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Adolph C, Cheung CY, McNeil MB, Jowsey WJ, Williams ZC, Hards K, Harold LK, Aboelela A, Bujaroski RS, Buckley BJ, Tyndall JDA, Li Z, Langer JD, Preiss L, Meier T, Steyn AJC, Rhee KY, Berney M, Kelso MJ, Cook GM. A dual-targeting succinate dehydrogenase and F 1F o-ATP synthase inhibitor rapidly sterilizes replicating and non-replicating Mycobacterium tuberculosis. Cell Chem Biol 2024; 31:683-698.e7. [PMID: 38151019 DOI: 10.1016/j.chembiol.2023.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 09/13/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023]
Abstract
Mycobacterial bioenergetics is a validated target space for antitubercular drug development. Here, we identify BB2-50F, a 6-substituted 5-(N,N-hexamethylene)amiloride derivative as a potent, multi-targeting bioenergetic inhibitor of Mycobacterium tuberculosis. We show that BB2-50F rapidly sterilizes both replicating and non-replicating cultures of M. tuberculosis and synergizes with several tuberculosis drugs. Target identification experiments, supported by docking studies, showed that BB2-50F targets the membrane-embedded c-ring of the F1Fo-ATP synthase and the catalytic subunit (substrate-binding site) of succinate dehydrogenase. Biochemical assays and metabolomic profiling showed that BB2-50F inhibits succinate oxidation, decreases the activity of the tricarboxylic acid (TCA) cycle, and results in succinate secretion from M. tuberculosis. Moreover, we show that the lethality of BB2-50F under aerobic conditions involves the accumulation of reactive oxygen species. Overall, this study identifies BB2-50F as an effective inhibitor of M. tuberculosis and highlights that targeting multiple components of the mycobacterial respiratory chain can produce fast-acting antimicrobials.
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Affiliation(s)
- Cara Adolph
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
| | - Chen-Yi Cheung
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Matthew B McNeil
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
| | - William J Jowsey
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
| | - Zoe C Williams
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Kiel Hards
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Liam K Harold
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Ashraf Aboelela
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Richard S Bujaroski
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Benjamin J Buckley
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Joel D A Tyndall
- School of Pharmacy, University of Otago, Dunedin 9054, New Zealand
| | - Zhengqiu Li
- School of Pharmacy, Jinan University, Guangzhou, China
| | - Julian D Langer
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Laura Preiss
- Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Thomas Meier
- Department of Life Sciences, Imperial College London, Exhibition Road, London SW7 2AZ, UK; Private University in the Principality of Liechtenstein, Triesen, Liechtenstein
| | - Adrie J C Steyn
- Africa Health Research Institute, University of KwaZulu Natal, Durban, KwaZulu, Natal, South Africa; Department of Microbiology, Centers for AIDs Research and Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Kyu Y Rhee
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY 14853, USA; Division of Infectious Diseases, Department of Medicine, Weill Cornell Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Michael Berney
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Michael J Kelso
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Gregory M Cook
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1042, New Zealand.
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Laws GA, Harold LK, Tagg JR, Hale JDF. Interferon Gamma Response in Human Saliva Following Exposure to the Oral Probiotic Streptococcus salivarius BLIS K12. Probiotics Antimicrob Proteins 2024; 16:93-98. [PMID: 36477439 DOI: 10.1007/s12602-022-10010-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2022] [Indexed: 12/12/2022]
Abstract
Streptococcus salivarius BLIS K12 is a probiotic strain developed for application to the oral cavity. The strain was originally characterised for its in vitro antibacterial activity against the prominent oral pathogen Streptococcus pyogenes. More recent research has expanded its applications to include reducing halitosis, preventing otitis media and protecting against virus infections of the respiratory tract. A potential mechanism for this anti-viral activity could be the stimulation of salivary interferon gamma (IFN-γ) production in the oral cavity. The aim of this study was to investigate whether the ingestion of and oral cavity colonisation by S. salivarius BLIS K12 is associated with enhancement of IFN-γ levels in saliva. Application of ELISA demonstrated that consumption of S. salivarius BLIS K12 effected an increase in salivary IFN-γ, and this response was more consistent with use of viable cells than following ingestion of heat-killed S. salivarius BLIS K12. Interestingly, those subjects who more successfully colonised with S. salivarius BLIS K12 did not experience a relatively larger increase in their IFN-γ levels, indicating that the observed IFN-γ response occurs independently of colonisation efficacy. In summary, the consumption of S. salivarius BLIS K12 increases salivary levels of IFN-γ, an effect that may contribute to protection of the host against certain virus infections.
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Affiliation(s)
- Gemma A Laws
- Blis Technologies, 81 Glasgow St, South Dunedin, 9012, New Zealand
| | - Liam K Harold
- Blis Technologies, 81 Glasgow St, South Dunedin, 9012, New Zealand
| | - John R Tagg
- Blis Technologies, 81 Glasgow St, South Dunedin, 9012, New Zealand
| | - John D F Hale
- Blis Technologies, 81 Glasgow St, South Dunedin, 9012, New Zealand.
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3
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Tagg JR, Harold LK, Jain R, Hale JDF. Beneficial modulation of human health in the oral cavity and beyond using bacteriocin-like inhibitory substance-producing streptococcal probiotics. Front Microbiol 2023; 14:1161155. [PMID: 37056747 PMCID: PMC10086258 DOI: 10.3389/fmicb.2023.1161155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
The human oral cavity contains a diversity of microbial habitats that have been adopted and adapted to as homeland by an amazingly heterogeneous population of microorganisms collectively referred to as the oral microbiota. These microbes generally co-habit in harmonious homeostasis. However, under conditions of imposed stress, as with changes to the host’s physiology or nutritional status, or as a response to foreign microbial or antimicrobial incursions, some components of the oral “microbiome” (viz. the in situ microbiota) may enter a dysbiotic state. This microbiome dysbiosis can manifest in a variety of guises including streptococcal sore throats, dental caries, oral thrush, halitosis and periodontal disease. Most of the strategies currently available for the management or treatment of microbial diseases of the oral cavity focus on the repetitive “broad sweep” and short-term culling of oral microbe populations, hopefully including the perceived principal pathogens. Both physical and chemical techniques are used. However, the application of more focused approaches to the harnessing or elimination of key oral cavity pathogens is now feasible through the use of probiotic strains that are naturally adapted for oral cavity colonization and also are equipped to produce anti-competitor molecules such as the bacteriocins and bacteriocin-like inhibitory substances (viz BLIS). Some of these probiotics are capable of suppressing the proliferation of a variety of recognized microbial pathogens of the human mouth, thereby assisting with the restoration of oral microbiome homeostasis. BLIS K12 and BLIS M18, the progenitors of the BLIS-producing oral probiotics, are members of the human oral cavity commensal species Streptococcus salivarius. More recently however, a number of other streptococcal and some non-streptococcal candidate oral probiotics have also been promoted. What is becoming increasingly apparent is that the future for oral probiotic applications will probably extend well beyond the attempted limitation of the direct pathological consequences of oral microbiome dysbiosis to also encompass a plethora of systemic diseases and disorders of the human host. The background to and the evolving prospects for the beneficial modulation of the oral microbiome via the application of BLIS-producing S. salivarius probiotics comprises the principal focus of the present review.
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Harold LK, Jinich A, Hards K, Cordeiro A, Keighley LM, Cross A, McNeil MB, Rhee K, Cook GM. Deciphering functional redundancy and energetics of malate oxidation in mycobacteria. J Biol Chem 2022; 298:101859. [PMID: 35337802 PMCID: PMC9062433 DOI: 10.1016/j.jbc.2022.101859] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 03/20/2022] [Accepted: 03/21/2022] [Indexed: 02/07/2023] Open
Abstract
Oxidation of malate to oxaloacetate, catalyzed by either malate dehydrogenase (Mdh) or malate quinone oxidoreductase (Mqo), is a critical step of the tricarboxylic acid cycle. Both Mqo and Mdh are found in most bacterial genomes, but the level of functional redundancy between these enzymes remains unclear. A bioinformatic survey revealed that Mqo was not as widespread as Mdh in bacteria but that it was highly conserved in mycobacteria. We therefore used mycobacteria as a model genera to study the functional role(s) of Mqo and its redundancy with Mdh. We deleted mqo from the environmental saprophyte Mycobacterium smegmatis, which lacks Mdh, and found that Mqo was essential for growth on nonfermentable carbon sources. On fermentable carbon sources, the Δmqo mutant exhibited delayed growth and lowered oxygen consumption and secreted malate and fumarate as terminal end products. Furthermore, heterologous expression of Mdh from the pathogenic species Mycobacterium tuberculosis shortened the delayed growth on fermentable carbon sources and restored growth on nonfermentable carbon sources at a reduced growth rate. In M. tuberculosis, CRISPR interference of either mdh or mqo expression resulted in a slower growth rate compared to controls, which was further inhibited when both genes were knocked down simultaneously. These data reveal that exergonic Mqo activity powers mycobacterial growth under nonenergy limiting conditions and that endergonic Mdh activity complements Mqo activity, but at an energetic cost for mycobacterial growth. We propose Mdh is maintained in slow-growing mycobacterial pathogens for use under conditions such as hypoxia that require reductive tricarboxylic acid cycle activity.
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Affiliation(s)
- Liam K Harold
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand.
| | - Adrian Jinich
- Division of Infectious Diseases, Weill Department of Medicine, Weill Cornell Medical College, New York, New York, USA
| | - Kiel Hards
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand
| | - Alexandra Cordeiro
- Division of Infectious Diseases, Weill Department of Medicine, Weill Cornell Medical College, New York, New York, USA
| | - Laura M Keighley
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Alec Cross
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Matthew B McNeil
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand
| | - Kyu Rhee
- Division of Infectious Diseases, Weill Department of Medicine, Weill Cornell Medical College, New York, New York, USA
| | - Gregory M Cook
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand.
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5
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Hards K, Cheung CY, Waller N, Adolph C, Keighley L, Tee ZS, Harold LK, Menorca A, Bujaroski RS, Buckley BJ, Tyndall JDA, McNeil MB, Rhee KY, Opel-Reading HK, Krause K, Preiss L, Langer JD, Meier T, Hasenoehrl EJ, Berney M, Kelso MJ, Cook GM. An amiloride derivative is active against the F 1F o-ATP synthase and cytochrome bd oxidase of Mycobacterium tuberculosis. Commun Biol 2022; 5:166. [PMID: 35210534 PMCID: PMC8873251 DOI: 10.1038/s42003-022-03110-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 02/03/2022] [Indexed: 12/15/2022] Open
Abstract
Increasing antimicrobial resistance compels the search for next-generation inhibitors with differing or multiple molecular targets. In this regard, energy conservation in Mycobacterium tuberculosis has been clinically validated as a promising new drug target for combatting drug-resistant strains of M. tuberculosis. Here, we show that HM2-16F, a 6-substituted derivative of the FDA-approved drug amiloride, is an anti-tubercular inhibitor with bactericidal properties comparable to the FDA-approved drug bedaquiline (BDQ; Sirturo®) and inhibits the growth of bedaquiline-resistant mutants. We show that HM2-16F weakly inhibits the F1Fo-ATP synthase, depletes ATP, and affects the entry of acetyl-CoA into the Krebs cycle. HM2-16F synergizes with the cytochrome bcc-aa3 oxidase inhibitor Q203 (Telacebec) and co-administration with Q203 sterilizes in vitro cultures in 14 days. Synergy with Q203 occurs via direct inhibition of the cytochrome bd oxidase by HM2-16F. This study shows that amiloride derivatives represent a promising discovery platform for targeting energy generation in drug-resistant tuberculosis. Derivatives of the FDA-approved drug, amiloride, can eliminate drug-resistant Mycobacterium tuberculosis in vitro by interfering with bacterial energy conservation.
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Affiliation(s)
- Kiel Hards
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Otago, Dunedin, New Zealand
| | - Chen-Yi Cheung
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Natalie Waller
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Cara Adolph
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Laura Keighley
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Zhi Shean Tee
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Liam K Harold
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Otago, Dunedin, New Zealand
| | - Ayana Menorca
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Richard S Bujaroski
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Benjamin J Buckley
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawarra Health and Medical Research Institute, Wollongong, Australia
| | | | - Matthew B McNeil
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Otago, Dunedin, New Zealand
| | - Kyu Y Rhee
- Weill Department of Medicine, Weill Cornell Medical College, New York, NY, USA
| | | | - Kurt Krause
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Otago, Dunedin, New Zealand
| | - Laura Preiss
- Department of Structural Biology, Max-Planck Institute of Biophysics, Frankfurt am Main, Germany.,Octapharma Biopharmaceuticals GmbH, Heidelberg, Germany
| | - Julian D Langer
- Department of Molecular Membrane Biology, Max-Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Thomas Meier
- Department of Life Sciences, Imperial College London, London, UK.,Private University in the Principality of Liechtenstein, Triesen, Liechtenstein
| | - Erik J Hasenoehrl
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Michael Berney
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Michael J Kelso
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia. .,Illawarra Health and Medical Research Institute, Wollongong, Australia.
| | - Gregory M Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand. .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Otago, Dunedin, New Zealand.
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6
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Ramsay JP, Bastholm TR, Verdonk CJ, Tambalo DD, Sullivan JT, Harold LK, Panganiban BA, Colombi E, Perry BJ, Jowsey W, Morris C, Hynes MF, Bond CS, Cameron ADS, Yost CK, Ronson CW. An epigenetic switch activates bacterial quorum sensing and horizontal transfer of an integrative and conjugative element. Nucleic Acids Res 2021; 50:975-988. [PMID: 34904658 PMCID: PMC8789080 DOI: 10.1093/nar/gkab1217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/23/2021] [Accepted: 11/25/2021] [Indexed: 11/13/2022] Open
Abstract
Horizontal transfer of the integrative and conjugative element ICEMlSymR7A converts non-symbiotic Mesorhizobium spp. into nitrogen-fixing legume symbionts. Here, we discover subpopulations of Mesorhizobium japonicum R7A become epigenetically primed for quorum-sensing (QS) and QS-activated horizontal transfer. Isolated populations in this state termed R7A* maintained these phenotypes in laboratory culture but did not transfer the R7A* state to recipients of ICEMlSymR7A following conjugation. We previously demonstrated ICEMlSymR7A transfer and QS are repressed by the antiactivator QseM in R7A populations and that the adjacently-coded DNA-binding protein QseC represses qseM transcription. Here RNA-sequencing revealed qseM expression was repressed in R7A* cells and that RNA antisense to qseC was abundant in R7A but not R7A*. Deletion of the antisense-qseC promoter converted cells into an R7A*-like state. An adjacently coded QseC2 protein bound two operator sites and repressed antisense-qseC transcription. Plasmid overexpression of QseC2 stimulated the R7A* state, which persisted following curing of this plasmid. The epigenetic maintenance of the R7A* state required ICEMlSymR7A-encoded copies of both qseC and qseC2. Therefore, QseC and QseC2, together with their DNA-binding sites and overlapping promoters, form a stable epigenetic switch that establishes binary control over qseM transcription and primes a subpopulation of R7A cells for QS and horizontal transfer.
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Affiliation(s)
- Joshua P Ramsay
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia
| | - Tahlia R Bastholm
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia
| | - Callum J Verdonk
- School of Molecular Sciences, University of Western Australia, Perth, WA 6009, Australia.,Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia
| | - Dinah D Tambalo
- Biology Department, University of Regina, Regina, SK S4S 0A2, Canada
| | - John T Sullivan
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Liam K Harold
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Beatrice A Panganiban
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia
| | - Elena Colombi
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia
| | - Benjamin J Perry
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - William Jowsey
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Calum Morris
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - Michael F Hynes
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 4V8, Canada
| | - Charles S Bond
- School of Molecular Sciences, University of Western Australia, Perth, WA 6009, Australia
| | | | | | - Clive W Ronson
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
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Safarian S, Opel-Reading HK, Wu D, Mehdipour AR, Hards K, Harold LK, Radloff M, Stewart I, Welsch S, Hummer G, Cook GM, Krause KL, Michel H. The cryo-EM structure of the bd oxidase from M. tuberculosis reveals a unique structural framework and enables rational drug design to combat TB. Nat Commun 2021; 12:5236. [PMID: 34475399 PMCID: PMC8413341 DOI: 10.1038/s41467-021-25537-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 08/17/2021] [Indexed: 02/07/2023] Open
Abstract
New drugs are urgently needed to combat the global TB epidemic. Targeting simultaneously multiple respiratory enzyme complexes of Mycobacterium tuberculosis is regarded as one of the most effective treatment options to shorten drug administration regimes, and reduce the opportunity for the emergence of drug resistance. During infection and proliferation, the cytochrome bd oxidase plays a crucial role for mycobacterial pathophysiology by maintaining aerobic respiration at limited oxygen concentrations. Here, we present the cryo-EM structure of the cytochrome bd oxidase from M. tuberculosis at 2.5 Å. In conjunction with atomistic molecular dynamics (MD) simulation studies we discovered a previously unknown MK-9-binding site, as well as a unique disulfide bond within the Q-loop domain that defines an inactive conformation of the canonical quinol oxidation site in Actinobacteria. Our detailed insights into the long-sought atomic framework of the cytochrome bd oxidase from M. tuberculosis will form the basis for the design of highly specific drugs to act on this enzyme.
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Affiliation(s)
- Schara Safarian
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt/Main, Germany.
| | | | - Di Wu
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt/Main, Germany
| | - Ahmad R Mehdipour
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt/Main, Germany
| | - Kiel Hards
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Liam K Harold
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Melanie Radloff
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt/Main, Germany
| | - Ian Stewart
- Department of Chemistry, University of Otago, Dunedin, New Zealand
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt/Main, Germany
- Institute of Biophysics, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - Gregory M Cook
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Kurt L Krause
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Hartmut Michel
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt/Main, Germany.
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8
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Grinter R, Ney B, Brammananth R, Barlow CK, Cordero PRF, Gillett DL, Izoré T, Cryle MJ, Harold LK, Cook GM, Taiaroa G, Williamson DA, Warden AC, Oakeshott JG, Taylor MC, Crellin PK, Jackson CJ, Schittenhelm RB, Coppel RL, Greening C. Cellular and Structural Basis of Synthesis of the Unique Intermediate Dehydro-F 420-0 in Mycobacteria. mSystems 2020; 5:e00389-20. [PMID: 32430409 PMCID: PMC7253369 DOI: 10.1128/msystems.00389-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 11/29/2022] Open
Abstract
F420 is a low-potential redox cofactor used by diverse bacteria and archaea. In mycobacteria, this cofactor has multiple roles, including adaptation to redox stress, cell wall biosynthesis, and activation of the clinical antitubercular prodrugs pretomanid and delamanid. A recent biochemical study proposed a revised biosynthesis pathway for F420 in mycobacteria; it was suggested that phosphoenolpyruvate served as a metabolic precursor for this pathway, rather than 2-phospholactate as long proposed, but these findings were subsequently challenged. In this work, we combined metabolomic, genetic, and structural analyses to resolve these discrepancies and determine the basis of F420 biosynthesis in mycobacterial cells. We show that, in whole cells of Mycobacterium smegmatis, phosphoenolpyruvate rather than 2-phospholactate stimulates F420 biosynthesis. Analysis of F420 biosynthesis intermediates present in M. smegmatis cells harboring genetic deletions at each step of the biosynthetic pathway confirmed that phosphoenolpyruvate is then used to produce the novel precursor compound dehydro-F420-0. To determine the structural basis of dehydro-F420-0 production, we solved high-resolution crystal structures of the enzyme responsible (FbiA) in apo-, substrate-, and product-bound forms. These data show the essential role of a single divalent cation in coordinating the catalytic precomplex of this enzyme and demonstrate that dehydro-F420-0 synthesis occurs through a direct substrate transfer mechanism. Together, these findings resolve the biosynthetic pathway of F420 in mycobacteria and have significant implications for understanding the emergence of antitubercular prodrug resistance.IMPORTANCE Mycobacteria are major environmental microorganisms and cause many significant diseases, including tuberculosis. Mycobacteria make an unusual vitamin-like compound, F420, and use it to both persist during stress and resist antibiotic treatment. Understanding how mycobacteria make F420 is important, as this process can be targeted to create new drugs to combat infections like tuberculosis. In this study, we show that mycobacteria make F420 in a way that is different from other bacteria. We studied the molecular machinery that mycobacteria use to make F420, determining the chemical mechanism for this process and identifying a novel chemical intermediate. These findings also have clinical relevance, given that two new prodrugs for tuberculosis treatment are activated by F420.
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Affiliation(s)
- Rhys Grinter
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Blair Ney
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- CSIRO Land & Water, Canberra, ACT, Australia
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Rajini Brammananth
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Christopher K Barlow
- Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
- Monash Proteomics & Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Paul R F Cordero
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - David L Gillett
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Thierry Izoré
- Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Max J Cryle
- Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Liam K Harold
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Gregory M Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - George Taiaroa
- Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Deborah A Williamson
- Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | | | | | | | - Paul K Crellin
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Colin J Jackson
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Ralf B Schittenhelm
- Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
- Monash Proteomics & Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Ross L Coppel
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Chris Greening
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
- Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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9
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Chong SMS, Manimekalai MSS, Sarathy JP, Williams ZC, Harold LK, Cook GM, Dick T, Pethe K, Bates RW, Grüber G. Antituberculosis Activity of the Antimalaria Cytochrome bcc Oxidase Inhibitor SCR0911. ACS Infect Dis 2020; 6:725-737. [PMID: 32092260 DOI: 10.1021/acsinfecdis.9b00408] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ability to respire and generate adenosine triphosphate (ATP) is essential for the physiology, persistence, and pathogenicity of Mycobacterium tuberculosis, which causes tuberculosis. By employing a lead repurposing strategy, the malarial cytochrome bc1 inhibitor SCR0911 was tested against mycobacteria. Docking studies were carried out to reveal potential binding and to understand the binding interactions with the target, cytochrome bcc. Whole-cell-based and in vitro assays demonstrated the potency of SCR0911 by inhibiting cell growth and ATP synthesis in both the fast- and slow-growing M. smegmatis and M. bovis bacillus Calmette-Guérin, respectively. The variety of biochemical assays and the use of a cytochrome bcc deficient mutant strain validated the cytochrome bcc oxidase as the direct target of the drug. The data demonstrate the broad-spectrum activity of SCR0911 and open the door for structure-activity relationship studies to improve the potency of new mycobacteria specific SCR0911 analogues.
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Affiliation(s)
- Shi Min Sherilyn Chong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
- School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Republic of Singapore
- Nanyang Institute of Technology in Health and Medicine, Interdisciplinary Graduate School, Nanyang Technological University, Singapore 637551, Republic of Singapore
| | | | - Jickky Palmae Sarathy
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 14 Medical Drive, Singapore 117599, Republic of Singapore
| | - Zoe C. Williams
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Liam K. Harold
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Gregory M. Cook
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Thomas Dick
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 14 Medical Drive, Singapore 117599, Republic of Singapore
- Center for Discovery and Innovation, Hackensack Meridian Health, 340 Kingsland Street Building 102, Nutley, New Jersey 07110, United States
| | - Kevin Pethe
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore
| | - Roderick W. Bates
- School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Republic of Singapore
| | - Gerhard Grüber
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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10
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Lee BM, Harold LK, Almeida DV, Afriat-Jurnou L, Aung HL, Forde BM, Hards K, Pidot SJ, Ahmed FH, Mohamed AE, Taylor MC, West NP, Stinear TP, Greening C, Beatson SA, Nuermberger EL, Cook GM, Jackson CJ. Predicting nitroimidazole antibiotic resistance mutations in Mycobacterium tuberculosis with protein engineering. PLoS Pathog 2020; 16:e1008287. [PMID: 32032366 PMCID: PMC7032734 DOI: 10.1371/journal.ppat.1008287] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 02/20/2020] [Accepted: 12/16/2019] [Indexed: 12/21/2022] Open
Abstract
Our inability to predict which mutations could result in antibiotic resistance has made it difficult to rapidly identify the emergence of resistance, identify pre-existing resistant populations, and manage our use of antibiotics to effectively treat patients and prevent or slow the spread of resistance. Here we investigated the potential for resistance against the new antitubercular nitroimidazole prodrugs pretomanid and delamanid to emerge in Mycobacterium tuberculosis, the causative agent of tuberculosis (TB). Deazaflavin-dependent nitroreductase (Ddn) is the only identified enzyme within M. tuberculosis that activates these prodrugs, via an F420H2-dependent reaction. We show that the native menaquinone-reductase activity of Ddn is essential for emergence from hypoxia, which suggests that for resistance to spread and pose a threat to human health, the native activity of Ddn must be at least partially retained. We tested 75 unique mutations, including all known sequence polymorphisms identified among ~15,000 sequenced M. tuberculosis genomes. Several mutations abolished pretomanid and delamanid activation in vitro, without causing complete loss of the native activity. We confirmed that a transmissible M. tuberculosis isolate from the hypervirulent Beijing family already possesses one such mutation and is resistant to pretomanid, before being exposed to the drug. Notably, delamanid was still effective against this strain, which is consistent with structural analysis that indicates delamanid and pretomanid bind to Ddn differently. We suggest that the mutations identified in this work be monitored for informed use of delamanid and pretomanid treatment and to slow the emergence of resistance.
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Affiliation(s)
- Brendon M. Lee
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Liam K. Harold
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Deepak V. Almeida
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Livnat Afriat-Jurnou
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
- MIGAL, Galilee Research Institute, Kiryat Shmona, Israel
- Faculty of Sciences and Technology, Tel-Hai Academic College, Upper Galilee, Israel
| | - Htin Lin Aung
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Brian M. Forde
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Kiel Hards
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Sacha J. Pidot
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Victoria, Australia
| | - F. Hafna Ahmed
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - A. Elaaf Mohamed
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Matthew C. Taylor
- Land and Water Flagship, The Commonwealth Scientific and Industrial Organisation, Canberra, Australian Capital Territory, Australia
| | - Nicholas P. West
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Timothy P. Stinear
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Victoria, Australia
| | - Chris Greening
- Land and Water Flagship, The Commonwealth Scientific and Industrial Organisation, Canberra, Australian Capital Territory, Australia
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Scott A. Beatson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Eric L. Nuermberger
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Gregory M. Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Colin J. Jackson
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
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11
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Hards K, Adolph C, Harold LK, McNeil MB, Cheung CY, Jinich A, Rhee KY, Cook GM. Two for the price of one: Attacking the energetic-metabolic hub of mycobacteria to produce new chemotherapeutic agents. Prog Biophys Mol Biol 2019; 152:35-44. [PMID: 31733221 DOI: 10.1016/j.pbiomolbio.2019.11.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 11/12/2019] [Indexed: 12/25/2022]
Abstract
Cellular bioenergetics is an area showing promise for the development of new antimicrobials, antimalarials and cancer therapy. Enzymes involved in central carbon metabolism and energy generation are essential mediators of bacterial physiology, persistence and pathogenicity, lending themselves natural interest for drug discovery. In particular, succinate and malate are two major focal points in both the central carbon metabolism and the respiratory chain of Mycobacterium tuberculosis. Both serve as direct links between the citric acid cycle and the respiratory chain due to the quinone-linked reactions of succinate dehydrogenase, fumarate reductase and malate:quinone oxidoreductase. Inhibitors against these enzymes therefore hold the promise of disrupting two distinct, but essential, cellular processes at the same time. In this review, we discuss the roles and unique adaptations of these enzymes and critically evaluate the role that future inhibitors of these complexes could play in the bioenergetics target space.
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Affiliation(s)
- Kiel Hards
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, 1042, Auckland, New Zealand.
| | - Cara Adolph
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand
| | - Liam K Harold
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, 1042, Auckland, New Zealand
| | - Matthew B McNeil
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, 1042, Auckland, New Zealand
| | - Chen-Yi Cheung
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand
| | - Adrian Jinich
- Division of Infectious Diseases, Weill Department of Medicine, Weill Cornell Medical College, New York, NY, 10065, USA
| | - Kyu Y Rhee
- Division of Infectious Diseases, Weill Department of Medicine, Weill Cornell Medical College, New York, NY, 10065, USA
| | - Gregory M Cook
- Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, 9054, Dunedin, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, 1042, Auckland, New Zealand.
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12
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Harold LK, Antoney J, Ahmed FH, Hards K, Carr PD, Rapson T, Greening C, Jackson CJ, Cook GM. FAD-sequestering proteins protect mycobacteria against hypoxic and oxidative stress. J Biol Chem 2018; 294:2903-2912. [PMID: 30567740 DOI: 10.1074/jbc.ra118.006237] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/14/2018] [Indexed: 12/13/2022] Open
Abstract
The ability to persist in the absence of growth triggered by low oxygen levels is a critical process for the survival of mycobacterial species in many environmental niches. MSMEG_5243 (fsq), a gene of unknown function in Mycobacterium smegmatis, is up-regulated in response to hypoxia and regulated by DosRDosS/DosT, an oxygen- and redox-sensing two-component system that is highly conserved in mycobacteria. In this communication, we demonstrate that MSMEG_5243 is a flavin-sequestering protein and henceforth refer to it as Fsq. Using an array of biochemical and structural analyses, we show that Fsq is a member of the diverse superfamily of flavin- and deazaflavin-dependent oxidoreductases (FDORs) and is widely distributed in mycobacterial species. We created a markerless deletion mutant of fsq and demonstrate that fsq is required for cell survival during hypoxia. Using fsq deletion and overexpression, we found that fsq enhances cellular resistance to hydrogen peroxide treatment. The X-ray crystal structure of Fsq, solved to 2.7 Å, revealed a homodimeric organization with FAD bound noncovalently. The Fsq structure also uncovered no potential substrate-binding cavities, as the FAD is fully enclosed, and electrochemical studies indicated that the Fsq:FAD complex is relatively inert and does not share common properties with electron-transfer proteins. Taken together, our results suggest that Fsq reduces the formation of reactive oxygen species (ROS) by sequestering free FAD during recovery from hypoxia, thereby protecting the cofactor from undergoing autoxidation to produce ROS. This finding represents a new paradigm in mycobacterial adaptation to hypoxia.
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Affiliation(s)
- Liam K Harold
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
| | - James Antoney
- Research School of Chemistry, The Australian National University, Canberra, Australia.,The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - F Hafna Ahmed
- Research School of Chemistry, The Australian National University, Canberra, Australia.,The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - Kiel Hards
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Paul D Carr
- Research School of Chemistry, The Australian National University, Canberra, Australia
| | - Trevor Rapson
- The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - Chris Greening
- The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and .,School of Biological Sciences, Monash University, Melbourne, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Canberra, Australia,
| | - Gregory M Cook
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand, .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
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