1
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Lee KY, Lee BJ. Dynamics-Based Regulatory Switches of Type II Antitoxins: Insights into New Antimicrobial Discovery. Antibiotics (Basel) 2023; 12:antibiotics12040637. [PMID: 37106997 PMCID: PMC10135005 DOI: 10.3390/antibiotics12040637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/20/2023] [Accepted: 03/22/2023] [Indexed: 04/29/2023] Open
Abstract
Type II toxin-antitoxin (TA) modules are prevalent in prokaryotes and are involved in cell maintenance and survival under harsh environmental conditions, including nutrient deficiency, antibiotic treatment, and human immune responses. Typically, the type II TA system consists of two protein components: a toxin that inhibits an essential cellular process and an antitoxin that neutralizes its toxicity. Antitoxins of type II TA modules typically contain the structured DNA-binding domain responsible for TA transcription repression and an intrinsically disordered region (IDR) at the C-terminus that directly binds to and neutralizes the toxin. Recently accumulated data have suggested that the antitoxin's IDRs exhibit variable degrees of preexisting helical conformations that stabilize upon binding to the corresponding toxin or operator DNA and function as a central hub in regulatory protein interaction networks of the type II TA system. However, the biological and pathogenic functions of the antitoxin's IDRs have not been well discussed compared with those of IDRs from the eukaryotic proteome. Here, we focus on the current state of knowledge about the versatile roles of IDRs of type II antitoxins in TA regulation and provide insights into the discovery of new antibiotic candidates that induce toxin activation/reactivation and cell death by modulating the regulatory dynamics or allostery of the antitoxin.
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Affiliation(s)
- Ki-Young Lee
- College of Pharmacy and Institute of Pharmaceutical Sciences, CHA University, Pocheon-si 11160, Republic of Korea
| | - Bong-Jin Lee
- College of Pharmacy, Seoul National University, Seoul 08826, Republic of Korea
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2
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Eun HJ, Lee J, Kang SJ, Lee BJ. The structural and functional investigation of the VapBC43 complex from Mycobacterium tuberculosis. Biochem Biophys Res Commun 2022; 616:19-25. [DOI: 10.1016/j.bbrc.2022.05.061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 05/17/2022] [Indexed: 11/02/2022]
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3
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Abstract
Toxin-antitoxin systems are widespread in bacterial genomes. They are usually composed of two elements: a toxin that inhibits an essential cellular process and an antitoxin that counteracts its cognate toxin. In the past decade, a number of new toxin-antitoxin systems have been described, bringing new growth inhibition mechanisms to light as well as novel modes of antitoxicity. However, recent advances in the field profoundly questioned the role of these systems in bacterial physiology, stress response and antimicrobial persistence. This shifted the paradigm of the functions of toxin-antitoxin systems to roles related to interactions between hosts and their mobile genetic elements, such as viral defence or plasmid stability. In this Review, we summarize the recent progress in understanding the biology and evolution of these small genetic elements, and discuss how genomic conflicts could shape the diversification of toxin-antitoxin systems.
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4
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Grabe GJ, Giorgio RT, Hall AMJ, Morgan RML, Dubois L, Sisley TA, Rycroft JA, Hare SA, Helaine S. Auxiliary interfaces support the evolution of specific toxin-antitoxin pairing. Nat Chem Biol 2021; 17:1296-1304. [PMID: 34556858 DOI: 10.1038/s41589-021-00862-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/20/2021] [Indexed: 02/08/2023]
Abstract
Toxin-antitoxin (TA) systems are a large family of genes implicated in the regulation of bacterial growth and its arrest in response to attacks. These systems encode nonsecreted toxins and antitoxins that specifically pair, even when present in several paralogous copies per genome. Salmonella enterica serovar Typhimurium contains three paralogous TacAT systems that block bacterial translation. We determined the crystal structures of the three TacAT complexes to understand the structural basis of specific TA neutralization and the evolution of such specific pairing. In the present study, we show that alteration of a discrete structural add-on element on the toxin drives specific recognition by their cognate antitoxin underpinning insulation of the three pairs. Similar to other TA families, the region supporting TA-specific pairing is key to neutralization. Our work reveals that additional TA interfaces beside the main neutralization interface increase the safe space for evolution of pairing specificity.
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Affiliation(s)
- Grzegorz J Grabe
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Rachel T Giorgio
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | | | | | - Laurent Dubois
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Tyler A Sisley
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Julian A Rycroft
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Stephen A Hare
- School of Life Sciences, University of Sussex, Brighton, UK
| | - Sophie Helaine
- Department of Microbiology, Harvard Medical School, Boston, MA, USA. .,MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
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5
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Xue L, Khan MH, Yue J, Zhu Z, Niu L. The two paralogous copies of the YoeB-YefM toxin-antitoxin module in Staphylococcus aureus differ in DNA binding and recognition patterns. J Biol Chem 2021; 298:101457. [PMID: 34861238 PMCID: PMC8717551 DOI: 10.1016/j.jbc.2021.101457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 11/24/2021] [Accepted: 11/25/2021] [Indexed: 12/13/2022] Open
Abstract
Toxin-antitoxin (TA) systems are ubiquitous regulatory modules for bacterial growth and cell survival following stress. YefM-YoeB, the most prevalent type II TA system, is present in a variety of bacterial species. In Staphylococcus aureus, the YefM-YoeB system exists as two independent paralogous copies. Our previous research resolved crystal structures of the two oligomeric states (heterotetramer and heterohexamer-DNA ternary complex) of the first paralog as well as the molecular mechanism of transcriptional autoregulation of this module. However, structural details reflecting molecular diversity in both paralogs have been relatively unexplored. To understand the molecular mechanism of how Sa2YoeB and Sa2YefM regulate their own transcription and how each paralog functions independently, we solved a series of crystal structures of the Sa2YoeB-Sa2YefM. Our structural and biochemical data demonstrated that both paralogous copies adopt similar mechanisms of transcriptional autoregulation. In addition, structural analysis suggested that molecular diversity between the two paralogs might be reflected in the interaction profile of YefM and YoeB and the recognition pattern of promoter DNA by YefM. Interaction analysis revealed unique conformational and activating force effected by the interface between Sa2YoeB and Sa2YefM. In addition, the recognition pattern analysis demonstrated that residues Thr7 and Tyr14 of Sa2YefM specifically recognizes the flanking sequences (G and C) of the promoter DNA. Together, these results provide the structural insights into the molecular diversity and independent function of the paralogous copies of the YoeB-YefM TA system.
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Affiliation(s)
- Lu Xue
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Molecular and Cellular Biophysics, University of Science and Technology of China, Hefei, Anhui, China; Division of Life Sciences and Medicine, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Muhammad Hidayatullah Khan
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Molecular and Cellular Biophysics, University of Science and Technology of China, Hefei, Anhui, China; Division of Life Sciences and Medicine, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Jian Yue
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Molecular and Cellular Biophysics, University of Science and Technology of China, Hefei, Anhui, China; Division of Life Sciences and Medicine, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Zhongliang Zhu
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Molecular and Cellular Biophysics, University of Science and Technology of China, Hefei, Anhui, China; Division of Life Sciences and Medicine, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
| | - Liwen Niu
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Molecular and Cellular Biophysics, University of Science and Technology of China, Hefei, Anhui, China; Division of Life Sciences and Medicine, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
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6
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Garcia-Rodriguez G, Girardin Y, Volkov AN, Singh RK, Muruganandam G, Van Dyck J, Sobott F, Versées W, Charlier D, Loris R. Entropic pressure controls the oligomerization of the Vibrio cholerae ParD2 antitoxin. Acta Crystallogr D Struct Biol 2021; 77:904-920. [PMID: 34196617 PMCID: PMC8251345 DOI: 10.1107/s2059798321004873] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 05/07/2021] [Indexed: 11/22/2022] Open
Abstract
ParD2 is the antitoxin component of the parDE2 toxin-antitoxin module from Vibrio cholerae and consists of an ordered DNA-binding domain followed by an intrinsically disordered ParE-neutralizing domain. In the absence of the C-terminal intrinsically disordered protein (IDP) domain, V. cholerae ParD2 (VcParD2) crystallizes as a doughnut-shaped hexadecamer formed by the association of eight dimers. This assembly is stabilized via hydrogen bonds and salt bridges rather than by hydrophobic contacts. In solution, oligomerization of the full-length protein is restricted to a stable, open decamer or dodecamer, which is likely to be a consequence of entropic pressure from the IDP tails. The relative positioning of successive VcParD2 dimers mimics the arrangement of Streptococcus agalactiae CopG dimers on their operator and allows an extended operator to wrap around the VcParD2 oligomer.
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Affiliation(s)
- Gabriela Garcia-Rodriguez
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Yana Girardin
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Alexander N. Volkov
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
- Jean Jeener NMR Center, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Ranjan Kumar Singh
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Gopinath Muruganandam
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jeroen Van Dyck
- Department of Chemistry, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Frank Sobott
- Department of Chemistry, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Wim Versées
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Daniel Charlier
- Research Group of Microbiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Remy Loris
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
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7
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Klemenčič M, Halužan Vasle A, Dolinar M. The Cysteine Protease MaOC1, a Prokaryotic Caspase Homolog, Cleaves the Antitoxin of a Type II Toxin-Antitoxin System. Front Microbiol 2021; 12:635684. [PMID: 33679669 PMCID: PMC7935541 DOI: 10.3389/fmicb.2021.635684] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/01/2021] [Indexed: 01/26/2023] Open
Abstract
The bloom-forming cyanobacterium Microcystis aeruginosa is known for its global distribution and for the production of toxic compounds. In the genome of M. aeruginosa PCC 7806, we discovered that the gene coding for MaOC1, a caspase homolog protease, is followed by a toxin-antitoxin module, flanked on each side by a direct repeat. We therefore investigated their possible interaction at the protein level. Our results suggest that this module belongs to the ParE/ParD-like superfamily of type II toxin-antitoxin systems. In solution, the antitoxin is predominantly alpha-helical and dimeric. When coexpressed with its cognate toxin and isolated from Escherichia coli, it forms a complex, as revealed by light scattering and affinity purification. The active site of the toxin is restricted to the C-terminus of the molecule. Its truncation led to normal cell growth, while the wild-type form prevented bacterial growth in liquid medium. The orthocaspase MaOC1 was able to cleave the antitoxin so that it could no longer block the toxin activity. The most likely target of the protease was the C-terminus of the antitoxin with two sections of basic amino acid residues. E. coli cells in which MaOC1 was expressed simultaneously with the toxin-antitoxin pair were unable to grow. In contrast, no effect on cell growth was found when using a proteolytically inactive MaOC1 mutant. We thus present the first case of a cysteine protease that regulates the activity of a toxin-antitoxin module, since all currently known activating proteases are of the serine type.
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Affiliation(s)
- Marina Klemenčič
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Ana Halužan Vasle
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Marko Dolinar
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
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8
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Ames JR, McGillick J, Murphy T, Reddem E, Bourne CR. Identifying a Molecular Mechanism That Imparts Species-Specific Toxicity to YoeB Toxins. Front Microbiol 2020; 11:959. [PMID: 32528435 PMCID: PMC7256200 DOI: 10.3389/fmicb.2020.00959] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 04/21/2020] [Indexed: 11/24/2022] Open
Abstract
The ribosome-dependent E. coli (Ec) mRNase toxin YoeB has been demonstrated to protect cells during thermal stress. Agrobacterium tumefaciens (At), a plant pathogen, also encodes a YoeB toxin. Initial studies indicated that AtYoeB does not impact the growth of Ec, but its expression is toxic to the native host At. The current work examines this species-specific effect. We establish the highly similar structure and function of Ec and AtYoeB toxins, including the ability of the AtYoeB toxin to inhibit Ec ribosomes in vitro. Comparison of YoeB sequences and structures highlights a four-residue helix between β-strands 2 and 3 that interacts with mRNA bases within the ribosome. This helix sequence is varied among YoeB toxins, and this variation correlates with bacterial classes of proteobacteria. When the four amino acid sequence of this helix is transplanted from EcYoeB onto AtYoeB, the resulting chimera gains toxicity to Ec cells and lessens toxicity to At cells. The reverse is also true, such that EcYoeB with the AtYoeB helix sequence is less toxic to Ec and gains toxicity to At cultures. We suggest this helix sequence directs mRNA sequence-specific degradation, which varies among proteobacterial classes, and thus controls growth inhibition and YoeB toxicity.
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Affiliation(s)
- Jessica R Ames
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, United States
| | - Julia McGillick
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, United States
| | - Tamiko Murphy
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, United States
| | - Eswar Reddem
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, United States
| | - Christina R Bourne
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, United States
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9
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Yoon WS, Seok SH, Won HS, Cho T, Lee SJ, Seo MD. Structural changes of antitoxin HigA from Shigella flexneri by binding of its cognate toxin HigB. Int J Biol Macromol 2019; 130:99-108. [PMID: 30797012 DOI: 10.1016/j.ijbiomac.2019.02.111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/19/2019] [Accepted: 02/19/2019] [Indexed: 11/17/2022]
Abstract
In toxin-antitoxin systems, many antitoxin proteins that neutralize their cognate toxin proteins also bind to DNA to repress transcription, and the DNA-binding affinity of the antitoxin is affected by its toxin. We solved crystal structures of the antitoxin HigA (apo-SfHigA) and its complex with the toxin HigB (SfHigBA) from Shigella flexneri. The apo-SfHigA shows a distinctive V-shaped homodimeric conformation with sequestered N-domains having a novel fold. SfHigBA appears as a heterotetramer formed by N-terminal dimerization of SfHigB-bound SfHigA molecules. The conformational change in SfHigA upon SfHigB binding is mediated by rigid-body movements of its C-domains, which accompanied an overall conformational change from wide V-shaped to narrow V-shaped dimer. Consequently, the two putative DNA-binding helices (α7 in each subunit) are repositioned to a conformation more compatible with canonical homodimeric DNA-binding proteins containing HTH motifs. Collectively, this study demonstrates a conformational change in an antitoxin protein, which occurs upon toxin binding and is responsible for regulating antitoxin DNA binding.
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Affiliation(s)
- Won-Su Yoon
- Department of Molecular Science and Technology, Ajou University, Suwon, Gyeonggi 16499, Republic of Korea; College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST), Ajou University, Suwon, Gyeonggi 16499, Republic of Korea
| | - Seung-Hyeon Seok
- College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST), Ajou University, Suwon, Gyeonggi 16499, Republic of Korea
| | - Hyung-Sik Won
- Department of Biotechnology, Research Institute (RIBHS) and College of Biomedical & Health Science, Konkuk University, Chungju, Chungbuk 27478, Republic of Korea
| | - Taehwan Cho
- Department of Molecular Science and Technology, Ajou University, Suwon, Gyeonggi 16499, Republic of Korea; College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST), Ajou University, Suwon, Gyeonggi 16499, Republic of Korea
| | - Sang Jae Lee
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Min-Duk Seo
- Department of Molecular Science and Technology, Ajou University, Suwon, Gyeonggi 16499, Republic of Korea; College of Pharmacy and Research Institute of Pharmaceutical Science and Technology (RIPST), Ajou University, Suwon, Gyeonggi 16499, Republic of Korea.
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10
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Roy M, Kundu A, Bhunia A, Das Gupta S, De S, Das AK. Structural characterization of VapB46 antitoxin from
Mycobacterium tuberculosis
: insights into VapB46–
DNA
binding. FEBS J 2019; 286:1174-1190. [DOI: 10.1111/febs.14737] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 10/24/2018] [Accepted: 12/17/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Madhurima Roy
- Department of Biotechnology Indian Institute of Technology Kharagpur India
| | - Anirban Kundu
- Department of Biotechnology Indian Institute of Technology Kharagpur India
| | | | | | - Soumya De
- School of Bioscience Indian Institute of Technology Kharagpur India
| | - Amit Kumar Das
- Department of Biotechnology Indian Institute of Technology Kharagpur India
- School of Bioscience Indian Institute of Technology Kharagpur India
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11
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Kang SM, Kim DH, Lee KY, Park SJ, Yoon HJ, Lee SJ, Im H, Lee BJ. Functional details of the Mycobacterium tuberculosis VapBC26 toxin-antitoxin system based on a structural study: insights into unique binding and antibiotic peptides. Nucleic Acids Res 2017; 45:8564-8580. [PMID: 28575388 PMCID: PMC5737657 DOI: 10.1093/nar/gkx489] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/25/2017] [Indexed: 11/16/2022] Open
Abstract
Toxin-antitoxin (TA) systems are essential for bacterial persistence under stressful conditions. In particular, Mycobacterium tuberculosis express VapBC TA genes that encode the stable VapC toxin and the labile VapB antitoxin. Under normal conditions, these proteins interact to form a non-toxic TA complex, but the toxin is activated by release from the antitoxin in response to unfavorable conditions. Here, we present the crystal structure of the M. tuberculosis VapBC26 complex and show that the VapC26 toxin contains a pilus retraction protein (PilT) N-terminal (PIN) domain that is essential for ribonuclease activity and that, the VapB26 antitoxin folds into a ribbon-helix-helix DNA-binding motif at the N-terminus. The active site of VapC26 is sterically blocked by the flexible C-terminal region of VapB26. The C-terminal region of free VapB26 adopts an unfolded conformation but forms a helix upon binding to VapC26. The results of RNase activity assays show that Mg2+ and Mn2+ are essential for the ribonuclease activity of VapC26. As shown in the nuclear magnetic resonance spectra, several residues of VapB26 participate in the specific binding to the promoter region of the VapBC26 operon. In addition, toxin-mimicking peptides were designed that inhibit TA complex formation and thereby increase toxin activity, providing a novel approach to the development of new antibiotics.
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Affiliation(s)
- Sung-Min Kang
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Do-Hee Kim
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Ki-Young Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Sung Jean Park
- College of Pharmacy, Gachon University, 534-2 Yeonsu-dong, Yeonsu-gu, Incheon 406-799, Republic of Korea
| | - Hye-Jin Yoon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sang Jae Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Hookang Im
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea
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12
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Ruangprasert A, Maehigashi T, Miles SJ, Dunham CM. Importance of the E. coli DinJ antitoxin carboxy terminus for toxin suppression and regulated proteolysis. Mol Microbiol 2017; 104:65-77. [PMID: 28164393 DOI: 10.1111/mmi.13641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2017] [Indexed: 11/26/2022]
Abstract
Toxin-antitoxin genes play important roles in the regulation of bacterial growth during stress. One response to stress is selective proteolysis of antitoxin proteins which releases their cognate toxin partners causing rapid inhibition of growth. The features of toxin-antitoxin complexes that are important to inhibit toxin activity as well as to release the active toxin remain elusive. Furthermore, it is unclear how antitoxins are selected for proteolysis by cellular proteases. Here, we test the minimal structural requirements of the Escherichia coli DinJ antitoxin to suppress its toxin partner, YafQ. We find that DinJ-YafQ complex formation is critically dependent on the last ten C-terminal residues of DinJ. However, deletion of these 10 DinJ residues has little effect on transcriptional autorepression suggesting that the YafQ toxin is not a critical component of the repression complex in contrast to other toxin-antitoxin systems. We further demonstrate that loop 5 preceding these ten C-terminal residues is important for Lon-mediated proteolysis. These results provide important insights into the critical interactions between toxin-antitoxin pairs necessary to inhibit toxin activity and the regulated proteolysis of antitoxins.
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Affiliation(s)
- Ajchareeya Ruangprasert
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Tatsuya Maehigashi
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Stacey J Miles
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Christine M Dunham
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
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13
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Structure, Biology, and Therapeutic Application of Toxin-Antitoxin Systems in Pathogenic Bacteria. Toxins (Basel) 2016; 8:toxins8100305. [PMID: 27782085 PMCID: PMC5086665 DOI: 10.3390/toxins8100305] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 10/17/2016] [Accepted: 10/18/2016] [Indexed: 01/09/2023] Open
Abstract
Bacterial toxin–antitoxin (TA) systems have received increasing attention for their diverse identities, structures, and functional implications in cell cycle arrest and survival against environmental stresses such as nutrient deficiency, antibiotic treatments, and immune system attacks. In this review, we describe the biological functions and the auto-regulatory mechanisms of six different types of TA systems, among which the type II TA system has been most extensively studied. The functions of type II toxins include mRNA/tRNA cleavage, gyrase/ribosome poison, and protein phosphorylation, which can be neutralized by their cognate antitoxins. We mainly explore the similar but divergent structures of type II TA proteins from 12 important pathogenic bacteria, including various aspects of protein–protein interactions. Accumulating knowledge about the structure–function correlation of TA systems from pathogenic bacteria has facilitated a novel strategy to develop antibiotic drugs that target specific pathogens. These molecules could increase the intrinsic activity of the toxin by artificially interfering with the intermolecular network of the TA systems.
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14
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Chan WT, Espinosa M, Yeo CC. Keeping the Wolves at Bay: Antitoxins of Prokaryotic Type II Toxin-Antitoxin Systems. Front Mol Biosci 2016; 3:9. [PMID: 27047942 PMCID: PMC4803016 DOI: 10.3389/fmolb.2016.00009] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 03/04/2016] [Indexed: 12/21/2022] Open
Abstract
In their initial stages of discovery, prokaryotic toxin-antitoxin (TA) systems were confined to bacterial plasmids where they function to mediate the maintenance and stability of usually low- to medium-copy number plasmids through the post-segregational killing of any plasmid-free daughter cells that developed. Their eventual discovery as nearly ubiquitous and repetitive elements in bacterial chromosomes led to a wealth of knowledge and scientific debate as to their diversity and functionality in the prokaryotic lifestyle. Currently categorized into six different types designated types I–VI, type II TA systems are the best characterized. These generally comprised of two genes encoding a proteic toxin and its corresponding proteic antitoxin, respectively. Under normal growth conditions, the stable toxin is prevented from exerting its lethal effect through tight binding with the less stable antitoxin partner, forming a non-lethal TA protein complex. Besides binding with its cognate toxin, the antitoxin also plays a role in regulating the expression of the type II TA operon by binding to the operator site, thereby repressing transcription from the TA promoter. In most cases, full repression is observed in the presence of the TA complex as binding of the toxin enhances the DNA binding capability of the antitoxin. TA systems have been implicated in a gamut of prokaryotic cellular functions such as being mediators of programmed cell death as well as persistence or dormancy, biofilm formation, as defensive weapons against bacteriophage infections and as virulence factors in pathogenic bacteria. It is thus apparent that these antitoxins, as DNA-binding proteins, play an essential role in modulating the prokaryotic lifestyle whilst at the same time preventing the lethal action of the toxins under normal growth conditions, i.e., keeping the proverbial wolves at bay. In this review, we will cover the diversity and characteristics of various type II TA antitoxins. We shall also look into some interesting deviations from the canonical type II TA systems such as tripartite TA systems where the regulatory role is played by a third party protein and not the antitoxin, and a unique TA system encoding a single protein with both toxin as well as antitoxin domains.
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Affiliation(s)
- Wai Ting Chan
- Molecular Microbiology and Infection Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas Madrid, Spain
| | - Manuel Espinosa
- Molecular Microbiology and Infection Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas Madrid, Spain
| | - Chew Chieng Yeo
- Faculty of Medicine, Biomedical Research Centre, Universiti Sultan Zainal Abidin Kuala Terengganu, Malaysia
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15
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Identification and characterization of the chromosomal yefM-yoeB toxin-antitoxin system of Streptococcus suis. Sci Rep 2015; 5:13125. [PMID: 26272287 PMCID: PMC4536659 DOI: 10.1038/srep13125] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/20/2015] [Indexed: 01/06/2023] Open
Abstract
Toxin-antitoxin (TA) systems are widely prevalent in the genomes of bacteria and archaea. These modules have been identified in Escherichia coli and various other bacteria. However, their presence in the genome of Streptococcus suis, an important zoonotic pathogen, has received little attention. In this study, we describe the identification and characterization of a type II TA system, comprising the chromosomal yefM-yoeB locus of S. suis. The yefM-yoeB locus is present in the genome of most serotypes of S. suis. Overproduction of S. suis YoeB toxin inhibited the growth of E. coli, and the toxicity of S. suis YoeB could be alleviated by the antitoxin YefM from S. suis and Streptococcus pneumoniae, but not by E. coli YefM. More importantly, introduction of the S. suis yefM-yoeB system into E. coli could affect cell growth. In a murine infection model, deletion of the yefM-yoeB locus had no effect on the virulence of S. suis serotype 2. Collectively, our data suggested that the yefM-yoeB locus of S. suis is an active TA system without the involvement of virulence.
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Janssen BD, Garza-Sánchez F, Hayes CS. YoeB toxin is activated during thermal stress. Microbiologyopen 2015; 4:682-97. [PMID: 26147890 PMCID: PMC4554461 DOI: 10.1002/mbo3.272] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 05/27/2015] [Indexed: 11/07/2022] Open
Abstract
Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis. In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock. We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways.
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Affiliation(s)
- Brian D Janssen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California
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Chan WT, Balsa D, Espinosa M. One cannot rule them all: Are bacterial toxins-antitoxins druggable? FEMS Microbiol Rev 2015; 39:522-40. [PMID: 25796610 PMCID: PMC4487406 DOI: 10.1093/femsre/fuv002] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2015] [Indexed: 01/31/2023] Open
Abstract
Type II (proteic) toxin–antitoxin (TA) operons are widely spread in bacteria and archaea. They are organized as operons in which, usually, the antitoxin gene precedes the cognate toxin gene. The antitoxin generally acts as a transcriptional self-repressor, whereas the toxin acts as a co-repressor, both proteins constituting a harmless complex. When bacteria encounter a stressful environment, TAs are triggered. The antitoxin protein is unstable and will be degraded by host proteases, releasing the free toxin to halt essential processes. The result is a cessation of cell growth or even death. Because of their ubiquity and the essential processes targeted, TAs have been proposed as good candidates for development of novel antimicrobials. We discuss here the possible druggability of TAs as antivirals and antibacterials, with focus on the potentials and the challenges that their use may find in the ‘real’ world. We present strategies to develop TAs as antibacterials in view of novel technologies, such as the use of very small molecules (fragments) as inhibitors of protein–protein interactions. Appropriate fragments could disrupt the T:A interfaces leading to the release of the targeted TA pair. Possible ways of delivery and formulation of Tas are also discussed. We consider various approaches to develop the toxins of the type II family as possible candidates to drug discovery; druggability of toxins-antitoxins could be possible as antivirals. As antibacterials, they might be considered as druggable but delivery and formulation may not be simple so far.
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Affiliation(s)
- Wai Ting Chan
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28006-Madrid, Spain
| | - Dolors Balsa
- Immunology & Vaccines, Laboratorios LETI, Gran Via de les Corts Catalanes 184. 08034-Barcelona, Spain
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28006-Madrid, Spain
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18
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Dy RL, Richter C, Salmond GP, Fineran PC. Remarkable Mechanisms in Microbes to Resist Phage Infections. Annu Rev Virol 2014; 1:307-31. [DOI: 10.1146/annurev-virology-031413-085500] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ron L. Dy
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand;
| | - Corinna Richter
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand;
| | - George P.C. Salmond
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - Peter C. Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand;
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Loris R, Garcia-Pino A. Disorder- and Dynamics-Based Regulatory Mechanisms in Toxin–Antitoxin Modules. Chem Rev 2014; 114:6933-47. [DOI: 10.1021/cr400656f] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Remy Loris
- Molecular
Recognition Unit, Structural Biology Research Center, VIB, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural
Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Abel Garcia-Pino
- Molecular
Recognition Unit, Structural Biology Research Center, VIB, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural
Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
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20
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Multiple toxin-antitoxin systems in Mycobacterium tuberculosis. Toxins (Basel) 2014; 6:1002-20. [PMID: 24662523 PMCID: PMC3968373 DOI: 10.3390/toxins6031002] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/20/2014] [Accepted: 02/24/2014] [Indexed: 12/26/2022] Open
Abstract
The hallmark of Mycobacterium tuberculosis is its ability to persist for a long-term in host granulomas, in a non-replicating and drug-tolerant state, and later awaken to cause disease. To date, the cellular factors and the molecular mechanisms that mediate entry into the persistence phase are poorly understood. Remarkably, M. tuberculosis possesses a very high number of toxin-antitoxin (TA) systems in its chromosome, 79 in total, regrouping both well-known (68) and novel (11) families, with some of them being strongly induced in drug-tolerant persisters. In agreement with the capacity of stress-responsive TA systems to generate persisters in other bacteria, it has been proposed that activation of TA systems in M. tuberculosis could contribute to its pathogenesis. Herein, we review the current knowledge on the multiple TA families present in this bacterium, their mechanism, and their potential role in physiology and virulence.
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Połom D, Boss L, Węgrzyn G, Hayes F, Kędzierska B. Amino acid residues crucial for specificity of toxin-antitoxin interactions in the homologous Axe-Txe and YefM-YoeB complexes. FEBS J 2013; 280:5906-18. [PMID: 24028219 DOI: 10.1111/febs.12517] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/30/2013] [Accepted: 09/02/2013] [Indexed: 11/29/2022]
Abstract
Toxin-antitoxin complexes are ubiquitous in bacteria. The specificity of interactions between toxins and antitoxins from homologous but non-interacting systems was investigated. Based on molecular modeling, selected amino acid residues were changed to assess which positions were crucial in the specificity of toxin-antitoxin interaction in the related Axe-Txe and YefM-YoeB complexes. No cross-interactions between wild-type proteins were detected. However, a single amino acid substitution that converts a Txe-specific residue to a YoeB-specific residue reduced, but did not abolish, Txe interaction with the Axe antitoxin. Interestingly, this alteration (Txe-Asp83Tyr) promoted functional interactions between Txe and the YefM antitoxin. The interactions between Txe-Asp83Tyr and YefM were sufficiently strong to abolish Txe toxicity and to allow effective corepression by YefM-Txe-Asp83Tyr of the promoter from which yefM-yoeB is expressed. We conclude that Asp83 in Txe is crucial for the specificity of toxin-antitoxin interactions in the Axe-Txe complex and that swapping this residue for the equivalent residue in YoeB relaxes the specificity of the toxin-antitoxin interaction.
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Affiliation(s)
- Dorota Połom
- Department of Molecular Biology, University of Gdańsk, Poland
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22
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Regulation of toxin–antitoxin systems by proteolysis. Plasmid 2013; 70:33-41. [DOI: 10.1016/j.plasmid.2013.01.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 11/19/2022]
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23
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Miallau L, Jain P, Arbing MA, Cascio D, Phan T, Ahn CJ, Chan S, Chernishof I, Maxson M, Chiang J, Jacobs WR, Eisenberg DS. Comparative proteomics identifies the cell-associated lethality of M. tuberculosis RelBE-like toxin-antitoxin complexes. Structure 2013; 21:627-37. [PMID: 23523424 DOI: 10.1016/j.str.2013.02.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 02/08/2013] [Accepted: 02/11/2013] [Indexed: 01/06/2023]
Abstract
The Mycobacterium tuberculosis (Mtb) genome encodes approximately 90 toxin-antitoxin protein complexes, including three RelBE family members, which are believed to play a major role in bacterial fitness and pathogenicity. We have determined the crystal structures of Mtb RelBE-2 and RelBE-3, and the structures reveal homologous heterotetramers. Our structures suggest RelE-2, and by extension the closely related RelE-1, use a different catalytic mechanism than RelE-3, because our analysis of the RelE-2 structure predicts additional amino acid residues that are likely to be functionally significant and are missing from analogous positions in the RelE-3 structure. Toxicity assays corroborate our structural findings; overexpression of RelE-3, whose active site is more similar to Escherichia coli YoeB, has limited consequences on bacterial growth, whereas RelE-1 and RelE-2 overexpression results in acute toxicity. Moreover, RelE-2 overexpression results in an elongated cell phenotype in Mycobacterium smegmatis and protects M. tuberculosis against antibiotics, suggesting a different functional role for RelE-2.
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Affiliation(s)
- Linda Miallau
- Howard Hughes Medical Institute and UCLA-DOE Institute for Genomics and Proteomics and Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA
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24
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Min AB, Miallau L, Sawaya MR, Habel J, Cascio D, Eisenberg D. The crystal structure of the Rv0301-Rv0300 VapBC-3 toxin-antitoxin complex from M. tuberculosis reveals a Mg²⁺ ion in the active site and a putative RNA-binding site. Protein Sci 2013; 21:1754-67. [PMID: 23011806 DOI: 10.1002/pro.2161] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
VapBC pairs account for 45 out of 88 identified toxin-antitoxin (TA) pairs in the Mycobacterium tuberculosis (Mtb) H37Rv genome. A working model suggests that under times of stress, antitoxin molecules are degraded, releasing the toxins to slow the metabolism of the cell, which in the case of VapC toxins is via their RNase activity. Otherwise the TA pairs remain bound to their promoters, autoinhibiting transcription. The crystal structure of Rv0301-Rv0300, an Mtb VapBC TA complex determined at 1.49 Å resolution, suggests a mechanism for these three functions: RNase activity, its inhibition by antitoxin, and its ability to bind promoter DNA. The Rv0301 toxin consists of a core of five parallel beta strands flanked by alpha helices. Three proximal aspartates coordinate a Mg²⁺ ion forming the putative RNase active site. The Rv0300 antitoxin monomer is extended in structure, consisting of an N-terminal beta strand followed by four helices. The last two helices wrap around the toxin and terminate near the putative RNase active site, but with different conformations. In one conformation, the C-terminal arginine interferes with Mg²⁺ ion coordination, suggesting a mechanism by which the antitoxin can inhibit toxin activity. At the N-terminus of the antitoxin, two pairs of Ribbon-Helix-Helix (RHH) motifs are related by crystallographic twofold symmetry. The resulting hetero-octameric complex is similar to the FitAB system, but the two RHH motifs are about 30 Å closer together in the Rv0301-Rv0300 complex, suggesting either a different span of the DNA recognition sequence or a conformational change.
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Affiliation(s)
- Andrew B Min
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, UCLA-DOE Institute of Genomics and Proteomics, UCLA, Los Angeles, California 90095-1570, USA
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25
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Park SJ, Son WS, Lee BJ. Structural overview of toxin-antitoxin systems in infectious bacteria: a target for developing antimicrobial agents. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1155-67. [PMID: 23459128 DOI: 10.1016/j.bbapap.2013.02.027] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 02/18/2013] [Accepted: 02/20/2013] [Indexed: 11/17/2022]
Abstract
The bacterial toxin-antitoxin (TA) system is a module that may play a role in cell survival under stress conditions. Generally, toxin molecules act as negative regulators in cell survival and antitoxin molecules as positive regulators. Thus, the expression levels and interactions between toxins and antitoxins should be systematically harmonized so that bacteria can escape such harmful conditions. Since TA systems are able to control the fate of bacteria, they are considered potent targets for the development of new antimicrobial agents. TA systems are widely prevalent with a variety of systems existing in bacteria: there are three types of bacterial TA systems depending on the property of the antitoxin which binds either the protein toxin or mRNA coding the toxin protein. Moreover, the multiplicity of TA genes has been observed even in species of bacteria. Therefore, knowledge on TA systems such as the individual characteristics of TA systems, integrative working mechanisms of various TA systems in bacteria, interactions between toxin molecules and cellular targets, and so on is currently limited due to their complexity. In this regard, it would be helpful to know the structural characteristics of TA modules for understanding TA systems in bacteria. Until now, 85 out of the total structures deposited in PDB have been bacterial TA system proteins including TA complexes or isolated toxins/antitoxins. Here, we summarized the structural information of TA systems and analyzed the structural characteristics of known TA modules from several bacteria, especially focusing on the TA modules of several infectious bacteria.
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Affiliation(s)
- Sung Jean Park
- College of Pharmacy, Gachon University, Yeonsu-gu, Incheon, Republic of Korea
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26
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Solution structure and biophysical properties of MqsA, a Zn-containing antitoxin from Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1401-8. [DOI: 10.1016/j.bbapap.2012.06.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 06/28/2012] [Accepted: 06/29/2012] [Indexed: 11/23/2022]
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27
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WANG W, DING JJ, WANG DC. Three Dimensional Structure of <I>Pseudomonas aeruginosa</I> Tsi2: a Novel Species-specific Antitoxin-like Protein With Coiled Coil Conformation*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2012.00126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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28
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Zhang H, Gao ZQ, Su XD, Dong YH. Crystal structure of type VI effector Tse1 from Pseudomonas aeruginosa. FEBS Lett 2012; 586:3193-9. [DOI: 10.1016/j.febslet.2012.06.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 05/30/2012] [Accepted: 06/20/2012] [Indexed: 11/27/2022]
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Moreno-Córdoba I, Diago-Navarro E, Barendregt A, Heck AJR, Alfonso C, Díaz-Orejas R, Nieto C, Espinosa M. The toxin-antitoxin proteins relBE2Spn of Streptococcus pneumoniae: characterization and association to their DNA target. Proteins 2012; 80:1834-46. [PMID: 22488579 DOI: 10.1002/prot.24081] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 03/21/2012] [Accepted: 03/23/2012] [Indexed: 01/07/2023]
Abstract
The chromosome of the pathogenic Gram-positive bacterium Streptococcus pneumoniae contains between six to 10 operons encoding toxin-antitoxin systems (TAS). TAS are widespread and redundant in bacteria and archaea and their role, albeit still obscure, may be related to important aspects of bacteria lifestyle like response to stress. One of the most abundant TAS is the relBE family, being present in the chromosome of many bacteria and archaea. Because of the high rates of morbility and mortality caused by S. pneumoniae, it has been interesting to gain knowledge on the pneumococcal TAS, among them the RelBE2Spn proteins. Here, we have analyzed the DNA binding capacity of the RelB2Spn antitoxin and the RelB2Spn-RelE2Spn proteins by band-shift assays. Thus, a DNA region encompassing the operator region of the proteins was identified. In addition, we have used analytical ultracentrifugation and native mass spectrometry to measure the oligomerization state of the antitoxin alone and the RelBE2Spn complex in solution bound or unbound to its DNA substrate. Using native mass spectrometry allowed us to unambiguously determine the stoichiometry of the RelB2Spn and of the RelBE2Spn complex alone or associated to its DNA target.
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Affiliation(s)
- Inma Moreno-Córdoba
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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30
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Abstract
Almost all bacteria and many archaea contain genes whose expression inhibits cell growth and may lead to cell death when overproduced, reminiscent of apoptotic genes in higher systems. The cellular targets of these toxins are quite diverse and include DNA replication, mRNA stability, protein synthesis, cell-wall biosynthesis, and ATP synthesis. These toxins are co-expressed and neutralized with their cognate antitoxins from a TA (toxin-antitoxin) operon in normally growing cells. Antitoxins are more labile than toxins and are readily degraded under stress conditions, allowing the toxins to exert their toxic effect. Presence of at least 33 TA systems in Escherichia coli and more than 60 TA systems in Mycobacterium tuberculosis suggests that the TA systems are involved not only in normal bacterial physiology but also in pathogenicity of bacteria. The elucidation of their cellular function and regulation is thus crucial for our understanding of bacterial physiology under various stress conditions.
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Affiliation(s)
- Yoshihiro Yamaguchi
- Department of Biochemistry, Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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31
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Zou T, Yao X, Qin B, Zhang M, Cai L, Shang W, Svergun DI, Wang M, Cui S, Jin Q. Crystal structure of Pseudomonas aeruginosa Tsi2 reveals a stably folded superhelical antitoxin. J Mol Biol 2012; 417:351-61. [PMID: 22310046 DOI: 10.1016/j.jmb.2012.01.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 01/14/2012] [Accepted: 01/25/2012] [Indexed: 11/25/2022]
Abstract
In the competition for niches in natural resources, Pseudomonas aeruginosa utilizes the type VI secretion system to inject the toxic protein effector Tse2 into bacteria on cell-cell contact. The cytoplasm toxin immunity protein Tsi2 can neutralize Tse2 by physical interaction with the toxin, providing essential protection from toxin activity. Except for orthologues in P. aeruginosa, Tsi2 antitoxin does not share detectable sequence homology with known proteins in public databases. The mechanism underlying toxin neutralization by Tsi2 remains unknown. We report here the crystal structure of Tsi2 at 2.28 Å resolution. Our structural and biophysical analyses demonstrate that the antitoxin adopts a previously unobserved superhelical conformation. Tsi2 is highly thermostable in the absence of the toxin in solution. Tsi2 assembles a dimer with 2-fold rotational symmetry, similar to that observed in other toxin-antitoxin systems. Dimerization is essential for the stable folding of Tsi2.
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Affiliation(s)
- Tingting Zou
- Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 9 Dong Dan San Tiao, Beijing 100730, PR China
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Arora A, Chandra NR, Das A, Gopal B, Mande SC, Prakash B, Ramachandran R, Sankaranarayanan R, Sekar K, Suguna K, Tyagi AK, Vijayan M. Structural biology of Mycobacterium tuberculosis proteins: The Indian efforts. Tuberculosis (Edinb) 2011; 91:456-68. [DOI: 10.1016/j.tube.2011.03.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 03/15/2011] [Accepted: 03/16/2011] [Indexed: 01/23/2023]
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33
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Hayes F, Van Melderen L. Toxins-antitoxins: diversity, evolution and function. Crit Rev Biochem Mol Biol 2011; 46:386-408. [PMID: 21819231 DOI: 10.3109/10409238.2011.600437] [Citation(s) in RCA: 196] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Genes for toxin-antitoxin (TA) complexes are widespread in prokaryote genomes, and species frequently possess tens of plasmid and chromosomal TA loci. The complexes are categorized into three types based on genetic organization and mode of action. The toxins universally are proteins directed against specific intracellular targets, whereas the antitoxins are either proteins or small RNAs that neutralize the toxin or inhibit toxin synthesis. Within the three types of complex, there has been extensive evolutionary shuffling of toxin and antitoxin genes leading to considerable diversity in TA combinations. The intracellular targets of the protein toxins similarly are varied. Numerous toxins, many of which are sequence-specific endoribonucleases, dampen protein synthesis levels in response to a range of stress and nutritional stimuli. Key resources are conserved as a result ensuring the survival of individual cells and therefore the bacterial population. The toxin effects generally are transient and reversible permitting a set of dynamic, tunable responses that reflect environmental conditions. Moreover, by harboring multiple toxins that intercede in protein synthesis in response to different physiological cues, bacteria potentially sense an assortment of metabolic perturbations that are channeled through different TA complexes. Other toxins interfere with the action of topoisomersases, cell wall assembly, or cytoskeletal structures. TAs also play important roles in bacterial persistence, biofilm formation and multidrug tolerance, and have considerable potential both as new components of the genetic toolbox and as targets for novel antibacterial drugs.
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Affiliation(s)
- Finbarr Hayes
- Faculty of Life Sciences and Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester, UK.
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VapC toxins from Mycobacterium tuberculosis are ribonucleases that differentially inhibit growth and are neutralized by cognate VapB antitoxins. PLoS One 2011; 6:e21738. [PMID: 21738782 PMCID: PMC3126847 DOI: 10.1371/journal.pone.0021738] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 06/09/2011] [Indexed: 12/18/2022] Open
Abstract
The chromosome of Mycobacterium tuberculosis (Mtb) encodes forty seven toxin-antitoxin modules belonging to the VapBC family. The role of these modules in the physiology of Mtb and the function(s) served by their expansion are unknown. We investigated ten vapBC modules from Mtb and the single vapBC from M. smegmatis. Of the Mtb vapCs assessed, only Rv0549c, Rv0595c, Rv2549c and Rv2829c were toxic when expressed from a tetracycline-regulated promoter in M. smegmatis. The same genes displayed toxicity when conditionally expressed in Mtb. Toxicity of Rv2549c in M. smegmatis correlated with the level of protein expressed, suggesting that the VapC level must exceed a threshold for toxicity to be observed. In addition, the level of Rv2456 protein induced in M. smegmatis was markedly lower than Rv2549c, which may account for the lack of toxicity of this and other VapCs scored as ‘non-toxic’. The growth inhibitory effects of toxic VapCs were neutralized by expression of the cognate VapB as part of a vapBC operon or from a different chromosomal locus, while that of non-cognate antitoxins did not. These results demonstrated a specificity of interaction between VapCs and their cognate VapBs, a finding corroborated by yeast two-hybrid analyses. Deletion of selected vapC or vapBC genes did not affect mycobacterial growth in vitro, but rendered the organisms more susceptible to growth inhibition following toxic VapC expression. However, toxicity of ‘non-toxic’ VapCs was not unveiled in deletion mutant strains, even when the mutation eliminated the corresponding cognate VapB, presumably due to insufficient levels of VapC protein. Together with the ribonuclease (RNase) activity demonstrated for Rv0065 and Rv0617 – VapC proteins with similarity to Rv0549c and Rv3320c, respectively – these results suggest that the VapBC family potentially provides an abundant source of RNase activity in Mtb, which may profoundly impact the physiology of the organism.
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Blower TR, Salmond GPC, Luisi BF. Balancing at survival's edge: the structure and adaptive benefits of prokaryotic toxin–antitoxin partners. Curr Opin Struct Biol 2011; 21:109-18. [DOI: 10.1016/j.sbi.2010.10.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 10/31/2010] [Indexed: 01/21/2023]
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Arbing MA, Handelman SK, Kuzin AP, Verdon G, Wang C, Su M, Rothenbacher FP, Abashidze M, Liu M, Hurley JM, Xiao R, Acton T, Inouye M, Montelione GT, Woychik NA, Hunt JF. Crystal structures of Phd-Doc, HigA, and YeeU establish multiple evolutionary links between microbial growth-regulating toxin-antitoxin systems. Structure 2010; 18:996-1010. [PMID: 20696400 DOI: 10.1016/j.str.2010.04.018] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Revised: 03/22/2010] [Accepted: 04/21/2010] [Indexed: 10/19/2022]
Abstract
Bacterial toxin-antitoxin (TA) systems serve a variety of physiological functions including regulation of cell growth and maintenance of foreign genetic elements. Sequence analyses suggest that TA families are linked by complex evolutionary relationships reflecting likely swapping of functional domains between different TA families. Our crystal structures of Phd-Doc from bacteriophage P1, the HigA antitoxin from Escherichia coli CFT073, and YeeU of the YeeUWV systems from E. coli K12 and Shigella flexneri confirm this inference and reveal additional, unanticipated structural relationships. The growth-regulating Doc toxin exhibits structural similarity to secreted virulence factors that are toxic for eukaryotic target cells. The Phd antitoxin possesses the same fold as both the YefM and NE2111 antitoxins that inhibit structurally unrelated toxins. YeeU, which has an antitoxin-like activity that represses toxin expression, is structurally similar to the ribosome-interacting toxins YoeB and RelE. These observations suggest extensive functional exchanges have occurred between TA systems during bacterial evolution.
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Affiliation(s)
- Mark A Arbing
- Department of Biological Sciences, Columbia University, 702 Fairchild Center, MC2434, New York, NY 10027, USA
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Brown BL, Wood TK, Peti W, Page R. Structure of the Escherichia coli antitoxin MqsA (YgiT/b3021) bound to its gene promoter reveals extensive domain rearrangements and the specificity of transcriptional regulation. J Biol Chem 2010; 286:2285-96. [PMID: 21068382 DOI: 10.1074/jbc.m110.172643] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial cultures, especially biofilms, produce a small number of persister cells, a genetically identical subpopulation of wild type cells that are metabolically dormant, exhibit multidrug tolerance, and are highly enriched in bacterial toxins. The gene most highly up-regulated in Escherichia coli persisters is mqsR, a ribonuclease toxin that, along with mqsA, forms a novel toxin·antitoxin (TA) system. Like all known TA systems, both the MqsR·MqsA complex and MqsA alone regulate their own transcription. Despite the importance of TA systems in persistence and biofilms, very little is known about how TA modules, and antitoxins in particular, bind and recognize DNA at a molecular level. Here, we report the crystal structure of MqsA bound to a 26-bp fragment from the mqsRA promoter. We show that MqsA binds DNA predominantly via its C-terminal helix-turn-helix domain, with direct binding of recognition helix residues Asn(97) and Arg(101) to the DNA major groove. Unexpectedly, the structure also revealed that the MqsA N-terminal domain interacts with the DNA phosphate backbone. This results in a more than 105° rotation of the N-terminal domains between the free and complexed states, an unprecedented rearrangement for an antitoxin. The structure also shows that MqsA bends the DNA by more than 55° in order to achieve symmetrical binding. Finally, using a combination of biochemical and NMR studies, we show that the DNA sequence specificity of MqsA is mediated by direct readout.
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Affiliation(s)
- Breann L Brown
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island 02912, USA
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38
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Brown BL, Page R. Preliminary crystallographic analysis of the Escherichia coli antitoxin MqsA (YgiT/b3021) in complex with mqsRA promoter DNA. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:1060-3. [PMID: 20823526 PMCID: PMC2935227 DOI: 10.1107/s1744309110028617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 07/18/2010] [Indexed: 11/10/2022]
Abstract
The Escherichia coli proteins MqsR and MqsA comprise a novel toxin-antitoxin (TA) system. MqsA, the antitoxin, defines a new family of antitoxins because unlike other antitoxins MqsA is structured throughout its entire sequence, binds zinc and coordinates DNA via its C-terminal and not its N-terminal domain. In order to understand how bacterial antitoxins, and MqsA in particular, regulate transcription, the MqsA protein was cocrystallized with a 26-mer duplex DNA corresponding to the palindromic region of the mqsRA promoter. The merohedrally twinned crystal belonged to space group P4(1), with unit-cell parameters a=60.99, b=60.99, c=148.60 A. A complete data set was collected to a resolution of 2.1 A. The solvent content of the crystal was consistent with the presence of two MqsA molecules bound to the duplex DNA in the asymmetric unit.
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Affiliation(s)
- Breann L. Brown
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Box G-E3, Providence, RI 02912, USA
| | - Rebecca Page
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Box G-E4, Providence, RI 02912, USA
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39
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Allostery and intrinsic disorder mediate transcription regulation by conditional cooperativity. Cell 2010; 142:101-11. [PMID: 20603017 DOI: 10.1016/j.cell.2010.05.039] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 01/05/2010] [Accepted: 05/20/2010] [Indexed: 11/20/2022]
Abstract
Regulation of the phd/doc toxin-antitoxin operon involves the toxin Doc as co- or derepressor depending on the ratio between Phd and Doc, a phenomenon known as conditional cooperativity. The mechanism underlying this observed behavior is not understood. Here we show that monomeric Doc engages two Phd dimers on two unrelated binding sites. The binding of Doc to the intrinsically disordered C-terminal domain of Phd structures its N-terminal DNA-binding domain, illustrating allosteric coupling between highly disordered and highly unstable domains. This allosteric effect also couples Doc neutralization to the conditional regulation of transcription. In this way, higher levels of Doc tighten repression up to a point where the accumulation of toxin triggers the production of Phd to counteract its action. Our experiments provide the basis for understanding the mechanism of conditional cooperative regulation of transcription typical of toxin-antitoxin modules. This model may be applicable for the regulation of other biological systems.
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Diago-Navarro E, Hernandez-Arriaga AM, López-Villarejo J, Muñoz-Gómez AJ, Kamphuis MB, Boelens R, Lemonnier M, Díaz-Orejas R. parD toxin-antitoxin system of plasmid R1 - basic contributions, biotechnological applications and relationships with closely-related toxin-antitoxin systems. FEBS J 2010; 277:3097-117. [DOI: 10.1111/j.1742-4658.2010.07722.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Dalton KM, Crosson S. A conserved mode of protein recognition and binding in a ParD-ParE toxin-antitoxin complex. Biochemistry 2010; 49:2205-15. [PMID: 20143871 DOI: 10.1021/bi902133s] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Toxin-antitoxin (TA) systems form a ubiquitous class of prokaryotic proteins with functional roles in plasmid inheritance, environmental stress response, and cell development. ParDE family TA systems are broadly conserved on plasmids and bacterial chromosomes and have been well characterized as genetic elements that promote stable plasmid inheritance. We present a crystal structure of a chromosomally encoded ParD-ParE complex from Caulobacter crescentus at 2.6 A resolution. This TA system forms an alpha(2)beta(2) heterotetramer in the crystal and in solution. The toxin-antitoxin binding interface reveals extensive polar and hydrophobic contacts of ParD antitoxin helices with a conserved recognition and binding groove on the ParE toxin. A cross-species comparison of this complex structure with related toxin structures identified an antitoxin recognition and binding subdomain that is conserved between distantly related members of the RelE/ParE toxin superfamily despite a low level of overall primary sequence identity. We further demonstrate that ParD antitoxin is dimeric, stably folded, and largely helical when not bound to ParE toxin. Thus, the paradigmatic model in which antitoxin undergoes a disorder-to-order transition upon toxin binding does not apply to this chromosomal ParD-ParE TA system.
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Affiliation(s)
- Kevin M Dalton
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA
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Garcia-Pino A, Sterckx Y, Vandenbussche G, Loris R. Purification and crystallization of Phd, the antitoxin of the phd/doc operon. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:167-71. [PMID: 20124714 PMCID: PMC2815684 DOI: 10.1107/s1744309109051550] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 11/30/2009] [Indexed: 11/11/2022]
Abstract
The antitoxin Phd from the phd/doc module of bacteriophage P1 was crystallized in two distinct crystal forms. Crystals of His-tagged Phd contain a C-terminally truncated version of the protein and diffract to 2.20 A resolution. Crystals of untagged Phd purified from the Phd-Doc complex diffract to 2.25 A resolution. These crystals are partially merohedrally twinned and contain the full-length version of the protein.
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Affiliation(s)
- Abel Garcia-Pino
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
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Brown BL, Grigoriu S, Kim Y, Arruda JM, Davenport A, Wood TK, Peti W, Page R. Three dimensional structure of the MqsR:MqsA complex: a novel TA pair comprised of a toxin homologous to RelE and an antitoxin with unique properties. PLoS Pathog 2009; 5:e1000706. [PMID: 20041169 PMCID: PMC2791442 DOI: 10.1371/journal.ppat.1000706] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 11/24/2009] [Indexed: 11/19/2022] Open
Abstract
One mechanism by which bacteria survive environmental stress is through the formation of bacterial persisters, a sub-population of genetically identical quiescent cells that exhibit multidrug tolerance and are highly enriched in bacterial toxins. Recently, the Escherichia coli gene mqsR (b3022) was identified as the gene most highly upregulated in persisters. Here, we report multiple individual and complex three-dimensional structures of MqsR and its antitoxin MqsA (B3021), which reveal that MqsR:MqsA form a novel toxin:antitoxin (TA) pair. MqsR adopts an α/β fold that is homologous with the RelE/YoeB family of bacterial ribonuclease toxins. MqsA is an elongated dimer that neutralizes MqsR toxicity. As expected for a TA pair, MqsA binds its own promoter. Unexpectedly, it also binds the promoters of genes important for E. coli physiology (e.g., mcbR, spy). Unlike canonical antitoxins, MqsA is also structured throughout its entire sequence, binds zinc and coordinates DNA via its C- and not N-terminal domain. These studies reveal that TA systems, especially the antitoxins, are significantly more diverse than previously recognized and provide new insights into the role of toxins in maintaining the persister state. Most bacteria live in biofilms, microbial communities that cause more than 80% of human infections. Biofilms have a genetically identical sub-population of dormant cells, named persister cells, which are the well-recognized source of antibiotic resistance. Recently, it was demonstrated that toxins are highly upregulated in persisters and have therefore been postulated to play a role in the persister state. Using an inter-disciplinary approach, we reveal how mqsR, the gene most highly upregulated in persisters, together with mqsA, function: they are the founding members of a new family of toxin:antitoxin (TA) systems. Unexpectedly, the structure of MqsR reveals that it is a ribonuclease, a protein that controls the production of other essential proteins. Moreover, we identified multiple features of this TA system that are so unique that each is a starting point for drug development. Unlike other antitoxins, MqsA is structured throughout its entire sequence, its structure is unchanged between the free and toxin-bound states and it binds zinc. It also binds DNA via its C- and not N-terminal domain. Finally, MqsA binds both its own promoter and additional genes important for E. coli physiology. Taken together, our data provide fundamental new insights into the role of MqsR and MqsA in bacterial persistence and biofilms.
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Affiliation(s)
- Breann L. Brown
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | - Simina Grigoriu
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Younghoon Kim
- Artie McFerrin Department of Chemical Engineering, Texas A & M University, College Station, Texas, United States of America
| | - Jennifer M. Arruda
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Andrew Davenport
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | - Thomas K. Wood
- Artie McFerrin Department of Chemical Engineering, Texas A & M University, College Station, Texas, United States of America
- Department of Biology, Texas A & M University, College Station, Texas, United States of America
- Zachry Department of Civil Engineering, Texas A & M University, College Station, Texas, United States of America
| | - Wolfgang Peti
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States of America
| | - Rebecca Page
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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