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Nwokocha GC, Ghosh A, Grove A. Regulation of bacterial virulence genes by PecS family transcription factors. J Bacteriol 2024:e0030224. [PMID: 39287432 DOI: 10.1128/jb.00302-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2024] Open
Abstract
Bacterial plant pathogens adjust their gene expression programs in response to environmental signals and host-derived compounds. This ensures that virulence genes or genes encoding proteins, which promote bacterial fitness in a host environment, are expressed only when needed. Such regulation is in the purview of transcription factors, many of which belong to the ubiquitous multiple antibiotic resistance regulator (MarR) protein family. PecS proteins constitute a subset of this large protein family. PecS has likely been distributed by horizontal gene transfer, along with the divergently encoded efflux pump PecM, suggesting its integration into existing gene regulatory networks. Here, we discuss the roles of PecS in the regulation of genes associated with virulence and fitness of bacterial plant pathogens. A comparison of phenotypes and differential gene expression associated with the disruption of pecS shows that functional consequences of PecS integration into existing transcriptional networks are highly variable, resulting in distinct PecS regulons. Although PecS universally binds to the pecS-pecM intergenic region to repress the expression of both genes, binding modes differ. A particularly relaxed sequence preference appears to apply for Dickeya dadantii PecS, perhaps to optimize its integration as a global regulator and regulate genes ancestral to the acquisition of pecS-pecM. Even inducing ligands for PecS are not universally conserved. It appears that PecS function has been optimized to match the unique regulatory needs of individual bacterial species and that its roles must be appreciated in the context of the regulatory networks into which it was recruited.
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Affiliation(s)
| | - Arpita Ghosh
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
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2
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Xuan G, Xun L, Xia Y. MarR family proteins sense sulfane sulfur in bacteria. MLIFE 2024; 3:231-239. [PMID: 38948149 PMCID: PMC11211675 DOI: 10.1002/mlf2.12109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 12/12/2023] [Accepted: 12/24/2023] [Indexed: 07/02/2024]
Abstract
Members of the multiple antibiotic resistance regulator (MarR) protein family are ubiquitous in bacteria and play critical roles in regulating cellular metabolism and antibiotic resistance. MarR family proteins function as repressors, and their interactions with modulators induce the expression of controlled genes. The previously characterized modulators are insufficient to explain the activities of certain MarR family proteins. However, recently, several MarR family proteins have been reported to sense sulfane sulfur, including zero-valent sulfur, persulfide (R-SSH), and polysulfide (R-SnH, n ≥ 2). Sulfane sulfur is a common cellular component in bacteria whose levels vary during bacterial growth. The changing levels of sulfane sulfur affect the expression of many MarR-controlled genes. Sulfane sulfur reacts with the cysteine thiols of MarR family proteins, causing the formation of protein thiol persulfide, disulfide bonds, and other modifications. Several MarR family proteins that respond to reactive oxygen species (ROS) also sense sulfane sulfur, as both sulfane sulfur and ROS induce the formation of disulfide bonds. This review focused on MarR family proteins that sense sulfane sulfur. However, the sensing mechanisms reviewed here may also apply to other proteins that detect sulfane sulfur, which is emerging as a modulator of gene regulation.
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Affiliation(s)
- Guanhua Xuan
- State Key Laboratory of Microbial TechnologyShandong UniversityQingdaoChina
- State Key Laboratory of Marine Food Processing & Safety ControlOcean University of ChinaQingdaoChina
| | - Luying Xun
- State Key Laboratory of Microbial TechnologyShandong UniversityQingdaoChina
- School of Molecular BiosciencesWashington State UniversityPullmanWashingtonUSA
| | - Yongzhen Xia
- State Key Laboratory of Microbial TechnologyShandong UniversityQingdaoChina
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3
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The Global Regulator MftR Controls Virulence and Siderophore Production in Burkholderia thailandensis. J Bacteriol 2022; 204:e0023722. [PMID: 36286517 PMCID: PMC9664960 DOI: 10.1128/jb.00237-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial pathogens face iron limitation in a host environment. To overcome this challenge, they produce siderophores, small iron-chelating molecules.
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4
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Development of a Monoclonal Antibody to a Vibriophage as a Proxy for Vibrio cholerae Detection. Infect Immun 2022; 90:e0016122. [PMID: 35862704 PMCID: PMC9387236 DOI: 10.1128/iai.00161-22] [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] [Indexed: 11/24/2022] Open
Abstract
Cholera is an acute watery, diarrheal disease that causes high rates of morbidity and mortality without treatment. Early detection of the etiologic agent of toxigenic Vibrio cholerae is important to mobilize treatment and mitigate outbreaks. Monoclonal antibody (mAb) based rapid diagnostic tests (RDTs) enable early detection in settings without laboratory capacity. However, the odds of an RDT testing positive are reduced by nearly 90% when the common virulent bacteriophage ICP1 is present. We hypothesize that adding a mAb for the common, and specific, virulent bacteriophage ICP1 as a proxy for V. cholerae to an RDT will increase diagnostic sensitivity when virulent ICP1 phage is present. In this study, we used an in-silico approach to identify immunogenic ICP1 protein targets that were conserved across disparate time periods and locations. Specificity of targets to cholera patients with known ICP1 was determined, and specific targets were used to produce mAbs in a murine model. Candidate mAbs to the head protein demonstrated specificity to ICP1 by Enzyme linked immunosorbent assay (ELISA) and an ICP1 phage neutralization assay. The limit of detection of the final mAb candidate for ICP1 phage particles spiked into cholera stool matrix was 8 × 105 PFU by Western blotting analysis. This mAb will be incorporated into a RDT prototype for evaluation in a future diagnostic study to test the guiding hypothesis behind this study.
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5
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Grove A. Extracytoplasmic Function Sigma Factors Governing Production of the Primary Siderophores in Pathogenic Burkholderia Species. Front Microbiol 2022; 13:851011. [PMID: 35283809 PMCID: PMC8908255 DOI: 10.3389/fmicb.2022.851011] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 02/07/2022] [Indexed: 11/13/2022] Open
Abstract
Bacteria respond to changing environments by modulating their gene expression programs. One of the mechanisms by which this may be accomplished is by substituting the primary σ factor with an alternative σ factor belonging to the family of extracytoplasmic function (ECF) σ factors. ECF σ factors are activated only in presence of specific signals, and they direct the RNA polymerase (RNAP) to transcribe a defined subset of genes. One condition, which may trigger the activation of an ECF σ factor, is iron limitation. To overcome iron starvation, bacteria produce and secrete siderophores, which chelate iron and facilitate its cellular uptake. In the genus Burkholderia, which includes several serious human pathogens, uptake of iron is critical for virulence, and expression of biosynthetic gene clusters encoding proteins involved in synthesis and transport of the primary siderophores are under control of an ECF σ factor. This review summarizes mechanisms involved in regulation of these gene clusters, including the role of global transcriptional regulators. Since siderophore-mediated iron acquisition is important for virulence, interference with this process constitutes a viable approach to the treatment of bacterial infections.
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Affiliation(s)
- Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States
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6
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Mendauletova A, Latham JA. Biosynthesis of the redox cofactor mycofactocin is controlled by the transcriptional regulator MftR and induced by long-chain acyl-CoA species. J Biol Chem 2021; 298:101474. [PMID: 34896395 PMCID: PMC8728441 DOI: 10.1016/j.jbc.2021.101474] [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: 09/14/2021] [Revised: 11/30/2021] [Accepted: 12/01/2021] [Indexed: 11/11/2022] Open
Abstract
Mycofactocin (MFT) is a ribosomally synthesized and post-translationally-modified redox cofactor found in pathogenic mycobacteria. While MFT biosynthetic proteins have been extensively characterized, the physiological conditions under which MFT biosynthesis is required are not well understood. To gain insights into the mechanisms of regulation of MFT expression in Mycobacterium smegmatis mc2155, we investigated the DNA-binding and ligand-binding activities of the putative TetR-like transcription regulator, MftR. In this study, we demonstrated that MftR binds to the mft promoter region. We used DNase I footprinting to identify the 27 bp palindromic operator located 5′ to mftA and found it to be highly conserved in Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium ulcerans, and Mycobacterium marinum. To determine under which conditions the mft biosynthetic gene cluster (BGC) is induced, we screened for effectors of MftR. As a result, we found that MftR binds to long-chain acyl-CoAs with low micromolar affinities. To demonstrate that oleoyl-CoA induces the mft BGC in vivo, we re-engineered a fluorescent protein reporter system to express an MftA–mCherry fusion protein. Using this mCherry fluorescent readout, we show that the mft BGC is upregulated in M. smegmatis mc2155 when oleic acid is supplemented to the media. These results suggest that MftR controls expression of the mft BGC and that MFT production is induced by long-chain acyl-CoAs. Since MFT-dependent dehydrogenases are known to colocalize with acyl carrier protein/CoA-modifying enzymes, these results suggest that MFT might be critical for fatty acid metabolism or cell wall reorganization.
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Affiliation(s)
- Aigera Mendauletova
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, USA
| | - John A Latham
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, USA.
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7
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Thapa SS, Grove A. Impaired purine homeostasis plays a primary role in trimethoprim-mediated induction of virulence genes in Burkholderia thailandensis. Mol Microbiol 2020; 115:610-622. [PMID: 33053234 DOI: 10.1111/mmi.14626] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/08/2020] [Accepted: 10/09/2020] [Indexed: 11/27/2022]
Abstract
One of the most commonly prescribed antibiotics against Burkholderia infections is co-trimoxazole, a cocktail of trimethoprim and sulfamethoxazole. Trimethoprim elicits an upregulation of the mal gene cluster, which encodes proteins involved in synthesis of the cytotoxic polyketide malleilactone; trimethoprim does so by increasing expression of the malR gene, which encodes the activator MalR. We report that B. thailandensis grown on trimethoprim exhibited increased virulence against Caenorhabditis elegans. This enhanced virulence correlated with an increase in expression of the mal gene cluster. Notably, inhibition of xanthine dehydrogenase by addition of allopurinol led to similar upregulation of malA and malR, with addition of trimethoprim or allopurinol also resulting in an equivalent intracellular accumulation of xanthine. Xanthine is a ligand for the transcription factor MftR that leads to attenuated DNA binding, and we show using chromatin immunoprecipitation that MftR binds directly to malR. Our gene expression data suggest that malR expression is repressed by both MftR and by a separate transcription factor, which also responds to a metabolite that accumulates on exposure to trimethoprim. Since allopurinol elicits a similar increase in malR/malA expression as trimethoprim, we suggest that impaired purine homeostasis plays a primary role in trimethoprim-mediated induction of malR and in turn malA.
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Affiliation(s)
- Sudarshan S Thapa
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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8
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Secondary metabolites from the Burkholderia pseudomallei complex: structure, ecology, and evolution. J Ind Microbiol Biotechnol 2020; 47:877-887. [PMID: 33052546 DOI: 10.1007/s10295-020-02317-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 09/22/2020] [Indexed: 12/15/2022]
Abstract
Bacterial secondary metabolites play important roles in promoting survival, though few have been carefully studied in their natural context. Numerous gene clusters code for secondary metabolites in the genomes of members of the Bptm group, made up of three closely related species with distinctly different lifestyles: the opportunistic pathogen Burkholderia pseudomallei, the non-pathogenic saprophyte Burkholderia thailandensis, and the host-adapted pathogen Burkholderia mallei. Several biosynthetic gene clusters are conserved across two or all three species, and this provides an opportunity to understand how the corresponding secondary metabolites contribute to survival in different contexts in nature. In this review, we discuss three secondary metabolites from the Bptm group: bactobolin, malleilactone (and malleicyprol), and the 4-hydroxy-3-methyl-2-alkylquinolines, providing an overview of each of their biosynthetic pathways and insight into their potential ecological roles. Results of studies on these secondary metabolites provide a window into how secondary metabolites contribute to bacterial survival in different environments, from host infections to polymicrobial soil communities.
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9
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Thapa SS, Grove A. Do Global Regulators Hold the Key to Production of Bacterial Secondary Metabolites? Antibiotics (Basel) 2019; 8:antibiotics8040160. [PMID: 31547528 PMCID: PMC6963729 DOI: 10.3390/antibiotics8040160] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 12/18/2022] Open
Abstract
The emergence of multiple antibiotic resistant bacteria has pushed the available pool of antibiotics to the brink. Bacterial secondary metabolites have long been a valuable resource in the development of antibiotics, and the genus Burkholderia has recently emerged as a source of novel compounds with antibacterial, antifungal, and anti-cancer activities. Genome mining has contributed to the identification of biosynthetic gene clusters, which encode enzymes that are responsible for synthesis of such secondary metabolites. Unfortunately, these large gene clusters generally remain silent or cryptic under normal laboratory settings, which creates a hurdle in identification and isolation of these compounds. Various strategies, such as changes in growth conditions and antibiotic stress, have been applied to elicit the expression of these cryptic gene clusters. Although a number of compounds have been isolated from different Burkholderia species, the mechanisms by which the corresponding gene clusters are regulated remain poorly understood. This review summarizes the activity of well characterized secondary metabolites from Burkholderia species and the role of local regulators in their synthesis, and it highlights recent evidence for the role of global regulators in controlling production of secondary metabolites. We suggest that targeting global regulators holds great promise for the awakening of cryptic gene clusters and for developing better strategies for discovery of novel antibiotics.
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Affiliation(s)
- Sudarshan Singh Thapa
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
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10
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Gong Z, Li H, Cai Y, Stojkoska A, Xie J. Biology of MarR family transcription factors and implications for targets of antibiotics against tuberculosis. J Cell Physiol 2019; 234:19237-19248. [PMID: 31012115 DOI: 10.1002/jcp.28720] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 04/03/2019] [Accepted: 04/10/2019] [Indexed: 12/12/2022]
Abstract
The emergence of multidrug resistant (MDR) Mycobacterium tuberculosis strains and increased incidence of HIV coinfection fueled the difficulty in controlling tuberculosis (TB). MarR (multiple antibiotic resistance regulator) family transcription factors can regulate marRAB operon and are involved in resistance to multiple environmental stresses. We have summarized the structure, function, distribution, and regulation of the MarR family proteins, as well as their implications for novel targets for antibiotics, especially for tuberculosis.
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Affiliation(s)
- Zhen Gong
- Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing, China
| | - Hui Li
- Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing, China
| | - Yuhua Cai
- Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing, China
| | - Andrea Stojkoska
- Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing, China
| | - Jianping Xie
- Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing, China
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11
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Sabrin A, Gioe BW, Gupta A, Grove A. An EmrB multidrug efflux pump in Burkholderia thailandensis with unexpected roles in antibiotic resistance. J Biol Chem 2018; 294:1891-1903. [PMID: 30545940 DOI: 10.1074/jbc.ra118.006638] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/12/2018] [Indexed: 01/28/2023] Open
Abstract
The antibiotic trimethoprim is frequently used to manage Burkholderia infections, and members of the resistance-nodulation-division (RND) family of efflux pumps have been implicated in multidrug resistance of this species complex. We show here that a member of the distinct Escherichia coli multidrug resistance B (EmrB) family is a primary exporter of trimethoprim in Burkholderia thailandensis, as evidenced by increased trimethoprim sensitivity after inactivation of emrB, the gene that encodes EmrB. We also found that the emrB gene is up-regulated following the addition of gentamicin and that this up-regulation is due to repression of the gene encoding OstR, a member of the multiple antibiotic resistance regulator (MarR) family. The addition of the oxidants H2O2 and CuCl2 to B. thailandensis cultures resulted in OstR-dependent differential emrB expression, as determined by qRT-PCR analysis. Specifically, OstR functions as a rheostat that optimizes emrB expression under oxidizing conditions, and it senses oxidants by a unique mechanism involving two vicinal cysteines and one distant cysteine (Cys3, Cys4, and Cys169) per monomer. Paradoxically, emrB inactivation increased resistance of B. thailandensis to tetracycline, a phenomenon that correlated with up-regulation of an RND efflux pump. These observations highlight the intricate mechanisms by which expression of genes that encode efflux pumps is optimized depending on cellular concentrations of antibiotics and oxidants.
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Affiliation(s)
- Afsana Sabrin
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Brennan W Gioe
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Ashish Gupta
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Anne Grove
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
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12
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MarR Family Transcription Factors from Burkholderia Species: Hidden Clues to Control of Virulence-Associated Genes. Microbiol Mol Biol Rev 2018; 83:83/1/e00039-18. [PMID: 30487164 DOI: 10.1128/mmbr.00039-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Species within the genus Burkholderia exhibit remarkable phenotypic diversity. Genomic plasticity, including genome reduction and horizontal gene transfer, has been correlated with virulence traits in several species. However, the conservation of virulence genes in species otherwise considered to have limited potential for infection suggests that phenotypic diversity may not be explained solely on the basis of genetic diversity. Instead, differential organization and control of gene regulatory networks may underlie many phenotypic differences. In this review, we evaluate how regulation of gene expression by members of the multiple antibiotic resistance regulator (MarR) family of transcription factors may contribute to shaping the physiological diversity of Burkholderia species, with a focus on the clinically relevant human pathogens. All Burkholderia species encode a relatively large number of MarR proteins, a feature common to bacteria that must respond to environmental changes such as those associated with host invasion. However, evolution of gene regulatory networks has likely resulted in orthologous transcription factors controlling disparate sets of genes. Adaptation to, and survival in, diverse habitats, including a human or plant host, is key to the success of Burkholderia species as (opportunistic) pathogens, and recent reports suggest that control of virulence-associated genes by MarR proteins features prominently among the survival strategies employed by these species. We suggest that identification of MarR regulons will contribute significantly to clarification of virulence determinants and phenotypic diversity.
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13
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Capdevila DA, Huerta F, Edmonds KA, Le MT, Wu H, Giedroc DP. Tuning site-specific dynamics to drive allosteric activation in a pneumococcal zinc uptake regulator. eLife 2018; 7:37268. [PMID: 30328810 PMCID: PMC6224198 DOI: 10.7554/elife.37268] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 10/16/2018] [Indexed: 11/25/2022] Open
Abstract
MarR (multiple antibiotic resistance repressor) family proteins are bacterial repressors that regulate transcription in response to a wide range of chemical signals. Although specific features of MarR family function have been described, the role of atomic motions in MarRs remains unexplored thus limiting insights into the evolution of allostery in this ubiquitous family of repressors. Here, we provide the first experimental evidence that internal dynamics play a crucial functional role in MarR proteins. Streptococcus pneumoniae AdcR (adhesin-competence repressor) regulates ZnII homeostasis and ZnII functions as an allosteric activator of DNA binding. ZnII coordination triggers a transition from somewhat independent domains to a more compact structure. We identify residues that impact allosteric activation on the basis of ZnII-induced perturbations of atomic motions over a wide range of timescales. These findings appear to reconcile the distinct allosteric mechanisms proposed for other MarRs and highlight the importance of conformational dynamics in biological regulation.
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Affiliation(s)
| | - Fidel Huerta
- Department of Chemistry, Indiana University, Bloomington, United States.,Graduate Program in Biochemistry, Indiana University, Bloomington, United States
| | | | - My Tra Le
- Department of Chemistry, Indiana University, Bloomington, United States
| | - Hongwei Wu
- Department of Chemistry, Indiana University, Bloomington, United States
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, United States.,Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, United States
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14
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Konasani VR, Jin C, Karlsson NG, Albers E. A novel ulvan lyase family with broad-spectrum activity from the ulvan utilisation loci of Formosa agariphila KMM 3901. Sci Rep 2018; 8:14713. [PMID: 30279430 PMCID: PMC6168547 DOI: 10.1038/s41598-018-32922-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 09/17/2018] [Indexed: 11/19/2022] Open
Abstract
Ulvan, which is one of the major structural polysaccharides of the cell walls of green macroalgae, is degraded by ulvan lyases via the β-elimination mechanism with the release of oligosaccharides that have unsaturated 4-deoxy-L-threo-hex-4-enopyranosiduronic acid (∆) at the non-reducing end. These ulvan lyases belong to the PL24 or PL25 or PL28 family in the CAZy database. In this study, we identify and biochemically characterise a periplasmic novel broad-spectrum ulvan lyase from Formosa agariphila KMM 3901. The lyase was overexpressed in Escherichia coli, and the purified recombinant enzyme depolymerised ulvan in an endolytic manner with a Km of 0.77 mg/ml, and displayed optimum activity at 40 °C and pH 8. This lyase also degraded heparan sulphate and chondroitin sulphate. Detailed analyses of the end-products of the enzymatic degradation of ulvan using 1H- and 13C-NMR and LC-MS revealed an unsaturated disaccharide (∆Rha3S) and a tetrasaccharide (∆Rha3S-Xyl-Rha) as the principal end-products. In contrast to the previously described ulvan lyases, this novel lyase is mostly composed of α-helices that form an (α/α)6 incomplete toroid domain and displays a remarkably broad-spectrum activity. This novel lyase is the first member of a new family of ulvan lyases.
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Affiliation(s)
- Venkat Rao Konasani
- Industrial Biotechnology Division, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Chunsheng Jin
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Niclas G Karlsson
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Eva Albers
- Industrial Biotechnology Division, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
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15
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The 3-D structure of VNG0258H/RosR - A haloarchaeal DNA-binding protein in its ionic shell. J Struct Biol 2018; 204:191-198. [PMID: 30110657 DOI: 10.1016/j.jsb.2018.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 08/05/2018] [Accepted: 08/09/2018] [Indexed: 11/21/2022]
Abstract
Protein-DNA interactions are highly dependent on salt concentration. To gain insight into how such interactions are maintained in the highly saline cytoplasm of halophilic archaea, we determined the 3-D structure of VNG0258H/RosR, the first haloarchaeal DNA-binding protein from the extreme halophilic archaeon Halobactrium salinarum. It is a dimeric winged-helix-turn-helix (wHTH) protein with unique features due to adaptation to the halophilic environment. As ions are major players in DNA binding processes, particularly in halophilic environments, we investigated the solution structure of the ionic envelope and located anions in the first shell around the protein in the crystal using anomalous scattering. Anions that were found to be tightly bound to residues in the positively charged DNA-binding site would probably be released upon DNA binding and will thus make significant contribution to the driving force of the binding process. Unexpectedly, ions were also found in a buried internal cavity connected to the external medium by a tunnel. Our structure lays a solid groundwork for future structural, computational and biochemical studies on complexes of the protein with cognate DNA sequences, with implications to protein-DNA interactions in hyper-saline environments.
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16
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Losada L, Shea AA, DeShazer D. A MarR family transcriptional regulator and subinhibitory antibiotics regulate type VI secretion gene clusters in Burkholderia pseudomallei. MICROBIOLOGY-SGM 2018; 164:1196-1211. [PMID: 30052173 DOI: 10.1099/mic.0.000697] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Burkholderia pseudomallei, the aetiological agent of melioidosis, is an inhabitant of soil and water in many tropical and subtropical regions worldwide. It possesses six distinct type VI secretion systems (T6SS-1 to T6SS-6), but little is known about most of them, as they are poorly expressed in laboratory culture media. A genetic screen was devised to locate a putative repressor of the T6SS-2 gene cluster and a MarR family transcriptional regulator, termed TctR, was identified. The inactivation of tctR resulted in a 50-fold increase in the expression of an hcp2-lacZ transcriptional fusion, indicating that TctR is a negative regulator of the T6SS-2 gene cluster. Surprisingly, the tctR mutation resulted in a significant decrease in the expression of an hcp6-lacZ transcriptional fusion. B. pseudomallei K96243 and a tctR mutant were grown to logarithmic phase in rich culture medium and RNA was isolated and sequenced in order to identify other genes regulated by TctR. The results identified seven gene clusters that were repressed by TctR, including T6SS-2, and three gene clusters that were significantly activated. A small molecule library consisting of 1120 structurally defined compounds was screened to identify a putative ligand (or ligands) that might bind TctR and derepress transcription of the T6SS-2 gene cluster. Seven compounds, six fluoroquinolones and one quinolone, activated the expression of hcp2-lacZ. Subinhibitory ciprofloxacin also increased the expression of the T6SS-3, T6SS-4 and T6SS-6 gene clusters. This study highlights the complex layers of regulatory control that B. pseudomallei utilizes to ensure that T6SS expression only occurs under very defined environmental conditions.
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Affiliation(s)
- Liliana Losada
- 1J. Craig Venter Institute, Rockville, MD, USA.,†Present address: Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases, Rockville, MD, USA
| | - April A Shea
- 2Diagnostic Systems Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD, USA.,‡Present address: National Strategic Research Institute, Annapolis Junction, MD, USA
| | - David DeShazer
- 3Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD, USA
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Gupta A, Bedre R, Thapa SS, Sabrin A, Wang G, Dassanayake M, Grove A. Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis. ACS Chem Biol 2017; 12:3012-3021. [PMID: 29087175 DOI: 10.1021/acschembio.7b00681] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Many bacteria encode biosynthetic proteins that produce a vast array of natural products. These compounds are often synthesized during host invasion as they function as virulence factors. In addition, such secondary metabolites have yielded numerous molecular scaffolds with pharmaceutical and clinical importance. The gene clusters that encode proteins responsible for synthesis of these compounds are typically silenced or "cryptic" under laboratory growth conditions, hampering discovery of novel lead compounds. We report here that MftR is a global repressor of secondary metabolite synthesis in Burkholderia thailandensis and that urate functions as a physiologically relevant inducer of gene expression. Biosynthetic gene clusters under MftR control include those associated with production of the antimicrobial bactobolins, the iron siderophore malleobactin, and the virulence factor malleilactone. MftR also controls additional genes associated with survival in a host environment, such as genes encoding components of the type III secretion system (T3SS) and proteins linked to anaerobic respiration. This observation not only has implications for understanding activation of gene regulatory networks during host invasion, but it also paves the way for isolation of novel therapeutic leads.
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Affiliation(s)
- Ashish Gupta
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Renesh Bedre
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudarshan Singh Thapa
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Afsana Sabrin
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Guannan Wang
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Maheshi Dassanayake
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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18
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Structural analysis of the regulatory mechanism of MarR protein Rv2887 in M. tuberculosis. Sci Rep 2017; 7:6471. [PMID: 28743871 PMCID: PMC5526998 DOI: 10.1038/s41598-017-01705-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/30/2017] [Indexed: 11/20/2022] Open
Abstract
MarR family proteins are transcriptional regulators that control expression of bacterial proteins involved in metabolism, virulence, stress responses and multi-drug resistance, mainly via ligand-mediated attenuation of DNA binding. Greater understanding of their underlying regulatory mechanism may open up new avenues for the effective treatment of bacterial infections. To gain molecular insight into the mechanism of Rv2887, a MarR family protein in M. tuberculosis, we first showed that it binds salicylate (SA) and para-aminosalicylic acid (PAS), its structural analogue and an antitubercular drug, in a 1:1 stoichiometry with high affinity. Subsequent determination and analysis of Rv2887 crystal structures in apo form, and in complex with SA, PAS and DNA showed that SA and PAS bind to Rv2887 at similar sites, and that Rv2887 interacts with DNA mainly by insertion of helix α4 into the major groove. Ligand binding triggers rotation of the wHTH domain of Rv2887 toward the dimerization domain, causing changes in protein conformation such that it can no longer bind to a 27 bp recognition sequence in the upstream region of gene Rv0560c. The structures provided here lay a foundation for the design of small molecules that target Rv2887, a potential new approach for the development of anti-mycobacterials.
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Deochand DK, Perera IC, Crochet RB, Gilbert NC, Newcomer ME, Grove A. Histidine switch controlling pH-dependent protein folding and DNA binding in a transcription factor at the core of synthetic network devices. MOLECULAR BIOSYSTEMS 2017; 12:2417-26. [PMID: 27282811 DOI: 10.1039/c6mb00304d] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Therapeutic strategies have been reported that depend on synthetic network devices in which a urate-sensing transcriptional regulator detects pathological levels of urate and triggers production or release of urate oxidase. The transcription factor involved, HucR, is a member of the multiple antibiotic resistance (MarR) protein family. We show that protonation of stacked histidine residues at the pivot point of long helices that form the scaffold of the dimer interface leads to reversible formation of a molten globule state and significantly attenuated DNA binding at physiological temperatures. We also show that binding of urate to symmetrical sites in each protein lobe is communicated via the dimer interface. This is the first demonstration of regulation of a MarR family transcription factor by pH-dependent interconversion between a molten globule and a compact folded state. Our data further suggest that HucR may be utilized in synthetic devices that depend on detection of pH changes.
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Affiliation(s)
- D K Deochand
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - I C Perera
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - R B Crochet
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - N C Gilbert
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - M E Newcomer
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - A Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
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20
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Deochand DK, Grove A. MarR family transcription factors: dynamic variations on a common scaffold. Crit Rev Biochem Mol Biol 2017; 52:595-613. [PMID: 28670937 DOI: 10.1080/10409238.2017.1344612] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Members of the multiple antibiotic resistance regulator (MarR) family of transcription factors are critical for bacterial cells to respond to chemical signals and to convert such signals into changes in gene activity. Obligate dimers belonging to the winged helix-turn-helix protein family, they are critical for regulation of a variety of functions, including degradation of organic compounds and control of virulence gene expression. The conventional regulatory paradigm is based on a genomic locus in which the gene encoding the MarR protein is divergently oriented from a gene under its control; MarR binding to the intergenic region controls expression of both genes by changing the interaction of RNA polymerase with gene promoters. MarR protein oxidation or binding of a small molecule ligand adversely affects DNA binding, resulting in altered expression of the divergent genes. The generality of this simple paradigm, including the regulation of Escherichia coli MarR by direct binding of antibiotics, has been challenged by reports published in recent years. In addition, structural and biochemical analyses of ligand binding to numerous MarR homologs are converging to identify a shared ligand-binding "hot-spot". This review highlights recent research advances that point to shared features, yet at the same time highlights the remarkable flexibility with which members of this protein family implement responses to inducing signals. A more comprehensive understanding of protein function will pave the way towards the development of both antibacterial agents and biosensors that are based on MarR family proteins.
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Affiliation(s)
- Dinesh K Deochand
- a Department of Biological Sciences , Louisiana State University , Baton Rouge , LA , USA
| | - Anne Grove
- a Department of Biological Sciences , Louisiana State University , Baton Rouge , LA , USA
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21
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Grove A. Regulation of Metabolic Pathways by MarR Family Transcription Factors. Comput Struct Biotechnol J 2017; 15:366-371. [PMID: 28694934 PMCID: PMC5487221 DOI: 10.1016/j.csbj.2017.06.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 06/05/2017] [Accepted: 06/08/2017] [Indexed: 01/24/2023] Open
Abstract
Bacteria have evolved sophisticated mechanisms for regulation of metabolic pathways. Such regulatory circuits ensure that anabolic pathways remain repressed unless final products are in short supply and that catabolic enzymes are not produced in absence of their substrates. The precisely tuned gene activity underlying such circuits is in the purview of transcription factors that may bind pathway intermediates, which in turn modulate transcription factor function and therefore gene expression. This review focuses on the role of ligand-responsive MarR family transcription factors in controlling expression of genes encoding metabolic enzymes and the mechanisms by which such control is exerted. Prospects for exploiting these transcription factors for optimization of gene expression for metabolic engineering and for the development of biosensors are considered.
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Affiliation(s)
- Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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22
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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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23
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Gupta A, Fuentes SM, Grove A. Redox-Sensitive MarR Homologue BifR from Burkholderia thailandensis Regulates Biofilm Formation. Biochemistry 2017; 56:2315-2327. [PMID: 28406615 DOI: 10.1021/acs.biochem.7b00103] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biofilm formation by pathogenic Burkholderia species is a serious complication as it renders the bacteria resistant to antibiotics and host defenses. Using B. thailandensis, we report here a novel redox-sensitive member of the multiple antibiotic resistance regulator (MarR) protein family, BifR, which represses biofilm formation. BifR is encoded as part of the emrB-bifR operon; emrB-bifR is divergent to ecsC, which encodes a putative LasA protease. In Pseudomonas aeruginosa, LasA has been implicated in virulence by contributing to cleavage of elastase. BifR repressed the expression of ecsC and emrB-bifR, and expression was further repressed under oxidizing conditions. BifR bound two sites in the intergenic region between ecsC and emrB-bifR with nanomolar affinity under both reducing and oxidizing conditions; however, oxidized BifR formed a disulfide-linked dimer-of-dimers, a covalent linkage that was absent in BifR-C104A in which the redox-active cysteine was replaced with alanine. BifR also repressed an operon encoding enzymes required for synthesis of phenazine antibiotics, which function as alternate respiratory electron receptors, and inactivation of bifR resulted in enhanced biofilm formation. Taken together, our data suggest that BifR functions to control LasA production and expression of genes involved in biofilm formation, in part by regulating synthesis of alternate electron acceptors that promote survival in the oxygen-limiting environment of a biofilm. The correlation between increased repression of emrB-bifR under oxidative conditions and the formation of a covalently linked BifR dimer-of-dimers suggests that BifR may modulate gene activity in response to cellular redox state.
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Affiliation(s)
- Ashish Gupta
- Department of Biological Sciences, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Stanley M Fuentes
- Department of Biological Sciences, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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24
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Anandapadamanaban M, Pilstål R, Andresen C, Trewhella J, Moche M, Wallner B, Sunnerhagen M. Mutation-Induced Population Shift in the MexR Conformational Ensemble Disengages DNA Binding: A Novel Mechanism for MarR Family Derepression. Structure 2016; 24:1311-1321. [DOI: 10.1016/j.str.2016.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 05/20/2016] [Accepted: 06/05/2016] [Indexed: 12/01/2022]
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25
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Deochand DK, Meariman JK, Grove A. pH-Dependent DNA Distortion and Repression of Gene Expression by Pectobacterium atrosepticum PecS. ACS Chem Biol 2016; 11:2049-56. [PMID: 27213700 DOI: 10.1021/acschembio.6b00168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Transcriptional activity is exquisitely sensitive to changes in promoter DNA topology. Transcription factors may therefore control gene activity by modulating the relative positioning of -10 and -35 promoter elements. The plant pathogen Pectobacterium atrosepticum, which causes soft rot in potatoes, must alter gene expression patterns to ensure growth in planta. In the related soft-rot enterobacterium Dickeya dadantii, PecS functions as a master regulator of virulence gene expression. Here, we report that P. atrosepticum PecS controls gene activity by altering promoter DNA topology in response to pH. While PecS binds the pecS promoter with high affinity regardless of pH, it induces significant DNA distortion only at neutral pH, the pH at which the pecS promoter is repressed in vivo. At pH ∼8, DNA distortions are attenuated, and PecS no longer represses the pecS promoter. A specific histidine (H142) located in a crevice between the dimerization- and DNA-binding regions is required for pH-dependent changes in DNA distortion and repression of gene activity, and mutation of this histidine renders the mutant protein incapable of repressing the pecS promoter. We propose that protonated PecS induces a DNA conformation at neutral pH in which -10 and -35 promoter elements are suboptimally positioned for RNA polymerase binding; on deprotonation of PecS, binding is no longer associated with significant changes in DNA conformation, allowing gene expression. We suggest that this mode of gene regulation leads to differential expression of the PecS regulon in response to alkalinization of the plant apoplast.
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Affiliation(s)
- Dinesh K. Deochand
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Jacob K. Meariman
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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26
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Panday A, Inda ME, Bagam P, Sahoo MK, Osorio D, Batra S. Transcription Factor NF-κB: An Update on Intervention Strategies. Arch Immunol Ther Exp (Warsz) 2016; 64:463-483. [PMID: 27236331 DOI: 10.1007/s00005-016-0405-y] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 04/14/2016] [Indexed: 12/25/2022]
Abstract
The nuclear factor (NF)-κB family of transcription factors are ubiquitous and pleiotropic molecules that regulate the expression of more than 150 genes involved in a broad range of processes including inflammation, immunity, cell proliferation, differentiation, and survival. The chronic activation or dysregulation of NF-κB signaling is the central cause of pathogenesis in many disease conditions and, therefore, NF-κB is a major focus of therapeutic intervention. Because of this, understanding the relationship between NF-κB and the induction of various downstream signaling molecules is imperative. In this review, we provide an updated synopsis of the role of NF-κB in DNA repair and in various ailments including cardiovascular diseases, HIV infection, asthma, herpes simplex virus infection, chronic obstructive pulmonary disease, and cancer. Furthermore, we also discuss the specific targets for selective inhibitors and future therapeutic strategies.
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Affiliation(s)
- Arvind Panday
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, 70803, USA.,Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Maria Eugenia Inda
- Departamento de Microbiología, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional Rosario, Suipacha 531, Santa Fe, Argentina
| | - Prathyusha Bagam
- Laboratory of Pulmonary Immunotoxicology, Environmental Toxicology PhD Program, 207 Health Research Center, Southern University and A&M College, Baton Rouge, LA, 70813, USA
| | - Malaya K Sahoo
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, 94304, USA
| | - Diana Osorio
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Sanjay Batra
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, 70803, USA. .,Laboratory of Pulmonary Immunotoxicology, Environmental Toxicology PhD Program, 207 Health Research Center, Southern University and A&M College, Baton Rouge, LA, 70813, USA.
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27
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Blancato VS, Pagliai FA, Magni C, Gonzalez CF, Lorca GL. Functional Analysis of the Citrate Activator CitO from Enterococcus faecalis Implicates a Divalent Metal in Ligand Binding. Front Microbiol 2016; 7:101. [PMID: 26903980 PMCID: PMC4746285 DOI: 10.3389/fmicb.2016.00101] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 01/19/2016] [Indexed: 02/04/2023] Open
Abstract
The regulator of citrate metabolism, CitO, from Enterococcus faecalis belongs to the FCD family within the GntR superfamily. In the presence of citrate, CitO binds to cis-acting sequences located upstream of the cit promoters inducing the expression of genes involved in citrate utilization. The quantification of the molecular binding affinities, performed by isothermal titration calorimetry (ITC), indicated that CitO has a high affinity for citrate (KD = 1.2 ± 0.2 μM), while it did not recognize other metabolic intermediates. Based on a structural model of CitO where a putative small molecule and a metal binding site were identified, it was hypothesized that the metal ion is required for citrate binding. In agreement with this model, citrate binding to CitO sharply decreased when the protein was incubated with EDTA. This effect was reverted by the addition of Ni2+, and Zn2+ to a lesser extent. Structure-based site-directed mutagenesis was conducted and it was found that changes to alanine in residues Arg97 and His191 resulted in decreased binding affinities for citrate, as determined by EMSA and ITC. Further assays using lacZ fusions confirmed that these residues in CitO are involved in sensing citrate in vivo. These results indicate that the molecular modifications induced by a ligand and a metal binding in the C-terminal domain of CitO are required for optimal DNA binding activity, and consequently, transcriptional activation.
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Affiliation(s)
- Víctor S Blancato
- Laboratorio de Fisiología y Genética de Bacterias Lácticas, Instituto de Biología Molecular de Rosario, Consejo Nacional de Investigaciones Científicas y TécnicasRosario, Argentina; Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of FloridaGainesville, FL, USA
| | - Fernando A Pagliai
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida Gainesville, FL, USA
| | - Christian Magni
- Laboratorio de Fisiología y Genética de Bacterias Lácticas, Instituto de Biología Molecular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas Rosario, Argentina
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida Gainesville, FL, USA
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida Gainesville, FL, USA
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Pagliai FA, Gonzalez CF, Lorca GL. Identification of a Ligand Binding Pocket in LdtR from Liberibacter asiaticus. Front Microbiol 2015; 6:1314. [PMID: 26635775 PMCID: PMC4658428 DOI: 10.3389/fmicb.2015.01314] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/09/2015] [Indexed: 11/13/2022] Open
Abstract
LdtR is a transcriptional activator involved in the regulation of a putative L,D transpeptidase in Liberibacter asiaticus, an unculturable pathogen and one of the causative agents of Huanglongbing disease. Using small molecule screens we identified benzbromarone as an inhibitor of LdtR activity, which was confirmed using in vivo and in vitro assays. Based on these previous results, the objective of this work was to identify the LdtR ligand binding pocket and characterize its interactions with benzbromarone. A structural model of LdtR was constructed and the molecular interactions with the ligand were predicted using the SwissDock interface. Using site-directed mutagenesis, these residues were changed to alanine. Electrophoretic mobility shift assays, thermal denaturation, isothermal titration calorimetry experiments, and in vivo assays were used to identify residues T43, L61, and F64 in the Benz1 pocket of LdtR as the amino acids most likely involved in the binding to benzbromarone. These results provide new information on the binding mechanism of LdtR to a modulatory molecule and provide a blue print for the design of therapeutics for other members of the MarR family of transcriptional regulators involved in pathogenicity.
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Affiliation(s)
- Fernando A Pagliai
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
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29
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Abstract
Trans-aconitate methyltransferase regulator (TamR) is a member of the ligand-responsive multiple antibiotic resistance regulator (MarR) family of transcription factors. In Streptomyces coelicolor, TamR regulates transcription of tamR (encoding TamR), tam (encoding trans-aconitate methyltransferase) and sacA (encoding aconitase); up-regulation of these genes promotes metabolic flux through the citric acid cycle. DNA binding by TamR is attenuated and transcriptional derepression is achieved on binding of ligands such as citrate and trans-aconitate to TamR. In the present study, we show that three additional genes are regulated by S. coelicolor TamR. Genes encoding malate synthase (aceB1; SCO6243), malate dehydrogenase (mdh; SCO4827) and isocitrate dehydrogenase (idh; SCO7000) are up-regulated in vivo when citrate and trans-aconitate accumulate, and TamR binds the corresponding gene promoters in vitro, a DNA binding that is attenuated by cognate ligands. Mutations to the TamR binding site attenuate DNA binding in vitro and result in constitutive promoter activity in vivo. The predicted TamR binding sites are highly conserved in the promoters of these genes in Streptomyces species that encode divergent tam-tamR gene pairs, suggesting evolutionary conservation. Like aconitase and trans-aconitate methyltransferase, malate dehydrogenase, isocitrate dehydrogenase and malate synthase are closely related to the citric acid cycle, either catalysing individual reaction steps or, in the case of malate synthase, participating in the glyoxylate cycle to produce malate that enters the citric acid cycle to replenish the intermediate pool. Taken together, our data suggest that TamR plays an important and conserved role in promoting metabolic flux through the citric acid cycle.
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30
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Shu HY, Lin LC, Lin TK, Chen HP, Yang HH, Peng KC, Lin GH. Transcriptional regulation of the iac locus from Acinetobacter baumannii by the phytohormone indole-3-acetic acid. Antonie van Leeuwenhoek 2015; 107:1237-47. [PMID: 25726082 DOI: 10.1007/s10482-015-0417-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 02/24/2015] [Indexed: 11/25/2022]
Abstract
The iac locus is involved in indole-3-acetic acid (IAA) catabolism in Acinetobacter baumannii. Nine structural genes of iac are transcribed in the same direction, whereas iacR, which encodes a MarR-type transcriptional regulator, is transcribed in the opposite direction. The IacA protein, which is encoded by the second structural gene of the iac locus, is expressed in an IAA-dependent manner. Here, we characterized gene expression from this locus in wild type A. baumannii and in an iacR mutant; this revealed that the iacH promoter is negatively regulated by IacR. The transcriptional site of iacH was determined by using 5' rapid amplification of cDNA ends; one IacR-binding site was identified between positions -35 and +28 of the iacH promoter. Sequence analysis and an electrophoretic mobility shift assay indicated that recombinant IacR binds specifically to a sequence with dyad symmetry in the iacR-iacH overlapping promoters in the absence of IAA. In addition, a two-plasmid expression system in Escherichia coli showed that IAA probably serves as a ligand that binds to IacR and releases it from the iacH promoter, thereby allowing RNA polymerase to transcribe iac. Thus, iac is expressed in order to promote IAA degradation, whereas free IacR is required for iac repression. We conclude that IacR serves as a key regulator of IAA degradation in A. baumannii in the rhizosphere. These results provide new insights into the possible role of A. baumannii in the environment.
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Affiliation(s)
- Hung-Yu Shu
- Department of Bioscience Technology, Chang Jung Christian University, Tainan, 711, Taiwan
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