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  • 1
    Electronic Resource
    Electronic Resource
    Role of 5′-TGN-3′ motif in the interaction of mycobacterial RNA polymerase with a promoter of ‘extended −10’ class (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 225 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In a systematic approach to understand the transcriptional machinery of mycobacteria, we had previously isolated and characterized mycobacterial promoter regions. In this study, we have investigated molecular interactions between mycobacterial RNA polymerase holoenzyme, reconstituted with different sigma subunits and the promoter element of the Mycobacterium tuberculosis gene pknH (Rv1266c), a representative of promoters belonging to the ‘extended −10’ class. In vitro transcription assays using the pknH promoter and reconstituted RNA polymerase holoenzyme demonstrated that transcription from the pknH promoter is specifically initiated by σA, the principal sigma factor of mycobacteria. DNase I protection assay and deletion studies with the pknH promoter revealed that the minimal region required for optimal transcription carries the sequence from position −37 to position +6. Moreover, mutation in the TGN motif of the pknH promoter resulted in the loss of 〉75% of its activity. Binding of RNA polymerase with wild-type promoter as well as its TG− mutant revealed that the TGN motif is required for the transition from a close complex into an open complex. Further, it was observed that the presence of the TGN motif reduces the thermal energy required for the conversion of a close complex into an open complex, necessary for initiation of transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00483-X
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  • 2
    Electronic Resource
    Electronic Resource
    Corrigendum to “mymA operon of Mycobacterium tuberculosis: its regulation and importance in the cell envelope” (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 232 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/rp10.1016-S0378-1097(02)01189-8
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  • 3
    Electronic Resource
    Electronic Resource
    Recombinant BCG approach for development of vaccines: cloning and expression of immunodominant antigens of M. tuberculosis (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 190 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In spite of major advances in our understanding of the biology and immunology of tuberculosis, the incidence of the disease has not reduced in most parts of the world. In an attempt to improve the protective efficacy of Mycobacterium bovis bacille Calmette–Guérin (BCG), we have developed a generic vector system, pSD5, for expression of genes at varying levels in mycobacteria. In this study, we have cloned and overexpressed three immunodominant secretory antigens of M. tuberculosis, 85A, 85B and 85C, belonging to the antigen 85 complex. All the genes were cloned under the control of a battery of mycobacterial promoters of varying strength. The expression was analysed in the fast-growing strain M. smegmatis and the slow-growing vaccine strain M. bovis BCG. The recombinant BCG constructs were able to express the antigens at high levels and the majority of the expressed antigens was secreted into the medium. These results show that by using this strategy the recombinant BCG approach can be successfully used for the development of candidate vaccines against infections associated with mycobacteria as well as other pathogens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09304.x
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  • 4
    Electronic Resource
    Electronic Resource
    mymA operon of Mycobacterium tuberculosis: its regulation and importance in the cell envelope (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 227 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mycobacterium tuberculosis faces various stressful conditions inside the host and responds to them through a coordinated regulation of gene expression. We had previously reported identification of the virS gene of M. tuberculosis (Rv3082c) belonging to the AraC family of transcriptional regulators. In the current study, we show that the seven genes (Rv3083–Rv3089) which are present divergently to virS (Rv3082c) constitute an operon designated the mymA operon. Further investigation on the regulation of this operon showed that transcription of the mymA operon is dependent on the presence of VirS protein. A four-fold induction of the mymA operon promoter occurs specifically in wild-type M. tuberculosis and not in the virS mutant of M. tuberculosis (MtbΔvirS) when exposed to acidic pH. Expression of the mymA operon was also induced in infected macrophages by 10-fold over a 6-day period. To gain an insight into the function of the proteins encoded by this operon, we carried out a bioinformatic analysis, which suggested the involvement of these proteins in the modification of fatty acids required for cell envelope. This was supported by altered colony morphology and cell envelope structure displayed by the virS mutant of M. tuberculosis (MtbΔvirS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00648-7
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  • 5
    Electronic Resource
    Electronic Resource
    Disruption of mptpB impairs the ability of Mycobacterium tuberculosis to survive in guinea pigs (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Protein tyrosine kinases and tyrosine phosphatases from several bacterial pathogens have been shown to act as virulence factors by modulating the phosphorylation and dephosphorylation of host proteins. The identification and characterization of two tyrosine phosphatases namely MptpA and MptpB from Mycobacterium tuberculosis has been reported earlier. MptpB is secreted by M. tuberculosis into extracellular mileu and exhibits a pH optimum of 5.6, similar to the pH of the lysosomal compartment of the cell. To determine the role of MptpB in the pathogenesis of M. tuberculosis, we constructed a mptpB mutant strain by homologous recombination and compared the ability of parent and the mutant strain to survive intracellularly. We show that disruption of the mptpB gene impairs the ability of the mutant strain to survive in activated macrophages and guinea pigs but not in resting macrophages suggesting the importance of its role in the host–pathogen interaction. Infection of guinea pigs with the mutant strain resulted in a 70-fold reduction in the bacillary load of spleens in infected animals as compared with the bacillary load in animals infected with the parental strain. Upon reintroduction of the mptpB gene into the mutant strain, the complemented strain was able to establish infection and survive in guinea pigs at rates comparable to the parental strain. These observations demonstrate a   role   of MptpB in the pathogenesis   of M. tuberculosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03712.x
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  • 6
    Electronic Resource
    Electronic Resource
    Polyamine — DNA nexus: structural ramifications and biological implications (1991)
    Springer
    Molecular and cellular biochemistry 100 (1991), S. 129-140 
    Details
    ISSN: 1573-4919
    Keywords: functions of polyamines ; cell growth ; B-Z DNA transitions ; compaction of DNA and chromatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Polyamines at physiological concentration can condense DNA, chromatin and promote B to Z DNA transitions. These properties of polyamines are crucial to the molecular organization and functional control of DNA and thus have very significant implications in the control of cellular functions. The structure of polyamines plays an important role in the binding of DNA and chromatin and it is not merely the charge, but a specific chain length of methylene (−CH2) groups that is required. Acetylation of polyamines seems to be an important mode of regulating polyamine-chromatin interaction. Purified histone acetyltransferase also possesses polyamine acetylation activity, thus histones and polyamine acetylation may occur in tandem to alter the structure/function of the nucleosome thereby regulating DNA replication and transcription. Acetylation as a means to diminish the number of charges on polyamine molecules serves as an ordered mechanism to control DNA replication and transcription in vivo. The results on the involvement of polyamines and their analogs in condensation of DNA and B to Z DNA transition correlate well with the conclusions drawn from experiments designed to observe the in vivo effects of polyamines and their analogs on the growth of prokaryotic and eukaryotic cells. For example, any change in the hydrogen bonding capacity of polyamines leads to a marked reduction in protein synthesis and the growth rate of polyamine depleted cells. A minimal level of polyamines is required for cells to move from G1 through S phase and these amines are directly involved in the DNA synthetic phase of the cell cycle. A nexus between polyamines and nucleic acids appears crucial to the cellular function(s) of polyamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234162
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  • 7
    Electronic Resource
    Electronic Resource
    Role of polyamines in the synthesis of RNA in mycobacteria (1987)
    Springer
    Molecular and cellular biochemistry 78 (1987), S. 3-8 
    Details
    ISSN: 1573-4919
    Keywords: polyamines ; RNA polymerase ; transcription ; gene expression ; mycobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract All three polyamines — putrescine, spermidine and spermine stimulated the activity of mycobacterial RNA polymerase in vitro although the concentration required for maximal stimulation was different for each of the amines. Spermidine and spermine showed a biphasic effect on the enzyme activity. Stimulation of RNA synthesis by spermidine occurs only at higher DNA template/enzyme ratio. Spermidine stimulates RNA synthesis by acting on the elongation phase of RNA synthesis but it had no effect on initiation phase. Addition of mycobacterial RNA to the assay mixture resulted in the inhibition of RNA polymerase activity and this inhibition could be reversed by spermidine suggesting that spermidine stimulates transcription by binding to nascent RNA and thus destabilizing the short DNA-RNA hybrid region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224418
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