Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Citrate is fermented by Klebsiella pneumoniae to 2 acetate, 0.5 formate and 1.2 CO2. The formation of less than 1 formate and greater than 1 CO2 per citrate can be accounted for by the oxidation of formate to CO2 in order to provide reducing equivalents for the assimilation of citrate into cell carbon. A membrane-bound electron transport chain is apparently involved in NADH synthesis by these cells. The electrons from formate oxidation to CO2 are used to reduce ubiquinone to ubiquinol by membrane-bound formate dehydrogenase and ubiquinol further delivers its electrons to NAD+, if this endergonic reaction is powered by delta mu Na+. The endogenous NADH level of K. pneumoniae cells thus increased in the presence of formate in response to a delta pNa+ greater than -100 mV. NADH formation was completely abolished in the presence of oxygen or after addition of hydroxyquinoline-N-oxide, a specific inhibitor of the Na(+)-translocating NADH:ubiquinone oxidoreductase. The increase of endogenous NADH was dependent on the delta pNa+ applied to the cells. Inverted membrane vesicles of K. pneumoniae catalysed the reduction of NAD+ to NADH with formate as electron donor after application of delta mu Na+ of about 120 mV consisting of delta pNa+ of 60 mV and delta psi of the same magnitude. Neither the delta pNa+ nor the delta psi of this size alone was sufficient to drive the endergonic reaction. Strictly anaerobic conditions were required for NADH formation and hydroxyquinoline-N-oxide completely inactivated the reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:NADH formation by Na(+)-coupled reversed electron transfer in Klebsiella pneumoniae. 150 43

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 dismutase 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.
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PMID:A primary respiratory Na+ pump of an anaerobic bacterium: the Na+-dependent NADH:quinone oxidoreductase of Klebsiella pneumoniae. 254 75

In addition to a cytoplasmic, NAD-dependent malate dehydrogenase (EC 1.1.1.37), Corynebacterium glutamicum possesses a highly active membrane-associated malate dehydrogenase (acceptor) (EC 1.1.99.16). This enzyme also takes part in the citric acid cycle. It oxidizes L-malate to oxaloacetate and donates electrons to ubiquinone-1 and other artificial acceptors or, via the electron transfer chain, to oxygen. NAD is not an acceptor and the natural direct acceptor for the enzyme is most likely a quinone. The enzyme is therefore called malate:quinone oxidoreductase, abbreviated to Mqo. Mqo is a peripheral membrane protein and can be released from the membrane by addition of chelators. The solubilized form was partially purified and characterized biochemically. FAD is probably a tightly but non-covalently bound prosthetic group, and the enzyme is activated by lipids. A C. glutamicum mutant completely lacking Mqo activity was isolated. It grows poorly on several substrates tested. The mutant possesses normal levels of cytoplasmic NAD-dependent malate dehydrogenase. A plasmid containing the gene from C. glutamicum coding for Mqo was isolated by complementation of the Mqo-negative phenotype. It leads to overexpression of Mqo activity in the mutant. The nucleotide sequence of the mqo gene was determined and is the first sequence known for this enzyme. The derived protein sequence is similar to hypothetical proteins from Escherichia coli, Klebsiella pneumoniae, and Mycobacterium tuberculosis.
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PMID:Biochemical and genetic characterization of the membrane-associated malate dehydrogenase (acceptor) from Corynebacterium glutamicum. 966 Jan 97

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 micromol 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 approximately 0.2 micromol 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.
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PMID:Na+ translocation by the NADH:ubiquinone oxidoreductase (complex I) from Klebsiella pneumoniae. 1041 49

The electrogenic NADH:Q oxidoreductase from the enterobacterium Klebsiella pneumoniae transports Na(+) ions. The complex was purified with an increase of the specific Na(+) transport activity from 0.2 micromol min(-1) mg(-1) in native membrane vesicles to 4.7 micromol min(-1) mg(-1) in reconstituted enzyme specimens. The subunit pattern resembled that of complex I from Escherichia coli, and two prominent polypeptides were identified as the NuoF and NuoG subunits of complex I. During purification the typical cofactors of complex I were enriched to yield approximately 17 nmol mg(-1) iron, 24 nmol mg(-1) acid-labile sulfide, and 0.79 nmol mg(-1) FMN in the purified sample. The enzyme contained approximately 1.2 nmol mg(-1) Q6 and 1.5 nmol mg(-1) Q8. The reduction of ubiquinone by NADH was Na(+)-dependent, which indicates coupling of the chemical and the vectorial reaction of the pump. The Na(+) activation profile corresponded to the Hill equation with a Hill coefficient K(H)(Na(+)) = 1.96 and with a half-maximal saturation at 0.33 mm Na(+). The reconstituted complex I from Klebsiella pneumoniae catalyzed deamino-NADH oxidation, Q1 reduction, and Na(+) translocation with specific activities of 2.6 units mg(-1), 2.4 units mg(-1), and 4.7 units mg(-1), respectively, which indicate a Na(+)/electron stoichiometry of one.
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PMID:The respiratory complex I (NDH I) from Klebsiella pneumoniae, a sodium pump. 1211 Jun 77

The modular evolutionary origin of NADH:ubiquinone oxidoreductase (complex I) provides useful insights into its functional organization. Iron-sulfur cluster N2 and the PSST and 49 kDa subunits were identified as key players in ubiquinone reduction and proton pumping. Structural studies indicate that this 'catalytic core' region of complex I is clearly separated from the membrane. Complex I from Escherichia coli and Klebsiella pneumoniae was shown to pump sodium ions rather than protons. These new insights into structure and function of complex I strongly suggest that proton or sodium pumping in complex I is achieved by conformational energy transfer rather than by a directly linked redox pump.
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PMID:Proton pumping by NADH:ubiquinone oxidoreductase. A redox driven conformational change mechanism? 1278 86

The NADH:ubiquinone oxidoreductase (complex I) couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. Recently, it was demonstrated that complex I from Klebsiella pneumoniae translocates sodium ions instead of protons. Experimental evidence suggested that complex I from the close relative Escherichia coli works as a primary sodium pump as well. However, data obtained with whole cells showed the presence of an NADH-induced electrochemical proton gradient. In addition, Fourier transform IR spectroscopy demonstrated that the redox reaction of the E. coli complex I is coupled to a protonation of amino acids. To resolve this contradiction we measured the properties of isolated E. coli complex I reconstituted in phospholipids. We found that the NADH:ubiquinone oxidoreductase activity did not depend on the sodium concentration. The redox reaction of the complex in proteoliposomes caused a membrane potential due to an electrochemical proton gradient as measured with fluorescent probes. The signals were sensitive to the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), the inhibitors piericidin A, dicyclohexylcarbodi-imide (DCCD), and amiloride derivatives, but were insensitive to the sodium ionophore ETH-157. Furthermore, monensin acting as a Na(+)/H(+) exchanger prevented the generation of a proton gradient. Thus, our data demonstrated that the E. coli complex I is a primary electrogenic proton pump. However, the magnitude of the pH gradient depended on the sodium concentration. The capability of complex I for secondary Na(+)/H(+) antiport is discussed.
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PMID:The Escherichia coli NADH:ubiquinone oxidoreductase (complex I) is a primary proton pump but may be capable of secondary sodium antiport. 1497 Feb 14

The energy-converting NADH:ubiquinone oxidoreductase, also known as respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with the translocation of ions across the membrane. It was assumed that the complex exclusively works as a proton pump. Recently, it has been proposed that complex I from Klebsiella pneumoniae and Escherichia coli work as Na+ pumps. We have used an E. coli complex I preparation to determine the type of ion(s) translocated by means of enzyme activity, generation of a membrane potential and redox-induced Fourier-transform infrared spectroscopy. We did not find any indications for Na+ translocation by the E. coli complex I.
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PMID:Ion translocation by the Escherichia coli NADH:ubiquinone oxidoreductase (complex I). 1604 10

Twenty percent of genes that encode for hypothetical proteins from Klebsiella pneumoniae MGH78578 were identified, leading to KPN00728 and KPN00729 after bioinformatics analysis. Both open reading frames showed high sequence homology to Succinate dehydrogenase Chain C (SdhC) and D (SdhD) from Escherichia coli. Recently, KPN00729 was assigned as SdhD. KPN00728 thus remains of particular interest as no annotated genes from the complete genome sequence encode for SdhC. We discovered KPN00728 has a missing region with conserved residues important for ubiquinone (UQ) and heme group binding. Structure and function prediction of KPN00728 coupled with secondary structure analysis and transmembrane topology showed KPN00728 adopts SDH-(subunit C)-like structure. To further probe its functionality, UQ was docked on the built model (consisting KPN00728 and KPN00729) and formation of hydrogen bonds between UQ and Ser27, Arg31 (KPN00728) and Tyr84 (KPN00729) further reinforces and supports that KPN00728 is indeed SDH. This is the first report on the structural and function prediction of KPN00728 of K. pneumoniae MGH78578 as SdhC.
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PMID:Why hypothetical protein KPN00728 of Klebsiella pneumoniae should be classified as chain C of succinate dehydrogenase? 1985 92

In bacteria, adaptive response to external stimuli is often regulated by small RNAs (sRNAs). In Escherichia coli, the organism in which sRNAs have been best characterized so far, no function could be attributed to 40 out of 79 sRNAs. Here we decipher the function of RybA, one of these orphan sRNAs. RybA was discovered in 2001 by Wassarman et al. using comparative genomics. This sRNA is conserved between E. coli, Salmonella typhimurium and Klebsiella pneumoniae. We determined the expression pattern of RybA under different growth conditions and identified its exact 5' and 3' ends. Using microarray and Northern analysis we show that, under peroxide stress, the absence of RybA leads to an upregulation of key genes of the TyrR regulon involved in the metabolism of aromatic compounds including the aromatic amino acids. Although containing an open reading frame, which might have an independent function, RybA does not require translation for this activity and therefore acts at the RNA level. Furthermore we demonstrate that regulation requires the transcription regulator TyrR. The mechanism of activation of TyrR, probably the primary target of RybA, remains to be elucidated. The downregulation of aromatic amino acid biosynthesis might regulate the cellular concentration of chorismate and its availability for other downstream products like ubiquinone or enterobactin. While ubiquinone participates in the defense against oxidative stress in the cytoplasmic membrane, enterobactin is involved in iron import and is therefore detrimental under oxidative stress.
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PMID:The small RNA RybA regulates key-genes in the biosynthesis of aromatic amino acids under peroxide stress in E. coli. 2233 64


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