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  • 1
    Electronic Resource
    Electronic Resource
    Differential roles for menaquinone and demethylmenaquinone in anaerobic electron transport of E. coli and their fnr-independent expression (1988)
    Springer
    Archives of microbiology 150 (1988), S. 499-503 
    Details
    ISSN: 1432-072X
    Keywords: Menaquinone ; Demethylmenaquinone ; Anaerobic respiration ; fnr gene ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli grown with glucose in the absence of added electron acceptors contained 3–4 times more naphthoquinones (menaquinone plus demethylmenaquinone) than in the presence of O2. Presence of electron acceptors resulted in a slight additional increase of the naphthoquinone content. A strain defective in the fnr gene, which encodes the transcriptional activator of anaerobic respiration, showed the same response. With fumarate or dimethyl sulfoxide present, 94% of the naphthoquinones consisted of menaquinone, while with nitrate up to 78% was demethylmenaquinone. With trimethylamine N-oxid as the acceptor the proportion was intermediate. From the donor substrates of anaerobic respiration only glycerol had a significant influence on the ratio of the contents of the 2 quinones. It is concluded that FNR, the gene product of the fnr gene, is not required for anaerobic derepression of naphthoquinone viosynthesis. Menaquinone appears to be involved specifically in the respiration with fumarate or dimethyl sulfoxide, and demethylmenaquinone in nitrate respiration. Both naphthoquinones appear to serve in trimethylamine N-oxide respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422294
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The membraneous nitrite reductase involved in the electron transport of Wolinella succinogenes (1985)
    Springer
    Archives of microbiology 140 (1985), S. 380-386 
    Details
    ISSN: 1432-072X
    Keywords: Nitrite reductase ; Electron transport ; Wolinella succinogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wolinella succinogenes grown with nitrate as terminal electron acceptor contains two nitrite reductases as measured with the donor viologen radical, one in the cytoplasm and the other integrated in the cytoplasmic membrane. The fumarate-grown bacteria contain only the membraneous species. The isolated membraneous enzyme consists of a single polypeptide chain (M r 63,000) carrying 4 hemeC groups and probably an iron-sulphur cluster as prosthetic groups. The enzyme amounts to about 1% of the total membrane protein. The isolated enzyme catalyses the reduction of nitrite to ammonium without accumulation of significant amounts of intermediates or alternative products. The Michaelis constant for nitrite was 0.1 mM and the turnover number of the hemeC 1.5 · 105 electrons per min at 37°C. The viologen-reactive site of the enzyme in the membrane is oriented towards the cytoplasm. When the isolated enzyme is incorporated into liposomes, the viologen-as well as the nitrite-reactive site is exposed to thooutside. The cytoplasmic membrane contains a second hemeC protein (M r 22,000) which may represent a cytochrome c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446982
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Menaquinone is an obligatory component of the chain catalyzing succinate respiration in Bacillus subtilis (1990)
    Springer
    Archives of microbiology 155 (1990), S. 62-67 
    Details
    ISSN: 1432-072X
    Keywords: Menaquinone ; Succinate respiration ; Electron transport ; Bacillus subtilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The question was investigated as to whether the bacterial menaquinone (MK) is a component of the electron transport chain catalyzing succinate respiration in Bacillus subtilis. Three different methods were applied, and the following consistent results were obtained. (i) Solvent extraction of MK from the bacterial membrane caused total inhibition of the respiratory activities with succinate and NADH, while the activity of succinate dehydrogenase remained unaffected. The respiratory activities were restored onincorporation of vitamin K1 into the membrane preparation. (ii) The membrane fraction of a B. subtilis mutant containing 15% of the wild-type amount of MK, respired succinate and NADH at reduced activities. Wild-type activities were restored on fusion of the preparation to liposomes containing vitamin K1. (iii) The membrane fraction of B. subtilis catalyzed succinate oxidation by various water-soluble naphtho- or benzoquinones at specific activities exceeding to that of succinate respiration. The results suggest that MK is involved in succinate respiration, although its redox potential is unfavorable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291276
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    Paper (German National Licenses)
    Fulltext
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