101
|
Bai G, Schaak DD, Smith EA, McDonough KA. Dysregulation of serine biosynthesis contributes to the growth defect of a Mycobacterium tuberculosis crp mutant. Mol Microbiol 2011; 82:180-98. [PMID: 21902733 DOI: 10.1111/j.1365-2958.2011.07806.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mycobacterium tuberculosis CRP(Mt), encoded by Rv3676 (crp), is a CRP-like transcription factor that binds with the serC-Rv0885 intergenic region. In the present study, we evaluated CRP(Mt) 's regulation of serC and Rv0885 in M. tuberculosis and M. bovis BCG, using site-specific mutagenesis, promoter fusions and reverse-transcriptase PCR (RT-PCR). The CRP(Mt) binding site was required for full expression of serC and Rv0885, and expression of both genes was reduced in M. tuberculosis and M. bovis BCG crp mutants. These data show that CRP(Mt) binding directly activates both serC and Rv0885 expression. M. tuberculosis serC restored the ability of an Escherichia coli serC mutant to grow in serine-dropout medium, demonstrating that M. tuberculosis serC encodes a phosphoserine aminotransferase. Serine supplementation, or overexpression of serC, accelerated the growth of M. tuberculosis and M. bovis BCG crp mutants in mycomedium, but not within macrophages. These results establish a role for CRP(Mt) in the regulation of amino acid biosynthesis, and show that reduced serine production contributes to the slow-growth phenotype of M. tuberculosis and M. bovis BCG crp mutants in vitro. Restoration of serine biosynthesis by serC expression will facilitate identification of additional CRP(Mt)-regulated factors required by M. tuberculosis during macrophage and host infection.
Collapse
Affiliation(s)
- Guangchun Bai
- Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, PO Box 22002, Albany, NY 12201-2002, USA
| | | | | | | |
Collapse
|
102
|
Holsclaw CM, Muse WB, Carroll KS, Leary JA. Mass Spectrometric Analysis of Mycothiol levels in Wild-Type and Mycothiol Disulfide Reductase Mutant Mycobacterium smegmatis. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2011; 305:151-156. [PMID: 21857792 PMCID: PMC3156591 DOI: 10.1016/j.ijms.2010.10.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Mycothiol (MSH), the primary low-molecular weight thiol produced in mycobacteria, acts to protect the cell from oxidative stress and to maintain redox homeostasis, notably in the pathogenic Mycobacterium tuberculosis in the course of human infection. The mycothiol disulfide reductase (Mtr) enzyme reduces the oxidized form of mycothiol, mycothione (MSSM), back to MSH, however its role in bacterial viability is not clear. In this study, we sought to determine the MSH levels of wild-type (WT) and Mtr mutant mycobacteria during oxidative stress. We describe a rapid method for the relative quantification of MSH using high-sensitivity mass spectrometry (MS) with selected ion monitoring (SIM). This method uses only minimal sample cleanup, and does not require advanced chromatographic equipment or fluorescent compounds. MSH levels decreased in the Mtr mutant only upon treatment with peroxide, and the results were consistent between our method and previously-described thiol quantification methods. Our results indicate that our MS-based method is a useful, high-throughput alternative tool for the quantification of MSH from mycobacteria.
Collapse
Affiliation(s)
- Cynthia M. Holsclaw
- Department of Molecular and Cell Biology, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
| | - Wilson B. Muse
- Life Sciences Institute, 210 Washtenaw Avenue, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Kate S. Carroll
- Life Sciences Institute, 210 Washtenaw Avenue, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Julie A. Leary
- Department of Molecular and Cell Biology, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
| |
Collapse
|
103
|
Abstract
Mycobacterium tuberculosis (Mtb) has evolved into a highly successful human pathogen. It deftly subverts the bactericidal mechanisms of alveolar macrophages, ultimately inducing granuloma formation and establishing long-term residence in the host. These hallmarks of Mtb infection are facilitated by the metabolic adaptation of the pathogen to its surrounding environment and the biosynthesis of molecules that mediate its interactions with host immune cells. The sulfate assimilation pathway of Mtb produces a number of sulfur-containing metabolites with important contributions to pathogenesis and survival. This pathway is regulated by diverse environmental cues and regulatory proteins that mediate sulfur transactions in the cell. Here, we discuss the transcriptional and biochemical mechanisms of sulfur metabolism regulation in Mtb and potential small molecule regulators of the sulfate assimilation pathway that are collectively poised to aid this intracellular pathogen in its expert manipulation of the host. From this global analysis, we have identified a subset of sulfur-metabolizing enzymes that are sensitive to multiple regulatory cues and may be strong candidates for therapeutic intervention.
Collapse
Affiliation(s)
- Stavroula K. Hatzios
- Department of Chemistry, University of California, Berkeley, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California, United States of America
| | - Carolyn R. Bertozzi
- Department of Chemistry, University of California, Berkeley, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California, United States of America
- * E-mail:
| |
Collapse
|
104
|
Examining the basis of isoniazid tolerance in nonreplicating Mycobacterium tuberculosis using transcriptional profiling. Future Med Chem 2011; 2:1371-83. [PMID: 21426023 DOI: 10.4155/fmc.10.219] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Understanding how growth state influences Mycobacterium tuberculosis responses to antibiotic exposure provides a window into drug action during patient chemotherapy. In this article, we describe the transcriptional programs mediated by isoniazid (INH) during the transition from log-phase to nonreplicating bacilli, from INH-sensitive to INH-tolerant bacilli respectively, using the Wayne model. RESULTS INH treatment did not elicit a transcriptional response from nonreplicating bacteria under microarophilic conditions (NRP2), unlike the induction of a robust and well-characterized INH signature in log-phase bacilli. CONCLUSION The differential regulation (between drug-free NRP2 and log-phase bacilli) of genes directly implicated in INH resistance could not account for the abrogation of INH killing in nongrowing bacilli. Thus, factors affecting the requirement for mycolic acids and the redox status of bacilli are likely responsible for the reduction in INH efficacy. We speculate on additional mechanisms revealed by transcriptome analysis that might account for INH tolerance.
Collapse
|
105
|
Abstract
Bacillithiol (BSH), the α-anomeric glycoside of l-cysteinyl-d-glucosamine with l-malic acid, plays a dominant role in the cytosolic thiol redox chemistry of the low guanine and cytosine (GC) Gram-positive bacteria (phylum Firmicutes). BSH is functionally analogous to glutathione (GSH) but differs sufficiently in chemical structure that cells have evolved a distinct set of enzymes that use BSH as cofactor. BSH was discovered in Bacillus subtilis as a mixed disulfide with the redox-sensing repressor OhrR and in B. anthracis by biochemical analysis of pools of labeled thiols. The structure of BSH was determined after purification from Deinococcus radiodurans. Similarities in structure between BSH and mycothiol (MSH) facilitated the identification of biosynthetic genes for BSH in the model organism B. subtilis. Phylogenomic analyses have identified several candidate BSH-using or associated proteins, including a BSH reductase, glutaredoxin-like thiol-dependent oxidoreductases (bacilliredoxins), and a BSH-S-transferase (FosB) involved in resistance to the epoxide antibiotic fosfomycin. Preliminary results implicate BSH in cellular processes to maintain cytosolic redox balance and for adaptation to reactive oxygen, nitrogen, and electrophilic species. BSH also is predicted to chelate metals avidly, in part due to the appended malate moiety, although the implications of BSH for metal ion homeostasis have yet to be explored in detail.
Collapse
Affiliation(s)
- John D Helmann
- Department of Microbiology, Cornell University, Ithaca, New York 14853-8101, USA.
| |
Collapse
|
106
|
Polymorphisms in isoniazid and prothionamide resistance genes of the Mycobacterium tuberculosis complex. Antimicrob Agents Chemother 2011; 55:4408-11. [PMID: 21709103 DOI: 10.1128/aac.00555-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sequence analyses of 74 strains that encompassed major phylogenetic lineages of the Mycobacterium tuberculosis complex revealed 10 polymorphisms in mshA (Rv0486) and four polymorphisms in inhA (Rv1484) that were not responsible for isoniazid or prothionamide resistance. Instead, some of these mutations were phylogenetically informative. This genetic diversity must be taken into consideration for drug development and for the design of molecular tests for drug resistance.
Collapse
|
107
|
Coresistance to isoniazid and ethionamide maps to mycothiol biosynthetic genes in Mycobacterium bovis. Antimicrob Agents Chemother 2011; 55:4422-3. [PMID: 21709101 DOI: 10.1128/aac.00564-11] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A search to identify new mechanisms of isoniazid resistance in Mycobacterium bovis led to the isolation of mutants defective in mycothiol biosynthesis due to mutations in genes coding for the glycosyltransferase (mshA) or the cysteine ligase (mshC). These mutants showed low-level resistance to isoniazid but were highly resistant to ethionamide. This study further illustrates that mutations in mycothiol biosynthesis genes may contribute to isoniazid or ethionamide resistance across mycobacterial species.
Collapse
|
108
|
Evaluation of NTF1836 as an inhibitor of the mycothiol biosynthetic enzyme MshC in growing and non-replicating Mycobacterium tuberculosis. Bioorg Med Chem 2011; 19:3956-64. [PMID: 21665483 DOI: 10.1016/j.bmc.2011.05.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 05/11/2011] [Accepted: 05/17/2011] [Indexed: 11/21/2022]
Abstract
The mycothiol biosynthesis enzyme MshC catalyzes the ligation of cysteine with the pseudodisaccharide GlcN-Ins and has been identified as an essential enzyme in Mycobacterium tuberculosis. We now report on the development of NTF1836 as a micromolar inhibitor of MshC. Using commercial libraries, we conducted preliminary structure-activity relationship (SAR) studies on NTF1836. Based on this data, NTF1836 and five structurally related compounds showed similar activity towards clinical strains of M. tuberculosis. A gram scale synthesis was developed to provide ample material for biological studies. Using this material, we determined that inhibition of M. tuberculosis growth by NTF1836 was accompanied by a fall in mycothiol and an increase in GlcN-Ins consistent with the targeting of MshC. We also determined that NTF1836 kills non-replicating M. tuberculosis in the carbon starvation model of latency.
Collapse
|
109
|
Almeida Da Silva PEA, Palomino JC. Molecular basis and mechanisms of drug resistance in Mycobacterium tuberculosis: classical and new drugs. J Antimicrob Chemother 2011; 66:1417-30. [PMID: 21558086 DOI: 10.1093/jac/dkr173] [Citation(s) in RCA: 323] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Tuberculosis (TB) remains one of the leading public health problems worldwide. Declared as a global emergency in 1993 by the WHO, its control is hampered by the emergence of multidrug resistance (MDR), defined as resistance to at least rifampicin and isoniazid, two key drugs in the treatment of the disease. More recently, severe forms of drug resistance such as extensively drug-resistant (XDR) TB have been described. After the discovery of several drugs with anti-TB activity, multidrug therapy became fundamental for control of the disease. Major advances in molecular biology and the availability of new information generated after sequencing the genome of Mycobacterium tuberculosis increased our knowledge of the mechanisms of resistance to the main anti-TB drugs. Better knowledge of the mechanisms of drug resistance in TB and the molecular mechanisms involved will help us to improve current techniques for rapid detection and will also stimulate the exploration of new targets for drug activity and drug development. This article presents an updated review of the mechanisms and molecular basis of drug resistance in M. tuberculosis. It also comments on the several gaps in our current knowledge of the molecular mechanisms of drug resistance to the main classical and new anti-TB drugs and briefly discusses some implications of the development of drug resistance and fitness, transmission and pathogenicity of M. tuberculosis.
Collapse
|
110
|
Precise null deletion mutations of the mycothiol synthesis genes reveal their role in isoniazid and ethionamide resistance in Mycobacterium smegmatis. Antimicrob Agents Chemother 2011; 55:3133-9. [PMID: 21502624 DOI: 10.1128/aac.00020-11] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Mycothiol (MSH; AcCys-GlcN-Ins) is the glutathione analogue for mycobacteria. Mutations in MSH biosynthetic genes have been associated with resistance to isoniazid (INH) and ethionamide (ETH) in mycobacteria, but rigorous genetic studies are lacking, and those that have been conducted have yielded different results. In this study, we constructed independent null deletion mutants for all four genes involved in the MSH biosynthesis pathway (mshA, mshB, mshC, and mshD) in Mycobacterium smegmatis and made complementing constructs in integrating plasmids. The resulting set of strains was analyzed for levels of MSH, INH resistance, and ETH resistance. The mshA and mshC single deletion mutants were devoid of MSH production and resistant to INH, whereas the mshB deletion mutant produced decreased levels of MSH yet was sensitive to INH, suggesting that MSH biosynthesis is essential for INH susceptibility in M. smegmatis. Further evidence supporting this conclusion was generated by deleting the gene encoding the MSH S-conjugate amidase (mca) from the ΔmshB null mutant. This double mutant, ΔmshB Δmca, completely abolished MSH production and was resistant to INH. The mshA, mshC, and mshB single deletion mutants were also resistant to ETH, indicating that ETH resistance is modulated by the level of MSH in M. smegmatis. Surprisingly, the mshD deletion mutant lacked MSH production but was sensitive to both INH and ETH. The drug sensitivity was likely mediated by the compensated synthesis of N-formyl-Cys-GlcN-Ins, previously demonstrated to substitute for MSH in an mshD mutant of M. smegmatis. We conclude that MSH or N-formyl-Cys-GlcN-Ins is required for susceptibility to INH or ETH in M. smegmatis.
Collapse
|
111
|
Farhana A, Guidry L, Srivastava A, Singh A, Hondalus MK, Steyn AJC. Reductive stress in microbes: implications for understanding Mycobacterium tuberculosis disease and persistence. Adv Microb Physiol 2011; 57:43-117. [PMID: 21078441 DOI: 10.1016/b978-0-12-381045-8.00002-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mycobacterium tuberculosis (Mtb) is a remarkably successful pathogen that is capable of persisting in host tissues for decades without causing disease. Years after initial infection, the bacilli may resume growth, the outcome of which is active tuberculosis (TB). In order to establish infection, resist host defences and re-emerge, Mtb must coordinate its metabolism with the in vivo environmental conditions and nutrient availability within the primary site of infection, the lung. Maintaining metabolic homeostasis for an intracellular pathogen such as Mtb requires a carefully orchestrated series of oxidation-reduction reactions, which, if unbalanced, generate oxidative or reductive stress. The importance of oxidative stress in microbial pathogenesis has been appreciated and well studied over the past several decades. However, the role of its counterpart, reductive stress, has been largely ignored. Reductive stress is defined as an aberrant increase in reducing equivalents, the magnitude and identity of which is determined by host carbon source utilisation and influenced by the presence of host-generated gases (e.g. NO, CO, O(2) and CO(2)). This increased reductive power must be dissipated for bacterial survival. To recycle reducing equivalents, microbes have evolved unique electron 'sinks' that are distinct for their particular environmental niche. In this review, we describe the specific mechanisms that some microbes have evolved to dispel reductive stress. The intention of this review is to introduce the concept of reductive stress, in tuberculosis research in particular, in the hope of stimulating new avenues of investigation.
Collapse
Affiliation(s)
- Aisha Farhana
- Department of Microbiology, University of Alabama at Birmingham, AL, USA
| | | | | | | | | | | |
Collapse
|
112
|
Organic hydroperoxide resistance protein and ergothioneine compensate for loss of mycothiol in Mycobacterium smegmatis mutants. J Bacteriol 2011; 193:1981-90. [PMID: 21335456 DOI: 10.1128/jb.01402-10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The mshA::Tn5 mutant of Mycobacterium smegmatis does not produce mycothiol (MSH) and was found to markedly overproduce both ergothioneine and an ~15-kDa protein determined to be organic hydroperoxide resistance protein (Ohr). An mshA(G32D) mutant lacking MSH overproduced ergothioneine but not Ohr. Comparison of the mutant phenotypes with those of the wild-type strain indicated the following: Ohr protects against organic hydroperoxide toxicity, whereas ergothioneine does not; an additional MSH-dependent organic hydroperoxide peroxidase exists; and elevated isoniazid resistance in the mutant is associated with both Ohr and the absence of MSH. Purified Ohr showed high activity with linoleic acid hydroperoxide, indicating lipid hydroperoxides as the likely physiologic targets. The reduction of oxidized Ohr by NADH was shown to be catalyzed by lipoamide dehydrogenase and either lipoamide or DlaT (SucB). Since free lipoamide and lipoic acid levels were shown to be undetectable in M. smegmatis, the bound lipoyl residues of DlaT are the likely source of the physiological dithiol reductant for Ohr. The pattern of occurrence of homologs of Ohr among bacteria suggests that the ohr gene has been distributed by lateral transfer. The finding of multiple Ohr homologs with various sequence identities in some bacterial genomes indicates that there may be multiple physiologic targets for Ohr proteins.
Collapse
|
113
|
Molecular investigation of resistance to the antituberculous drug ethionamide in multidrug-resistant clinical isolates of Mycobacterium tuberculosis. Antimicrob Agents Chemother 2010; 55:355-60. [PMID: 20974869 DOI: 10.1128/aac.01030-10] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ethionamide (ETH) needs to be activated by the mono-oxygenase EthA, which is regulated by EthR, in order to be active against Mycobacterium tuberculosis. The activated drug targets the enzyme InhA, which is involved in cell wall biosynthesis. Resistance to ETH has been reported to result from various mechanisms, including mutations altering EthA/EthR, InhA and its promoter, the NADH dehydrogenase encoded by ndh, and the MshA enzyme, involved in mycothiol biosynthesis. We searched for such mutations in 87 clinical isolates: 47 ETH-resistant (ETH(r)) isolates, 24 ETH-susceptible (ETH(s)) isolates, and 16 isolates susceptible to ETH but displaying an intermediate proportion of resistant cells (ETH(Sip); defined as ≥1% but <10% resistant cells). In 81% (38/47) of the ETH(r) isolates, we found mutations in ethA, ethR, or inhA or its promoter, which mostly corresponded to new alterations in ethA and ethR. The 9 ETH(r) isolates without a mutation in these three genes (9/47, 19%) had no mutation in ndh, and a single isolate had a mutation in mshA. Of the 16 ETH(Sip) isolates, 7 had a mutation in ethA, 8 had no detectable mutation, and 1 had a mutation in mshA. Finally, of the 24 ETH(s) isolates, 23 had no mutation in the studied genes and 1 displayed a yet unknown mutation in the inhA promoter. Globally, the mechanism of resistance to ETH remained unknown for 19% of the ETH(r) isolates, highlighting the complexity of the mechanisms of ETH resistance in M. tuberculosis.
Collapse
|
114
|
Mycobacterium tuberculosis dihydrofolate reductase is not a target relevant to the antitubercular activity of isoniazid. Antimicrob Agents Chemother 2010; 54:3776-82. [PMID: 20566771 DOI: 10.1128/aac.00453-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis enoyl-acyl-ACP reductase (InhA) has been demonstrated to be the primary target of isoniazid (INH). Recently, it was postulated that M. tuberculosis dihydrofolate reductase (DHFR) is also a target of INH, based on the findings that a 4R-INH-NADP adduct synthesized from INH by a nonenzymatic approach showed strong inhibition of DHFR in vitro, and overexpression of M. tuberculosis dfrA in M. smegmatis conferred a 2-fold increase of resistance to INH. In the present study, a plasmid expressing M. tuberculosis dfrA was transformed into M. smegmatis and M. tuberculosis strains, respectively. The transformant strains were tested for their resistance to INH. Compared to the wild-type strains, overexpression of dfrA in M. smegmatis and M. tuberculosis did not confer any resistance to INH based on the MIC values. Similar negative results were obtained with 14 other overexpressed proteins that have been proposed to bind some form of INH-NAD(P) adduct. An Escherichia coli cell-based system was designed that allowed coexpression of both M. tuberculosis katG and dfrA genes in the presence of INH. The DHFR protein isolated from the experimental sample was not found bound with any INH-NADP adduct by enzyme inhibition assay and mass spectroscopic analysis. We also used whole-genome sequencing to determine whether polymorphisms in dfrA could be detected in six INH-resistant clinical isolates known to lack mutations in inhA and katG, but no such mutations were found. The dfrA overexpression experiments, together with the biochemical and sequencing studies, conclusively demonstrate that DHFR is not a target relevant to the antitubercular activity of INH.
Collapse
|
115
|
Kaur D, Guerin ME, Skovierová H, Brennan PJ, Jackson M. Chapter 2: Biogenesis of the cell wall and other glycoconjugates of Mycobacterium tuberculosis. ADVANCES IN APPLIED MICROBIOLOGY 2009; 69:23-78. [PMID: 19729090 DOI: 10.1016/s0065-2164(09)69002-x] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The re-emergence of tuberculosis in its present-day manifestations - single, multiple and extensive drug-resistant forms and as HIV-TB coinfections - has resulted in renewed research on fundamental questions such as the nature of the organism itself, Mycobacterium tuberculosis, the molecular basis of its pathogenesis, definition of the immunological response in animal models and humans, and development of new intervention strategies such as vaccines and drugs. Foremost among these developments has been the precise chemical definition of the complex and distinctive cell wall of M. tuberculosis, elucidation of the relevant pathways and underlying genetics responsible for the synthesis of the hallmark moieties of the tubercle bacillus such as the mycolic acid-arabinogalactan-peptidoglycan complex, the phthiocerol- and trehalose-containing effector lipids, the phosphatidylinositol-containing mannosides, lipomannosides and lipoarabinomannosides, major immunomodulators, and others. In this review, the laboratory personnel who have been the focal point of some to these developments review recent progress towards a comprehensive understanding of the basic physiology and functions of the cell wall of M. tuberculosis.
Collapse
Affiliation(s)
- Devinder Kaur
- Department of Microbiology, Immunology and Pathology, Mycobacteria Research Laboratories, Colorado State University, Fort Collins, CO 80523-1682, USA
| | | | | | | | | |
Collapse
|
116
|
Fan F, Vetting MW, Frantom PA, Blanchard JS. Structures and mechanisms of the mycothiol biosynthetic enzymes. Curr Opin Chem Biol 2009; 13:451-9. [PMID: 19699138 DOI: 10.1016/j.cbpa.2009.07.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 07/13/2009] [Accepted: 07/21/2009] [Indexed: 11/27/2022]
Abstract
In the past decade, the genes encoding all four enzymes responsible for the biosynthesis of mycothiol in Mycobacterium tuberculosis have been identified. Orthologs of each of these have been stably expressed and structurally characterized. The chemical mechanisms of all the four have also been studied. Because of the unique phylogenetic distribution of mycothiol, and the enzymes responsible for its biosynthesis, these enzymes represent interesting potential targets for antimycobacterial agents.
Collapse
Affiliation(s)
- Fan Fan
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | | | | | | |
Collapse
|
117
|
Abstract
Infections with Mycobacterium tuberculosis remain a major cause of disease and death in humans. Among the factors that contribute to M. tuberculosis's success as a pathogen is its ability to withstand potentially bactericidal host defences and to resist elimination by an activated immune system. This resistance to killing by the host is in part due to the low permeability of the mycobacterial cell envelope for many toxic molecules. In addition, it depends upon the detoxification of reactive oxygen and reactive nitrogen molecules produced by the host, the repair of the damage these molecules cause and maintenance of a neutral intrabacterial pH within acidic environments. The latter three mechanisms are the focus of this review.
Collapse
Affiliation(s)
- Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10065, USA.
| | | |
Collapse
|
118
|
Riccardi G, Pasca MR, Buroni S. Mycobacterium tuberculosis: drug resistance and future perspectives. Future Microbiol 2009; 4:597-614. [PMID: 19492969 DOI: 10.2217/fmb.09.20] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
TB is still a global health problem. The selection and spread of multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis strains represents a threat for global TB control. The reappearance of TB has driven an increased interest in understanding the mechanisms of drug action and drug resistance, which could provide a significant contribution in the development of new antimicrobials. In this article, the authors describe the mode of action and the resistance mechanisms of the principal first- and second-line antitubercular agents, namely isoniazid, ethionamide, ethambutol, D-cycloserine, rifamycins, fluoroquinolones, streptomycin, linezolid and pyrazinamide. A brief outline of the seven drugs in clinical development is reported, showing how the development of new TB drugs is still required.
Collapse
Affiliation(s)
- Giovanna Riccardi
- Department of Genetics & Microbiology, University of Pavia, Via Ferrata, 1 27100 Pavia, Italy.
| | | | | |
Collapse
|
119
|
Ioerger TR, Sacchettini JC. Structural genomics approach to drug discovery for Mycobacterium tuberculosis. Curr Opin Microbiol 2009; 12:318-25. [PMID: 19481971 DOI: 10.1016/j.mib.2009.04.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 04/27/2009] [Accepted: 04/27/2009] [Indexed: 11/28/2022]
Abstract
Structural genomics has become a powerful tool for studying microorganisms at the molecular level. Advances in technology have enabled the assembly of high-throughput pipelines that can be used to automate X-ray crystal structure determination for many proteins in the genome of a target organism. In this paper, we describe the methods used in the Tuberculosis Structural Genomics Consortium (TBSGC), ranging from protein production and crystallization to diffraction data collection and processing. The TBSGC is unique in that it uses biological importance as a primary criterion for target selection. The over-riding goal is to solve structures of proteins that may be potential drug targets, in order to support drug discovery efforts. We describe the crystal structures of several significant proteins in the M. tuberculosis genome that have been solved by the TBSGC over the past few years. We conclude by describing the high-throughput screening facilities and virtual screening facilities we have implemented for identifying small-molecule inhibitors of proteins whose structures have been solved.
Collapse
Affiliation(s)
- Thomas R Ioerger
- Department of Computer Science and Engineering, Texas A&M University, USA
| | | |
Collapse
|
120
|
Reynolds TB. Strategies for acquiring the phospholipid metabolite inositol in pathogenic bacteria, fungi and protozoa: making it and taking it. MICROBIOLOGY-SGM 2009; 155:1386-1396. [PMID: 19383710 PMCID: PMC2889408 DOI: 10.1099/mic.0.025718-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
myo-Inositol (inositol) is an essential nutrient that is used for building phosphatidylinositol and its derivatives in eukaryotes and even in some eubacteria such as the mycobacteria. As a consequence, fungal, protozoan and mycobacterial pathogens must be able to acquire inositol in order to proliferate and cause infection in their hosts. There are two primary mechanisms for acquiring inositol. One is to synthesize inositol from glucose 6-phosphate using two sequentially acting enzymes: inositol-3-phosphate synthase (Ino1p) converts glucose 6-phosphate to inositol 3-phosphate, and then inositol monophosphatase (IMPase) dephosphorylates inositol 3-phosphate to generate inositol. The other mechanism is to import inositol from the environment via inositol transporters. Inositol is readily abundant in the bloodstream of mammalian hosts, providing a source from which many pathogens could potentially import inositol. However, despite this abundance of inositol in the host, some pathogens such as the bacterium Mycobacterium tuberculosis and the protist parasite Trypanosoma brucei must be able to make inositol de novo in order to cause disease (M. tuberculosis) or even grow (T. brucei). Other pathogens such as the fungus Candida albicans are equally adept at causing disease by importing inositol or by making it de novo. The role of inositol acquisition in the biology and pathogenesis of the parasite Leishmania and the fungus Cryptococcus are being explored as well. The specific strategies used by these pathogens to acquire inositol while in the host are discussed in relation to each pathogen's unique metabolic requirements.
Collapse
Affiliation(s)
- Todd B Reynolds
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| |
Collapse
|
121
|
Alahari A, Alibaud L, Trivelli X, Gupta R, Lamichhane G, Reynolds RC, Bishai WR, Guerardel Y, Kremer L. Mycolic acid methyltransferase, MmaA4, is necessary for thiacetazone susceptibility inMycobacterium tuberculosis. Mol Microbiol 2009; 71:1263-77. [DOI: 10.1111/j.1365-2958.2009.06604.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
122
|
Jothivasan VK, Hamilton CJ. Mycothiol: synthesis, biosynthesis and biological functions of the major low molecular weight thiol in actinomycetes. Nat Prod Rep 2008; 25:1091-117. [PMID: 19030604 DOI: 10.1039/b616489g] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Actinomycetes produce mycothiol as their major low molecular weight thiol, which parallels the functions of glutathione found in prokaryotes and most Gram-negative bacteria. This review covers progress that has so far been made in terms of its distribution, biosynthesis and metabolic functions, as well as chemical syntheses of mycothiol and alternative substrates and inhibitors of mycothiol biosynthesis and mycothiol-dependent enzymes. 152 references are cited.
Collapse
|