrifying strains. These primer sets also specifically amplified norB from freshwater and marine sediments. Pairwise comparison of amplified norB sequences indicated minimum levels of amino acid identity of 43.9% for qnorB and 38% for cnorB. Phylogenetic analysis confirmed the existence of two classes of norB genes, which clustered according to the respective primer set. Within the qnorB cluster, the majority of genes from isolates and a few environmental clones formed a separate subcluster. Most environmental qnorB clones originating from both habitats clustered into two distinct subclusters of novel sequences from presumably as yet uncultivated organisms. cnorB clones were located on separate branches within subclusters of genes from known organisms, suggesting an origin from similar organisms.

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Journal articles on the topic 'Norr'

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