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  • 1
    Electronic Resource
    Electronic Resource
    Na+ translocation by the NADH:ubiquinone oxidoreductase (complex I) from Klebsiella pneumoniae (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 33 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Complex I is the site for electrons entering the respiratory chain and therefore of prime importance for the conservation of cell energy. It is generally accepted that the complex I-catalysed oxidation of NADH by ubiquinone is coupled specifically to proton translocation across the membrane. In variance to this view, we show here that complex I of Klebsiella pneumoniae operates as a primary Na+ pump. Membranes from Klebsiella pneumoniae catalysed Na+-stimulated electron transfer from NADH or deaminoNADH to ubiquinone-1 (0.1–0.2 μmol min−1 mg−1). Upon NADH or deaminoNADH oxidation, Na+ ions were transported into the lumen of inverted membrane vesicles. Rate and extent of Na+ transport were significantly enhanced by the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP) to values of ≈0.2 μmol min−1 mg−1 protein. This characterizes the responsible enzyme as a primary Na+ pump. The uptake of sodium ions was severely inhibited by the complex I-specific inhibitor rotenone with deaminoNADH or NADH as substrate. N-terminal amino acid sequence analyses of the partially purified Na+-stimulated NADH:ubiquinone oxidoreductase from K. pneumoniae revealed that two polypeptides were highly similar to the NuoF and NuoG subunits from the H+-translocating NADH:ubiquinone oxidoreductases from enterobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01506.x
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Na+ translocation by complex I (NADH:quinone oxidoreductase) of Escherichia coli (2000)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Following on from our previous discovery of Na+ pumping by the NADH:ubiquinone oxidoreductase (complex I) of Klebsiella pneumoniae, we show here that complex I from Escherichia coli is a Na+ pump as well. Our study object was the Escherichia coli mutant EP432, which lacks the Na+/H+ antiporter genes nhaA and nhaB and is therefore unable to grow on LB medium at elevated Na+ concentrations. During growth on mineral medium, the Na+ tolerance of E. coli EP432 was influenced by the organic substrate. NaCl up to 450 mM did not affect growth on glycerol and fumarate, but growth on glucose was inhibited. Correlated to the Na+ tolerance was an increased synthesis of complex I in the glycerol/fumarate medium. Inverted membrane vesicles catalysed respiratory Na+ uptake with NADH as electron donor. The sodium ion transport activity of vesicles from glycerol/fumarate-grown cells was 40 nmol mg−1 min−1 and was resistant to the uncoupler carbonyl-cyanide m-chlorophenylhydrazone (CCCP), but was inhibited by the complex I-specific inhibitor rotenone. With an E. coli mutant deficient in complex I, the Na+ transport activity was low (1–3 nmol mg−1 min−1), and rotenone was without effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01712.x
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of anaerobic citrate metabolism in Klebsiella pneumoniae (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Three enzymes are specifically required for uptake and catabolism of citrate by Klebsiella pneumoniae under anaerobic conditions: a Na+-dependent citrate carrier (CitS), citrate lyase (CitDEF), and the Na+ pump oxalo-acetate decarboxylase (OadGAB). The corresponding genes are clustered on the chromosome, with the citCDEFG genes located upstream and divergent to the citS—oadGAB genes. We found that expression of citS from its native promoter in Escherichia coli requires the DNA region downstream of oadB. Nucleotide sequence analysis of this region revealed the presence of two adjacent genes, citA and citB, By sequence similarity, the predicted CitA and CitB proteins were identified as members of the two-component regulatory systems. The sensor kinase CitA contained, in the N-terminal half, two putative transmembrane helices which enclosed a presumably periplasmic domain of about 130 amino acids. The C-terminal half of the response regulator CitB harboured a helix-turn-helix motif typical of DNA-binding proteins. K. pneumoniaecitB null mutants were unable to grow anaerobically with citrate as the sole carbon and energy source (Cit− phenotype). When cultivated anaerobically with citrate plus glycerol, all of the citrate-specific fermentation enzymes were synthesized in the wild type, but not in the citB mutants. This showed that citS, oadGAB and citDEF required the CitB protein for expression and therefore are part of a regulon. In the wild type, synthesis of CitS, oxalo-acetate decarboxylase and citrate lyase was dependent on the presence of citrate, sodium ions and a low oxygen tension. In a citA null mutant which expressed citB constitutively at high levels, none of these signals was required for the formation of the citrate fermentation enzymes. This result suggested that citrate, Na+, and oxygen exerted their regulatory effects via the CitA/CitB system. In the presence of these signals, the citAB gene products induced their own synthesis. The positive autoregulation occurred via co-transcription of citAB with citS and oadGAB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18030533.x
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  • 5
    Electronic Resource
    Electronic Resource
    Anaerobic growth of Salmonella typhimurium on l(+)- and d(–)-tartrate involves an oxaloacetate decarboxylase Na+ pump (1994)
    Springer
    Archives of microbiology 162 (1994), S. 233-237 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Fermentation of tartrate ; Fermentation ; of citrate ; Enterobacteria ; Tartrate dehydratase ; Na+-translocating oxaloacetate decarboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      We show here that the Enterobacterium Salmonella typhimurium LT2 has the capacity to grow anaerobically on l(+)- or d(–)-tartrate as sole carbon and energy source. Growth on these substrates was Na+-dependent and involved the l(+)- or d(–)-tartrate-inducible expression of oxaloacetate decarboxylase. The induced decarboxylase was closely related to the o xaloacetate decarboxylase Na+ pump of Klebsiella pneumoniae as shown by the sensitivity towards avidin, the location in the cytoplasmic membrane, activation by Na+ ions, and Western blot analysis with antiserum raised against the K. pneumoniae oxaloacetate decarboxylase. Participation of an oxaloacetate decarboxylase Na+ pump in l(+)-tartrate degradation by S. typhimurium is in accord with results from DNA analyses. The deduced protein seq uence of the open reading frame identified upstream of the recently sequenced oxaloacetate decarboxylase genes is clearly homologous with the β-subunit of l-tartrate dehydratase from Escherichia coli. Southern blot analysis with S. typhimurium chromosomal DNA indicated the presence of probably more than one gene for oxaloacetate decarboxylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301843
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  • 6
    Electronic Resource
    Electronic Resource
    A primary respiratory Na+ pump of an anaerobic bacterium: the Na+-dependent NADH:quinone oxidoreductase of Klebsiella pneumoniae (1989)
    Springer
    Archives of microbiology 151 (1989), S. 439-444 
    Details
    ISSN: 1432-072X
    Keywords: Klebsiella pneumoniae ; Citrate fermentation ; NADH:ubiquinone oxidoreductase ; Respiratory sodium pump ; Semiquinone radical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membranes of Klebsiella pneumoniae, grown anaerobically on citrate, contain a NADH oxidase activity that is activated specifically by Na+ or Li+ ions and effectively inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Cytochromes b and d were present in the membranes, and the steady state reduction level of cytochrome b increased on NaCl addition. Inverted bacterial membrane vesicles accumulated Na+ ions upon NADH oxidation. Na+ uptake was completely inhibited by monensin and by HQNO and slightly stimulated by carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), thus indicating the operation of a primary Na+ pump. A Triton extract of the bacterial membranes did not catalyze NADH oxidation by O2, but by ferricyanide or menadione in a Na+-independent manner. The Na+-dependent NADH oxidation by O2 was restored by adding ubiquinone-1 in micromolar concentrations. After inhibition of the terminal oxidase with KCN, ubiquinol was formed from ubiquinone-1 and NADH. The reaction was stimulated about 6-fold by 10 mM NaCl and was severely inhibited by low amounts of HQNO. Superoxide radicals were formed during electron transfer from NADH to ubiquinone-1. These radicals disappeared by adding NaCl, but not with NaCl and HQNO. It is suggested that the superoxide radicals arise from semiquinone radicals which are formed by one electron reduction of quinone in a Na+-independent reaction sequence and then dismutate in a Na+ and HQNO sensitive reaction to quinone and quinol. The mechanism of the respiratory Na+ pump of K. pneumoniae appears to be quite similar to that of Vibrio alginolyticus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416604
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  • 7
    Electronic Resource
    Electronic Resource
    Isolation and characterization of oxaloacetate decarboxylase of Salmonella typhimurium, a sodium ion pump (1989)
    Springer
    Archives of microbiology 152 (1989), S. 584-588 
    Details
    ISSN: 1432-072X
    Keywords: Citrate fermentation ; Oxaloacetate decarboxylase ; Salmonella typhimurium ; Sodium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anaerobic growth of Salmonella typhimurium on citrate is Na+-dependent and requires induction of the necessary enzymes during a 20–40 h lag phase. The citrate fermentation pathway involves citrate lyase and oxaloacetate decarboxylase. The decarboxylase is a membrane-bound. Na+-activated, biotin-containing enzyme that functions as a Na+ pump. Oxaloacetate decarboxylase was isolated by affinity chromatography of a Triton X-100 extract of the bacterial membranes on avidin-Sepharose. The enzyme consists of three subunits α, β, γ, with apparent molecular weights of 63800, 34500 and 10600. The α-chain contains a covalently attached biotin group and binds to antibodies raised against the α-subunit of oxaloacetate decarboxylase from Klebsiella pneumoniae. The Na+ transport function was reconstituted by incorporation of the puriried enzyme into proteoliposomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425491
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  • 8
    Electronic Resource
    Electronic Resource
    Expression of subunits a and c of the sodium-dependent ATPase of Propionigenium modestum in Escherichia coli (1994)
    Springer
    Archives of microbiology 161 (1994), S. 495-500 
    Details
    ISSN: 1432-072X
    Keywords: F1F0 ATPase ; Expression of unc genes ; Complementation analysis ; Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of the present study was to construct functional hybrid ATPases consisting of all Escherichia coli ATPase subunits excepts the F0 subunits a or c which were replaced by the respective subunits of the Propionigenium modestum ATPase. This would give valuable information on the subunit(s) conferring the coupling ion specificity. Plasmids were constructed that carried the gene for subunit c (uncE) or subunit a (uncB) behind a tac promoter. These plasmids were transformed into E. coli strains which differed with respect to the unc operon and the expression of the P. modestum genes was verified biochemically. Enhanced expression of the P. modestum genes led to strong growth inhibition of all E. coli strains tested. However, the expressed P. modestum proteins could not functionally complement E. coli strains that lacked the homologous subunit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307770
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Energy conservation in the decarboxylation of dicarboxylic acids by fermenting bacteria (1998)
    Springer
    Archives of microbiology 170 (1998), S. 69-77 
    Details
    ISSN: 1432-072X
    Keywords: Key words ATP synthase ; Decarboxylation ; Electrogenic substrate/product antiporter ; Sodium ion ; pump ; Malo-lactic fermentation ; Oxalate ; Malonate ; Succinate ; Glutarate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Decarboxylation of dicarboxylic acids (oxalate, malonate, succinate, glutarate, and malate) can serve as the sole energy source for the growth of fermenting bacteria. Since the free energy change of a decarboxylation reaction is small (around –20 kJ per mol) and equivalent to only approximately one-third of the energy required for ATP synthesis from ADP and phosphate under physiological conditions, the decarboxylation energy cannot be conserved by substrate-level phosphorylation. It is either converted (in malonate, succinate, and glutarate fermentation) by membrane-bound primary decarboxylase sodium ion pumps into an electrochemical gradient of sodium ions across the membrane; or, alternatively, an electrochemical proton gradient can be established by the combined action of a soluble decarboxylase with a dicarboxylate/monocarboxylate antiporter (in oxalate and malate fermentation). The thus generated electrochemical Na+ or H+ gradients are then exploited for ATP synthesis by Na+- or H+-coupled F1F0 ATP synthases. This new type of energy conservation has been termed decarboxylation phosphorylation and is responsible entirely for ATP synthesis in several anaerobic bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050616
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