Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thioredoxin system exists ubiquitously and participates in essential antioxidant and redox-regulation processes via a pair of conserved cysteine residues. In Mycobacterium tuberculosis, which lacks a genuine glutathione system, the thioredoxin system provides reducing equivalents inside the cell. The three-dimensional structure of thioredoxin reductase from M. tuberculosis has been determined at 3 A resolution. TLS refinement reveals a large libration axis, showing that NADPH-binding domain has large anisotropic disorder. The relative rotation of the NADPH domain with respect to the FAD domain is necessary for the thioredoxin reduction cycle, as it brings the spatially distant reacting sites close together. Normal-mode analysis carried out based on the elastic network model shows that the motion required to bring about the functional conformational change can be accounted for by motion along one single mode. TLS refinement and normal-mode analysis thus enhance our understanding of the associated conformational changes.
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PMID:Conformational flexibility of Mycobacterium tuberculosis thioredoxin reductase: crystal structure and normal-mode analysis. 1630 94

Protein disulfide-bond formation is poorly understood in the pathogenic bacterium Mycobacterium tuberculosis. Rv2874 is the M. tuberculosis homologue of the disulfide-bond electron transporter DsbD from Escherichia coli. Both proteins share a core central transmembrane domain and a C-terminal thioredoxin domain. To investigate the possible role of Rv2874 in disulfide-bond formation in M. tuberculosis, the C-terminal domain of Rv2874 has been cloned, expressed, purified and crystallized. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 109.7, b = 118.3, c = 122.9 A, and diffract to at least 3.0 A.
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PMID:Crystallization and preliminary diffraction studies of the C-terminal domain of the DipZ homologue from Mycobacterium tuberculosis. 1651 Oct 6

Thioredoxin peroxidase (TPx) has been reported to dominate the defense against H(2)O(2), other hydroperoxides, and peroxynitrite at the expense of thioredoxin (Trx) B and C in Mycobacterium tuberculosis (Mt). By homology, the enzyme has been classified as an atypical 2-C-peroxiredoxin (Prx), with Cys(60) as the "peroxidatic" cysteine (C(P)) forming a complex catalytic center with Cys(93) as the "resolving" cysteine (C(R)). Site-directed mutagenesis confirms Cys(60) to be C(P) and Cys(80) to be catalytically irrelevant. Replacing Cys(93) with serine leads to fast inactivation as seen by conventional activity determination, which is associated with oxidation of Cys(60) to a sulfinic acid derivative. However, in comparative stopped-flow analysis, WT-MtTPx and MtTPx C93S reduce peroxynitrite and react with TrxB and -C similarly fast. Reduction of pre-oxidized WT-MtTPx and MtTPx C93S by MtTrxB is demonstrated by monitoring the redox-dependent tryptophan fluorescence of MtTrxB. Furthermore, MtTPx C93S remains stable for 10 min at a morpholinosydnonimine hydrochloride-generated low flux of peroxynitrite and excess MtTrxB in a dihydrorhodamine oxidation model. Liquid chromatography-tandem mass spectrometry analysis revealed disulfide bridges between Cys(60) and Cys(93) and between Cys(60) and Cys(80) in oxidized WT-MtTPx. Reaction of pre-oxidized WT-MtTPx and MtTPx C93S with MtTrxB C34S or MtTrxC C40S yielded dead-end intermediates in which the Trx mutants are preferentially linked via disulfide bonds to Cys(60) and never to Cys(93) of the TPx. It is concluded that neither Cys(80) nor Cys(93) is required for the catalytic cycle of the peroxidase. Instead, MtTPx can react as a 1-C-Prx with Cys(60) being the site of attack for both the oxidizing and the reducing substrate. The role of Cys(93) is likely to conserve the oxidation equivalents of the sulfenic acid state of C(P) as a disulfide bond to prevent overoxidation of Cys(60) under a restricted supply of reducing substrate.
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PMID:The mycobacterial thioredoxin peroxidase can act as a one-cysteine peroxiredoxin. 1668 10

To evaluate the possibility of developing an effective subunit vaccine against Japanese encephalitis virus (JEV), mice were intraperitoneally immunized with either a neutralizing epitope (a 27-amino-acid region of the JEV E protein), or with a fusion protein between this region and a Mycobacterium tuberculosis hsp70. Both antigens were heterologously expressed in Escherichia coli as fusion proteins with thioredoxin. The fusion protein antigen elicited a higher titer of anti-thioredoxin-neutralizing epitope antibodies and a stronger proliferation of lymphocytes than did either the neutralizing epitope (irrespective of the presence of mineral oil as an adjuvant), or the conventional JEV SA14-14-2 vaccine. Assays of antibody isotype and IFN-gamma and IL-4 content in post-immunization serum showed that the fusion protein elicited a higher IgG2a titer and higher levels of IFN-gamma suggesting a potentiation of the Th1 immune response. The fusion protein antigen elicited a long-lived immune response, and the antibodies were able to neutralize JEV in vitro more strongly than did those elicited by the JEV SA14-14-2 vaccine. Immunization with the fusion protein generated both humoral and cellular immune responses to JEV, and the fusion protein appeared to be a more efficient protectant than the JEV SA14-14-2 vaccine.
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PMID:An hsp70 fusion protein vaccine potentiates the immune response against Japanese encephalitis virus. 1686 85

A thiol peroxidase (Tpx) from Mycobacterium tuberculosis was functionally analyzed. The enzyme shows NADPH-linked peroxidase activity using a thioredoxin-thioredoxin reductase system as electron donor, and anti-oxidant activity in a thiol-dependent metal-catalyzed oxidation system. It reduces H2O2, t-butyl hydroperoxide, and cumene hydroperoxide, and is inhibited by sulfhydryl reagents. Mutational studies revealed that the peroxidatic (Cys60) and resolving (Cys93) cysteine residues are critical amino acids for catalytic activity. The X-ray structure determined to a resolution of 1.75 A shows a thioredoxin fold similar to that of other peroxiredoxin family members. Superposition with structural homologues in oxidized and reduced forms indicates that the M. tuberculosis Tpx is a member of the atypical two-Cys peroxiredoxin family. In addition, the short distance that separates the Calpha atoms of Cys60 and Cys93 and the location of these cysteine residues in unstructured regions may indicate that the M. tuberculosis enzyme is oxidized, though the side-chain of Cys60 is poorly visible. It is solely in the reduced Streptococcus pneumoniae Tpx structure that both residues are part of two distinct helical segments. The M. tuberculosis Tpx is dimeric both in solution and in the crystal structure. Amino acid residues from both monomers delineate the active site pocket.
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PMID:Functional and structural characterization of a thiol peroxidase from Mycobacterium tuberculosis. 1688 37

APS reductase catalyzes the first committed step of reductive sulfate assimilation in pathogenic bacteria, including Mycobacterium tuberculosis, and is a promising target for drug development. We report the 2.7 A resolution crystal structure of Pseudomonas aeruginosa APS reductase in the thiosulfonate intermediate form of the catalytic cycle and with substrate bound. The structure, high-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry, and quantitative kinetic analysis, establish that the two chemically discrete steps of the overall reaction take place at distinct sites on the enzyme, mediated via conformational flexibility of the C-terminal 18 residues. The results address the mechanism by which sulfonucleotide reductases protect the covalent but labile enzyme-intermediate before release of sulfite by the protein cofactor thioredoxin. P. aeruginosa APS reductase contains an [4Fe-4S] cluster that is essential for catalysis. The structure reveals an unusual mode of cluster coordination by tandem cysteine residues and suggests how this arrangement might facilitate conformational change and cluster interaction with the substrate. Assimilatory 3'-phosphoadenosine 5'-phosphosulfate (PAPS) reductases are evolutionarily related, homologous enzymes that catalyze the same overall reaction, but do so in the absence of an [Fe-S] cluster. The APS reductase structure reveals adaptive use of a phosphate-binding loop for recognition of the APS O3' hydroxyl group, or the PAPS 3'-phosphate group.
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PMID:Substrate recognition, protein dynamics, and iron-sulfur cluster in Pseudomonas aeruginosa adenosine 5'-phosphosulfate reductase. 1701 Mar 73

Hydroperoxide metabolism in diverse pathogens is reviewed under consideration of involved enzymes as potential drug targets. The common denominator of the peroxidase systems of Trypanosoma, Leishmania, Plasmodium, and Mycobacterium species is the use of NAD(P)H to reduce hydroperoxides including peroxynitrite via a flavin-containing disulfide reductase, a thioredoxin (Trx)-related protein and a peroxidase that operates with thiol catalysis. In Plasmodium falciparum, thioredoxin- and glutathione dependent systems appear to be linked via glutaredoxin and plasmoredoxin to terminal thioredoxin peroxidases belonging to both, the peroxiredoxin (Prx) and glutathione peroxidase (GPx) family. In Mycobacterium tuberculosis, a catalase-type peroxidase is complemented by the typical 2-C-Prx AhpC that, in contrast to most bacteria, is reduced by TrxC, and an atypical 2-C-Prx reduced by TrxB or C. A most complex variation of the scheme is found in trypanosomatids, where the unique redox metabolite trypanothione reduces the thioredoxin-related tryparedoxin, which fuels Prx- and GPx-type peroxidases as well as ribonucleotide reductase. In Trypanosoma brucei and Leishmania donovani the system has been shown to be essential for viability and virulence by inversed genetics. It is concluded that optimum efficacy can be expected from inhibitors of the most upstream components of the redox cascades. For trypanosomatids attractive validated drug targets are trypanothione reductase and trypanothione synthetase; for mycobacteria thioredoxin reductase appears most appealing, while in Plasmodium simultaneous inhibition of both the thioredoxin and the glutathione pathway appears advisable to avoid mutual substitution in co-substrate supply to the peroxidases. Financial and organisational needs to translate the scientific progress into applicable drugs are discussed under consideration of the socio-economic impact of the addressed diseases.
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PMID:The thiol-based redox networks of pathogens: unexploited targets in the search for new drugs. 1701 68

ESI-FTICR MS was utilized to characterize a 4Fe-4S containing protein Mycobacterium tuberculosis APS reductase. This enzyme catalyzes the reduction of APS to sulfite and AMP with reducing equivalents from the protein cofactor, thioredoxin. Under nondenaturing conditions, a distribution of the apoprotein, a 2Fe-2S intermediate, and the 4Fe-4S holoprotein were observed. Accurate mass measurements indicated an oxidation state of +2 for the 4Fe-4S cluster, with no disulfide bond in the holoenzyme. Gas-phase stability of the 4Fe-4S cluster was investigated using both in-source and collision induced dissociation, which provided information regarding the relative gas-phase binding strength of iron towards protein ligands and inorganic sulfides. Noncovalent complexes of the holoprotein with several ligands, including APS, thioredoxin, and AMP, were also investigated. Calculated values of dissociation constants for the complexes indicate that AMP binds with a higher affinity to the enzyme intermediate than to the free enzyme. The implications of the binary and ternary complexes observed by gas-phase noncovalent interactions in the mechanism of APS reduction are discussed.
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PMID:Noncovalent complexes of APS reductase from M. tuberculosis: delineating a mechanistic model using ESI-FTICR MS. 1702 75

Mycobacterium tuberculosis is a facultative intracellular parasite of alveolar macrophages. M. tuberculosis is able to propagate in harsh environments within cells such as phagocytes, despite being exposed to reactive oxygen and nitrogen intermediates. The thioredoxin redox system is conserved across the phyla and has a well characterized role in resisting oxidative stress and influencing gene expression within prokaryotic and eukaryotic cells. M. tuberculosis thioredoxin (MtbTrx) has similar functions in redox homeostasis and it has recently been shown that alkyl hydroperoxidase C is efficiently reduced to its active form by MtbTrxC, supporting this notion. To address whether the MtbTrx has similar features to other thioredoxin structures and to examine the opportunities for designing drugs against this target, MtbTrxC has been crystallized and its structure determined to 1.3 A resolution. Unexpectedly, the structure demonstrates an interesting crystal packing in which five C-terminal residues from the MtbTrxC fold insert into a groove adjacent to the active site. A very similar interaction is observed in structures of human thioredoxins bound to peptides from the target proteins NF-kappaB and Ref-1.
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PMID:Structure of Mycobacterium tuberculosis thioredoxin C. 1713 80

WhiB family of protein is emerging as one of the most fascinating group and is implicated in stress response as well as pathogenesis via their involvement in diverse cellular processes. Surprisingly, available in vivo data indicate an organism specific physiological role for each of these proteins. The WhiB proteins have four conserved cysteine residues where two of them are present in a C-X-X-C motif. In thioredoxins and similar proteins, this motif works as an active site and confers thiol-disulfide oxidoreductase activity to the protein. The recombinant WhiB1/Rv3219 was purified in a single step from Escherichia coli using Ni(2+)-NTA affinity chromatography and was found to exist as a homodimer. Mass spectrometry of WhiB1 shows that the four cysteine residues form two intramolecular disulfide bonds. Using intrinsic tryptophan fluorescence as a measure of redox state, the redox potential of WhiB1 was calculated as -236+/-2mV, which corresponds to the redox potential of many cytoplasmic thioredoxin-like proteins. WhiB1 catalyzed the reduction of insulin disulfide thus clearly demonstrating that it functions as a protein disulfide reductase. Present study for the first time suggests that WhiB1 may be a part of the redox network of Mycobacterium tuberculosis through its involvement in thiol-disulfide exchange with other cellular proteins.
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PMID:Characterization of Mycobacterium tuberculosis WhiB1/Rv3219 as a protein disulfide reductase. 1715 31


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