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Zhao X, Song Y, Wang T, Hua C, Hu R, Shang Y, Shi H, Chen S. Glutamine synthetase and GlnR regulate nitrogen metabolism in Paenibacillus polymyxa WLY78. Appl Environ Microbiol 2023; 89:e0013923. [PMID: 37668407 PMCID: PMC10537745 DOI: 10.1128/aem.00139-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 07/12/2023] [Indexed: 09/06/2023] Open
Abstract
Paenibacillus polymyxa WLY78, a N2-fixing bacterium, has great potential use as a biofertilizer in agriculture. Recently, we have revealed that GlnR positively and negatively regulates the transcription of the nif (nitrogen fixation) operon (nifBHDKENXhesAnifV) in P. polymyxa WLY78 by binding to two loci of the nif promoter according to nitrogen availability. However, the regulatory mechanisms of nitrogen metabolism mediated by GlnR in the Paenibacillus genus remain unclear. In this study, we have revealed that glutamine synthetase (GS) and GlnR in P. polymyxa WLY78 play a key role in the regulation of nitrogen metabolism. P. polymyxa GS (encoded by glnA within glnRA) and GS1 (encoded by glnA1) belong to distinct groups: GSI-α and GSI-β. Both GS and GS1 have the enzyme activity to convert NH4+ and glutamate into glutamine, but only GS is involved in the repression by GlnR. GlnR represses transcription of glnRA under excess nitrogen, while it activates the expression of glnA1 under nitrogen limitation. GlnR simultaneously activates and represses the expression of amtBglnK and gcvH in response to nitrogen availability. Also, GlnR regulates the expression of nasA, nasD1D2, nasT, glnQHMP, and glnS. IMPORTANCE In this study, we have revealed that Paenibacillus polymyxa GlnR uses multiple mechanisms to regulate nitrogen metabolism. GlnR activates or represses or simultaneously activates and inhibits the transcription of nitrogen metabolism genes in response to nitrogen availability. The multiple regulation mechanisms employed by P. polymyxa GlnR are very different from Bacillus subtilis GlnR which represses nitrogen metabolism under excess nitrogen. Both GS encoded by glnA within the glnRA operon and GS1 encoded by glnA1 in P. polymyxa WLY78 are involved in ammonium assimilation, but only GS is required for regulating GlnR activity. The work not only provides significant insight into understanding the interplay of GlnR and GS in nitrogen metabolism but also provides guidance for improving nitrogen fixation efficiency by modulating nitrogen metabolism.
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Affiliation(s)
- Xiyun Zhao
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yi Song
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Tianshu Wang
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Chongchong Hua
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Rui Hu
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yimin Shang
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Haowen Shi
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Sanfeng Chen
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
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Gong C, You X, Zhang S, Xue D. Functional Analysis of a Glutamine Biosynthesis Protein from a Psychrotrophic Bacterium, Cryobacterium soli GCJ02. Indian J Microbiol 2020; 60:153-159. [PMID: 32255847 DOI: 10.1007/s12088-020-00858-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 01/30/2020] [Indexed: 11/25/2022] Open
Abstract
A putative glutamine synthetase (GS) was detected in a psychrophilic bacterium, Cryobacterium soli GCJ02. For gaining greater insight into its functioning, the gene was cloned and expressed in a heterologous host, Escherichia coli. The monomer enzyme with a molecular weight of 53.03 kDa was expressed primarily in cytosolic compartment. The enzyme activity was detected using glutamate and ATP. The optimum conditions of its biosynthesis were observed to be 60 °C and pH value 7.5. Its thermostability was relatively high with a half-life of 50 min at 40 °C. GS activity was enhanced in the presence of metal ions such as Mg2+ and Mn2+, whereas Fe2+, Cu2+ and Ca2+ proved inhibitory. The consensus pattern [EXE]-D-KP-[XGXGXH] in the GS lies between residues 132 and 272. The catalytic active sites consisting of EAE and NGSGMH were verified by site-directed mutagenesis. Based on the analysis of the consensus pattern, the GS/glutamate synthase cycle of C. soli GCJ02 is expected to contribute to the GS synthesic activity.
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Affiliation(s)
- Chunjie Gong
- 1Key Laboratory of Fermentation Engineering (Ministry of Education), National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, 430068 People's Republic of China
| | - Xihuo You
- 2Mudanjiang Normal University, Mudanjiang, 157011 People's Republic of China
| | - Shuyang Zhang
- 1Key Laboratory of Fermentation Engineering (Ministry of Education), National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, 430068 People's Republic of China
| | - Dongsheng Xue
- 1Key Laboratory of Fermentation Engineering (Ministry of Education), National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, 430068 People's Republic of China
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3
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Bolay P, Muro-Pastor MI, Florencio FJ, Klähn S. The Distinctive Regulation of Cyanobacterial Glutamine Synthetase. Life (Basel) 2018; 8:E52. [PMID: 30373240 PMCID: PMC6316151 DOI: 10.3390/life8040052] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 10/23/2018] [Accepted: 10/25/2018] [Indexed: 12/02/2022] Open
Abstract
Glutamine synthetase (GS) features prominently in bacterial nitrogen assimilation as it catalyzes the entry of bioavailable nitrogen in form of ammonium into cellular metabolism. The classic example, the comprehensively characterized GS of enterobacteria, is subject to exquisite regulation at multiple levels, among them gene expression regulation to control GS abundance, as well as feedback inhibition and covalent modifications to control enzyme activity. Intriguingly, the GS of the ecologically important clade of cyanobacteria features fundamentally different regulatory systems to those of most prokaryotes. These include the interaction with small proteins, the so-called inactivating factors (IFs) that inhibit GS linearly with their abundance. In addition to this protein interaction-based regulation of GS activity, cyanobacteria use alternative elements to control the synthesis of GS and IFs at the transcriptional level. Moreover, cyanobacteria evolved unique RNA-based regulatory mechanisms such as glutamine riboswitches to tightly tune IF abundance. In this review, we aim to outline the current knowledge on the distinctive features of the cyanobacterial GS encompassing the overall control of its activity, sensing the nitrogen status, transcriptional and post-transcriptional regulation, as well as strain-specific differences.
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Affiliation(s)
- Paul Bolay
- Helmholtz Centre for Environmental Research, Department of Solar Materials, Permoserstrasse 15, D-04318 Leipzig, Germany.
| | - M Isabel Muro-Pastor
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain.
| | - Francisco J Florencio
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain.
| | - Stephan Klähn
- Helmholtz Centre for Environmental Research, Department of Solar Materials, Permoserstrasse 15, D-04318 Leipzig, Germany.
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Valdespino-Castillo PM, Hu P, Merino-Ibarra M, López-Gómez LM, Cerqueda-García D, González-De Zayas R, Pi-Puig T, Lestayo JA, Holman HY, Falcón LI. Exploring Biogeochemistry and Microbial Diversity of Extant Microbialites in Mexico and Cuba. Front Microbiol 2018; 9:510. [PMID: 29666607 PMCID: PMC5891642 DOI: 10.3389/fmicb.2018.00510] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 03/06/2018] [Indexed: 01/23/2023] Open
Abstract
Microbialites are modern analogs of ancient microbial consortia that date as far back as the Archaean Eon. Microbialites have contributed to the geochemical history of our planet through their diverse metabolic capacities that mediate mineral precipitation. These mineral-forming microbial assemblages accumulate major ions, trace elements and biomass from their ambient aquatic environments; their role in the resulting chemical structure of these lithifications needs clarification. We studied the biogeochemistry and microbial structure of microbialites collected from diverse locations in Mexico and in a previously undescribed microbialite in Cuba. We examined their structure, chemistry and mineralogy at different scales using an array of nested methods including 16S rRNA gene high-throughput sequencing, elemental analysis, X-Ray fluorescence (XRF), X-Ray diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transformed Infrared (FTIR) spectroscopy and Synchrotron Radiation-based Fourier Transformed Infrared (SR-FTIR) spectromicroscopy. The resulting data revealed high biological and chemical diversity among microbialites and specific microbe to chemical correlations. Regardless of the sampling site, Proteobacteria had the most significant correlations with biogeochemical parameters such as organic carbon (Corg), nitrogen and Corg:Ca ratio. Biogeochemically relevant bacterial groups (dominant phototrophs and heterotrophs) showed significant correlations with major ion composition, mineral type and transition element content, such as cadmium, cobalt, chromium, copper and nickel. Microbial-chemical relationships were discussed in reference to microbialite formation, microbial metabolic capacities and the role of transition elements as enzyme cofactors. This paper provides an analytical baseline to drive our understanding of the links between microbial diversity with the chemistry of their lithified precipitations.
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Affiliation(s)
- Patricia M Valdespino-Castillo
- Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States
| | - Ping Hu
- Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States
| | - Martín Merino-Ibarra
- Unidad Académica de Ecología y Biodiversidad Acuática, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Luz M López-Gómez
- Unidad Académica de Ecología y Biodiversidad Acuática, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Daniel Cerqueda-García
- Laboratorio de Ecología Bacteriana, Instituto de Ecología, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | | | - Teresa Pi-Puig
- Instituto de Geología, Universidad Nacional Autónoma de México, Mexico City, Mexico.,Laboratorio Nacional de Geoquímica y Mineralogía, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Julio A Lestayo
- Centro de Investigaciones de Ecosistemas Costeros, Cayo Coco, Cuba
| | - Hoi-Ying Holman
- Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA, United States
| | - Luisa I Falcón
- Laboratorio de Ecología Bacteriana, Instituto de Ecología, Universidad Nacional Autónoma de México, Mexico City, Mexico
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Esteves-Ferreira AA, Inaba M, Fort A, Araújo WL, Sulpice R. Nitrogen metabolism in cyanobacteria: metabolic and molecular control, growth consequences and biotechnological applications. Crit Rev Microbiol 2018. [DOI: 10.1080/1040841x.2018.1446902] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Alberto A. Esteves-Ferreira
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
- CAPES Foundation, Ministry of Education of Brazil, Brasilia, Brazil
| | - Masami Inaba
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Antoine Fort
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Wagner L. Araújo
- Max-Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Brazil
| | - Ronan Sulpice
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
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Domínguez-Martín MA, Díez J, García-Fernández JM. Physiological Studies of Glutamine Synthetases I and III from Synechococcus sp. WH7803 Reveal Differential Regulation. Front Microbiol 2016; 7:969. [PMID: 27446010 PMCID: PMC4923085 DOI: 10.3389/fmicb.2016.00969] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 06/03/2016] [Indexed: 11/18/2022] Open
Abstract
The marine picocyanobacterium Synechococcus sp. WH7803 possesses two glutamine synthetases (GSs; EC 6.3.1.2), GSI encoded by glnA and GSIII encoded by glnN. This is the first work addressing the physiological regulation of both enzymes in a marine cyanobacterial strain. The increase of GS activity upon nitrogen starvation was similar to that found in other model cyanobacteria. However, an unusual response was found when cells were grown under darkness: the GS activity was unaffected, reflecting adaptation to the environment where they thrive. On the other hand, we found that GSIII did not respond to nitrogen availability, in sharp contrast with the results observed for this enzyme in other cyanobacteria thus far studied. These features suggest that GS activities in Synechococcus sp. WH7803 represent an intermediate step in the evolution of cyanobacteria, in a process of regulatory streamlining where GSI lost the regulation by light, while GSIII lost its responsiveness to nitrogen. This is in good agreement with the phylogeny of Synechococcus sp. WH7803 in the context of the marine cyanobacterial radiation.
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Affiliation(s)
| | | | - José M. García-Fernández
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CEIA3, Universidad de CórdobaCórdoba, Spain
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7
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Zhu C, Zhang G, Shen C, Chen S, Tang Y, Mei B, Song R. Expression of bacterial glutamine synthetase gene in Arabidopsis thaliana increases the plant biomass and level of nitrogen utilization. Biologia (Bratisl) 2015. [DOI: 10.1515/biolog-2015-0183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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8
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9
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Kim JN, Cann IKO, Mackie RI. Purification, characterization, and expression of multiple glutamine synthetases from Prevotella ruminicola 23. J Bacteriol 2012; 194:176-84. [PMID: 22020637 PMCID: PMC3256599 DOI: 10.1128/jb.05916-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 10/14/2011] [Indexed: 11/20/2022] Open
Abstract
The Prevotella ruminicola 23 genome encodes three different glutamine synthetase (GS) enzymes: glutamine synthetase I (GSI) (ORF02151), GSIII-1 (ORF01459), and GSIII-2 (ORF02034). GSI, GSIII-1, and GSIII-2 have each been heterologously expressed in and purified from Escherichia coli. The subunit molecular mass of GSI was 56 kDa, while GSIII-1 and GSIII-2 were both 83 kDa. Optimal conditions for γ-glutamyl transferase activity were found to be 35°C at pH 5.6 with 0.25 mM Mn(2+) ions (GSI) or 37°C at pH 6.0 (GSIII-1 and GSIII-2) with 0.50 to 1.00 mM Mn(2+) ions. GSIII biosynthetic activity was found to be optimal at 50 to 60°C and pH 6.8 to 7.0 with 10 mM Mn(2+) ions, while GSI displayed no GS biosynthetic activity. Kinetic analysis revealed K(m) values for glutamate and ammonium as well as for hydrolysis of ATP to be 8.58, 0.48, and 1.91 mM, respectively, for GSIII-1 and 1.72, 0.43, and 2.65 mM, respectively, for GSIII-2. A quantitative reverse transcriptase PCR assay (qRT-PCR) revealed GSIII-2 to be significantly induced by high concentrations of ammonia, and this corresponded with increases in measured GS activity. Collectively, these results show that both GSIII enzymes in P. ruminicola 23 are functional and indicate that GSIII-2, flanked by GOGAT (gltB and gltD genes), plays an important role in the acquisition and metabolism of ammonia, particularly under nonlimiting ammonia growth conditions.
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Affiliation(s)
| | - Isaac K. O. Cann
- Department of Animal Sciences
- Department of Microbiology
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
| | - Roderick I. Mackie
- Department of Animal Sciences
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
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10
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He YX, Gui L, Liu YZ, Du Y, Zhou Y, Li P, Zhou CZ. Crystal structure of Saccharomyces cerevisiae glutamine synthetase Gln1 suggests a nanotube-like supramolecular assembly. Proteins 2009; 76:249-54. [PMID: 19322816 DOI: 10.1002/prot.22403] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Yong-Xing He
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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11
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Kinoshita S, Isu S, Kaneko G, Yamada H, Hara T, Itoh Y, Watabe S. The occurrence of eukaryotic type III glutamine synthetase in the marine diatom Chaetoceros compressum. Mar Genomics 2009; 2:103-11. [DOI: 10.1016/j.margen.2009.06.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 05/26/2009] [Accepted: 06/03/2009] [Indexed: 10/20/2022]
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12
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PII, the key regulator of nitrogen metabolism in the cyanobacteria. ACTA ACUST UNITED AC 2008; 51:1056-65. [PMID: 19093078 DOI: 10.1007/s11427-008-0148-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Accepted: 11/15/2008] [Indexed: 10/21/2022]
Abstract
PII proteins are a protein family important to signal transduction in bacteria and plants. PII plays a critical role in regulation of carbon and nitrogen metabolism in cyanobacteria. Through conformation change and covalent modification, which are regulated by 2-oxoglutarate, PII interacts with different target proteins in response to changes of cellular energy status and carbon and nitrogen sources in cyanobacteria and regulates cellular metabolism. This article reports recent progress in PII research in cyanobacteria and discusses the mechanism of PII regulation of cellular metabolism.
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Gómez-García MR, Losada M, Serrano A. Comparative biochemical and functional studies of family I soluble inorganic pyrophosphatases from photosynthetic bacteria. FEBS J 2007; 274:3948-59. [PMID: 17635582 DOI: 10.1111/j.1742-4658.2007.05927.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Soluble inorganic pyrophosphatases (inorganic diphosphatases, EC 3.6.1.1) were isolated and characterized from three phylogenetically diverse cyanobacteria--Synechocystis sp. PCC 6803, Anabaena sp. PCC 7120, and Pseudanabaena sp. PCC 6903--and one anoxygenic photosynthetic bacterium, Rhodopseudomonas viridis (purple nonsulfur). These enzymes were found to be family I soluble inorganic pyrophosphatases with c. 20 kDa subunits with diverse oligomeric structures. The corresponding ppa genes were cloned and functionally validated by heterologous expression. Cyanobacterial family I soluble inorganic pyrophosphatases were strictly Mg(2+)-dependent enzymes. However, diverse cation cofactor dependence was observed for enzymes from other groups of photosynthetic bacteria. Immunochemical studies with antibodies to cyanobacterial soluble inorganic pyrophosphatases showed crossreaction with orthologs of other main groups of phototrophic prokaryotes and suggested a close relationship with the enzyme of heliobacteria, the nearest photosynthetic relatives of cyanobacteria. A slow-growing Escherichia coli JP5 mutant strain, containing a very low level of soluble inorganic pyrophosphatase activity, was functionally complemented up to wild-type growth rates with ppa genes from diverse photosynthetic prokaryotes expressed under their own promoters. Overall, these results suggest that the bacterial family I soluble inorganic pyrophosphatases described here have retained functional similarities despite their genealogies and their adaptations to diverse metabolic scenarios.
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Affiliation(s)
- María R Gómez-García
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla Cartuja, CSIC-Universidad de Sevilla, Spain.
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14
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van Rooyen JM, Abratt VR, Sewell BT. Three-dimensional Structure of a Type III Glutamine Synthetase by Single-particle Reconstruction. J Mol Biol 2006; 361:796-810. [PMID: 16879836 DOI: 10.1016/j.jmb.2006.06.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 06/05/2006] [Accepted: 06/12/2006] [Indexed: 10/24/2022]
Abstract
GlnN, the type III glutamine synthetase (GSIII) from the medically important, anaerobic, opportunistic pathogen Bacteroides fragilis, has 82.8 kDa subunits that share only 9% sequence identity with the type I glutamine synthetases (GSI), the only family for which a structure is known. Active GlnN was found predominantly in a single peak that eluted from a calibrated gel-filtration chromatography column at a position equaivalent to 0.86(+/-0.08) MDa. Negative-stain electron microscopy enabled the identification of double-ringed particles and single hexameric rings ("pinwheels") resulting from partial staining. A 2D average of these pinwheels showed marked similarity to the corresponding structures found in preparations of GSI, except that the arms of the subunits were 40% longer. Reconstructions from particles embedded in vitreous ice showed that GlnN has a double-ringed, dodecameric structure with a 6-fold dihedral space group (D6) symmetry and dimensions of 17.0 nm parallel with the 6-fold axis and 18.3 nm parallel with the 2-fold axes. The structures, combined with a sequence alignment based on structural principles, showed how many aspects of the structure of GSI, and most notably the alpha/beta barrel fold active site were preserved. There was evidence for the presence of this structure in the reconstructed volume, thus, identifying the indentations between the pinwheel spokes as putative active sites and suggesting conservation of the overall molecular geometry found in GSI despite their low level of global homology. Furthermore, docking of GSI into the reconstruction left sufficient plausibly located unoccupied density to account for the additional residues in GSIII, thus validating the structure.
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Affiliation(s)
- Jason M van Rooyen
- Electron Microscope Unit, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
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15
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Aldehni MF, Forchhammer K. Analysis of a non-canonical NtcA-dependent promoter in Synechococcus elongatus and its regulation by NtcA and PII. Arch Microbiol 2005; 184:378-86. [PMID: 16311758 DOI: 10.1007/s00203-005-0056-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 10/04/2005] [Accepted: 11/03/2005] [Indexed: 11/29/2022]
Abstract
In this communication, we present a genetic analysis of the glnN promoter region of Synechococcus elongatus PCC 7942. luxAB reporter fusions were used to characterize the glnN promoter by deletion and site-directed mutational analysis. Reporter gene expression analysis was performed in S. elongatus wild-type and mutant strains to reveal the role of the global nitrogen responsive transcription factor NtcA and of the P(II) signalling protein on regulation of glnN gene expression. A non-canonical NtcA-binding motif is responsible for NtcA-dependent, nitrogen-responsive regulation of glnN. The P(II) signalling protein has opposing effects on NtcA-dependent glnN expression. Under conditions of nitrate-growth, it depresses expression, whereas under conditions of combined nitrogen starvation, it is required for full induction. Furthermore, sequences upstream of the NtcA-binding site have repressive effect on glnN promoter activity.
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Affiliation(s)
- M Fadi Aldehni
- Institut für Mikrobiologie und Molekularbiologie der Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
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16
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Amaya KR, Kocherginskaya SA, Mackie RI, Cann IKO. Biochemical and mutational analysis of glutamine synthetase type III from the rumen anaerobe Ruminococcus albus 8. J Bacteriol 2005; 187:7481-91. [PMID: 16237031 PMCID: PMC1272975 DOI: 10.1128/jb.187.21.7481-7491.2005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2005] [Accepted: 08/08/2005] [Indexed: 11/20/2022] Open
Abstract
Two different genes encoding glutamine synthetase type I (GSI) and GSIII were identified in the genome sequence of R. albus 8. The identity of the GSIII protein was confirmed by the presence of its associated conserved motifs. The glnN gene, encoding the GSIII, was cloned and expressed in Escherichia coli BL21 cells. The recombinant protein was purified and subjected to biochemical and physical analyses. Subunit organization suggested a protein present in solution as both monomers and oligomers. Kinetic studies using the forward and the gamma-glutamyl transferase (gamma-GT) assays were carried out. Mutations that changed conserved glutamic acid residues to alanine in the four GSIII motifs resulted in drastic decreases in GS activity using both assays, except for an E380A mutation, which rather resulted in an increase in activity in the forward assay compared to the wild-type protein. Reduced GSIII activity was also exhibited by mutating, individually, two lysines (K308 and K318) located in the putative nucleotide-binding site to alanine. Most importantly, the presence of mRNA transcripts of the glnN gene in R. albus 8 cells grown under ammonia limiting conditions, whereas little or no transcript was detected in cells grown under ammonia sufficient conditions, suggested an important role for the GSIII in the nitrogen metabolism of R. albus 8. Furthermore, the mutational studies on the conserved GSIII motifs demonstrated, for the first time, their importance in the structure and/or function of a GSIII protein.
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Affiliation(s)
- Kensey R. Amaya
- Department of Animal Sciences, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Svetlana A. Kocherginskaya
- Department of Animal Sciences, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Roderick I. Mackie
- Department of Animal Sciences, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Isaac K. O. Cann
- Department of Animal Sciences, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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Muro-Pastor MI, Reyes JC, Florencio FJ. Ammonium assimilation in cyanobacteria. PHOTOSYNTHESIS RESEARCH 2005; 83:135-50. [PMID: 16143848 DOI: 10.1007/s11120-004-2082-7] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Accepted: 07/17/2004] [Indexed: 05/04/2023]
Abstract
In cyanobacteria, after transport by specific permeases, ammonium is incorporated into carbon skeletons by the sequential action of glutamine synthetase (GS) and glutamate synthase (GOGAT). Two types of GS (GSI and GSIII) and two types of GOGAT (ferredoxin-GOGAT and NADH-GOGAT) have been characterized in cyanobacteria. The carbon skeleton substrate of the GS-GOGAT pathway is 2-oxoglutarate that is synthesized by the isocitrate dehydrogenase (IDH). In order to maintain the C-N balance and the amino acid pools homeostasis, ammonium assimilation is tightly regulated. The key regulatory point is the GS, which is controlled at transcriptional and posttranscriptional levels. The transcription factor NtcA plays a critical role regulating the expression of the GS and the IDH encoding genes. In the unicellular cyanobacterium Synechocystis sp. PCC 6803, NtcA controls also the expression of two small proteins (IF7 and IF17) that inhibit the activity of GS by direct protein-protein interaction. Cyanobacteria perceive nitrogen status by sensing the intracellular concentration of 2-oxoglutarate, a signaling metabolite that is able to modulate allosterically the function of NtcA, in vitro. In vivo, a functional dependence between NtcA and the signal transduction protein PII in controlling NtcA-dependent genes has been also shown.
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Affiliation(s)
- M Isabel Muro-Pastor
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Isla de la Cartuja, Universidad de Sevilla-CSIC, Av. Américo Vespucio s/n, Seville 41092, Spain. imuro@ ibvf.csic.es
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18
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Forchhammer K. Global carbon/nitrogen control by PII signal transduction in cyanobacteria: from signals to targets. FEMS Microbiol Rev 2004; 28:319-33. [PMID: 15449606 DOI: 10.1016/j.femsre.2003.11.001] [Citation(s) in RCA: 206] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PII signal transduction plays a pervasive role in microbial nitrogen control. Different phylogenetic lineages have developed various signal transduction schemes around the highly conserved core of the signalling system, which consists of the PII proteins. Among all various bacterial PII signalling systems, the one in cyanobacteria is so far unique: in unicellular strains, the mode of covalent modification is by serine phosphorylation and the interpretation of the cellular nitrogen status occurs by measuring the 2-oxoglutarate levels. Recent advances have been the identification of the phospho-PII phosphatase, the resolution of the crystal structure of PII proteins from Synechococcus and Synechocystis strains and the identification of novel functions of PII regulation in cyanobacteria, which highlight the central role of PII signalling for the acclimation to changing carbon-nitrogen regimes.
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Affiliation(s)
- Karl Forchhammer
- Institut für Mikrobiologie und Molekularbiologie, Interdisziplinäres Forschungszentrum der Universität Giessen, Heinrich-Buff-Ring 26-32, Giessen 35392, Germany.
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Muro-Pastor MI, Reyes JC, Florencio FJ. Cyanobacteria perceive nitrogen status by sensing intracellular 2-oxoglutarate levels. J Biol Chem 2001; 276:38320-8. [PMID: 11479309 DOI: 10.1074/jbc.m105297200] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The regulatory circuits that control nitrogen metabolism are relatively well known in several bacterial model groups. However, much less is understood about how the nitrogen status of the cell is perceived in vivo. In cyanobacteria, the transcription factor NtcA is required for regulation (activation or repression) of an extensive number of genes involved in nitrogen metabolism. In contrast, how NtcA activity is regulated is largely unknown. Assimilation of ammonium by most microorganisms occurs through the sequential action of two enzymes: glutamine synthetase (GS) and glutamate synthase. Interestingly, regulation of the expression of NtcA-dependent genes in the cyanobacterium Synechocystis sp. PCC 6803 is altered in mutants with modified levels of GS activity. Two types of mutants were analyzed: glnA null mutants that lack GS type I and gif mutants unable to inactivate GS in the presence of ammonium. Changes in the intracellular pools of 19 different amino acids and the keto acid 2-oxoglutarate were recorded in wild-type and mutant strains under different nitrogen conditions. Our data strongly indicate that the nitrogen status in cyanobacteria is perceived as changes in the intracellular 2-oxoglutarate pool.
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Affiliation(s)
- M I Muro-Pastor
- Instituto de Bioquimica Vegetal y Fotosintesis, Universidad de Sevilla-Consejo Superior de Investigaciones Cientificas, Centro de Investigaciones Cientificas Isla de la Cartuja, Avenida Américo Vespucio s/n, Isla de la Cartuja, E-41092 Sevilla, Spain
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20
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Luque I, Zabulon G, Contreras A, Houmard J. Convergence of two global transcriptional regulators on nitrogen induction of the stress-acclimation gene nblA in the cyanobacterium Synechococcus sp. PCC 7942. Mol Microbiol 2001; 41:937-47. [PMID: 11532155 DOI: 10.1046/j.1365-2958.2001.02566.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cyanobacteria respond to environmental stress conditions by degrading their phycobilisomes, the light harvesting complexes for photosynthesis. The expression of nblA, a key gene in this process, is controlled by the response regulator NblR in Synechococcus sp. PCC 7942. Here we show that, under nitrogen stress, nblA is also regulated by NtcA, the global regulator for nitrogen control. NtcA activation of nblA was found to be nitrogen-specific and did not take place under sulphur stress. Transcripts from the two major transcription start points (tsp) for the nblA gene were induced in response to nitrogen and sulphur starvation. The most active one (tspII) required both NblR and NtcA to induce full nblA expression under nitrogen starvation. NblR and NtcA bound in vitro to a DNA fragment from the nblA promoter region, suggesting that, under nitrogen stress, both NblR and NtcA activate the main regulated promoter (PnblA-2) by direct DNA-binding. The structure of PnblA-2 differs from that of the canonical NtcA-activated promoter and it is therefore proposed to represent a novel type of NtcA-dependent promoter. We analysed expression patterns from ntcA and selected NtcA targets in NtcA(-), NblR(-) and wild-type strains, and discuss data suggesting further interrelations between phycobilisome degradation and nitrogen assimilation regulatory pathways.
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Affiliation(s)
- I Luque
- Unité Mixte de Recherche 8543, Centre National de la Recherche Scientifique, Photorégulation et Dynamique des Membranes Végétales, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris cedex 05, France.
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21
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Affiliation(s)
- A Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, E-41092 Seville, Spain
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22
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Sauer J, Dirmeier U, Forchhammer K. The Synechococcus strain PCC 7942 glnN product (glutamine synthetase III) helps recovery from prolonged nitrogen chlorosis. J Bacteriol 2000; 182:5615-9. [PMID: 10986271 PMCID: PMC111011 DOI: 10.1128/jb.182.19.5615-5619.2000] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacterium Synechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression of glnN is impaired in NtcA- and P(II)-deficient mutants. The only parameter which was negatively affected in the glnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen.
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Affiliation(s)
- J Sauer
- Institut für Mikrobiologie und Molekularbiologie der Justus-Liebig-Universität Giessen, D-35392 Giessen, Germany
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