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)

Although many bacterial pathogens use specialized secretion systems for virulence, no such systems have been described for Mycobacterium tuberculosis, a major pathogen of humans that proliferates in host macrophages. In a screen to identify genes required for virulence of M. tuberculosis, we have discovered three components and two substrates of the first Sec-independent secretion pathway described in M. tuberculosis, which we designate the Snm pathway. Here we demonstrate that the proteins Snm1, -2, and -4 are required for the secretion of ESAT-6 and CFP-10, small proteins previously identified as major T cell antigens. Snm2, a member of the AAA ATPase family, interacts with substrates and with Snm1, another AAA ATPase. We show that M. tuberculosis mutants lacking either the Snm system or these substrates exhibit defects in bacterial growth during the acute phase of a mouse infection and are attenuated for virulence. Strikingly, snm mutants fail to replicate in cultured macrophages and to inhibit macrophage inflammatory responses, two well established activities of wild-type M. tuberculosis bacilli. Thus, the Snm secretion pathway works to subvert normal macrophage responses and is a major determinant of M. tuberculosis virulence.
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PMID:Acute infection and macrophage subversion by Mycobacterium tuberculosis require a specialized secretion system. 1455 36

Microbial HSP70 (heat-shock protein 70) consists of three functionally distinct domains: an N-terminal 44 kDa ATPase portion (amino acids 1-358), followed by an 18 kDa peptide-binding domain (amino acids 359-494) and a C-terminal 10 kDa fragment (amino acids 495-609). Immunological functions of these three different domains in stimulating monocytes and dendritic cells have not been fully defined. However, the C-terminal portion (amino acids 359-610) stimulates the production of CC chemokines, IL-12 (interleukin-12), TNFalpha(tumour necrosis factor alpha), NO and maturation of dendritic cells and also functions as an adjuvant in the induction of immune responses. In contrast, the ATPase domain of microbial HSP70 mostly lacks these functions. Since the receptor for HSP70 is CD40, which with its CD40 ligand constitutes a major co-stimulatory pathway in the interaction between antigen-presenting cells and T-cells, HSP70 may function as an alternative ligand to CD40L. HSP70-CD40 interaction has been demonstrated in non-human primates to play a role in HIV infection, in protection against Mycobacterium tuberculosis and in conversion of tolerance to immunity.
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PMID:Functional domains of HSP70 stimulate generation of cytokines and chemokines, maturation of dendritic cells and adjuvanticity. 1527 Jun 93

Pyrazinamide (PZA) is an unconventional front line tuberculosis drug characterized by high in vivo sterilizing activity, but poor in vitro activity. This disparity in PZA activity may reflect differences between the in vivo tissue environment and in vitro culture conditions. This study examined the effect of anaerobic conditions, which exist in granulomatous lesions in vivo, on PZA activity in vitro. Low oxygen enhanced the activity of PZA against Mycobacterium tuberculosis, with anaerobic conditions resulting in greater enhancement than microaerobic conditions. ATPase and respiratory chain enzyme inhibitors enhanced PZA activity under normal atmospheric conditions, but not under anaerobic conditions. Furthermore, the inhibitors did not enhance isoniazid or rifampicin activity. Nitrate as an alternative electron acceptor antagonized PZA activity under anaerobic conditions. These findings provide further support for a proposed mechanism of action of PZA in which the active form of PZA (pyrazinoic acid) depletes the membrane energy reserve. They also provide another explanation for the higher sterilizing activity of PZA within in vivo lesions with low oxygen than under in vitro drug susceptibility testing conditions with ambient oxygen.
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PMID:Anaerobic incubation conditions enhance pyrazinamide activity against Mycobacterium tuberculosis. 1527 64

Chaperonin-60s are large double ring oligomeric proteins with a central cavity where unfolded polypeptides undergo productive folding. In conjunction with their co-chaperonin, Chaperonin-60s bind non-native polypeptides and facilitate their refolding in an ATP-dependent manner. The ATPase activity of Chaperonin-60 is tightly regulated by the 10 kDa co-chaperonin. In contrast to most other bacterial species, Mycobacterium tuberculosis genome carries a duplicate set of cpn60 genes, one of which occurs on the groESL operon (cpn60.1), while the other is separately arranged on the chromosome (cpn60.2). Biophysical characterization of the mycobacterial proteins showed that these proteins exist as lower oligomers and not tetradecamers, an unexpected property much different from the other known Chaperonin-60s. Failure of the M.tuberculosis chaperonins to oligomerize can be attributed to amino acid mutations at the oligomeric interface. Rates of ATP hydrolysis of the M.tuberculosis chaperonins showed that these proteins possess a very weak ATPase activity. Both the M.tuberculosis chaperonins were partially active in refolding substrate proteins. Interestingly, their refolding activity was seen to be independent of the co-chaperonin and ATP. We hypothesize that the ATP independent chaperones might offer benefit to the pathogen by promoting its existence in the latent phase of its life cycle.
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PMID:Mycobacterium tuberculosis GroEL homologues unusually exist as lower oligomers and retain the ability to suppress aggregation of substrate proteins. 1532 59

A screen for Mycobacterium tuberculosis (Mtb) mutants sensitive to reactive nitrogen intermediates identified transposon insertions in the presumptive proteasomal ATPase gene mpa (mycobacterium proteasome ATPase; Rv2115c). mpa mutants are attenuated in both wild type and nitric oxide synthase 2 deficient mice. In this work, we show that attenuation of mpa mutants is severe, and that Mpa is an ATPase associated with various cellular activities (AAA) ATPase that forms hexameric rings resembling the eukaryotic complex p97/valosin-containing protein (VCP). Point mutations in the conserved Walker box ATPase motifs of Mpa greatly reduced or abolished ATPase activity in vitro and abrogated protection of Mtb against acidified nitrite. A mutant Mpa protein missing only its last two amino acids retained ATPase activity, yet failed to protect Mtb against nitrite. The corresponding strain was attenuated in mice. Thus, Mpa is an ATPase whose enzymatic activity is necessary but not sufficient to protect against reactive nitrogen intermediates.
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PMID:Characterization of a Mycobacterium tuberculosis proteasomal ATPase homologue. 1565 70

DNA gyrase is a DNA topoisomerase indispensable for cellular functions in bacteria. We describe a novel, hitherto unknown, mechanism of specific inhibition of Mycobacterium smegmatis and Mycobacterium tuberculosis DNA gyrase by a monoclonal antibody (mAb). Binding of the mAb did not affect either GyrA-GyrB or gyrase-DNA interactions. More importantly, the ternary complex of gyrase-DNA-mAb retained the ATPase activity of the enzyme and was competent to catalyse DNA cleavage-religation reactions, implying a new mode of action different from other classes of gyrase inhibitors. DNA gyrase purified from fluoroquinolone-resistant strains of M.tuberculosis and M.smegmatis were inhibited by the mAb. The absence of cross-resistance of the drug-resistant enzymes from two different sources to the antibody-mediated inhibition corroborates the new mechanism of inhibition. We suggest that binding of the mAb in the proximity of the primary dimer interface region of GyrA in the heterotetrameric enzyme appears to block the release of the transported segment after strand passage, leading to enzyme inhibition. The specific inhibition of mycobacterial DNA gyrase with the mAb opens up new avenues for designing novel lead molecules for drug discovery and for probing gyrase mechanism.
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PMID:A monoclonal antibody that inhibits mycobacterial DNA gyrase by a novel mechanism. 1593 Jan 58

Class III adenylyl cyclases usually possess six highly conserved catalytic residues. Deviations in these canonical amino acids are observed in several putative adenylyl cyclase genes as apparent in several bacterial genomes. This suggests that a variety of catalytic mechanisms may actually exist. The gene Rv0386 from Mycobacterium tuberculosis codes for an adenylyl cyclase catalytic domain fused to an AAA-ATPase and a helix-turn-helix DNA-binding domain. In Rv0386, the standard substrate, adenine-defining lysine-aspartate couple is replaced by glutamine-asparagine. The recombinant adenylyl cyclase domain was active with a V(max) of 8 nmol cAMP.mg(-1).min(-1). Unusual for adenylyl cyclases, Rv0386 displayed 20% guanylyl cyclase side-activity with GTP as a substrate. Mutation of the glutamine-asparagine pair either to alanine residues or to the canonical lysine-aspartate consensus abolished activity. This argues for a novel mechanism of substrate selection which depends on two non-canonical residues. Data from individual and coordinated point mutations suggest a model for purine definition based on an amide switch related to that previously identified in cyclic nucleotide phosphodiesterases.
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PMID:Adenylyl cyclase Rv0386 from Mycobacterium tuberculosis H37Rv uses a novel mode for substrate selection. 1595 67

The response of dendritic cells (DCs) plays an essential role in the initiation of immune responses following Mycobacterium tuberculosis (MTB) challenge. Two-dimensional electrophoresis (2-DE) was employed to compare the global protein patterns between human DCs infected and that uninfected with MTB H37Rv ATCC 27294 strains, and 45 protein spots were found to express differentially. Four protein spots which remarkably changed in DCs infected with MTB H37Rv ATCC 27294 strains were measured by matrix assisted laser desorption/ionization tandem time-of-flight (TOF/TOF) mass spectrometry. The data obtained from peptide mass fingerprinting were used in protein database search. Four protein spots in gel were identified as Human Arsenite-stimulated ATPase (hASNA-I), Annexin IV, gamma-actin and Heat shock protein27 (HSP27). These data provide insight into the changed global protein patterns of the DCs after infection and may prove useful for further study in the interaction between MTB and host.
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PMID:[Protein profiling of human dendritic cells infected with mycobacterium tuberculosis]. 1598 38

Corynebacterium glutamicum, a soil Gram-positive bacterium used for industrial amino acid production, was found to grow optimally at pH 7.0-9.0 when incubated in 5 litre fermenters under pH-controlled conditions. The highest biomass was accumulated at pH 9.0. Growth still occurred at pH 9.5 but at a reduced rate. The expression of the pH-regulated F0 F1 ATPase operon (containing the eight genes atpBEFHAGDC) was induced at alkaline pH. A 7.5 kb transcript, corresponding to the eight-gene operon, was optimally expressed at pH 9.0. The same occurred with a 1.2 kb transcript corresponding to the atpB gene. RT-PCR studies confirmed the alkaline pH induction of the F0 F1 operon and the existence of the atpI gene. The atpI gene, located upstream of the F0 F1 operon, was expressed at a lower level than the polycistronic 7.5 kb mRNA, from a separate promoter (P-atp1). Expression of the major promoter of the F0 F1 operon, designated P-atp2, and the P-atp1 promoter was quantified by coupling them to the pET2 promoter-probe vector. Both P-atp1 and P-atp2 were functional in C. glutamicum and Escherichia coli. Primer extension analysis identified one transcription start point inside each of the two promoter regions. The P-atp1 promoter fitted the consensus sequence of promoters recognized by the vegetative sigma factor of C. glutamicum, whereas the -35 and -10 boxes of P-atp2 fitted the consensus sequence for sigma(H)-recognized Mycobacterium tuberculosis promoters C(C)/(G)GG(A)/(G)AC 17-22 nt (C)/(G)GTT(C)/(G), known to be involved in expression of heat-shock and other stress-response genes. These results suggest that the F0 F1 operon is highly expressed at alkaline pH, probably using a sigma (H) RNA polymerase.
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PMID:Transcriptional analysis of the F0F1 ATPase operon of Corynebacterium glutamicum ATCC 13032 reveals strong induction by alkaline pH. 2375 42

Oligomerization of the initiator protein, DnaA, on the origin of replication (oriC) is crucial for initiation of DNA replication. Studies in Escherichia coli (Gram-negative) have revealed that binding of DnaA to ATP, but not hydrolysis of ATP, is sufficient to promote DnaA binding, oligomerization and DNA strand separation. To begin understanding the initial events involved in the initiation of DNA replication in Mycobacterium tuberculosis (Gram-positive), we investigated interactions of M. tuberculosis DnaA (DnaA(TB)) with oriC using surface plasmon resonance in the presence of ATP and ADP. We provide evidence that, in contrast to what is observed in E. coli, ATPase activity of DnaA(TB) promoted rapid oligomerization on oriC. In support, we found that a recombinant mutant DnaA(TB) proficient in binding to ATP, but deficient in ATPase activity, did not oligomerize as rapidly. The corresponding mutation in the dnaA gene of M. tuberculosis resulted in non-viability, presumably due to a defect in oriC-DnaA interactions. Dimethy sulphate (DMS) footprinting experiments revealed that DnaA(TB) bound to DnaA boxes similarly with ATP or ADP. DnaA(TB) binding to individual DnaA boxes revealed that rapid oligomerization on oriC is triggered only after the initial interaction of DnaA with individual DnaA boxes. We propose that ATPase activity enables the DnaA protomers on oriC to rapidly form oligomeric complexes competent for replication initiation.
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PMID:The intrinsic ATPase activity of Mycobacterium tuberculosis DnaA promotes rapid oligomerization of DnaA on oriC. 1655 90


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