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Xu Z, Wu G, Wang B, Zhao Y, Liu F. TrpR-Like Protein PXO_00831, Regulated by the Sigma Factor RpoD, Is Involved in Motility, Oxidative Stress Tolerance, and Virulence in Xanthomonas oryzae pv. oryzae. PHYTOPATHOLOGY 2023; 113:170-182. [PMID: 36095334 DOI: 10.1094/phyto-05-22-0165-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Xanthomonas oryzae pv. oryzae (Xoo) is a Gram-negative bacterium that causes bacterial leaf blight in rice. In this study, we identified a putative TrpR-like protein, PXO_TrpR (PXO_00831), in Xoo. This protein contains a tryptophan (Trp) repressor domain and is highly conserved in Xanthomonas. Auxotrophic assays and RT-qPCR confirmed that PXO_TrpR acts as a Trp repressor, negatively regulating the expression of Trp biosynthesis genes. Pathogenicity tests showed that PXO_trpR knockout in Xoo significantly reduced lesion development and disease symptoms in the leaves of susceptible rice. RNA-seq analysis and phenotypic tests revealed that the PXO_trpR mutant exhibited impaired cell motility and was more sensitive to H2O2 oxidative stress than the wild-type strain. Furthermore, we found that the sigma 70 factor RpoD controlled the transcription of PXO_trpR by directly binding to its promoter region. This study demonstrates the biological function and transcriptional mechanism of PXO_TrpR as a Trp repressor in Xoo and evaluates its novel pathogenic roles by regulating flagellar motility and the oxidative stress response.
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Affiliation(s)
- Zhizhou Xu
- Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Guichun Wu
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu 210014, China
- National Engineering Laboratory of Crop Stress Resistance Breeding, School of Life Sciences, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Bo Wang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu 210014, China
| | - Yancun Zhao
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu 210014, China
| | - Fengquan Liu
- Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu 210014, China
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2
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Gong X, Zhang R, Wang J, Yan Y. Engineering of a TrpR-Based Biosensor for Altered Dynamic Range and Ligand Preference. ACS Synth Biol 2022; 11:2175-2183. [PMID: 35594503 PMCID: PMC10947557 DOI: 10.1021/acssynbio.2c00134] [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] [Indexed: 11/28/2022]
Abstract
Transcriptional factors play a crucial role in regulating cellular functions. Understanding and altering the dynamic behavior of the transcriptional factor-based biosensors will expand our knowledge in investigating biomolecular interactions and facilitating biosynthetic applications. In this study, we characterized and engineered a TrpR-based tryptophan repressor system in Escherichia coli. We found that the reconstructed TrpR1-PtrpO1 biosensor system exhibited low basal expression and narrow dynamic range in the presence of tryptophan or its analogue 5-hydroxytryptophan (5-HTP). Given the application potential of the biosensor, we introduced engineering approaches in multiple levels to optimize its dynamic behavior. First, the I57 and V58 residues in the ligand-binding pocket were rationally mutated in search of variants with altered ligand specificity. Two TrpR1 variants, V58E and V58K, successfully acquired ligand preference toward tryptophan and 5-HTP, respectively. The biosensor-induced expression levels were increased up to 10-fold with those variants. Furthermore, to pursue broader operational range, we tuned the regulator-operator binding affinity by mutating the binding box of TrpR1. Collectively, we demonstrated that the biosynthesis-significant biosensor TrpR1-PtrpO1 can be engineered to acquire extended dynamic ranges and improved ligand preference. The engineered biosensor variants with remarkable dynamic behavior can serve as key genetic elements in high-throughput screening and dynamic regulation in biosynthetic scenarios.
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Affiliation(s)
- Xinyu Gong
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Ruihua Zhang
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Jian Wang
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Yajun Yan
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
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Verma BK, Mannan AA, Zhang F, Oyarzún DA. Trade-Offs in Biosensor Optimization for Dynamic Pathway Engineering. ACS Synth Biol 2022; 11:228-240. [PMID: 34968029 DOI: 10.1021/acssynbio.1c00391] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent progress in synthetic biology allows the construction of dynamic control circuits for metabolic engineering. This technology promises to overcome many challenges encountered in traditional pathway engineering, thanks to its ability to self-regulate gene expression in response to bioreactor perturbations. The central components in these control circuits are metabolite biosensors that read out pathway signals and actuate enzyme expression. However, the construction of metabolite biosensors is a major bottleneck for strain design, and a key challenge is to understand the relation between biosensor dose-response curves and pathway performance. Here we employ multiobjective optimization to quantify performance trade-offs that arise in the design of metabolite biosensors. Our approach reveals strategies for tuning dose-response curves along an optimal trade-off between production flux and the cost of an increased expression burden on the host. We explore properties of control architectures built in the literature and identify their advantages and caveats in terms of performance and robustness to growth conditions and leaky promoters. We demonstrate the optimality of a control circuit for glucaric acid production in Escherichia coli, which has been shown to increase the titer by 2.5-fold as compared to static designs. Our results lay the groundwork for the automated design of control circuits for pathway engineering, with applications in the food, energy, and pharmaceutical sectors.
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Affiliation(s)
- Babita K. Verma
- School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, U.K
| | - Ahmad A. Mannan
- Warwick Integrative Synthetic Biology Centre, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K
| | - Fuzhong Zhang
- Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Diego A. Oyarzún
- School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, U.K
- School of Informatics, The University of Edinburgh, Edinburgh EH8 9AB, U.K
- The Alan Turing Institute, London, NW1 2DB, U.K
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Howitz N, Su T, Lazazzera BA. Meta-Tyrosine Induces Cytotoxic Misregulation of Metabolism in Escherichia coli. J Mol Biol 2020; 432:166716. [PMID: 33220263 DOI: 10.1016/j.jmb.2020.11.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 11/09/2020] [Accepted: 11/12/2020] [Indexed: 12/16/2022]
Abstract
The non-protein amino acid meta-Tyrosine (m-Tyr) is produced in cells under conditions of oxidative stress, and m-Tyr has been shown to be toxic to a broad range of biological systems. However, the mechanism by which m-Tyr damages cells is unclear. In E. coli, the quality control (QC) function of phenyalanyl-tRNA synthetase (PheRS) is required for resistantce to m-Tyr. To determine the mechanism of m-Tyr toxicity, we utilitized a strain of E. coli that expresses a QC-defective PheRS. The global responses of E. coli cells to m-Tyr were assessed by RNA-seq, and >500 genes were differentially expressed after the addition of m-Tyr. The most strongly up-regulated genes are involved in unfolded-protein stress response, and cells exposed to m-Tyr contained large, electron-dense protein aggregates, indicating that m-Tyr destabilized a large fraction of the proteome. Additionally, we observed that amino acid biosynthesis and transport regulons, controlled by ArgR, TrpR, and TyrR, and the stringent-response regulon, controlled by DksA/ppGpp, were differentially expressed. m-Tyr resistant mutants were isolated and found to have altered a promoter to increase expression of the enzymes for Phe production or to have altered transporters, which likely result in less uptake or increased efflux of m-Tyr. These findings indicate that when m-Tyr has passed the QC checkpoint by the PheRS, this toxicity of m-Tyr may result from interfering with amino acid metabolism, destabalizing a large number of proteins, and the formation of protein aggregates.
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Affiliation(s)
- Nathaniel Howitz
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Trent Su
- Department of Biological Chemistry, University of California, Los Angeles, CA 90095, USA; Institute for Quantitative and Computational Biology, University of California, Los Angeles, CA 90095, USA
| | - Beth A Lazazzera
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
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Cao M, Gao M, Suástegui M, Mei Y, Shao Z. Building microbial factories for the production of aromatic amino acid pathway derivatives: From commodity chemicals to plant-sourced natural products. Metab Eng 2020; 58:94-132. [DOI: 10.1016/j.ymben.2019.08.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 08/03/2019] [Accepted: 08/07/2019] [Indexed: 01/23/2023]
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Kawai S, Kawamoto J, Ogawa T, Kurihara T. Development of a regulatable low-temperature protein expression system using the psychrotrophic bacterium, Shewanella livingstonensis Ac10, as the host. Biosci Biotechnol Biochem 2019; 83:2153-2162. [PMID: 31291825 DOI: 10.1080/09168451.2019.1638754] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A low-temperature protein expression system is useful for the production of thermolabile proteins. We previously developed a system that enables constitutive protein production at low temperatures, using the psychrotrophic bacterium Shewanella livingstonensis Ac10 as the host. To increase the utility of this system, in the present study, we introduced a repressible promoter of the trp operon of this bacterium into the system. When ß-lactamase was produced under the control of this promoter at 18°C and 4°C, the yields were 75 and 33 mg/L-culture, respectively, in the absence of L-Trp, and the yields were decreased by 72% and 77%, respectively, in the presence of L-Trp. We also found that 3-indoleacrylic acid, a competitive inhibitor of the Escherichia coli trp repressor, increased the expression of the reporter gene. This repressible gene expression system would be useful for regulatable recombinant protein production at low temperatures.
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Affiliation(s)
- Soichiro Kawai
- Laboratory of Molecular Microbial Science, Institute for Chemical Research, Kyoto University , Kyoto , Japan
| | - Jun Kawamoto
- Laboratory of Molecular Microbial Science, Institute for Chemical Research, Kyoto University , Kyoto , Japan
| | - Takuya Ogawa
- Laboratory of Molecular Microbial Science, Institute for Chemical Research, Kyoto University , Kyoto , Japan
| | - Tatsuo Kurihara
- Laboratory of Molecular Microbial Science, Institute for Chemical Research, Kyoto University , Kyoto , Japan
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D'Ambrosio V, Jensen MK. Lighting up yeast cell factories by transcription factor-based biosensors. FEMS Yeast Res 2018; 17:4157790. [PMID: 28961766 PMCID: PMC5812511 DOI: 10.1093/femsyr/fox076] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 09/12/2017] [Indexed: 12/17/2022] Open
Abstract
Our ability to rewire cellular metabolism for the sustainable production of chemicals, fuels and therapeutics based on microbial cell factories has advanced rapidly during the last two decades. Especially the speed and precision by which microbial genomes can be engineered now allow for more advanced designs to be implemented and tested. However, compared to the methods developed for engineering cell factories, the methods developed for testing the performance of newly engineered cell factories in high throughput are lagging far behind, which consequently impacts the overall biomanufacturing process. For this purpose, there is a need to develop new techniques for screening and selection of best-performing cell factory designs in multiplex. Here we review the current status of the sourcing, design and engineering of biosensors derived from allosterically regulated transcription factors applied to the biotechnology work-horse budding yeast Saccharomyces cerevisiae. We conclude by providing a perspective on the most important challenges and opportunities lying ahead in order to harness the full potential of biosensor development for increasing both the throughput of cell factory development and robustness of overall bioprocesses.
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Affiliation(s)
- Vasil D'Ambrosio
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Michael K Jensen
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
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Leyn SA, Suvorova IA, Kazakov AE, Ravcheev DA, Stepanova VV, Novichkov PS, Rodionov DA. Comparative genomics and evolution of transcriptional regulons in Proteobacteria. Microb Genom 2016; 2:e000061. [PMID: 28348857 PMCID: PMC5343134 DOI: 10.1099/mgen.0.000061] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 04/14/2016] [Indexed: 12/16/2022] Open
Abstract
Comparative genomics approaches are broadly used for analysis of transcriptional regulation in bacterial genomes. In this work, we identified binding sites and reconstructed regulons for 33 orthologous groups of transcription factors (TFs) in 196 reference genomes from 21 taxonomic groups of Proteobacteria. Overall, we predict over 10 600 TF binding sites and identified more than 15 600 target genes for 1896 TFs constituting the studied orthologous groups of regulators. These include a set of orthologues for 21 metabolism-associated TFs from Escherichia coli and/or Shewanella that are conserved in five or more taxonomic groups and several additional TFs that represent non-orthologous substitutions of the metabolic regulators in some lineages of Proteobacteria. By comparing gene contents of the reconstructed regulons, we identified the core, taxonomy-specific and genome-specific TF regulon members and classified them by their metabolic functions. Detailed analysis of ArgR, TyrR, TrpR, HutC, HypR and other amino-acid-specific regulons demonstrated remarkable differences in regulatory strategies used by various lineages of Proteobacteria. The obtained genomic collection of in silico reconstructed TF regulons contains a large number of new regulatory interactions that await future experimental validation. The collection provides a framework for future evolutionary studies of transcriptional regulatory networks in Bacteria. It can be also used for functional annotation of putative metabolic transporters and enzymes that are abundant in the reconstructed regulons.
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Affiliation(s)
- Semen A Leyn
- 1A. A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
| | - Inna A Suvorova
- 1A. A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
| | - Alexey E Kazakov
- 2Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | | | - Vita V Stepanova
- 1A. A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
| | | | - Dmitry A Rodionov
- 4Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.,1A. A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
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Zhao G, Hu T, Li J, Wei H, Shang H, Guan Y. A novel strategy to analyze L-tryptophan through allosteric Trp repressor based on rolling circle amplification. Biosens Bioelectron 2015; 71:103-107. [PMID: 25889351 DOI: 10.1016/j.bios.2015.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/25/2015] [Accepted: 04/05/2015] [Indexed: 10/23/2022]
Abstract
Rolling circle amplification (RCA) has been considered as a powerful tool for nucleic acids detection. Here, a novel repressor-RCA-based method for L-tryptophan (L-Trp) detection was developed. This method utilizes the specific interaction between the RCA circular template and the Trp repressor protein (TrpR) involved in trp operon of Escherichia coli (E. coli). In the absence of L-Trp, the TrpR protein could not bind to the RCA template, and the RCA process can be continued. When L-Trp is present, the activated TrpR will bind to the operon sequence on the RCA template and inhibit the RCA reaction. Thus, the concentration of L-Trp is correlated directly with the fluorescent RCA signals. We succeeded in detecting L-Trp in a single step in simple homogeneous reaction system. The detection limit was estimated to be 0.77 μM (S/N=3) with good linearity. The method can unambiguously distinguish L-Trp from other 19 standard amino acids and L-Trp analogs. This strategy is also promising for detecting many small molecules such as other amino acids and carbohydrates.
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Affiliation(s)
- Guojie Zhao
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning 110001, China
| | - Tianyu Hu
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning 110001, China
| | - Jun Li
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning 110001, China
| | - Hua Wei
- Animal Science and Veterinary Medicine College, Shenyang Agricultural University, Shenyang, Liaoning 110866, China
| | - Hong Shang
- Department of Clinical Diagnosis, the First Affiliated Hospital, China Medical University, Shenyang, Liaoning 110001, China
| | - Yifu Guan
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, Liaoning 110001, China.
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Salazar-Cavazos E, Santillán M. Optimal performance of the tryptophan operon of E. coli: a stochastic, dynamical, mathematical-modeling approach. Bull Math Biol 2013; 76:314-34. [PMID: 24307084 DOI: 10.1007/s11538-013-9920-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 11/07/2013] [Indexed: 10/25/2022]
Abstract
In this work, we develop a detailed, stochastic, dynamical model for the tryptophan operon of E. coli, and estimate all of the model parameters from reported experimental data. We further employ the model to study the system performance, considering the amount of biochemical noise in the trp level, the system rise time after a nutritional shift, and the amount of repressor molecules necessary to maintain an adequate level of repression, as indicators of the system performance regime. We demonstrate that the level of cooperativity between repressor molecules bound to the first two operators in the trp promoter affects all of the above enlisted performance characteristics. Moreover, the cooperativity level found in the wild-type bacterial strain optimizes a cost-benefit function involving low biochemical noise in the tryptophan level, short rise time after a nutritional shift, and low number of regulatory molecules.
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11
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Interactions of sulfur oxidation repressor with its promoters involve different binding geometries. Arch Microbiol 2012; 194:737-47. [DOI: 10.1007/s00203-012-0808-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 02/15/2012] [Accepted: 03/15/2012] [Indexed: 12/27/2022]
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12
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Cho BK, Federowicz S, Park YS, Zengler K, Palsson BØ. Deciphering the transcriptional regulatory logic of amino acid metabolism. Nat Chem Biol 2011; 8:65-71. [PMID: 22082910 DOI: 10.1038/nchembio.710] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 08/27/2011] [Indexed: 11/09/2022]
Abstract
Although metabolic networks have been reconstructed on a genome scale, the corresponding reconstruction and integration of governing transcriptional regulatory networks has not been fully achieved. Here we reconstruct such an integrated network for amino acid metabolism in Escherichia coli. Analysis of ChIP-chip and gene expression data for the transcription factors ArgR, Lrp and TrpR showed that 19 out of 20 amino acid biosynthetic pathways are either directly or indirectly controlled by these regulators. Classifying the regulated genes into three functional categories of transport, biosynthesis and metabolism leads to the elucidation of regulatory motifs that constitute the integrated network's basic building blocks. The regulatory logic of these motifs was determined on the basis of relationships between transcription factor binding and changes in the amount of transcript in response to exogenous amino acids. Remarkably, the resulting logic shows how amino acids are differentiated as signaling and nutrient molecules, revealing the overarching regulatory principles of the amino acid stimulon.
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Affiliation(s)
- Byung-Kwan Cho
- Department of Bioengineering, University of California at San Diego, La Jolla, California, USA.
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13
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Abstract
CodY is a global transcriptional regulator that is activated by branched-chain amino acids. A palindromic 15-bp sequence motif, AATTTTCNGAAAATT, is associated with CodY DNA binding. A gel mobility shift assay was used to examine the effect of pH on the binding of Bacillus subtilis CodY to the hutPp and ureAp(3) promoters. CodY at pH 6.0 has higher affinity for DNA, more enhanced activation by isoleucine, and a lower propensity for nonspecific DNA binding than CodY at pH 8.0. DNase I footprinting was used to identify the CodY-protected regions in the hutPp and ureAp(3) promoters. The CodY-protected sequences for both promoters were found to contain multiple copies of the 15-bp motif with 6-bp overlaps. Mutational analysis of the hutPp regulatory region revealed that two overlapping sequence motifs were required for CodY-mediated regulation. The presence of overlapping sequence motifs in the regulatory regions of many B. subtilis CodY-regulated genes suggests that CodY binds to native operators that contain overlapping binding sites.
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Drepper T, Krauss U, Meyer zu Berstenhorst S, Pietruszka J, Jaeger KE. Lights on and action! Controlling microbial gene expression by light. Appl Microbiol Biotechnol 2011; 90:23-40. [PMID: 21336931 DOI: 10.1007/s00253-011-3141-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 01/05/2011] [Accepted: 01/05/2011] [Indexed: 01/10/2023]
Abstract
Light-mediated control of gene expression and thus of any protein function and metabolic process in living microbes is a rapidly developing field of research in the areas of functional genomics, systems biology, and biotechnology. The unique physical properties of the environmental factor light allow for an independent photocontrol of various microbial processes in a noninvasive and spatiotemporal fashion. This mini review describes recently developed strategies to generate photo-sensitive expression systems in bacteria and yeast. Naturally occurring and artificial photoswitches consisting of light-sensitive input domains derived from different photoreceptors and regulatory output domains are presented and individual properties of light-controlled expression systems are discussed.
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Affiliation(s)
- Thomas Drepper
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Düsseldorf, Forschungszentrum Jülich, Stetternicher Forst, 52426, Jülich, Germany.
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15
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Cycling expression and cooperative operator interaction in the trp operon of Escherichia coli. J Theor Biol 2009; 263:340-52. [PMID: 20004672 DOI: 10.1016/j.jtbi.2009.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 12/01/2009] [Accepted: 12/02/2009] [Indexed: 01/12/2023]
Abstract
Oscillatory behaviour in the tryptophan operon of an Escherichia coli mutant strain lacking the enzyme-inhibition regulatory mechanism has been observed by Bliss et al. but not confirmed by others. This behaviour could be important from the standpoint of synthetic biology, whose goals include the engineering of intracellular genetic oscillators. This work is devoted to investigating, from a mathematical modelling point of view, the possibility that the trp operon of the E. coli inhibition-free strain expresses cyclically. For that we extend a previously introduced model for the regulatory pathway of the tryptophan operon in Escherichia coli to account for the observed multiplicity and cooperativity of repressor binding sites. Thereafter we investigate the model dynamics using deterministic numeric solutions, stochastic simulations, and analytic studies. Our results suggest that a quasi-periodic behaviour could be observed in the trp operon expression level of single bacteria.
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Abstract
This chapter describes in detail the genes and proteins of Escherichia coli involved in the biosynthesis and transport of the three aromatic amino acids tyrosine, phenylalanine, and tryptophan. It provides a historical perspective on the elaboration of the various reactions of the common pathway converting erythrose-4-phosphate and phosphoenolpyruvate to chorismate and those of the three terminal pathways converting chorismate to phenylalanine, tyrosine, and tryptophan. The regulation of key reactions by feedback inhibition, attenuation, repression, and activation are also discussed. Two regulatory proteins, TrpR (108 amino acids) and TyrR (513 amino acids), play a major role in transcriptional regulation. The TrpR protein functions only as a dimer which, in the presence of tryptophan, represses the expression of trp operon plus four other genes (the TrpR regulon). The TyrR protein, which can function both as a dimer and as a hexamer, regulates the expression of nine genes constituting the TyrR regulon. TyrR can bind each of the three aromatic amino acids and ATP and under their influence can act as a repressor or activator of gene expression. The various domains of this protein involved in binding the aromatic amino acids and ATP, recognizing DNA binding sites, interacting with the alpha subunit of RNA polymerase, and changing from a monomer to a dimer or a hexamer are all described. There is also an analysis of the various strategies which allow TyrR in conjunction with particular amino acids to differentially affect the expression of individual genes of the TyrR regulon.
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17
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Tabaka M, Cybulski O, Hołyst R. Accurate Genetic Switch in Escherichia coli: Novel Mechanism of Regulation by Co-repressor. J Mol Biol 2008; 377:1002-14. [DOI: 10.1016/j.jmb.2008.01.060] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2007] [Revised: 12/27/2007] [Accepted: 01/15/2008] [Indexed: 11/24/2022]
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18
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Hermsen R, Tans S, ten Wolde PR. Transcriptional regulation by competing transcription factor modules. PLoS Comput Biol 2006; 2:e164. [PMID: 17140283 PMCID: PMC1676028 DOI: 10.1371/journal.pcbi.0020164] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 10/23/2006] [Indexed: 11/19/2022] Open
Abstract
Gene regulatory networks lie at the heart of cellular computation. In these networks, intracellular and extracellular signals are integrated by transcription factors, which control the expression of transcription units by binding to cis-regulatory regions on the DNA. The designs of both eukaryotic and prokaryotic cis-regulatory regions are usually highly complex. They frequently consist of both repetitive and overlapping transcription factor binding sites. To unravel the design principles of these promoter architectures, we have designed in silico prokaryotic transcriptional logic gates with predefined input-output relations using an evolutionary algorithm. The resulting cis-regulatory designs are often composed of modules that consist of tandem arrays of binding sites to which the transcription factors bind cooperatively. Moreover, these modules often overlap with each other, leading to competition between them. Our analysis thus identifies a new signal integration motif that is based upon the interplay between intramodular cooperativity and intermodular competition. We show that this signal integration mechanism drastically enhances the capacity of cis-regulatory domains to integrate signals. Our results provide a possible explanation for the complexity of promoter architectures and could be used for the rational design of synthetic gene circuits.
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Affiliation(s)
- Rutger Hermsen
- FOM Institute for Atomic and Molecular Physics, Amsterdam, The Netherlands
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Akers JC, Tan M. Molecular mechanism of tryptophan-dependent transcriptional regulation in Chlamydia trachomatis. J Bacteriol 2006; 188:4236-43. [PMID: 16740930 PMCID: PMC1482941 DOI: 10.1128/jb.01660-05] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tryptophan is an essential amino acid that is required for normal development in Chlamydia species, and tryptophan metabolism has been implicated in chlamydial persistence and tissue tropism. The ability to synthesize tryptophan is not universal among the Chlamydiaceae, but species that have a predicted tryptophan biosynthetic pathway also encode an ortholog of TrpR, a regulator of tryptophan metabolism in many gram-negative bacteria. We show that in Chlamydia trachomatis serovar D, TrpR regulates its own gene and trpB and trpA, the genes for the two subunits of tryptophan synthase. These three genes form an operon that is transcribed by the major form of chlamydial RNA polymerase. TrpR acts as a tryptophan-dependent aporepressor that binds specifically to operator sequences upstream of the trpRBA operon. We also found that TrpR repressed in vitro transcription of trpRBA in a promoter-specific manner, and the level of repression was dependent upon the concentrations of TrpR and tryptophan. Our findings provide a mechanism for chlamydiae to sense changes in tryptophan levels and to respond by modulating expression of the tryptophan biosynthesis genes, and we present a unified model that shows how C. trachomatis can combine transcriptional repression and attenuation to regulate intrachlamydial tryptophan levels. In the face of host defense mechanisms that limit tryptophan availability from the infected cell, the ability to maintain homeostatic control of intrachlamydial tryptophan levels is likely to play an important role in chlamydial pathogenesis.
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Affiliation(s)
- Johnny C Akers
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
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Wibowo FR, Rauch C, Trieb M, Wellenzohn B, Liedl KR. Water-mediated contacts in thetrp-repressor operator complex recognition process. Biopolymers 2004; 73:668-81. [PMID: 15048770 DOI: 10.1002/bip.20023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Water-mediated contacts are known as an important recognition tool in trp-repressor operator systems. One of these contacts involves two conserved base pairs (G(6).C(-6) and A(5). T(-5)) and three amino acids (Lys 72, Ile 79, and Ala 80). To investigate the nature of these contacts, we analyzed the X-ray structure (PDB code: 1TRO) of the trp-repressor operator complex by means of molecular dynamics simulations. This X-ray structure contains two dimers that exhibit structural differences. From these two different starting structures, two 10 ns molecular dynamics simulations have been performed. Both of our simulations show an increase of water molecules in the major groove at one side of the dimer, while the other side remains unchanged compared to the X-ray structure. Though the maximum residence time of the concerned water molecules decreases with an increase of solvent at the interface, these water molecules continue to play an important role in mediating DNA-protein contacts. This is shown by new stable amino acids-DNA distances and a long water residence time compared to free DNA simulation. To maintain stability of the new contacts, the preferential water binding site on O6(G6) is extended. This extension agrees with mutation experiment data on A5 and G6, which shows different relative affinity due to mutation on these bases [A. Joachimiak, T. E. Haran, P. B. Sigler, EMBO Journal 1994, Vol. 13, No. (2) pp. 367-372]. Due to the rearrangements in the system, the phosphate of the base G6 is able to interconvert to the B(II) substate, which is not observed on the other half side of the complex. The decrease of the number of hydrogen bonds between protein and DNA backbone could be the initial step of the dissociation process of the complex, or in other words an intermediate complex conformation of the association process. Thus, we surmise that these features show the importance of water-mediated contacts in the trp-repressor operator recognition process.
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Affiliation(s)
- Fajar R Wibowo
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria
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Finucane MD, Jardetzky O. Surface plasmon resonance studies of wild-type and AV77 tryptophan repressor resolve ambiguities in super-repressor activity. Protein Sci 2003; 12:1613-20. [PMID: 12876311 PMCID: PMC2323948 DOI: 10.1110/ps.0305703] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The interactions of wild-type (WT) and AV77 tryptophan repressor (TR) with several operators have been studied using surface plasmon resonance. The use of this real-time method has been able to settle several outstanding issues in the field, in a way that has heretofore not been possible. We resolve the issue of the super-repressor status of the AV77 aporepressor and find that in contrast to early studies, which found no significant difference in the binding constants in vitro to those of the WT, that there is indeed a clear difference in the binding constant that can simply account for the phenotype. Accordingly, there is no need for alternative proposals invoking complex equilibria with in vivo components not found in the in vitro experiments. In addition, we find that the AV77 holorepressor-DNA complex is much more stable than the equivalent WT complex, which has not been apparent from either in vitro or equilibrium binding experiments.
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Affiliation(s)
- Michael D Finucane
- Department of Molecular Pharmacology, Stanford University, Stanford, CA 94305-5174, USA
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