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Li Y, Guo Y, Niu F, Gao H, Wang Q, Xu M. Regulation of oxidative stress response and antioxidant modification in Corynebacterium glutamicum. World J Microbiol Biotechnol 2024; 40:267. [PMID: 39004689 DOI: 10.1007/s11274-024-04066-z] [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: 05/11/2024] [Accepted: 06/27/2024] [Indexed: 07/16/2024]
Abstract
As an efficient and safe industrial bacterium, Corynebacterium glutamicum has extensive application in amino acid production. However, it often faces oxidative stress induced by reactive oxygen species (ROS), leading to diminished production efficiency. To enhance the robustness of C. glutamicum, numerous studies have focused on elucidating its regulatory mechanisms under various stress conditions such as heat, acid, and sulfur stress. However, a comprehensive review of its defense mechanisms against oxidative stress is needed. This review offers an in-depth overview of the mechanisms C. glutamicum employs to manage oxidative stress. It covers both enzymatic and non-enzymatic systems, including antioxidant enzymes, regulatory protein families, sigma factors involved in transcription, and physiological redox reduction pathways. This review provides insights for advancing research on the antioxidant mechanisms of C. glutamicum and sheds light on its potential applications in industrial production.
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Affiliation(s)
- Yueshu Li
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Yuanyi Guo
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Fangyuan Niu
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Hui Gao
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Qing Wang
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Meijuan Xu
- The Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China.
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Martinez Pastor M, Sakrikar S, Hwang S, Hackley R, Soborowski A, Maupin-Furlow J, Schmid A. TroR is the primary regulator of the iron homeostasis transcription network in the halophilic archaeon Haloferax volcanii. Nucleic Acids Res 2024; 52:125-140. [PMID: 37994787 PMCID: PMC10783522 DOI: 10.1093/nar/gkad997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 10/10/2023] [Accepted: 10/23/2023] [Indexed: 11/24/2023] Open
Abstract
Maintaining the intracellular iron concentration within the homeostatic range is vital to meet cellular metabolic needs and reduce oxidative stress. Previous research revealed that the haloarchaeon Halobacterium salinarum encodes four diphtheria toxin repressor (DtxR) family transcription factors (TFs) that together regulate the iron response through an interconnected transcriptional regulatory network (TRN). However, the conservation of the TRN and the metal specificity of DtxR TFs remained poorly understood. Here we identified and characterized the TRN of Haloferax volcanii for comparison. Genetic analysis demonstrated that Hfx. volcanii relies on three DtxR transcriptional regulators (Idr, SirR, and TroR), with TroR as the primary regulator of iron homeostasis. Bioinformatics and molecular approaches revealed that TroR binds a conserved cis-regulatory motif located ∼100 nt upstream of the start codon of iron-related target genes. Transcriptomics analysis demonstrated that, under conditions of iron sufficiency, TroR repressed iron uptake and induced iron storage mechanisms. TroR repressed the expression of one other DtxR TF, Idr. This reduced DtxR TRN complexity relative to that of Hbt. salinarum appeared correlated with natural variations in iron availability. Based on these data, we hypothesize that variable environmental conditions such as iron availability appear to select for increasing TRN complexity.
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Affiliation(s)
| | - Saaz Sakrikar
- Center for Genomics and System Biology at NYU Department of Biology, New York University, NY, NY 10003, USA
| | - Sungmin Hwang
- Division of Practical Research, Honam National Institute of Biological Resources, Jeollanam-do, Mokpo-si 58762, Republic of Korea
| | - Rylee K Hackley
- Department of Biology, Duke University, Durham, NC 27708, USA
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
| | - Andrew L Soborowski
- Department of Biology, Duke University, Durham, NC 27708, USA
- Computational Biology and Bioinformatics graduate program, Duke University, Durham, NC 27708, USA
| | - Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA
- Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - Amy K Schmid
- Department of Biology, Duke University, Durham, NC 27708, USA
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
- Computational Biology and Bioinformatics graduate program, Duke University, Durham, NC 27708, USA
- Center for Genomics and Computational Biology, Duke University, Durham, NC 27708, USA
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3
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Glasscock CJ, Pecoraro R, McHugh R, Doyle LA, Chen W, Boivin O, Lonnquist B, Na E, Politanska Y, Haddox HK, Cox D, Norn C, Coventry B, Goreshnik I, Vafeados D, Lee GR, Gordan R, Stoddard BL, DiMaio F, Baker D. Computational design of sequence-specific DNA-binding proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558720. [PMID: 37790440 PMCID: PMC10542524 DOI: 10.1101/2023.09.20.558720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Sequence-specific DNA-binding proteins (DBPs) play critical roles in biology and biotechnology, and there has been considerable interest in the engineering of DBPs with new or altered specificities for genome editing and other applications. While there has been some success in reprogramming naturally occurring DBPs using selection methods, the computational design of new DBPs that recognize arbitrary target sites remains an outstanding challenge. We describe a computational method for the design of small DBPs that recognize specific target sequences through interactions with bases in the major groove, and employ this method in conjunction with experimental screening to generate binders for 5 distinct DNA targets. These binders exhibit specificity closely matching the computational models for the target DNA sequences at as many as 6 base positions and affinities as low as 30-100 nM. The crystal structure of a designed DBP-target site complex is in close agreement with the design model, highlighting the accuracy of the design method. The designed DBPs function in both Escherichia coli and mammalian cells to repress and activate transcription of neighboring genes. Our method is a substantial step towards a general route to small and hence readily deliverable sequence-specific DBPs for gene regulation and editing.
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Affiliation(s)
- Cameron J. Glasscock
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Robert Pecoraro
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Ryan McHugh
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Lindsey A. Doyle
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, Washington, USA
| | - Wei Chen
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Olivier Boivin
- Program in Genetics and Genomic, Duke University, Durham, NC, USA
- Center for Advanced Genomic Technologies, Duke University, Durham, NC, USA
| | - Beau Lonnquist
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Emily Na
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Yuliya Politanska
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Hugh K. Haddox
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, Washington, USA
| | - David Cox
- Department of Biochemistry, Stanford University School of Medicine, Palo Alto, CA USA
- Department of Medicine, Division of Hematology, Stanford University, Stanford, CA, USA
| | - Christoffer Norn
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- BioInnovation Institute, DK2200 Copenhagen N, Denmark
| | - Brian Coventry
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Inna Goreshnik
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Dionne Vafeados
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Gyu Rie Lee
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA USA
| | - Raluca Gordan
- Center for Advanced Genomic Technologies, Duke University, Durham, NC, USA
- Department of Biostatistics and Bioinformatics, Department of Computer Science, Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
| | - Barry L. Stoddard
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, Washington, USA
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- BioInnovation Institute, DK2200 Copenhagen N, Denmark
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Marcos-Torres FJ, Juniar L, Griese JJ. The molecular mechanisms of the bacterial iron sensor IdeR. Biochem Soc Trans 2023:233013. [PMID: 37140254 DOI: 10.1042/bst20221539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/12/2023] [Accepted: 04/18/2023] [Indexed: 05/05/2023]
Abstract
Life came to depend on iron as a cofactor for many essential enzymatic reactions. However, once the atmosphere was oxygenated, iron became both scarce and toxic. Therefore, complex mechanisms have evolved to scavenge iron from an environment in which it is poorly bioavailable, and to tightly regulate intracellular iron contents. In bacteria, this is typically accomplished with the help of one key regulator, an iron-sensing transcription factor. While Gram-negative bacteria and Gram-positive species with low guanine-cytosine (GC) content generally use Fur (ferric uptake regulator) proteins to regulate iron homeostasis, Gram-positive species with high GC content use the functional homolog IdeR (iron-dependent regulator). IdeR controls the expression of iron acquisition and storage genes, repressing the former, and activating the latter in an iron-dependent manner. In bacterial pathogens such as Corynebacterium diphtheriae and Mycobacterium tuberculosis, IdeR is also involved in virulence, whereas in non-pathogenic species such as Streptomyces, it regulates secondary metabolism as well. Although in recent years the focus of research on IdeR has shifted towards drug development, there is much left to learn about the molecular mechanisms of IdeR. Here, we summarize our current understanding of how this important bacterial transcriptional regulator represses and activates transcription, how it is allosterically activated by iron binding, and how it recognizes its DNA target sites, highlighting the open questions that remain to be addressed.
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Affiliation(s)
- Francisco Javier Marcos-Torres
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-CSIC, 18011 Granada, Spain
| | - Linda Juniar
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
| | - Julia J Griese
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
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Choi WW, Jeong H, Kim Y, Lee HS. Gene nceA encodes a Ni/Co-sensing transcription factor to regulate metal efflux in Corynebacterium glutamicum. METALLOMICS : INTEGRATED BIOMETAL SCIENCE 2022; 14:6865361. [PMID: 36460048 DOI: 10.1093/mtomcs/mfac094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 11/23/2022] [Indexed: 12/04/2022]
Abstract
The function of Corynebacterium glutamicum open reading frame (ORF) NCgl2684 (named nceA in this study), which was annotated to encode a metalloregulator, was assessed using physiological, genetic, and biochemical approaches. Cells with deleted-nceA (ΔnceA) showed a resistant phenotype to NiSO4 and CoSO4 and showed faster growth in minimal medium containing 20 μM NiSO4 or 10 μM CoSO4 than both the wild-type and nceA-overexpressing (P180-nceA) cells. In the ΔnceA strain, the transcription of the downstream-located ORF NCgl2685 (nceB), annotated to encode efflux protein, was increased approximately 4-fold, whereas gene transcription decreased down to 30% level in the P180-nceA strain. The transcriptions of the nceA and nceB genes were stimulated, even when as little as 5 nM NiSO4 was added to the growth medium. Protein NceA was able to bind DNA comprising the promoter region (from -14 to + 18) of the nceA--nceB operon. The protein-DNA interaction was abolished in the presence of 20 μM NiSO4, 50 μM CoSO4, or 50 μM CdSO4. Although manganese induced the transcription of the nceA and nceB genes, it failed to interrupt protein-DNA interaction. Simultaneously, the P180-nceA cells showed increased sensitivity to oxidants such as menadione, hydrogen peroxide, and cumene hydroperoxide, but not diamide. Collectively, our data show that NceA is a nickel- and cobalt-sensing transcriptional regulator that controls the transcription of the probable efflux protein-encoding nceB. The genes are able to suppress intracellular levels of nickel to prevent reactions, which can cause oxidative damage to cellular components.
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Affiliation(s)
- Won-Woo Choi
- Department of Biotechnology and Bioinformatics, Korea University, Sejong 30019, Republic of Korea.,Interdisciplinary Graduate Program for Artificial Intelligence Smart Convergence Technology, Korea University, Sejong 30019, Republic of Korea
| | - Haeri Jeong
- Department of Biotechnology and Bioinformatics, Korea University, Sejong 30019, Republic of Korea
| | - Younhee Kim
- Department of Korean Medicine, Semyung University, Jecheon, Chungbuk 27136, Republic of Korea
| | - Heung-Shick Lee
- Department of Biotechnology and Bioinformatics, Korea University, Sejong 30019, Republic of Korea.,Interdisciplinary Graduate Program for Artificial Intelligence Smart Convergence Technology, Korea University, Sejong 30019, Republic of Korea
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Yang X, Wang Y, Liu G, Deng Z, Lin S, Zheng J. Structural basis of Streptomyces transcription activation by zinc uptake regulator. Nucleic Acids Res 2022; 50:8363-8376. [PMID: 35871291 PMCID: PMC9371925 DOI: 10.1093/nar/gkac627] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 06/30/2022] [Accepted: 07/20/2022] [Indexed: 11/30/2022] Open
Abstract
Streptomyces coelicolor (Sc) is a model organism of actinobacteria to study morphological differentiation and production of bioactive metabolites. Sc zinc uptake regulator (Zur) affects both processes by controlling zinc homeostasis. It activates transcription by binding to palindromic Zur-box sequences upstream of −35 elements. Here we deciphered the molecular mechanism by which ScZur interacts with promoter DNA and Sc RNA polymerase (RNAP) by cryo-EM structures and biochemical assays. The ScZur-DNA structures reveal a sequential and cooperative binding of three ScZur dimers surrounding a Zur-box spaced 8 nt upstream from a −35 element. The ScRNAPσHrdB-Zur-DNA structures define protein-protein and protein-DNA interactions involved in the principal housekeeping σHrdB-dependent transcription initiation from a noncanonical promoter with a −10 element lacking the critical adenine residue at position −11 and a TTGCCC −35 element deviating from the canonical TTGACA motif. ScZur interacts with the C-terminal domain of ScRNAP α subunit (αCTD) in a complex structure trapped in an active conformation. Key ScZur-αCTD interfacial residues accounting for ScZur-dependent transcription activation were confirmed by mutational studies. Together, our structural and biochemical results provide a comprehensive model for transcription activation of Zur family regulators.
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Affiliation(s)
- Xu Yang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
| | - Yiqun Wang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
| | - Guiyang Liu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
| | - Shuangjun Lin
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
| | - Jianting Zheng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University , Shanghai 200240, China
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7
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Bacterial Transcriptional Regulators: A Road Map for Functional, Structural, and Biophysical Characterization. Int J Mol Sci 2022; 23:ijms23042179. [PMID: 35216300 PMCID: PMC8879271 DOI: 10.3390/ijms23042179] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/11/2022] [Accepted: 02/11/2022] [Indexed: 12/12/2022] Open
Abstract
The different niches through which bacteria move during their life cycle require a fast response to the many environmental queues they encounter. The sensing of these stimuli and their correct response is driven primarily by transcriptional regulators. This kind of protein is involved in sensing a wide array of chemical species, a process that ultimately leads to the regulation of gene transcription. The allosteric-coupling mechanism of sensing and regulation is a central aspect of biological systems and has become an important field of research during the last decades. In this review, we summarize the state-of-the-art techniques applied to unravel these complex mechanisms. We introduce a roadmap that may serve for experimental design, depending on the answers we seek and the initial information we have about the system of study. We also provide information on databases containing available structural information on each family of transcriptional regulators. Finally, we discuss the recent results of research about the allosteric mechanisms of sensing and regulation involving many transcriptional regulators of interest, highlighting multipronged strategies and novel experimental techniques. The aim of the experiments discussed here was to provide a better understanding at a molecular level of how bacteria adapt to the different environmental threats they face.
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Bradley JM, Svistunenko DA, Wilson MT, Hemmings AM, Moore GR, Le Brun NE. Bacterial iron detoxification at the molecular level. J Biol Chem 2021; 295:17602-17623. [PMID: 33454001 PMCID: PMC7762939 DOI: 10.1074/jbc.rev120.007746] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 10/07/2020] [Indexed: 01/18/2023] Open
Abstract
Iron is an essential micronutrient, and, in the case of bacteria, its availability is commonly a growth-limiting factor. However, correct functioning of cells requires that the labile pool of chelatable "free" iron be tightly regulated. Correct metalation of proteins requiring iron as a cofactor demands that such a readily accessible source of iron exist, but overaccumulation results in an oxidative burden that, if unchecked, would lead to cell death. The toxicity of iron stems from its potential to catalyze formation of reactive oxygen species that, in addition to causing damage to biological molecules, can also lead to the formation of reactive nitrogen species. To avoid iron-mediated oxidative stress, bacteria utilize iron-dependent global regulators to sense the iron status of the cell and regulate the expression of proteins involved in the acquisition, storage, and efflux of iron accordingly. Here, we survey the current understanding of the structure and mechanism of the important members of each of these classes of protein. Diversity in the details of iron homeostasis mechanisms reflect the differing nutritional stresses resulting from the wide variety of ecological niches that bacteria inhabit. However, in this review, we seek to highlight the similarities of iron homeostasis between different bacteria, while acknowledging important variations. In this way, we hope to illustrate how bacteria have evolved common approaches to overcome the dual problems of the insolubility and potential toxicity of iron.
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Affiliation(s)
- Justin M Bradley
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom.
| | | | - Michael T Wilson
- School of Life Sciences, University of Essex, Colchester, United Kingdom
| | - Andrew M Hemmings
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom; Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Geoffrey R Moore
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom.
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Sousa Gerós A, Simmons A, Drakesmith H, Aulicino A, Frost JN. The battle for iron in enteric infections. Immunology 2020; 161:186-199. [PMID: 32639029 PMCID: PMC7576875 DOI: 10.1111/imm.13236] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 07/01/2020] [Indexed: 02/06/2023] Open
Abstract
Iron is an essential element for almost all living organisms, but can be extremely toxic in high concentrations. All organisms must therefore employ homeostatic mechanisms to finely regulate iron uptake, usage and storage in the face of dynamic environmental conditions. The critical step in mammalian systemic iron homeostasis is the fine regulation of dietary iron absorption. However, as the gastrointestinal system is also home to >1014 bacteria, all of which engage in their own programmes of iron homeostasis, the gut represents an anatomical location where the inter-kingdom fight for iron is never-ending. Here, we explore the molecular mechanisms of, and interactions between, host and bacterial iron homeostasis in the gastrointestinal tract. We first detail how mammalian systemic and cellular iron homeostasis influences gastrointestinal iron availability. We then focus on two important human pathogens, Salmonella and Clostridia; despite their differences, they exemplify how a bacterial pathogen must navigate and exploit this web of iron homeostasis interactions to avoid host nutritional immunity and replicate successfully. We then reciprocally explore how iron availability interacts with the gastrointestinal microbiota, and the consequences of this on mammalian physiology and pathogen iron acquisition. Finally, we address how understanding the battle for iron in the gastrointestinal tract might inform clinical practice and inspire new treatments for important diseases.
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Affiliation(s)
- Ana Sousa Gerós
- MRC Human Immunology UnitWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
- Translational Gastroenterology UnitJohn Radcliffe HospitalOxfordUK
| | - Alison Simmons
- MRC Human Immunology UnitWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
- Translational Gastroenterology UnitJohn Radcliffe HospitalOxfordUK
| | - Hal Drakesmith
- MRC Human Immunology UnitWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
| | - Anna Aulicino
- MRC Human Immunology UnitWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
- Translational Gastroenterology UnitJohn Radcliffe HospitalOxfordUK
| | - Joe N. Frost
- MRC Human Immunology UnitWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
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Berg K, Pedersen HL, Leiros I. Biochemical characterization of ferric uptake regulator (Fur) from Aliivibrio salmonicida. Mapping the DNA sequence specificity through binding studies and structural modelling. Biometals 2020; 33:169-185. [PMID: 32648080 PMCID: PMC7536154 DOI: 10.1007/s10534-020-00240-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 06/28/2020] [Indexed: 11/25/2022]
Abstract
Iron is an essential nutrient for bacteria, however its propensity to form toxic hydroxyl radicals at high intracellular concentrations, requires its acquisition to be tightly regulated. Ferric uptake regulator (Fur) is a metal-dependent DNA-binding protein that acts as a transcriptional regulator in maintaining iron metabolism in bacteria and is a highly interesting target in the design of new antibacterial drugs. Fur mutants have been shown to exhibit decreased virulence in infection models. The protein interacts specifically with DNA at binding sites designated as 'Fur boxes'. In the present study, we have investigated the interaction between Fur from the fish pathogen Aliivibrio salmonicida (AsFur) and its target DNA using a combination of biochemical and in silico methods. A series of target DNA oligomers were designed based on analyses of Fur boxes from other species, and affinities assessed using electrophoretic mobility shift assay. Binding strengths were interpreted in the context of homology models of AsFur to gain molecular-level insight into binding specificity.
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Affiliation(s)
- Kristel Berg
- Department of Chemistry, Faculty of Science and Technology, The Norwegian Structural Biology Centre (NorStruct), UiT the Arctic University of Norway, 9037, Tromsø, Norway
| | - Hege Lynum Pedersen
- Department of Chemistry, Faculty of Science and Technology, The Norwegian Structural Biology Centre (NorStruct), UiT the Arctic University of Norway, 9037, Tromsø, Norway
| | - Ingar Leiros
- Department of Chemistry, Faculty of Science and Technology, The Norwegian Structural Biology Centre (NorStruct), UiT the Arctic University of Norway, 9037, Tromsø, Norway.
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11
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The Iron Deficiency Response of Corynebacterium glutamicum and a Link to Thiamine Biosynthesis. Appl Environ Microbiol 2020; 86:AEM.00065-20. [PMID: 32144105 DOI: 10.1128/aem.00065-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 02/28/2020] [Indexed: 12/20/2022] Open
Abstract
The response to iron limitation of the Gram-positive soil bacterium Corynebacterium glutamicum was analyzed with respect to secreted metabolites, the transcriptome, and the proteome. During growth in glucose minimal medium, iron limitation caused a shift from lactate to pyruvate as the major secreted organic acid complemented by l-alanine and 2-oxoglutarate. Transcriptome and proteome analyses revealed that a pronounced iron starvation response governed by the transcriptional regulators DtxR and RipA was detectable in the late, but not in the early, exponential-growth phase. A link between iron starvation and thiamine pyrophosphate (TPP) biosynthesis was uncovered by the strong upregulation of thiC As phosphomethylpyrimidine synthase (ThiC) contains an iron-sulfur cluster, limiting activities of the TPP-dependent pyruvate-2-oxoglutarate dehydrogenase supercomplex probably cause the excretion of pyruvate and 2-oxoglutarate. In line with this explanation, thiamine supplementation could strongly diminish the secretion of these acids. The upregulation of thiC and other genes involved in thiamine biosynthesis and transport is presumably due to TPP riboswitches present at the 5' end of the corresponding operons. The results obtained in this study provide new insights into iron homeostasis in C. glutamicum and demonstrate that the metabolic consequences of iron limitation can be due to the iron dependency of coenzyme biosynthesis.IMPORTANCE Iron is an essential element for most organisms but causes problems due to poor solubility under oxic conditions and due to toxicity by catalyzing the formation of reactive oxygen species (ROS). Therefore, bacteria have evolved complex regulatory networks for iron homeostasis aiming at a sufficient iron supply while minimizing ROS formation. In our study, the responses of the actinobacterium Corynebacterium glutamicum to iron limitation were analyzed, resulting in a detailed view on the processes involved in iron homeostasis in this model organism. In particular, we provide evidence that iron limitation causes TPP deficiency, presumably due to insufficient activity of the iron-dependent phosphomethylpyrimidine synthase (ThiC). TPP deficiency was deduced from the upregulation of genes controlled by a TPP riboswitch and secretion of metabolites caused by insufficient activity of the TPP-dependent enzymes pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. To our knowledge, the link between iron starvation and thiamine synthesis has not been elaborated previously.
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12
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Lee MY, Lee DW, Joo HK, Jeong KH, Lee JY. Structural analysis of the manganese transport regulator MntR from Bacillus halodurans in apo and manganese bound forms. PLoS One 2019; 14:e0224689. [PMID: 31738781 PMCID: PMC6860424 DOI: 10.1371/journal.pone.0224689] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 10/18/2019] [Indexed: 01/05/2023] Open
Abstract
The manganese transport regulator MntR is a metal-ion activated transcriptional repressor of manganese transporter genes to maintain manganese ion homeostasis. MntR, a member of the diphtheria toxin repressor (DtxR) family of metalloregulators, selectively responds to Mn2+ and Cd2+ over Fe2+, Co2+ and Zn2+. The DtxR/MntR family members are well conserved transcriptional repressors that regulate the expression of metal ion uptake genes by sensing the metal ion concentration. MntR functions as a homo-dimer with one metal ion binding site per subunit. Each MntR subunit contains two domains: an N-terminal DNA binding domain, and a C-terminal dimerization domain. However, it lacks the C-terminal SH3-like domain of DtxR/IdeR. The metal ion binding site of MntR is located at the interface of the two domains, whereas the DtxR/IdeR subunit contains two metal ion binding sites, the primary and ancillary sites, separated by 9 Å. In this paper, we reported the crystal structures of the apo and Mn2+-bound forms of MntR from Bacillus halodurans, and analyze the structural basis of the metal ion binding site. The crystal structure of the Mn2+-bound form is almost identical to the apo form of MntR. In the Mn2+-bound structure, one subunit contains a binuclear cluster of manganese ions, the A and C sites, but the other subunit forms a mononuclear complex. Structural data about MntR from B. halodurans supports the previous hypothesizes about manganese-specific activation mechanism of MntR homologues.
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Affiliation(s)
- Myeong Yeon Lee
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Dong Won Lee
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Hyun Kyu Joo
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Kang Hwa Jeong
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Jae Young Lee
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
- * E-mail:
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Parveen S, Bishai WR, Murphy JR. Corynebacterium diphtheriae: Diphtheria Toxin, the tox Operon, and Its Regulation by Fe2 + Activation of apo-DtxR. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0063-2019. [PMID: 31267892 PMCID: PMC8713076 DOI: 10.1128/microbiolspec.gpp3-0063-2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Indexed: 11/20/2022] Open
Abstract
Diphtheria is one of the most well studied of all the bacterial infectious diseases. These milestone studies of toxigenic Corynebacterium diphtheriae along with its primary virulence determinant, diphtheria toxin, have established the paradigm for the study of other related bacterial protein toxins. This review highlights those studies that have contributed to our current understanding of the structure-function relationships of diphtheria toxin, the molecular mechanism of its entry into the eukaryotic cell cytosol, the regulation of diphtheria tox expression by holo-DtxR, and the molecular basis of transition metal ion activation of apo-DtxR itself. These seminal studies have laid the foundation for the protein engineering of diphtheria toxin and the development of highly potent eukaryotic cell-surface receptor-targeted fusion protein toxins for the treatment of human diseases that range from T cell malignancies to steroid-resistant graft-versus-host disease to metastatic melanoma. This deeper scientific understanding of diphtheria toxin and the regulation of its expression have metamorphosed the third-most-potent bacterial toxin known into a life-saving targeted protein therapeutic, thereby at least partially fulfilling Paul Erlich's concept of a magic bullet-"a chemical that binds to and specifically kills microbes or tumor cells."
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Affiliation(s)
- Sadiya Parveen
- Department of Medicine, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21231
| | - William R Bishai
- Department of Medicine, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21231
| | - John R Murphy
- Department of Medicine, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21231
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Aono S, Nakajima H. Transcriptional Regulation of Gene Expression by Metalloproteins. PROGRESS IN REACTION KINETICS AND MECHANISM 2019. [DOI: 10.3184/007967400103165128] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
FNR and SoxR are transcriptional regulators containing an iron–sulfur cluster. The iron–sulfur cluster in FNR acts as an oxygen sensor by reacting with oxygen. The structural change of the iron–sulfur cluster takes place when FNR senses oxygen, which regulates the transcriptional regulator activity of FNR through the change of the quaternary structure. SoxR contains the [2Fe–2S] cluster that regulates the transcriptional activator activity of SoxR. Only the oxidized SoxR containing the [2Fe–2S]2+ cluster is active as the transcriptional activator. CooA is a transcriptional activator containing a protoheme that acts as a CO sensor. CO is a physiological effector of CooA and regulates the transcriptional activator activity of CooA. In this review, the biochemical and biophysical properties of FNR, SoxR, and CooA are described.
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Affiliation(s)
- Shigetoshi Aono
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan
| | - Hiroshi Nakajima
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan
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15
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Bacterial zinc uptake regulator proteins and their regulons. Biochem Soc Trans 2018; 46:983-1001. [PMID: 30065104 PMCID: PMC6103462 DOI: 10.1042/bst20170228] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 06/25/2018] [Accepted: 06/26/2018] [Indexed: 01/10/2023]
Abstract
All organisms must regulate the cellular uptake, efflux, and intracellular trafficking of essential elements, including d-block metal ions. In bacteria, such regulation is achieved by the action of metal-responsive transcriptional regulators. Among several families of zinc-responsive transcription factors, the ‘zinc uptake regulator’ Zur is the most widespread. Zur normally represses transcription in its zinc-bound form, in which DNA-binding affinity is enhanced allosterically. Experimental and bioinformatic searches for Zur-regulated genes have revealed that in many cases, Zur proteins govern zinc homeostasis in a much more profound way than merely through the expression of uptake systems. Zur regulons also comprise biosynthetic clusters for metallophore synthesis, ribosomal proteins, enzymes, and virulence factors. In recognition of the importance of zinc homeostasis at the host–pathogen interface, studying Zur regulons of pathogenic bacteria is a particularly active current research area.
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Abstract
Iron is an essential micronutrient for both microbes and humans alike. For well over half a century we have known that this element, in particular, plays a pivotal role in health and disease and, most especially, in shaping host-pathogen interactions. Intracellular iron concentrations serve as a critical signal in regulating the expression not only of high-affinity iron acquisition systems in bacteria, but also of toxins and other noted virulence factors produced by some major human pathogens. While we now are aware of many strategies that the host has devised to sequester iron from invading microbes, there are as many if not more sophisticated mechanisms by which successful pathogens overcome nutritional immunity imposed by the host. This review discusses some of the essential components of iron sequestration and scavenging mechanisms of the host, as well as representative Gram-negative and Gram-positive pathogens, and highlights recent advances in the field. Last, we address how the iron acquisition strategies of pathogenic bacteria may be exploited for the development of novel prophylactics or antimicrobials.
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17
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Metallochaperones and metalloregulation in bacteria. Essays Biochem 2017; 61:177-200. [PMID: 28487396 DOI: 10.1042/ebc20160076] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 02/23/2017] [Accepted: 02/27/2017] [Indexed: 12/21/2022]
Abstract
Bacterial transition metal homoeostasis or simply 'metallostasis' describes the process by which cells control the intracellular availability of functionally required metal cofactors, from manganese (Mn) to zinc (Zn), avoiding both metal deprivation and toxicity. Metallostasis is an emerging aspect of the vertebrate host-pathogen interface that is defined by a 'tug-of-war' for biologically essential metals and provides the motivation for much recent work in this area. The host employs a number of strategies to starve the microbial pathogen of essential metals, while for others attempts to limit bacterial infections by leveraging highly competitive metals. Bacteria must be capable of adapting to these efforts to remodel the transition metal landscape and employ highly specialized metal sensing transcriptional regulators, termed metalloregulatory proteins,and metallochaperones, that allocate metals to specific destinations, to mediate this adaptive response. In this essay, we discuss recent progress in our understanding of the structural mechanisms and metal specificity of this adaptive response, focusing on energy-requiring metallochaperones that play roles in the metallocofactor active site assembly in metalloenzymes and metallosensors, which govern the systems-level response to metal limitation and intoxication.
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Takeuchi K, Imai M, Shimada I. Dynamic equilibrium on DNA defines transcriptional regulation of a multidrug binding transcriptional repressor, LmrR. Sci Rep 2017; 7:267. [PMID: 28325892 PMCID: PMC5428041 DOI: 10.1038/s41598-017-00257-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 02/14/2017] [Indexed: 11/09/2022] Open
Abstract
LmrR is a multidrug binding transcriptional repressor that controls the expression of a major multidrug transporter, LmrCD, in Lactococcus lactis. Promiscuous compound ligations reduce the affinity of LmrR for the lmrCD operator by several fold to release the transcriptional repression; however, the affinity reduction is orders of magnitude smaller than that of typical transcriptional repressors. Here, we found that the transcriptional regulation of LmrR is achieved through an equilibrium between the operator-bound and non-specific DNA-adsorption states in vivo. The effective dissociation constant of LmrR for the lmrCD operator under the equilibrium is close to the endogenous concentration of LmrR, which allows a substantial reduction of LmrR occupancy upon compound ligations. Therefore, LmrR represents a dynamic type of transcriptional regulation of prokaryotic multidrug resistance systems, where the small affinity reduction induced by compounds is coupled to the functional relocalization of the repressor on the genomic DNA via nonspecific DNA adsorption.
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Affiliation(s)
- Koh Takeuchi
- Biomedicinal Information Research Center & Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Aomi 2-3-26, Koto-ku, Tokyo, 135-0064, Japan.,PRESTO, JST, Aomi 2-3-26, Koto-ku, Tokyo, 135-0064, Japan
| | - Misaki Imai
- Research and Development Department, Japan Biological Informatics Consortium, Aomi 2-3-26, Koto-ku, Tokyo, 135-0064, Japan
| | - Ichio Shimada
- Biomedicinal Information Research Center & Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Aomi 2-3-26, Koto-ku, Tokyo, 135-0064, Japan. .,Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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Mulé MP, Giacalone D, Lawlor K, Golden A, Cook C, Lott T, Aksten E, O'Toole GA, Bergeron LJ. Iron-dependent gene expression in Actinomyces oris. J Oral Microbiol 2015; 7:29800. [PMID: 26685151 PMCID: PMC4684579 DOI: 10.3402/jom.v7.29800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/20/2015] [Accepted: 11/23/2015] [Indexed: 11/21/2022] Open
Abstract
Background Actinomyces oris is a Gram-positive bacterium that has been associated with healthy and diseased sites in the human oral cavity. Most pathogenic bacteria require iron to survive, and in order to acquire iron in the relatively iron-scarce oral cavity A. oris has been shown to produce iron-binding molecules known as siderophores. The genes encoding these siderophores and transporters are thought to be regulated by the amount of iron in the growth medium and by the metal-dependent repressor, AmdR, which we showed previously binds to the promoter of proposed iron-regulated genes. Objective The purpose of this study was to characterize siderophore and associated iron transport systems in A. oris.
Design We examined gene expression of the putative iron transport genes fetA and sidD in response to low- and high-iron environments. One of these genes, sidD, encoding a putative Fe ABC transporter protein, was insertionally inactivated and was examined for causing growth defects. To gain a further understanding of the role of iron metabolism in oral diseases, clinical isolates of Actinomyces spp. were examined for the presence of the gene encoding AmdR, a proposed global regulator of iron-dependent gene expression in A. oris.
Results When A. oris was grown under iron-limiting conditions, the genes encoding iron/siderophore transporters fetA and sidD showed increased expression. One of these genes (sidD) was mutated, and the sidD::Km strain exhibited a 50% reduction in growth in late log and stationary phase cells in media that contained iron. This growth defect was restored when the sidD gene was provided in a complemented strain. We were able to isolate the AmdR-encoding gene in seven clinical isolates of Actinomyces. When these protein sequences were aligned to the laboratory strain, there was a high degree of sequence similarity. Conclusions The growth of the sidD::Km mutant in iron-replete medium mirrored the growth of the wild-type strain grown in iron-limiting medium, suggesting that the sidD::Km mutant was compromised in iron uptake. The known iron regulator AmdR is well conserved in clinical isolates of A. oris. This work provides additional insight into iron metabolism in this important oral microbe.
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Affiliation(s)
- Matthew P Mulé
- Department of Biology, New England College, Henniker, NH, USA
| | - David Giacalone
- Department of Biology, New England College, Henniker, NH, USA
| | - Kayla Lawlor
- Department of Biology, New England College, Henniker, NH, USA
| | - Alexa Golden
- Department of Biology, New England College, Henniker, NH, USA
| | - Caroline Cook
- Department of Biology, New England College, Henniker, NH, USA
| | - Thomas Lott
- Department of Biology, New England College, Henniker, NH, USA
| | | | - George A O'Toole
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Lori J Bergeron
- Department of Biology, New England College, Henniker, NH, USA;
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20
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Liang JL, Nie Y, Wang M, Xiong G, Wang YP, Maser E, Wu XL. Regulation of alkane degradation pathway by a TetR family repressor via an autoregulation positive feedback mechanism in a Gram-positiveDietziabacterium. Mol Microbiol 2015; 99:338-59. [DOI: 10.1111/mmi.13232] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/25/2015] [Indexed: 01/26/2023]
Affiliation(s)
- Jie-Liang Liang
- Department of Energy and Resources Engineering; College of Engineering; Peking University; Beijing 100871 China
| | - Yong Nie
- Department of Energy and Resources Engineering; College of Engineering; Peking University; Beijing 100871 China
| | - Miaoxiao Wang
- Department of Energy and Resources Engineering; College of Engineering; Peking University; Beijing 100871 China
| | - Guangming Xiong
- Institute of Toxicology and Pharmacology for Natural Scientists; University Medical School; Schleswig-Holstein, Campus Kiel Kiel 24105 Germany
| | - Yi-Ping Wang
- State Key Laboratory of Protein and Plant Gene Research; College of Life Sciences; Peking University; Beijing 100871 China
| | - Edmund Maser
- Institute of Toxicology and Pharmacology for Natural Scientists; University Medical School; Schleswig-Holstein, Campus Kiel Kiel 24105 Germany
| | - Xiao-Lei Wu
- Department of Energy and Resources Engineering; College of Engineering; Peking University; Beijing 100871 China
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21
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Interactions of the Metalloregulatory Protein SloR from Streptococcus mutans with Its Metal Ion Effectors and DNA Binding Site. J Bacteriol 2015; 197:3601-15. [PMID: 26350131 DOI: 10.1128/jb.00612-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 08/28/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Streptococcus mutans is the causative agent of dental caries, a significant concern for human health, and therefore an attractive target for therapeutics development. Previous work in our laboratory has identified a homodimeric, manganese-dependent repressor protein, SloR, as an important regulator of cariogenesis and has used site-directed mutagenesis to map functions to specific regions of the protein. Here we extend those studies to better understand the structural interaction between SloR and its operator and its effector metal ions. The results of DNase I assays indicate that SloR protects a 42-bp region of DNA that overlaps the sloABC promoter on the S. mutans UA159 chromosome, while electrophoretic mobility shift and solution binding assays indicate that each of two SloR dimers binds to this region. Real-time semiquantitative reverse transcriptase PCR (real-time semi-qRT-PCR) experiments were used to determine the individual base pairs that contribute to SloR-DNA binding specificity. Solution studies indicate that Mn(2+) is better than Zn(2+) at specifically activating SloR to bind DNA, and yet the 2.8-Å resolved crystal structure of SloR bound to Zn(2+) provides insight into the means by which selective activation by Mn(2+) may be achieved and into how SloR may form specific interactions with its operator. Taken together, these experimental observations are significant because they can inform rational drug design aimed at alleviating and/or preventing S. mutans-induced caries formation. IMPORTANCE This report focuses on investigating the SloR protein as a regulator of essential metal ion transport and virulence gene expression in the oral pathogen Streptococcus mutans and on revealing the details of SloR binding to its metal ion effectors and binding to DNA that together facilitate this expression. We used molecular and biochemical approaches to characterize the interaction of SloR with Mn(2+) and with its SloR recognition element to gain a clearer picture of the regulatory networks that optimize SloR-mediated metal ion homeostasis and virulence gene expression in S. mutans. These experiments can have a significant impact on caries treatment and/or prevention by revealing the S. mutans SloR-DNA binding interface as an appropriate target for the development of novel therapeutic interventions.
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22
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Kaushik MS, Singh P, Tiwari B, Mishra AK. Ferric Uptake Regulator (FUR) protein: properties and implications in cyanobacteria. ANN MICROBIOL 2015. [DOI: 10.1007/s13213-015-1134-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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23
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Wang C, Sun Y, Wang J, Xu H, Lu JR. Copper(II)-Mediated Self-Assembly of Hairpin Peptides and Templated Synthesis of CuS Nanowires. Chem Asian J 2015; 10:1953-8. [PMID: 26110265 DOI: 10.1002/asia.201500467] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Indexed: 11/06/2022]
Abstract
The self-assembly of peptides and proteins under well-controlled conditions underlies important nanostructuring processes that could be harnessed in practical applications. Herein, the synthesis of a new hairpin peptide containing four histidine residues is reported and the self-assembly process mediated by metal ions is explored. The work involves the combined use of circular dichroism, NMR spectroscopy, UV/Vis spectroscopy, AFM, and TEM to follow the structural and morphological details of the metal-coordination-mediated folding and self-assembly of the peptide. The results indicate that by forming a tetragonal coordination geometry with four histidine residues, copper(II) ions selectively trigger the peptide to fold and then self-assemble into nanofibrils. Furthermore, the copper(II)-bound nanofibrils template the synthesis of CuS nanowires, which display a near-infrared laser-induced thermal effect.
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Affiliation(s)
- Chengdong Wang
- State Key Laboratory of Heavy Oil Processing, and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Changjiang West Road, Qingdao, 266580, P.R. China
| | - Yawei Sun
- State Key Laboratory of Heavy Oil Processing, and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Changjiang West Road, Qingdao, 266580, P.R. China
| | - Jiqian Wang
- State Key Laboratory of Heavy Oil Processing, and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Changjiang West Road, Qingdao, 266580, P.R. China
| | - Hai Xu
- State Key Laboratory of Heavy Oil Processing, and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Changjiang West Road, Qingdao, 266580, P.R. China.
| | - Jian R Lu
- School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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Deng Z, Wang Q, Liu Z, Zhang M, Machado ACD, Chiu TP, Feng C, Zhang Q, Yu L, Qi L, Zheng J, Wang X, Huo X, Qi X, Li X, Wu W, Rohs R, Li Y, Chen Z. Mechanistic insights into metal ion activation and operator recognition by the ferric uptake regulator. Nat Commun 2015; 6:7642. [PMID: 26134419 PMCID: PMC4506495 DOI: 10.1038/ncomms8642] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 05/27/2015] [Indexed: 01/21/2023] Open
Abstract
Ferric uptake regulator (Fur) plays a key role in the iron homeostasis of prokaryotes, such as bacterial pathogens, but the molecular mechanisms and structural basis of Fur-DNA binding remain incompletely understood. Here, we report high-resolution structures of Magnetospirillum gryphiswaldense MSR-1 Fur in four different states: apo-Fur, holo-Fur, the Fur-feoAB1 operator complex and the Fur-Pseudomonas aeruginosa Fur box complex. Apo-Fur is a transition metal ion-independent dimer whose binding induces profound conformational changes and confers DNA-binding ability. Structural characterization, mutagenesis, biochemistry and in vivo data reveal that Fur recognizes DNA by using a combination of base readout through direct contacts in the major groove and shape readout through recognition of the minor-groove electrostatic potential by lysine. The resulting conformational plasticity enables Fur binding to diverse substrates. Our results provide insights into metal ion activation and substrate recognition by Fur that suggest pathways to engineer magnetotactic bacteria and antipathogenic drugs.
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Affiliation(s)
- Zengqin Deng
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Qing Wang
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Zhao Liu
- Experimental Research Center, China Academy of Chinese Medical Sciences, Beijing 100700, China
| | - Manfeng Zhang
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Ana Carolina Dantas Machado
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Tsu-Pei Chiu
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Chong Feng
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Qi Zhang
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Lin Yu
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Lei Qi
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Jiangge Zheng
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Xu Wang
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - XinMei Huo
- Institute of Apicultural Research, Key Laboratory of Pollinating Insect Biology, Chinese Academy of Agricultural Science, Beijing 100093, China
| | - Xiaoxuan Qi
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Xiaorong Li
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Wei Wu
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Remo Rohs
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Ying Li
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Zhongzhou Chen
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
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Fernandez-López R, Ruiz R, de la Cruz F, Moncalián G. Transcription factor-based biosensors enlightened by the analyte. Front Microbiol 2015; 6:648. [PMID: 26191047 PMCID: PMC4486848 DOI: 10.3389/fmicb.2015.00648] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Accepted: 06/15/2015] [Indexed: 01/17/2023] Open
Abstract
Whole cell biosensors (WCBs) have multiple applications for environmental monitoring, detecting a wide range of pollutants. WCBs depend critically on the sensitivity and specificity of the transcription factor (TF) used to detect the analyte. We describe the mechanism of regulation and the structural and biochemical properties of TF families that are used, or could be used, for the development of environmental WCBs. Focusing on the chemical nature of the analyte, we review TFs that respond to aromatic compounds (XylS-AraC, XylR-NtrC, and LysR), metal ions (MerR, ArsR, DtxR, Fur, and NikR) or antibiotics (TetR and MarR). Analyzing the structural domains involved in DNA recognition, we highlight the similitudes in the DNA binding domains (DBDs) of these TF families. Opposite to DBDs, the wide range of analytes detected by TFs results in a diversity of structures at the effector binding domain. The modular architecture of TFs opens the possibility of engineering TFs with hybrid DNA and effector specificities. Yet, the lack of a crisp correlation between structural domains and specific functions makes this a challenging task.
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Affiliation(s)
| | | | | | - Gabriel Moncalián
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria – Consejo Superior de Investigaciones CientíficasSantander, Spain
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Sheldon JR, Heinrichs DE. Recent developments in understanding the iron acquisition strategies of gram positive pathogens. FEMS Microbiol Rev 2015; 39:592-630. [DOI: 10.1093/femsre/fuv009] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2015] [Indexed: 12/26/2022] Open
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27
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Pröpper K, Meindl K, Sammito M, Dittrich B, Sheldrick GM, Pohl E, Usón I. Structure solution of DNA-binding proteins and complexes with ARCIMBOLDO libraries. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:1743-57. [PMID: 24914984 PMCID: PMC4051508 DOI: 10.1107/s1399004714007603] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 04/04/2014] [Indexed: 11/11/2022]
Abstract
Protein-DNA interactions play a major role in all aspects of genetic activity within an organism, such as transcription, packaging, rearrangement, replication and repair. The molecular detail of protein-DNA interactions can be best visualized through crystallography, and structures emphasizing insight into the principles of binding and base-sequence recognition are essential to understanding the subtleties of the underlying mechanisms. An increasing number of high-quality DNA-binding protein structure determinations have been witnessed despite the fact that the crystallographic particularities of nucleic acids tend to pose specific challenges to methods primarily developed for proteins. Crystallographic structure solution of protein-DNA complexes therefore remains a challenging area that is in need of optimized experimental and computational methods. The potential of the structure-solution program ARCIMBOLDO for the solution of protein-DNA complexes has therefore been assessed. The method is based on the combination of locating small, very accurate fragments using the program Phaser and density modification with the program SHELXE. Whereas for typical proteins main-chain α-helices provide the ideal, almost ubiquitous, small fragments to start searches, in the case of DNA complexes the binding motifs and DNA double helix constitute suitable search fragments. The aim of this work is to provide an effective library of search fragments as well as to determine the optimal ARCIMBOLDO strategy for the solution of this class of structures.
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Affiliation(s)
- Kevin Pröpper
- University of Göttingen, Germany
- Instituto de Biologia Molecular de Barcelona (IBMB-CSIC), Spain
| | - Kathrin Meindl
- Instituto de Biologia Molecular de Barcelona (IBMB-CSIC), Spain
| | - Massimo Sammito
- Instituto de Biologia Molecular de Barcelona (IBMB-CSIC), Spain
| | | | | | | | - Isabel Usón
- Instituto de Biologia Molecular de Barcelona (IBMB-CSIC), Spain
- Institucio Catalana de Recerca i Estudis Avancats (ICREA), Spain
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Amangyeld T, Shin YK, Lee M, Kwon B, Seo YS. Human MUS81-EME2 can cleave a variety of DNA structures including intact Holliday junction and nicked duplex. Nucleic Acids Res 2014; 42:5846-62. [PMID: 24692662 PMCID: PMC4027171 DOI: 10.1093/nar/gku237] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
MUS81 shares a high-degree homology with the catalytic XPF subunit of the XPF–ERCC1 endonuclease complex. It is catalytically active only when complexed with the regulatory subunits Mms4 or Eme1 in budding and fission yeasts, respectively, and EME1 or EME2 in humans. Although Mus81 complexes are implicated in the resolution of recombination intermediates in vivo, recombinant yeast Mus81-Mms4 and human MUS81-EME1 isolated from Escherichia coli fail to cleave intact Holliday junctions (HJs) in vitro. In this study, we show that human recombinant MUS81-EME2 isolated from E. coli cleaves HJs relatively efficiently, compared to MUS81-EME1. Furthermore, MUS81-EME2 catalyzed cleavage of nicked and gapped duplex deoxyribonucleic acids (DNAs), generating double-strand breaks. The presence of a 5′ phosphate terminus at nicks and gaps rendered DNA significantly less susceptible to the cleavage by MUS81-EME2 than its absence, raising the possibility that this activity could play a role in channeling damaged DNA duplexes that are not readily repaired into the recombinational repair pathways. Significant differences in substrate specificity observed with unmodified forms of MUS81-EME1 and MUS81-EME2 suggest that they play related but non-overlapping roles in DNA transactions.
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Affiliation(s)
- Tamir Amangyeld
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Yong-Keol Shin
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Miju Lee
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Buki Kwon
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Yeon-Soo Seo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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29
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Fadden AJ, Schalbetter S, Bowles M, Harris R, Lally J, Carr AM, McDonald NQ. A winged helix domain in human MUS81 binds DNA and modulates the endonuclease activity of MUS81 complexes. Nucleic Acids Res 2013; 41:9741-52. [PMID: 23982516 PMCID: PMC3834828 DOI: 10.1093/nar/gkt760] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 07/05/2013] [Accepted: 07/31/2013] [Indexed: 11/14/2022] Open
Abstract
The MUS81-EME1 endonuclease maintains metazoan genomic integrity by cleaving branched DNA structures that arise during the resolution of recombination intermediates. In humans, MUS81 also forms a poorly characterized complex with EME2. Here, we identify and determine the structure of a winged helix (WH) domain from human MUS81, which binds DNA. WH domain mutations greatly reduce binding of the isolated domain to DNA and impact on incision activity of MUS81-EME1/EME2 complexes. Deletion of the WH domain reduces the endonuclease activity of both MUS81-EME1 and MUS81-EME2 complexes, and incisions made by MUS81-EME2 are made closer to the junction on substrates containing a downstream duplex, such as fork structures and nicked Holliday junctions. WH domain mutation or deletion in Schizosaccharomyces pombe phenocopies the DNA-damage sensitivity of strains deleted for mus81. Our results indicate an important role for the WH domain in both yeast and human MUS81 complexes.
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Affiliation(s)
- Andrew J. Fadden
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Stephanie Schalbetter
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Maureen Bowles
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Richard Harris
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - John Lally
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Antony M. Carr
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Neil Q. McDonald
- Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK, Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK and Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
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30
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Lisher JP, Higgins KA, Maroney MJ, Giedroc DP. Physical characterization of the manganese-sensing pneumococcal surface antigen repressor from Streptococcus pneumoniae. Biochemistry 2013; 52:7689-701. [PMID: 24067066 DOI: 10.1021/bi401132w] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Transition metals, including manganese, are required for the proper virulence and persistence of many pathogenic bacteria. In Streptococcus pneumoniae (Spn), manganese homeostasis is controlled by a high-affinity Mn(II) uptake complex, PsaBCA, and a constitutively expressed efflux transporter, MntE. psaBCA expression is transcriptionally regulated by the DtxR/MntR family metalloregulatory protein pneumococcal surface antigen repressor (PsaR) in Spn. Here, we present a comprehensive analysis of the metal and DNA binding properties of PsaR. PsaR is a homodimer in the absence and presence of metals and binds two manganese or zinc atoms per protomer (four per dimer) in two pairs of structurally distinct sites, termed site 1 and site 2. Site 1 is likely filled with Zn(II) in vivo (K(Zn1) ≥ 10¹³ M⁻¹; K(Mn1) ≈ 10⁸ M⁻¹). The Zn(II)-site 1 complex adopts a pentacoordinate geometry as determined by X-ray absorption spectroscopy containing a single cysteine and appears to be analogous to the Cd(II) site observed in Streptococcus gordonii ScaR. Site 1 is necessary but not sufficient for full positive allosteric activation of DNA operator binding by metals as measured by ΔGc, the allosteric coupling free energy, because site 1 mutants show an intermediate ΔGc. Site 2 is the primary regulatory site and governs specificity for Mn(II) over Zn(II) in PsaR, where ΔGc(Zn,Mn) >> ΔGc(Zn,Zn) despite the fact that Zn(II) binds site 2 with an affinity 40-fold higher than that of Mn(II); i.e., K(Zn2) > K(Mn2). Mutational studies reveal that Asp7 in site 2 is a critical ligand for Mn(II)-dependent allosteric activation of DNA binding. These findings are discussed in the context of other well-studied DtxR/MntR Mn(II)/Fe(II) metallorepressors.
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Affiliation(s)
- John P Lisher
- Department of Chemistry and ‡Interdisciplinary Graduate Program in Biochemistry, Indiana University , Bloomington, Indiana 47405-7102, United States
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Cloning, expression, purification and characterization of an iron-dependent regulator protein from Thermobifida fusca. Protein Expr Purif 2013; 92:190-4. [PMID: 24084005 DOI: 10.1016/j.pep.2013.09.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 09/15/2013] [Accepted: 09/17/2013] [Indexed: 11/22/2022]
Abstract
Iron-dependent regulators (IdeRs) control the transcription of a variety of genes associated with iron homeostasis in Gram-positive bacteria. In this study we report the cloning of a putative IdeR gene from the moderate thermophile Thermobifida fusca into the pET-21a(+) expression vector. The expressed protein, Tf-IdeR, was purified using immobilized metal affinity and size-exclusion chromatography, and yielded approximately 12-16 mg of protein per liter of culture. The purified Tf-IdeR protein binds the tox operator sequence in the presence of divalent metal ions. Two Tf-IdeR binding sites were identified in the T. fusca genome upstream of a putative enterobactin exporter and a putative ABC-type multidrug transporter.
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32
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Chakraborty S. A quantitative measure of electrostatic perturbation in holo and apo enzymes induced by structural changes. PLoS One 2013; 8:e59352. [PMID: 23516628 PMCID: PMC3597595 DOI: 10.1371/journal.pone.0059352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 02/13/2013] [Indexed: 11/19/2022] Open
Abstract
Biological pathways are subject to subtle manipulations that achieve a wide range of functional variation in differing physiological niches. In many instances, changes in the structure of an enzyme on ligand binding germinate electrostatic perturbations that form the basis of its changed catalytic or transcriptional efficiency. Computational methods that seek to gain insights into the electrostatic changes in enzymes require expertise to setup and computing prowess. In the current work, we present a fast, easy and reliable methodology to compute electrostatic perturbations induced by ligand binding (MEPP). The theoretical foundation of MEPP is the conserved electrostatic potential difference (EPD) in cognate pairs of active site residues in proteins with the same functionality. Previously, this invariance has been used to unravel promiscuous serine protease and metallo-β-lactamase scaffolds in alkaline phosphatases. Given that a similarity in EPD is significant, we expect differences in the EPD to be significant too. MEPP identifies residues or domains that undergo significant electrostatic perturbations, and also enumerates residue pairs that undergo significant polarity change. The gain in a certain polarity of a residue with respect to neighboring residues, or the reversal of polarity between two residues might indicate a change in the preferred ligand. The methodology of MEPP has been demonstrated on several enzymes that employ varying mechanisms to perform their roles. For example, we have attributed the change in polarity in residue pairs to be responsible for the loss of metal ion binding in fructose 1,6-bisphosphatases, and corroborated the pre-organized state of the active site of the enzyme with respect to functionally relevant changes in electric fields in ketosteroid isomerases.
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Affiliation(s)
- Sandeep Chakraborty
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
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33
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Wong JJW, Lu J, Glover JNM. Relaxosome function and conjugation regulation in F-like plasmids - a structural biology perspective. Mol Microbiol 2012; 85:602-17. [PMID: 22788760 DOI: 10.1111/j.1365-2958.2012.08131.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The tra operon of the prototypical F plasmid and its relatives enables transfer of a copy of the plasmid to other bacterial cells via the process of conjugation. Tra proteins assemble to form the transferosome, the transmembrane pore through which the DNA is transferred, and the relaxosome, a complex of DNA-binding proteins at the origin of DNA transfer. F-like plasmid conjugation is characterized by a high degree of plasmid specificity in the interactions of tra components, and is tightly regulated at the transcriptional, translational and post-translational levels. Over the past decade, X-ray crystallography of conjugative components has yielded insights into both specificity and regulatory mechanisms. Conjugation is repressed by FinO, an RNA chaperone which increases the lifetime of the small RNA, FinP. Recent work has resulted in a detailed model of FinO/FinP interactions and the discovery of a family of FinO-like RNA chaperones. Relaxosome components include TraI, a relaxase/helicase, and TraM, which mediates signalling between the transferosome and relaxosome for transfer initiation. The structures of TraI and TraM bound to oriT DNA reveal the basis of specific recognition of DNA for their cognate plasmid. Specificity also exists in TraI and TraM interactions with the transferosome protein TraD.
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Affiliation(s)
- Joyce J W Wong
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
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34
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Yeo HK, Kang J, Park YW, Sung JS, Lee JY. Crystallization and preliminary X-ray diffraction analysis of the metalloregulatory protein DtxR from Thermoplasma acidophilum. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:172-4. [PMID: 22297991 DOI: 10.1107/s1744309111051700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 11/30/2011] [Indexed: 11/10/2022]
Abstract
The diphtheria toxin repressor (DtxR) is a metal-ion-dependent transcriptional regulator which regulates genes encoding proteins involved in metal-ion uptake to maintain metal-ion homeostasis. DtxR from Thermoplasma acidophilum was cloned and overexpressed in Escherichia coli. Crystals of N-terminally His-tagged DtxR were obtained by hanging-drop vapour diffusion and diffracted to 1.8 Å resolution. DtxR was crystallized at 296 K using polyethylene glycol 4000 as a precipitant. The crystals belonged to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 61.14, b = 84.61, c = 46.91 Å, α = β = γ = 90°. The asymmetric unit contained approximately one monomer of DtxR, giving a crystal volume per mass (V(M)) of 2.22 Å(3) Da(-1) and a solvent content of 44.6%.
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Affiliation(s)
- Hyun Ku Yeo
- Department of Life Science, Dongguk University, Seoul, Republic of Korea
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35
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Abstract
The dramatic changes in the environmental conditions that organisms encountered during evolution and adaptation to life in specific niches, have influenced intracellular and extracellular metal ion contents and, as a consequence, the cellular ability to sense and utilize different metal ions. This metal-driven differentiation is reflected in the specific panels of metal-responsive transcriptional regulators found in different organisms, which finely tune the intracellular metal ion content and all metal-dependent processes. In order to understand the processes underlying this complex metal homeostasis network, the study of the molecular processes that determine the protein-metal ion recognition, as well as how this event is transduced into a transcriptional output, is necessary. This chapter describes how metal ion binding to specific proteins influences protein interaction with DNA and how this event can influence the fate of genetic expression, leading to specific transcriptional outputs. The features of representative metal-responsive transcriptional regulators, as well as the molecular basis of metal-protein and protein-DNA interactions, are discussed on the basis of the structural information available. An overview of the recent advances in the understanding of how these proteins choose specific metal ions among the intracellular metal ion pool, as well as how they allosterically respond to their effector binding, is given.
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36
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Protein photocrosslinking reveals dimer of dimers formation on MarR protein in Escherichia coli. Sci China Chem 2011. [DOI: 10.1007/s11426-011-4437-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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37
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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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38
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Chandrasekhar V, Mahanti B, Bandipalli P, Bhanuprakash K, Nair NN. Cyclometalated Ir(III) complexes containing N-aryl picolinamide ancillary ligands. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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39
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Wong JJW, Lu J, Edwards RA, Frost LS, Glover JNM. Structural basis of cooperative DNA recognition by the plasmid conjugation factor, TraM. Nucleic Acids Res 2011; 39:6775-88. [PMID: 21565799 PMCID: PMC3159463 DOI: 10.1093/nar/gkr296] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The conjugative transfer of F-like plasmids such as F, R1, R100 and pED208, between bacterial cells requires TraM, a plasmid-encoded DNA-binding protein. TraM tetramers bridge the origin of transfer (oriT) to a key component of the conjugative pore, the coupling protein TraD. Here we show that TraM recognizes a high-affinity DNA-binding site, sbmA, as a cooperative dimer of tetramers. The crystal structure of the TraM-sbmA complex from the plasmid pED208 shows that binding cooperativity is mediated by DNA kinking and unwinding, without any direct contact between tetramers. Sequence-specific DNA recognition is carried out by TraM's N-terminal ribbon-helix-helix (RHH) domains, which bind DNA in a staggered arrangement. We demonstrate that both DNA-binding specificity, as well as selective interactions between TraM and the C-terminal tail of its cognate TraD mediate conjugation specificity within the F-like family of plasmids. The ability of TraM to cooperatively bind DNA without interaction between tetramers leaves the C-terminal TraM tetramerization domains free to make multiple interactions with TraD, driving recruitment of the plasmid to the conjugative pore.
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Affiliation(s)
- Joyce J W Wong
- Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
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40
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Choi SS, Chivers PT, Berg DE. Point mutations in Helicobacter pylori's fur regulatory gene that alter resistance to metronidazole, a prodrug activated by chemical reduction. PLoS One 2011; 6:e18236. [PMID: 21464913 PMCID: PMC3064673 DOI: 10.1371/journal.pone.0018236] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2010] [Accepted: 02/23/2011] [Indexed: 02/08/2023] Open
Abstract
Background Helicobacter pylori's Fur regulatory protein controls transcription of dozens of genes in response to iron availability, acidity and oxidative stress, and affects the vigor of infection and severity of disease. It is unusual among Fur family proteins in being active both when iron-loaded and iron-free. Metholodolgy/Principal Findings We tested if H. pylori fur mutations could affect resistance to metronidazole (Mtz), an anti-H. pylori prodrug rendered bactericidal by chemical reduction. Point mutations were made by PCR in DNA containing fur and a downstream chloramphenicol resistance gene, and were placed in the H. pylori chromosome by transformation of a fur-deletion (Δfur) strain. Several substitutions affecting H. pylori Fur's ∼10 residue N terminal arm, which has no counterpart in prototype (E. coli-type) Fur proteins, increased Mtz resistance, as did mutations affecting the region between DNA binding and dimerization domains. Three types of mutations decreased resistance more than did Δfur: substitutions affecting the N-terminal arm; substitutions affecting the metal binding pocket; and nonsense mutations that resulted in a truncated Fur protein with no C-terminal dimerization domain. Most metal binding pocket mutations were obtained only in fur genes with additional inactivating mutations, and thus seemed deleterious or lethal because they. Conclusions/Significance These results establish that H. pylori Fur's distinctive N terminal arm is functional, and more generally illustrate that point mutations can confer informative phenotypes, distinct from those conferred by null mutations. We propose that fur mutations can affect Mtz susceptibility by altering the balance among Fur's several competing activities, and thereby the expression of genes that control cellular redox potential or elimination of bactericidal Mtz activation products. Further analyses of selected mutants should provide insights into Fur interactions with other cellular components, metabolic circuitry, and how H. pylori thrives in its special gastric niche.
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Affiliation(s)
- Sung Sook Choi
- Department of Molecular Microbiology, Washington University Medical School, St Louis, Missouri, United States of America
| | - Peter T. Chivers
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St Louis, Missouri, United States of America
| | - Douglas E. Berg
- Department of Molecular Microbiology, Washington University Medical School, St Louis, Missouri, United States of America
- * E-mail:
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41
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Geobacter uraniireducens NikR displays a DNA binding mode distinct from other members of the NikR family. J Bacteriol 2010; 192:4327-36. [PMID: 20581212 DOI: 10.1128/jb.00152-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
NikR is a nickel-responsive ribbon-helix-helix transcription factor present in many bacteria and archaea. The DNA binding properties of Escherichia coli and Helicobacter pylori NikR (factors EcNikR and HpNikR, respectively) have revealed variable features of DNA recognition. EcNikR represses a single operon by binding to a perfect inverted repeat sequence, whereas HpNikR binds to promoters from multiple genes that contain poorly conserved inverted repeats. These differences are due in large part to variations in the amino acid sequences of the DNA-contacting beta-sheets, as well as residues preceding the beta-sheets of these two proteins. We present here evidence of another variation in DNA recognition by the NikR protein from Geobacter uraniireducens (GuNikR). GuNikR has an Arg-Gly-Ser beta-sheet that binds specifically to an inverted repeat sequence distinct from those recognized by Ec- or HpNikR. The N-terminal residues that precede the GuNikR beta-sheet residues are required for high-affinity DNA binding. Mutation of individual arm residues dramatically reduced the affinity of GuNikR for specific DNA. Interestingly, GuNikR tetramers are capable of binding cooperatively to the promoter regions of two different genes, nik(MN)1 and nik(MN)2. Cooperativity was not observed for the closely related G. bemidjiensis NikR, which recognizes the same operator sequence. The cooperative mode of DNA binding displayed by GuNikR could affect the sensitivity of transporter gene expression to changes in intracellular nickel levels.
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42
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McLaughlin KJ, Strain-Damerell CM, Xie K, Brekasis D, Soares AS, Paget MSB, Kielkopf CL. Structural basis for NADH/NAD+ redox sensing by a Rex family repressor. Mol Cell 2010; 38:563-75. [PMID: 20513431 DOI: 10.1016/j.molcel.2010.05.006] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 02/21/2010] [Accepted: 05/11/2010] [Indexed: 01/26/2023]
Abstract
Nicotinamide adenine dinucleotides have emerged as key signals of the cellular redox state. Yet the structural basis for allosteric gene regulation by the ratio of reduced NADH to oxidized NAD(+) is poorly understood. A key sensor among Gram-positive bacteria, Rex represses alternative respiratory gene expression until a limited oxygen supply elevates the intracellular NADH:NAD(+) ratio. Here we investigate the molecular mechanism for NADH/NAD(+) sensing among Rex family members by determining structures of Thermus aquaticus Rex bound to (1) NAD(+), (2) DNA operator, and (3) without ligand. Comparison with the Rex/NADH complex reveals that NADH releases Rex from the DNA site following a 40 degrees closure between the dimeric subunits. Complementary site-directed mutagenesis experiments implicate highly conserved residues in NAD-responsive DNA-binding activity. These rare views of a redox sensor in action establish a means for slight differences in the nicotinamide charge, pucker, and orientation to signal the redox state of the cell.
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Affiliation(s)
- Krystle J McLaughlin
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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43
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Wu CY, Chen YC, Lim C. A structural-alphabet-based strategy for finding structural motifs across protein families. Nucleic Acids Res 2010; 38:e150. [PMID: 20525797 PMCID: PMC2919736 DOI: 10.1093/nar/gkq478] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Proteins with insignificant sequence and overall structure similarity may still share locally conserved contiguous structural segments; i.e. structural/3D motifs. Most methods for finding 3D motifs require a known motif to search for other similar structures or functionally/structurally crucial residues. Here, without requiring a query motif or essential residues, a fully automated method for discovering 3D motifs of various sizes across protein families with different folds based on a 16-letter structural alphabet is presented. It was applied to structurally non-redundant proteins bound to DNA, RNA, obligate/non-obligate proteins as well as free DNA-binding proteins (DBPs) and proteins with known structures but unknown function. Its usefulness was illustrated by analyzing the 3D motifs found in DBPs. A non-specific motif was found with a ‘corner’ architecture that confers a stable scaffold and enables diverse interactions, making it suitable for binding not only DNA but also RNA and proteins. Furthermore, DNA-specific motifs present ‘only’ in DBPs were discovered. The motifs found can provide useful guidelines in detecting binding sites and computational protein redesign.
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Affiliation(s)
- Chih Yuan Wu
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
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Langlois RE, Lu H. Boosting the prediction and understanding of DNA-binding domains from sequence. Nucleic Acids Res 2010; 38:3149-58. [PMID: 20156993 PMCID: PMC2879530 DOI: 10.1093/nar/gkq061] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
DNA-binding proteins perform vital functions related to transcription, repair and replication. We have developed a new sequence-based machine learning protocol to identify DNA-binding proteins. We compare our method with an extensive benchmark of previously published structure-based machine learning methods as well as a standard sequence alignment technique, BLAST. Furthermore, we elucidate important feature interactions found in a learned model and analyze how specific rules capture general mechanisms that extend across DNA-binding motifs. This analysis is carried out using the malibu machine learning workbench available at http://proteomics.bioengr.uic.edu/malibu and the corresponding data sets and features are available at http://proteomics.bioengr.uic.edu/dna.
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Affiliation(s)
- Robert E Langlois
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60612, USA
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45
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Lie TJ, Hendrickson EL, Niess UM, Moore BC, Haydock AK, Leigh JA. Overlapping repressor binding sites regulate expression of the Methanococcus maripaludis glnK(1) operon. Mol Microbiol 2009; 75:755-62. [PMID: 20025661 DOI: 10.1111/j.1365-2958.2009.07016.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The euryarchaeal transcriptional repressor NrpR regulates a variety of nitrogen assimilation genes by 2-oxoglutarate-reversible binding to conserved palindromic operators. The number and positioning of these operators varies among promoter regions of regulated genes, suggesting NrpR can bind in different patterns. Particularly intriguing is the contrast between the nif and glnK(1) promoter regions of Methanococcus maripaludis, where two operators are present but with different configurations. Here we study NrpR binding and regulation at the glnK(1) promoter, where the two operator sequences overlap and occur on opposite faces of the double helix. We find that both operators function in binding, with a dimer of NrpR binding simultaneously to each overlapping operator. We show in vivo that the first operator plays a primary role in regulation and the second operator plays an enhancing role. This is the first demonstration of overlapping operators functioning in Archaea.
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Affiliation(s)
- Thomas J Lie
- Department of Microbiology, University of Washington, Box 357242, Seattle, WA 98195-7242, USA
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46
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Crystal structure of the manganese transport regulatory protein fromEscherichia coli. Proteins 2009; 77:741-6. [DOI: 10.1002/prot.22541] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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47
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Stoll KE, Draper WE, Kliegman JI, Golynskiy MV, Brew-Appiah RAT, Phillips RK, Brown HK, Breyer WA, Jakubovics NS, Jenkinson HF, Brennan RG, Cohen SM, Glasfeld A. Characterization and structure of the manganese-responsive transcriptional regulator ScaR. Biochemistry 2009; 48:10308-20. [PMID: 19795834 PMCID: PMC3586275 DOI: 10.1021/bi900980g] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The streptococcal coaggregation regulator (ScaR) of Streptococcus gordonii is a manganese-dependent transcriptional regulator. When intracellular manganese concentrations become elevated, ScaR represses transcription of the scaCBA operon, which encodes a manganese uptake transporter. A member of the DtxR/MntR family of metalloregulators, ScaR shares sequence similarity with other family members, and many metal-binding residues are conserved. Here, we show that ScaR is an active dimer, with two dimers binding the 46 base pair scaC operator. Each ScaR subunit binds two manganese ions, and the protein is activated by a variety of other metal ions, including Cd(2+), Co(2+), and Ni(2+) but not Zn(2+). The crystal structure of apo-ScaR reveals a tertiary and quaternary structure similar to its homologue, the iron-responsive regulator DtxR. While each DtxR subunit binds a metal ion in two sites, labeled primary and ancillary, crystal structures of ScaR determined in the presence of Cd(2+) and Zn(2+) show only a single occupied metal-binding site that is novel to ScaR. The site analogous to the primary site in DtxR is unoccupied, and the ancillary site is absent from ScaR. Instead, metal ions bind to ScaR at a site labeled "secondary", which is composed of Glu80, Cys123, His125, and Asp160 and lies roughly 5 A away from where the ancillary site would be predicted to exist. This difference suggests that ScaR and its closely related homologues are activated by a mechanism distinct from that of either DtxR or MntR.
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Affiliation(s)
- Kate E. Stoll
- Department of Chemistry, Reed College, Portland, Oregon 97202
| | | | - Joseph I. Kliegman
- Department of Chemistry, Reed College, Portland, Oregon 97202
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0358
| | - Misha V. Golynskiy
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0358
| | | | - Rebecca K. Phillips
- Department of Chemistry, Reed College, Portland, Oregon 97202
- Department of Biochemistry and Molecular Biology, U. T. M. D. Anderson Cancer Center, Unit 1000 Houston, TX 77030
| | - Hattie K. Brown
- Department of Chemistry, Reed College, Portland, Oregon 97202
| | - Wendy A. Breyer
- Department of Chemistry, Reed College, Portland, Oregon 97202
| | | | - Howard F. Jenkinson
- Department of Oral and Dental Science, University of Bristol, Bristol BS1 2LY, UK
| | - Richard G. Brennan
- Department of Biochemistry and Molecular Biology, U. T. M. D. Anderson Cancer Center, Unit 1000 Houston, TX 77030
| | - Seth M. Cohen
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0358
| | - Arthur Glasfeld
- Department of Chemistry, Reed College, Portland, Oregon 97202
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48
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Ma Z, Jacobsen FE, Giedroc DP. Coordination chemistry of bacterial metal transport and sensing. Chem Rev 2009; 109:4644-81. [PMID: 19788177 PMCID: PMC2783614 DOI: 10.1021/cr900077w] [Citation(s) in RCA: 426] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Zhen Ma
- Department of Chemistry, Indiana University, Bloomington, IN 47401-7005 USA
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128 USA
| | - Faith E. Jacobsen
- Department of Chemistry, Indiana University, Bloomington, IN 47401-7005 USA
| | - David P. Giedroc
- Department of Chemistry, Indiana University, Bloomington, IN 47401-7005 USA
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D'Aquino JA, Denninger AR, Moulin AG, D'Aquino KE, Ringe D. Decreased sensitivity to changes in the concentration of metal ions as the basis for the hyperactivity of DtxR(E175K). J Mol Biol 2009; 390:112-23. [PMID: 19433095 DOI: 10.1016/j.jmb.2009.05.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 04/29/2009] [Accepted: 05/06/2009] [Indexed: 11/25/2022]
Abstract
The metal-ion-activated diphtheria toxin repressor (DtxR) is responsible for the regulation of virulence and other genes in Corynebacterium diphtheriae. A single point mutation in DtxR, DtxR(E175K), causes this mutant repressor to have a hyperactive phenotype. Mice infected with Mycobacterium tuberculosis transformed with plasmids carrying this mutant gene show reduced signs of the tuberculosis infection. Corynebacterial DtxR is able to complement mycobacterial IdeR and vice versa. To date, an explanation for the hyperactivity of DtxR(E175K) has remained elusive. In an attempt to address this issue, we have solved the first crystal structure of DtxR(E175K) and characterized this mutant using circular dichroism, isothermal titration calorimetry, and other biochemical techniques. The results show that although DtxR(E175K) and the wild type have similar secondary structures, DtxR(E175K) gains additional thermostability upon activation with metal ions, which may lead to this mutant requiring a lower concentration of metal ions to reach the same levels of thermostability as the wild-type protein. The E175K mutation causes binding site 1 to retain metal ion bound at all times, which can only be removed by incubation with an ion chelator. The crystal structure of DtxR(E175K) shows an empty binding site 2 without evidence of oxidation of Cys102. The association constant for this low-affinity binding site of DtxR(E175K) obtained from calorimetric titration with Ni(II) is K(a)=7.6+/-0.5x10(4), which is very similar to the reported value for the wild-type repressor, K(a)=6.3x10(4). Both the wild type and DtxR(E175K) require the same amount of metal ion to produce a shift in the electrophoretic mobility shift assay, but unlike the wild type, DtxR(E175K) binding to its cognate DNA [tox promoter-operator (toxPO)] does not require metal-ion supplementation in the running buffer. In the timescale of these experiments, the Mn(II)-DtxR(E175K)-toxPO complex is insensitive to changes in the environmental cation concentrations. In addition to Mn(II), Ni(II), Co(II), Cd(II), and Zn(II) are able to sustain the hyperactive phenotype. These results demonstrate a prominent role of binding site 1 in the activation of DtxR and support the hypothesis that DtxR(E175K) attenuates the expression of virulence due to the decreased ability of the Me(II)-DtxR(E175K)-toxPO complex to dissociate at low concentrations of metal ions.
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Affiliation(s)
- J Alejandro D'Aquino
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
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50
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Ahmad R, Brandsdal BO, Michaud-Soret I, Willassen NP. Ferric uptake regulator protein: Binding free energy calculations and per-residue free energy decomposition. Proteins 2009; 75:373-86. [DOI: 10.1002/prot.22247] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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