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Silva WM, Folador EL, Soares SC, Souza GHMF, Santos AV, Sousa CS, Figueiredo H, Miyoshi A, Le Loir Y, Silva A, Azevedo V. Label-free quantitative proteomics of Corynebacterium pseudotuberculosis isolates reveals differences between Biovars ovis and equi strains. BMC Genomics 2017; 18:451. [PMID: 28595597 PMCID: PMC5463331 DOI: 10.1186/s12864-017-3835-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 05/31/2017] [Indexed: 11/24/2022] Open
Affiliation(s)
- Wanderson M Silva
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil.,INRA, UMR1253 STLO, 35042, Rennes, France.,Agrocampus Ouest, UMR1253 STLO, 35042, Rennes, France
| | - Edson L Folador
- Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Paraíba, Brasil
| | - Siomar C Soares
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil.,Departmento de Microbiologia, Imunologia e Parasitologia, Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brasil
| | - Gustavo H M F Souza
- Waters Corporation, Waters Technologies Brazil, MS Applications Laboratory, Alphaville, São Paulo, Brasil
| | - Agenor V Santos
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brasil
| | - Cassiana S Sousa
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil
| | - Henrique Figueiredo
- Escola de Veterinária, Aquavet, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil
| | - Anderson Miyoshi
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil
| | - Yves Le Loir
- INRA, UMR1253 STLO, 35042, Rennes, France.,Agrocampus Ouest, UMR1253 STLO, 35042, Rennes, France
| | - Artur Silva
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brasil
| | - Vasco Azevedo
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil.
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Silva WM, Dorella FA, Soares SC, Souza GHMF, Castro TLP, Seyffert N, Figueiredo H, Miyoshi A, Le Loir Y, Silva A, Azevedo V. A shift in the virulence potential of Corynebacterium pseudotuberculosis biovar ovis after passage in a murine host demonstrated through comparative proteomics. BMC Microbiol 2017; 17:55. [PMID: 28327085 PMCID: PMC5361795 DOI: 10.1186/s12866-017-0925-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 01/04/2017] [Indexed: 01/19/2023] Open
Abstract
Background Corynebacterium pseudotuberculosis biovar ovis, a facultative intracellular pathogen, is the etiologic agent of caseous lymphadenitis in small ruminants. During the infection process, C. pseudotuberculosis changes its gene expression to resist different types of stresses and to evade the immune system of the host. However, factors contributing to the infectious process of this pathogen are still poorly documented. To better understand the C. pseudotuberculosis infection process and to identify potential factors which could be involved in its virulence, experimental infection was carried out in a murine model using the strain 1002_ovis and followed by a comparative proteomic analysis of the strain before and after passage. Results The experimental infection assays revealed that strain 1002_ovis exhibits low virulence potential. However, the strain recovered from the spleen of infected mice and used in a new infection challenge showed a dramatic change in its virulence potential. Label-free proteomic analysis of the culture supernatants of strain 1002_ovis before and after passage in mice revealed that 118 proteins were differentially expressed. The proteome exclusive to the recovered strain contained important virulence factors such as CP40 proteinase and phospholipase D exotoxin, the major virulence factor of C. pseudotuberculosis. Also, the proteome from recovered condition revealed different classes of proteins involved in detoxification processes, pathogenesis and export pathways, indicating the presence of distinct mechanisms that could contribute in the infectious process of this pathogen. Conclusions This study shows that C. pseudotuberculosis modifies its proteomic profile in the laboratory versus infection conditions and adapts to the host context during the infection process. The screening proteomic performed us enable identify known virulence factors, as well as potential proteins that could be related to virulence this pathogen. These results enhance our understanding of the factors that might influence in the virulence of C. pseudotuberculosis. Electronic supplementary material The online version of this article (doi:10.1186/s12866-017-0925-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wanderson M Silva
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.,INRA, UMR1253 STLO, 35042, Rennes, France.,Agrocampus Ouest, UMR1253 STLO, 35042, Rennes, France
| | - Fernanda A Dorella
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Siomar C Soares
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Gustavo H M F Souza
- Waters Corporation, Waters Technologies Brazil, MS Applications Laboratory, Alphaville, São Paulo, Brazil
| | - Thiago L P Castro
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Núbia Seyffert
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Henrique Figueiredo
- Aquacen, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Anderson Miyoshi
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Yves Le Loir
- INRA, UMR1253 STLO, 35042, Rennes, France.,Agrocampus Ouest, UMR1253 STLO, 35042, Rennes, France
| | - Artur Silva
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Guamá, Belém, Pará, Brazil
| | - Vasco Azevedo
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
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3
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Abstract
The development and application of a highly versatile suite of tools for mycobacterial genetics, coupled with widespread use of "omics" approaches to elucidate the structure, function, and regulation of mycobacterial proteins, has led to spectacular advances in our understanding of the metabolism and physiology of mycobacteria. In this article, we provide an update on nucleotide metabolism and DNA replication in mycobacteria, highlighting key findings from the past 10 to 15 years. In the first section, we focus on nucleotide metabolism, ranging from the biosynthesis, salvage, and interconversion of purine and pyrimidine ribonucleotides to the formation of deoxyribonucleotides. The second part of the article is devoted to DNA replication, with a focus on replication initiation and elongation, as well as DNA unwinding. We provide an overview of replication fidelity and mutation rates in mycobacteria and summarize evidence suggesting that DNA replication occurs during states of low metabolic activity, and conclude by suggesting directions for future research to address key outstanding questions. Although this article focuses primarily on observations from Mycobacterium tuberculosis, it is interspersed, where appropriate, with insights from, and comparisons with, other mycobacterial species as well as better characterized bacterial models such as Escherichia coli. Finally, a common theme underlying almost all studies of mycobacterial metabolism is the potential to identify and validate functions or pathways that can be exploited for tuberculosis drug discovery. In this context, we have specifically highlighted those processes in mycobacterial DNA replication that might satisfy this critical requirement.
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Liu YJ, Song X, Li Y, Xuan J, Cui Q, Wang J, Feng Y. Low stability of the reduced state of Mycobacterium tuberculosis NrdH redoxin. FEBS Lett 2016; 590:387-95. [PMID: 26786191 DOI: 10.1002/1873-3468.12068] [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: 10/27/2015] [Revised: 01/08/2016] [Accepted: 01/11/2016] [Indexed: 11/10/2022]
Abstract
NrdH redoxin is the only hydrogen donor for ribonucleotide reductase in Mycobacterium tuberculosis. Several crystal structures of NrdH redoxins in the oxidized state from different species have been reported, but no structure of the reduced state has yet been reported. Using NMR spectroscopy, we found surprisingly that the reduced NrdH redoxin from M. tuberculosis is largely unfolded at a pH lower than the pKa of its first active site cysteine, and the structural basis of the low stability was analyzed. In addition, a single mutant of the NrdH redoxin suitable to determine the structure in the reduced state was obtained.
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Affiliation(s)
- Ya-Jun Liu
- Shandong Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China
| | - Xiaxia Song
- Department of Biological Science and Engineering, School of Chemical and Biological Engineering, University of Science and Technology Beijing, China
| | - Yifei Li
- Shandong Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China
| | - Jinsong Xuan
- Department of Biological Science and Engineering, School of Chemical and Biological Engineering, University of Science and Technology Beijing, China
| | - Qiu Cui
- Shandong Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China
| | - Jinfeng Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yingang Feng
- Shandong Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China.,CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, China
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5
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NrdH Redoxin enhances resistance to multiple oxidative stresses by acting as a peroxidase cofactor in Corynebacterium glutamicum. Appl Environ Microbiol 2013; 80:1750-62. [PMID: 24375145 DOI: 10.1128/aem.03654-13] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
NrdH redoxins are small protein disulfide oxidoreductases behaving like thioredoxins but sharing a high amino acid sequence similarity to glutaredoxins. Although NrdH redoxins are supposed to be another candidate in the antioxidant system, their physiological roles in oxidative stress remain unclear. In this study, we confirmed that the Corynebacterium glutamicum NrdH redoxin catalytically reduces the disulfides in the class Ib ribonucleotide reductases (RNR), insulin and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), by exclusively receiving electrons from thioredoxin reductase. Overexpression of NrdH increased the resistance of C. glutamicum to multiple oxidative stresses by reducing ROS accumulation. Accordingly, elevated expression of the nrdH gene was observed when the C. glutamicum wild-type strain was exposed to oxidative stress conditions. It was discovered that the NrdH-mediated resistance to oxidative stresses was largely dependent on the presence of the thiol peroxidase Prx, as the increased resistance to oxidative stresses mediated by overexpression of NrdH was largely abrogated in the prx mutant. Furthermore, we showed that NrdH facilitated the hydroperoxide reduction activity of Prx by directly targeting and serving as its electron donor. Thus, we present evidence that the NrdH redoxin can protect against the damaging effects of reactive oxygen species (ROS) induced by various exogenous oxidative stresses by acting as a peroxidase cofactor.
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Pawlik A, Garnier G, Orgeur M, Tong P, Lohan A, Le Chevalier F, Sapriel G, Roux AL, Conlon K, Honoré N, Dillies MA, Ma L, Bouchier C, Coppée JY, Gaillard JL, Gordon SV, Loftus B, Brosch R, Herrmann JL. Identification and characterization of the genetic changes responsible for the characteristic smooth-to-rough morphotype alterations of clinically persistent Mycobacterium abscessus. Mol Microbiol 2013; 90:612-29. [PMID: 23998761 DOI: 10.1111/mmi.12387] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2013] [Indexed: 12/13/2022]
Abstract
Mycobacterium abscessus is an emerging pathogen that is increasingly recognized as a relevant cause of human lung infection in cystic fibrosis patients. This highly antibiotic-resistant mycobacterium is an exception within the rapidly growing mycobacteria, which are mainly saprophytic and non-pathogenic organisms. M. abscessus manifests as either a smooth (S) or a rough (R) colony morphotype, which is of clinical importance as R morphotypes are associated with more severe and persistent infections. To better understand the molecular mechanisms behind the S/R alterations, we analysed S and R variants of three isogenic M. abscessus S/R pairs using an unbiased approach involving genome and transcriptome analyses, transcriptional fusions and integrating constructs. This revealed different small insertions, deletions (indels) or single nucleotide polymorphisms within the non-ribosomal peptide synthase gene cluster mps1-mps2-gap or mmpl4b in the three R variants, consistent with the transcriptional differences identified within this genomic locus that is implicated in the synthesis and transport of Glyco-Peptido-Lipids (GPL). In contrast to previous reports, the identification of clearly defined genetic lesions responsible for the loss of GPL-production or transport makes a frequent switching back-and-forth between smooth and rough morphologies in M. abscessus highly unlikely, which is important for our understanding of persistent M. abscessus infections.
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Affiliation(s)
- Alexandre Pawlik
- Institut Pasteur, Unit for Integrated Mycobacterial Pathogenomics, Paris, France; EA 3647, University Versailles St Quentin in Yvelines, Garches, France; Microbiology Laboratory, Assistance Publique - Hôpitaux de Paris, Raymond Poincaré Hospital, Garches, France
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Van Laer K, Dziewulska AM, Fislage M, Wahni K, Hbeddou A, Collet JF, Versées W, Mateos LM, Tamu Dufe V, Messens J. NrdH-redoxin of Mycobacterium tuberculosis and Corynebacterium glutamicum dimerizes at high protein concentration and exclusively receives electrons from thioredoxin reductase. J Biol Chem 2013; 288:7942-7955. [PMID: 23362277 PMCID: PMC3597831 DOI: 10.1074/jbc.m112.392688] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2012] [Revised: 01/22/2013] [Indexed: 11/06/2022] Open
Abstract
NrdH-redoxins are small reductases with a high amino acid sequence similarity with glutaredoxins and mycoredoxins but with a thioredoxin-like activity. They function as the electron donor for class Ib ribonucleotide reductases, which convert ribonucleotides into deoxyribonucleotides. We solved the x-ray structure of oxidized NrdH-redoxin from Corynebacterium glutamicum (Cg) at 1.5 Å resolution. Based on this monomeric structure, we built a homology model of NrdH-redoxin from Mycobacterium tuberculosis (Mt). Both NrdH-redoxins have a typical thioredoxin fold with the active site CXXC motif located at the N terminus of the first α-helix. With size exclusion chromatography and small angle x-ray scattering, we show that Mt_NrdH-redoxin is a monomer in solution that has the tendency to form a non-swapped dimer at high protein concentration. Further, Cg_NrdH-redoxin and Mt_NrdH-redoxin catalytically reduce a disulfide with a specificity constant 1.9 × 10(6) and 5.6 × 10(6) M(-1) min(-1), respectively. They use a thiol-disulfide exchange mechanism with an N-terminal cysteine pKa lower than 6.5 for nucleophilic attack, whereas the pKa of the C-terminal cysteine is ~10. They exclusively receive electrons from thioredoxin reductase (TrxR) and not from mycothiol, the low molecular weight thiol of actinomycetes. This specificity is shown in the structural model of the complex between NrdH-redoxin and TrxR, where the two surface-exposed phenylalanines of TrxR perfectly fit into the conserved hydrophobic pocket of the NrdH-redoxin. Moreover, nrdh gene deletion and disruption experiments seem to indicate that NrdH-redoxin is essential in C. glutamicum.
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Affiliation(s)
- Koen Van Laer
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium
| | - Aleksandra M Dziewulska
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium
| | - Marcus Fislage
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Khadija Wahni
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium
| | - Abderahim Hbeddou
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium
| | - Jean-Francois Collet
- Brussels Center for Redox Biology, 1050 Brussels, Belgium; de Duve Institute, Université Catholique de Louvain, 1200 Brussels, Belgium; Welbio, 1200 Brussels, Belgium
| | - Wim Versées
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Luis M Mateos
- Department of Molecular Biology, Area of Microbiology, University of León, 24071 León, Spain
| | - Veronica Tamu Dufe
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium; Welbio, 1200 Brussels, Belgium
| | - Joris Messens
- Department of Structural Biology, Vlaams Instituut voor Biotechnologie, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Brussels Center for Redox Biology, 1050 Brussels, Belgium.
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8
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Barh D, Jain N, Tiwari S, Parida BP, D'Afonseca V, Li L, Ali A, Santos AR, Guimarães LC, de Castro Soares S, Miyoshi A, Bhattacharjee A, Misra AN, Silva A, Kumar A, Azevedo V. A novel comparative genomics analysis for common drug and vaccine targets in Corynebacterium pseudotuberculosis and other CMN group of human pathogens. Chem Biol Drug Des 2011; 78:73-84. [PMID: 21443692 DOI: 10.1111/j.1747-0285.2011.01118.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Caseous lymphadenitis is a chronic goat and sheep disease caused by Corynebacterium pseudotuberculosis (Cp) that accounts for a huge economic loss worldwide. Proper vaccination or medication is not available because of the lack of understanding of molecular biology of the pathogen. In a recent approach, four Cp (CpFrc41, Cp1002, CpC231, and CpI-19) genomes were sequenced to elucidate the molecular pathology of the bacteria. In this study, using these four genome sequences along with other eight genomes (total 12 genomes) and a novel subtractive genomics approach (first time ever applied to a veterinary pathogen), we identified potential conserved common drug and vaccine targets of these four Cp strains along with other Corybacterium, Mycobacterium and Nocardia (CMN) group of human pathogens (Corynebacterium diphtheriae and Mycobacterium tuberculosis) considering goat, sheep, bovine, horse, and human as the most affected hosts. The minimal genome of Cp1002 was found to consist of 724 genes, and 20 conserved common targets (to all Cp strains as well as CMN group of pathogens) from various metabolic pathways (13 from host-pathogen common and seven from pathogen's unique pathways) are potential targets irrespective of all hosts considered. ubiA from host-pathogen common pathway and an ABC-like transporter from unique pathways may serve dual (drug and vaccine) targets. Two Corynebacterium-specific (mscL and resB) and one broad-spectrum (rpmB) novel targets were also identified. Strain-specific targets are also discussed. Six important targets were subjected to virtual screening, and one compound was found to be potent enough to render two targets (cdc and nrdL). We are currently validating all identified targets and lead compounds.
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Affiliation(s)
- Debmalya Barh
- Centre for Genomics and Applied Gene Technology, Institute of Integrative Omics and Applied Biotechnology, Nonakuri, Purba Medinipur, West Bengal, India.
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Staphylococcus aureus NrdH redoxin is a reductant of the class Ib ribonucleotide reductase. J Bacteriol 2010; 192:4963-72. [PMID: 20675493 DOI: 10.1128/jb.00539-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Staphylococci contain a class Ib NrdEF ribonucleotide reductase (RNR) that is responsible, under aerobic conditions, for the synthesis of deoxyribonucleotide precursors for DNA synthesis and repair. The genes encoding that RNR are contained in an operon consisting of three genes, nrdIEF, whereas many other class Ib RNR operons contain a fourth gene, nrdH, that determines a thiol redoxin protein, NrdH. We identified a 77-amino-acid open reading frame in Staphylococcus aureus that resembles NrdH proteins. However, S. aureus NrdH differs significantly from the canonical NrdH both in its redox-active site, C-P-P-C instead of C-M/V-Q-C, and in the absence of the C-terminal [WF]SGFRP[DE] structural motif. We show that S. aureus NrdH is a thiol redox protein. It is not essential for aerobic or anaerobic growth and appears to have a marginal role in protection against oxidative stress. In vitro, S. aureus NrdH was found to be an efficient reductant of disulfide bonds in low-molecular-weight substrates and proteins using dithiothreitol as the source of reducing power and an effective reductant for the homologous class Ib RNR employing thioredoxin reductase and NADPH as the source of the reducing power. Its ability to reduce NrdEF is comparable to that of thioredoxin-thioredoxin reductase. Hence, S. aureus contains two alternative thiol redox proteins, NrdH and thioredoxin, with both proteins being able to function in vitro with thioredoxin reductase as the immediate hydrogen donors for the class Ib RNR. It remains to be clarified under which in vivo physiological conditions the two systems are used.
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