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Prasad D, Muniyappa K. The extended N-terminus of Mycobacterium smegmatis RecX potentiates its ability to antagonize RecA functions. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140468. [PMID: 32526474 DOI: 10.1016/j.bbapap.2020.140468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 05/21/2020] [Accepted: 06/05/2020] [Indexed: 01/13/2023]
Abstract
The members of the RecX family of proteins have a unique capacity to regulate the catalytic activities of RecA/Rad51 proteins in both prokaryotic and eukaryotic organisms. However, our understanding of the functional roles of RecX in pathogenic and non-pathogenic mycobacteria has been limited by insufficient knowledge of the molecular mechanisms of its activity and regulation. Moreover, the significance of a unique 14 amino acid N-terminal extension in Mycobacterium smegmatis RecX (MsRecX) to its function remains unknown. Here, we advance our understanding of the antagonistic roles of mycobacterial RecX proteins and the functional significance of the extended N-terminus of MsRecX. The full-length MsRecX acts as an antagonist of RecA, negatively regulating RecA promoted functions, including DNA strand exchange, LexA cleavage and ATP hydrolysis, but not binding of ATP. The N-terminally truncated MsRecX variants retain the RecA inhibitory activity, albeit with lower efficiencies compared to the full-length protein. Perhaps most importantly, direct visualization of RecA nucleoprotein filaments, which had been incubated with RecX proteins, showed that they promote disassembly of nucleoprotein filaments primarily within the filaments. In addition, interaction of RecX proteins with the RecA nucleoprotein filaments results in the formation of stiff and irregularly shaped nucleoprotein filaments. Thus, these findings add an additional mechanism by which RecX disassembles RecA nucleoprotein filaments. Overall, this study provides strong evidence for the notion that the N-terminal 14 amino acid region of MsRecX plays an important role in the negative regulation of RecA functions and new insights into the molecular mechanism underlying RecX function.
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Affiliation(s)
- Deepika Prasad
- Department of Biochemistry, Indian Institute of Science, Bengaluru 560012, India
| | - Kalappa Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bengaluru 560012, India.
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2
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Hans S, Purkait D, Nandan S, Bansal M, Hameed S, Fatima Z. Rec A disruption unveils cross talk between DNA repair and membrane damage, efflux pump activity, biofilm formation in Mycobacterium smegmatis. Microb Pathog 2020; 149:104262. [PMID: 32439563 DOI: 10.1016/j.micpath.2020.104262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 05/06/2020] [Accepted: 05/12/2020] [Indexed: 10/24/2022]
Abstract
Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) has emerged in recent decades as one of the leading causes of mortality worldwide. The burden of TB is alarmingly high, with one third affected global population as reported by WHO. Short-course treatment with an antibiotic is a powerful weapon to treat infection of susceptible MTB strain, however; MTB has developed resistance to anti-TB drugs, which is an escalating global health crisis. Thus there is urgent need to identify new drug targets. RecA is a 38 kilodalton protein required for the repair and maintenance of DNA and regulation of the SOS response. The objective of this study is to understand the effect of disruption of RecA gene (deletion mutant ΔdisA from previous study) in a surrogate model for MTB, Mycobacterium smegmatis. This study demonstrated that disruption of RecA causes enhanced susceptibility towards rifampicin and generation of ROS leading to lipid peroxidation and impaired membrane homeostasis as depicted by altered cell membrane permeability and efflux pump activity. Mass spectrometry based lipidomic analysis revealed decreased mycolic acid moieties, phosphatidylinositol mannosides (PIM), Phthiocerol dimycocerosate (DIM). Furthermore, biofilm formation was considerably reduced. Additionally, we have validated all the disrupted phenotypes by RT-PCR which showed a good correlation with the biochemical assays. Lastly, RecA mutant displayed reduced infectivity in Caenorhabditis elegans illustrating its vulnerability as antimycobacterial target. Together, present study establishes a link between DNA repair, drug efflux and biofilm formation and validates RecA as an effective drug target. Intricate studies are needed to further understand and exploit this therapeutic opportunity.
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Affiliation(s)
- Sandeep Hans
- Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Manesar, 122413, India
| | - Dyuti Purkait
- Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Manesar, 122413, India
| | - Shiv Nandan
- Amity Lipidomics Research Facility, Amity University Haryana, Gurugram, Manesar, 122413, India
| | - Maghav Bansal
- Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Manesar, 122413, India
| | - Saif Hameed
- Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Manesar, 122413, India.
| | - Zeeshan Fatima
- Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Manesar, 122413, India.
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Kim SH, Park J, Joo C, Kim D, Ha T. Dynamic growth and shrinkage govern the pH dependence of RecA filament stability. PLoS One 2015; 10:e0115611. [PMID: 25608006 PMCID: PMC4301630 DOI: 10.1371/journal.pone.0115611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 11/30/2014] [Indexed: 11/19/2022] Open
Abstract
RecA proteins form a long stable filament on a single-stranded DNA and catalyze strand exchange reaction. The stability of RecA filament changes dramatically with pH, yet its detailed mechanism is not known. Here, using a single molecule assay, we determined the binding and dissociation rates of RecA monomers at the filament ends at various pH. The pH-induced rate changes were moderate but occurred in opposite directions for binding and dissociation, resulting in a substantial increase in filament stability in lower pH. The highly charged residues in C-terminal domain do not contribute to the pH dependent stability. The stability enhancement of RecA filament in low pH may help the cell to cope with acidic stress by fine-tuning of the binding and dissociation rates without losing the highly dynamic nature of the filament required for strand exchange.
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Affiliation(s)
- Sung Hyun Kim
- Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul, Korea
| | - Jeehae Park
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Chirlmin Joo
- Kavli Institute of NanoScience, Department of BioNanoScience, Delft University of Technology, Delft, The Netherlands
| | - Doseok Kim
- Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul, Korea
- * E-mail: (TH); (DK)
| | - Taekjip Ha
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Howard Hughes Medical Institute, Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail: (TH); (DK)
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Nautiyal A, Patil KN, Muniyappa K. Suramin is a potent and selective inhibitor of Mycobacterium tuberculosis RecA protein and the SOS response: RecA as a potential target for antibacterial drug discovery. J Antimicrob Chemother 2014; 69:1834-43. [PMID: 24722837 DOI: 10.1093/jac/dku080] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
OBJECTIVES In eubacteria, RecA is essential for recombinational DNA repair and for stalled replication forks to resume DNA synthesis. Recent work has implicated a role for RecA in the development of antibiotic resistance in pathogenic bacteria. Consequently, our goal is to identify and characterize small-molecule inhibitors that target RecA both in vitro and in vivo. METHODS We employed ATPase, DNA strand exchange and LexA cleavage assays to elucidate the inhibitory effects of suramin on Mycobacterium tuberculosis RecA. To gain insights into the mechanism of suramin action, we directly visualized the structure of RecA nucleoprotein filaments by atomic force microscopy. To determine the specificity of suramin action in vivo, we investigated its effect on the SOS response by pull-down and western blot assays as well as for its antibacterial activity. RESULTS We show that suramin is a potent inhibitor of DNA strand exchange and ATPase activities of bacterial RecA proteins with IC(50) values in the low micromolar range. Additional evidence shows that suramin inhibits RecA-catalysed proteolytic cleavage of the LexA repressor. The mechanism underlying such inhibitory actions of suramin involves its ability to disassemble RecA-single-stranded DNA filaments. Notably, suramin abolished ciprofloxacin-induced recA gene expression and the SOS response and augmented the bactericidal action of ciprofloxacin. CONCLUSIONS Our findings suggest a strategy to chemically disrupt the vital processes controlled by RecA and hence the promise of small molecules for use against drug-susceptible as well as drug-resistant strains of M. tuberculosis for better infection control and the development of new therapies.
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Affiliation(s)
- Astha Nautiyal
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | | | - K Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Fu H, Le S, Muniyappa K, Yan J. Dynamics and Regulation of RecA Polymerization and De-Polymerization on Double-Stranded DNA. PLoS One 2013; 8:e66712. [PMID: 23825559 PMCID: PMC3688958 DOI: 10.1371/journal.pone.0066712] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 05/09/2013] [Indexed: 11/19/2022] Open
Abstract
The RecA filament formed on double-stranded (ds) DNA is proposed to be a functional state analogous to that generated during the process of DNA strand exchange. RecA polymerization and de-polymerization on dsDNA is governed by multiple physiological factors. However, a comprehensive understanding of how these factors regulate the processes of polymerization and de-polymerization of RecA filament on dsDNA is still evolving. Here, we investigate the effects of temperature, pH, tensile force, and DNA ends (in particular ssDNA overhang) on the polymerization and de-polymerization dynamics of the E. coli RecA filament at a single-molecule level. Our results identified the optimal conditions that permitted spontaneous RecA nucleation and polymerization, as well as conditions that could maintain the stability of a preformed RecA filament. Further examination at a nano-meter spatial resolution, by stretching short DNA constructs, revealed a striking dynamic RecA polymerization and de-polymerization induced saw-tooth pattern in DNA extension fluctuation. In addition, we show that RecA does not polymerize on S-DNA, a recently identified novel base-paired elongated DNA structure that was previously proposed to be a possible binding substrate for RecA. Overall, our studies have helped to resolve several previous single-molecule studies that reported contradictory and inconsistent results on RecA nucleation, polymerization and stability. Furthermore, our findings also provide insights into the regulatory mechanisms of RecA filament formation and stability in vivo.
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Affiliation(s)
- Hongxia Fu
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Shimin Le
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Kalappa Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Department of Physics, National University of Singapore, Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
- * E-mail:
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Fu H, Le S, Chen H, Muniyappa K, Yan J. Force and ATP hydrolysis dependent regulation of RecA nucleoprotein filament by single-stranded DNA binding protein. Nucleic Acids Res 2012; 41:924-32. [PMID: 23221642 PMCID: PMC3553936 DOI: 10.1093/nar/gks1162] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
In Escherichia coli, the filament of RecA formed on single-stranded DNA (ssDNA) is essential for recombinational DNA repair. Although ssDNA-binding protein (SSB) plays a complicated role in RecA reactions in vivo, much of our understanding of the mechanism is based on RecA binding directly to ssDNA. Here we investigate the role of SSB in the regulation of RecA polymerization on ssDNA, based on the differential force responses of a single 576-nucleotide-long ssDNA associated with RecA and SSB. We find that SSB outcompetes higher concentrations of RecA, resulting in inhibition of RecA nucleation. In addition, we find that pre-formed RecA filaments de-polymerize at low force in an ATP hydrolysis- and SSB-dependent manner. At higher forces, re-polymerization takes place, which displaces SSB from ssDNA. These findings provide a physical picture of the competition between RecA and SSB under tension on the scale of the entire nucleoprotein SSB array, which have broad biological implications particularly with regard to competitive molecular binding.
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Affiliation(s)
- Hongxia Fu
- Mechanobiology Institute, National University of Singapore, 117411 Singapore
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Abstract
The action of RecA, an important eubacterial protein involved in recombination and repair, involves the transition from an inactive filament in the absence of DNA to an active filament formed in association with DNA and ATP. The structure of the inactive filament was first established in Escherichia coli RecA (EcRecA). The interaction of RecA with non-hydrolysable ATP analogues and ADP has been thoroughly characterized and the DNA binding loops visualized based on the crystal structures of the RecA proteins from Mycobacterium tuberculosis (MtRecA) and Mycobacterium smegmatis (MsRecA). A switch residue, which triggers the transformation of the information on ATP binding to the DNA binding regions, has been identified. The 20-residue C-terminal stretch of RecA, which is disordered in all other relevant crystal structures, has been defined in an MsRecA-dATP complex. The ordering of the stretch is accompanied by the generation of a new nucleotide binding site which can communicate with the original nucleotide binding site of an adjacent molecule in the filament. The plasticity of MsRecA and its mutants involving the switch residue has been explored by studying crystals grown under different conditions at two different temperatures and, in one instance, at low humidity. The structures of these crystals and those of EcRecA and Deinococcus radiodurans RecA (DrRecA) provide information on correlated movements involving different regions of the molecule. These correlated movements appear to be important in the allosteric transitions of RecA during its action.
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Patil KN, Singh P, Harsha S, Muniyappa K. Mycobacterium leprae RecA is structurally analogous but functionally distinct from Mycobacterium tuberculosis RecA protein. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1802-11. [DOI: 10.1016/j.bbapap.2011.09.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/18/2011] [Accepted: 09/23/2011] [Indexed: 11/28/2022]
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Sharadamma N, Khan K, Kumar S, Patil KN, Hasnain SE, Muniyappa K. Synergy between the N-terminal and C-terminal domains of Mycobacterium tuberculosis HupB is essential for high-affinity binding, DNA supercoiling and inhibition of RecA-promoted strand exchange. FEBS J 2011; 278:3447-62. [PMID: 21787377 DOI: 10.1111/j.1742-4658.2011.08267.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The occurrence of DNA architectural proteins containing two functional domains derived from two different architectural proteins is an interesting emerging research theme in the field of nucleoid structure and function. Mycobacterium tuberculosis HupB, unlike Escherichia coli HU, is a two-domain protein that, in the N-terminal region, shows broad sequence homology with bacterial HU. The long C-terminal extension, on the other hand, contains seven PAKK/KAAK motifs, which are characteristic of the histone H1/H5 family of proteins. In this article, we describe several aspects of HupB function, in comparison with its truncated derivatives lacking either the C-terminus or N-terminus. We found that HupB binds a variety of DNA repair and replication intermediates with K(d) values in the nanomolar range. By contrast, the N-terminal fragment of M. tuberculosis HupB (HupB(MtbN)) showed diminished DNA-binding activity, with K(d) values in the micromolar range, and the C-terminal domain was completely devoid of DNA-binding activity. Unlike HupB(MtbN) , HupB was able to constrain DNA in negative supercoils and introduce negative superhelical turns into relaxed DNA. Similarly, HupB exerted a robust inhibitory effect on DNA strand exchange promoted by cognate and noncognate RecA proteins, whereas HupB(MtbN), even at a 50-fold molar excess, had no inhibitory effect. Considered together, these results suggest that synergy between the N-terminal and C-terminal domains of HupB is essential for its DNA-binding ability, and to modulate the topological features of DNA, which has implications for processes such as DNA compaction, gene regulation, homologous recombination, and DNA repair.
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Affiliation(s)
- N Sharadamma
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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10
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Patil KN, Singh P, Muniyappa K. DNA Binding, Coprotease, and Strand Exchange Activities of Mycobacterial RecA Proteins: Implications for Functional Diversity among RecA Nucleoprotein Filaments. Biochemistry 2010; 50:300-11. [DOI: 10.1021/bi1018013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Pawan Singh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - K. Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Singh P, Patil KN, Khanduja JS, Kumar PS, Williams A, Rossi F, Rizzi M, Davis EO, Muniyappa K. Mycobacterium tuberculosis UvrD1 and UvrA proteins suppress DNA strand exchange promoted by cognate and noncognate RecA proteins. Biochemistry 2010; 49:4872-83. [PMID: 20455546 DOI: 10.1021/bi902021d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
DNA helicases are present in all kingdoms of life and play crucial roles in processes of DNA metabolism such as replication, repair, recombination, and transcription. To date, however, the role of DNA helicases during homologous recombination in mycobacteria remains unknown. In this study, we show that Mycobacterium tuberculosis UvrD1 more efficiently inhibited the strand exchange promoted by its cognate RecA, compared to noncognate Mycobacterium smegmatis or Escherichia coli RecA proteins. The M. tuberculosis UvrD1(Q276R) mutant lacking the helicase and ATPase activities was able to block strand exchange promoted by mycobacterial RecA proteins but not of E. coli RecA. We observed that M. tuberculosis UvrA by itself has no discernible effect on strand exchange promoted by E. coli RecA but impedes the reaction catalyzed by the mycobacterial RecA proteins. Our data also show that M. tuberculosis UvrA and UvrD1 can act together to inhibit strand exchange promoted by mycobacterial RecA proteins. Taken together, these findings raise the possibility that UvrD1 and UvrA might act together in vivo to counter the deleterious effects of RecA nucleoprotein filaments and/or facilitate the dissolution of recombination intermediates. Finally, we provide direct experimental evidence for a physical interaction between M. tuberculosis UvrD1 and RecA on one hand and RecA and UvrA on the other hand. These observations are consistent with a molecular mechanism, whereby M. tuberculosis UvrA and UvrD1, acting together, block DNA strand exchange promoted by cognate and noncognate RecA proteins.
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Affiliation(s)
- Pawan Singh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Sharadamma N, Harshavardhana Y, Singh P, Muniyappa K. Mycobacterium tuberculosis nucleoid-associated DNA-binding protein H-NS binds with high-affinity to the Holliday junction and inhibits strand exchange promoted by RecA protein. Nucleic Acids Res 2010; 38:3555-69. [PMID: 20176569 PMCID: PMC2887947 DOI: 10.1093/nar/gkq064] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
A number of studies have shown that the structure and composition of bacterial nucleoid influences many a processes related to DNA metabolism. The nucleoid-associated proteins modulate not only the DNA conformation but also regulate the DNA metabolic processes such as replication, recombination, repair and transcription. Understanding of how these processes occur in the context of Mycobacterium tuberculosis nucleoid is of considerable medical importance because the nucleoid structure may be constantly remodeled in response to environmental signals and/or growth conditions. Many studies have concluded that Escherichia coli H-NS binds to DNA in a sequence-independent manner, with a preference for A-/T-rich tracts in curved DNA; however, recent studies have identified the existence of medium- and low-affinity binding sites in the vicinity of the curved DNA. Here, we show that the M. tuberculosis H-NS protein binds in a more structure-specific manner to DNA replication and repair intermediates, but displays lower affinity for double-stranded DNA with relatively higher GC content. Notably, M. tuberculosis H-NS was able to bind Holliday junction (HJ), the central recombination intermediate, with substantially higher affinity and inhibited the three-strand exchange promoted by its cognate RecA. Likewise, E. coli H-NS was able to bind the HJ and suppress DNA strand exchange promoted by E. coli RecA, although much less efficiently compared to M. tuberculosis H-NS. Our results provide new insights into a previously unrecognized function of H-NS protein, with implications for blocking the genome integration of horizontally transferred genes by homologous and/or homeologous recombination.
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Affiliation(s)
- N Sharadamma
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Dos Vultos T, Mestre O, Tonjum T, Gicquel B. DNA repair inMycobacterium tuberculosisrevisited. FEMS Microbiol Rev 2009; 33:471-87. [DOI: 10.1111/j.1574-6976.2009.00170.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Khanduja JS, Tripathi P, Muniyappa K. Mycobacterium tuberculosis RuvA induces two distinct types of structural distortions between the homologous and heterologous Holliday junctions. Biochemistry 2009; 48:27-40. [PMID: 19072585 DOI: 10.1021/bi8016526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A central step in the process of homologous genetic recombination is the strand exchange between two homologous DNA molecules, leading to the formation of the Holliday junction intermediate. Several lines of evidence, both in vitro and in vivo, suggest a concerted role for the Escherichia coli RuvABC protein complex in the process of branch migration and the resolution of the Holliday junctions. A number of investigations have examined the role of RuvA protein in branch migration of the Holliday junction in conjunction with its natural cellular partner, RuvB. However, it remains unclear whether the RuvABC protein complex or its individual subunits function differently in the context of DNA repair and homologous recombination. In this study, we have specifically investigated the function of RuvA protein using Holliday junctions containing either homologous or heterologous arms. Our data show that Mycobacterium tuberculosis ruvA complements E. coli DeltaruvA mutants for survival to genotoxic stress caused by different DNA-damaging agents, and the purified RuvA protein binds HJ in preference to any other substrates. Strikingly, our analysis revealed two distinct types of structural distortions caused by M. tuberculosis RuvA between the homologous and heterologous Holliday junctions. We interpret these data as evidence that local distortion of base pairing in the arms of homologous Holliday junctions by RuvA might augment branch migration catalyzed by RuvB. The biological significance of two modes of structural distortion caused by M. tuberculosis RuvA and the implications for its role in DNA repair and homologous recombination are discussed.
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Abstract
As part of an international effort and a national programme, structural analysis of mycobacterial proteins involved in recombination and repair, stringent response and protein synthesis has been undertaken, and work on proteins in a couple of metabolic pathways has been initiated. Already X-ray analysed are Mycobacterium tuberculosis and Mycobacterium smegmatis RecA and their nucleotide complexes, and different crystal forms of M. tuberculosis single-stranded DNA binding protein, M. smegmatis DNA binding protein from stationary phase cells and M. tuberculosis ribosome recycling factor. A comparative study involving these structures and those of similar proteins from other sources brings out the special features of the mycobacterial proteins, which are likely to be useful in selective inhibitor design. The structures provide insights into the plasticity of the molecules and its biological implications, and yield valuable information on their assembly and quaternary structure. They also provide leads for further structural investigations.
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Affiliation(s)
- M Vijayan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
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16
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Ganesh N, Muniyappa K. Mycobacterium smegmatis RecA protein is structurally similar to but functionally distinct from Mycobacterium tuberculosis RecA. Proteins 2003; 53:6-17. [PMID: 12945045 DOI: 10.1002/prot.10433] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In eubacteria, RecA proteins belong to a large superfamily of evolutionarily conserved, filament-forming, functional homologs of DNA strand exchange proteins. Here, we report the functional characterization of Mycobacterium smegmatis (Ms) and Mycobacterium tuberculosis (Mt) RecA proteins. Although in some respects Ms and Mt RecA proteins are structural and functional homologs of Escherichia coli (Ec) RecA, there are significant differences as well. The single-stranded DNA-binding property of RecA proteins was analyzed by electrophoretic mobility shift assays. We observed that Ms or Mt RecA proteins bound single-stranded DNA in a manner distinct from that of Ec RecA: The former two were able to form protein-DNA complexes in the presence of high salt. Further experiments indicated that Ms or Mt RecA proteins catalyzed adenosine triphosphate hydrolysis at approximately comparable rates across a wide range of pHs. Significantly, DNA strand invasion promoted by Ms or Mt RecA proteins displayed similar kinetics but distinctly different pH profiles. In contrast to MtRecA, MsRecA by itself was unable to form joint molecules across a wide range of pHs. However, regardless of the order in which SSB was added, it was able to stimulate MsRecA to form joint molecules within a narrow pH range, indicating that SSB is a required accessory factor. Together, these results provide a source of sharp contrast between EcRecA and mycobacterial RecAs on the one hand and Mt and Ms RecA proteins on the other.
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Affiliation(s)
- N Ganesh
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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Tyagi AK, Dhar N. Recent advances in tuberculosis research in India. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2003; 84:211-73. [PMID: 12934938 DOI: 10.1007/3-540-36488-9_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Tuberculosis (TB) continues to be the leading killer of mankind among all infectious diseases, especially in the developing countries. Since the discovery of tubercle bacillus more than 100 years ago, TB has been the subject of research in an attempt to develop tools and strategies to combat this disease. Research in Indian laboratories has contributed significantly towards developing the DOTS strategy employed worldwide in tuberculosis control programmes and elucidating the biological properties of its etiologic agent, M. tuberculosis. In recent times, the development of tools for manipulation of mycobacteria has given a boost to researchers working in this field. New strategies are being employed towards understanding the mechanisms of protection and pathogenesis of this disease. Molecular methods are being applied to develop new tools and reagents for prevention, diagnosis and treatment of tuberculosis. With the sequencing of the genome of M. tuberculosis, molecules are being identified for the development of new drugs and vaccines. In this chapter, the advances made in these areas by Indian researchers mainly during the last five years are reviewed.
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Affiliation(s)
- Anil K Tyagi
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021, India.
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Datta S, Ganesh N, Chandra NR, Muniyappa K, Vijayan M. Structural studies on MtRecA-nucleotide complexes: insights into DNA and nucleotide binding and the structural signature of NTP recognition. Proteins 2003; 50:474-85. [PMID: 12557189 DOI: 10.1002/prot.10315] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RecA protein plays a crucial role in homologous recombination and repair of DNA. Central to all activities of RecA is its binding to Mg(+2)-ATP. The active form of the protein is a helical nucleoprotein filament containing the nucleotide cofactor and single-stranded DNA. The stability and structure of the helical nucleoprotein filament formed by RecA are modulated by nucleotide cofactors. Here we report crystal structures of a MtRecA-ADP complex, complexes with ATPgammaS in the presence and absence of magnesium as well as a complex with dATP and Mg+2. Comparison with the recently solved crystal structures of the apo form as well as a complex with ADP-AlF4 confirms an expansion of the P-loop region in MtRecA, compared to its homologue in Escherichia coli, correlating with the reduced affinity of MtRecA for ATP. The ligand bound structures reveal subtle variations in nucleotide conformations among different nucleotides that serve in maintaining the network of interactions crucial for nucleotide binding. The nucleotide binding site itself, however, remains relatively unchanged. The analysis also reveals that ATPgammaS rather than ADP-AlF4 is structurally a better mimic of ATP. From among the complexed structures, a definition for the two DNA-binding loops L1 and L2 has clearly emerged for the first time and provides a basis to understand DNA binding by RecA. The structural information obtained from these complexes correlates well with the extensive biochemical data on mutants available in the literature, contributing to an understanding of the role of individual residues in the nucleotide binding pocket, at the molecular level. Modeling studies on the mutants again point to the relative rigidity of the nucleotide binding site. Comparison with other NTP binding proteins reveals many commonalties in modes of binding by diverse members in the structural family, contributing to our understanding of the structural signature of NTP recognition.
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Affiliation(s)
- S Datta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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Venkatesh R, Ganesh N, Guhan N, Reddy MS, Chandrasekhar T, Muniyappa K. RecX protein abrogates ATP hydrolysis and strand exchange promoted by RecA: insights into negative regulation of homologous recombination. Proc Natl Acad Sci U S A 2002; 99:12091-6. [PMID: 12218174 PMCID: PMC129403 DOI: 10.1073/pnas.192178999] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many eubacteria, coexpression of recX with recA is essential for attenuation of the deleterious effects of recA overexpression; however, the molecular mechanism has remained enigmatic. Here, we show that Mycobacterium tuberculosis RecX binds directly to M. tuberculosis RecA as well as M. smegmatis and E. coli RecA proteins in vivo and in vitro, but not single-stranded DNA binding protein. The direct association of RecX with RecA failed to regulate the specificity or extent of binding of RecA either to DNA or ATP, ligands that are central to activation of its functions. Significantly, RecX severely impeded ATP hydrolysis and the generation of heteroduplex DNA promoted by homologous, as well as heterologous, RecA proteins. These findings reveal a mode of negative regulation of RecA, and imply that RecX might act as an anti-recombinase to quell inappropriate recombinational repair during normal DNA metabolism.
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Affiliation(s)
- R Venkatesh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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20
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Guhan N, Muniyappa K. Mycobacterium tuberculosis RecA intein possesses a novel ATP-dependent site-specific double-stranded DNA endonuclease activity. J Biol Chem 2002; 277:16257-64. [PMID: 11850426 DOI: 10.1074/jbc.m112365200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mycobacterium tuberculosis recA harbors an intervening sequence in its open reading frame, presumed to encode an endonuclease (PI-MtuI) required for intein homing in inteinless recA allele. Although the protein-splicing ability of PI-MtuI has been characterized, the identification of its putative endonuclease activity has remained elusive. To investigate whether PI-MtuI possesses endonuclease activity, recA intervening sequence was cloned, overexpressed, and purified to homogeneity. Here we show that PI-MtuI bound both single- and double-stranded DNA with similar affinity but failed to cleave DNA in the absence of cofactors. Significantly, PI-MtuI nicked supercoiled DNA in the presence of alternative cofactors but required both Mn(2+) and ATP to generate linear double-stranded DNA. We observed that PI-MtuI was able to inflict a staggered double-strand break 24 bp upstream of the insertion site in the inteinless recA allele. Similar to a few homing endonucleases, DNA cleavage by PI-MtuI was specific with an exceptionally long cleavage site spanning 22 bp. The kinetic mechanism of PI-MtuI promoted cleavage supports a sequential rather than concerted pathway of strand cleavage with the formation of nicked double-stranded DNA as an intermediate. Together, these results reveal that RecA intein is a novel Mn(2+)-ATP-dependent double-strand specific endonuclease, which is likely to be important for homing process in vivo.
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Affiliation(s)
- N Guhan
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Reddy MS, Guhan N, Muniyappa K. Characterization of single-stranded DNA-binding proteins from Mycobacteria. The carboxyl-terminal of domain of SSB is essential for stable association with its cognate RecA protein. J Biol Chem 2001; 276:45959-68. [PMID: 11577073 DOI: 10.1074/jbc.m103523200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Single-stranded DNA-binding proteins (SSB) play an important role in most aspects of DNA metabolism including DNA replication, repair, and recombination. We report here the identification and characterization of SSB proteins of Mycobacterium smegmatis and Mycobacterium tuberculosis. Sequence comparison of M. smegmatis SSB revealed that it is homologous to M. tuberculosis SSB, except for a small spacer connecting the larger amino-terminal domain with the extreme carboxyl-terminal tail. The purified SSB proteins of mycobacteria bound single-stranded DNA with high affinity, and the association and dissociation constants were similar to that of the prototype SSB. The proteolytic signatures of free and bound forms of SSB proteins disclosed that DNA binding was associated with structural changes at the carboxyl-terminal domain. Significantly, SSB proteins from mycobacteria displayed high affinity for cognate RecA, whereas Escherichia coli SSB did not under comparable experimental conditions. Accordingly, SSB and RecA were coimmunoprecipitated from cell lysates, further supporting an interaction between these proteins in vivo. The carboxyl-terminal domain of M. smegmatis SSB, which is not essential for interaction with ssDNA, is the site of binding of its cognate RecA. These studies provide the first evidence for stable association of eubacterial SSB proteins with their cognate RecA, suggesting that these two proteins might function together during DNA repair and/or recombination.
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Affiliation(s)
- M S Reddy
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Sander P, Papavinasasundaram KG, Dick T, Stavropoulos E, Ellrott K, Springer B, Colston MJ, Böttger EC. Mycobacterium bovis BCG recA deletion mutant shows increased susceptibility to DNA-damaging agents but wild-type survival in a mouse infection model. Infect Immun 2001; 69:3562-8. [PMID: 11349014 PMCID: PMC98336 DOI: 10.1128/iai.69.6.3562-3568.2001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic microorganisms possess antioxidant defense mechanisms for protection from reactive oxygen metabolites which are generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxifies reactive oxygen species, and DNA repair systems, which repair damage resulting from oxidative stress. To (i) determine the relative importance of the DNA repair system when oxidative stress is encountered by the Mycobacterium tuberculosis complex during infection of the host and to (ii) provide improved mycobacterial hosts as live carriers to express foreign antigens, the recA locus was inactivated by allelic exchange in Mycobacterium bovis BCG. The recA mutants are sensitive to DNA-damaging agents and show increased susceptibility to metronidazole, the first lead compound active against the dormant M. tuberculosis complex. Surprisingly, the recA genotype does not affect the in vitro dormancy response, nor does the defect in the DNA repair system lead to attenuation as determined in a mouse infection model. The recA mutants will be a valuable tool for further development of BCG as an antigen delivery system to express foreign antigens and as a source of a genetically stable vaccine against tuberculosis.
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Affiliation(s)
- P Sander
- Institut für Medizinische Mikrobiologie, Medizinische Hochschule Hannover, Germany.
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Datta S, Prabu MM, Vaze MB, Ganesh N, Chandra NR, Muniyappa K, Vijayan M. Crystal structures of Mycobacterium tuberculosis RecA and its complex with ADP-AlF(4): implications for decreased ATPase activity and molecular aggregation. Nucleic Acids Res 2000; 28:4964-73. [PMID: 11121488 PMCID: PMC115232 DOI: 10.1093/nar/28.24.4964] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Sequencing of the complete genome of Mycobacterium tuberculosis, combined with the rapidly increasing need to improve tuberculosis management through better drugs and vaccines, has initiated extensive research on several key proteins from the pathogen. RecA, a ubiquitous multifunctional protein, is a key component of the processes of homologous genetic recombination and DNA repair. Structural knowledge of MtRecA is imperative for a full understanding of both these activities and any ensuing application. The crystal structure of MtRecA, presented here, has six molecules in the unit cell forming a 6(1) helical filament with a deep groove capable of binding DNA. The observed weakening in the higher order aggregation of filaments into bundles may have implications for recombination in mycobacteria. The structure of the complex reveals the atomic interactions of ADP-AlF(4), an ATP analogue, with the P-loop-containing binding pocket. The structures explain reduced levels of interactions of MtRecA with ATP, despite sharing the same fold, topology and high sequence similarity with EcRecA. The formation of a helical filament with a deep groove appears to be an inherent property of MtRecA. The histidine in loop L1 appears to be positioned appropriately for DNA interaction.
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Affiliation(s)
- S Datta
- Molecular Biophysics Unit, Department of Biochemistry and Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India
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Abstract
Five new inteins were discovered in a survey of 39 mycobacterial strains that was undertaken to clarify the role of RecA inteins in mycobacteria. They are all inserted at the RecA-b site of the recA gene of Mycobacterium chitae, 4. fallax, M. gastri, M. shimodei and M. thermoresistibile and belong to the MleRecA allelic family. Sequence analysis showed that although only M. tuberculosis harbours an intein at the RecA-a site the sequence of the RecA-b site is well conserved between species. Furthermore, the presence of inteins does not correlate with specific characteristics of the species such as pathogenicity or growth rate.
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Affiliation(s)
- I Saves
- Institut de Pharmacologie et Biologie Structurale UMR5089, CNRS Université Paul Sabatier Toulouse III, Toulouse, France.
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