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  • 1
    Electronic Resource
    Electronic Resource
    Stereochemical course of malonate decarboxylation in Malonomonas rubra (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 1153-1154 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00108a042
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Icm/Dot-dependent upregulation of phagocytosis by Legionella pneumophila (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Legionella pneumophila is the causative agent of Legionnaires' disease, a severe pneumonia. Dependent on the icm/dot loci, L. pneumophila survives and replicates in macrophages and amoebae within a specialized phagosome that does not fuse with lysosomes. Here, we report that phagocytosis of wild-type L. pneumophila is more efficient than uptake of icm/dot mutants. Compared with the wild-type strain JR32, about 10 times fewer icm/dot mutant bacteria were recovered from HL-60 macrophages in a gentamicin protection assay. The defect in phagocytosis of the mutants could be complemented by supplying the corresponding genes on a plasmid. Using fluorescence microscopy and green fluorescent protein (GFP)-expressing strains, 10–20 times fewer icm/dot mutant bacteria were found to be internalized by HL-60 cells and human monocyte-derived macrophages (HMMΦ). Compared with icm/dot mutants, wild-type L. pneumophila infected two to three times more macrophages and yielded a population of highly infected host cells (15–70 bacteria per macrophage) that was not observed with icm/dot mutant strains. Wild-type and icmT mutant bacteria were found to adhere similarly and compete for binding to HMMΦ. In addition, wild-type L. pneumophila was also phagocytosed more efficiently by Acanthamoeba castellanii, indicating that the process is independent of adherence receptor(s). Wild-type L. pneumophila enhanced phagocytosis of an icmT mutant strain in a synchronous co-infection, suggesting that increased phagocytosis results from (a) secreted effector(s) acting in trans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02645.x
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymic and genetic basis for bacterial growth on malonate (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 25 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Various bacteria are able to grow aerobically or anaerobically on malonate as sole source of carbon and energy. Independent of the mechanism for energy conservation, the decarboxylation of malonate is the key reaction in the decomposition of this compound. To achieve malonate decarboxylation under physiological conditions, the substrate must be converted into an activated (thioester) derivative. We report here on the malonate decarboxylases of Malonomonas rubra and Klebsiella pneumoniae. These enzymes perform an interesting substrate activation mechanism by generating a malonyl thioester with the enzyme. Formation of the malonyl-S-enzyme involves an ‘activation module’ that comprises the acetylation of a specific thiol group of an acyl carrier protein (ACP) and the transfer of the ACP moiety to malonate, yielding malonyl-S-ACP and acetate. The malonyl-S-ACP is subsequently decarboxylated with regeneration of the acetyl-ACP. The malonate activation mechanism is related to the activation of citrate by citrate lyase. The relationship extends to the identical 2′-(5′′-phosphoribosyl)-3′-dephospho-CoA thiol cofactor that is bound covalently to the corresponding ACP subunit. In Klebsiella pneumoniae, malonate is decarboxylated by a water-soluble enzyme complex. In the anaerobic bacterium Malonomonas rubra, malonate decarboxylation is catalysed by a set of water-soluble as well as membrane-bound enzymes that function together in converting the free energy of the decarboxylation reaction into ΔμNa+. Therefore, this malonate decarboxylase includes a biotin carrier protein that accepts the CO2 moiety from malonyl-S-ACP and delivers it to a membrane-bound decarboxylase acting as a Na+ pump. Genes encoding the individual protein components that perform the decarboxylation of malonate in K. pneumoniae or M. rubra have been identified within the mdc and mad gene clusters respectively. The function of most of the derived proteins could be envisaged from sequence similarities with proteins of known functions. The genetic evidence firmly supports the idea that malonate decarboxylation is carried out by the two different decarboxylases, as deduced from the biochemical studies of the enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.4611824.x
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  • 4
    Electronic Resource
    Electronic Resource
    Macroautophagy is dispensable for intracellular replication of Legionella pneumophila in Dictyostelium discoideum (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Gram-negative bacterium Legionella pneumophila is a facultative intracellular pathogen of free-living amoebae and mammalian phagocytes. L. pneumophila is engulfed in phagosomes that initially avoid fusion with lysosomes. The phagosome associates with endoplasmic reticulum (ER) and mitochondria and eventually resembles ER. The morphological similarity of the replication vacuole to autophagosomes, and enhanced bacterial replication in response to macroautophagy-inducing starvation, led to the hypothesis that L. pneumophila infection requires macroautophagy. As L. pneumophila replicates in Dictyostelium discoideum, and macroautophagy genes have been identified and mutated in D. discoideum, we have taken a genetic and cell biological approach to evaluate the relationship between host macroautophagy and intracellular replication of L. pneumophila. Mutation of the apg1, apg5, apg6, apg7 and apg8 genes produced typical macroautophagy defects, including reduced bulk protein degradation and cell viability during starvation. We show that L. pneumophila replicates normally in D. discoideum macroautophagy mutants and produces replication vacuoles that are morphologically indistinguishable from those in wild-type D. discoideum. Furthermore, a green fluorescent protein (GFP)-tagged marker of autophagosomes, Apg8, does not systematically co-localize with DsRed-labelled L. pneumophila. We conclude that macroautophagy is dispensable for L. pneumophila intracellular replication in D. discoideum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03826.x
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  • 5
    Electronic Resource
    Electronic Resource
    Purification and characterization of a cytoplasmic enzyme component of the Na+-activated malonate decarboxylase system of Malonomonas rubra: acetyl-S-acyl carrier protein: malonate acyl carrier protein-SH transferase (1994)
    Springer
    Archives of microbiology 162 (1994), S. 48-56 
    Details
    ISSN: 1432-072X
    Keywords: Malonyl-CoA:acetate CoA transferase ; Na+ transport decarboxylases ; Na+ cycle ; Citrate lyase ; Citramalate lyase ; CoA-like prosthetic group ; Citramalate lyase (EC 4.1.3.22) ; Citrate lyase (EC 4.1.3.6) ; Malonate decarboxylase (EC 4.1.1.-)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Malonate decarboxylation by crude extracts of Malonomonas rubra was specifically activated by Na+ and less efficiently by Li+ ions. The extracts contained an enzyme catalyzing CoA transfer from malonyl-CoA to acetate, yielding acetyl-CoA and malonate. After about a 26-fold purification of the malonyl-CoA:acetate CoA transferase, an almost pure enzyme was obtained, indicating that about 4% of the cellular protein consisted of the CoA transferase. This abundance of the transferase is in accord with its proposed role as an enzyme component of the malonate decarboxylase system, the key enzyme of energy metabolism in this organism. The apparent molecular weight of the polypeptide was 67,000 as revealed from SDS-polyacrylamide gel electrophoresis. A similar molecular weight was estimated for the native transferase by gel chromatography, indicating that the enzyme exists as a monomer. Kinetic analyses of the CoA transferase yielded the following: pH-optimum at pH 5.5, an apparent Km for malonyl-CoA of 1.9mM, for acetate of 54mM, for acetyl-CoA of 6.9mM, and for malonate of 0.5mM. Malonate or citrate inhibited the enzyme with an apparent Ki of 0.4mM and 3.0mM, respectively. The isolated CoA transferase increased the activity of malonate decarboxylase of a crude enzyme system, in which part of the endogenous CoA transferase was inactivated by borohydride, about three-fold. These results indicate that the CoA transferase functions physiologically as a component of the malonate decarboxylase system, in which it catalyzes the transfer of acyl carrier protein from acetyl acyl carrier protein and malonate to yield malonyl acyl carrier protein and acetate. Malonate is thus activated on the enzyme by exchange for the catalytically important enzymebound acetyl thioester residues noted previously. This type of substrate activation resembles the catalytic mechanism of citrate lyase and citramalate lyase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264372
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  • 6
    Electronic Resource
    Electronic Resource
    The malonate decarboxylase enzyme system of Malonomonas rubra: evidence for the cytoplasmic location of the biotin-containing component (1993)
    Springer
    Archives of microbiology 160 (1993), S. 126-131 
    Details
    ISSN: 1432-072X
    Keywords: Malonomonas rubra ; Propionigenium modestum ; Malonate decarboxylase ; Methylmalonyl-CoA decarboxylase ; Biotin ; Avidin ; Electron microscopy ; High pressure freezing ; Immunolabeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Malonate decarboxylase of Malonomonas rubra is a complex enzyme system involving cytoplasmic and membrane-bound components. One of these is a biotin-containing protein of Mr 120'000, the location of which in the cytoplasm was deduced from the following criteria: (i) If the cytoplasm was incubated with avidin and the malonate decarboxylase subsequently completed with the membrane fraction the decarboxylase activity was abolished. The corresponding incubation of the membrane with avidin, however, was without effect. (ii) Western blot analysis identified the single biotin-containing polypeptide of Mr 120'000 within the cytoplasm. (iii) Transmission electron micrographs of immuno-gold labeled M. rubra cells clearly showed the location of the biotinyl protein within the cytoplasm, whereas the same procedure with Propionigenium modestum cells indicated the location of the biotin enzyme methylmalonyl-CoA decarboxylase in the cell membrane. The biotin-containing protein of the M. rubra malonate decarboxylase enzyme system was not retained by monomeric avidin-Sepharose columns but could be isolated with this column in a catalytically inactive form in the presence of detergents. If the high binding affinity of tetrameric avidin towards biotin was reduced by destructing part of the tryptophan residues by irradiation or oxidation with periodate, the inhibition of malonate decarboxylase by the modified avidin was partially reversed with an excess of biotin. Attempts to purify the biotin protein in its catalytically active state using modified avidin columns were without success.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288714
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