1
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Iskhakova ZI, Zhuravleva DE, Heim C, Hartmann MD, Laykov AV, Forchhammer K, Kayumov AR. PotN represents a novel energy‐state sensing PII subfamily, occurring in firmicutes. FEBS J 2022; 289:5305-5321. [DOI: 10.1111/febs.16431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 02/19/2022] [Accepted: 03/10/2022] [Indexed: 01/19/2023]
Affiliation(s)
| | | | - Christopher Heim
- Department of Protein Evolution Max Planck Institute for Developmental Biology Tübingen Germany
| | - Marcus D. Hartmann
- Department of Protein Evolution Max Planck Institute for Developmental Biology Tübingen Germany
| | | | - Karl Forchhammer
- Institut für Mikrobiologie Eberhard‐Karls‐Universität Tübingen Germany
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2
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Role of GlnR in Controlling Expression of Nitrogen Metabolism Genes in Listeria monocytogenes. J Bacteriol 2020; 202:JB.00209-20. [PMID: 32690554 DOI: 10.1128/jb.00209-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/10/2020] [Indexed: 01/27/2023] Open
Abstract
Listeria monocytogenes is a fastidious bacterial pathogen that can utilize only a limited number of nitrogen sources for growth. Both glutamine and ammonium are common nitrogen sources used in listerial defined growth media, but little is known about the regulation of their uptake or utilization. The functional role of L. monocytogenes GlnR, the transcriptional regulator of nitrogen metabolism genes in low-G+C Gram-positive bacteria, was determined using transcriptome sequencing and real-time reverse transcription-PCR experiments. The GlnR regulon included transcriptional units involved in ammonium transport (amtB glnK) and biosynthesis of glutamine (glnRA) and glutamate (gdhA) from ammonium. As in other bacteria, GlnR proved to be an autoregulatory repressor of the glnRA operon. Unexpectedly, GlnR was most active during growth with ammonium as the nitrogen source and less active in the glutamine medium, apparently because listerial cells perceive growth with glutamine as a nitrogen-limiting condition. Therefore, paradoxically, expression of the glnA gene, encoding glutamine synthetase, was highest in the glutamine medium. For the amtB glnK operon, GlnR served as both a negative regulator in the presence of ammonium and a positive regulator in the glutamine medium. The gdhA gene was subject to a third mode of regulation that apparently required an elevated level of GlnR for repression. Finally, activity of glutamate dehydrogenase encoded by the gdhA gene appeared to correlate inversely with expression of gltAB, the operon that encodes the other major glutamate-synthesizing enzyme, glutamate synthase. Both gdhA and amtB were also regulated, in a negative manner, by the global transcriptional regulator CodY.IMPORTANCE L. monocytogenes is a widespread foodborne pathogen. Nitrogen-containing compounds, such as the glutamate-containing tripeptide, glutathione, and glutamine, have been shown to be important for expression of L. monocytogenes virulence genes. In this work, we showed that a transcriptional regulator, GlnR, controls expression of critical listerial genes of nitrogen metabolism that are involved in ammonium uptake and biosynthesis of glutamine and glutamate. A different mode of GlnR-mediated regulation was found for each of these three pathways.
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Wang C, Wang J, Yuan J, Jiang L, Jiang X, Yang B, Zhao G, Liu B, Huang D. Generation of
Streptomyces hygroscopicus
cell factories with enhanced ascomycin production by combined elicitation and pathway‐engineering strategies. Biotechnol Bioeng 2019; 116:3382-3395. [DOI: 10.1002/bit.27158] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/26/2019] [Accepted: 08/28/2019] [Indexed: 01/09/2023]
Affiliation(s)
- Cheng Wang
- Department of Forestry Engineering, College of ForestryNorthwest A&F UniversityYangling Shaanxi China
| | - Junhua Wang
- Tianjin Institute of Industrial BiotechnologyChinese Academy of SciencesTianjin China
| | - Jian Yuan
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
| | - Lingyan Jiang
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
| | - Xiaolong Jiang
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
| | - Bin Yang
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
| | - Guang Zhao
- Qingdao Institute of Bioenergy and Bioprocess TechnologyChinese Academy of SciencesQingdao Shandong China
| | - Bin Liu
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
- Tianjin Key Laboratory of Microbial Functional GenomicsNankai UniversityTianjin China
| | - Di Huang
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin China
- TEDA Institute of Biological Sciences and BiotechnologyNankai UniversityTianjin China
- SynBio Research Platform, Collaborative Innovation Center of Chemical Science and EngineeringNankai UniversityTianjin China
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4
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Wang T, Zhao X, Shi H, Sun L, Li Y, Li Q, Zhang H, Chen S, Li J. Positive and negative regulation of transferred nif genes mediated by indigenous GlnR in Gram-positive Paenibacillus polymyxa. PLoS Genet 2018; 14:e1007629. [PMID: 30265664 PMCID: PMC6191146 DOI: 10.1371/journal.pgen.1007629] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 10/16/2018] [Accepted: 08/14/2018] [Indexed: 12/29/2022] Open
Abstract
Ammonia is a major signal that regulates nitrogen fixation in most diazotrophs. Regulation of nitrogen fixation by ammonia in the Gram-negative diazotrophs is well-characterized. In these bacteria, this regulation occurs mainly at the level of nif (nitrogen fixation) gene transcription, which requires a nif-specific activator, NifA. Although Gram-positive and diazotrophic Paenibacilli have been extensively used as a bacterial fertilizer in agriculture, how nitrogen fixation is regulated in response to nitrogen availability in these bacteria remains unclear. An indigenous GlnR and GlnR/TnrA-binding sites in the promoter region of the nif cluster are conserved in these strains, indicating the role of GlnR as a regulator of nitrogen fixation. In this study, we for the first time reveal that GlnR of Paenibacillus polymyxa WLY78 is essentially required for nif gene transcription under nitrogen limitation, whereas both GlnR and glutamine synthetase (GS) encoded by glnA within glnRA operon are required for repressing nif expression under excess nitrogen. Dimerization of GlnR is necessary for binding of GlnR to DNA. GlnR in P. polymyxa WLY78 exists in a mixture of dimers and monomers. The C-terminal region of GlnR monomer is an autoinhibitory domain that prevents GlnR from binding DNA. Two GlnR-biding sites flank the -35/-10 regions of the nif promoter of the nif operon (nifBHDKENXhesAnifV). The GlnR-binding site Ⅰ (located upstream of -35/-10 regions of the nif promoter) is specially required for activating nif transcription, while GlnR-binding siteⅡ (located downstream of -35/-10 regions of the nif promoter) is for repressing nif expression. Under nitrogen limitation, GlnR dimer binds to GlnR-binding siteⅠ in a weak and transient association way and then activates nif transcription. During excess nitrogen, glutamine binds to and feedback inhibits GS by forming the complex FBI-GS. The FBI-GS interacts with the C-terminal domain of GlnR and stabilizes the binding affinity of GlnR to GlnR-binding site Ⅱ and thus represses nif transcription. GlnR is a global transcription regulator of nitrogen metabolism in Bacillus and other Gram-positive bacteria. GlnR generally functions as repressor and inhibits gene transcription under excess nitrogen. Our study for the first time reveals that GlnR simultaneously acted as an activator and a repressor for nitrogen fixation of Paenibacillus by binding to different loci of the single nif promoter region according to nitrogen availability. In excess glutamine, the feedback inhibited form of glutamine synthetase (GS) encoded by glnA within glnRA operon directly interacts with the C-terminal domain of GlnR and then controls the GlnR activity. Also, overexpression of glnR or deletion of glnA or mutagenesis of GlnR-binding site Ⅱ led to constitutive nif expression in the absence or presence of high (100 mM) concentration of ammonia. This work represents the first instance of a dual positive and negative regulatory mechanism of nitrogen fixation.
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Affiliation(s)
- Tianshu Wang
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Xiyun Zhao
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Haowen Shi
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Li Sun
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Yongbin Li
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Qin Li
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Haowei Zhang
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
| | - Sanfeng Chen
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
- * E-mail:
| | - Jilun Li
- State Key Laboratory for Agrobiotechnology, Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, P. R. China
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5
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Gerhardt ECM, Moure VR, Souza AW, Pedrosa FO, Souza EM, Diacovich L, Gramajo H, Huergo LF. Expression and purification of untagged GlnK proteins from actinobacteria. EXCLI JOURNAL 2017; 16:949-958. [PMID: 28900375 PMCID: PMC5579400 DOI: 10.17179/excli2017-394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 06/12/2017] [Indexed: 11/16/2022]
Abstract
The PII protein family constitutes one of the most conserved and well distributed family of signal transduction proteins in nature. These proteins play key roles in nitrogen and carbon metabolism. PII function has been well documented in Gram-negative bacteria. However, there are very few reports describing the in vitro properties and function of PII derived from Gram-positive bacteria. Here we present the heterologous expression and efficient purification protocols for untagged PII from three Actinobacteria of medical and biotechnological interest namely: Mycobacterium tuberculosis, Rhodococcus jostii and Streptomyces coelicolor. Circular dichroism and gel filtration analysis supported that the purified proteins are correctly folded. The purification protocol described here will facilitate biochemical studies and help to uncover the biochemical functions of PII proteins in Actinobacteria.
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Affiliation(s)
| | - Vivian R Moure
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, Brazil
| | - Andrey W Souza
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, Brazil
| | - Fabio O Pedrosa
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, Brazil
| | - Emanuel M Souza
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, Brazil
| | - Lautaro Diacovich
- Instituto de Biologia Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Hugo Gramajo
- Instituto de Biologia Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Luciano F Huergo
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, Brazil.,Setor Litoral, UFPR, Matinhos, Brazil
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6
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Fernandes GDC, Hauf K, Sant'Anna FH, Forchhammer K, Passaglia LMP. Glutamine synthetase stabilizes the binding of GlnR to nitrogen fixation gene operators. FEBS J 2017; 284:903-918. [DOI: 10.1111/febs.14021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 12/22/2016] [Accepted: 01/18/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Gabriela de C. Fernandes
- Departamento de Genética Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre RS Brazil
- Interfaculty Institute for Microbiology and Infection Medicine University of Tuebingen Germany
| | - Ksenia Hauf
- Interfaculty Institute for Microbiology and Infection Medicine University of Tuebingen Germany
| | - Fernando H. Sant'Anna
- Departamento de Genética Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre RS Brazil
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine University of Tuebingen Germany
| | - Luciane M. P. Passaglia
- Departamento de Genética Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre RS Brazil
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7
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Chen YYM, Chen YY, Hung JL, Chen PM, Chia JS. The GlnR Regulon in Streptococcus mutans Is Differentially Regulated by GlnR and PmrA. PLoS One 2016; 11:e0159599. [PMID: 27454482 PMCID: PMC4959772 DOI: 10.1371/journal.pone.0159599] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 05/30/2016] [Indexed: 12/13/2022] Open
Abstract
GlnR-mediated repression of the GlnR regulon at acidic pH is required for optimal acid tolerance in Streptococcus mutans, the etiologic agent for dental caries. Unlike most streptococci, the GlnR regulon is also regulated by newly identified PmrA (SMUGS5_RS05810) at the transcriptional level in S. mutans GS5. Results from gel mobility shift assays confirmed that both GlnR and PmrA recognized the putative GlnR box in the promoter regions of the GlnR regulon genes. By using a chemostat culture system, we found that PmrA activated the expression of the GlnR regulon at pH 7, and that this activation was enhanced by excess glucose. Deletion of pmrA (strain ΔPmrA) reduced the survival rate of S. mutans GS5 at pH 3 moderately, whereas the GlnR mutant (strain ΔGlnR) exhibited an acid-sensitive phenotype in the acid killing experiments. Elevated biofilm formation in both ΔGlnR and ΔPmrA mutant strains is likely a result of indirect regulation of the GlnR regulon since GlnR and PmrA regulate the regulon differently. Taken together, it is suggested that activation of the GlnR regulon by PmrA at pH 7 ensures adequate biosynthesis of amino acid precursor, whereas repression by GlnR at acidic pH allows greater ATP generation for acid tolerance. The tight regulation of the GlnR regulon in response to pH provides an advantage for S. mutans to better survive in its primary niche, the oral cavity.
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Affiliation(s)
- Yi-Ywan M. Chen
- Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
- * E-mail:
| | - Yueh-Ying Chen
- Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Jui-Lung Hung
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Pei-Min Chen
- Department and Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Jean-San Chia
- Department and Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
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8
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Kaspar D, Auer F, Schardt J, Schindele F, Ospina A, Held C, Ehrenreich A, Scherer S, Müller-Herbst S. Temperature- and nitrogen source-dependent regulation of GlnR target genes in Listeria monocytogenes. FEMS Microbiol Lett 2014; 355:131-41. [PMID: 24801548 DOI: 10.1111/1574-6968.12458] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 04/30/2014] [Indexed: 11/28/2022] Open
Abstract
The ubiquitous pathogen Listeria monocytogenes lives either saprophytically in the environment or within cells in a vertebrate host, thus adapting its lifestyle to its ecological niche. Growth experiments at 24 and 37 °C (environmental and host temperature) with ammonium or glutamine as nitrogen sources revealed that ammonium is the preferred nitrogen source of L. monocytogenes. Reduced growth on glutamine is more obvious at 24 °C. Global transcriptional microarray analyses showed that the most striking difference in temperature-dependent transcription was observed for central nitrogen metabolism genes, glnR (glutamine synthetase repressor GlnR), glnA (glutamine synthetase GlnA), amtB (ammonium transporter AmtB), glnK (PII regulatory protein GlnK), and gdh (glutamate dehydrogenase) when cells were grown on glutamine. When grown on ammonium, both at 24 and 37 °C, the transcriptional level of these genes resembles that of cells grown with glutamine at 37 °C. Electrophoretic mobility shift assay studies and qPCR analyses in the wild-type L. monocytogenes and the deletion mutant L. monocytogenes ∆glnR revealed that the transcriptional regulator GlnR is directly involved in temperature- and nitrogen source-dependent regulation of the respective genes. Glutamine, a metabolite known to influence GlnR activity, seems unlikely to be the (sole) intracellular signal mediating this temperature-and nitrogen source-dependent metabolic adaptation.
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Affiliation(s)
- Daniela Kaspar
- Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Wissenschaftszentrum Weihenstephan, Freising, Germany; Abteilung Mikrobiologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Technische Universität München, Freising, Germany
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9
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Abstract
To modulate the expression of genes involved in nitrogen assimilation, the cyanobacterial PII-interacting protein X (PipX) interacts with the global transcriptional regulator NtcA and the signal transduction protein PII, a protein found in all three domains of life as an integrator of signals of the nitrogen and carbon balance. PipX can form alternate complexes with NtcA and PII, and these interactions are stimulated and inhibited, respectively, by 2-oxoglutarate, providing a mechanistic link between PII signaling and NtcA-regulated gene expression. Here, we demonstrate that PipX is involved in a much wider interaction network. The effect of pipX alleles on transcript levels was studied by RNA sequencing of S. elongatus strains grown in the presence of either nitrate or ammonium, followed by multivariate analyses of relevant mutant/control comparisons. As a result of this process, 222 genes were classified into six coherent groups of differentially regulated genes, two of which, containing either NtcA-activated or NtcA-repressed genes, provided further insights into the function of NtcA-PipX complexes. The remaining four groups suggest the involvement of PipX in at least three NtcA-independent regulatory pathways. Our results pave the way to uncover new regulatory interactions and mechanisms in the control of gene expression in cyanobacteria.
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10
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Rodrigues TE, Gerhardt ECM, Oliveira MA, Chubatsu LS, Pedrosa FO, Souza EM, Souza GA, Müller-Santos M, Huergo LF. Search for novel targets of the PII signal transduction protein in Bacteria identifies the BCCP component of acetyl-CoA carboxylase as a PII binding partner. Mol Microbiol 2014; 91:751-61. [PMID: 24329683 DOI: 10.1111/mmi.12493] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2013] [Indexed: 11/29/2022]
Abstract
The PII family comprises a group of widely distributed signal transduction proteins. The archetypal function of PII is to regulate nitrogen metabolism in bacteria. As PII can sense a range of metabolic signals, it has been suggested that the number of metabolic pathways regulated by PII may be much greater than described in the literature. In order to provide experimental evidence for this hypothesis a PII protein affinity column was used to identify PII targets in Azospirillum brasilense. One of the PII partners identified was the biotin carboxyl carrier protein (BCCP), a component of the acetyl-CoA carboxylase which catalyses the committed step in fatty acid biosynthesis. As BCCP had been previously identified as a PII target in Arabidopsis thaliana we hypothesized that the PII -BCCP interaction would be conserved throughout Bacteria. In vitro experiments using purified proteins confirmed that the PII -BCCP interaction is conserved in Escherichia coli. The BCCP-PII interaction required MgATP and was dissociated by increasing 2-oxoglutarate. The interaction was modestly affected by the post-translational uridylylation status of PII ; however, it was completely dependent on the post-translational biotinylation of BCCP.
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Affiliation(s)
- Thiago E Rodrigues
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil
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11
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Huergo LF, Chandra G, Merrick M. PIIsignal transduction proteins: nitrogen regulation and beyond. FEMS Microbiol Rev 2013; 37:251-83. [DOI: 10.1111/j.1574-6976.2012.00351.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 07/26/2012] [Accepted: 07/26/2012] [Indexed: 01/12/2023] Open
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12
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Groot Kormelink T, Koenders E, Hagemeijer Y, Overmars L, Siezen RJ, de Vos WM, Francke C. Comparative genome analysis of central nitrogen metabolism and its control by GlnR in the class Bacilli. BMC Genomics 2012; 13:191. [PMID: 22607086 PMCID: PMC3412718 DOI: 10.1186/1471-2164-13-191] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 03/20/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The assimilation of nitrogen in bacteria is achieved through only a few metabolic conversions between alpha-ketoglutarate, glutamate and glutamine. The enzymes that catalyze these conversions are glutamine synthetase, glutaminase, glutamate dehydrogenase and glutamine alpha-ketoglutarate aminotransferase. In low-GC Gram-positive bacteria the transcriptional control over the levels of the related enzymes is mediated by four regulators: GlnR, TnrA, GltC and CodY. We have analyzed the genomes of all species belonging to the taxonomic families Bacillaceae, Listeriaceae, Staphylococcaceae, Lactobacillaceae, Leuconostocaceae and Streptococcaceae to determine the diversity in central nitrogen metabolism and reconstructed the regulation by GlnR. RESULTS Although we observed a substantial difference in the extent of central nitrogen metabolism in the various species, the basic GlnR regulon was remarkably constant and appeared not affected by the presence or absence of the other three main regulators. We found a conserved regulatory association of GlnR with glutamine synthetase (glnRA operon), and the transport of ammonium (amtB-glnK) and glutamine/glutamate (i.e. via glnQHMP, glnPHQ, gltT, alsT). In addition less-conserved associations were found with, for instance, glutamate dehydrogenase in Streptococcaceae, purine catabolism and the reduction of nitrite in Bacillaceae, and aspartate/asparagine deamination in Lactobacillaceae. CONCLUSIONS Our analyses imply GlnR-mediated regulation in constraining the import of ammonia/amino-containing compounds and the production of intracellular ammonia under conditions of high nitrogen availability. Such a role fits with the intrinsic need for tight control of ammonia levels to limit futile cycling.
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Affiliation(s)
- Tom Groot Kormelink
- Kluyver Centre for Genomics of Industrial Fermentation, Delft, The Netherlands
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