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| 2. |
- Nitharwal, Ram Gopal, et al.
(author)
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Helicobacter pylori chromosomal DNA replication : Current status and future perspectives
- 2011
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In: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 585:1, s. 7-17
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Research review (peer-reviewed)abstract
- Helicobacter pylori causes gastritis, gastric ulcer and gastric cancer. Though DNA replication and its control are central to bacterial proliferation, pathogenesis, virulence and/or dormancy, our knowledge of DNA synthesis in slow growing pathogenic bacteria like H. pylori is still preliminary. Here, we review the current understanding of DNA replication, replication restart and recombinational repair in H. pylori. Several differences have been identified between the H. pylori and Escherichia coli replication machineries including the absence of DnaC, the helicase loader usually conserved in gram-negative bacteria. These differences suggest different mechanisms of DNA replication at initiation and restart of stalled forks in H. pylori.
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| 3. |
- Pettersson, B. M. Fredrik, et al.
(author)
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Identification and expression of stressosomal proteins in Mycobacterium marinum under various growth and stress conditions
- 2013
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 342:2, s. 98-105
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Journal article (peer-reviewed)abstract
- Like other bacteria, Mycobacterium spp. have developed different strategies in response to environmental changes such as nutrient limitations and other different stress situations. We have identified candidate genes (rsb genes) from Mycobacterium marinum involved in the regulation of the activity of the alternative sigma factor, sigma F. This is a homolog of the master regulator of general stress response, sigma B, and the sporulation-specific sigma factor, sigma F, in Bacillus subtilis. The organization of these genes in M.marinum and B.subtilis is similar. Transcriptome and qRT-PCR data show that these genes are indeed expressed in M.marinum and that the levels of expression vary with growth phase and exposure to stress. In particular, cold stress caused a significant rise in the expression of all identified rsb and sigF genes. We discuss these data in relation to what is currently known for other Mycobacterium spp.
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| 4. |
- Ramesh, Malavika, et al.
(author)
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Intracellular localization of the mycobacterial stressosome complex
- 2021
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Journal article (peer-reviewed)abstract
- Microorganisms survive stresses by alternating the expression of genes suitable for surviving the immediate and present danger and eventually adapt to new conditions. Many bacteria have evolved a multiprotein "molecular machinery" designated the "Stressosome" that integrates different stress signals and activates alternative sigma factors for appropriate downstream responses. We and others have identified orthologs of some of the Bacillus subtilis stressosome components, RsbR, RsbS, RsbT and RsbUVW in several mycobacteria and we have previously reported mutual interactions among the stressosome components RsbR, RsbS, RsbT and RsbUVW from Mycobacterium marinum. Here we provide evidence that "STAS" domains of both RsbR and RsbS are important for establishing the interaction and thus critical for stressosome assembly. Fluorescence microscopy further suggested co-localization of RsbR and RsbS in multiprotein complexes visible as co-localized fluorescent foci distributed at scattered locations in the M. marinum cytoplasm; the number, intensity and distribution of such foci changed in cells under stressed conditions. Finally, we provide bioinformatics data that 17 (of 244) mycobacteria, which lack the RsbRST genes, carry homologs of Bacillus cereus genes rsbK and rsbM indicating the existence of alternative σF activation pathways among mycobacteria.
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| 5. |
- Singh, Bhupender, et al.
(author)
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Asymmetric growth and division in Mycobacterium spp. : compensatory mechanisms for non-medial septa
- 2013
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In: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 88:1, s. 64-76
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Journal article (peer-reviewed)abstract
- Mycobacterium spp., rod-shaped cells belonging to the phylum Actinomycetes, lack the Min- and Noc/Slm systems responsible for preventing the placement of division sites at the poles or over the nucleoids to ensure septal assembly at mid-cell. We show that the position for establishment of the FtsZ-ring in exponentially growing Mycobacterium marinum and Mycobacterium smegmatis cells is nearly random, and that the cells often divide non-medially, producing two unequal but viable daughters. Septal sites and cellular growth disclosed by staining with the membrane-specific dye FM4-64 and fluorescent antibiotic vancomycin (FL-Vanco), respectively, showed that many division sites were off-centre, often over the nucleoids, and that apical cell growth was frequently unequal at the two poles. DNA transfer through the division septum was detected, and translocation activity was supported by the presence of a putative mycobacterial DNA translocase (MSMEG2690) at the majority of the division sites. Time-lapse imaging of single live cells through several generations confirmed both acentric division site placement and unequal polar growth in mycobacteria. Our evidence suggests that post-septal DNA transport and unequal polar growth may compensate for the non-medial division site placement in Mycobacterium spp.
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| 6. |
- Verma, Vijay, et al.
(author)
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Modulation of the enzymatic activities of replicative helicase (DnaB) by interaction with Hp0897 : a possible mechanism for helicase loading in Helicobacter pylori
- 2016
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In: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 44:7, s. 3288-3303
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Journal article (peer-reviewed)abstract
- DNA replication in Helicobacter pylori is initiated from a unique site (oriC) on its chromosome where several proteins assemble to form a functional replisome. The assembly of H. pylori replication machinery is similar to that of the model gram negative bacterium Escherichia coli except for the absence of DnaC needed to recruit the hexameric DnaB helicase at the replisome assembly site. In the absence of an obvious DnaC homologue in H. pylori, the question arises as to whether HpDnaB helicase is loaded at the Hp-replication origin by itself or is assisted by other unidentified protein(s). A high-throughput yeast two-hybrid study has revealed two proteins of unknown functions (Hp0897 and Hp0340) that interact with HpDnaB. Here we demonstrate that Hp0897 interacts with HpDnaB helicase in vitro as well as in vivo. Furthermore, the interaction stimulates the DNA binding activity of HpDnaB and modulates its adenosine triphosphate hydrolysis and helicase activities significantly. Prior complex formation of Hp0897 and HpDnaB enhances the binding/loading of DnaB onto DNA. Hp0897, along with HpDnaB, colocalizes with replication complex at initiation but does not move with the replisome during elongation. Together, these results suggest a possible role of Hp0897 in loading of HpDnaB at oriC.
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| 7. |
- Wiseman, Benjamin, et al.
(author)
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Structure of a full-length bacterial polysaccharide co-polymerase
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- Lipopolysaccharides are important components of the bacterial cell envelope that among other things act as a protective barrier against the environment and toxic molecules such as antibiotics. One of the most widely disseminated pathways of polysaccharide biosynthesis is the inner membrane bound Wzy-dependent pathway. Here we present the 3.0 Å structure of the co-polymerase component of this pathway, WzzB from E. coli solved by single-particle cryo-electron microscopy. The overall architecture is octameric and resembles a box jellyfish containing a large bell-shaped periplasmic domain with the 2-helix transmembrane domain from each protomer, positioned 32 Å apart, encircling a large empty transmembrane chamber. This structure also reveals the architecture of the transmembrane domain, including the location of key residues for the Wzz-family of proteins and the Wzy-dependent pathway present in many Gram-negative bacteria, explaining several of the previous biochemical and mutational studies and lays the foundation for future investigations.
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| 8. |
- Wiseman, Benjamin, et al.
(author)
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Structure of a functional obligate complex III2IV2 respiratory supercomplex from Mycobacterium smegmatis
- 2018
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In: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 25:12, s. 1128-1136
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Journal article (peer-reviewed)abstract
- In the mycobacterial electron-transport chain, respiratory complex III passes electrons from menaquinol to complex IV, which in turn reduces oxygen, the terminal acceptor. Electron transfer is coupled to transmembrane proton translocation, thus establishing the electrochemical proton gradient that drives ATP synthesis. We isolated, biochemically characterized, and determined the structure of the obligate III2IV2 supercomplex from Mycobacterium smegmatis, a model for Mycobacterium tuberculosis. The supercomplex has quinol:O-2 oxidoreductase activity without exogenous cytochrome c and includes a superoxide dismutase subunit that may detoxify reactive oxygen species produced during respiration. We found menaquinone bound in both the Q(o) and Q(i) sites of complex III. The complex III-intrinsic diheme cytochrome cc subunit, which functionally replaces both cytochrome c(1) and soluble cytochrome c in canonical electron-transport chains, displays two conformations: one in which it provides a direct electronic link to complex IV and another in which it serves as an electrical switch interrupting the connection.
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