1
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Chan WT, Garcillán-Barcia MP, Yeo CC, Espinosa M. Type II bacterial toxin-antitoxins: hypotheses, facts, and the newfound plethora of the PezAT system. FEMS Microbiol Rev 2023; 47:fuad052. [PMID: 37715317 PMCID: PMC10532202 DOI: 10.1093/femsre/fuad052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/24/2023] [Accepted: 09/07/2023] [Indexed: 09/17/2023] Open
Abstract
Toxin-antitoxin (TA) systems are entities found in the prokaryotic genomes, with eight reported types. Type II, the best characterized, is comprised of two genes organized as an operon. Whereas toxins impair growth, the cognate antitoxin neutralizes its activity. TAs appeared to be involved in plasmid maintenance, persistence, virulence, and defence against bacteriophages. Most Type II toxins target the bacterial translational machinery. They seem to be antecessors of Higher Eukaryotes and Prokaryotes Nucleotide-binding (HEPN) RNases, minimal nucleotidyltransferase domains, or CRISPR-Cas systems. A total of four TAs encoded by Streptococcus pneumoniae, RelBE, YefMYoeB, Phd-Doc, and HicAB, belong to HEPN-RNases. The fifth is represented by PezAT/Epsilon-Zeta. PezT/Zeta toxins phosphorylate the peptidoglycan precursors, thereby blocking cell wall synthesis. We explore the body of knowledge (facts) and hypotheses procured for Type II TAs and analyse the data accumulated on the PezAT family. Bioinformatics analyses showed that homologues of PezT/Zeta toxin are abundantly distributed among 14 bacterial phyla mostly in Proteobacteria (48%), Firmicutes (27%), and Actinobacteria (18%), showing the widespread distribution of this TA. The pezAT locus was found to be mainly chromosomally encoded whereas its homologue, the tripartite omega-epsilon-zeta locus, was found mostly on plasmids. We found several orphan pezT/zeta toxins, unaccompanied by a cognate antitoxin.
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Affiliation(s)
- Wai Ting Chan
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28040 Madrid, Spain
| | - Maria Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, C/Albert Einstein 22, PCTCAN, 39011 Santander, Spain
| | - Chew Chieng Yeo
- Centre for Research in Infectious Diseases and Biotechnology (CeRIDB), Faculty of Medicine
, Universiti Sultan Zainal Abidin, Jalan Sultan Mahumd, 20400 Kuala Terengganu, Malaysia
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28040 Madrid, Spain
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2
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Xu X, Usher B, Gutierrez C, Barriot R, Arrowsmith TJ, Han X, Redder P, Neyrolles O, Blower TR, Genevaux P. MenT nucleotidyltransferase toxins extend tRNA acceptor stems and can be inhibited by asymmetrical antitoxin binding. Nat Commun 2023; 14:4644. [PMID: 37591829 PMCID: PMC10435456 DOI: 10.1038/s41467-023-40264-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 07/20/2023] [Indexed: 08/19/2023] Open
Abstract
Mycobacterium tuberculosis, the bacterium responsible for human tuberculosis, has a genome encoding a remarkably high number of toxin-antitoxin systems of largely unknown function. We have recently shown that the M. tuberculosis genome encodes four of a widespread, MenAT family of nucleotidyltransferase toxin-antitoxin systems. In this study we characterize MenAT1, using tRNA sequencing to demonstrate MenT1 tRNA modification activity. MenT1 activity is blocked by MenA1, a short protein antitoxin unrelated to the MenA3 kinase. X-ray crystallographic analysis shows blockage of the conserved MenT fold by asymmetric binding of MenA1 across two MenT1 protomers, forming a heterotrimeric toxin-antitoxin complex. Finally, we also demonstrate tRNA modification by toxin MenT4, indicating conserved activity across the MenT family. Our study highlights variation in tRNA target preferences by MenT toxins, selective use of nucleotide substrates, and diverse modes of MenA antitoxin activity.
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Affiliation(s)
- Xibing Xu
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Ben Usher
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Claude Gutierrez
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Roland Barriot
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Tom J Arrowsmith
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Xue Han
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Peter Redder
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Olivier Neyrolles
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
| | - Tim R Blower
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK.
| | - Pierre Genevaux
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France.
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3
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Deep A, Singh L, Kaur J, Velusamy M, Bhardwaj P, Singh R, Thakur KG. Structural insights into DarT toxin neutralization by cognate DarG antitoxin: ssDNA mimicry by DarG C-terminal domain keeps the DarT toxin inhibited. Structure 2023; 31:780-789.e4. [PMID: 37167974 DOI: 10.1016/j.str.2023.04.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/20/2023] [Accepted: 04/14/2023] [Indexed: 05/13/2023]
Abstract
In the DarTG toxin-antitoxin system, the DarT toxin ADP-ribosylates single-stranded DNA (ssDNA), which stalls DNA replication and plays a crucial role in controlling bacterial growth and bacteriophage infection. This toxic activity is reversed by the N-terminal macrodomain of the cognate antitoxin DarG. DarG also binds DarT, but the role of these interactions in DarT neutralization is unknown. Here, we report that the C-terminal domain of DarG (DarG toxin-binding domain [DarGTBD]) interacts with DarT to form a 1:1 stoichiometric heterodimeric complex. We determined the 2.2 Å resolution crystal structure of the Mycobacterium tuberculosis DarT-DarGTBD complex. The comparative structural analysis reveals that DarGTBD interacts with DarT at the DarT/ssDNA interaction interface, thus sterically occluding substrate ssDNA binding and consequently inactivating toxin by direct protein-protein interactions. Our data support a unique two-layered DarT toxin neutralization mechanism of DarG, which is important in keeping the toxin molecules in check under normal growth conditions.
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Affiliation(s)
- Amar Deep
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India
| | - Latika Singh
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India
| | - Japleen Kaur
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India
| | - Maheshwaran Velusamy
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India
| | - Pushpanjali Bhardwaj
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India
| | - Ramandeep Singh
- Infection and Immunology Group, Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR-Biotech Science Cluster, 3rd Milestone, Faridabad Gurugram Expressway, Faridabad-121001, India
| | - Krishan Gopal Thakur
- Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh 160036, India.
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4
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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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5
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Hernández-Ramírez KC, Valle-Maldonado MI, Patiño-Medina JA, Calo S, Jácome-Galarza IE, Garre V, Meza-Carmen V, Ramírez-Díaz MI. Role of PumB antitoxin as a transcriptional regulator of the PumAB type-II toxin-antitoxin system and its endoribonuclease activity on the PumA (toxin) transcript. Mol Genet Genomics 2023; 298:455-472. [PMID: 36604348 DOI: 10.1007/s00438-022-01988-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 12/20/2022] [Indexed: 01/07/2023]
Abstract
The PumAB type-II toxin-antitoxin (TA) system is encoded by pumAB genes that are organized into an operon. This system is encoded by the pUM505 plasmid, isolated from a Pseudomonas aeruginosa clinical strain. The pumA gene encodes a putative RelE toxin protein (toxic component), whereas the pumB gene encodes a putative HTH antitoxin protein. The expression of the PumAB system in Escherichia coli confers plasmid stability. In addition, PumA toxin overexpression in P. aeruginosa possesses the capability to increase bacterial virulence, an effect that is neutralized by the PumB antitoxin. The aim of this study was to establish the mechanism of regulation of the PumAB toxin-antitoxin system from pUM505. By an in silico analysis of the putative regulatory elements, we identified two putative internal promoters, PpumB and PpumB-AlgU (in addition to the already reported PpumAB), located upstream of pumB. By RT-qPCR assays, we determined that the pumAB genes are transcribed differentially, in that the mRNA of pumB is more abundant than the pumA transcript. We also observed that pumB could be expressed individually and that its mRNA levels decreased under oxidative stress, during individual expression as well as co-expression of pumAB. However, under stressful conditions, the pumA mRNA levels were not affected. This suggests the negative regulation of pumB by stressful conditions. The PumB purified protein was found to bind to a DNA region located between the PpumAB and the pumA coding region, and PumA participates in PumB binding, suggesting that a PumA-PumB complex co-regulates the transcription of the pumAB operon. Interestingly, the pumA mRNA levels decreased after incubation in vitro with PumB protein. This effect was repressed by ribonuclease inhibitors, suggesting that PumB could function as an RNAse toward the mRNA of the toxin. Taken together, we conclude that the PumAB TA system possesses multiple mechanisms to regulate its expression, as well as that the PumB antitoxin generates a decrease in the mRNA toxin levels, suggesting an RNase function. Our analysis provides new insights into the understanding of the control of TA systems from mobile plasmid-encoded genes from a human pathogen.
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Affiliation(s)
- K C Hernández-Ramírez
- Laboratorio de Microbiología, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B-3, Ciudad Universitaria, 58030, Morelia, Michoacán, Mexico
| | - M I Valle-Maldonado
- Laboratorio de Diferenciación Celular, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, 58030, Morelia, Michoacán, Mexico.,Laboratorio Estatal de Salud Pública, Secretaría de Salud Michoacán, Morelia, Mexico
| | - J A Patiño-Medina
- Laboratorio de Diferenciación Celular, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, 58030, Morelia, Michoacán, Mexico
| | - S Calo
- School of Natural and Exact Sciences, Pontificia Universidad Católica Madre y Maestra, 51033, Santiago de los Caballeros, Dominican Republic
| | - I E Jácome-Galarza
- Laboratorio Estatal de Salud Pública, Secretaría de Salud Michoacán, Morelia, Mexico
| | - V Garre
- Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, 30100, Murcia, Spain
| | - V Meza-Carmen
- Laboratorio de Diferenciación Celular, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, 58030, Morelia, Michoacán, Mexico
| | - M I Ramírez-Díaz
- Laboratorio de Microbiología, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B-3, Ciudad Universitaria, 58030, Morelia, Michoacán, Mexico.
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6
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The DarT/DarG Toxin-Antitoxin ADP-Ribosylation System as a Novel Target for a Rational Design of Innovative Antimicrobial Strategies. Pathogens 2023; 12:pathogens12020240. [PMID: 36839512 PMCID: PMC9967889 DOI: 10.3390/pathogens12020240] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
The chemical modification of cellular macromolecules by the transfer of ADP-ribose unit(s), known as ADP-ribosylation, is an ancient homeostatic and stress response control system. Highly conserved across the evolution, ADP-ribosyltransferases and ADP-ribosylhydrolases control ADP-ribosylation signalling and cellular responses. In addition to proteins, both prokaryotic and eukaryotic transferases can covalently link ADP-ribosylation to different conformations of nucleic acids, thus highlighting the evolutionary conservation of archaic stress response mechanisms. Here, we report several structural and functional aspects of DNA ADP-ribosylation modification controlled by the prototype DarT and DarG pair, which show ADP-ribosyltransferase and hydrolase activity, respectively. DarT/DarG is a toxin-antitoxin system conserved in many bacterial pathogens, for example in Mycobacterium tuberculosis, which regulates two clinically important processes for human health, namely, growth control and the anti-phage response. The chemical modulation of the DarT/DarG system by selective inhibitors may thus represent an exciting strategy to tackle resistance to current antimicrobial therapies.
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7
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López-Igual R, Dorado-Morales P, Mazel D. Increasing the Scalability of Toxin-Intein Orthogonal Combinations. ACS Synth Biol 2023; 12:618-623. [PMID: 36706324 PMCID: PMC9942249 DOI: 10.1021/acssynbio.2c00477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Inteins are proteins embedded into host proteins from which they are excised in an autocatalytic reaction. Specifically, split inteins are separated into two independent fragments that reconstitute the host protein during the catalytic process. We recently developed a novel strategy for the specific killing of pathogenic and antibiotic resistant bacteria based on toxin-intein combinations. Bacterial type II toxin-antitoxin systems are protein modules in which the toxin can provoke cell death whereas the antitoxin inhibits toxin activity. Although our previous system was based on a split intein (iDnaE) and the CcdB toxin, we demonstrated that iDnaE is able to reconstitute four different toxins. To expand the applicability of our system by widening the repertoire of toxin-intein combinations for complex set-ups, we introduced a second intein, iDnaX, which was artificially split. We demonstrate that iDnaX is able to reconstitute the four toxins, and we manage to reduce its scar size to facilitate their use. In addition, we prove the orthogonality of both inteins (iDnaE and iDnaX) through a toxin reconstitution assay, thus opening the possibility for complex set-ups based on these toxin-intein modules. This could be used to develop specific antimicrobial and other biotechnological applications.
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Affiliation(s)
- Rocío López-Igual
- Institut
Pasteur, Université
de Paris, Unité Plasticité du Génome Bactérien,
et CNRS, UMR3525, 28 Rue
du Dr Roux, F-75015 Paris, France,Instituto
de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 40, E-41092 Seville, Spain,
| | - Pedro Dorado-Morales
- Institut
Pasteur, Université
de Paris, Unité Plasticité du Génome Bactérien,
et CNRS, UMR3525, 28 Rue
du Dr Roux, F-75015 Paris, France
| | - Didier Mazel
- Institut
Pasteur, Université
de Paris, Unité Plasticité du Génome Bactérien,
et CNRS, UMR3525, 28 Rue
du Dr Roux, F-75015 Paris, France
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8
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Gosain TP, Singh M, Singh C, Thakur KG, Singh R. Disruption of MenT2 toxin impairs the growth of Mycobacterium tuberculosis in guinea pigs. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 36342835 DOI: 10.1099/mic.0.001246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Toxin-antitoxin (TA) systems are abundantly present in the genomes of various bacterial pathogens. TA systems have been implicated in either plasmid maintenance or protection against phage infection, stress adaptation or disease pathogenesis. The genome of Mycobacterium tuberculosis encodes for more than 90 TA systems and 4 of these belong to the type IV subfamily (MenAT family). The toxins and antitoxins belonging to type IV TA systems share sequence homology with the AbiEii family of nucleotidyl transferases and the AbiEi family of putative transcriptional regulators, respectively. Here, we have performed experiments to understand the role of MenT2, a toxin from the type IV TA system, in mycobacterial physiology and disease pathogenesis. The ectopic expression of MenT2 using inducible vectors does not inhibit bacterial growth in liquid cultures. Bioinformatic and molecular modelling analysis suggested that the M. tuberculosis genome has an alternative start site upstream of the annotated menT2 gene. The overexpression of the reannotated MenT2 resulted in moderate growth inhibition of Mycobacterium smegmatis. We show that both menT2 and menA2 transcript levels are increased when M. tuberculosis is exposed to nitrosative stress, in vitro. When compared to the survival of the wild-type and the complemented strain, the ΔmenT2 mutant strain of M. tuberculosis was more resistant to being killed by nitrosative stress. However, the survival of both the ΔmenT2 mutant and the wild-type strain was similar in macrophages and when exposed to other stress conditions. Here, we show that MenT2 is required for the establishment of disease in guinea pigs. Gross pathology and histopathology analysis of lung tissues from guinea pigs infected with the ∆menT2 strain revealed significantly reduced tissue damage and inflammation. In summary, these results provide new insights into the role of MenT2 in mycobacterial pathogenesis.
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Affiliation(s)
- Tannu Priya Gosain
- Infection and Immunology Group, Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR-Biotech Science Cluster, 3rd Milestone, Faridabad Gurugram Expressway, Faridabad-121001, India
| | - Manisha Singh
- Infection and Immunology Group, Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR-Biotech Science Cluster, 3rd Milestone, Faridabad Gurugram Expressway, Faridabad-121001, India
| | - Charandeep Singh
- Structural Biology Laboratory, G. N. Ramachandran Protein Centre, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh-160036, India
| | - Krishan Gopal Thakur
- Structural Biology Laboratory, G. N. Ramachandran Protein Centre, Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh-160036, India
| | - Ramandeep Singh
- Infection and Immunology Group, Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR-Biotech Science Cluster, 3rd Milestone, Faridabad Gurugram Expressway, Faridabad-121001, India
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9
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Sun H, Coussens NP, Danchik C, Wachsmuth LM, Henderson MJ, Patnaik S, Hall MD, Molinaro AL, Daines DA, Shen M. Discovery of Small-Molecule VapC1 Nuclease Inhibitors by Virtual Screening and Scaffold Hopping from an Atomic Structure Revealing Protein-Protein Interactions with a Native VapB1 Inhibitor. J Chem Inf Model 2022; 62:1249-1258. [PMID: 35103473 PMCID: PMC10041999 DOI: 10.1021/acs.jcim.1c01188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nontypeable Haemophilus influenzae (NTHi) are clinically important Gram-negative bacteria that are responsible for various human mucosal diseases, including otitis media (OM). Recurrent OM caused by NTHi is common, and infections that recur less than 2 weeks following antimicrobial therapy are largely attributable to the recurrence of the same strain of bacteria. Toxin-antitoxin (TA) modules encoded by bacteria enable rapid responses to environmental stresses and are thought to facilitate growth arrest, persistence, and tolerance to antibiotics. The vapBC-1 locus of NTHi encodes a type II TA system, comprising the ribonuclease toxin VapC1 and its cognate antitoxin VapB1. The activity of VapC1 has been linked to the survival of NTHi during antibiotic treatment both in vivo and ex vivo. Therefore, inhibitors of VapC1 might serve as adjuvants to antibiotics, preventing NTHi from entering growth arrest and surviving; however, none have been reported to date. A truncated VapB1 peptide from a crystal structure of the VapBC-1 complex was used to generate pharmacophore queries to facilitate a scaffold hopping approach for the identification of small-molecule VapC1 inhibitors. The National Center for Advancing Translational Sciences small-molecule library was virtually screened using the shape-based method rapid overlay of chemical structures (ROCS), and the top-ranking hits were docked into the VapB1 binding pocket of VapC1. Two hundred virtual screening hits with the best docking scores were selected and tested in a biochemical VapC1 activity assay, which confirmed eight compounds as VapC1 inhibitors. An additional 60 compounds were selected with structural similarities to the confirmed VapC1 inhibitors, of which 20 inhibited VapC1 activity. Intracellular target engagement of five inhibitors was indicated by the destabilization of VapC1 within bacterial cells from a cellular thermal shift assay; however, no impact on bacterial growth was observed. Thus, this virtual screening and scaffold hopping approach enabled the discovery of VapC1 ribonuclease inhibitors that might serve as starting points for preclinical development.
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Affiliation(s)
- Hongmao Sun
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Nathan P Coussens
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Carina Danchik
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Leah M Wachsmuth
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Mark J Henderson
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Samarjit Patnaik
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Matthew D Hall
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Ashley L Molinaro
- Office of the Dean, College of Sciences, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Dayle A Daines
- Office of the Dean, College of Sciences, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Min Shen
- National Center for Advancing Translational Sciences (NCATS), 9800 Medical Center Drive, Rockville, Maryland 20850, United States
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10
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Chen X, Hu A, Zou Q, Luo S, Wu H, Yan C, Liu T, He D, Li X, Cheng G. The Mesorhizobium huakuii transcriptional regulator AbiEi plays a critical role in nodulation and is important for bacterial stress response. BMC Microbiol 2021; 21:245. [PMID: 34511061 PMCID: PMC8436566 DOI: 10.1186/s12866-021-02304-0] [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: 05/04/2021] [Accepted: 08/28/2021] [Indexed: 11/16/2022] Open
Abstract
Background Bacterial abortive infection (Abi) systems are type IV toxin–antitoxin (TA) system, which could elicit programmed cell death and constitute a native survival strategy of pathogenic bacteria under various stress conditions. However, no rhizobial AbiE family TA system has been reported so far. Here, a M. huakuii AbiE TA system was identified and characterized. Results A mutation in M. huakuii abiEi gene, encoding an adjacent GntR-type transcriptional regulator, was generated by homologous recombination. The abiEi mutant strain grew less well in rich TY medium, and displayed increased antioxidative capacity and enhanced gentamicin resistance, indicating the abiEi operon was negatively regulated by the antitoxin AbiEi in response to the oxidative stress and a particular antibiotic. The mRNA expression of abiEi gene was significantly up-regulated during Astragalus sinicus nodule development. The abiEi mutant was severely impaired in its competitive ability in rhizosphere colonization, and was defective in nodulation with 97% reduction in nitrogen-fixing capacity. The mutant infected nodule cells contained vacuolation and a small number of abnormal bacteroids with senescence character. RNA-seq experiment revealed it had 5 up-regulated and 111 down-regulated genes relative to wild type. Of these down-regulated genes, 21 are related to symbiosis nitrogen fixation and nitrogen mechanism, 16 are involved in the electron transport chain and antioxidant responses, and 12 belong to type VI secretion system (T6SS). Conclusions M. huakuii AbiEi behaves as a key transcriptional regulator mediating root nodule symbiosis. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-021-02304-0.
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Affiliation(s)
- Xiaohong Chen
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Aiqi Hu
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Qian Zou
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Sha Luo
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Hetao Wu
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Chunlan Yan
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Tao Liu
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Donglan He
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Xiaohua Li
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
| | - Guojun Cheng
- Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, Hubei, China.
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11
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Chen R, Zhou J, Xie W. Mechanistic Insight into the Peptide Binding Modes to Two M. tb MazF Toxins. Toxins (Basel) 2021; 13:toxins13050319. [PMID: 33925254 PMCID: PMC8145246 DOI: 10.3390/toxins13050319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 04/26/2021] [Accepted: 04/26/2021] [Indexed: 11/30/2022] Open
Abstract
Tuberculosis (TB) is a contagious disease caused by Mycobacterium tuberculosis (M. tb). It is regarded as a major health threat all over the world, mainly because of its high mortality and drug-resistant nature. Toxin-antitoxin (TA) systems are modules ubiquitously found in prokaryotic organisms, and the well-studied MazEF systems (MazE means “what is it?” in Hebrew) are implicated in the formation of “persister cells” in the M. tb pathogen. Here, we report cocrystal structures of M. tb MazF-mt1 and -mt9, two important MazF members responsible for specific mRNA and tRNA cleavages, respectively, in complexes with truncated forms of their cognate antitoxin peptides. These peptides bind to the toxins with comparable affinities to their full-length antitoxins, which would reduce the RNA-cleavage capacities of the toxins in vitro. After structural analysis of the binding modes, we systemically tested the influence of the substitutions of individual residues in the truncated MazE-mt9 peptide on its affinity. This study provides structural insight into the binding modes and the inhibition mechanisms between the MazE/F-mt TA pairs. More importantly, it contributes to the future design of peptide-based antimicrobial agents against TB and potentially relieves the drug-resistance problems by targeting novel M. tb proteins.
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Affiliation(s)
- Ran Chen
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510006, China; (R.C.); (J.Z.)
- Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, Innovation Academy of South China Sea Ecology and Environmental Engineering, South China Sea Institute of Oceanology, Chinese Academy of Sciences, No.1119, Haibin Road, Nansha District, Guangzhou 511458, China
| | - Jie Zhou
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510006, China; (R.C.); (J.Z.)
| | - Wei Xie
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510006, China; (R.C.); (J.Z.)
- Correspondence:
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12
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Kang SM, Moon H, Han SW, Kim BW, Kim DH, Kim BM, Lee BJ. Toxin-Activating Stapled Peptides Discovered by Structural Analysis Were Identified as New Therapeutic Candidates That Trigger Antibacterial Activity against Mycobacterium tuberculosis in the Mycobacterium smegmatis Model. Microorganisms 2021; 9:microorganisms9030568. [PMID: 33801872 PMCID: PMC8000039 DOI: 10.3390/microorganisms9030568] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/02/2021] [Accepted: 03/03/2021] [Indexed: 11/17/2022] Open
Abstract
The structure-function relationships of toxin-antitoxin (TA) systems from Mycobacterium tuberculosis have prompted the development of novel and effective antimicrobial agents that selectively target this organism. The artificial activation of toxins by peptide inhibitors can lead to the growth arrest and eventual death of bacterial cells. Optimizing candidate peptides by hydrocarbon α-helix stapling based on structural information from the VapBC TA system and in vitro systematic validation led to V26-SP-8, a VapC26 activator of M. tuberculosis. This compound exhibited highly enhanced activity and cell permeability owing to the stabilizing helical propensity of the peptide. These characteristics will increase its efficacy against multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis. Similar approaches utilizing structural and biochemical information for new antibiotic targets opens a new era for developing TB therapies.
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Affiliation(s)
- Sung-Min Kang
- College of Pharmacy, Duksung Women’s University, Seoul 01369, Korea;
| | - Heejo Moon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Korea; (H.M.); (B.W.K.)
| | - Sang-Woo Han
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Korea;
| | - Byeong Wook Kim
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Korea; (H.M.); (B.W.K.)
| | - Do-Hee Kim
- College of Pharmacy, Jeju National University, Jeju 63243, Korea;
- Interdisciplinary Graduate Program in Advanced Convergence Technology & Science, Jeju National University, Jeju 63243, Korea
| | - Byeong Moon Kim
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Korea; (H.M.); (B.W.K.)
- Correspondence: (B.M.K.); (B.-J.L.); Tel.: +82-2-880-6634 (B.M.K.); +82-2-880-7868 (B.-J.L.)
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Korea;
- Correspondence: (B.M.K.); (B.-J.L.); Tel.: +82-2-880-6634 (B.M.K.); +82-2-880-7868 (B.-J.L.)
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13
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Xue L, Yue J, Ke J, Khan MH, Wen W, Sun B, Zhu Z, Niu L. Distinct oligomeric structures of the YoeB-YefM complex provide insights into the conditional cooperativity of type II toxin-antitoxin system. Nucleic Acids Res 2020; 48:10527-10541. [PMID: 32845304 PMCID: PMC7544224 DOI: 10.1093/nar/gkaa706] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 08/07/2020] [Accepted: 08/14/2020] [Indexed: 12/21/2022] Open
Abstract
YoeB-YefM, the widespread type II toxin-antitoxin (TA) module, binds to its own promoter to autoregulate its transcription: repress or induce transcription under normal or stress conditions, respectively. It remains unclear how YoeB-YefM regulates its transcription depending on the YoeB to YefM TA ratio. We find that YoeB-YefM complex from S.aureus exists as two distinct oligomeric assemblies: heterotetramer (YoeB-YefM2-YoeB) and heterohexamer (YoeB-YefM2-YefM2-YoeB) with low and high DNA-binding affinities, respectively. Structures of the heterotetramer alone and heterohexamer bound to promoter DNA reveals that YefM C-terminal domain undergoes disorder to order transition upon YoeB binding, which allosterically affects the conformation of N-terminal DNA-binding domain. At TA ratio of 1:2, unsaturated binding of YoeB to the C-terminal regions of YefM dimer forms an optimal heterohexamer for DNA binding, and two YefM dimers with N-terminal domains dock into the adjacent major grooves of DNA to specifically recognize the 5'-TTGTACAN6AGTACAA-3' palindromic sequence, resulting in transcriptional repression. In contrast, at TA ratio of 1:1, binding of two additional YoeB molecules onto the heterohexamer induces the completely ordered conformation of YefM and disassembles the heterohexamer into two heterotetramers, which are unable to bind the promoter DNA optimally due to steric clashes, hence derepresses TA operon transcription.
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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 230026, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, 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 230026, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jiyuan Ke
- Lead Discovery Department, H3 Biomedicine Inc, 300 Technology Square FL 5, Cambridge, MA 02139, USA
| | - 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 230026, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wen Wen
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Baolin Sun
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, 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 230026, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, 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 230026, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
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14
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Kang SM, Jin C, Kim DH, Lee Y, Lee BJ. Structural and Functional Study of the Klebsiella pneumoniae VapBC Toxin-Antitoxin System, Including the Development of an Inhibitor That Activates VapC. J Med Chem 2020; 63:13669-13679. [PMID: 33146528 DOI: 10.1021/acs.jmedchem.0c01118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Klebsiella pneumoniae is one of the most critical opportunistic pathogens. TA systems are promising drug targets because they are related to the survival of bacterial pathogens. However, structural information on TA systems in K. pneumoniae remains lacking; therefore, it is necessary to explore this information for the development of antibacterial agents. Here, we present the first crystal structure of the VapBC complex from K. pneumoniae at a resolution of 2.00 Å. We determined the toxin inhibitory mechanism of the VapB antitoxin through an Mg2+ switch, in which Mg2+ is displaced by R79 of VapB. This inhibitory mechanism of the active site is a novel finding and the first to be identified in a bacterial TA system. Furthermore, inhibitors, including peptides and small molecules, that activate the VapC toxin were discovered and investigated. These inhibitors can act as antimicrobial agents by disrupting the VapBC complex and activating VapC. Our comprehensive investigation of the K. pneumoniae VapBC system will help elucidate an unsolved conundrum in VapBC systems and develop potential antimicrobial agents.
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Affiliation(s)
- Sung-Min Kang
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Korea
| | - Chenglong Jin
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Korea
| | - Do-Hee Kim
- College of Pharmacy, Jeju National University, Jeju 63243, Korea.,Interdisciplinary Graduate Program in Advanced Convergence Technology & Science, Jeju National University, Jeju 63243, Korea
| | - Yuno Lee
- Korea Chemical Bank, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Korea
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15
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Khan F, Pham DTN, Tabassum N, Oloketuyi SF, Kim YM. Treatment strategies targeting persister cell formation in bacterial pathogens. Crit Rev Microbiol 2020; 46:665-688. [DOI: 10.1080/1040841x.2020.1822278] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Fazlurrahman Khan
- Institute of Food Science, Pukyong National University, Busan, Korea
| | - Dung Thuy Nguyen Pham
- Department of Food Science and Technology, Pukyong National University, Busan, Korea
| | - Nazia Tabassum
- Industrial Convergence Bionix Engineering, Pukyong National University, Busan, Korea
| | | | - Young-Mog Kim
- Institute of Food Science, Pukyong National University, Busan, Korea
- Department of Food Science and Technology, Pukyong National University, Busan, Korea
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16
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Kang SM, Moon H, Han SW, Kim DH, Kim BM, Lee BJ. Structure-Based De Novo Design of Mycobacterium Tuberculosis VapC-Activating Stapled Peptides. ACS Chem Biol 2020; 15:2493-2498. [PMID: 32840352 DOI: 10.1021/acschembio.0c00492] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Toxin-antitoxin (TA) systems have been considered essential factors for bacterial survival. During our drug development program aimed against tuberculosis (TB), we discovered certain peptides that mimic the binding of the VapBC30 complex, leading to the arrest of bacterial cell growth and eventually cell death. Herein, we optimized these candidate peptides based on a hydrocarbon stapling strategy and performed biological in vitro evaluations. The V30-SP-8 peptide successfully penetrated Mycobacterium smegmatis cell membranes and exerted bactericidal activity at a minimum inhibitory concentration that inhibited 50% of the isolates (MIC50) < 6.25 μM. With the aid of structural and biochemical information for the VapBC30 TA system from M. tuberculosis, we suggest potential antimicrobial agents that could provide a platform to establish a novel antibacterial strategy. Reflecting the limited number of therapeutic agents targeting TA systems, we believe that this study not only provides chemical tools for exploring the biological events relevant to TA systems but also opens a new gateway toward TB drug discovery.
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Affiliation(s)
- Sung-Min Kang
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Republic of Korea
| | - Heejo Moon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Sang-Woo Han
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Republic of Korea
| | - Do-Hee Kim
- College of Pharmacy, Jeju National University, Jeju 63243, Republic of Korea
- Interdisciplinary Graduate Program in Advanced Convergence Technology & Science, Jeju National University, Jeju, 63243 Republic of Korea
| | - Byeong Moon Kim
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 08826, Republic of Korea
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17
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Evaluating the Potential for Cross-Interactions of Antitoxins in Type II TA Systems. Toxins (Basel) 2020; 12:toxins12060422. [PMID: 32604745 PMCID: PMC7354431 DOI: 10.3390/toxins12060422] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 01/21/2023] Open
Abstract
The diversity of Type-II toxin–antitoxin (TA) systems in bacterial genomes requires tightly controlled interaction specificity to ensure protection of the cell, and potentially to limit cross-talk between toxin–antitoxin pairs of the same family of TA systems. Further, there is a redundant use of toxin folds for different cellular targets and complexation with different classes of antitoxins, increasing the apparent requirement for the insulation of interactions. The presence of Type II TA systems has remained enigmatic with respect to potential benefits imparted to the host cells. In some cases, they play clear roles in survival associated with unfavorable growth conditions. More generally, they can also serve as a “cure” against acquisition of highly similar TA systems such as those found on plasmids or invading genetic elements that frequently carry virulence and resistance genes. The latter model is predicated on the ability of these highly specific cognate antitoxin–toxin interactions to form cross-reactions between chromosomal antitoxins and invading toxins. This review summarizes advances in the Type II TA system models with an emphasis on antitoxin cross-reactivity, including with invading genetic elements and cases where toxin proteins share a common fold yet interact with different families of antitoxins.
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18
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Klimina KM, Voroshilova VN, Poluektova EU, Veselovsky VA, Yunes RA, Kovtun AS, Kudryavtseva AV, Kasianov AS, Danilenko VN. Toxin-Antitoxin Systems: A Tool for Taxonomic Analysis of Human Intestinal Microbiota. Toxins (Basel) 2020; 12:toxins12060388. [PMID: 32545455 PMCID: PMC7354421 DOI: 10.3390/toxins12060388] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 01/14/2023] Open
Abstract
The human gastrointestinal microbiota (HGM) is known for its rich diversity of bacterial species and strains. Yet many studies stop at characterizing the HGM at the family level. This is mainly due to lack of adequate methods for a high-resolution profiling of the HGM. One way to characterize the strain diversity of the HGM is to look for strain-specific functional markers. Here, we propose using type II toxin-antitoxin systems (TAS). To identify TAS systems in the HGM, we previously developed the software TAGMA. This software was designed to detect the TAS systems, MazEF and RelBE, in lactobacilli and bifidobacteria. In this study, we updated the gene catalog created previously and used it to test our software anew on 1346 strains of bacteria, which belonged to 489 species and 49 genera. We also sequenced the genomes of 20 fecal samples and analyzed the results with TAGMA. Although some differences were detected at the strain level, the results showed no particular difference in the bacterial species between our method and other classic analysis software. These results support the use of the updated catalog of genes encoding type II TAS as a useful tool for computer-assisted species and strain characterization of the HGM.
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Affiliation(s)
- Ksenia M. Klimina
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435 Moscow, Russia;
- Correspondence:
| | - Viktoriya N. Voroshilova
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701 Moscow, Russia
| | - Elena U. Poluektova
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
| | - Vladimir A. Veselovsky
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435 Moscow, Russia;
| | - Roman A. Yunes
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
| | - Aleksey S. Kovtun
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701 Moscow, Russia
| | - Anna V. Kudryavtseva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia;
| | - Artem S. Kasianov
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701 Moscow, Russia
| | - Valery N. Danilenko
- Vavilov Institute of General Genetics Russian Academy of Sciences, 119991 Moscow, Russia; (V.N.V.); (E.U.P.); (R.A.Y.); (A.S.K.); (A.S.K.); (V.N.D.)
- Faculty of Ecology, International Institute for Strategic Development of Sectoral Economics, Peoples’ Friendship University of Russia (RUDN University), 117198 Moscow, Russia
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19
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Park D, Yoon HJ, Lee KY, Park SJ, Cheon SH, Lee HH, Lee SJ, Lee BJ. Crystal structure of proteolyzed VapBC and DNA-bound VapBC from Salmonella enterica Typhimurium LT2 and VapC as a putative Ca 2+ -dependent ribonuclease. FASEB J 2020; 34:3051-3068. [PMID: 31908032 DOI: 10.1096/fj.201901989r] [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: 08/05/2019] [Revised: 12/13/2019] [Accepted: 12/16/2019] [Indexed: 12/22/2022]
Abstract
Bacterial toxin-antitoxin (TA) system has gained attention for its essential roles in cellular maintenance and survival under harsh environmental conditions such as nutrient deficiency and antibiotic treatment. There are at least 14 TA systems in Salmonella enterica serovar Typhimurium LT2, a pathogenic bacterium, and none of the structures of these TA systems have been determined. We determined the crystal structure of the VapBC TA complex from S. Typhimurium LT2 in proteolyzed and DNA-bound forms at 2.0 Å and 2.8 Å resolution, respectively. The VapC toxin possesses a pilT N-terminal domain (PIN-domain) that shows ribonuclease activity, and the VapB antitoxin has an AbrB-type DNA binding domain. In addition, the structure revealed details of interaction mode between VapBC and the cognate promoter DNA, including the inhibition of VapC by VapB and linear conformation of bound DNA in the VapBC complex. The complexation of VapBC with the linear DNA is not consistent with known structures of VapBC homologs in complex with bent DNA. We also identified VapC from S. Typhimurium LT2 as a putative Ca2+ -dependent ribonuclease, which differs from previous data showing that VapC homologs have Mg2+ or Mn2+ -dependent ribonuclease activities. The present studies could provide structural understanding of the physiology of VapBC systems and foundation for the development of new antibiotic drugs against Salmonella infection.
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Affiliation(s)
- DongWon Park
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Republic of Korea
| | - Hye-Jin Yoon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Ki-Young Lee
- Department of Medical Biophysics, University of Toronto, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Sung-Jean Park
- College of Pharmacy, Gachon University, Incheon, Republic of Korea
| | - Seung-Ho Cheon
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Republic of Korea
| | - Hyung Ho Lee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Sang Jae Lee
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Korea
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Republic of Korea
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20
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Farhadi T, Hashemian SM, Farhadi Z. In Silico Designing of Peptidomimetics Enhancing Endoribonucleolytic Activities of Acinetobacter MazF Toxin as the Novel Anti-bacterial Candidates. Int J Pept Res Ther 2019. [DOI: 10.1007/s10989-019-09908-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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21
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Kim DH, Kang SM, Park SJ, Jin C, Yoon HJ, Lee BJ. Functional insights into the Streptococcus pneumoniae HicBA toxin-antitoxin system based on a structural study. Nucleic Acids Res 2019; 46:6371-6386. [PMID: 29878152 PMCID: PMC6159526 DOI: 10.1093/nar/gky469] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 05/15/2018] [Indexed: 12/12/2022] Open
Abstract
Streptococcus pneumonia has attracted increasing attention due to its resistance to existing antibiotics. TA systems are essential for bacterial persistence under stressful conditions such as nutrient deprivation, antibiotic treatment, and immune system attacks. In particular, S. pneumoniae expresses the HicBA TA gene, which encodes the stable HicA toxin and the labile HicB antitoxin. These proteins interact to form a non-toxic TA complex under normal conditions, but the toxin is activated by release from the antitoxin in response to unfavorable growth conditions. Here, we present the first crystal structure showing the complete conformation of the HicBA complex from S. pneumonia. The structure reveals that the HicA toxin contains a double-stranded RNA-binding domain that is essential for RNA recognition and that the C-terminus of the HicB antitoxin folds into a ribbon-helix-helix DNA-binding motif. The active site of HicA is sterically blocked by the N-terminal region of HicB. RNase activity assays show that His36 is essential for the ribonuclease activity of HicA, and nuclear magnetic resonance (NMR) spectra show that several residues of HicB participate in binding to the promoter DNA of the HicBA operon. A toxin-mimicking peptide that inhibits TA complex formation and thereby increases toxin activity was designed, providing a novel approach to the development of new antibiotics.
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Affiliation(s)
- Do-Hee Kim
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Sung-Min Kang
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Sung Jean Park
- College of Pharmacy and Gachon Institute of Pharmaceutical Sciences, Gachon University, 534-2 Yeonsu-dong, Yeonsu-gu, Incheon 13120, Republic of Korea
| | - Chenglong Jin
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Hye-Jin Yoon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Bong-Jin Lee
- The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
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22
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Ames JR, Muthuramalingam M, Murphy T, Najar FZ, Bourne CR. Expression of different ParE toxins results in conserved phenotypes with distinguishable classes of toxicity. Microbiologyopen 2019; 8:e902. [PMID: 31309747 PMCID: PMC6813445 DOI: 10.1002/mbo3.902] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 06/12/2019] [Accepted: 06/18/2019] [Indexed: 01/10/2023] Open
Abstract
Toxin–antitoxin (TA) systems are found on both chromosomes and plasmids. These systems are unique in that they can confer both fatal and protective effects on bacterial cells—a quality that could potentially be harnessed given further understanding of these TA mechanisms. The current work focuses on the ParE subfamily, which is found throughout proteobacteria and has a sequence identity on average of approximately 12% (similarity at 30%–80%). Our aim is to evaluate the equivalency of chromosomally derived ParE toxin activity depending on its bacterial species of origin. Nine ParE toxins were analyzed, originating from six different bacterial species. Based on the resulting toxicity, three categories can be established: ParE toxins that do not exert toxicity under the experimental conditions, toxins that exert toxicity within the first four hours, and those that exert toxicity only after 10–12 hr of exposure. All tested ParE toxins produce a cellular morphologic change from rods to filaments, consistent with disruption of DNA topology. Analysis of the distribution of filamented cells within a population reveals a correlation between the extent of filamentation and toxicity. No membrane septation is visible along the length of the cell filaments, whereas aberrant lipid blebs are evident. Potent ParE‐mediated toxicity is also correlated with a hallmark signature of abortive DNA replication, consistent with the inhibition of DNA gyrase.
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Affiliation(s)
- Jessica R Ames
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | | | - Tamiko Murphy
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Fares Z Najar
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Christina R Bourne
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
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23
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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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24
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Muthuramalingam M, White JC, Murphy T, Ames JR, Bourne CR. The toxin from a ParDE toxin-antitoxin system found in Pseudomonas aeruginosa offers protection to cells challenged with anti-gyrase antibiotics. Mol Microbiol 2019; 111:441-454. [PMID: 30427086 PMCID: PMC6368863 DOI: 10.1111/mmi.14165] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2018] [Indexed: 12/13/2022]
Abstract
Toxin-antitoxin systems are mediators of diverse activities in bacterial physiology. For the ParE-type toxins, their reported role of gyrase inhibition utilized during plasmid-segregation killing indicates they are toxic. However, their location throughout chromosomes leads to questions about function, including potential non-toxic outcomes. The current study has characterized a ParDE system from the opportunistic human pathogen Pseudomonas aeruginosa (Pa). We identified a protective function for this ParE toxin, PaParE, against effects of quinolone and other antibiotics. However, higher concentrations of PaParE are themselves toxic to cells, indicating the phenotypic outcome can vary based on its concentration. Our assays confirmed PaParE inhibition of gyrase-mediated supercoiling of DNA with an IC50 value in the low micromolar range, a species-specificity that resulted in more efficacious inhibition of Escherichia coli derived gyrase versus Pa gyrase, and overexpression in the absence of antitoxin yielded an expected filamentous morphology with multi-foci nucleic acid material. Additional data revealed that the PaParE toxin is monomeric and interacts with dimeric PaParD antitoxin with a KD in the lower picomolar range, yielding a heterotetramer. This work provides novel insights into chromosome-encoded ParE function, whereby its expression can impart partial protection to cultures from selected antibiotics.
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Affiliation(s)
- Meenakumari Muthuramalingam
- The University of Oklahoma, Department of Chemistry and BiochemistryNorman73019OKUSA
- Present address:
Department of Pharmaceutical ChemistryUniversity of KansasLawrence66047 KSUSA
| | - John C. White
- The University of Oklahoma, Department of Chemistry and BiochemistryNorman73019OKUSA
| | - Tamiko Murphy
- The University of Oklahoma, Department of Chemistry and BiochemistryNorman73019OKUSA
| | - Jessica R. Ames
- The University of Oklahoma, Department of Chemistry and BiochemistryNorman73019OKUSA
| | - Christina R. Bourne
- The University of Oklahoma, Department of Chemistry and BiochemistryNorman73019OKUSA
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25
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Coskun USS, Cicek AC, Kilinc C, Guckan R, Dagcioglu Y, Demir O, Sandalli C. Effect of mazEF, higBA and relBE toxin-antitoxin systems on antibiotic resistance in Pseudomonas aeruginosa and Staphylococcus isolates. Malawi Med J 2019; 30:67-72. [PMID: 30627331 PMCID: PMC6307074 DOI: 10.4314/mmj.v30i2.3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background A toxin-antitoxin (TA) system is a set of two or more closely linked genes that are encoded as a poison and a corresponding antidote on a protein. In typical bacterial physiology, an antitoxin binds to a toxin and neutralizes it, which prevents the bacterium from killing itself. We aimed to determine whether P.aeruginosa and Staphylococcus isolates have TA genes and to investigate whether there is a relationship between the expression levels of TA genes and resistance to antibiotics. Methods This study included 92 P. aeruginosa and 148 Staphylococcus isolates. RelBE, higBA genes were investigated in P.aeruginosa by multiplex polymerase chain reaction (PCR). The mazEF gene and the all TA genes expression were detected by real time PCR. Results RelBE and higBA genes were detected in 100% of P. aeruginosa. It was found that the level of relBE TA gene expression is increased in isolates sensitive to aztreonam compared to resistant isolates (p<0.05). The mazEF gene was detected in 89.1% of Staphylococcus isolates. In terms of MazEF gene expression level there was no significant difference between methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) isolates (p>0.05) whereas there was a significant difference between MSSA and coagulase-negative Staphylococcus (CNS) isolates, MRSA and CNS isolates (p<0.05). The levels of mazEF gene expression were found to be higher in isolates sensitive to gentamicin, ciprofloxacin, levofloxacin, clindamycin, phosphomycine, nitrofurantoin, fusidic acid, cefoxitin compared to resistant isolates (p<0.05). Conclusion Studies on the prevalence and functionality of TA systems emphasize that it may be possible to have new sensitive regions in bacteria by activating TA systems. The results of this study lead to the idea that resistance to antibiotics can be reduced by increasing TA gene expression levels. But there is need for further studies to support and develop this issue.
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Affiliation(s)
- Umut Safiye Say Coskun
- Gaziosmanpasa University Faculty of Medicine, Department of Medical Microbiology, Turkey
| | - Aysegul Copur Cicek
- Recep Tayyip Erdoğan University Faculty of Medicine, Department of Medical Microbiology, Turkey
| | - Cetin Kilinc
- Amasya University Sabuncuoglu Serafeddin Training and Research Hospital, Department of Microbiology, Turkey
| | - Ridvan Guckan
- Amasya University Sabuncuoglu Serafeddin Training and Research Hospital, Department of Microbiology, Turkey
| | - Yelda Dagcioglu
- Gaziosmanpasa Universirty Training And Research Hospital, Microbiology Laboratory, Turkey
| | - Osman Demir
- Gaziosmanpasa University School of Medicine, Department of Biostatistics, Turkey
| | - Cemal Sandalli
- Recep Tayyip Erdoğan University Faculty of Medicine, Department of Medical Microbiology, Turkey
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26
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Isolation and characterization of bacteriophage NTR1 infectious for Nocardia transvalensis and other Nocardia species. Virus Genes 2018; 55:257-265. [DOI: 10.1007/s11262-018-1625-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 12/11/2018] [Indexed: 10/27/2022]
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ClpAP protease is a universal factor that activates the parDE toxin-antitoxin system from a broad host range RK2 plasmid. Sci Rep 2018; 8:15287. [PMID: 30327496 PMCID: PMC6191456 DOI: 10.1038/s41598-018-33726-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 10/04/2018] [Indexed: 12/12/2022] Open
Abstract
The activity of type II toxin-antitoxin systems (TA), which are responsible for many important features of bacterial cells, is based on the differences between toxin and antitoxin stabilities. The antitoxin lability results from bacterial protease activity. Here, we investigated how particular Escherichia coli cytosolic proteases, namely, Lon, ClpAP, ClpXP, and ClpYQ, affect the stability of both the toxin and antitoxin components of the parDE system from the broad host range plasmid RK2. The results of our in vivo and in vitro experiments show that the ParD antitoxin is degraded by the ClpAP protease, and dsDNA stimulates this process. The ParE toxin is not degraded by any of these proteases and can therefore cause growth inhibition of plasmid-free cells after an unequal plasmid distribution during cell division. We also demonstrate that the ParE toxin interaction with ParD prevents antitoxin proteolysis by ClpAP; however, this interaction does not prevent the ClpAP interaction with ParD. We show that ClpAP protease homologs affect plasmid stability in other bacterial species, indicating that ClpAP is a universal activator of the parDE system and that ParD is a universal substrate for ClpAP.
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28
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Neoteric advancement in TB drugs and an overview on the anti-tubercular role of peptides through computational approaches. Microb Pathog 2017; 114:80-89. [PMID: 29174699 DOI: 10.1016/j.micpath.2017.11.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 11/21/2022]
Abstract
Tuberculosis (TB) is a devastating threat to human health whose treatment without the emergence of drug resistant Mycobacterium tuberculosis (M. tuberculosis) is the million-dollar question at present. The pathogenesis of M. tuberculosis has been extensively studied which represents unique defence strategies by infecting macrophages. Several anti-tubercular drugs with varied mode of action and administration from diversified sources have been used for the treatment of TB that later contributed to the emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB). However, few of potent anti-tubercular drugs are scheduled for clinical trials status in 2017-2018. Peptides of varied origins such as human immune cells and non-immune cells, bacteria, fungi, and venoms have been widely investigated as anti-tubercular agents for the replacement of existing anti-tubercular drugs in future. In the present review, we spotlighted not only on the mechanisms of action and mode of administration of currently available anti-tubercular drugs but also the recent comprehensive report of World Health Organization (WHO) on TB epidemic, diagnosis, prevention, and treatment. The major excerpt of the study also inspects the direct contribution of different computational tools during drug designing strategies against M. tuberculosis in order to grasp the interplay between anti-tubercular peptides and targeted bacterial protein. The potentiality of some of these anti-tubercular peptides as therapeutic agents unlocks a new portal for achieving the goal of end TB strategy.
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29
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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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30
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Sprenger H, Kienesberger S, Pertschy B, Pöltl L, Konrad B, Bhutada P, Vorkapic D, Atzmüller D, Feist F, Högenauer C, Gorkiewicz G, Zechner EL. Fic Proteins of Campylobacter fetus subsp. venerealis Form a Network of Functional Toxin-Antitoxin Systems. Front Microbiol 2017; 8:1965. [PMID: 29089929 PMCID: PMC5651007 DOI: 10.3389/fmicb.2017.01965] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 09/25/2017] [Indexed: 01/02/2023] Open
Abstract
Enzymes containing the FIC (filamentation induced by cyclic AMP) domain catalyze post-translational modifications of target proteins. In bacteria the activity of some Fic proteins resembles classical toxin–antitoxin (TA) systems. An excess of toxin over neutralizing antitoxin can enable bacteria to survive some stress conditions by slowing metabolic processes and promoting dormancy. The cell can return to normal growth when sufficient antitoxin is present to block toxin activity. Fic genes of the human and animal pathogen Campylobacter fetus are significantly associated with just one subspecies, which is specifically adapted to the urogenital tract. Here, we demonstrate that the fic genes of virulent isolate C. fetus subsp. venerealis 84-112 form multiple TA systems. Expression of the toxins in Escherichia coli caused filamentation and growth inhibition phenotypes reversible by concomitant antitoxin expression. Key active site residues involved in adenylylation by Fic proteins are conserved in Fic1, Fic3 and Fic4, but degenerated in Fic2. We show that both Fic3 and the non-canonical Fic2 disrupt assembly and function of E. coli ribosomes when expressed independently of a trans-acting antitoxin. Toxicity of the Fic proteins is controlled by different mechanisms. The first involves intramolecular regulation by an inhibitory helix typical for Fic proteins. The second is an unusual neutralization by heterologous Fic–Fic protein interactions. Moreover, a small interacting antitoxin called Fic inhibitory protein 3, which appears unrelated to known Fic antitoxins, has the novel capacity to bind and neutralize Fic toxins encoded in cis and at distant sites. These findings reveal a remarkable system of functional crosstalk occurring between Fic proteins expressed from chromosomal and extrachromosomal modules. Conservation of fic genes in other bacteria that either inhabit or establish pathology in the urogenital tract of humans and animals underscores the significance of these factors for niche-specific adaptation and virulence.
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Affiliation(s)
- Hanna Sprenger
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.,Institute of Pathology, Medical University of Graz, Graz, Austria.,Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
| | - Sabine Kienesberger
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.,Institute of Pathology, Medical University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria
| | - Brigitte Pertschy
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Lisa Pöltl
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Bettina Konrad
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Priya Bhutada
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Dina Vorkapic
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Denise Atzmüller
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Florian Feist
- Vehicle Safety Institute, Graz University of Technology, Graz, Austria
| | - Christoph Högenauer
- Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
| | - Gregor Gorkiewicz
- Institute of Pathology, Medical University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria
| | - Ellen L Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria
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31
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Hernández-Ramírez KC, Chávez-Jacobo VM, Valle-Maldonado MI, Patiño-Medina JA, Díaz-Pérez SP, Jácome-Galarza IE, Ortiz-Alvarado R, Meza-Carmen V, Ramírez-Díaz MI. Plasmid pUM505 encodes a Toxin-Antitoxin system conferring plasmid stability and increased Pseudomonas aeruginosa virulence. Microb Pathog 2017; 112:259-268. [PMID: 28970172 DOI: 10.1016/j.micpath.2017.09.060] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/20/2017] [Accepted: 09/28/2017] [Indexed: 12/19/2022]
Abstract
Pseudomonas aeruginosa plasmid pUM505 possesses a pathogenicity island that contains the pumAB genes that encode products with sequence similarity to Toxin-Antitoxin (TA) modules. RT-PCR assays on the overlapping regions of the pumAB genes generated a bicistronic messenger RNA, suggesting that they form an operon. When the pumAB genes were cloned into the pJET vector, recombinant plasmid pJET-pumAB was maintained under nonselective conditions in Escherichia coli cells after six daily subcultures, whereas pJET without pumAB genes was lost. These data indicate that pumAB genes confer post-segregational plasmid stability. In addition, overexpression of the PumA protein in the E. coli BL21 strain resulted in a significant growth inhibition, while BL21 co-expressing the PumA and PumB proteins did not show growth inhibition. These results indicate that pumAB genes encode a TA system where the PumB protein counters the toxic effects of the PumA toxin. Furthermore, P. aeruginosa PAO1 transformants with the pumA gene increased Caenorhabditis elegans and mouse mortality rate and improved mouse organ invasion, effects neutralized by the PumB protein. Moreover, purified recombinant His-PumA protein decreased the viability of C. elegans, indicating that the PumA protein could acts as a toxin. These results indicate that PumA has the potential to promoter the PAO1 virulence against C. elegans and mice when is expressed in absence of PumB. This is the first description, to our knowledge, of a plasmid-encoded TA system that confers plasmid stability and encoded a toxin with the possible ability to increase the P. aeruginosa virulence.
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Affiliation(s)
- K C Hernández-Ramírez
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - V M Chávez-Jacobo
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - M I Valle-Maldonado
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - J A Patiño-Medina
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - S P Díaz-Pérez
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - I E Jácome-Galarza
- Laboratorio Estatal de Salud Pública, Secretaría de Salud Michoacán, Morelia, Mexico
| | - R Ortiz-Alvarado
- Facultad de Químico-Farmacobiología, Universidad Michoacana, Morelia, Mexico
| | - V Meza-Carmen
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico
| | - M I Ramírez-Díaz
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Morelia, Michoacán, Mexico.
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32
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Klimina KM, Poluektova EU, Danilenko VN. Bacterial toxin–antitoxin systems: Properties, functional significance, and possibility of use (Review). APPL BIOCHEM MICRO+ 2017. [DOI: 10.1134/s0003683817050076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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33
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Santiago ADS, Mendes JS, Dos Santos CA, de Toledo MAS, Beloti LL, Crucello A, Horta MAC, Favaro MTDP, Munar DMM, de Souza AA, Cotta MA, de Souza AP. The Antitoxin Protein of a Toxin-Antitoxin System from Xylella fastidiosa Is Secreted via Outer Membrane Vesicles. Front Microbiol 2016; 7:2030. [PMID: 28066356 PMCID: PMC5167779 DOI: 10.3389/fmicb.2016.02030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 12/02/2016] [Indexed: 11/22/2022] Open
Abstract
The Xylella fastidiosa subsp pauca strain 9a5c is a Gram-negative, xylem-limited bacterium that is able to form a biofilm and affects citrus crops in Brazil. Some genes are considered to be involved in biofilm formation, but the specific mechanisms involved in this process remain unknown. This limited understanding of how some bacteria form biofilms is a major barrier to our comprehension of the progression of diseases caused by biofilm-producing bacteria. Several investigations have shown that the toxin-antitoxin (TA) operon is related to biofilm formation. This operon is composed of a toxin with RNAse activity and its cognate antitoxin. Previous reports have indicated that the antitoxin is able to inhibit toxin activity and modulate the expression of the operon as well as other target genes involved in oxidative stress and mobility. In this study, we characterize a toxin-antitoxin system consisting of XfMqsR and XfYgiT, respectively, from X. fastidiosa subsp. pauca strain 9a5c. These proteins display a high similarity to their homologs in X. fastidiosa strain Temecula and a predicted tridimensional structure that is similar to MqsR-YgiT from Escherichia coli. The characterization was performed using in vitro assays such as analytical ultracentrifugation (AUC), size exclusion chromatography, isothermal titration calorimetry, and Western blotting. Using a fluorometric assay to detect RNAses, we demonstrated that XfMqsR is thermostable and can degrade RNA. XfMqsR is inhibited by XfYgiT, which interacts with its own promoter. XfYgiT is known to be localized in the intracellular compartment; however, we provide strong evidence that X. fastidiosa secretes wild-type XfYgiT into the extracellular environment via outer membrane vesicles, as confirmed by Western blotting and specific immunofluorescence labeling visualized by fluorescence microscopy. Taken together, our results characterize the TA system from X. fastidiosa strain 9a5c, and we also discuss the possible influence of wild-type XfYgiT in the cell.
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Affiliation(s)
- André da Silva Santiago
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Juliano S Mendes
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Clelton A Dos Santos
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Marcelo A S de Toledo
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Lilian L Beloti
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Aline Crucello
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Maria A C Horta
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Marianna T de Pinho Favaro
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Brazil
| | - Duber M M Munar
- Departamento de Física Aplicada, Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas Campinas, Brazil
| | | | - Mônica A Cotta
- Departamento de Física Aplicada, Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas Campinas, Brazil
| | - Anete P de Souza
- Centro de Biologia Molecular e Engenharia Genética, Instituto de Biologia, Universidade Estadual de CampinasCampinas, Brazil; Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de CampinasCampinas, Brazil
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Jaiswal S, Paul P, Padhi C, Ray S, Ryan D, Dash S, Suar M. The Hha-TomB Toxin-Antitoxin System Shows Conditional Toxicity and Promotes Persister Cell Formation by Inhibiting Apoptosis-Like Death in S. Typhimurium. Sci Rep 2016; 6:38204. [PMID: 27910884 PMCID: PMC5133643 DOI: 10.1038/srep38204] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 06/03/2016] [Indexed: 11/09/2022] Open
Abstract
Toxin-antitoxin (TA) modules are two component “addictive” genetic elements found on either plasmid or bacterial chromosome, sometimes on both. TA systems perform a wide range of functions like biofilm formation, persistence, programmed cell death, phage abortive infection etc. Salmonella has been reported to contain several such TA systems. However, the hemolysin expression modulating protein (Hha) and its adjacent uncharacterized hypothetical protein TomB (previously known as YbaJ), have not been listed as a TA module in Salmonella. In this study we established that Hha and TomB form a bonafide TA system where Hha serves as a toxin while TomB functions as an antitoxin. Interestingly, the toxicity of Hha was conditional causing cell death under acid stress. The antitoxin attenuated the toxicity of Hha by forming a TA complex through stable interactions. The Hha-TomB TA system was found to increase persistence and inhibit programmed cell death under antibiotic stress where a phenotypically diverse population expressing differential level of TA components was observed. Therefore we propose that Hha and TomB prevent cells from committing suicide thereby promoting persister cell formation.
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Affiliation(s)
- Sangeeta Jaiswal
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
| | - Prajita Paul
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
| | | | - Shilpa Ray
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
| | - Daniel Ryan
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
| | - Shantoshini Dash
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
| | - Mrutyunjay Suar
- School of Biotechnology, KIIT University, Bhubaneswar-751024, Odisha, India
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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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36
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Wang C, Xuan J, Cui Q, Feng Y. Resonance assignments of a VapC family toxin from Clostridium thermocellum. BIOMOLECULAR NMR ASSIGNMENTS 2016; 10:367-371. [PMID: 27386855 DOI: 10.1007/s12104-016-9702-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 07/02/2016] [Indexed: 06/06/2023]
Abstract
Toxin-antitoxin (TA) systems widely exist in bacterial plasmids, phages, and chromosomes and play important roles in growth persistence and host-pathogen interaction. Virulence associated protein BC (VapBC) family TAs are the most abundant TAs in bacteria and many pathogens contain a large number of vapBC loci in the genome which have been extensively studied. Clostridium thermocellum, a cellulolytic anaerobic gram-positive bacterium with promising applications in biofuel production, also contains a VapBC TA in the genome. Despite the structures of several VapBC family TAs have been determined, the toxin and anti-toxin components of C. thermocellum VapBC have very low sequence identity to the proteins in PDB. Therefore, the structure and functional mechanism of this TA is largely unknown. Here we reported the NMR resonance assignments of the VapC toxin from C. thermocellum as a basis for further structural and functional studies.
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Affiliation(s)
- Chen Wang
- Department of Biological Science and Engineering, School of Chemical and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
- Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China
- CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China
| | - Jinsong Xuan
- Department of Biological Science and Engineering, School of Chemical and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China.
| | - Qiu Cui
- Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China
- CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China
| | - Yingang Feng
- Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China.
- CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101, China.
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Toxin-Antitoxin Modules Are Pliable Switches Activated by Multiple Protease Pathways. Toxins (Basel) 2016; 8:toxins8070214. [PMID: 27409636 PMCID: PMC4963847 DOI: 10.3390/toxins8070214] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 06/24/2016] [Accepted: 06/27/2016] [Indexed: 02/06/2023] Open
Abstract
Toxin-antitoxin (TA) modules are bacterial regulatory switches that facilitate conflicting outcomes for cells by promoting a pro-survival phenotypic adaptation and/or by directly mediating cell death, all through the toxin activity upon degradation of antitoxin. Intensive study has revealed specific details of TA module functions, but significant gaps remain about the molecular details of activation via antitoxin degradation used by different bacteria and in different environments. This review summarizes the current state of knowledge about the interaction of antitoxins with cellular proteases Lon and ClpP to mediate TA module activation. An understanding of these processes can answer long-standing questions regarding stochastic versus specific activation of TA modules and provide insight into the potential for manipulation of TA modules to alter bacterial growth.
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Karlowicz A, Wegrzyn K, Dubiel A, Ropelewska M, Konieczny I. Proteolysis in plasmid DNA stable maintenance in bacterial cells. Plasmid 2016; 86:7-13. [PMID: 27252071 DOI: 10.1016/j.plasmid.2016.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/25/2016] [Accepted: 05/26/2016] [Indexed: 01/12/2023]
Abstract
Plasmids, as extrachromosomal genetic elements, need to work out strategies that promote independent replication and stable maintenance in host bacterial cells. Their maintenance depends on constant formation and dissociation of nucleoprotein complexes formed on plasmid DNA. Plasmid replication initiation proteins (Rep) form specific complexes on direct repeats (iterons) localized within the plasmid replication origin. Formation of these complexes along with a strict control of Rep protein cellular concentration, quaternary structure, and activity, is essential for plasmid maintenance. Another important mechanism for maintenance of low-copy-number plasmids are the toxin-antitoxin (TA) post-segregational killing (psk) systems, which prevent plasmid loss from the bacterial cell population. In this mini review we discuss the importance of nucleoprotein complex processing by energy-dependent host proteases in plasmid DNA replication and plasmid type II toxin-antitoxin psk systems, and draw attention to the elusive role of DNA in this process.
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Affiliation(s)
- Anna Karlowicz
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland
| | - Katarzyna Wegrzyn
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland
| | - Andrzej Dubiel
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland
| | - Malgorzata Ropelewska
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland
| | - Igor Konieczny
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gdansk, Poland.
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Coussens NP, Daines DA. Wake me when it's over - Bacterial toxin-antitoxin proteins and induced dormancy. Exp Biol Med (Maywood) 2016; 241:1332-42. [PMID: 27216598 DOI: 10.1177/1535370216651938] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Toxin-antitoxin systems are encoded by bacteria and archaea to enable an immediate response to environmental stresses, including antibiotics and the host immune response. During normal conditions, the antitoxin components prevent toxins from interfering with metabolism and arresting growth; however, toxin activation enables microbes to remain dormant through unfavorable conditions that might continue over millions of years. Intense investigations have revealed a multitude of mechanisms for both regulation and activation of toxin-antitoxin systems, which are abundant in pathogenic microorganisms. This minireview provides an overview of the current knowledge regarding type II toxin-antitoxin systems along with their clinical and environmental implications.
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Affiliation(s)
- Nathan P Coussens
- Division of Pre-Clinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD 20850, USA
| | - Dayle A Daines
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
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Fan X, Li Y, He R, Li Q, He W. Comparative analysis of prophage-like elements in Helicobacter sp. genomes. PeerJ 2016; 4:e2012. [PMID: 27169002 PMCID: PMC4860318 DOI: 10.7717/peerj.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 04/14/2016] [Indexed: 12/11/2022] Open
Abstract
Prophages are regarded as one of the factors underlying bacterial virulence, genomic diversification, and fitness, and are ubiquitous in bacterial genomes. Information on Helicobacter sp. prophages remains scarce. In this study, sixteen prophages were identified and analyzed in detail. Eight of them are described for the first time. Based on a comparative genomic analysis, these sixteen prophages can be classified into four different clusters. Phylogenetic relationships of Cluster A Helicobacter prophages were investigated. Furthermore, genomes of Helicobacter prophages from Clusters B, C, and D were analyzed. Interestingly, some putative antibiotic resistance proteins and virulence factors were associated with Helicobacter prophages.
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Affiliation(s)
- Xiangyu Fan
- School of Biological Science and Technology, University of Jinan , Jinan , China
| | - Yumei Li
- School of Biological Science and Technology, University of Jinan , Jinan , China
| | - Rong He
- School of Biological Science and Technology, University of Jinan , Jinan , China
| | - Qiang Li
- School of Biological Science and Technology, University of Jinan , Jinan , China
| | - Wenxing He
- School of Biological Science and Technology, University of Jinan , Jinan , China
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Savari M, Rostami S, Ekrami A, Bahador A. Characterization of Toxin-Antitoxin (TA) Systems in Pseudomonas aeruginosa Clinical Isolates in Iran. Jundishapur J Microbiol 2016; 9:e26627. [PMID: 27099681 PMCID: PMC4834025 DOI: 10.5812/jjm.26627] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 09/01/2015] [Accepted: 09/21/2015] [Indexed: 11/16/2022] Open
Abstract
Background: Pseudomonas aeruginosa is among the most problematic hospital and community-acquired pathogens. Toxin-antitoxin (TA) systems are maintenance regulatory systems in bacteria and have recently been considered new targets for antimicrobial therapy. The prevalence and transcription of these systems in clinical isolates are still unknown. Objectives: The aim of this study was to characterize three types of TA systems (parDE, relBE, and higBA) among P. aeruginosa clinical isolates. Materials and Methods: We typed our clinical isolates by ERIC-PCR (enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction) and BOX-PCR. We then investigated 174 P. aeruginosa clinical isolates from three hospitals in Ahvaz, Iran, for the presence of TA system genes, and determined whether these systems were encoded on chromosomes or plasmids by amplification of the flanking regions. Results: Our results showed that in the 174 P. aeruginosa isolates, relBE and higBA were universal, but parDE was less prevalent. Both of the flanking regions of the parDE genes in all positive isolates were amplified. The flanking regions of nearly all relBE genes were amplified. Amplification was observed for the downstream sequence of every higBA locus, as well as for the region upstream of higBA, except in 14 strains. Conclusions: Based on the presence of TA systems in the majority of P. aeruginosa isolates, these could be used as a novel target for antimicrobial therapy.
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Affiliation(s)
- Mohammad Savari
- Department of Microbiology, Medicine school, Tehran University of Medical Sciences, Tehran, IR Iran
| | - Soodabeh Rostami
- Infectious Disease and Tropical Medicine Research Center, Isfahan University of Medical Sciences, Isfahan, IR Iran
| | - Alireza Ekrami
- Department of Laboratory Medical Sciences, Faculty of Para Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran
| | - Abbas Bahador
- Department of Microbiology, Medicine school, Tehran University of Medical Sciences, Tehran, IR Iran
- Corresponding author: Abbas Bahador, Department of Microbiology, Medicine school, Tehran University of Medical Sciences, Tehran, IR Iran. Tel/Fax: +98-2188955810, E-mail:
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42
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A stable luciferase reporter plasmid for in vivo imaging in murine models of Staphylococcus aureus infections. Appl Microbiol Biotechnol 2015; 100:3197-206. [PMID: 26685857 DOI: 10.1007/s00253-015-7229-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/03/2015] [Accepted: 12/05/2015] [Indexed: 11/27/2022]
Abstract
In vivo imaging of bioluminescent bacteria permits their visualization in infected mice, allowing spatial and temporal evaluation of infection progression. Most available bioluminescent strains were obtained by integration of the luciferase genes into the bacterial chromosome, a challenging and time-consuming approach. Recently, episomal plasmids were used, which were introduced in bacteria and expressed all genes required for bioluminescence emission. However, the plasmid was progressively lost in vitro and in vivo, if bacteria were not maintained under antibiotic selective pressure. Increased stability could be obtained inserting into the plasmid backbone sequences that assured plasmid partition between daughter bacterial cells, or caused death of bacteria that had lost the plasmid. So far, no detailed analysis was performed of either plasmid stability in vivo or contribution of different stabilizing sequence types. Here we report the construction of a plasmid, which includes the Photorhabdus luminescens lux cassette expressed under the control of a Staphylococcus aureus specific gene promoter, and toxin/antitoxin (T/A) and partition sequences (Par) conferring stability and transmissibility of the plasmid. Following infection of mice with S. aureus carrying this plasmid, we demonstrated that the promoter-lux fusion was functional in vivo, that the plasmid was retained by 70-100% of bacterial cells 7 days post-infection, and that both stabilizing sequence types were required to maximize plasmid retention. These data suggest that the plasmid can be a valuable tool to study gene expression and bacterial spread in small laboratory animals infected with S. aureus or possibly other Gram-positive human pathogens.
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Kojima KK, Kobayashi I. Transmission of the PabI family of restriction DNA glycosylase genes: mobility and long-term inheritance. BMC Genomics 2015; 16:817. [PMID: 26481899 PMCID: PMC4615327 DOI: 10.1186/s12864-015-2021-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/07/2015] [Indexed: 02/08/2023] Open
Abstract
Background R.PabI is an exceptional restriction enzyme that functions as a DNA glycosylase. The enzyme excises an unmethylated base from its recognition sequence to generate apurinic/apyrimidinic (AP) sites, and also displays AP lyase activity, cleaving the DNA backbone at the AP site to generate the 3’-phospho alpha, beta-unsaturated aldehyde end in addition to the 5’-phosphate end. The resulting ends are difficult to religate with DNA ligase. The enzyme was originally isolated in Pyrococcus, a hyperthermophilic archaeon, and additional homologs subsequently identified in the epsilon class of the Gram-negative bacterial phylum Proteobacteria, such as Helicobacter pylori. Results Systematic analysis of R.PabI homologs and their neighboring genes in sequenced genomes revealed co-occurrence of R.PabI with M.PabI homolog methyltransferase genes. R.PabI and M.PabI homolog genes are occasionally found at corresponding (orthologous) loci in different species, such as Helicobacter pylori, Helicobacter acinonychis and Helicobacter cetorum, indicating long-term maintenance of the gene pair. One R.PabI and M.PabI homolog gene pair is observed immediately after the GMP synthase gene in both Campylobacter and Helicobacter, representing orthologs beyond genera. The mobility of the PabI family of restriction-modification (RM) system between genomes is evident upon comparison of genomes of sibling strains/species. Analysis of R.PabI and M.PabI homologs in H. pylori revealed an insertion of integrative and conjugative elements (ICE), and replacement with a gene of unknown function that may specify a membrane-associated toxin (hrgC). In view of the similarity of HrgC with toxins in type I toxin-antitoxin systems, we addressed the biological significance of this substitution. Our data indicate that replacement with hrgC occurred in the common ancestor of hspAmerind and hspEAsia. Subsequently, H. pylori with and without hrgC were intermixed at this locus, leading to complex distribution of hrgC in East Asia and the Americas. In Malaysia, hrgC was horizontally transferred from hspEAsia to hpAsia2 strains. Conclusions The PabI family of RM system behaves as a mobile, selfish genetic element, similar to the other families of Type II RM systems. Our analysis additionally revealed some cases of long-term inheritance. The distribution of the hrgC gene replacing the PabI family in the subpopulations of H. pylori, hspAmerind, hspEAsia and hpAsia2, corresponds to the two human migration events, one from East Asia to Americas and the other from China to Malaysia. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2021-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kenji K Kojima
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. .,Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. .,Genetic Information Research Institute, Los Altos, CA, 94022, USA.
| | - Ichizo Kobayashi
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. .,Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
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Lee IG, Lee SJ, Chae S, Lee KY, Kim JH, Lee BJ. Structural and functional studies of the Mycobacterium tuberculosis VapBC30 toxin-antitoxin system: implications for the design of novel antimicrobial peptides. Nucleic Acids Res 2015; 43:7624-37. [PMID: 26150422 PMCID: PMC4551927 DOI: 10.1093/nar/gkv689] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/24/2015] [Indexed: 12/21/2022] Open
Abstract
Toxin-antitoxin (TA) systems play important roles in bacterial physiology, such as multidrug tolerance, biofilm formation, and arrest of cellular growth under stress conditions. To develop novel antimicrobial agents against tuberculosis, we focused on VapBC systems, which encompass more than half of TA systems in Mycobacterium tuberculosis. Here, we report that theMycobacterium tuberculosis VapC30 toxin regulates cellular growth through both magnesium and manganese ion-dependent ribonuclease activity and is inhibited by the cognate VapB30 antitoxin. We also determined the 2.7-Å resolution crystal structure of the M. tuberculosis VapBC30 complex, which revealed a novel process of inactivation of the VapC30 toxin via swapped blocking by the VapB30 antitoxin. Our study on M. tuberculosis VapBC30 leads us to design two kinds of VapB30 and VapC30-based novel peptides which successfully disrupt the toxin-antitoxin complex and thus activate the ribonuclease activity of the VapC30 toxin. Our discovery herein possibly paves the way to treat tuberculosis for next generation.
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Affiliation(s)
- In-Gyun Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Sang Jae Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Susanna Chae
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Ki-Young Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Ji-Hun Kim
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Bong-Jin Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
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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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Die for the community: an overview of programmed cell death in bacteria. Cell Death Dis 2015; 6:e1609. [PMID: 25611384 PMCID: PMC4669768 DOI: 10.1038/cddis.2014.570] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 11/25/2014] [Accepted: 12/01/2014] [Indexed: 02/07/2023]
Abstract
Programmed cell death is a process known to have a crucial role in many aspects of eukaryotes physiology and is clearly essential to their life. As a consequence, the underlying molecular mechanisms have been extensively studied in eukaryotes and we now know that different signalling pathways leading to functionally and morphologically different forms of death exist in these organisms. Similarly, mono-cellular organism can activate signalling pathways leading to death of a number of cells within a colony. The reason why a single-cell organism would activate a program leading to its death is apparently counterintuitive and probably for this reason cell death in prokaryotes has received a lot less attention in the past years. However, as summarized in this review there are many reasons leading to prokaryotic cell death, for the benefit of the colony. Indeed, single-celled organism can greatly benefit from multicellular organization. Within this forms of organization, regulation of death becomes an important issue, contributing to important processes such as: stress response, development, genetic transformation, and biofilm formation.
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48
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Prozorov AA, Fedorova IA, Bekker OB, Danilenko VN. The virulence factors of Mycobacterium tuberculosis: Genetic control, new conceptions. RUSS J GENET+ 2014. [DOI: 10.1134/s1022795414080055] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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49
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Functional and structural analysis of HicA3-HicB3, a novel toxin-antitoxin system of Yersinia pestis. J Bacteriol 2014; 196:3712-23. [PMID: 25112480 DOI: 10.1128/jb.01932-14] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The mechanisms involved in the virulence of Yersinia pestis, the plague pathogen, are not fully understood. In previous research, we found that a Y. pestis mutant lacking the HicB3 (YPO3369) putative orphan antitoxin was attenuated for virulence in a murine model of bubonic plague. Toxin-antitoxin systems (TASs) are widespread in prokaryotes. Most bacterial species possess many TASs of several types. In type II TASs, the toxin protein is bound and neutralized by its cognate antitoxin protein in the cytoplasm. Here we identify the hicA3 gene encoding the toxin neutralized by HicB3 and show that HicA3-HicB3 constitutes a new functional type II TAS in Y. pestis. Using biochemical and mutagenesis-based approaches, we demonstrate that the HicA3 toxin is an RNase with a catalytic histidine residue. HicB3 has two functions: it sequesters and neutralizes HicA3 by blocking its active site, and it represses transcription of the hicA3B3 operon. Gel shift assays and reporter fusion experiments indicate that the HicB3 antitoxin binds to two operators in the hicA3B3 promoter region. We solved the X-ray structures of HicB3 and the HicA3-HicB3 complex; thus, we present the first crystal structure of a TA complex from the HicAB family. HicB3 forms a tetramer that can bind two HicA3 toxin molecules. HicA3 is monomeric and folds as a double-stranded-RNA-binding domain. The HicB3 N-terminal domain occludes the HicA3 active site, whereas its C-terminal domain folds as a ribbon-helix-helix DNA-binding motif.
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Ruangprasert A, Maehigashi T, Miles SJ, Giridharan N, Liu JX, Dunham CM. Mechanisms of toxin inhibition and transcriptional repression by Escherichia coli DinJ-YafQ. J Biol Chem 2014; 289:20559-69. [PMID: 24898247 PMCID: PMC4110269 DOI: 10.1074/jbc.m114.573006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 05/29/2014] [Indexed: 01/26/2023] Open
Abstract
Bacteria encounter environmental stresses that regulate a gene expression program required for adaptation and survival. Here, we report the 1.8-Å crystal structure of the Escherichia coli toxin-antitoxin complex YafQ-(DinJ)2-YafQ, a key component of the stress response. The antitoxin DinJ dimer adopts a ribbon-helix-helix motif required for transcriptional autorepression, and toxin YafQ contains a microbial RNase fold whose proposed active site is concealed by DinJ binding. Contrary to previous reports, our studies indicate that equivalent levels of transcriptional repression occur by direct interaction of either YafQ-(DinJ)2-YafQ or a DinJ dimer at a single inverted repeat of its recognition sequence that overlaps with the -10 promoter region. Surprisingly, multiple YafQ-(DinJ)2-YafQ complexes binding to the operator region do not appear to amplify the extent of repression. Our results suggest an alternative model for transcriptional autorepression that may be novel to DinJ-YafQ.
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Affiliation(s)
- Ajchareeya Ruangprasert
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Tatsuya Maehigashi
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stacey J Miles
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Nisha Giridharan
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Julie X Liu
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Christine M Dunham
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
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