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Rasal TA, Mallery CP, Brockley MW, Brown LC, Paczkowski JE, van Kessel JC. Ligand binding determines proteolytic stability of Vibrio LuxR/HapR quorum sensing transcription factors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.15.580527. [PMID: 38405947 PMCID: PMC10888775 DOI: 10.1101/2024.02.15.580527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
In Vibrio species, quorum sensing signaling culminates in the production of a TetR-type master transcription factor collectively called the LuxR/HapR family, which regulates genes required for colonization and infection of host organisms. These proteins possess a solvent accessible putative ligand binding pocket. However, a native ligand has not been identified, and the role of ligand binding in LuxR/HapR function in Vibrionaceae is unknown. To probe the role of the ligand binding pocket, we utilize the small molecule thiophenesulfonamide inhibitor PTSP (3- p henyl-1-( t hiophen-2-yl s ulfonyl)-1 H - p yrazole) that we previously showed targets LuxR/HapR proteins. Amino acid conservation in the ligand binding pocket determines the specificity and efficacy of PTSP inhibition across Vibrio species. Here, we used structure-function analyses to identify PTSP-interacting residues in the ligand binding pocket of SmcR - the Vibrio vulnificus LuxR/HapR homolog - that are required for PTSP inhibition of SmcR activity in vivo . Forward genetic screening combined with X-ray crystallography structural determination of SmcR bound to PTSP identified substitutions at eight residues that were sufficient to reduce or eliminate PTSP-mediated SmcR inhibition. Small-angle X-ray scattering and computational modeling determined that PTSP drives allosteric unfolding at the N-terminal DNA binding domain. We discovered that SmcR is degraded by the ClpAP protease in the presence of PTSP in vivo ; substitution of key PTSP-interacting residues stabilized or increased SmcR levels in the cell. This mechanism of inhibition is observed for all thiophenesulfonamide compounds tested and against other Vibrio species. We conclude that thiophenesulfonamides specifically bind in the ligand binding pocket of LuxR/HapR proteins, promoting protein degradation and thereby suppressing downstream gene expression, implicating ligand binding as a mediator of LuxR/HapR protein stability and function to govern virulence gene expression in Vibrio pathogens. SIGNIFICANCE LuxR/HapR proteins were discovered in the 1990s as central regulators of quorum sensing gene expression and later discovered to be conserved in all studied Vibrio species. LuxR/HapR homologs regulate a wide range of genes involved in pathogenesis, including but not limited to genes involved in biofilm production and toxin secretion. As archetypal members of the broad class of TetR-type transcription factors, each LuxR/HapR protein has a predicted ligand binding pocket. However, no ligand has been identified for LuxR/HapR proteins that control their function as regulators. Here, we used LuxR/HapR-specific chemical inhibitors to determine that ligand binding drives proteolytic degradation in vivo , the first demonstration of LuxR/HapR function connected to ligand binding for this historical protein family.
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Wang Z, Lu K, Liu X, Zhu Y, Liu C. Comparative Functional Genome Analysis Reveals the Habitat Adaptation and Biocontrol Characteristics of Plant Growth-Promoting Bacteria in NCBI Databases. Microbiol Spectr 2023; 11:e0500722. [PMID: 37098923 PMCID: PMC10269705 DOI: 10.1128/spectrum.05007-22] [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: 12/06/2022] [Accepted: 04/03/2023] [Indexed: 04/27/2023] Open
Abstract
Plant growth-promoting bacteria (PGPB) are a group of beneficial microorganisms that include 60 bacterial genera, such as Bacillus, Pseudomonas, and Burkholderia, which widely colonize plant leaves and soil, promote plant growth, and/or inhibit pathogen infection. However, the genetic factors underpinning adaptation of PGPB to plant leaves and soil remain poorly understood. In this study, we performed a comparative functional genome analysis approach to investigate the functional genes of 195 leaf-associated (LA) and 283 soil-associated (SA) PGPB strains and their roles in adapting to their environment, using 95 strains from other-associated (OA) environmental habitats with growth-promoting or antimicrobial functions as negative controls. Comparison analysis of the enrichment of nonredundant (NR) protein sequence databases showed that cytochrome P450, DNA repair, and motor chemotaxis genes were significantly enriched in LA PGPB strains related to environmental adaptation, while cell wall-degrading enzymes, TetR transcriptional regulatory factors, and sporulation-related genes were highly enriched in SA PGPB strains. Additionally, analysis of carbohydrate-active enzymes demonstrated that glycosyltransferases (GTs) and glycoside hydrolases (GHs) were abundant families in all PGPB strains, which is in favor of plant growth, and enriched in SA PGPB strains. Except for most Bacillus strains, SA PGPB genomes contained significantly more secondary metabolism clusters than LA PGPB. Most LA PGPB contained hormone biosynthesis genes, which may contribute to plant growth promotion, while SA PGPB harbored numerous carbohydrate and antibiotic metabolism genes. In summary, this study further deepens our understanding of the habitat adaptation and biocontrol characteristics of LA and SA PGPB strains. IMPORTANCE Plant growth-promoting bacteria (PGPB) are essential for the effectiveness of biocontrol agents in plant phyllosphere and rhizosphere. However, little is known about the ecological adaptation of PGPB to different habitats. In this study, comparative functional genome analysis of leaf-associated (LA), soil-associated (SA), and other-associated (OA) PGPB strains was performed. We found that genes related to the metabolism of hormones were enriched in LA PGPB. Carbohydrate and antibiotic metabolism genes were enriched in SA PGPB, which likely facilitated their adaptation to the plant growth environment. Our findings provide genetic insights on LA and SA PGPB strains' ecological adaptation and biocontrol characteristics.
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Affiliation(s)
- Zhen Wang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Kaiheng Lu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Xuan Liu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Yuping Zhu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Changhong Liu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
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Sen H, Choudhury GB, Pawar G, Sharma Y, Bhalerao SE, Chaudhari VD, Datta S, Raychaudhuri S. Diversity in the ligand binding pocket of HapR attributes to its uniqueness towards several inhibitors with respect to other homologues - A structural and molecular perspective. Int J Biol Macromol 2023; 233:123495. [PMID: 36739058 DOI: 10.1016/j.ijbiomac.2023.123495] [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: 11/24/2022] [Revised: 01/06/2023] [Accepted: 01/28/2023] [Indexed: 02/05/2023]
Abstract
Vibrio cholerae is a prolific bacterium. Cumulative studies clearly demonstrate the key role of quorum sensing on the lifecycle of this bacterium. Of the sensory network components, HapR is known as high cell density master regulator. Until now, no information is available on native HapR ligand despite the protein having a ligand binding pocket. Interestingly, function of SmcR, a HapR homologue of Vibrio vulnificus is inhibited by a small molecule Qstatin. Structural analysis of SmcR with Qstatin identifies key interacting residues in SmcR ligand binding domain. Despite bearing significant homology with SmcR, HapR function remained unabated by Qstatin. Sequence alignment indicates divergence in the key residues of ligand binding pocket between these two regulators. A series of ligand binding domain mutants of HapR was constructed where only HapR quadruple mutant responded to Qstatin and newly synthesized IMT-VC-212. Crystal structure analysis revealed four key residues are responsible for changes in the volume of ligand binding pocket of HapR quadruple mutant compared to the wild type counterpart, thereby increasing the accessibility of Qstatin and its derivative in case of the former. The mechanistic insights exuberating from this study will remain instrumental in designing inhibitors against wild type HapR.
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Affiliation(s)
- Himanshu Sen
- CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Gourab Basu Choudhury
- CSIR-Indian Institute of Chemical Biology, Raja S C Mullick Road, Jadavpur, Kolkata 700032, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Ganesh Pawar
- CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India
| | - Yogesh Sharma
- CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | | | - Vinod D Chaudhari
- CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India..
| | - Saumen Datta
- CSIR-Indian Institute of Chemical Biology, Raja S C Mullick Road, Jadavpur, Kolkata 700032, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India..
| | - Saumya Raychaudhuri
- CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
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Midgett CR, Kull FJ. Structural Insights into Regulation of Vibrio Virulence Gene Networks. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1404:269-294. [PMID: 36792881 DOI: 10.1007/978-3-031-22997-8_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
One of the best studied aspects of pathogenic Vibrios are the virulence cascades that lead to the production of virulence factors and, ultimately, clinical outcomes. In this chapter, we will examine the regulation of Vibrio virulence gene networks from a structural and biochemical perspective. We will discuss the recent research into the numerous proteins that contribute to regulating virulence in Vibrio spp such as quorum sensing regulator HapR, the transcription factors AphA and AphB, or the virulence regulators ToxR and ToxT. We highlight how insights gained from these studies are already illuminating the basic molecular mechanisms by which the virulence cascade of pathogenic Vibrios unfold and contend that understanding how protein interactions contribute to the host-pathogen communications will enable the development of new antivirulence compounds that can effectively target these pathogens.
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Affiliation(s)
| | - F Jon Kull
- Chemistry Department, Dartmouth College, Hanover, NH, USA.
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Walker LM, Haycocks JR, van Kessel JC, Dalia TN, Dalia AB, Grainger DC. A simple mechanism for integration of quorum sensing and cAMP signalling in V. cholerae. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.08.527633. [PMID: 36798193 PMCID: PMC9934648 DOI: 10.1101/2023.02.08.527633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Many bacteria use quorum sensing to control changes in lifestyle. The process is regulated by microbially derived "autoinducer" signalling molecules, that accumulate in the local environment. Individual cells sense autoinducer abundance, to infer population density, and alter their behaviour accordingly. In Vibrio cholerae , quorum sensing signals are transduced by phosphorelay to the transcription factor LuxO. Unphosphorylated LuxO permits expression of HapR, which alters global gene expression patterns. In this work, we have mapped the genome-wide distribution of LuxO and HapR in V. cholerae . Whilst LuxO has a small regulon, HapR targets 32 loci. Many HapR targets coincide with sites for the cAMP receptor protein (CRP) that regulates the transcriptional response to carbon starvation. This overlap, also evident in other Vibrio species, results from similarities in the DNA sequence bound by each factor. At shared sites, HapR and CRP simultaneously contact the double helix and binding is stabilised by direct interaction of the two factors. Importantly, this involves a CRP surface that usually contacts RNA polymerase to stimulate transcription. As a result, HapR can block transcription activation by CRP. Thus, by interacting at shared sites, HapR and CRP integrate information from quorum sensing and cAMP signalling to control gene expression.
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Affiliation(s)
- Lucas M. Walker
- School of Biosciences, University of Birmingham, Edgbaston B15 2TT, UK
| | | | | | - Triana N. Dalia
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Ankur B. Dalia
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - David C. Grainger
- School of Biosciences, University of Birmingham, Edgbaston B15 2TT, UK,for correspondence: , Tel: +44 (0)121 414 5437
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Sequence Polymorphisms in Vibrio cholerae HapR Affect Biofilm Formation under Aerobic and Anaerobic Conditions. Appl Environ Microbiol 2022; 88:e0104422. [PMID: 35969071 PMCID: PMC9469714 DOI: 10.1128/aem.01044-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the influence of hapR sequence mutations on the biofilm formation of Vibrio cholerae. In this study, hapR sequences from 85 V. cholerae strains belonging to both pandemic and nonpandemic serogroup were investigated through phylogenetic and sequence analyses. Biofilm formation assays under aerobic and anaerobic conditions were also performed. Sequence variations include single point mutations and insertions/deletions (indels) leading to either truncated or frameshifted HapR. Population structure analysis revealed two major hapR haplogroups, hapR1 and hapR2. Phylogenetic reconstruction displayed a hypothetical ancestral hapR sequence located within the hapR1 haplogroup. Higher numbers of single nucleotide polymorphisms and genetic diversity indices were observed in hapR1, while indels occurred dominantly in hapR2. Aerobic conditions supported more robust biofilms compared to anaerobic conditions. Strains with frameshifted HapR produced the largest amount of biofilm under both oxygen conditions. Quantitative real-time PCR assay confirmed that strains with truncated and frameshifted HapR resulted in a nonfunctional regulator as exhibited by the significantly low hapA gene expression. The present study shows that HapR mutations had a strong influence on biofilm formation and that sequence polymorphisms leading to the disruption of DNA-binding sites or dimerization of the HapR will result in more-robust V. cholerae biofilms. IMPORTANCE Our study revealed an ancestral hapR sequence from a phylogenetic reconstruction that displayed the evolutionary lineage of the nonpandemic to the pandemic strains. Here, we established hapR1 and hapR2 as major hapR haplogroups. The association of the O1 and O139 serogroups with the hapR2 haplogroup demonstrated the distinction of hapR2 in causing cholera infection. Moreover, mutations in this regulator that could lead to the disruption of transcription factor-binding sites or dimerization of the HapR can significantly affect the biofilm formation of V. cholerae. These observations on the relationship of the hapR polymorphism and V. cholerae biofilm formation will provide additional considerations for future biofilm studies and insights into the epidemiology of the pathogen that could ultimately help in the surveillance and mitigation of future cholera disease outbreaks.
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Cai J, Hao Y, Xu R, Zhang Y, Ma Y, Zhang Y, Wang Q. Differential binding of LuxR in response to temperature gauges switches virulence gene expression in Vibrio alginolyticus. Microbiol Res 2022; 263:127114. [PMID: 35878491 DOI: 10.1016/j.micres.2022.127114] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 06/04/2022] [Accepted: 07/05/2022] [Indexed: 12/26/2022]
Abstract
Vibrio pathogens must cope with temperature changes for proper thermo-adaptation and virulence gene expression. LuxR is a quorum-sensing (QS) master regulator of vibrios, playing roles in response to temperature alteration. However, the molecular mechanisms how LuxR is involved in adapting to different temperatures in bacteria have not been precisely elucidated. In this study, using chromatin immunoprecipitation and nucleotide sequencing (ChIP-seq), we identified 272 and 22 enriched loci harboring LuxR-binding peaks at ambient temperature (30 ˚C) and heat shock (42 ˚C) in the Vibrio alginolyticus genome, respectively. Analysis with the MEME (multiple EM for motif elicitation) algorithm indicated that the binding motifs of LuxR varied from temperatures. Three novel binding regions (the promoter of orf00292, orf00397 and fadD) of LuxR were identified and verified that the rising temperature causes the decreasing binding affinity of LuxR to these promoters. Meanwhile, the expression of orf00292, orf00397 and fadD were regulated by LuxR. Moreover, the weak binding of LuxR to the promoter of extracellular protease (Asp) was attributed to the attenuated Asp expression at thermal stress conditions. Taken together, our study demonstrated distinct binding characteristics of LuxR in response to temperature changes, thus highlighting LuxR as a thermo-sensor to switch and control virulence gene expression in V. alginolyticus.
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Affiliation(s)
- Jingxiao Cai
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yuan Hao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Rongjing Xu
- Yantai Tianyuan Aquatic Co. Ltd., Yantai, Shandong, China
| | - Yuanxing Zhang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai 200237, China
| | - Yue Ma
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai 200237, China; Shanghai Collaborative Innovation Center for Biomanufacturing, 130 Meilong Road, Shanghai 200237, China
| | - Yibei Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai 200237, China.
| | - Qiyao Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai 200237, China; Shanghai Collaborative Innovation Center for Biomanufacturing, 130 Meilong Road, Shanghai 200237, China
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8
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Teschler JK, Nadell CD, Drescher K, Yildiz FH. Mechanisms Underlying Vibrio cholerae Biofilm Formation and Dispersion. Annu Rev Microbiol 2022; 76:503-532. [PMID: 35671532 DOI: 10.1146/annurev-micro-111021-053553] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Biofilms are a widely observed growth mode in which microbial communities are spatially structured and embedded in a polymeric extracellular matrix. Here, we focus on the model bacterium Vibrio cholerae and summarize the current understanding of biofilm formation, including initial attachment, matrix components, community dynamics, social interactions, molecular regulation, and dispersal. The regulatory network that orchestrates the decision to form and disperse from biofilms coordinates various environmental inputs. These cues are integrated by several transcription factors, regulatory RNAs, and second-messenger molecules, including bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). Through complex mechanisms, V. cholerae weighs the energetic cost of forming biofilms against the benefits of protection and social interaction that biofilms provide. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Jennifer K Teschler
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, California, USA;
| | - Carey D Nadell
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | | | - Fitnat H Yildiz
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, California, USA;
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9
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Tahir Ul Qamar M, Ahmad S, Khan A, Mirza MU, Ahmad S, Abro A, Chen LL, Almatroudi A, Wei DQ. Structural probing of HapR to identify potent phytochemicals to control Vibrio cholera through integrated computational approaches. Comput Biol Med 2021; 138:104929. [PMID: 34655900 DOI: 10.1016/j.compbiomed.2021.104929] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 10/06/2021] [Accepted: 10/06/2021] [Indexed: 01/01/2023]
Abstract
Cholera is a severe small intestine bacterial disease caused by consumption of water and food contaminated with Vibrio cholera. The disease causes watery diarrhea leading to severe dehydration and even death if left untreated. In the past few decades, V. cholerae has emerged as multidrug-resistant enteric pathogen due to its rapid ability to adapt in detrimental environmental conditions. This research study aimed to design inhibitors of a master virulence gene expression regulator, HapR. HapR is critical in regulating the expression of several set of V. cholera virulence genes, quorum-sensing circuits and biofilm formation. A blind docking strategy was employed to infer the natural binding tendency of diverse phytochemicals extracted from medicinal plants by exposing the whole HapR structure to the screening library. Scoring function criteria was applied to prioritize molecules with strong binding affinity (binding energy < -11 kcal/mol) and as such two compounds: Strychnogucine A and Galluflavanone were filtered. Both the compounds were found favourably binding to the conserved dimerization interface of HapR. One rare binding conformation of Strychnogucine A was noticed docked at the elongated cavity formed by α1, α4 and α6 (binding energy of -12.5 kcal/mol). The binding stability of both top leads at dimer interface and elongated cavity was further estimated using long run of molecular dynamics simulations, followed by MMGB/PBSA binding free energy calculations to define the dominance of different binding energies. In a nutshell, this study presents computational evidence on antibacterial potential of phytochemicals capable of directly targeting bacterial virulence and highlight their great capacity to be utilized in the future experimental studies to stop the evolution of antibiotic resistance evolution.
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Affiliation(s)
| | - Sajjad Ahmad
- Department of Health and Biological Sciences, Abasyn University, Peshawar, Pakistan
| | - Abbas Khan
- Department of Bioinformatics and Biological Statistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Muhammad Usman Mirza
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Canada
| | - Sarfraz Ahmad
- Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
| | - Asma Abro
- Department of Biotechnology, Faculty of Life Sciences and Informatics, Balochistan University of Information Technology Engineering and Management Sciences, Quetta, Pakistan
| | - Ling-Ling Chen
- College of Life Science and Technology, Guangxi University, Nanning, PR China.
| | - Ahmad Almatroudi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Dong-Qing Wei
- Department of Bioinformatics and Biological Statistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China; Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nashan District, Shenzhen, Guangdong, PR China; State Key Laboratory of Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint Laboratory of International Cooperation in Metabolic and Developmental Sciences, Ministry of Education and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China.
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10
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Newman JD, Chopra J, Shah P, Shi E, McFadden ME, Horness RE, Brown LC, van Kessel JC. Amino acid divergence in the ligand-binding pocket of Vibrio LuxR/HapR proteins determines the efficacy of thiophenesulfonamide inhibitors. Mol Microbiol 2021; 116:1173-1188. [PMID: 34468051 DOI: 10.1111/mmi.14804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 08/09/2021] [Accepted: 08/26/2021] [Indexed: 12/12/2022]
Abstract
The quorum-sensing signaling systems in Vibrio bacteria converge to control levels of the master transcription factors LuxR/HapR, a family of highly conserved proteins that regulate gene expression for bacterial behaviors. A compound library screen identified 2-thiophenesulfonamide compounds that specifically inhibit Vibrio campbellii LuxR but do not affect cell growth. We synthesized a panel of 50 thiophenesulfonamide compounds to examine the structure-activity relationship effects on Vibrio quorum sensing. The most potent molecule identified, PTSP (3-phenyl-1-(thiophen-2-ylsulfonyl)-1H-pyrazole), inhibits quorum sensing in multiple strains of V. vulnificus, V. parahaemolyticus, and V. campbellii at nanomolar concentrations. However, thiophenesulfonamide inhibition efficacy varies significantly among Vibrio species: PTSP is most inhibitory against V. vulnificus SmcR, but V. cholerae HapR is completely resistant to all thiophenesulfonamides tested. Reverse genetics experiments show that PTSP efficacy is dictated by amino acid sequence in the putative ligand-binding pocket: F75Y and C170F SmcR substitutions are each sufficient to eliminate PTSP inhibition. Further, in silico modeling distinguished the most potent thiophenesulfonamides from less-effective derivatives. Our results revealed the previously unknown differences in LuxR/HapR proteins that control quorum sensing in Vibrio species and underscore the potential for developing thiophenesulfonamides as specific quorum sensing-directed treatments for Vibrio infections.
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Affiliation(s)
- Jane D Newman
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Jay Chopra
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Priyanka Shah
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Eda Shi
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Molly E McFadden
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Rachel E Horness
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Laura C Brown
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
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Newman JD, van Kessel JC. Purification of the Vibrio Quorum-Sensing Transcription Factors LuxR, HapR, and SmcR. Methods Mol Biol 2021; 2346:173-182. [PMID: 32705543 DOI: 10.1007/7651_2020_306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
Quorum sensing is a cell density-dependent form of cellular communication among bacteria. This signaling process has been heavily studied in vibrios due to their diverse and complex phenotypes and relevance to human and aquaculture disease. Mechanistic studies of Vibrio quorum sensing have required optimization of protein purification techniques to examine the role of key proteins, such as the LuxR/HapR family of transcription factors that control quorum-sensing gene expression. Protein purification is the cornerstone of biochemistry, and it is crucial to consistently produce batches of protein that are pure, active, and concentrated to perform various assays. The methods described here are optimized for purification of the Vibrio master quorum-sensing regulators, LuxR (Vibrio harveyi), HapR (Vibrio cholerae), and SmcR (Vibrio vulnificus). We anticipate that these methods can be applied to other proteins in this family of transcription factors.
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Affiliation(s)
- Jane D Newman
- Biology Department, Indiana University, Bloomington, IN, USA
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12
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Newman JD, Russell MM, Fan L, Wang YX, Gonzalez-Gutierrez G, van Kessel JC. The DNA binding domain of the Vibrio vulnificus SmcR transcription factor is flexible and binds diverse DNA sequences. Nucleic Acids Res 2021; 49:5967-5984. [PMID: 34023896 PMCID: PMC8191795 DOI: 10.1093/nar/gkab387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 04/23/2021] [Accepted: 04/28/2021] [Indexed: 01/22/2023] Open
Abstract
Quorum sensing gene expression in vibrios is regulated by the LuxR/HapR family of transcriptional factors, which includes Vibrio vulnificus SmcR. The consensus binding site of Vibrio LuxR/HapR/SmcR proteins is palindromic but highly degenerate with sequence variations at each promoter. To examine the mechanism by which SmcR recognizes diverse DNA sites, we generated SmcR separation-of-function mutants that either repress or activate transcription but not both. SmcR N55I is restricted in recognition of single base-pair variations in DNA binding site sequences and thus is defective at transcription activation but retains interaction with RNA polymerase (RNAP) alpha. SmcR S76A, L139R and N142D substitutions disrupt the interaction with RNAP alpha but retain functional DNA binding activity. X-ray crystallography and small angle X-ray scattering data show that the SmcR DNA binding domain exists in two conformations (wide and narrow), and the protein complex forms a mixture of dimers and tetramers in solution. The three RNAP interaction-deficient variants also have two DNA binding domain conformations, whereas SmcR N55I exhibits only the wide conformation. These data support a model in which two mechanisms drive SmcR transcriptional activation: interaction with RNAP and a multi-conformational DNA binding domain that permits recognition of variable DNA sites.
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Affiliation(s)
- Jane D Newman
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, IN 47405, USA.,Department of Molecular and Cellular Biochemistry, Indiana University, 212 S Hawthorne Dr, Bloomington, IN 47405, USA
| | - Meghan M Russell
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, IN 47405, USA
| | - Lixin Fan
- Small Angle X-ray Scattering Facility, Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Yun-Xing Wang
- Small Angle X-ray Scattering Facility, Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Giovanni Gonzalez-Gutierrez
- Department of Molecular and Cellular Biochemistry, Indiana University, 212 S Hawthorne Dr, Bloomington, IN 47405, USA
| | - Julia C van Kessel
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, IN 47405, USA
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13
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Zhang J, Liu B, Gu D, Hao Y, Chen M, Ma Y, Zhou X, Reverter D, Zhang Y, Wang Q. Binding site profiles and N-terminal minor groove interactions of the master quorum-sensing regulator LuxR enable flexible control of gene activation and repression. Nucleic Acids Res 2021; 49:3274-3293. [PMID: 33693882 PMCID: PMC8034623 DOI: 10.1093/nar/gkab150] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 12/19/2022] Open
Abstract
LuxR is a TetR family master quorum sensing (QS) regulator activating or repressing expression of hundreds of genes that control collective behaviors in Vibrios with underlying mechanism unknown. To illuminate how this regulator controls expression of various target genes, we applied ChIP-seq and DNase I-seq technologies. Vibrio alginolyticus LuxR controls expression of ∼280 genes that contain either symmetric palindrome (repDNA) or asymmetric (actDNA) binding motifs with different binding profiles. The median number of LuxR binding sites for activated genes are nearly double for that of repressed genes. Crystal structures of LuxR in complex with the respective repDNA and actDNA motifs revealed a new mode of LuxR DNA binding that involves contacts of its N-terminal extension to the minor groove. The N-terminal contacts mediated by Arginine-9 and Arginine-11 differ when LuxR binds to repDNA vs actDNA, leading to higher binding affinity at repressed targets. Moreover, modification of LuxR binding sites, binding profiles, and N-terminal extension have important consequences on QS-regulated phenotypes. These results facilitate fundamental understanding of the high flexibility of mechanisms of LuxR control of gene activation and repression in Vibrio QS, which may facilitate to design QS inhibiting chemicals that interfere with LuxR regulation to effectively control pathogens.
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Affiliation(s)
| | | | | | - Yuan Hao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Mo Chen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yue Ma
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xiaohui Zhou
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269, USA
| | - David Reverter
- Correspondence may also be addressed to David Reverter. Tel: +34 93 5868955;
| | - Yuanxing Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), 519000 Zhuhai, China
- Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, China
| | - Qiyao Wang
- To whom correspondence should be addressed. Tel: +86 21 64253306;
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14
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Ekka M, Mondal A, Singh R, Sen H, Datta S, Raychaudhuri S. Arginine 37 of Glycine Linker Dictates Regulatory Function of HapR. Front Microbiol 2020; 11:1949. [PMID: 32973706 PMCID: PMC7472637 DOI: 10.3389/fmicb.2020.01949] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 07/24/2020] [Indexed: 12/14/2022] Open
Abstract
HapR is designated as a high cell density quorum sensing master regulatory protein of Vibrio cholerae. It is a member of the TetR family protein and functions both as an activator and a repressor by directly communicating with cognate promoters, thus controlling the expression of a plethora of genes in a density-dependent manner. Molecular insights reveal the domain architecture and further unveil the significance of a cross talk between the DNA binding domain and the dimerization domain for the functionality of the wild-type protein. The DNA binding domain is made up of three α-helices, where a helix-turn-helix motif spans between the helices α2 and α3. The essentiality of the glycine-rich linker linking helices α1 and α2 came into prominence while unraveling the molecular basis of a natural non-functional variant of HapR. Subsequently, the importance of linker length was demonstrated. The present study, involving a series of biochemical analyses coupled with molecular dynamics simulation, has illustrated the indispensability of a critical arginine within the linker at position 37 contributing to HapR–DNA binding activity.
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Affiliation(s)
- Manjula Ekka
- Council of Scientific and Industrial Research (CSIR), Institute of Microbial Technology, Chandigarh, India
| | - Abhisek Mondal
- Council of Scientific and Industrial Research (CSIR), Indian Institute of Chemical Biology, Kolkata, India
| | - Richa Singh
- Council of Scientific and Industrial Research (CSIR), Institute of Microbial Technology, Chandigarh, India
| | - Himanshu Sen
- Council of Scientific and Industrial Research (CSIR), Institute of Microbial Technology, Chandigarh, India
| | - Saumen Datta
- Council of Scientific and Industrial Research (CSIR), Indian Institute of Chemical Biology, Kolkata, India
| | - Saumya Raychaudhuri
- Council of Scientific and Industrial Research (CSIR), Institute of Microbial Technology, Chandigarh, India
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15
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Xu G. Evolution of LuxR solos in bacterial communication: receptors and signals. Biotechnol Lett 2019; 42:181-186. [PMID: 31732826 DOI: 10.1007/s10529-019-02763-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Accepted: 11/11/2019] [Indexed: 12/14/2022]
Abstract
Cell-cell communication in bacteria needs chemical signals and cognate receptors. Many Gram-negative bacteria use acyl-homoserine lactones (AHLs) and cognate LuxR-type receptors to regulate their quorum sensing (QS) systems. The signal synthase-receptor (LuxI-LuxR) pairs may have co-evolved together. However, many LuxR solo (orphan LuxR) regulators sense more signals than just AHLs, and expand the regulatory networks for inter-species and inter-kingdom communication. Moreover, there are also some QS regulators from the TetR family. LuxR solo regulators might have evolved by gene duplication and horizontal gene transfer. An increased understanding of the evolutionary roles of QS regulators would be helpful for engineering of cell-cell communication circuits in bacteria.
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Affiliation(s)
- Gangming Xu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
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16
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Ball AS, van Kessel JC. The master quorum-sensing regulators LuxR/HapR directly interact with the alpha subunit of RNA polymerase to drive transcription activation in Vibrio harveyi and Vibrio cholerae. Mol Microbiol 2019; 111:1317-1334. [PMID: 30742725 DOI: 10.1111/mmi.14223] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2019] [Indexed: 12/19/2022]
Abstract
In Vibrio species, quorum sensing controls gene expression for numerous group behaviors, including bioluminescence production, biofilm formation, virulence factor secretion systems, and competence. The LuxR/HapR master quorum-sensing regulators activate expression of hundreds of genes in response to changes in population densities. The mechanism of transcription activation by these TetR-type transcription factors is unknown, though LuxR DNA binding sites that lie in close proximity to the -35 region of the promoter are required for activation at some promoters. Here, we show that Vibrio harveyi LuxR directly interacts with RNA polymerase to activate transcription of the luxCDABE bioluminescence genes. LuxR interacts with RNA polymerase in vitro and in vivo and specifically interacts with both the N- and C-terminal domains of the RNA polymerase α-subunit. Amino acid substitutions in the RNAP interaction domain on LuxR decrease interactions between LuxR and the α-subunit and result in defects in transcription activation of quorum-sensing genes in vivo. The RNAP-LuxR interaction domain is conserved in Vibrio cholerae HapR and is required for activation of the HapR-regulated gene hapA. Our findings support a model in which LuxR/HapR bind proximally to RNA polymerase to drive transcription initiation at a subset of quorum-sensing genes in Vibrio species.
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Affiliation(s)
- Alyssa S Ball
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
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17
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Cruite J, Succo P, Raychaudhuri S, Kull FJ. Crystal structure of an inactive variant of the quorum-sensing master regulator HapR from the protease-deficient non-O1, non-O139 Vibrio cholerae strain V2. Acta Crystallogr F Struct Biol Commun 2018; 74:331-336. [PMID: 29870016 PMCID: PMC5987740 DOI: 10.1107/s2053230x18006519] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 04/27/2018] [Indexed: 11/10/2022] Open
Abstract
HapR is a TetR-family transcriptional regulator that controls quorum sensing in Vibrio cholerae, the causative agent of cholera. HapR regulates the expression of hemagglutinin protease, virulence and biofilm genes. The crystal structure of wild-type HapR from V. cholerae strain O1 El Tor C6706 has previously been solved. In this study, the structure of a DNA-binding-deficient variant of HapR (HapRV2) derived from the protease-deficient V. cholerae serotype O37 strain V2 is reported. The structure reveals no structural differences compared with wild-type HapR. However, structural alignment of HapRV2 with the TetR-family member QacR in complex with its operator DNA suggests that the aspartate residue located between the regulatory and DNA-binding domains may clash with and electrostatically repel the phosphate backbone of DNA to prevent binding.
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Affiliation(s)
- Justin Cruite
- Department of Biochemistry, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
| | - Patrick Succo
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Saumya Raychaudhuri
- Institute of Microbial Technology, Chandigarh, Council of Scientific and Industrial Research, Chandigarh 160 036, India
| | - F. Jon Kull
- Department of Biochemistry, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire, USA
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Yan L, Tang Q, Guan Z, Pei K, Zou T, He J. Structural insights into operator recognition by BioQ in the Mycobacterium smegmatis biotin synthesis pathway. Biochim Biophys Acta Gen Subj 2018; 1862:1843-1851. [PMID: 29852200 DOI: 10.1016/j.bbagen.2018.05.015] [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: 11/10/2017] [Revised: 04/18/2018] [Accepted: 05/19/2018] [Indexed: 10/14/2022]
Abstract
BACKGROUND Biotin is an essential cofactor in living organisms. The TetR family transcriptional regulator (TFTR) BioQ is the main regulator of biotin synthesis in Mycobacterium smegmatis. BioQ represses the expression of its target genes by binding to a conserved palindromic DNA sequence (the BioQ operator). However, the mechanism by which BioQ recognizes this DNA element has not yet been fully elucidated. METHODS/RESULTS We solved the crystal structures of the BioQ homodimer in its apo-form and in complex with its specific operator at 2.26 Å and 2.69 Å resolution, respectively. BioQ inserts the N-terminal recognition helix of each protomer into the corresponding major grooves of its operator and stabilizes the formation of the complex via electrostatic interactions and hydrogen bonding to induce conformational changes in both the DNA and BioQ. The DNA interface of BioQ is rich in positively charged residues, which help BioQ stabilize DNA binding. We elucidated the structural basis of DNA recognition by BioQ for the first time and identified the amino acid residues responsible for DNA binding via further site-directed mutagenesis. GENERAL SIGNIFICANCE Our findings clearly elucidate the mechanism by which BioQ recognizes its operator in the biotin synthesis pathway and reveal the unique structural characteristics of BioQ that are distinct from other TFTR members.
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Affiliation(s)
- Ling Yan
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Qing Tang
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China; State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Zeyuan Guan
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China; National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Kai Pei
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Tingting Zou
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China.
| | - Jin He
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China; State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei 430070, China.
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19
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Abstract
Pathogenic Vibrio species cause diseases in diverse marine animals reared in aquaculture. Since their pathogenesis, persistence, and survival in marine environments are regulated by quorum sensing (QS), QS interference has attracted attention as a means to control these bacteria in aquatic settings. A few QS inhibitors of Vibrio species have been reported, but detailed molecular mechanisms are lacking. Here, we identified a novel, potent, and selective Vibrio QS inhibitor, named QStatin [1-(5-bromothiophene-2-sulfonyl)-1H-pyrazole], which affects Vibrio harveyi LuxR homologues, the well-conserved master transcriptional regulators for QS in Vibrio species. Crystallographic and biochemical analyses showed that QStatin binds tightly to a putative ligand-binding pocket in SmcR, the LuxR homologue in V. vulnificus, and changes the flexibility of the protein, thereby altering its transcription regulatory activity. Transcriptome analysis revealed that QStatin results in SmcR dysfunction, affecting the expression of SmcR regulon required for virulence, motility/chemotaxis, and biofilm dynamics. Notably, QStatin attenuated representative QS-regulated phenotypes in various Vibrio species, including virulence against the brine shrimp (Artemia franciscana). Together, these results provide molecular insights into the mechanism of action of an effective, sustainable QS inhibitor that is less susceptible to resistance than other antimicrobial agents and useful in controlling the virulence of Vibrio species in aquacultures.IMPORTANCE Yields of aquaculture, such as penaeid shrimp hatcheries, are greatly affected by vibriosis, a disease caused by pathogenic Vibrio infections. Since bacterial cell-to-cell communication, known as quorum sensing (QS), regulates pathogenesis of Vibrio species in marine environments, QS inhibitors have attracted attention as alternatives to conventional antibiotics in aquatic settings. Here, we used target-based high-throughput screening to identify QStatin, a potent and selective inhibitor of V. harveyi LuxR homologues, which are well-conserved master QS regulators in Vibrio species. Structural and biochemical analyses revealed that QStatin binds tightly to a putative ligand-binding pocket on SmcR, the LuxR homologue in V. vulnificus, and affects expression of QS-regulated genes. Remarkably, QStatin attenuated diverse QS-regulated phenotypes in various Vibrio species, including pathogenesis against brine shrimp, with no impact on bacterial viability. Taken together, the results suggest that QStatin may be a sustainable antivibriosis agent useful in aquacultures.
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20
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Abstract
The coordination of group behaviors in bacteria is accomplished via the cell-cell signaling process called quorum sensing. Vibrios have historically been models for studying bacterial communication due to the diverse and remarkable behaviors controlled by quorum sensing in these bacteria, including bioluminescence, type III and type VI secretion, biofilm formation, and motility. Here, we discuss the Vibrio LuxR/HapR family of proteins, the master global transcription factors that direct downstream gene expression in response to changes in cell density. These proteins are structurally similar to TetR transcription factors but exhibit distinct biochemical and genetic features from TetR that determine their regulatory influence on the quorum sensing gene network. We review here the gene groups regulated by LuxR/HapR and quorum sensing and explore the targets that are common and unique among Vibrio species.
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21
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Rajamanikandan S, Jeyakanthan J, Srinivasan P. Discovery of potent inhibitors targeting Vibrio harveyi LuxR through shape and e-pharmacophore based virtual screening and its biological evaluation. Microb Pathog 2016; 103:40-56. [PMID: 27939874 DOI: 10.1016/j.micpath.2016.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 11/29/2016] [Accepted: 12/05/2016] [Indexed: 01/12/2023]
Abstract
Quorum sensing is widely recognized as an efficient mechanism in the regulation and production of several virulence factors, biofilm formation and stress responses. For this reason, quorum sensing circuit is emerging as a novel drug target for the development of anti-infective. Recently, cinnamaldehyde derivatives have been found to interfere with master quorum sensing transcriptional regulator and thereby decreasing the DNA binding ability of LuxR. However, the exact mode of cinnamaldehyde binding with LuxR and receptor interaction still remains inconclusive. In the current study, combined method of molecular docking and molecular dynamics simulations were performed to investigate the binding mode, dynamic and energy aspects of cinnamaldehyde derivatives into the binding site of LuxR. Based on the experimental and computational evidences, LuxR-3,4-dichloro-cinnamaldehyde complex was chosen for the development of e-pharmacophore model. Further, shape and e-pharmacophore based virtual screening were performed against ChemBridge database to find potent and suitable ligands for LuxR. By comparing the results of shape and e-pharmacophore based virtual screening; best 9 hit molecules were selected for further studies including ADMET prediction, molecular dynamics simulations and Prime MM-GBSA calculations. From the 9 hit molecules, the top most compound 3-(2,4-dichlorophenyl)-1-(1H-pyrrol-2-yl)-2-propen-1-one (ChemBridge-7364106) was selected for in vitro assays using Vibrio harveyi. The result revealed that ChemBridge-7364106 significantly reduced the bioluminescence production in a dose dependent manner. In addition, ChemBridge-7364106 showed a significant inhibition in biofilm formation and motility in V. harveyi. The results from the study suggest that ChemBridge-7364106 could serve as an anti-quorum sensing molecule for V. harveyi.
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Affiliation(s)
- Sundaraj Rajamanikandan
- Department of Bioinformatics, Science campus Alagappa University, Karaikudi, Tamilnadu, India
| | - Jeyaraman Jeyakanthan
- Department of Bioinformatics, Science campus Alagappa University, Karaikudi, Tamilnadu, India
| | - Pappu Srinivasan
- Department of Animal Health and Management, Science campus Alagappa University, Karaikudi, Tamilnadu, India.
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22
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Xu GM. Relationships between the Regulatory Systems of Quorum Sensing and Multidrug Resistance. Front Microbiol 2016; 7:958. [PMID: 27379084 PMCID: PMC4909744 DOI: 10.3389/fmicb.2016.00958] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/02/2016] [Indexed: 11/23/2022] Open
Abstract
Cell–cell communications, known as quorum sensing (QS) in bacteria, involve the signal molecules as chemical languages and the corresponding receptors as transcriptional regulators. In Gram-negative bacteria, orphan LuxR receptors recognize signals more than just acylhomoserine lactones, and modulate interspecies and interkingdom communications. Whereas, in the Gram-positive Streptomyces, pseudo gamma-butyrolactones (GBLs) receptors bind antibiotics other than GBL signals, and coordinate antibiotics biosynthesis. By interacting with structurally diverse molecules like antibiotics, the TetR family receptors regulate multidrug resistance (MDR) by controlling efflux pumps. Antibiotics at subinhibitory concentration may act as signal molecules; while QS signals also have antimicrobial activity at high concentration. Moreover, the QS and MDR systems may share the same exporters to transport molecules. Among these orphan LuxR, pseudo GBL receptors, and MDR regulators, although only with low sequence homology, they have some structure similarity and function correlation. Therefore, perhaps there might be evolutionary relationship and biological relevance between the regulatory systems of QS and MDR. Since the QS systems become new targets for antimicrobial strategy, it would expand our understanding about the evolutionary history of these regulatory systems.
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Affiliation(s)
- Gang-Ming Xu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences Qingdao, China
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23
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Chaparian RR, Olney SG, Hustmyer CM, Rowe-Magnus DA, van Kessel JC. Integration host factor and LuxR synergistically bind DNA to coactivate quorum-sensing genes in Vibrio harveyi. Mol Microbiol 2016; 101:823-40. [PMID: 27191515 DOI: 10.1111/mmi.13425] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/2016] [Indexed: 11/30/2022]
Abstract
The cell-cell signaling process called quorum sensing allows bacteria to control behaviors in response to changes in population density. In Vibrio harveyi, the master quorum-sensing transcription factor LuxR is a member of the TetR family of transcription factors that both activates and represses genes to coordinate group behaviors, including bioluminescence. Here, we show that integration host factor (IHF) is a key coactivator of the luxCDABE bioluminescence genes that is required together with LuxR for precise timing and expression levels of bioluminescence during quorum sensing. IHF binds to multiple sites in the luxCDABE promoter and bends the DNA in vitro. IHF and LuxR synergistically bind luxCDABE promoter DNA at overlapping, essential binding sites that are required for maximal gene expression in vivo. RNA-seq analysis demonstrated that IHF regulates 300 genes in V. harveyi, and among these are a core set of 19 genes that are also directly bound and regulated by LuxR. We validated these global analyses by demonstrating that both IHF and LuxR are required for transcriptional activation of the osmotic stress response genes betIBA-proXWV. These data suggest that IHF plays an integral role in one mechanism of transcriptional activation by the LuxR-type family of quorum-sensing regulators in vibrios.
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Affiliation(s)
- Ryan R Chaparian
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Stephen G Olney
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Christine M Hustmyer
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA
| | | | - Julia C van Kessel
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA
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Rajamanikandan S, Jeyakanthan J, Srinivasan P. Binding mode exploration of LuxR-thiazolidinedione analogues, e-pharmacophore-based virtual screening in the designing of LuxR inhibitors and its biological evaluation. J Biomol Struct Dyn 2016; 35:897-916. [PMID: 27141809 DOI: 10.1080/07391102.2016.1166455] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Master quorum sensing (QS) regulator LuxR of Vibrio harveyi is a unique member of the TetR protein superfamily. Recent studies have demonstrated the contribution of thiazolidinedione analogues in blocking QS by decreasing the DNA-binding ability of LuxR. However, the precise mechanism of thiazolidinedione analogues binding to LuxR is still unclear. In the present study, molecular docking combined with molecular dynamics (MD) simulations was performed to understand the mechanism of ligand binding to the protein. The binding pattern of thiazolidinedione analogues showed strong hydrogen bonding interactions with the amine group (NH) of polar amino acid residue Asn133 and carbonyl (C=O) interaction with negatively charged amino acid residue Gln137 in the binding site of LuxR. The stability of the protein-ligand complexes was confirmed by running 50 ns of MD simulations. Further, the four-featured pharmacophore hypothesis (AHHD) consists of one acceptor (A), two hydrophobic regions (HH) and one donor (D) group was used to screen compounds from ChemBridge database. The identified hit molecules were shown to have excellent pharmacokinetic properties under the acceptable range. Based on the computational studies, ChemBridge_5343641 was selected for in vitro assays. The 1-(4-chlorophenoxy)-3-[(4,6-dimethyl-2-pyrimidinyl)thio]-2-propanol (ChemBridge_5343641) showed significant reduction in bioluminescence in a dose-dependent manner. In addition, ChemBridge_5343641 inhibits biofilm formation and motility in V. harveyi. The result from the study suggests that ChemBridge_5343641 could serve as an anti-QS molecule.
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Affiliation(s)
| | - Jeyaraman Jeyakanthan
- a Department of Bioinformatics , Alagappa University , Karaikudi , TamilNadu , India
| | - Pappu Srinivasan
- a Department of Bioinformatics , Alagappa University , Karaikudi , TamilNadu , India.,b Department of Animal Health and Management , Alagappa University , Karaikudi , TamilNadu , India
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25
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Diversity of Clinical and Environmental Isolates of Vibrio cholerae in Natural Transformation and Contact-Dependent Bacterial Killing Indicative of Type VI Secretion System Activity. Appl Environ Microbiol 2016; 82:2833-2842. [PMID: 26944842 DOI: 10.1128/aem.00351-16] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 02/27/2016] [Indexed: 02/08/2023] Open
Abstract
The bacterial pathogen Vibrio cholerae can occupy both the human gut and aquatic reservoirs, where it may colonize chitinous surfaces that induce the expression of factors for three phenotypes: chitin utilization, DNA uptake by natural transformation, and contact-dependent bacterial killing via a type VI secretion system (T6SS). In this study, we surveyed a diverse set of 53 isolates from different geographic locales collected over the past century from human clinical and environmental specimens for each phenotype outlined above. The set included pandemic isolates of serogroup O1, as well as several serogroup O139 and non-O1/non-O139 strains. We found that while chitin utilization was common, only 22.6% of the isolates tested were proficient at chitin-induced natural transformation, suggesting that transformation is expendable. Constitutive contact-dependent killing of Escherichia coli prey, which is indicative of a functional T6SS, was rare among clinical isolates (only 4 of 29) but common among environmental isolates (22 of 24). These results bolster the pathoadaptive model in which tight regulation of T6SS-mediated bacterial killing is beneficial in a human host, whereas constitutive killing by environmental isolates may give a competitive advantage in natural settings. Future sequence analysis of this set of diverse isolates may identify previously unknown regulators and structural components for both natural transformation and T6SS.
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Teschler JK, Zamorano-Sánchez D, Utada AS, Warner CJA, Wong GCL, Linington RG, Yildiz FH. Living in the matrix: assembly and control of Vibrio cholerae biofilms. Nat Rev Microbiol 2015; 13:255-68. [PMID: 25895940 PMCID: PMC4437738 DOI: 10.1038/nrmicro3433] [Citation(s) in RCA: 253] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nearly all bacteria form biofilms as a strategy for survival and persistence. Biofilms are associated with biotic and abiotic surfaces and are composed of aggregates of cells that are encased by a self-produced or acquired extracellular matrix. Vibrio cholerae has been studied as a model organism for understanding biofilm formation in environmental pathogens, as it spends much of its life cycle outside of the human host in the aquatic environment. Given the important role of biofilm formation in the V. cholerae life cycle, the molecular mechanisms underlying this process and the signals that trigger biofilm assembly or dispersal have been areas of intense investigation over the past 20 years. In this Review, we discuss V. cholerae surface attachment, various matrix components and the regulatory networks controlling biofilm formation.
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Affiliation(s)
- Jennifer K. Teschler
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - David Zamorano-Sánchez
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Andrew S. Utada
- Bioengineering Department, Chemistry and Biochemistry Department, and NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Christopher J. A. Warner
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Gerard C. L. Wong
- Bioengineering Department, Chemistry and Biochemistry Department, and NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Roger G. Linington
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Fitnat H. Yildiz
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
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Hema M, Balasubramanian S, Princy SA. Meddling Vibrio cholerae Murmurs: A Neoteric Advancement in Cholera Research. Indian J Microbiol 2015; 55:121-30. [PMID: 25805898 DOI: 10.1007/s12088-015-0520-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 02/17/2015] [Indexed: 12/28/2022] Open
Abstract
Cholera, a known diarrheal disease is associated with various risk factors like hypovolemic shock, rice watery stools, and death in developing countries. The overuse of antibiotics to treat cholera imposed a selective pressure for the emergence and spread of multi-drug resistant Vibrio cholerae strains. The failure of conventional antimicrobial therapy urged the researchers to find an alternative therapy that could meddle the cholera murmurs (Quorum Sensing). It seems to effectively overcome the conventional cholera therapies in parallel to decrease the morbidity and mortality rate in the developing countries. The paramount objective of this review essentially focuses on the different Quorum Sensing (QS) regulatory switches governing virulence and pathogenicity of Vibrio cholerae. This review also provides an insight into the plausible QS targets that could be exploited to bring about a breakthrough to the prevailing cholera therapy.
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Affiliation(s)
- M Hema
- Quorum Sensing Laboratory, Centre for Research on Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA University, Thanjavur, 613 402 Tamil Nadu India
| | - Srikkanth Balasubramanian
- Quorum Sensing Laboratory, Centre for Research on Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA University, Thanjavur, 613 402 Tamil Nadu India
| | - S Adline Princy
- Quorum Sensing Laboratory, Centre for Research on Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA University, Thanjavur, 613 402 Tamil Nadu India
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Singh NS, Kachhap S, Singh R, Mishra RC, Singh B, Raychaudhuri S. The length of glycine-rich linker in DNA-binding domain is critical for optimal functioning of quorum-sensing master regulatory protein HapR. Mol Genet Genomics 2014; 289:1171-82. [PMID: 24997084 DOI: 10.1007/s00438-014-0878-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 06/06/2014] [Indexed: 01/03/2023]
Abstract
HapR is a quorum-sensing master regulatory protein in Vibrio cholerae. Though many facts are known regarding its structural and functional aspects, much still can be learnt from natural variants of this wild-type protein. While unraveling the underlying cause of functional inertness of a natural variant (HapRV2), the significance of a conserved glycine residue at position 39 in a glycine-rich linker in DNA-binding domain comes into light. This work aims at investigating how the length of glycine-rich linker (R(33)GIGRGG(39)) bridging helices α1 and α2 modulates the functionality of HapR. In pursuit of our interest, glycine residues were inserted after terminal glycine (G39) of the linker in a sequential manner. To evaluate functionality, all the glycine linker variants were subjected to a battery of performance tests under various conditions. Combined in vitro and in vivo results clearly demonstrated a gradual functional impairment of HapR linker variants coupled with increasing length of glycine-rich linker and finally, linker variant harboring four glycine residues resulted in a functionally compromised protein with significant loss of communication with cognate DNAs. Molecular dynamics studies of modeled HapR linker variants in complex with cognate promoter region show that residues namely Ser50, Thr53 and Asn56 are involved in varying degree of interactions with different nucleotides of HapR-DNA complex. The diminished functionality between variants and DNA appears to result from reduced or no interactions between Phe55 and nucleotides of cognate DNA as observed during simulations.
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Affiliation(s)
- Naorem Santa Singh
- Molecular Biology and Microbial Physiology Division, Institute of Microbial Technology (Council of Scientific and Industrial Research), Sector 39A, Chandigarh, 160036, India
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Abstract
The most common prokaryotic signal transduction mechanisms are the one-component systems in which a single polypeptide contains both a sensory domain and a DNA-binding domain. Among the >20 classes of one-component systems, the TetR family of regulators (TFRs) are widely associated with antibiotic resistance and the regulation of genes encoding small-molecule exporters. However, TFRs play a much broader role, controlling genes involved in metabolism, antibiotic production, quorum sensing, and many other aspects of prokaryotic physiology. There are several well-established model systems for understanding these important proteins, and structural studies have begun to unveil the mechanisms by which they bind DNA and recognize small-molecule ligands. The sequences for more than 200,000 TFRs are available in the public databases, and genomics studies are identifying their target genes. Three-dimensional structures have been solved for close to 200 TFRs. Comparison of these structures reveals a common overall architecture of nine conserved α helices. The most important open question concerning TFR biology is the nature and diversity of their ligands and how these relate to the biochemical processes under their control.
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Mechanisms underlying the additive and redundant Qrr phenotypes in Vibrio harveyi and Vibrio cholerae. J Theor Biol 2014; 340:38-49. [DOI: 10.1016/j.jtbi.2013.08.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 07/26/2013] [Accepted: 08/29/2013] [Indexed: 11/18/2022]
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The LuxR-type regulator VpsT negatively controls the transcription of rpoS, encoding the general stress response regulator, in Vibrio cholerae biofilms. J Bacteriol 2013; 196:1020-30. [PMID: 24363348 DOI: 10.1128/jb.00993-13] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cholera is a waterborne diarrheal disease caused by Vibrio cholerae strains of serogroups O1 and O139. Expression of the general stress response regulator RpoS and formation of biofilm communities enhance the capacity of V. cholerae to persist in aquatic environments. The transition of V. cholerae between free-swimming (planktonic) and biofilm life-styles is regulated by the second messenger cyclic di-GMP (c-di-GMP). We previously reported that increasing the c-di-GMP pool by overexpression of a diguanylate cyclase diminished RpoS expression. Here we show that c-di-GMP repression of RpoS expression is eliminated by deletion of the genes vpsR and vpsT, encoding positive regulators of biofilm development. To determine the mechanism of this regulation, we constructed a strain expressing a vpsT-FLAG allele from native transcription and translation signals. Increasing the c-di-GMP pool induced vpsT-FLAG expression. The interaction between VpsT-FLAG and the rpoS promoter was demonstrated by chromatin immunoprecipitation. Furthermore, purified VpsT interacted with the rpoS promoter in a c-di-GMP-dependent manner. Primer extension analysis identified two rpoS transcription initiation sites located 43 bp (P1) and 63 bp (P2) upstream of the rpoS start codon. DNase I footprinting showed that the VpsT binding site at the rpoS promoter overlaps the primary P1 transcriptional start site. Deletion of vpsT significantly enhanced rpoS expression in V. cholerae biofilms that do not make HapR. This result suggests that VpsT and c-di-GMP contribute to the transcriptional silencing of rpoS in biofilms prior to cells entering the quorum-sensing mode.
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Singh R, Rathore YS, Singh NS, Peddada N, Ashish, Raychaudhuri S. Substitution of glutamate residue by lysine in the dimerization domain affects DNA binding ability of HapR by inducing structural deformity in the DNA binding domain. PLoS One 2013; 8:e76033. [PMID: 24155884 PMCID: PMC3796514 DOI: 10.1371/journal.pone.0076033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 08/22/2013] [Indexed: 01/22/2023] Open
Abstract
HapR has been given the status of a high cell density master regulatory protein in Vibrio cholerae. Though many facts are known regarding its structural and functional aspects, much still can be learnt from natural variants of the wild type protein. This work aims at investigating the nature of functional inertness of a HapR natural variant harboring a substitution of a conserved glutamate residue at position 117 which participates in forming a salt bridge by lysine (HapRV2G-E(117)K). Experimental evidence presented here reveals the inability of this variant to interact with various cognate promoters by in vitro gel shift assay. Furthermore, the elution profiles of HapRV2G-E(117)K protein along with the wild type functional HapRV2G in size-exclusion chromatography as well as circular dichroism spectra did not reflect any significant differences in its structure, thereby indicating the intactness of dimer in the variant protein. To gain further insight into the global shape of the proteins, small angle X-ray scattering analysis (SAXS) was performed. Intriguingly, increased radius of gyration of HapRV2G-E(117)K of 27.5 Å in comparison to the wild type protein from SAXS data analyses implied a significant alteration in the global shape of the dimeric HapRV2G-E(117)K protein. Structure reconstruction brought forth that the DNA binding domains were substantially "parted away" in this variant. Taken together, our data illustrates that substitution of the conserved glutamate residue by lysine in the dimerization domain induces separation of the two DNA binding domains from their native-like positioning without altering the dimeric status of HapR variant.
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Affiliation(s)
- Richa Singh
- CSIR-Institute of Microbial Technology, Molecular Biology Division, Chandigarh, India
| | | | - Naorem Santa Singh
- CSIR-Institute of Microbial Technology, Molecular Biology Division, Chandigarh, India
| | - Nagesh Peddada
- CSIR-Institute of Microbial Technology, Molecular Biology Division, Chandigarh, India
| | - Ashish
- CSIR-Institute of Microbial Technology, Molecular Biology Division, Chandigarh, India
| | - Saumya Raychaudhuri
- CSIR-Institute of Microbial Technology, Molecular Biology Division, Chandigarh, India
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Kurnasov OV, Luk HJD, Roberts MF, Stec B. Structure of the inositol-1-phosphate cytidylyltransferase from Thermotoga maritima. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1808-17. [DOI: 10.1107/s0907444913015278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 06/02/2013] [Indexed: 11/10/2022]
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Analysis of activator and repressor functions reveals the requirements for transcriptional control by LuxR, the master regulator of quorum sensing in Vibrio harveyi. mBio 2013; 4:mBio.00378-13. [PMID: 23839217 PMCID: PMC3705450 DOI: 10.1128/mbio.00378-13] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
LuxR-type transcription factors are the master regulators of quorum sensing in vibrios. LuxR proteins are unique members of the TetR superfamily of transcription factors because they activate and repress large regulons of genes. Here, we used chromatin immunoprecipitation and nucleotide sequencing (ChIP-seq) to identify LuxR binding sites in the Vibrio harveyi genome. Bioinformatics analyses showed that the LuxR consensus binding site at repressed promoters is a symmetric palindrome, whereas at activated promoters it is asymmetric and contains only half of the palindrome. Using a genetic screen, we isolated LuxR mutants that separated activation and repression functions at representative promoters. These LuxR mutants exhibit sequence-specific DNA binding defects that restrict activation or repression activity to subsets of target promoters. Altering the LuxR DNA binding site sequence to one more closely resembling the ideal LuxR consensus motif can restore in vivo function to a LuxR mutant. This study provides a mechanistic understanding of how a single protein can recognize a variety of binding sites to differentially regulate gene expression. Bacteria use the cell-cell communication process called quorum sensing to regulate collective behaviors. In vibrios, LuxR-type transcription factors control the quorum-sensing gene expression cascade. LuxR-type proteins are structural homologs of TetR-type transcription factors. LuxR proteins were assumed to function analogously to TetR proteins, which typically bind to a single conserved binding site to repress transcription of one or two genes. We find here that unlike TetR proteins, LuxR acts a global regulator, directly binding upstream of and controlling more than 100 genes. Again unlike TetR, LuxR functions as both an activator and a repressor, and these two activities can be separated by mutagenesis. Finally, the consensus binding motifs driving LuxR-activated and -repressed genes are distinct. This work shows that LuxR, although structurally similar to TetR, has evolved unique features enabling it to differentially control a large regulon of genes in response to quorum-sensing cues.
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Yeo HK, Park YW, Kang J, Lee JY. Crystallization and preliminary X-ray diffraction analysis of the TetR-family transcriptional repressor YhgD from Bacillus halodurans. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:532-4. [PMID: 23695570 PMCID: PMC3660894 DOI: 10.1107/s174430911300763x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 03/19/2013] [Indexed: 11/10/2022]
Abstract
YhgD is a member of the TetR-family transcription factors, which regulate genes encoding proteins involved in multidrug resistance, virulence, osmotic stress and pathogenicity. YhgD from the alkaliphilic bacterium Bacillus halodurans was cloned and overexpressed in Escherichia coli. YhgD (Bh2145) from B. halodurans is composed of 193 amino-acid residues with a molecular mass of 21 853 Da. YhgD was crystallized at 296 K using ethylene glycol as a precipitant by the sitting-drop vapour-diffusion method. The crystal diffracted to 1.9 Å resolution and belonged to the apparent triclinic space group P1, with unit-cell parameters a = 37.22, b = 47.85, c = 54.15 Å, α = 92.75, β = 107.9, γ = 90.27°. The asymmetric unit is likely to contain two molecules of monomeric YhgD, giving a crystal volume per mass (VM) of 2.05 Å(3) Da(-1) and a solvent content of 40.2%.
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Affiliation(s)
- Hyun Ku Yeo
- Department of Life Science, Dongguk University-Seoul, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Republic of Korea
| | - Young Woo Park
- Department of Life Science, Dongguk University-Seoul, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Republic of Korea
| | - Jina Kang
- Department of Life Science, Dongguk University-Seoul, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Republic of Korea
| | - Jae Young Lee
- Department of Life Science, Dongguk University-Seoul, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Republic of Korea
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Defoirdt T, Benneche T, Brackman G, Coenye T, Sorgeloos P, Scheie AA. A quorum sensing-disrupting brominated thiophenone with a promising therapeutic potential to treat luminescent vibriosis. PLoS One 2012; 7:e41788. [PMID: 22848604 PMCID: PMC3404956 DOI: 10.1371/journal.pone.0041788] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Accepted: 06/25/2012] [Indexed: 02/02/2023] Open
Abstract
Vibrio harveyi is amongst the most important bacterial pathogens in aquaculture. Novel methods to control this pathogen are needed since many strains have acquired resistance to antibiotics. We previously showed that quorum sensing-disrupting furanones are able to protect brine shrimp larvae against vibriosis. However, a major problem of these compounds is that they are toxic toward higher organisms and therefore, they are not safe to be used in aquaculture. The synthesis of brominated thiophenones, sulphur analogues of the quorum sensing-disrupting furanones, has recently been reported. In the present study, we report that these compounds block quorum sensing in V. harveyi at concentrations in the low micromolar range. Bioluminescence experiments with V. harveyi quorum sensing mutants and a fluorescence anisotropy assay indicated that the compounds disrupt quorum sensing in this bacterium by decreasing the ability of the quorum sensing master regulator LuxR to bind to its target promoter DNA. In vivo challenge tests with gnotobiotic brine shrimp larvae showed that thiophenone compound TF310, (Z)-4-((5-(bromomethylene)-2-oxo-2,5-dihydrothiophen-3-yl)methoxy)-4-oxobutanoic acid, completely protected the larvae from V. harveyi BB120 when dosed to the culture water at 2.5 µM or more, whereas severe toxicity was only observed at 250 µM. This makes TF310 showing the highest therapeutic index of all quorum sensing-disrupting compounds tested thus far in our brine shrimp model system.
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Affiliation(s)
- Tom Defoirdt
- Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Ghent, Belgium.
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Fazil MHUT, Singh DV. Vibrio cholerae infection, novel drug targets and phage therapy. Future Microbiol 2011; 6:1199-208. [DOI: 10.2217/fmb.11.93] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Vibrio cholerae is the causative agent of the diarrheal disease cholera. Although antibiotic therapy shortens the duration of diarrhea, excessive use has contributed to the emergence of antibiotic resistance in V. cholerae. Mobile genetic elements have been shown to be largely responsible for the shift of drug resistance genes in bacteria, including some V. cholerae strains. Quorum sensing communication systems are used for interaction among bacteria and for sensing environmental signals. Sequence analysis of the ctxB gene of toxigenic V. cholerae strains demonstrated its presence in multiple cholera toxin genotypes. Moreover, bacteriophage that lyse the bacterium have been reported to modulate epidemics by decreasing the required infectious dose of the bacterium. In this article, we will briefly discuss the disease, its clinical manifestation, antimicrobial resistance and the novel approaches to locate drug targets to treat cholera.
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Interplay among cyclic diguanylate, HapR, and the general stress response regulator (RpoS) in the regulation of Vibrio cholerae hemagglutinin/protease. J Bacteriol 2011; 193:6529-38. [PMID: 21965573 DOI: 10.1128/jb.05166-11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae secretes the Zn-dependent metalloprotease hemagglutinin (HA)/protease (mucinase), which is encoded by hapA and displays a broad range of potential pathogenic activities. Expression of HA/protease has a stringent requirement for the quorum-sensing regulator HapR and the general stress response regulator RpoS. Here we report that the second messenger cyclic diguanylic acid (c-di-GMP) regulates the production of HA/protease in a negative manner. Overexpression of a diguanylate cyclase to increase the cellular c-di-GMP pool resulted in diminished expression of HA/protease and its positive regulator, HapR. The effect of c-di-GMP on HapR was independent of LuxO but was abolished by deletion of the c-di-GMP binding protein VpsT, the LuxR-type regulator VqmA, or a single-base mutation in the hapR promoter that prevents autorepression. Though expression of HapR had a positive effect on RpoS biosynthesis, direct manipulation of the c-di-GMP pool at a high cell density did not significantly impact RpoS expression in the wild-type genetic background. In contrast, increasing the c-di-GMP pool severely inhibited RpoS expression in a ΔhapR mutant that is locked in a regulatory state mimicking low cell density. Based on the above findings, we propose a model for the interplay between HapR, RpoS, and c-di-GMP in the regulation of HA/protease expression.
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Tsou AM, Liu Z, Cai T, Zhu J. The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR. MICROBIOLOGY-SGM 2011; 157:1620-1628. [PMID: 21393367 DOI: 10.1099/mic.0.046235-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The human pathogen Vibrio cholerae uses quorum sensing to regulate the expression of a number of phenotypes, including virulence factor production, in response to changes in cell density. It produces small molecules called autoinducers that increase in concentration as cell density increases, and these autoinducers bind to membrane sensors once they reach a certain threshold. This binding leads to signalling through a downstream phosphorelay pathway to alter the expression of the transcriptional regulator HapR. Previously, it was shown that the VarS/VarA two-component system acts on a component of the phosphorelay pathway upstream of HapR to regulate HapR expression levels. Here, we show that in addition to this mechanism of regulation, VarS and VarA also indirectly modulate HapR protein activity. This modulation is mediated by the small RNA CsrB but is independent of the known quorum-sensing system that links the autoinducers to HapR. Thus, the VarS/VarA two-component system intersects with the quorum-sensing network at two levels. In both cases, the effect of VarS and VarA on quorum sensing is dependent on the Csr small RNAs, which regulate carbon metabolism, suggesting that V. cholerae may integrate nutrient status and cell density sensory inputs to tailor its gene expression profile more precisely to surrounding conditions.
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Affiliation(s)
- Amy M Tsou
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Zhi Liu
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Tao Cai
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Jun Zhu
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Dongre M, Singh NS, Dureja C, Peddada N, Solanki AK, Ashish, Raychaudhuri S. Evidence on how a conserved glycine in the hinge region of HapR regulates its DNA binding ability: lessons from a natural variant. J Biol Chem 2011; 286:15043-9. [PMID: 21383015 DOI: 10.1074/jbc.m110.209346] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HapR has been recognized as a quorum-sensing master regulator in Vibrio cholerae. Because it controls a plethora of disparate cellular events, the absence of a functional HapR affects the physiology of V. cholerae to a great extent. In the current study, we pursued an understanding of an observation of a natural protease-deficient non-O1, non-O139 variant V. cholerae strain V2. Intriguingly, a nonfunctional HapR (henceforth designated as HapR(V2)) harboring a substitution of glycine to aspartate at position 39 of the N-terminal hinge region has been identified. An in vitro gel shift assay clearly suggested the inability of HapR(V2) to interact with various cognate promoters. Reinstatement of glycine at position 39 restores DNA binding ability of HapR(V2) (HapR(V2G)), thereby rescuing the protease-negative phenotype of this strain. The elution profile of HapR(V2) and HapR(V2G) proteins in size-exclusion chromatography and their circular dichroism spectra did not reflect any significant differences to explain the functional discrepancies between the two proteins. To gain insight into the structure-function relationship of these two proteins, we acquired small/wide angle x-ray scattering data from samples of the native and G39D mutant. Although Guinier analysis and indirect Fourier transformation of scattering indicated only a slight difference in the shape parameters, structure reconstruction using dummy amino acids concluded that although HapR adopts a "Y" shape similar to its crystal structure, the G39D mutation in hinge drastically altered the DNA binding domains by bringing them in close proximity. This altered spatial orientation of the helix-turn-helix domains in this natural variant provides the first structural evidence on the functional role of the hinge region in quorum sensing-related DNA-binding regulatory proteins of Vibrio spp.
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Affiliation(s)
- Mitesh Dongre
- Institute of Microbial Technology, Chandigarh, Council of Scientific and Industrial Research, Sector 39A, Chandigarh 160036, India
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Structure-activity relationship of cinnamaldehyde analogs as inhibitors of AI-2 based quorum sensing and their effect on virulence of Vibrio spp. PLoS One 2011; 6:e16084. [PMID: 21249192 PMCID: PMC3020944 DOI: 10.1371/journal.pone.0016084] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 12/09/2010] [Indexed: 11/19/2022] Open
Abstract
Background Many bacteria, including Vibrio spp., regulate virulence gene expression in a cell-density dependent way through a communication process termed quorum sensing (QS). Hence, interfering with QS could be a valuable novel antipathogenic strategy. Cinnamaldehyde has previously been shown to inhibit QS-regulated virulence by decreasing the DNA-binding ability of the QS response regulator LuxR. However, little is known about the structure-activity relationship of cinnamaldehyde analogs. Methodology/Principal Findings By evaluating the QS inhibitory activity of a series of cinnamaldehyde analogs, structural elements critical for autoinducer-2 QS inhibition were identified. These include an α,β unsaturated acyl group capable of reacting as Michael acceptor connected to a hydrophobic moiety and a partially negative charge. The most active cinnamaldehyde analogs were found to affect the starvation response, biofilm formation, pigment production and protease production in Vibrio spp in vitro, while exhibiting low cytotoxicity. In addition, these compounds significantly increased the survival of the nematode Caenorhabditis elegans infected with Vibrio anguillarum, Vibrio harveyi and Vibrio vulnificus. Conclusions/Significance Several new and more active cinnamaldehyde analogs were discovered and they were shown to affect Vibrio spp. virulence factor production in vitro and in vivo. Although ligands for LuxR have not been identified so far, the nature of different cinnamaldehyde analogs and their effect on the DNA binding ability of LuxR suggest that these compounds act as LuxR-ligands.
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Goryachev AB. Design principles of the bacterial quorum sensing gene networks. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2010; 1:45-60. [PMID: 20835981 DOI: 10.1002/wsbm.27] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Bacterial quorum sensing (QS) has attracted much interest as the manifestation of collective behavior in prokaryotic organisms once considered strictly solitary. Significant amount of genetic, biochemical, and structural data which, has been accumulated in studies on QS in many species allows us to map properties of specific molecules and their interactions on the observed population-wide bacterial behavior. The present review attempts to give a systems biology perspective on the structure of genetic regulatory networks that control QS and considers functional implications of a variety of design principles that recur in the organization of these networks across species.
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Affiliation(s)
- Andrew B Goryachev
- Centre for Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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Quorum sensing and a global regulator TsrA control expression of type VI secretion and virulence in Vibrio cholerae. Proc Natl Acad Sci U S A 2010; 107:21128-33. [PMID: 21084635 DOI: 10.1073/pnas.1014998107] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vibrio cholerae is a human pathogen that causes the life-threatening diarrheal disease cholera. A type VI secretion system (T6SS) was recently shown to be required for full virulence in the O37 serogroup strain V52, which causes only sporadic human disease, but T6SS is not expressed in seventh pandemic O1 El Tor strains under standard laboratory conditions. In this study, we show that in the O1 El Tor strain C6706, T6SS is repressed by both quorum sensing and the uncharacterized protein VC0070 (TsrA). Disruption of TsrA and the quorum sensing regulator LuxO induces expression and secretion of the T6SS substrate Hcp, and this is dependent on the downstream regulator HapR, which directly binds to the promoter region of the T6SS genes hcp1 and hcp2 to induce expression. The activated T6SS in C6706 is functional and can translocate the effector protein VgrG-1 into macrophage cells, and T6SS activation leads to fecal diarrhea and intestinal inflammation in infant rabbits. Using an infant mouse infection model, we show that deletion of tsrA results in a 9.3-fold increase in intestinal colonization compared with wild type. TsrA functions as a global regulator to activate expression of hemagglutinin protease and repress cholera toxin and toxin coregulated pilus. Our findings provide significant insight into the molecular mechanism of T6SS and ToxT regulon gene regulation by quorum sensing and TsrA.
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Itou H, Watanabe N, Yao M, Shirakihara Y, Tanaka I. Crystal structures of the multidrug binding repressor Corynebacteriumglutamicum CgmR in complex with inducers and with an operator. J Mol Biol 2010; 403:174-84. [PMID: 20691702 DOI: 10.1016/j.jmb.2010.07.042] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 07/20/2010] [Accepted: 07/22/2010] [Indexed: 10/19/2022]
Abstract
CgmR (CGL2612) from Corynebacterium glutamicum is a multidrug-resistance-related transcription factor belonging to the TetR family, which is a protein family of widespread bacterial transcription factors typically involved in environmental response. Here, we report the crystal structures of CgmR homodimeric repressor in complex with two distinct inducers (1.95 and 1.4 Å resolution) and with an operator (2.5 Å resolution). The CgmR-operator complex showed that two CgmR dimers bound to the operator, and each half-site of the palindromic operator was asymmetrically recognized by two DNA-binding domains from different dimers on the opposite sides of the DNA. The inducer complexes demonstrated that both bound inducers act as a wedge to alter the operator-binding conformation of the repressor by steric inhibition. As steric hindrance is used, various drugs should act as inducers if they have sufficient volume for the conformation change and if their bindings sufficiently reduce free energy. The comparative structural study of CgmR free protein, in complex with operator, and with inducers, implies the other mechanism that might contribute to multidrug response of the repressor.
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Affiliation(s)
- Hiroshi Itou
- Structural Biology Center, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan.
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Kim Y, Kim BS, Park YJ, Choi WC, Hwang J, Kang BS, Oh TK, Choi SH, Kim MH. Crystal structure of SmcR, a quorum-sensing master regulator of Vibrio vulnificus, provides insight into its regulation of transcription. J Biol Chem 2010; 285:14020-30. [PMID: 20178981 PMCID: PMC2859563 DOI: 10.1074/jbc.m109.100248] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Quorum sensing has been implicated as an important global regulatory system controlling the expression of numerous virulence factors in bacterial pathogens. SmcR, a homologue of Vibrio harveyi LuxR, has been proposed as a quorum-sensing master regulator of Vibrio vulnificus, an opportunistic human pathogen. Previous studies demonstrated that SmcR is essential for the survival and pathogenesis of V. vulnificus, indicating that inhibiting SmcR is an attractive approach to combat infections by the bacteria. Here, we determined the crystal structure of SmcR at 2.1 Å resolution. The protein structure reveals a typical TetR superfamily fold consisting of an N-terminal DNA binding domain and a C-terminal dimerization domain. In vivo and in vitro functional analysis of the dimerization domain suggested that dimerization of SmcR is vital for its biological regulatory function. The N-terminal DNA recognition and binding residues were assigned based on the protein structure and the results of in vivo and in vitro mutagenesis experiments. Furthermore, protein-DNA interaction experiments suggested that SmcR may have a sophisticated mechanism that enables the protein to recognize each of its many target operators with different affinities.
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Affiliation(s)
- Yoonjeong Kim
- Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806
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TetR-type transcriptional regulator VtpR functions as a global regulator in Vibrio tubiashii. Appl Environ Microbiol 2009; 75:7602-9. [PMID: 19837838 DOI: 10.1128/aem.01016-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio tubiashii, a causative agent of severe shellfish larval disease, produces multiple extracellular proteins, including a metalloprotease (VtpA), as potential virulence factors. We previously reported that VtpA is toxic for Pacific oyster (Crassostrea gigas) larvae. In this study, we show that extracellular protease production by V. tubiashii was much reduced by elevated salt concentrations, as well as by elevated temperatures. In addition, V. tubiashii produced dramatically less protease in minimal salts medium supplemented with glucose or sucrose as the sole carbon source than with succinate. We identified a protein that belongs to the TetR family of transcriptional regulators, VtpR, which showed high homology with V. cholerae HapR. We conclude that VtpR activates VtpA production based on the following: (i) a VtpR-deficient V. tubiashii mutant did not produce extracellular proteases, (ii) the mutant showed reduced expression of a vtpA-lacZ fusion, and (iii) VtpR activated vtpA-lacZ in a V. cholerae heterologous background. Moreover, we show that VtpR activated the expression of an additional metalloprotease gene (vtpB). The deduced VtpB sequence showed high homology with a metalloprotease, VhpA, from V. harveyi. Furthermore, the vtpR mutant strain produced reduced levels of extracellular hemolysin, which is attributed to the lower expression of the V. tubiashii hemolysin genes (vthAB). The VtpR-deficient mutant also had negative effects on bacterial motility and did not demonstrate toxicity to oyster larvae. Together, these findings establish that the V. tubiashii VtpR protein functions as a global regulator controlling an array of potential virulence factors.
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Structural plasticity and distinct drug-binding modes of LfrR, a mycobacterial efflux pump regulator. J Bacteriol 2009; 191:7531-7. [PMID: 19820093 DOI: 10.1128/jb.00631-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The TetR-like transcriptional repressor LfrR controls the expression of the gene encoding the Mycobacterium smegmatis efflux pump LfrA, which actively extrudes fluoroquinolones, cationic dyes, and anthracyclines from the cell and promotes intrinsic antibiotic resistance. The crystal structure of the apoprotein form of the repressor reveals a structurally asymmetric homodimer exhibiting local unfolding and a blocked drug-binding site, emphasizing the significant conformational plasticity of the protein necessary for DNA and multidrug recognition. Crystallographic and calorimetric studies of LfrR-drug complexes further confirm the intrinsic flexibility of the homodimer, which provides a dynamic mechanism to broaden multidrug binding specificity and may be a general property of transcriptional repressors regulating microbial efflux pump expression.
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Routh MD, Su CC, Zhang Q, Yu EW. Structures of AcrR and CmeR: insight into the mechanisms of transcriptional repression and multi-drug recognition in the TetR family of regulators. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1794:844-51. [PMID: 19130905 PMCID: PMC2729549 DOI: 10.1016/j.bbapap.2008.12.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 11/26/2008] [Accepted: 12/01/2008] [Indexed: 11/27/2022]
Abstract
The transcriptional regulators of the TetR family act as chemical sensors to monitor the cellular environment in many bacterial species. To perform this function, members of the TetR family harbor a diverse ligand-binding domain capable of recognizing the same series of compounds as the transporters they regulate. Many of the regulators can be induced by a wide array of structurally unrelated compounds. Binding of these structurally unrelated ligands to the regulator results in a conformational change that is transmitted to the DNA-binding region, causing the repressor to lose its DNA-binding capacity and allowing for the initiation of transcription. The multi-drug binding proteins AcrR of Escherichia coli and CmeR from Campylobacter jejuni are members of the TetR family of transcriptional repressors that regulate the expression of the multidrug resistant efflux pumps AcrAB and CmeABC, respectively. To gain insights into the mechanisms of transcriptional regulation and how multiple ligands induce the same physiological response, we determined the crystal structures of the AcrR and CmeR regulatory proteins. In this review, we will summarize the new findings with AcrR and CmeR, and discuss the novel features of these two proteins in comparison with other regulators in the TetR family.
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Affiliation(s)
- Mathew D. Routh
- Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, IA 50011, USA
| | - Chih-Chia Su
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Qijing Zhang
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Edward W. Yu
- Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, IA 50011, USA
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
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Nanotransportation system for cholera toxin in Vibrio cholerae 01. Med Mol Morphol 2009; 42:40-6. [PMID: 19294491 DOI: 10.1007/s00795-008-0431-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 11/27/2008] [Indexed: 10/21/2022]
Abstract
Vibrio cholerae (V. cholerae) cholera toxin (CT), which causes a severe watery diarrheal illness, is secreted via the type II secretion machinery; it remains unclear, however, how this toxin is transported toward the machinery. In this study, we determined that the pH-dependent intrabacterial transport system correlates with the priming of CT secretion by V. cholerae. The secretion and production of V. cholerae treated at different pHs were examined by enzyme immunoassay. The localization of the CT was analyzed by immunoelectron microscopy. The CT secretion level rapidly increases in the alkaline-pH-treated V. cholerae but does so more slowly in neutral- and acidic-pH-treated V. cholerae. The CT was found to be densely localized near the membrane in the alkaline-pH-treated bacterial cytoplasm, suggesting that the CT shifts from the center to the peripheral portion of the cytoplasm following an extracellular rise in pH. The shift was observed in V. cholerae treated at alkaline pH for more than 10 min. The pH treatment did not enhance CT production at the same stage at which secretion and intrabacterial transport of the CT were enhanced. We propose that V. cholerae possesses a pH-dependent intrabacterial nanotransportation system that probably accelerates priming for CT secretion.
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