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Ensinck D, Gerhardt ECM, Rollan L, Huergo LF, Gramajo H, Diacovich L. The PII protein interacts with the Amt ammonium transport and modulates nitrate/nitrite assimilation in mycobacteria. Front Microbiol 2024; 15:1366111. [PMID: 38591044 PMCID: PMC11001197 DOI: 10.3389/fmicb.2024.1366111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 03/04/2024] [Indexed: 04/10/2024] Open
Abstract
PII proteins are signal transduction proteins that belong to a widely distributed family of proteins involved in the modulation of different metabolisms in bacteria. These proteins are homotrimers carrying a flexible loop, named T-loop, which changes its conformation due to the recognition of diverse key metabolites, ADP, ATP, and 2-oxoglutarate. PII proteins interact with different partners to primarily regulate a set of nitrogen pathways. In some organisms, PII proteins can also control carbon metabolism by interacting with the biotin carboxyl carrier protein (BCCP), a key component of the acetyl-CoA carboxylase (ACC) enzyme complex, inhibiting its activity with the consequent reduction of fatty acid biosynthesis. Most bacteria contain at least two PII proteins, named GlnB and GlnK, with different regulatory roles. In mycobacteria, only one PII protein was identified, and the three-dimensional structure was solved, however, its physiological role is unknown. In this study we purified the Mycobacterium tuberculosis (M. tb) PII protein, named GlnB, and showed that it weakly interacts with the AccA3 protein, the α subunit shared by the three different, and essential, Acyl-CoA carboxylase complexes (ACCase 4, 5, and 6) present in M. tb. A M. smegmatis deletion mutant, ∆MsPII, exhibited a growth deficiency on nitrate and nitrite as unique nitrogen sources, and accumulated nitrite in the culture supernatant. In addition, M. tb PII protein was able to interact with the C-terminal domain of the ammonium transporter Amt establishing the ancestral role for this PII protein as a GlnK functioning protein.
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Affiliation(s)
- Delfina Ensinck
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Edileusa C. M. Gerhardt
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
| | - Lara Rollan
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Luciano F. Huergo
- Setor Litoral, Federal University of Paraná, Universidade Federal do Paraná (UFPR), Matinhos, Paraná, Brazil
- Graduated Program in Sciences-Biochemistry, Universidade Federal do Paraná (UFPR), Curitiba, Paraná, Brazil
| | - Hugo Gramajo
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Lautaro Diacovich
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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Moreno-Paz M, dos Santos Severino RS, Sánchez-García L, Manchado JM, García-Villadangos M, Aguirre J, Fernández-Martínez MA, Carrizo D, Kobayashi L, Dave A, Warren-Rhodes K, Davila A, Stoker CR, Glass B, Parro V. Life Detection and Microbial Biomarker Profiling with Signs of Life Detector-Life Detector Chip During a Mars Drilling Simulation Campaign in the Hyperarid Core of the Atacama Desert. ASTROBIOLOGY 2023; 23:1259-1283. [PMID: 37930382 PMCID: PMC10825288 DOI: 10.1089/ast.2021.0174] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 07/02/2023] [Indexed: 11/07/2023]
Abstract
The low organic matter content in the hyperarid core of the Atacama Desert, together with abrupt temperature shifts and high ultraviolet radiation at its surface, makes this region one of the best terrestrial analogs of Mars and one of the best scenarios for testing instrumentation devoted to in situ planetary exploration. We have operated remotely and autonomously the SOLID-LDChip (Signs of Life Detector-Life Detector Chip), an antibody microarray-based sensor instrument, as part of a rover payload during the 2019 NASA Atacama Rover Astrobiology Drilling Studies (ARADS) Mars drilling simulation campaign. A robotic arm collected drilled cuttings down to 80 cm depth and loaded SOLID to process and assay them with LDChip for searching for molecular biomarkers. A remote science team received and analyzed telemetry data and LDChip results. The data revealed the presence of microbial markers from Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Cyanobacteria to be relatively more abundant in the middle layer (40-50 cm). In addition, the detection of several proteins from nitrogen metabolism indicates a pivotal role in the system. These findings were corroborated and complemented on "returned samples" to the lab by a comprehensive analysis that included DNA sequencing, metaproteomics, and a metabolic reconstruction of the sampled area. Altogether, the results describe a relatively complex microbial community with members capable of nitrogen fixation and denitrification, sulfur oxidation and reduction, or triggering oxidative stress responses, among other traits. This remote operation demonstrated the high maturity of SOLID-LDChip as a powerful tool for remote in situ life detection for future missions in the Solar System.
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Affiliation(s)
- Mercedes Moreno-Paz
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
| | - Rita Sofia dos Santos Severino
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
- Departament of Física y Matemáticas y de Automática, University of Alcalá de Henares (UAH), Madrid, Spain
| | - Laura Sánchez-García
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
| | - Juan Manuel Manchado
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
| | | | - Jacobo Aguirre
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
| | - Miguel Angel Fernández-Martínez
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
- Department of Natural Resource Sciences, McGill University, Québec, Canada
| | - Daniel Carrizo
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
| | - Linda Kobayashi
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
| | - Arwen Dave
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
| | - Kim Warren-Rhodes
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
- Carl Sagan Center, SETI Institute, Mountain View, California, USA
| | - Alfonso Davila
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
| | - Carol R. Stoker
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
| | - Brian Glass
- Space Science Division and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA
| | - Víctor Parro
- Department of Molecular Evolution, Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain
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Sieradzki ET, Nuccio EE, Pett-Ridge J, Firestone MK. Rhizosphere and detritusphere habitats modulate expression of soil N-cycling genes during plant development. mSystems 2023; 8:e0031523. [PMID: 37754554 PMCID: PMC10654102 DOI: 10.1128/msystems.00315-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 08/07/2023] [Indexed: 09/28/2023] Open
Abstract
IMPORTANCE Plant roots modulate microbial nitrogen (N) cycling by regulating the supply of root-derived carbon and nitrogen uptake. These differences in resource availability cause distinct micro-habitats to develop: soil near living roots, decaying roots, near both, or outside the direct influence of roots. While many environmental factors and genes control the microbial processes involved in the nitrogen cycle, most research has focused on single genes and pathways, neglecting the interactive effects these pathways have on each other. The processes controlled by these pathways determine consumption and production of N by soil microorganisms. We followed the expression of N-cycling genes in four soil microhabitats over a period of active root growth for an annual grass. We found that the presence of root litter and living roots significantly altered gene expression involved in multiple nitrogen pathways, as well as tradeoffs between pathways, which ultimately regulate N availability to plants.
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Affiliation(s)
- Ella T. Sieradzki
- Department of Environmental Science, Policy and Management, University of California Berkeley, Berkeley, California, USA
| | - Erin E. Nuccio
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Jennifer Pett-Ridge
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
- Life & Environmental Sciences Department, UC Merced, Merced, California, USA
- Innovative Genomics Institute, UC Berkeley, Berkeley, California, USA
| | - Mary K. Firestone
- Department of Environmental Science, Policy and Management, University of California Berkeley, Berkeley, California, USA
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Monteagudo-Cascales E, Santero E, Canosa I. The Regulatory Hierarchy Following Signal Integration by the CbrAB Two-Component System: Diversity of Responses and Functions. Genes (Basel) 2022; 13:genes13020375. [PMID: 35205417 PMCID: PMC8871633 DOI: 10.3390/genes13020375] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 02/14/2022] [Accepted: 02/16/2022] [Indexed: 02/04/2023] Open
Abstract
CbrAB is a two-component system, unique to bacteria of the family Pseudomonaceae, capable of integrating signals and involved in a multitude of physiological processes that allow bacterial adaptation to a wide variety of varying environmental conditions. This regulatory system provides a great metabolic versatility that results in excellent adaptability and metabolic optimization. The two-component system (TCS) CbrA-CbrB is on top of a hierarchical regulatory cascade and interacts with other regulatory systems at different levels, resulting in a robust output. Among the regulatory systems found at the same or lower levels of CbrAB are the NtrBC nitrogen availability adaptation system, the Crc/Hfq carbon catabolite repression cascade in Pseudomonas, or interactions with the GacSA TCS or alternative sigma ECF factor, such as SigX. The interplay between regulatory mechanisms controls a number of physiological processes that intervene in important aspects of bacterial adaptation and survival. These include the hierarchy in the use of carbon sources, virulence or resistance to antibiotics, stress response or definition of the bacterial lifestyle. The multiple actions of the CbrAB TCS result in an important competitive advantage.
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Affiliation(s)
| | - Eduardo Santero
- Departamento de Biología Molecular e Ingeniería Bioquímica, Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo, CSIC, Junta de Andalucía, 41013 Seville, Spain;
| | - Inés Canosa
- Departamento de Biología Molecular e Ingeniería Bioquímica, Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo, CSIC, Junta de Andalucía, 41013 Seville, Spain;
- Correspondence: ; Tel.: +34-954349052
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5
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Morikawa Y, Morimoto S, Yoshida E, Naka S, Inaba H, Matsumoto-Nakano M. Identification and functional analysis of glutamine transporter in Streptococcus mutans. J Oral Microbiol 2020; 12:1797320. [PMID: 32944153 PMCID: PMC7482851 DOI: 10.1080/20002297.2020.1797320] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Background Streptococcus mutans, a biofilm-forming bacterium, possesses several transporters that function as import/export molecules. Among them, the PII protein family is composed of members that regulate glutamine synthesis in bacterial species. Objective In this study, we characterized the function of the glutamine transporter in S. mutans MT8148. Methods The SMU.732 gene, corresponding to glnP in S. mutans, is homologous to the glutamine transporter gene in Bacillus subtilis. We constructed a glnP-inactivated mutant strain (GEMR) and a complement strain (comp-GEMR) and evaluated their biological functions. Results Growth of GEMR was similar in the presence and absence of glutamine, whereas the growth rates of MT8148 and comp-GEMR were significantly lower in the presence of glutamine as compared to its absence. Furthermore, biofilms formed by MT8148 and comp-GEMR were significantly thicker than that formed by GEMR, while the GEMR strain showed a significantly lower survival rate in an acidic environment than the other strains. Addition of n-phenyl-2-naphthylamine, used to label of the membrane, led to increased fluorescence intensity of MT8148 and GEMR, albeit that was significantly lower in the latter. Conclusions These results suggest that glnP is associated with glutamine transport in S. mutans, especially the import of glutamine involved in biofilm formation.
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Affiliation(s)
- Yuko Morikawa
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Setsuyo Morimoto
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Eri Yoshida
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Shuhei Naka
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Hiroaki Inaba
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Michiyo Matsumoto-Nakano
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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Selim KA, Lapina T, Forchhammer K, Ermilova E. Interaction of N-acetyl-l-glutamate kinase with the PII signal transducer in the non-photosynthetic alga Polytomella parva: Co-evolution towards a hetero-oligomeric enzyme. FEBS J 2019; 287:465-482. [PMID: 31287617 PMCID: PMC7027753 DOI: 10.1111/febs.14989] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/17/2019] [Accepted: 07/06/2019] [Indexed: 12/27/2022]
Abstract
During evolution, several algae and plants became heterotrophic and lost photosynthesis; however, in most cases, a nonphotosynthetic plastid was maintained. Among these organisms, the colourless alga Polytomella parva is a special case, as its plastid is devoid of any DNA, but is maintained for specific metabolic tasks carried out by nuclear encoded enzymes. This makes P. parva attractive to study molecular events underlying the transition from autotrophic to heterotrophic lifestyle. Here we characterize metabolic adaptation strategies of P. parva in comparison to the closely related photosynthetic alga Chlamydomonas reinhardtii with a focus on the role of plastid‐localized PII signalling protein. Polytomella parva accumulates significantly higher amounts of most TCA cycle intermediates as well as glutamate, aspartate and arginine, the latter being specific for the colourless plastid. Correlating with the altered metabolite status, the carbon/nitrogen sensory PII signalling protein and its regulatory target N‐acetyl‐l‐glutamate‐kinase (NAGK; the controlling enzyme of arginine biosynthesis) show unique features: They have co‐evolved into a stable hetero‐oligomeric complex, irrespective of effector molecules. The PII signalling protein, so far known as a transiently interacting signalling protein, appears as a permanent subunit of the enzyme NAGK. NAGK requires PII to properly sense the feedback inhibitor arginine, and moreover, PII tunes arginine‐inhibition in response to glutamine. No other PII effector molecules interfere, indicating that the PII‐NAGK system in P. parva has lost the ability to estimate the cellular energy and carbon status but has specialized to provide an entirely glutamine‐dependent arginine feedback control, highlighting the evolutionary plasticity of PII signalling system.
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Affiliation(s)
- Khaled A Selim
- Department of Microbiology/Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard-Karls-Universität Tübingen, Germany
| | - Tatyana Lapina
- Biological Faculty, Saint-Petersburg State University, Russia
| | - Karl Forchhammer
- Department of Microbiology/Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard-Karls-Universität Tübingen, Germany
| | - Elena Ermilova
- Biological Faculty, Saint-Petersburg State University, Russia
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The PII signaling protein from red algae represents an evolutionary link between cyanobacterial and Chloroplastida PII proteins. Sci Rep 2018; 8:790. [PMID: 29335634 PMCID: PMC5768801 DOI: 10.1038/s41598-017-19046-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/15/2017] [Indexed: 11/16/2022] Open
Abstract
PII superfamily consists of widespread signal transduction proteins found in all domains of life. Whereas they are well-studied in Archaea, Bacteria and Chloroplastida, no PII homolog has been analyzed in Rhodophyta (red algae), where PII is encoded by a chloroplast localized glnB gene. Here, we characterized relevant sensory properties of PII from the red alga Porphyra purpurea (PpPII) in comparison to PII proteins from different phyla of oxygenic phototrophs (cyanobacteria, Chlamydomonas and Physcomitrella) to assess evolutionary conservation versus adaptive properties. Like its cyanobacterial counterparts, PpPII binds ATP/ADP and 2-oxoglutarate in synergy with ATP. However, green algae and land plant PII proteins lost the ability to bind ADP. In contrast to PII proteins from green algae and land plants, PpPII enhances the activity of N-acetyl-L-glutamate kinase (NAGK) and relieves it from feedback inhibition by arginine in a glutamine-independent manner. Like PII from Chloroplastida, PpPII is not able to interact with the cyanobacterial transcriptional co-activator PipX. These data emphasize the conserved role of NAGK as a major PII-interactor throughout the evolution of oxygenic phototrophs, and confirms the specific role of PipX for cyanobacteria. Our results highlight the PII signaling system in red algae as an evolutionary intermediate between Cyanobacteria and Chlorophyta.
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8
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Forchhammer K, Lüddecke J. Sensory properties of the PII signalling protein family. FEBS J 2015; 283:425-37. [PMID: 26527104 DOI: 10.1111/febs.13584] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 10/06/2015] [Accepted: 10/28/2015] [Indexed: 11/30/2022]
Abstract
PII signalling proteins constitute one of the largest families of signalling proteins in nature. An even larger superfamily of trimeric sensory proteins with the same architectural principle as PII proteins appears in protein structure databases. Large surface-exposed flexible loops protrude from the intersubunit faces, where effector molecules are bound that tune the conformation of the loops. Via this mechanism, PII proteins control target proteins in response to cellular ATP/ADP levels and the 2-oxoglutarate status, thereby coordinating the cellular carbon/nitrogen balance. The antagonistic (ATP versus ADP) and synergistic (2-oxoglutarate and ATP) mode of effector molecule binding is further affected by PII -receptor interaction, leading to a highly sophisticated signalling network organized by PII . Altogether, it appears that PII is a multitasking information processor that, depending on its interaction environment, differentially transmits information on the energy status and the cellular 2-oxoglutarate level. In addition to the basic mode of PII function, several bacterial PII proteins may transmit a signal of the cellular glutamine status via covalent modification. Remarkably, during the evolution of plant chloroplasts, glutamine signalling by PII proteins was re-established by acquisition of a short sequence extension at the C-terminus. This plant-specific C-terminus makes the interaction of plant PII proteins with one of its targets, the arginine biosynthetic enzyme N-acetyl-glutamate kinase, glutamine-dependent.
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Affiliation(s)
- Karl Forchhammer
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Eberhard-Karls-Universität Tübingen, Germany
| | - Jan Lüddecke
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Eberhard-Karls-Universität Tübingen, Germany
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9
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Lüddecke J, Forchhammer K. Energy Sensing versus 2-Oxoglutarate Dependent ATPase Switch in the Control of Synechococcus PII Interaction with Its Targets NAGK and PipX. PLoS One 2015; 10:e0137114. [PMID: 26317540 PMCID: PMC4552645 DOI: 10.1371/journal.pone.0137114] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 08/07/2015] [Indexed: 12/20/2022] Open
Abstract
PII proteins constitute a superfamily of highly conserved signaling devices, common in all domains of life. Through binding of the metabolites ATP, ADP and 2-oxoglutarate (2-OG), they undergo conformational changes which allow them to regulate a variety of target proteins including enzymes, transport proteins and transcription factors. But, in reverse, these target proteins also modulate the metabolite sensing properties of PII, as has been recently shown. We used this effect to refine our PII based Förster resonance energy transfer (FRET) sensor and amplify its sensitivity towards ADP. With this enhanced sensor setup we addressed the question whether the PII protein from the model organism Synechococcus elongatus autonomously switches into the ADP conformation through ATPase activity as proposed in a recently published model. The present study disproves ATPase activity as a relevant mechanism for the transition of PII into the ADP state. In the absence of 2-OG, only the ATP/ADP ratio and concentration of ADP directs the competitive interaction of PII with two targets, one of which preferentially binds PII in the ATP-state, the other in the ADP-state.
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Affiliation(s)
- Jan Lüddecke
- Interfaculty Institute for Microbiology and Infection Medicine, Division Organismic Interactions, University of Tübingen, Auf der Morgenstelle 28, D-72076, Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine, Division Organismic Interactions, University of Tübingen, Auf der Morgenstelle 28, D-72076, Tübingen, Germany
- * E-mail:
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10
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Minaeva E, Forchhammer K, Ermilova E. Glutamine Assimilation and Feedback Regulation of L-acetyl-N-glutamate Kinase Activity in Chlorella variabilis NC64A Results in Changes in Arginine Pools. Protist 2015; 166:493-505. [PMID: 26356535 DOI: 10.1016/j.protis.2015.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 07/07/2015] [Accepted: 08/01/2015] [Indexed: 11/16/2022]
Abstract
Glutamine is a metabolite of central importance in nitrogen metabolism of microorganisms and plants. The Chlorella PII signaling protein controls, in a glutamine-dependent manner, the key enzyme of the ornithine/arginine biosynthesis pathway, N-acetyl-L-glutamate kinase (NAGK) that leads to arginine formation. We provide evidence that glutamine promotes effective growth of C. variabilis strain NC64A. The present study shows that externally supplied glutamine directly influences the internal pool of arginine in NC64A. Glutamine synthetase (GS) catalyzes the ATP-dependent conversion of glutamate and ammonium to glutamine. The results of this study demonstrate that glutamine acts as a negative effector of GS activity. These data emphasize the importance of glutamine-dependent coupling of metabolism and signaling as components of an efficient pathway allowing the maintenance of metabolic homeostasis and sustaining growth of Chlorella.
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Affiliation(s)
- Ekaterina Minaeva
- Lab Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Elena Ermilova
- Lab Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia.
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11
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Nambu M, Tatsukami Y, Morisaka H, Kuroda K, Ueda M. Quantitative time-course proteome analysis of Mesorhizobium loti during nodule maturation. J Proteomics 2015; 125:112-20. [DOI: 10.1016/j.jprot.2015.04.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/22/2015] [Accepted: 04/27/2015] [Indexed: 11/30/2022]
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12
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Roelvink PW, Van Den Bos RC. Regulation of nitrogen fixation in diazotrophs: the regulatorynifA gene and its characteristics. ACTA ACUST UNITED AC 2015. [DOI: 10.1111/j.1438-8677.1989.tb01349.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- P. W. Roelvink
- Department of Molecular Biology; Wageningen Agricultural University; Dreijenlaan 3 6703 HA Wageningen The Netherlands
| | - R. C. Van Den Bos
- Department of Molecular Biology; Wageningen Agricultural University; Dreijenlaan 3 6703 HA Wageningen The Netherlands
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13
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Chellamuthu VR, Ermilova E, Lapina T, Lüddecke J, Minaeva E, Herrmann C, Hartmann MD, Forchhammer K. A widespread glutamine-sensing mechanism in the plant kingdom. Cell 2015; 159:1188-1199. [PMID: 25416954 DOI: 10.1016/j.cell.2014.10.015] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 08/13/2014] [Accepted: 09/26/2014] [Indexed: 11/19/2022]
Abstract
Glutamine is the primary metabolite of nitrogen assimilation from inorganic nitrogen sources in microorganisms and plants. The ability to monitor cellular nitrogen status is pivotal for maintaining metabolic homeostasis and sustaining growth. The present study identifies a glutamine-sensing mechanism common in the entire plant kingdom except Brassicaceae. The plastid-localized PII signaling protein controls, in a glutamine-dependent manner, the key enzyme of the ornithine synthesis pathway, N-acetyl-l-glutamate kinase (NAGK), that leads to arginine and polyamine formation. Crystal structures reveal that the plant-specific C-terminal extension of PII, which we term the Q loop, forms a low-affinity glutamine-binding site. Glutamine binding alters PII conformation, promoting interaction and activation of NAGK. The binding motif is highly conserved in plants except Brassicaceae. A functional Q loop restores glutamine sensing in a recombinant Arabidopsis thaliana PII protein, demonstrating the modular concept of the glutamine-sensing mechanism adopted by PII proteins during the evolution of plant chloroplasts.
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Affiliation(s)
- Vasuki-Ranjani Chellamuthu
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany; Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Elena Ermilova
- Lab Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia
| | - Tatjana Lapina
- Lab Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia
| | - Jan Lüddecke
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Ekaterina Minaeva
- Lab Adaptation in Microorganisms, Biological Faculty, Saint-Petersburg State University, Universitetskaya em. 7/9, 199034 Saint-Petersburg, Russia
| | - Christina Herrmann
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Marcus D Hartmann
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
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14
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Ardin AC, Fujita K, Nagayama K, Takashima Y, Nomura R, Nakano K, Ooshima T, Matsumoto-Nakano M. Identification and functional analysis of an ammonium transporter in Streptococcus mutans. PLoS One 2014; 9:e107569. [PMID: 25229891 PMCID: PMC4167856 DOI: 10.1371/journal.pone.0107569] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 08/13/2014] [Indexed: 12/26/2022] Open
Abstract
Streptococcus mutans, a Gram-positive bacterium, is considered to be a major etiologic agent of human dental caries and reported to form biofilms known as dental plaque on tooth surfaces. This organism is also known to possess a large number of transport proteins in the cell membrane for export and import of molecules. Nitrogen is an essential nutrient for Gram-positive bacteria, though alternative sources such as ammonium can also be utilized. In order to obtain nitrogen for macromolecular synthesis, nitrogen-containing compounds must be transported into the cell. However, the ammonium transporter in S. mutans remains to be characterized. The present study focused on characterizing the ammonium transporter gene of S. mutans and its operon, while related regulatory genes were also analyzed. The SMU.1658 gene corresponding to nrgA in S. mutans is homologous to the ammonium transporter gene in Bacillus subtilis and SMU.1657, located upstream of the nrgA gene and predicted to be glnB, is a member of the PII protein family. Using a nrgA-deficient mutant strain (NRGD), we examined bacterial growth in the presence of ammonium, calcium chloride, and manganese sulfate. Fluorescent efflux assays were also performed to reveal export molecules associated with the ammonium transporter. The growth rate of NRGD was lower, while its fluorescent intensity was much higher as compared to the parental strain. In addition, confocal laser scanning microscopy revealed that the structure of biofilms formed by NRGD was drastically different than that of the parental strain. Furthermore, transcriptional analysis showed that the nrgA gene was co-transcribed with the glnB gene. These results suggest that the nrgA gene in S. mutans is essential for export of molecules and biofilm formation.
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Affiliation(s)
- Arifah Chieko Ardin
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Kazuyo Fujita
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Kayoko Nagayama
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Yukiko Takashima
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Ryota Nomura
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Kazuhiko Nakano
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Takashi Ooshima
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Michiyo Matsumoto-Nakano
- Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
- * E-mail:
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15
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Ma CW, Lüddecke J, Forchhammer K, Zeng AP. Population shift of binding pocket size and dynamic correlation analysis shed new light on the anticooperative mechanism of PII protein. Proteins 2014; 82:1048-59. [PMID: 24218085 PMCID: PMC4282546 DOI: 10.1002/prot.24477] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 10/24/2013] [Accepted: 11/04/2013] [Indexed: 12/03/2022]
Abstract
PII protein is one of the largest families of signal transduction proteins in archaea, bacteria, and plants, controlling key processes of nitrogen assimilation. An intriguing characteristic for many PII proteins is that the three ligand binding sites exhibit anticooperative allosteric regulation. In this work, PII protein from Synechococcus elongatus, a model for cyanobacteria and plant PII proteins, is utilized to reveal the anticooperative mechanism upon binding of 2-oxoglutarate (2-OG). To this end, a method is proposed to define the binding pocket size by identifying residues that contribute greatly to the binding of 2-OG. It is found that the anticooperativity is realized through population shift of the binding pocket size in an asymmetric manner. Furthermore, a new algorithm based on the dynamic correlation analysis is developed and utilized to discover residues that mediate the anticooperative process with high probability. It is surprising to find that the T-loop, which is believed to be responsible for mediating the binding of PII with its target proteins, also takes part in the intersubunit signal transduction process. Experimental results of PII variants further confirmed the influence of T-loop on the anticooperative regulation, especially on binding of the third 2-OG. These discoveries extend our understanding of the PII T-loop from being essential in versatile binding of target protein to signal-mediating in the anticooperative allosteric regulation.
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Affiliation(s)
- Cheng-Wei Ma
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of TechnologyD-21073, Hamburg, Germany
| | - Jan Lüddecke
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls-Universität Tübingen72076, Tübingen, Germany
| | - Karl Forchhammer
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls-Universität Tübingen72076, Tübingen, Germany
| | - An-Ping Zeng
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of TechnologyD-21073, Hamburg, Germany
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16
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Zeth K, Fokina O, Forchhammer K. Structural basis and target-specific modulation of ADP sensing by the Synechococcus elongatus PII signaling protein. J Biol Chem 2014; 289:8960-72. [PMID: 24519945 DOI: 10.1074/jbc.m113.536557] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PII signaling proteins comprise one of the most versatile signaling devices in nature and have a highly conserved structure. In cyanobacteria, PipX and N-acetyl-L-glutamate kinase are receptors of PII signaling, and these interactions are modulated by ADP, ATP, and 2-oxoglutarate. These effector molecules bind interdependently to three anti-cooperative binding sites on the trimeric PII protein and thereby affect its structure. Here we used the PII protein from Synechococcus elongatus PCC 7942 to reveal the structural basis of anti-cooperative ADP binding. Furthermore, we clarified the mutual influence of PII-receptor interaction and sensing of the ATP/ADP ratio. The crystal structures of two forms of trimeric PII, one with one ADP bound and the other with all three ADP-binding sites occupied, revealed significant differences in the ADP binding mode: at one site (S1) ADP is tightly bound through side-chain and main-chain interactions, whereas at the other two sites (S2 and S3) the ADP molecules are only bound by main-chain interactions. In the presence of the PII-receptor PipX, the affinity of ADP to the first binding site S1 strongly increases, whereas the affinity for ATP decreases due to PipX favoring the S1 conformation of PII-ADP. In consequence, the PII-PipX interaction is highly sensitive to subtle fluctuations in the ATP/ADP ratio. By contrast, the PII-N-acetyl-L-glutamate kinase interaction, which is negatively affected by ADP, is insensitive to these fluctuations. Modulation of the metabolite-sensing properties of PII by its receptors allows PII to differentially perceive signals in a target-specific manner and to perform multitasking signal transduction.
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Affiliation(s)
- Kornelius Zeth
- From the Max Planck Institute for Developmental Biology, Department of Protein Evolution, Spemannstrasse 35, 72076 Tübingen, Germany and
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17
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Lüddecke J, Forchhammer K. From PII signaling to metabolite sensing: a novel 2-oxoglutarate sensor that details PII-NAGK complex formation. PLoS One 2013; 8:e83181. [PMID: 24349456 PMCID: PMC3861474 DOI: 10.1371/journal.pone.0083181] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 10/31/2013] [Indexed: 11/29/2022] Open
Abstract
The widespread PII signal transduction proteins are known for integrating signals of nitrogen and energy supply and regulating cellular behavior by interacting with a multitude of target proteins. The PII protein of the cyanobacterium Synechococcus elongatus forms complexes with the controlling enzyme of arginine synthesis, N-acetyl-L-glutamate kinase (NAGK) in a 2-oxoglutarate- and ATP/ADP-dependent manner. Fusing NAGK and PII proteins to either CFP or YFP yielded a FRET sensor that specifically responded to 2-oxoglutarate. The impact of the fluorescent tags on PII and NAGK was evaluated by enzyme assays, surface plasmon resonance spectroscopy and isothermal calorimetric experiments. The developed FRET sensor provides real-time data on PII - NAGK interaction and its modulation by the effector molecules ATP, ADP and 2-oxoglutarate in vitro. Additionally to its utility to monitor 2-oxoglutarate levels, the FRET assay provided novel insights into PII - NAGK complex formation: (i) It revealed the formation of an encounter-complex between PII and NAGK, which holds the proteins in proximity even in the presence of inhibitors of complex formation; (ii) It revealed that the PII T-loop residue Ser49 is neither essential for complex formation with NAGK nor for activation of the enzyme but necessary to form a stable complex and efficiently relieve NAGK from arginine inhibition; (iii) It showed that arginine stabilizes the NAGK hexamer and stimulates PII - NAGK interaction.
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Affiliation(s)
- Jan Lüddecke
- Interfaculty Institute for Microbiology and Infection Medicine (IMIT), Eberhard Karls University, Tübingen, Germany
| | - Karl Forchhammer
- Interfaculty Institute for Microbiology and Infection Medicine (IMIT), Eberhard Karls University, Tübingen, Germany
- * E-mail:
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18
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van Heeswijk WC, Westerhoff HV, Boogerd FC. Nitrogen assimilation in Escherichia coli: putting molecular data into a systems perspective. Microbiol Mol Biol Rev 2013; 77:628-95. [PMID: 24296575 PMCID: PMC3973380 DOI: 10.1128/mmbr.00025-13] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
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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19
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Williams KJ, Bennett MH, Barton GR, Jenkins VA, Robertson BD. Adenylylation of mycobacterial Glnk (PII) protein is induced by nitrogen limitation. Tuberculosis (Edinb) 2013; 93:198-206. [PMID: 23352854 PMCID: PMC3612183 DOI: 10.1016/j.tube.2012.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/17/2012] [Accepted: 12/22/2012] [Indexed: 12/03/2022]
Abstract
PII proteins are pivotal regulators of nitrogen metabolism in most prokaryotes, controlling the activities of many targets, including nitrogen assimilation enzymes, two component regulatory systems and ammonium transport proteins. Escherichia coli contains two PII-like proteins, PII (product of glnB) and GlnK, both of which are uridylylated under nitrogen limitation at a conserved Tyrosine-51 residue by GlnD (a uridylyl transferase). PII-uridylylation in E. coli controls glutamine synthetase (GS) adenylylation by GlnE and mediates the NtrB/C transcriptomic response. Mycobacteria contain only one PII protein (GlnK) which in environmental Actinomycetales is adenylylated by GlnD under nitrogen limitation. However in mycobacteria, neither the type of GlnK (PII) covalent modification nor its precise role under nitrogen limitation is known. In this study, we used LC-Tandem MS to analyse the modification state of mycobacterial GlnK (PII), and demonstrate that during nitrogen limitation GlnK from both non-pathogenic Mycobacterium smegmatis and pathogenic Mycobacterium tuberculosis is adenylylated at the Tyrosine-51 residue; we also show that GlnD is the adenylyl transferase enzyme responsible. Further analysis shows that in contrast to E. coli, GlnK (PII) adenylylation in M. tuberculosis does not regulate GS adenylylation, nor does it mediate the transcriptomic response to nitrogen limitation.
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Affiliation(s)
- Kerstin J Williams
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, UK
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20
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Teixeira PF, Dominguez-Martin MA, Nordlund S. Molecular basis for the distinct divalent cation requirement in the uridylylation of the signal transduction proteins GlnJ and GlnB from Rhodospirillum rubrum. BMC Microbiol 2012; 12:136. [PMID: 22769741 PMCID: PMC3480911 DOI: 10.1186/1471-2180-12-136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 06/20/2012] [Indexed: 11/24/2022] Open
Abstract
Background PII proteins have a fundamental role in the control of nitrogen metabolism in bacteria, through interactions with different PII targets, controlled by metabolite binding and post-translational modification, uridylylation in most organisms. In the photosynthetic bacterium Rhodospirillum rubrum, the PII proteins GlnB and GlnJ were shown, in spite of their high degree of similarity, to have different requirements for post-translational uridylylation, with respect to the divalent cations, Mg2+ and Mn2+. Results Given the importance of uridylylation in the functional interactions of PII proteins, we have hypothesized that the difference in the divalent cation requirement for the uridylylation is related to efficient binding of Mg/Mn-ATP to the PII proteins. We concluded that the amino acids at positions 42 and 85 in GlnJ and GlnB (in the vicinity of the ATP binding site) influence the divalent cation requirement for uridylylation catalyzed by GlnD. Conclusions Efficient binding of Mg/Mn-ATP to the PII proteins is required for uridylylation by GlnD. Our results show that by simply exchanging two amino acid residues, we could modulate the divalent cation requirement in the uridylylation of GlnJ and GlnB. Considering that post-translational uridylylation of PII proteins modulates their signaling properties, a different requirement for divalent cations in the modification of GlnB and GlnJ adds an extra regulatory layer to the already intricate control of PII function.
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21
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Mitra A, Fay PA, Morgan JK, Vendura KW, Versaggi SL, Riordan JT. Sigma factor N, liaison to an ntrC and rpoS dependent regulatory pathway controlling acid resistance and the LEE in enterohemorrhagic Escherichia coli. PLoS One 2012; 7:e46288. [PMID: 23029465 PMCID: PMC3459932 DOI: 10.1371/journal.pone.0046288] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 08/28/2012] [Indexed: 11/19/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is dependent on acid resistance for gastric passage and low oral infectious dose, and the locus of enterocyte effacement (LEE) for intestinal colonization. Mutation of rpoN, encoding sigma factor N (σ(N)), dramatically alters the growth-phase dependent regulation of both acid resistance and the LEE. This study reports on the determinants of σ(N)-directed acid resistance and LEE expression, and the underlying mechanism attributable to this phenotype. Glutamate-dependent acid resistance (GDAR) in TW14359ΔrpoN correlated with increased expression of the gadX-gadW regulatory circuit during exponential growth, whereas upregulation of arginine-dependent acid resistance (ADAR) genes adiA and adiC in TW14359ΔrpoN did not confer acid resistance by the ADAR mechanism. LEE regulatory (ler), structural (espA and cesT) and effector (tir) genes were downregulated in TW14359ΔrpoN, and mutation of rpoS encoding sigma factor 38 (σ(S)) in TW14359ΔrpoN restored acid resistance and LEE genes to WT levels. Stability, but not the absolute level, of σ(S) was increased in TW14359ΔrpoN; however, increased stability was not solely attributable to the GDAR and LEE expression phenotype. Complementation of TW14359ΔrpoN with a σ(N) allele that binds RNA polymerase (RNAP) but not DNA, did not restore WT levels of σ(S) stability, gadE, ler or GDAR, indicating a dependence on transcription from a σ(N) promoter(s) and not RNAP competition for the phenotype. Among a library of σ(N) enhancer binding protein mutants, only TW14359ΔntrC, inactivated for nitrogen regulatory protein NtrC, phenocopied TW14359ΔrpoN for σ(S) stability, GDAR and ler expression. The results of this study suggest that during exponential growth, NtrC-σ(N) regulate GDAR and LEE expression through downregulation of σ(S) at the post-translational level; likely by altering σ(S) stability or activity. The regulatory interplay between NtrC, other EBPs, and σ(N)-σ(S), represents a mechanism by which EHEC can coordinate GDAR, LEE expression and other cellular functions, with nitrogen availability and physiologic stimuli.
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Affiliation(s)
- Avishek Mitra
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
| | - Pamela A. Fay
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
| | - Jason K. Morgan
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
| | - Khoury W. Vendura
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
| | - Salvatore L. Versaggi
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
| | - James T. Riordan
- Department of Cell Biology, Microbiology, and Molecular Biology (CMMB), University of South Florida, Tampa, Florida, United States of America
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22
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Zeth K, Fokina O, Forchhammer K. An engineered PII protein variant that senses a novel ligand: atomic resolution structure of the complex with citrate. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:901-8. [PMID: 22868755 DOI: 10.1107/s0907444912016447] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 04/16/2012] [Indexed: 11/10/2022]
Abstract
PII proteins are central signal processing units for the regulation of nitrogen metabolism in bacteria, archaea and plants. They act in response to cellular energy, carbon and nitrogen availability. The central metabolites ATP, ADP and 2-oxoglutarate, which indicate cellular energy and carbon/nitrogen abundance, bind in a highly organized manner to PII and induce effector-molecule-dependent conformational states of the T-loop. Depending on these states, PII proteins bind and modulate the activity of various regulatory targets. A mutant variant of the Synechococcus elongatus PII protein (PII-I86N) has been identified to have impaired 2-oxoglutarate binding. Here, the PII-I86N variant was cocrystallized in the presence of ATP, magnesium and citrate and its structure was solved at a resolution of 1.05 Å. The PII-I86N variant bound citrate in place of 2-oxoglutarate. Citrate binding is mediated primarily by interactions with the ATP-coordinated magnesium ion and the backbone atoms of the T-loop. Citrate binding rearranges the conformation of the T-loop and, consistent with this, citrate suppresses the binding of PII-I86N to an NAG kinase variant, which is similar to the suppression of PII-NAG kinase complex formation by 2-OG. Based on the structures of 2-OG and citrate, homocitrate was suggested as a third ligand and an efficient response towards this molecule with different functional properties was observed. Together, these data provide a first glimpse of a genetically engineered PII variant that senses a new effector molecule.
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Affiliation(s)
- Kornelius Zeth
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
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23
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Ermilova E, Lapina T, Zalutskaya Z, Minaeva E, Fokina O, Forchhammer K. PII signal transduction protein in Chlamydomonas reinhardtii: localization and expression pattern. Protist 2012; 164:49-59. [PMID: 22578427 DOI: 10.1016/j.protis.2012.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 03/05/2012] [Accepted: 04/09/2012] [Indexed: 11/25/2022]
Abstract
Although PII signal transduction proteins have been described in bacteria, archaea and higher plants, no PII homolog has so far been characterized in green algae. In the unicellular green alga Chlamydomonas reinhardtii, the PII protein is encoded by a single nuclear gene CrGLB1. The C. reinhardtii PII (CrPII) was cloned and overexpressed with a C-terminal-fused Strep-tag II peptide. Consistent with the presence of key conserved residues necessary for trimer formation, gel filtration showed the oligomeric structure of C. reinhardtii to be a homotrimer. Under the studied culture conditions, CrPII appears not to be modified by phosphorylation. Here we show that like its plant PII homologs, the CrPII protein is localized in the chloroplast. Although the CrGLB1 transcript level increased in response to dark-light shift and nitrogen depletion, the level of mature CrPII protein did not change accordingly. Changes in the level of CrGLB1 mRNA were independent of gametogenesis. Characterization of PII in the green alga C. reinhardtii provides a framework for a more complete understanding of the function of this highly conserved signaling protein.
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Affiliation(s)
- Elena Ermilova
- Laboratory of Adaptation in Microorganisms, Biological Research Institute of St. Petersburg University, Oranienbaumskoe schosse 2, Stary Peterhof, St. Petersburg, 198504 Russia.
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Signal-transduction protein P(II) from Synechococcus elongatus PCC 7942 senses low adenylate energy charge in vitro. Biochem J 2011; 440:147-56. [PMID: 21774788 DOI: 10.1042/bj20110536] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
P(II) proteins belong to a family of highly conserved signal-transduction proteins that occurs widely in bacteria, archaea and plants. They respond to the central metabolites ATP, ADP and 2-OG (2-oxoglutarate), and control enzymes, transcription factors and transport proteins involved in nitrogen metabolism. In the present study, we examined the effect of ADP on in vitro P(II)-signalling properties for the cyanobacterium Synechococcus elongatus, a model for oxygenic phototrophic organisms. Different ADP/ATP ratios strongly affected the properties of P(II) signalling. Increasing ADP antagonized the binding of 2-OG and directly affected the interactions of P(II) with its target proteins. The resulting P(II)-signalling properties indicate that, in mixtures of ADP and ATP, P(II) trimers are occupied by mixtures of adenylate nucleotides. Binding and kinetic activation of NAGK (N-acetyl-L-glutamate kinase), the controlling enzyme of arginine biosynthesis, by P(II) was weakened by ADP, but relief from arginine inhibition remained unaffected. On the other hand, ADP enhanced the binding of P(II) to PipX, a co-activator of the transcription factor NtcA and, furthermore, antagonized the inhibitory effect of 2-OG on P(II)-PipX interaction. These results indicate that S. elongatus P(II) directly senses the adenylate energy charge, resulting in target-dependent differential modification of the P(II)-signalling properties.
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25
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Sung TY, Chung TY, Hsu CP, Hsieh MH. The ACR11 encodes a novel type of chloroplastic ACT domain repeat protein that is coordinately expressed with GLN2 in Arabidopsis. BMC PLANT BIOLOGY 2011; 11:118. [PMID: 21861936 PMCID: PMC3173338 DOI: 10.1186/1471-2229-11-118] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 08/24/2011] [Indexed: 05/08/2023]
Abstract
BACKGROUND The ACT domain, named after bacterial aspartate kinase, chorismate mutase and TyrA (prephenate dehydrogenase), is a regulatory domain that serves as an amino acid-binding site in feedback-regulated amino acid metabolic enzymes. We have previously identified a novel type of ACT domain-containing protein family, the ACT domain repeat (ACR) protein family, in Arabidopsis. Members of the ACR family, ACR1 to ACR8, contain four copies of the ACT domain that extend throughout the entire polypeptide. Here, we describe the identification of four novel ACT domain-containing proteins, namely ACR9 to ACR12, in Arabidopsis. The ACR9 and ACR10 proteins contain three copies of the ACT domain, whereas the ACR11 and ACR12 proteins have a putative transit peptide followed by two copies of the ACT domain. The functions of these plant ACR proteins are largely unknown. RESULTS The ACR11 and ACR12 proteins are predicted to target to chloroplasts. We used protoplast transient expression assay to demonstrate that the Arabidopsis ACR11- and ACR12-green fluorescent fusion proteins are localized to the chloroplast. Analysis of an ACR11 promoter-β-glucuronidase (GUS) fusion in transgenic Arabidopsis revealed that the GUS activity was mainly detected in mature leaves and sepals. Interestingly, coexpression analysis revealed that the GLN2, which encodes a chloroplastic glutamine synthetase, has the highest mutual rank in the coexpressed gene network connected to ACR11. We used RNA gel blot analysis to confirm that the expression pattern of ACR11 is similar to that of GLN2 in various organs from 6-week-old Arabidopsis. Moreover, the expression of ACR11 and GLN2 is highly co-regulated by sucrose and light/dark treatments in 2-week-old Arabidopsis seedlings. CONCLUSIONS This study reports the identification of four novel ACT domain repeat proteins, ACR9 to ACR12, in Arabidopsis. The ACR11 and ACR12 proteins are localized to the chloroplast, and the expression of ACR11 and GLN2 is highly coordinated. These results suggest that the ACR11 and GLN2 genes may belong to the same functional module. The Arabidopsis ACR11 protein may function as a regulatory protein that is related to glutamine metabolism or signaling in the chloroplast.
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Affiliation(s)
- Tzu-Ying Sung
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Tsui-Yun Chung
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chih-Ping Hsu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Ming-Hsiun Hsieh
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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26
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Litz C, Helfmann S, Gerhardt S, Andrade SLA. Structure of GlnK1, a signalling protein from Archaeoglobus fulgidus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:178-81. [PMID: 21301082 PMCID: PMC3034604 DOI: 10.1107/s1744309110047482] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 11/16/2010] [Indexed: 11/10/2022]
Abstract
GlnB and GlnK are ancient signalling proteins that play a crucial role in the regulation of nitrogen assimilation. Both protein types can be present in the same genome as either single or multiple copies. However, the gene product of glnK is always found in an operon together with an amt gene encoding an ammonium-transport (Amt) protein. Complex formation between GlnK and Amt blocks ammonium uptake and depends on the nitrogen level in the cell, which is regulated through the binding of specific effector molecules to GlnK. In particular, an ammonium shock to a cell culture previously starved in this nitrogen source or the binding of ATP to purified GlnK can stimulate effective complex formation. While the binding of ATP/ADP and 2-oxoglutarate (as a signal for low intracellular nitrogen) to GlnK have been reported and several GlnB/K protein structures are available, essential functional questions remain unanswered. Here, the crystal structure of A. fulgidus GlnK1 at 2.28 Å resolution and a comparison with the crystal structures of other GlnK proteins, in particular with that of its paralogue GlnK2 from the same organism, is reported.
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Affiliation(s)
- Claudia Litz
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Sarah Helfmann
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Stefan Gerhardt
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Susana L. A. Andrade
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
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Shetty ND, Reddy MCM, Palaninathan SK, Owen JL, Sacchettini JC. Crystal structures of the apo and ATP bound Mycobacterium tuberculosis nitrogen regulatory PII protein. Protein Sci 2010; 19:1513-24. [PMID: 20521335 DOI: 10.1002/pro.430] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PII constitutes a family of signal transduction proteins that act as nitrogen sensors in microorganisms and plants. Mycobacterium tuberculosis (Mtb) has a single homologue of PII whose precise role has as yet not been explored. We have solved the crystal structures of the Mtb PII protein in its apo and ATP bound forms to 1.4 and 2.4 A resolutions, respectively. The protein forms a trimeric assembly in the crystal lattice and folds similarly to the other PII family proteins. The Mtb PII:ATP binary complex structure reveals three ATP molecules per trimer, each bound between the base of the T-loop of one subunit and the C-loop of the neighboring subunit. In contrast to the apo structure, at least one subunit of the binary complex structure contains a completely ordered T-loop indicating that ATP binding plays a role in orienting this loop region towards target proteins like the ammonium transporter, AmtB. Arg38 of the T-loop makes direct contact with the gamma-phosphate of the ATP molecule replacing the Mg(2+) position seen in the Methanococcus jannaschii GlnK1 structure. The C-loop of a neighboring subunit encloses the other side of the ATP molecule, placing the GlnK specific C-terminal 3(10) helix in the vicinity. Homology modeling studies with the E. coli GlnK:AmtB complex reveal that Mtb PII could form a complex similar to the complex in E. coli. The structural conservation and operon organization suggests that the Mtb PII gene encodes for a GlnK protein and might play a key role in the nitrogen regulatory pathway.
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Affiliation(s)
- Nishant D Shetty
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-2128, USA
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Mechanism of 2-oxoglutarate signaling by the Synechococcus elongatus PII signal transduction protein. Proc Natl Acad Sci U S A 2010; 107:19760-5. [PMID: 21041661 DOI: 10.1073/pnas.1007653107] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
P(II) proteins control key processes of nitrogen metabolism in bacteria, archaea, and plants in response to the central metabolites ATP, ADP, and 2-oxoglutarate (2-OG), signaling cellular energy and carbon and nitrogen abundance. This metabolic information is integrated by P(II) and transmitted to regulatory targets (key enzymes, transporters, and transcription factors), modulating their activity. In oxygenic phototrophs, the controlling enzyme of arginine synthesis, N-acetyl-glutamate kinase (NAGK), is a major P(II) target, whose activity responds to 2-OG via P(II). Here we show structures of the Synechococcus elongatus P(II) protein in complex with ATP, Mg(2+), and 2-OG, which clarify how 2-OG affects P(II)-NAGK interaction. P(II) trimers with all three sites fully occupied were obtained as well as structures with one or two 2-OG molecules per P(II) trimer. These structures identify the site of 2-OG located in the vicinity between the subunit clefts and the base of the T loop. The 2-OG is bound to a Mg(2+) ion, which is coordinated by three phosphates of ATP, and by ionic interactions with the highly conserved residues K58 and Q39 together with B- and T-loop backbone interactions. These interactions impose a unique T-loop conformation that affects the interactions with the P(II) target. Structures of P(II) trimers with one or two bound 2-OG molecules reveal the basis for anticooperative 2-OG binding and shed light on the intersubunit signaling mechanism by which P(II) senses effectors in a wide range of concentrations.
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29
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Fokina O, Chellamuthu VR, Zeth K, Forchhammer K. A novel signal transduction protein P(II) variant from Synechococcus elongatus PCC 7942 indicates a two-step process for NAGK-P(II) complex formation. J Mol Biol 2010; 399:410-21. [PMID: 20399792 DOI: 10.1016/j.jmb.2010.04.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 03/17/2010] [Accepted: 04/13/2010] [Indexed: 11/15/2022]
Abstract
P(II) signal transduction proteins are highly conserved in bacteria, archaea and plants and have key functions in coordination of central metabolism by integrating signals from the carbon, nitrogen and energy status of the cell. In the cyanobacterium Synechococcus elongatus PCC 7942, P(II) binds ATP and 2-oxoglutarate (2-OG) in a synergistic manner, with the ATP binding sites also accepting ADP. Depending on its effector molecule binding status, P(II) (from this cyanobacterium and other oxygenic phototrophs) complexes and regulates the arginine-controlled enzyme of the cyclic ornithine pathway, N-acetyl-l-glutamate kinase (NAGK), to control arginine biosynthesis. To gain deeper insights into the process of P(II) binding to NAGK, we searched for P(II) variants with altered binding characteristics and found P(II) variants I86N and I86T to be able to bind to an NAGK variant (R233A) that was previously shown to be unable to bind wild-type P(II) protein. Analysis of interactions between these P(II) variants and wild-type NAGK as well as with the NAGK R233A variant suggested that the P(II) I86N variant was a superactive NAGK binder. To reveal the structural basis of this property, we solved the crystal structure of the P(II) I86N variant at atomic resolution. The large T-loop, which prevails in most receptor interactions of P(II) proteins, is present in a tightly bended conformation that mimics the T-loop of S. elongatus P(II) after having latched onto NAGK. Moreover, both P(II) I86 variants display a specific defect in 2-OG binding, implying a role of residue I86 in 2-OG binding. We propose a two-step model for the mechanism of P(II)-NAGK complex formation: in an initiating step, a contact between R233 of NAGK and E85 of P(II) initiates the bending of the extended T-loop of P(II), followed by a second step, where a bended T-loop deeply inserts into the NAGK clefts to form the tight complex.
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Affiliation(s)
- Oleksandra Fokina
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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Amon J, Titgemeyer F, Burkovski A. Common patterns - unique features: nitrogen metabolism and regulation in Gram-positive bacteria. FEMS Microbiol Rev 2010; 34:588-605. [PMID: 20337720 DOI: 10.1111/j.1574-6976.2010.00216.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Gram-positive bacteria have developed elaborate mechanisms to control ammonium assimilation, at the levels of both transcription and enzyme activity. In this review, the common and specific mechanisms of nitrogen assimilation and regulation in Gram-positive bacteria are summarized and compared for the genera Bacillus, Clostridium, Streptomyces, Mycobacterium and Corynebacterium, with emphasis on the high G+C genera. Furthermore, the importance of nitrogen metabolism and control for the pathogenic lifestyle and virulence is discussed. In summary, the regulation of nitrogen metabolism in prokaryotes shows an impressive diversity. Virtually every phylum of bacteria evolved its own strategy to react to the changing conditions of nitrogen supply. Not only do the transcription factors differ between the phyla and sometimes even between families, but the genetic targets of a given regulon can also differ between closely related species.
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Affiliation(s)
- Johannes Amon
- Lehrstuhl für Mikrobiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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31
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NtrC-dependent regulatory network for nitrogen assimilation in Pseudomonas putida. J Bacteriol 2009; 191:6123-35. [PMID: 19648236 DOI: 10.1128/jb.00744-09] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas putida KT2440 is a model strain for studying bacterial biodegradation processes. However, very little is known about nitrogen regulation in this strain. Here, we show that the nitrogen regulatory NtrC proteins from P. putida and Escherichia coli are functionally equivalent and that substitutions leading to partially active forms of enterobacterial NtrC provoke the same phenotypes in P. putida NtrC. P. putida has only a single P(II)-like protein, encoded by glnK, whose expression is nitrogen regulated. Two contiguous NtrC binding sites located upstream of the sigma(N)-dependent glnK promoter have been identified by footprinting analysis. In vitro experiments with purified proteins demonstrated that glnK transcription was directly activated by NtrC and that open complex formation at this promoter required integration host factor. Transcription of genes orthologous to enterobacterial codB, dppA, and ureD genes, whose transcription is dependent on sigma(70) and which are activated by Nac in E. coli, has also been analyzed for P. putida. Whereas dppA does not appear to be regulated by nitrogen via NtrC, the codB and ureD genes have sigma(N)-dependent promoters and their nitrogen regulation was exerted directly by NtrC, thus avoiding the need for Nac, which is missing in this bacterial species. Based upon these results, we propose a simplified nitrogen regulatory network in P. putida (compared to that in enterobacteria), which involves an indirect-feedback autoregulation of glnK using NtrC as an intermediary.
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32
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van Heeswijk WC, Molenaar D, Hoving S, Westerhoff HV. The pivotal regulator GlnB of Escherichia coli is engaged in subtle and context-dependent control. FEBS J 2009; 276:3324-40. [PMID: 19438718 DOI: 10.1111/j.1742-4658.2009.07058.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study tests the purported signal amplification capability of the glutamine synthetase (GS) regulatory cascade in Escherichia coli. Intracellular concentrations of the pivotal regulatory protein GlnB were modulated by varying expression of its gene (glnB). Neither glnB expression nor P(II)* (i.e. the sum of the concentration of the P(II)-like proteins GlnB and GlnK) had control over the steady-state adenylylation level of GS when cells were grown in the presence of ammonia, in which glnK is not activated. Following the removal of ammonia, the response coefficient of the transient deadenylylation rate of GS-AMP was again zero with respect to both glnB expression and P(II)* concentration. This was at wild-type P(II)* levels. A 20% decrease in the P(II)* level resulted in the response coefficients increasing to 1, which was quite significant yet far from expected for zero-order ultrasensitivity. The transient deadenylylation rate of GS-AMP after brief incubation with ammonia was also measured in cells grown in the absence of ammonia. Here, GlnK was present and both glnB expression and P(II)* lacked control throughout. Because at wild-type levels of P(II)*, the molar ratio of P(II)*-trimer/adenylyltransferase-monomer was only slightly above 1, it is suggested that the absence of control by P(II)* is caused by saturation of adenylyltransferase by P(II)*. The difference in the control of deadenylylation by P(II)* under the two different growth conditions indicates that control of signal transduction is adjusted to the growth conditions of the cell. Adjustment of regulation rather than ultrasensitivity may be the function of signal transduction chains such as the GS cascade. We discuss how the subtle interplay between GlnB, its homologue GlnK and the adenylyltransferase may be responsible for the 'redundant', but quantitative, phenotype of GlnB.
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Affiliation(s)
- Wally C van Heeswijk
- Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
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Teixeira PF, Jonsson A, Frank M, Wang H, Nordlund S. Interaction of the signal transduction protein GlnJ with the cellular targets AmtB1, GlnE and GlnD in Rhodospirillum rubrum: dependence on manganese, 2-oxoglutarate and the ADP/ATP ratio. MICROBIOLOGY-SGM 2008; 154:2336-2347. [PMID: 18667566 DOI: 10.1099/mic.0.2008/017533-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The PII family of signal transduction proteins is widespread amongst the three domains of life, and its members have fundamental roles in the general control of nitrogen metabolism. These proteins exert their regulatory role by direct protein-protein interaction with a multitude of cellular targets. The interactions are dependent on the binding of metabolites such as ATP, ADP and 2-oxoglutarate (2-OG), and on whether or not the PII protein is modified. In the photosynthetic nitrogen-fixing bacterium Rhodospirillum rubrum three PII paralogues have been identified and termed GlnB, GlnJ and GlnK. In this report we analysed the interaction of GlnJ with known cellular targets such as the ammonium transporter AmtB1, the adenylyltransferase GlnE and the uridylyltransferase GlnD. Our results show that the interaction of GlnJ with cellular targets is regulated in vitro by the concentrations of manganese and 2-OG and the ADP : ATP ratio. Furthermore, we show here for the first time, to our knowledge, that in the interactions of GlnJ with the three different partners, the energy signal (ADP : ATP ratio) in fact overrides the carbon/nitrogen signal (2-OG). In addition, by generating specific amino acid substitutions in GlnJ we show that the interactions with different cellular targets are differentially affected, and the possible implications of these results are discussed. Our results are important to further the understanding of the regulatory role of PII proteins in R. rubrum, a photosynthetic bacterium in which the nitrogen fixation process and its intricate control mechanisms make the regulation of nitrogen metabolism even more complex than in other studied bacteria.
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Affiliation(s)
- Pedro Filipe Teixeira
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Anders Jonsson
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Martina Frank
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - He Wang
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Stefan Nordlund
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
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34
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Jiang P, Ninfa AJ. Escherichia coli PII signal transduction protein controlling nitrogen assimilation acts as a sensor of adenylate energy charge in vitro. Biochemistry 2007; 46:12979-96. [PMID: 17939683 DOI: 10.1021/bi701062t] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PII signal transduction proteins are among the most widely distributed signaling proteins in nature, controlling nitrogen assimilation in organisms ranging from bacteria to higher plants. PII proteins integrate signals of cellular metabolic status and interact with and regulate receptors that are signal transduction enzymes or key metabolic enzymes. Prior work with Escherichia coli PII showed that all signal transduction functions of PII required ATP binding to PII and that ATP binding was synergistic with the binding of alpha-ketoglutarate to PII. Furthermore, alpha-ketoglutarate, a cellular signal of nitrogen and carbon status, was observed to strongly regulate PII functions. Here, we show that in reconstituted signal transduction systems, ADP had a dramatic effect on PII regulation of two E. coli PII receptors, ATase, and NRII (NtrB), and on PII uridylylation by the signal transducing UTase/UR. ADP acted antagonistically to alpha-ketoglutarate, that is, low adenylylate energy charge acted to diminish signaling of nitrogen limitation. By individually studying the interactions that occur in the reconstituted signal transduction systems, we observed that essentially all PII and PII-UMP interactions were influenced by ADP. Our experiments also suggest that under certain conditions, the three nucleotide binding sites of the PII trimer may be occupied by combinations of ATP and ADP. In the aggregate, our results show that PII proteins, in addition to serving as sensors of alpha-ketoglutarate, have the capacity to serve as direct sensors of the adenylylate energy charge.
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Affiliation(s)
- Peng Jiang
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
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35
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Jonsson A, Teixeira PF, Nordlund S. The activity of adenylyltransferase in Rhodospirillum rubrum is only affected by α-ketoglutarate and unmodified PII proteins, but not by glutamine, in vitro. FEBS J 2007; 274:2449-60. [PMID: 17419734 DOI: 10.1111/j.1742-4658.2007.05778.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Ammonium assimilation is tightly regulated in nitrogen-fixing bacteria; the target of regulation is primarily the activity of the key enzyme glutamine synthetase that is regulated by reversible covalent modification by AMP groups in reactions catalysed by the bifunctional adenylyltransferase (ATase). The properties and regulation of ATase from Escherichia coli have been studied in great detail. We have investigated the regulation of ATase from Rhodospirillum rubrum, a photosynthetic nitrogen-fixing bacterium. In this diazotroph, nitrogenase is regulated at the metabolic level in addition to the transcriptional regulation operating in all diazotrophic bacteria, which makes understanding the regulatory features of nitrogen assimilation even more interesting. We show that in R. rubrum, in contrast to the E. coli system, ATase is primarily regulated by alpha-ketoglutarate and that glutamine has no effect on neither the adenylylation nor the deadenylylation of glutamine synthetase. Furthermore, the role of the regulatory P(II) proteins is only to stimulate the adenylylation reaction, as there is no effect on the reverse reaction. We propose that in R. rubrum and possibly other diazotrophs alpha-ketoglutarate plays the central role in the regulation of ATase and thus glutamine synthetase activity.
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Affiliation(s)
- Anders Jonsson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
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36
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Jonsson A, Nordlund S. In vitro studies of the uridylylation of the three PII protein paralogs from Rhodospirillum rubrum: the transferase activity of R. rubrum GlnD is regulated by alpha-ketoglutarate and divalent cations but not by glutamine. J Bacteriol 2007; 189:3471-8. [PMID: 17337583 PMCID: PMC1855872 DOI: 10.1128/jb.01704-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
P(II) proteins have been shown to be key players in the regulation of nitrogen fixation and ammonia assimilation in bacteria. The mode by which these proteins act as signals is by being in either a form modified by UMP or the unmodified form. The modification, as well as demodification, is catalyzed by a bifunctional enzyme encoded by the glnD gene. The regulation of this enzyme is thus of central importance. In Rhodospirillum rubrum, three P(II) paralogs have been identified. In this study, we have used purified GlnD and P(II) proteins from R. rubrum, and we show that for the uridylylation activity of R. rubrum GlnD, alpha-ketoglutarate is the main signal, whereas glutamine has no effect. This is in contrast to, e.g., the Escherichia coli system. Furthermore, we show that all three P(II) proteins are uridylylated, although the efficiency is dependent on the cation present. This difference may be of importance in understanding the effects of the P(II) proteins on the different target enzymes. Furthermore, we show that the deuridylylation reaction is greatly stimulated by glutamine and that Mn(2+) is required.
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Affiliation(s)
- Anders Jonsson
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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37
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Tøndervik A, Torgersen HR, Botnmark HK, Strøm AR. Transposon mutations in the 5' end of glnD, the gene for a nitrogen regulatory sensor, that suppress the osmosensitive phenotype caused by otsBA lesions in Escherichia coli. J Bacteriol 2006; 188:4218-26. [PMID: 16740928 PMCID: PMC1482954 DOI: 10.1128/jb.00513-05] [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: 11/20/2022] Open
Abstract
GlnD of Escherichia coli is a bifunctional signal-transducing enzyme (102.4 kDa) which uridylylates the allosteric regulatory protein PII and deuridylylates PII-UMP in response to growth with nitrogen excess or limitation, respectively. GlnD catalyzes these reactions in response to high or low levels of cytoplasmic glutamine, respectively, and indirectly directs the expression of nitrogen-regulated genes, e.g., the glnK-amtB operon. We report that chromosomal mini-Tn10 insertions situated after nucleotide number 997 or 1075 of glnD partially suppressed the osmosensitive phenotype of DeltaotsBA or otsA::Tn10 mutations (defective osmoregulatory trehalose synthesis). Strains carrying these glnD::mini-Tn10 mutations either completely repressed the expression of trp::(glnKp-lacZ) or induced this reporter system to nearly 60% of the wild-type glnD level in response to nitrogen availability, an essentially normal response. This was in contrast to the much-studied glnD99::Tn10 mutation, which carries its insertion in the 3' end of the gene, causes a complete repression of glnKp-lacZ expression under all growth conditions, and also confers leaky glutamine auxotrophy. When expressed from the Pm promoter in plasmid constructs, the present glnD mutations produced proteins with an apparent mass of 39 or 42 kDa. These proteins were deduced to comprise 344 or 370 N-terminal residues, respectively, harboring the known nucleotidyltransferase domain of GlnD, plus a common C-terminal addition of 12 residues encoded by IS10. They lacked three other domains of GlnD. Apparently, the transferase domain by itself enabled the cells to catalyze the uridylylation reaction and direct nitrogen-regulated gene expression. Our data indicate that there exists a link between osmotic stress and the nitrogen response.
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Affiliation(s)
- Anne Tøndervik
- The Norwegian University of Science and Technology, Department of Biotechnology, Trondheim N-7491, Norway
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38
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Chen Y, Yang E, Liu Z, Tian Z, Wang Y. The role of CopG mediated DNA bending on the regulation of the σ54-dependent promoters in E. coli. CHINESE SCIENCE BULLETIN-CHINESE 2006. [DOI: 10.1007/s11434-006-0934-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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39
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Fabozzi G, Ascenzi P, Renzi SD, Visca P. Truncated hemoglobin GlbO from Mycobacterium leprae alleviates nitric oxide toxicity. Microb Pathog 2006; 40:211-20. [PMID: 16524692 DOI: 10.1016/j.micpath.2006.01.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Revised: 01/09/2006] [Accepted: 01/16/2006] [Indexed: 11/21/2022]
Abstract
As a consequence of reductive genome evolution, the obligate intracellular pathogen Mycobacterium leprae has minimized the repertoire of genes implicated in defense against reactive oxygen and nitrogen species. Genes for multiple hemoglobin types coexist in mycobacterial genomes, but M. leprae has retained only glbO, encoding a group-II truncated hemoglobin. Mycobacterium tuberculosis GlbO has been involved in oxygen transfer and respiration during hypoxia, but a role in protection from nitric oxide (NO) has not been documented yet. Here, we report that the in vitro reaction of oxygenated recombinant M. leprae GlbO with NO results in an immediate stoichiometric formation of nitrate, concomitant with heme-protein oxidation. Overexpression of GlbO alleviates the growth inhibition of Escherichia colihmp (flavohemoglobin gene) mutants in the presence of NO-donors, partly complementing the defect in Hmp synthesis. A promoter element upstream of glbO was predicted in silico, and confirmed by using a glbO::lacZ transcriptional fusion in the heterologous Mycobacterium smegmatis system. The glbO::lacZ fusion was expressed through the whole growth cycle of M. smegmatis, and moderately induced by NO. We propose that M. leprae, by retaining the unique truncated hemoglobin GlbO, may have coupled O2 delivery to the terminal oxidase with a defensive mechanism to scavenge NO from respiratory enzymes. These activities would help to sustain the obligate aerobic metabolism required for intracellular survival of leprosy bacilli.
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Affiliation(s)
- Giulia Fabozzi
- National Institute for Infectious Diseases IRCCS Lazzaro Spallanzani, Via Portuense 292, I-00149 Rome, Italy
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40
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Kurihara S, Oda S, Kumagai H, Suzuki H. γ-Glutamyl-γ-aminobutyrate hydrolase in the putrescine utilization pathway of Escherichia coli K-12. FEMS Microbiol Lett 2006; 256:318-23. [PMID: 16499623 DOI: 10.1111/j.1574-6968.2006.00137.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
gamma-Glutamyl-gamma-aminobutyrate hydrolase (PuuD) was purified and the properties of the enzyme were characterized. The active center of PuuD was identified as Cys-114 by site-directed mutagenesis. The expression of PuuD was induced by putrescine and O2 (substrates of the Puu pathway), while the addition of succinate or NH4Cl (products of the Puu pathway) to the medium reduced the expression of PuuD. The findings that the puuD-deficient strain accumulated gamma-glutamyl-gamma-aminobutyrate (gamma-Glu-GABA) and could not grow on putrescine as a sole nitrogen source indicate that PuuD is physiologically important as a gamma-Glu-GABA hydrolase.
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Affiliation(s)
- Shin Kurihara
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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41
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Bonatto AC, Souza EM, Pedrosa FO, Yates MG, Benelli EM. Effect of T- and C-loop mutations on the Herbaspirillum seropedicae GlnB protein in nitrogen signalling. Res Microbiol 2005; 156:634-40. [PMID: 15950123 DOI: 10.1016/j.resmic.2005.01.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Revised: 01/19/2005] [Accepted: 01/24/2005] [Indexed: 11/28/2022]
Abstract
Proteins of the PII family are found in species of all kingdoms. Although these proteins usually share high identity, their functions are specific to the different organisms. Comparison of structural data from Escherichia coli GlnB and GlnK and Herbaspirillum seropedicae GlnB showed that the T-loop and C-terminus were variable regions. To evaluate the role of these regions in signal transduction by the H. seropedicae GlnB protein, four mutants were constructed: Y51F, G108A/P109a, G108W and Q3R/T5A. The activities of the native and mutated proteins were assayed in an E. coli background constitutively expressing the Klebsiella pneumoniae nifLA operon. The results suggested that the T-loop and C-terminus regions of H. seropedicae GlnB are involved in nitrogen signal transduction.
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Affiliation(s)
- Ana C Bonatto
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, C. Postal 19046, CEP 81531-990, Curitiba, PR, Brazil
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Kurihara S, Oda S, Kato K, Kim HG, Koyanagi T, Kumagai H, Suzuki H. A novel putrescine utilization pathway involves gamma-glutamylated intermediates of Escherichia coli K-12. J Biol Chem 2004; 280:4602-8. [PMID: 15590624 DOI: 10.1074/jbc.m411114200] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel bacterial putrescine utilization pathway was discovered. Seven genes, the functions of whose products were not known, are involved in this novel pathway. Five of them encode enzymes that catabolize putrescine; one encodes a putrescine importer, and the other encodes a transcriptional regulator. This novel pathway involves six sequential steps as follows: 1) import of putrescine; 2) ATP-dependent gamma-glutamylation of putrescine; 3) oxidization of gamma-glutamylputrescine; 4) dehydrogenation of gamma-glutamyl-gamma-aminobutyraldehyde; 5) hydrolysis of the gamma-glutamyl linkage of gamma-glutamyl-gamma-aminobutyrate; and 6) transamination of gamma-aminobutyrate to form the final product of this pathway, succinate semialdehyde, which is the precursor of succinate.
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Affiliation(s)
- Shin Kurihara
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
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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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Pioszak AA, Ninfa AJ. Mutations altering the N-terminal receiver domain of NRI (NtrC) That prevent dephosphorylation by the NRII-PII complex in Escherichia coli. J Bacteriol 2004; 186:5730-40. [PMID: 15317778 PMCID: PMC516846 DOI: 10.1128/jb.186.17.5730-5740.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The phosphorylated form of NRI is the transcriptional activator of nitrogen-regulated genes in Escherichia coli. NRI approximately P displays a slow autophosphatase activity and is rapidly dephosphorylated by the complex of the NRII and PII signal transduction proteins. Here we describe the isolation of two mutations, causing the alterations DeltaD10 and K104Q in the receiver domain of NRI, that were selected as conferring resistance to dephosphorylation by the NRII-PII complex. The mutations, which alter highly conserved residues near the D54 site of phosphorylation in the NRI receiver domain, resulted in elevated expression of nitrogen-regulated genes under nitrogen-rich conditions. The altered NRI receiver domains were phosphorylated by NRII in vitro but were defective in dephosphorylation. The DeltaD10 receiver domain retained normal autophosphatase activity but was resistant to dephosphorylation by the NRII-PII complex. The K104Q receiver domain lacked both the autophosphatase activity and the ability to be dephosphorylated by the NRII-PII complex. The properties of these altered proteins are consistent with the hypothesis that the NRII-PII complex is not a true phosphatase but rather collaborates with NRI approximately P to bring about its dephosphorylation.
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Affiliation(s)
- Augen A Pioszak
- Department of Biological Chemistry, University of Michigan Medical School, 1301 E. Catherine, Ann Arbor, MI 48109-0606, USA
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Abstract
Nitrogen limitation in Escherichia coli controls the expression of about 100 genes of the nitrogen regulated (Ntr) response, including the ammonia-assimilating glutamine synthetase. Low intracellular glutamine controls the Ntr response through several regulators, whose activities are modulated by a variety of metabolites. Ntr proteins assimilate ammonia, scavenge nitrogen-containing compounds, and appear to integrate ammonia assimilation with other aspects of metabolism, such as polyamine metabolism and glutamate synthesis. The leucine-responsive regulatory protein (Lrp) controls the synthesis of glutamate synthase, which controls the Ntr response, presumably through its effect on intracellular glutamine. Some Ntr proteins inhibit the expression of some Lrp-activated genes. Guanosine tetraphosphate appears to control Lrp synthesis. In summary, a network of interacting global regulators that senses different aspects of metabolism integrates nitrogen assimilation with other metabolic processes.
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Affiliation(s)
- Larry Reitzer
- Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson, Texas 75080-0688, USA.
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Burkovski A. Ammonium assimilation and nitrogen control in Corynebacterium glutamicum and its relatives: an example for new regulatory mechanisms in actinomycetes. FEMS Microbiol Rev 2004; 27:617-28. [PMID: 14638415 DOI: 10.1016/s0168-6445(03)00067-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Nitrogen is an essential component of nearly all complex macromolecules in a bacterial cell, such as proteins, nucleic acids and cell wall components. Accordingly, most prokaryotes have developed elaborate control mechanisms to provide an optimal supply of nitrogen for cellular metabolism and to cope with situations of nitrogen limitation. In this review, recent advances in our knowledge of ammonium uptake, its assimilation, and related regulatory systems in Corynebacterium glutamicum, a Gram-positive soil bacterium used for the industrial production of amino acids, are summarized and discussed with respect to the situation in the bacterial model organisms, Escherichia coli and Bacillus subtilis, and in comparison to the situation in other actinomycetes, namely in mycobacteria and streptomycetes. The regulatory network of nitrogen control in C. glutamicum seems to be a patchwork of different elements. It includes proteins similar to the UTase/GlnK pathway of E. coli and expression regulation by a repressor protein as in B. subtilis, but it lacks an NtrB/NtrC two-component signal transduction system. Furthermore, the C. glutamicum regulation network has unique features, such as a new sensing mechanism. Based on its extremely well-investigated central metabolism, well-established molecular biology tools, a public genome sequence and a newly-established proteome project, C. glutamicum seems to be a suitable model organism for other corynebacteria, such as Corynebacterium diphtheriae and Corynebacterium efficiens.
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Affiliation(s)
- Andreas Burkovski
- Institut für Biochemie der Universität zu Köln, Zülpicher-Strasse 47, 50674 Cologne, Germany.
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Maheswaran M, Forchhammer K. Carbon-source-dependent nitrogen regulation in Escherichia coli is mediated through glutamine-dependent GlnB signalling. MICROBIOLOGY (READING, ENGLAND) 2003; 149:2163-2172. [PMID: 12904556 DOI: 10.1099/mic.0.26449-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The P(II) signal transduction proteins GlnB and GlnK are uridylylated/deuridylylated in response to the intracellular glutamine level, the primary signal of the cellular nitrogen status. Furthermore, GlnB was shown to be allosterically regulated by 2-oxoglutarate, and thus GlnB was suggested to integrate signals of the cellular carbon and nitrogen status. Receptors of GlnB signal transduction in Escherichia coli are the NtrB/NtrC two-component system and GlnE, an enzyme which adenylylates/deadenylylates glutamine synthetase. In this study, the authors investigated the effect of different carbon sources on the expression of the NtrC-dependent genes glnA and glnK and on the uridylylation status of GlnB and GlnK. With glutamine as nitrogen source, high levels of glnA and glnK expression were obtained when glucose was used as carbon source, but expression was strongly decreased when the cells were grown with poor carbon sources or when cAMP was present. This response correlated with the uridylylation status of GlnB, suggesting that the carbon/cAMP effect was mediated through GlnB uridylylation, a conclusion that was confirmed by mutants of the P(II) signalling pathway. When glutamine was replaced by low concentrations of ammonium as nitrogen source, neither glnAglnK expression nor GlnB uridylylation responded to the carbon source or to cAMP. Furthermore, glutamine synthetase could be rapidly adenylylated in vivo by the external addition of glutamine; however, this occurred only when cells were grown in the presence of cAMP, not in its absence. Together, these results suggest that poor carbon sources, through cAMP signalling, favour glutamine uptake. The cellular glutamine signal is then transduced by uridylyltransferase and GlnB to modulate NtrC-dependent gene expression.
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Affiliation(s)
- Mani Maheswaran
- Institut für Mikrobiologie und Molekularbiologie der Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
| | - Karl Forchhammer
- Institut für Mikrobiologie und Molekularbiologie der Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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Abstract
Escherichia coli AmtB is a member of the MEP/Amt family of ammonia transporters found in archaea, eubacteria, fungi, plants and animals. In prokaryotes, AmtB homologues are co-transcribed with a PII paralogue, GlnK, in response to nitrogen limitation. Here, we show that AmtB antagonizes PII signalling through NRII and that co-expression of GlnK with AmtB overcomes this antagonism. In cells lacking GlnK, expression of AmtB during nitrogen starvation prevented deinduction of Ntr gene expression when a nitrogen source became available. The absence of AmtB in cells lacking GlnK allowed rapid reduction of Ntr gene expression during this transition, indicating that one function of GlnK is to prevent AmtB-mediated antagonism of PII signalling after nitrogen starvation. Other roles of GlnK in controlling Ntr gene expression and maintaining viability during nitrogen starvation were unaffected by AmtB. Expression of AmtB from a constitutive promoter under nitrogen-rich conditions induced full expression of glnALG and elevated expression of glnK in wild-type and glnK cells; thus, the ability of AmtB to raise Ntr gene expression did not require a factor found only in nitrogen-starved cells. Experiments with intact cells showed that AmtB acted downstream of a uridylyl transferase uridylyl-removing enzyme (UTase/UR) and upstream of NRII, suggesting that the target was PII. AmtB also slowed the deuridylylation of PII approximately UMP upon ammonia addition, showing that multiple PII interactions were affected by AmtB. Our data are consistent with a hypothesis that AmtB interacts with PII and GlnK, and that co-transcription of glnK and amtB prevents titration of PII when AmtB is highly expressed.
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Affiliation(s)
- Timothy A Blauwkamp
- Department of Biological Chemistry, University of Michigan Medical School, 1301 E Catherine, Ann Arbor, MI 48109-0606, USA
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Pioszak AA, Ninfa AJ. Genetic and biochemical analysis of phosphatase activity of Escherichia coli NRII (NtrB) and its regulation by the PII signal transduction protein. J Bacteriol 2003; 185:1299-315. [PMID: 12562801 PMCID: PMC142841 DOI: 10.1128/jb.185.4.1299-1315.2003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutant forms of Escherichia coli NRII (NtrB) were isolated that retained wild-type NRII kinase activity but were defective in the PII-activated phosphatase activity of NRII. Mutant strains were selected as mimicking the phenotype of a strain (strain BK) that lacks both of the related PII and GlnK signal transduction proteins and thus has no mechanism for activation of the NRII phosphatase activity. The selection and screening procedure resulted in the isolation of numerous mutants that phenotypically resembled strain BK to various extents. Mutations mapped to the glnL (ntrB) gene encoding NRII and were obtained in all three domains of NRII. Two distinct regions of the C-terminal, ATP-binding domain were identified by clusters of mutations. One cluster, including the Y302N mutation, altered a lid that sits over the ATP-binding site of NRII. The other cluster, including the S227R mutation, defined a small surface on the "back" or opposite side of this domain. The S227R and Y302N proteins were purified, along with the A129T (NRII2302) protein, which has reduced phosphatase activity due to a mutation in the central domain of NRII, and the L16R protein, which has a mutation in the N-terminal domain of NRII. The S227R, Y302N, and L16R proteins were specifically defective in the PII-activated phosphatase activity of NRII. Wild-type NRII, Y302N, A129T, and L16R proteins bound to PII, while the S227R protein was defective in binding PII. This suggests that the PII-binding site maps to the "back" of the C-terminal domain and that mutation of the ATP-lid, central domain, and N-terminal domain altered functions necessary for the phosphatase activity after PII binding.
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Affiliation(s)
- Augen A Pioszak
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA
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Burkovski A. I do it my way: Regulation of ammonium uptake and ammonium assimilation in Corynebacterium glutamicum. Arch Microbiol 2003; 179:83-8. [PMID: 12560985 DOI: 10.1007/s00203-002-0505-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2002] [Revised: 11/11/2002] [Accepted: 11/16/2002] [Indexed: 02/28/2023]
Abstract
In order to utilize different nitrogen sources and to survive situations of nitrogen limitation, microorganisms have developed several mechanisms to adapt their metabolism to changes in the nitrogen supply. In this communication, recent advances in our knowledge of ammonium uptake, its assimilation, and connected regulatory systems in Corynebacterium glutamicum are discussed with respect to the situation in the bacterial model organisms Escherichia coli and Bacillus subtilis. The regulatory network of nitrogen control in C. glutamicum differs substantially from that in these bacteria, for example, by the presence of AmtR, the unique "master regulator" of nitrogen control, the absence of a NtrB/NtrC two-component signal transduction system, and a different sensing mechanism in C. glutamicum.
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Affiliation(s)
- Andreas Burkovski
- Institut für Biochemie der Universität zu Köln, Zülpicher-Strasse 47, 50674, Köln, Germany.
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