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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The O-side-chain polysaccharide in the lipopolysaccharide of Klebsiella pneumoniae O1 is based on a backbone structure of repeat units of [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]; this structure is termed D-galactan I. The rfb (O-antigen biosynthesis) gene cluster directs the synthesis of D-galactan I and consists of six genes termed rfbA-FKPO1. In this paper we show that rfbDKPO1 encodes a UDP-galactopyranose mutase (NAD(P)H-requiring) (EC 5.4.99. 9), which forms uridine 5'-(trihydrogen diphosphate) P'-alpha-D-galactofuranosyl ester (UDP-Galf), the biosynthetic precursor of galactofuranosyl residues. The deduced amino acid sequence of rfbDKPO1 shows 85% and 37.5% identity to the rfbDKPO8 gene of K. pneumoniae serotype O8 and the glf gene of Escherichia coli, respectively. The molecular mass of the purified RfbDKPO1 enzyme is 45 kDa as determined by SDS-polyacrylamide gel electrophoresis, while gel filtration revealed a molecular mass of 92 kDa, suggesting a dimeric structure for the native protein. The rfbDKPO1 gene product interconverts uridine 5'-(trihydrogen diphosphate) P'-alpha-D-galactopyranosyl ester (UDP-Galp) and UDP-Galf. Unlike Glf, RfbDKPO1 showed a requirement for NADH or NADPH, which could not be replaced by NAD or NADP. RfbDKPO1 was used to synthesize milligram quantities of UDP-Galf, allowing this compound to be purified and fully characterized in an intact form for the first time. The structure of UDP-Galf was proven by NMR spectroscopy.
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PMID:UDP-galactofuranose precursor required for formation of the lipopolysaccharide O antigen of Klebsiella pneumoniae serotype O1 is synthesized by the product of the rfbDKPO1 gene. 902 Jan 23

Several species of enterobacteria are able to utilize citrate as carbon and energy source. Under oxic conditions in the presence of a functional tricarboxylic acid cycle, growth on this compound solely depends on an appropriate transport system. During anaerobiosis, when 2-oxoglutarate dehydrogenase is repressed, some species such as Klebsiella pneumoniae and Salmonella typhimurium, but not Escherichia coli, are capable of growth on citrate by a Na+-dependent pathway forming acetate, formate, and CO2 as products. During the last decade, several novel features associated with this type of fermentation have been discovered in K. pneumoniae. The biotin protein oxaloacetate decarboxylase, one of the key enzymes of the pathway besides citrate lyase, is a Na+ pump. Recently it has been shown that the proton required for the decarboxylation of carboxybiotin is taken up from the side to which Na+ ions are pumped, and a membrane-embedded aspartate residue that is probably involved both in Na+ and in H+ transport was identified. The Na+ gradient established by oxaloacetate decarboxylase drives citrate uptake via CitS, a homodimeric carrier protein with a simultaneous-type reaction mechanism, and NADH formation by reversed electron transfer involving formate dehydrogenase, quinone, and a Na+-dependent NADH:quinone oxidoreductase. All enzymes specifically required for citrate fermentation are induced under anoxic conditions in the presence of citrate and Na+ ions. The corresponding genes form a cluster on the chromosome and are organized as two divergently transcribed operons. Their co-ordinate expression is dependent on a two-component system consisting of the sensor kinase CitA and the response regulator CitB. The citAB genes are part of the cluster and are positively autoregulated. In addition to CitA/CitB, the cAMP receptor protein (Crp) is involved in the regulation of the citrate fermentation enzymes, subjecting them to catabolite repression.
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PMID:Anaerobic citrate metabolism and its regulation in enterobacteria. 913 29

During anaerobic growth of Klebsiella pneumoniae on citrate, 9.4 mmol of H2/mol of citrate (4-kPa partial pressure) was formed at the end of growth besides acetate, formate, and CO2. Upon addition of NiCl2 (36 microM) to the growth medium, hydrogen formation increased about 36% to 14.8 mmol/mol of citrate (6 kPa), and the cell yield increased about 15%. Cells that had been harvested and washed under anoxic conditions exhibited an H2-dependent formation of NAD(P)H in vivo. The reduction of internal NAD(P)+ was also achieved by the addition of formate. In crude extracts, the H2:NAD+ oxidoreductase activity was 0.13 micromol min-1 mg-1, and 76% of this activity was found in the washed membrane fraction. The highest specific activities of the membrane fraction were observed in 50 mM potassium phosphate, with 1.6 micromol of NADPH formed min-1 mg-1 at pH 7.0 and 1.7 micromol of NADH formed min-1 mg-1 at pH 9.5. In the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone and the Na+/H+ antiporter monensin, the H2-dependent reduction of NAD+ by membrane vesicles decreased only slightly (about 16%). The NADP+- or NAD+-reducing hydrogenases were solubilized from the membranes with the detergent lauryldimethylamine-N-oxide or Triton X-100. NAD(P)H formation with H2 as electron donor, therefore, does not depend on an energized state of the membrane. It is proposed that hydrogen which is formed by K. pneumoniae during citrate fermentation is recaptured by a novel membrane-bound, oxygen-sensitive H2:NAD(P)+ oxidoreductase that provides reducing equivalents for the synthesis of cell material.
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PMID:A membrane-bound NAD(P)+-reducing hydrogenase provides reduced pyridine nucleotides during citrate fermentation by Klebsiella pneumoniae. 986 36

1,2-Propanediol (1,2-PD) is a major commodity chemical that is currently derived from propylene, a nonrenewable resource. A goal of our research is to develop fermentation routes to 1,2-PD from renewable resources. Here we report the production of enantiomerically pure R-1,2-PD from glucose in Escherichia coli expressing NADH-linked glycerol dehydrogenase genes (E. coli gldA or Klebsiella pneumoniae dhaD). We also show that E. coli overexpressing the E. coli methylglyoxal synthase gene (mgs) produced 1,2-PD. The expression of either glycerol dehydrogenase or methylglyoxal synthase resulted in the anaerobic production of approximately 0.25 g of 1,2-PD per liter. R-1,2-PD production was further improved to 0.7 g of 1,2-PD per liter when methylglyoxal synthase and glycerol dehydrogenase (gldA) were coexpressed. In vitro studies indicated that the route to R-1,2-PD involved the reduction of methylglyoxal to R-lactaldehyde by the recombinant glycerol dehydrogenase and the reduction of R-lactaldehyde to R-1, 2-PD by a native E. coli activity. We expect that R-1,2-PD production can be significantly improved through further metabolic and bioprocess engineering.
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PMID:Metabolic engineering of a 1,2-propanediol pathway in Escherichia coli. 1004 80

The respiratory system of a cyanide-resistant Klebsiella oxytoca was analyzed by monitoring the changes in the cytochrome contents in response to various inhibitors in the presence of various concentrations of cyanide. The cells grown in the medium without cyanide (KCN) have two terminal oxidases, cytochrome d (Ki = 10(-5) M KCN) and o (Ki = 10(-3) M KCN). When cells were grown on medium with 1 mM KCN, the expression of both b-type cytochrome and cytochrome d in the plasma membranes of the cell decreased by more than 50%, while cytochrome o increased by 70%, as compared with the cells grown in the absence of KCN. Two terminal oxidases with Ki values of about 10(-3) M and 1.7 x 10(-2) M KCN were observed in the plasma membrane fractions of the cells growing on KCN enriched medium. 2-n-Heptyl-4-hydroxyquinoline-N-oxide markedly inhibited the oxidation of NADH by the plasma membranes from the cells grown in the medium without KCN, but not in those plasma membranes from KCN-grown cells. The NADH oxidases in plasma membranes of K. oxytoca grown with and without KCN were equally sensitive to UV irradiation. Adding freshly isolated quinone to the UV-damaged plasma membranes restored the NADH oxidase activity from both types of plasma membranes. From these results, we propose the presence of a non-heme type of terminal oxidase to account for the KCN resistance in K. oxytoca.
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PMID:The respiratory responses to cyanide of a cyanide-resistant Klebsiella oxytoca bacterial strain. 1036 7

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

A mutant ribitol dehydrogenase (RDH-F) was purified from Klebsiella aerogenes strain F which evolved from the wild-type strain A under selective pressure to improve growth on xylitol, a poor substrate used as sole carbon source. The ratio of activities on xylitol (500 mM) and ribitol (50 mM) was 0.154 for RDH-F compared to 0.033 for the wild-type (RDH-A) enzyme. The complete amino acid sequence of RDH-F showed the mutations. Q60 for E60 and V215 for L215 in the single polypeptide chain of 249 amino acid residues. Structural modeling based on homologies with two other microbial dehydrogenases suggests that E60 --> Q60 is a neutral mutation, since it lies in a region far from the catalytic site and should not cause structural perturbations. In contrast, L215 --> V215 lies in variable region II and would shift a loop that interacts with the NADH cofactor. Another improved ribitol dehydrogenase, RDH-D, contains an A196 --> P196 mutation that would disrupt a surface alpha-helix in region II. Hence conformational changes in this region appear to be responsible for the improved xylitol specificity.
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PMID:The amino acid sequence of ribitol dehydrogenase-F, a mutant enzyme with improved xylitol dehydrogenase activity. 1044 46

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.
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PMID:Na+ translocation by complex I (NADH:quinone oxidoreductase) of Escherichia coli. 1065 3

The current knowledge on the Na(+)-translocating NADH:ubiquinone oxidoreductase of the Na(+)-NQR type from Vibrio alginolyticus, and on Na(+) transport by the electrogenic NADH:Q oxidoreductases from Escherichia coli and Klebsiella pneumoniae (complex I, or NDH-I) is summarized. A general mode of redox-linked Na(+) transport by NADH:Q oxidoreductases is proposed that is based on the electrostatic attraction of a positively charged Na(+) towards a negatively charged, enzyme-bound ubisemiquinone anion in a medium of low dielectricity. A structural model of the [2Fe-2S]- and FAD-carrying NqrF subunit of the Na(+)-NQR from V. alginolyticus based on ferredoxin and ferredoxin:NADP(+) oxidoreductase suggests that a direct participation of the Fe/S center in Na(+) transport is rather unlikely. A ubisemiquinone-dependent mechanism of Na(+) translocation is proposed that results in the transport of two Na(+) ions per two electrons transferred. Whereas this stoichiometry of the pump is in accordance with in vivo determinations of Na(+) transport by the respiratory chain of V. alginolyticus, higher (Na(+) or H(+)) transport stoichiometries are expected for complex I, suggesting the presence of a second coupling site.
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PMID:Na(+) translocation by bacterial NADH:quinone oxidoreductases: an extension to the complex-I family of primary redox pumps. 1124 88

Eukaryotic complex I integrated into the respiratory chain transports at least 4 H+ per NADH oxidized. Recent results indicate that the cation selectivity is altered to Na+ in complex I (NDH I) isolated from the enterobacteria Escherichia coli and Klebsiella pneumoniae. A sequence analysis illustrates the characteristic differences of the enterobacterial, Na+-translocating NDH I compared to the H+-translocating complex I from mitochondria. Special attention is given to the membranous NuoL (ND5, Nqo12) subunits that possess striking sequence similarities to secondary Na+/H+ antiporters and are proposed to participate in Na+ transport. A model of redox-linked Na+ (or H+) transport by complex I is discussed based on the ion-pair formation of a negatively charged ubisemiquinone anion with a positively charged Na+ (or H+).
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PMID:The Na+-translocating NADH:quinone oxidoreductase (NDH I) from Klebsiella pneumoniae and Escherichia coli: implications for the mechanism of redox-driven cation translocation by complex I. 1169 27


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