glnF-lacZ fusions in Escherichia coli: studies on glnF expression and its chromosomal orientation

Castaño, Irene Mencía; Bastarrachea, Fernando

doi:10.1007/bf00332751

Cited by 44 publications

(21 citation statements)

References 22 publications

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“…Given such a range of functions, it is also not surprising that the expression of rpoN appears to be constitutive in A. tumefaciens strain 5A and is not influenced by a specific solute or ion such as As III (Fig. 3), which is in agreement with previous studies (7,26). What was surprising, however, was the observation of a C 4 -dicarboxylate transporter (dctA) (Fig.…”

Section: Discussionsupporting

confidence: 89%

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Kang

Bothner

Rensing

et al. 2012

Appl Environ Microbiol

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In this study with the model organism Agrobacterium tumefaciens, we used a combination of lacZ gene fusions, reverse transcriptase PCR (RT-PCR), and deletion and insertional inactivation mutations to show unambiguously that the alternative sigma factor RpoN participates in the regulation of As III oxidation. A deletion mutation that removed the RpoN binding site from the aioBA promoter and an aacC3 (gentamicin resistance) cassette insertional inactivation of the rpoN coding region eliminated aioBA expression and As III oxidation, although rpoN expression was not related to cell exposure to As III . Putative RpoN binding sites were identified throughout the genome and, as examples, included promoters for aioB, phoB1, pstS1, dctA, glnA, glnB, and flgB that were examined by using qualitative RT-PCR and lacZ reporter fusions to assess the relative contribution of RpoN to their transcription. The expressions of aioB and dctA in the wild-type strain were considerably enhanced in cells exposed to As III , and both genes were silent in the rpoN::aacC3 mutant regardless of As III . The expression level of glnA was not influenced by As III but was reduced (but not silent) in the rpoN::aacC3 mutant and further reduced in the mutant under N starvation conditions. The rpoN::aacC3 mutation had no obvious effect on the expression of glnB, pstS1, phoB1, or flgB. These experiments provide definitive evidence to document the requirement of RpoN for As III oxidation but also illustrate that the presence of a consensus RpoN binding site does not necessarily link the associated gene with regulation by As III or by this sigma factor. E vidence of microbial arsenite (As III ) oxidation was first reported nearly a century ago (18). Subsequent progress has been sporadic, with work that identified some organisms capable of As III oxidation (46,48,60) and then a study of a Pseudomonas arsenitoxidans strain reported to grow chemolithoautotrophically with As III as a sole electron donor (23). Subsequent follow-up characterizations of this organism and this process failed to materialize; however, approximately 2 decades later, Santini et al. (52) described the isolation and initial characterization of a Rhizobiumlike bacterium (strain NT-26) that could grow chemolithoautotrophically with As III as a sole electron donor for energy generation and with CO 2 as a sole carbon source. Soon thereafter, and in part stimulated by the massive arsenic poisoning disaster in Bangladesh (2), a series of studies initiated the characterization of microbial As III oxidation in natural environments, including geothermal springs (9,11,12,17,19,24,25,35,51) and soils (41); in mining-contaminated environments (6, 13, 40); and, most recently, in anoxic photosynthesis (21, 33). Likewise, progress has been made in the understanding of the biochemistry of the As III oxidase enzyme (1,14,37 oxidase structural genes were later cloned from the above-mentioned Rhizobium NT-26 organism (53). The symbols for genes coding for functions associated with As III oxidation have...

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Section: Discussionsupporting

confidence: 89%

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Kang

Bothner

Rensing

et al. 2012

Appl Environ Microbiol

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“…The genes in the rpoN operon are expressed from two promoters, i.e., a strong promoter upstream of rpoN (257,260) and a weak promoter upstream of the ptsNO genes (257). Transcription of the rpoN gene (operon) was found not to be regulated by nitrogen (257,261,262), which, in hindsight, is not so remarkable anymore in light of the involvement of the sigma factor in all kinds of bacterium-environment interactions (256). A third gene that coded for a protein with homology to a PTS component was ptsP.…”

Section: Nitrogen-phosphotransferase Systemmentioning

confidence: 99%

Nitrogen Assimilation in Escherichia coli: Putting Molecular Data into a Systems Perspective

Heeswijk¹,

Westerhoff

Boogerd³

2013

Microbiol Mol Biol Rev

232

246

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SUMMARY We present a comprehensive overview of the hierarchical network of intracellular processes revolving around central nitrogen metabolism in Escherichia coli . The hierarchy intertwines transport, metabolism, signaling leading to posttranslational modification, and transcription. The protein components of the network include an ammonium transporter (AmtB), a glutamine transporter (GlnHPQ), two ammonium assimilation pathways (glutamine synthetase [GS]-glutamate synthase [glutamine 2-oxoglutarate amidotransferase {GOGAT}] and glutamate dehydrogenase [GDH]), the two bifunctional enzymes adenylyl transferase/adenylyl-removing enzyme (ATase) and uridylyl transferase/uridylyl-removing enzyme (UTase), the two trimeric signal transduction proteins (GlnB and GlnK), the two-component regulatory system composed of the histidine protein kinase nitrogen regulator II (NRII) and the response nitrogen regulator I (NRI), three global transcriptional regulators called nitrogen assimilation control (Nac) protein, leucine-responsive regulatory protein (Lrp), and cyclic AMP (cAMP) receptor protein (Crp), the glutaminases, and the nitrogen-phosphotransferase system. First, the structural and molecular knowledge on these proteins is reviewed. Thereafter, the activities of the components as they engage together in transport, metabolism, signal transduction, and transcription and their regulation are discussed. Next, old and new molecular data and physiological data are put into a common perspective on integral cellular functioning, especially with the aim of resolving counterintuitive or paradoxical processes featured in nitrogen assimilation. Finally, we articulate what still remains to be discovered and what general lessons can be learned from the vast amounts of data that are available now.

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“…Variations in 54 activity, either by ligand binding or by covalent modification, are not known in E. coli. Furthermore, the intracellular level of 54 is apparently constant (87), and expression of rpoN, which specifies 54 , appears to be constitutive (33). Strain W3110 contains about 700 molecules of 70 per cell and 110 molecules of 54 , whereas strain MC4100 may contain only about 285 molecules of 70 and as few as 13 to 22 molecules of 54 (87).…”

Section: Control Of 54 -Dependent Promotersmentioning

confidence: 99%

Metabolic Context and Possible Physiological Themes of ς⁵⁴-Dependent Genes inEscherichia coli

Reitzer

Schneider

2001

Microbiol Mol Biol Rev

253

300

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SUMMARY ς54 has several features that distinguish it from other sigma factors in Escherichia coli: it is not homologous to other ς subunits, ς54-dependent expression absolutely requires an activator, and the activator binding sites can be far from the transcription start site. A rationale for these properties has not been readily apparent, in part because of an inability to assign a common physiological function for ς54-dependent genes. Surveys of ς54-dependent genes from a variety of organisms suggest that the products of these genes are often involved in nitrogen assimilation; however, many are not. Such broad surveys inevitably remove the ς54-dependent genes from a potentially coherent metabolic context. To address this concern, we consider the function and metabolic context of ς54-dependent genes primarily from a single organism, Escherichia coli, in which a reasonably complete list of ς54-dependent genes has been identified by computer analysis combined with a DNA microarray analysis of nitrogen limitation-induced genes. E. coli appears to have approximately 30 ς54-dependent operons, and about half are involved in nitrogen assimilation and metabolism. A possible physiological relationship between ς54-dependent genes may be based on the fact that nitrogen assimilation consumes energy and intermediates of central metabolism. The products of the ς54-dependent genes that are not involved in nitrogen metabolism may prevent depletion of metabolites and energy resources in certain environments or partially neutralize adverse conditions. Such a relationship may limit the number of physiological themes of ς54-dependent genes within a single organism and may partially account for the unique features of ς54 and ς54-dependent gene expression.

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glnF-lacZ fusions in Escherichia coli: studies on glnF expression and its chromosomal orientation

Cited by 44 publications

References 22 publications

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Nitrogen Assimilation in Escherichia coli: Putting Molecular Data into a Systems Perspective

Metabolic Context and Possible Physiological Themes of ς⁵⁴-Dependent Genes inEscherichia coli

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glnF-lacZ fusions in Escherichia coli: studies on glnF expression and its chromosomal orientation

Cited by 44 publications

References 22 publications

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Nitrogen Assimilation in Escherichia coli: Putting Molecular Data into a Systems Perspective

Metabolic Context and Possible Physiological Themes of ς54-Dependent Genes inEscherichia coli

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Metabolic Context and Possible Physiological Themes of ς⁵⁴-Dependent Genes inEscherichia coli