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

Klebsiella pneumoniae (Aerobacter aerogenes) ATCC 8724 was able to grow anaerobically on 1,2-propanediol and 1,2-ethanediol as carbon and energy sources. Whole cells of the bacterium grown anaerobically on 1,2-propanediol or on glycerol catalyzed conversion of 1,2-diols and aldehydes to the corresponding acids and alcohols. Glucose-grown cells also converted aldehydes, but not 1,2-diols, to acids and alcohols. The presence of activities of coenzyme B(12)-dependent diol dehydratase, alcohol dehydrogenase, coenzyme-A-dependent aldehyde dehydrogenase, phosphotransacetylase, and acetate kinase was demonstrated with crude extracts of 1,2-propanediol-grown cells. The dependence of the levels of these enzymes on growth substrates, together with cofactor requirements in in vitro conversion of these substrates, indicates that 1,2-diols are fermented to the corresponding acids and alcohols via aldehydes, acyl-coenzyme A, and acyl phosphates. This metabolic pathway for 1,2-diol fermentation was also suggested in some other genera of Enterobacteriaceae which were able to grow anaerobically on 1,2-propanediol. When the bacteria were cultivated in a 1,2-propanediol medium not supplemented with cobalt ion, the coenzyme B(12)-dependent conversion of 1,2-diols to aldehydes was the rate-limiting step in this fermentation. This was because the intracellular concentration of coenzyme B(12) was very low in the cells grown in cobalt-deficient medium, since the apoprotein of diol dehydratase was markedly induced in the cells grown in the 1,2-propanediol medium. Better cell yields were obtained when the bacteria were grown anaerobically on 1,2-propanediol. Evidence is presented that aerobically grown cells have a different metabolic pathway for utilizing 1,2-propanediol.
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PMID:Fermentation of 1,2-propanediol with 1,2-ethanediol by some genera of Enterobacteriaceae, involving coenzyme B12-dependent diol dehydratase. 37 59

Structural and chemical properties of a flavodoxin from Anabaena PCC 7119 are described. The first 36 residues of the amino-terminal amino acid sequence have been determined and show extensive homology with flavodoxins isolated from other sources. Anabaena flavodoxin exhibits a net negative change (-3) in the helix-1 segment as found with other cyanobacterial flavodoxins Synechococcus 6301 (Anacystis nidulans) and Nostoc MAC, but in contrast to the net positive charge found in this region in the case of flavodoxins isolated from nitrogen-fixing bacteria (Azotobacter and Klebsiella). The FMN cofactor can be reversibly resolved from the apoprotein by trichloroacetic acid treatment. Apoflavodoxin, thus prepared, binds FMN with a Kd value of 0.1 nM and binds riboflavin with a decreased affinity (Kd = 5 microM) at pH 7.2. The apoprotein is stable in dilute solutions at pH values around 7 but readily denatures at pH 8 as judged from loss in flavin-binding ability and by ultraviolet circular dichroism spectroscopy. Oxidation-reduction potential studies at pH values of 7 and 8 show OX/SQ couples of -195 mV and -255 mV, respectively, and show SQ/HQ couples of -390 mV and -418 mV, respectively. From these data, the binding constant for the FMN semiquinone is calculated to be approx. 5-fold tighter and the binding of the FMN hydroquinone is approx. 10(5)-fold weaker than that of the oxidized FMN to the apoprotein. Anabaena flavodoxin functions as an effective mediator of electron transfer from ferredoxin-NADP(+)-reductase to cytochrome c with a turnover number [4.5-5) x 10(3) min-1); a values similar to that determined for Anabaena ferredoxin. The flavodoxin binds tightly to the reductase with Kd values of 6.4 and 8.5 microM at pH values of 7.0 and 8.0, respectively.
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PMID:Structural and chemical properties of a flavodoxin from Anabaena PCC 7119. 211 31

A binary plasmid system was used to produce nitrogenase components in Escherichia coli and subsequently to define a minimum set of nitrogen fixation (nif) genes required for the production of the iron-molybdenum cofactor (FeMoco) reactivatable apomolybdenum-iron (apoMoFe) protein of nitrogenase. The active MoFe protein is an alpha 2 beta 2 tetramer containing two FeMoco clusters and 4 Fe4S4 P centers (for review see, Orme-Johnson, W.H. (1985) Annu. Rev. Biophys. Biophys. Chem. 14, 419-459). The plasmid pVL15, carrying a tac-promoted nifA activator gene, was coharbored in E. coli with the plasmid pGH1 which contained nifHDKTYENXUSVWZMF' derived from the chromosome of the nitrogen fixing bacterium Klebsiella pneumoniae. The apoMoFe protein produced in E. coli by pGH1 + VL15 was identical to the apoprotein in derepressed cells of the nifB- mutant of K. pneumoniae (UN106) in its electrophoretic properties on nondenaturing polyacrylamide gels as well as in its ability to be activated by FeMoco. The constituent peptides migrated identically to those from purified MoFe protein during electrophoresis on denaturing gels. The concentrations of apoMoFe protein produced in nif-transformed strains of E. coli were greater than 50% of the levels of MoFe protein observed in derepressed wild-type K. pneumoniae. Systematic deletion of individual nif genes carried by pGH1 has established the requirements for the maximal production of the FeMoco-reactivatable apoMoFe protein to be the following gene products, NifHDKTYUSWZM+A. It appears that several of the genes (nifT, Y, U, W, and Z) are only required for maximal production of the apoMoFe protein, while others (nifH, D, K, and S) are absolutely required for synthesis of this protein in E. coli. One curious result is that the nifH gene product, the peptide of the Fe protein, but not active Fe protein itself, is required for formation of the apoMoFe protein. This suggests the possibility of a ternary complex of the NifH, D, and K peptides as the substrate for the processing to form the apoMoFe protein. We also find that nifM, the gene which processes the nifH protein into Fe protein (Howard, K.S., McLean, P.A., Hansen, F. B., Lemley, P.V., Kobla, K.S. & Orme-Johnson, W.H. (1986) J. Biol. Chem. 261, 772-778) can, under certain circumstances, partially replace other processing genes (i.e. nifTYU and/or WZ) although it is not essential for apoMoFe protein formation. It also appears that nifS and nifU, reported to play a role in Fe protein production in Azotobacter vinelandii, play no such role in K. pneumoniae, although these genes are involved in apoMoFe formation.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Genes required for formation of the apoMoFe protein of Klebsiella pneumoniae nitrogenase in Escherichia coli. 220 91

Four analogs of adenosylcobalamin (AdoCbl) modified in the D-ribose moiety of the Co beta ligand were synthesized, and their coenzymic properties were studied with diol dehydratase of Klebsiella pneumoniae ATCC 8724. 2'-Deoxyadenosylcobalamin (2'-dAdoCbl) and 3'-deoxyadenosylcobalamin (3'-dAdoCbl) were active as coenzyme. 2',3'-Secoadenosylcobalamin (2',3'-secoAdoCbl), an analog bearing the same functional groups as AdoCbl but nicked between the 2' and 3' positions in the ribose moiety, and its 2',3'-dialdehyde derivative (2',3'-secoAdoCbl dialdehyde) were totally inactive analogs of the coenzyme. It is therefore evident that the beta-D-ribofuranose ring itself, possibly its rigid structure, is essential and much more important than the functional groups of the ribose moiety for coenzymic function (relative importance: beta-D-ribofuranose ring much greater than 3'-OH greater than 2'-OH greater than ether group). With 2'-dAdoCbl and 3'-dAdoCbl as coenzymes, an absorption peak at 478 nm appeared during enzymatic reaction, suggesting homolysis of the C-Co bond to form cob(II)alamin as intermediate. In the absence of substrate, the complexes of the enzyme with these active analogs underwent rapid inactivation by oxygen. This suggests that their C-Co bond is activated even in the absence of substrate by binding to the apoprotein. No significant spectral changes were observed with 2',3'-secoAdoCbl upon binding to the apoenzyme. In contrast, spectroscopic observation indicates that 2'3'-secoAdoCbl dialdehyde, another inactive analog, underwent gradual and irreversible cleavage of the C-Co bond by interaction with the apodiol dehydratase, forming the enzyme-bound cob(II)alamin without intermediates.
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PMID:Roles of the beta-D-ribofuranose ring and the functional groups of the D-ribose moiety of adenosylcobalamin in the diol dehydratase reaction. 312 37

Adeninylethylcobalamin (AdeEtCbl) underwent cleavage of the C-Co bond by interaction with apoprotein of diol dehydrase from Klebsiella pneumoniae ATCC 8724, although this analog was quite inactive as coenzyme. Spectroscopic observation indicates that AdeEtCbl was converted to the enzyme-bound hydroxocobalamin without intermediates. The conversion was stoichiometric (1:1) and obeyed the second-order reaction kinetics (k = 0.027 min-1 microM-1 at 37 degrees C) depending upon concentrations of apoprotein and AdeEtCbl. This suggests that the complex formation is the rate-determining step and that AdeEtCbl undergoes rapid C-Co bond cleavage once it binds to the apoenzyme. Substrates and oxygen did apparently not affect the rate of the C-Co bond cleavage. The experiments using [adenine-U-14C]AdeEtCbl and [1(3)-3H]glycerol demonstrated that 9-ethyladenine was the only product formed from the adeninylethyl group of AdeEtCbl during the conversion and that an additional hydrogen atom in the 9-ethyladenine is not derived from the substrate. 1H NMR measurement of the 9-ethyladenine formed enzymatically from AdeEtCbl and DL-1,2-[1,1,2-2H3]propanediol also led to the same conclusion. All of these results indicate that the C-Co bond of AdeEtCbl is activated by diol dehydrase and undergoes heterolysis forming Co(III) and a carbanion or a carbanion-like species, in clear contrast to the homolysis of the C-Co bond of adenosylcobalamin in the normal catalytic process. 9-Ethyladenine formed remained tightly associated with the enzyme. Longer chain homologs, i.e. adeninylpropylcobalamin, adeninylbutylcobalamin, and adeninylpentylcobalamin did not undergo such cleavage of the C-Co bond by diol dehydrase.
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PMID:Activation and cleavage of the carbon-cobalt bond of adeninylethylcobalamin by diol dehydrase. 329 36

Urease (urea amidohydrolase; EC 3.5.1.5) catalyzes the hydrolysis of urea to yield ammonia and carbamate. The latter compound spontaneously decomposes to yield another molecule of ammonia and carbonic acid. The urease phenotype is widely distributed across the bacterial kingdom, and the gene clusters encoding this enzyme have been cloned from numerous bacterial species. The complete nucleotide sequence, ranging from 5.15 to 6.45 kb, has been determined for five species including Bacillus sp. strain TB-90, Klebsiella aerogenes, Proteus mirabilis, Helicobacter pylori, and Yersinia enterocolitica. Sequences for selected genes have been determined for at least 10 other bacterial species and the jack bean enzyme. Urease synthesis can be nitrogen regulated, urea inducible, or constitutive. The crystal structure of the K. aerogenes enzyme has been determined. When combined with chemical modification studies, biophysical and spectroscopic analyses, site-directed mutagenesis results, and kinetic inhibition experiments, the structure provides important insight into the mechanism of catalysis. Synthesis of active enzyme requires incorporation of both carbon dioxide and nickel ions into the protein. Accessory genes have been shown to be required for activation of urease apoprotein, and roles for the accessory proteins in metallocenter assembly have been proposed. Urease is central to the virulence of P. mirabilis and H. pylori. Urea hydrolysis by P. mirabilis in the urinary tract leads directly to urolithiasis (stone formation) and contributes to the development of acute pyelonephritis. The urease of H. pylori is necessary for colonization of the gastric mucosa in experimental animal models of gastritis and serves as the major antigen and diagnostic marker for gastritis and peptic ulcer disease in humans. In addition, the urease of Y. enterocolitica has been implicated as an arthritogenic factor in the development of infection-induced reactive arthritis. The significant progress in our understanding of the molecular biology of microbial ureases is reviewed.
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PMID:Molecular biology of microbial ureases. 756 14

In vivo activation of Klebsiella aerogenes urease, a nickel-containing enzyme, requires the presence of functional UreD, UreF, and UreG accessory proteins and is further facilitated by UreE. These accessory proteins are proposed to be involved in metallocenter assembly (M. H. Lee, S. B. Mulrooney, M. J. Renner, Y. Markowicz, and R. P. Hausinger, J. Bacteriol. 174:4324-4330, 1992). A series of three UreD-urease apoprotein complexes are present in cells that express ureD at high levels, and these complexes are thought to be essential for in vivo activation of the enzyme (I.-S. Park, M. B. Carr, and R. P. Hausinger, Proc. Natl. Acad. Sci. USA 91:3233-3237, 1994). In this study, we describe the effect of accessory gene deletions on urease complex formation. The ureE, ureF, and ureG gene products were found not to be required for formation of the UreD-urease complexes; however, the complexes from the ureF deletion mutant exhibited delayed elution during size exclusion chromatography. Because these last complexes were of typical UreD-urease sizes according to native gel electrophoretic analysis, we propose that UreF alters the conformation of the UreD-urease complexes. The same studies revealed the presence of an additional series of urease apoprotein complexes present only in cells containing ureD, ureF, and ureG, along with the urease subunit genes. These new complexes were shown to contain urease, UreD, UreF, and UreG. We propose that the UreD-UreF-UreG-urease apoprotein complexes represent the activation-competent form of urease apoprotein in the cell.
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PMID:Evidence for the presence of urease apoprotein complexes containing UreD, UreF, and UreG in cells that are competent for in vivo enzyme activation. 772 85

Assembly of protein metallocenters is not well understood. Urease offers a tractable system for examination of this process. Formation of the urease metallocenter in vivo is known to require four accessory proteins: UreD, postulated to be a urease-specific molecular chaperone; UreE, a nickel(II)-binding protein; and UreF and UreG, of unknown function. Activation of purified Klebsiella aerogenes urease apoprotein was accomplished in vitro by providing carbon dioxide (half-maximal activation at approximately 0.2 percent carbon dioxide) in addition to nickel ion. Activation coincided with carbon dioxide incorporation into urease in a pH-dependent reaction (pKa > or = 9, where Ka is the acid constant). The concentration of carbon dioxide also affected the amount of activation of UreD-urease apoprotein complexes. These results suggest that carbon dioxide binding to urease apoprotein generates a ligand that facilitates productive nickel binding.
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PMID:Requirement of carbon dioxide for in vitro assembly of the urease nickel metallocenter. 785 93

The formation of active urease in Klebsiella aerogenes requires the presence of three structural genes for the apoprotein (ureA, ureB, and ureC), as well as four accessory genes (ureD, ureE, ureF, and ureG) that are involved in functional assembly of the metallocenter in this nickel-containing enzyme. Slow and partial activation of urease apoprotein was observed after addition of nickel ion to extracts of Escherichia coli cells bearing a plasmid containing the K. aerogenes urease gene cluster or derivatives of this plasmid with deletions in ureE, ureF, or ureG. In contrast, extracts of cells containing a ureD deletion derivative failed to generate active urease, thus highlighting a key role for UreD in the metallocenter assembly process. Site-directed mutagenesis methods were used to overexpress ureD in the presence of the other urease genes, and the UreD protein was found to copurify with urease. A molecule of native urease apoprotein is capable of binding 0, 1, 2, or 3 molecules of UreD, consistent with a trimeric structure of urease catalytic units. The UreD-urease apoprotein complexes are competent for activation by nickel, with the level of activity obtained being directly related to the number of UreD molecules bound per urease molecule. Activation of the UreD-urease complexes is rapid and accompanied by UreD dissociation. We propose that UreD is a chaperone protein which stabilizes a urease apoprotein conformation that is competent for nickel incorporation.
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PMID:In vitro activation of urease apoprotein and role of UreD as a chaperone required for nickel metallocenter assembly. 790 61

The cysB gene of Klebsiella aerogenes has been cloned, sequenced and shown to complement the cysteine auxotrophic phenotype of Escherichia coli cysB mutants. The K. aerogenes cysB gene is predicted to encode a protein of 324 amino acid residues that shares approx. 95% sequence similarity with the Salmonella typhimurium and E. coli CysB proteins. Gel-retardation assays demonstrate that the purified protein binds to DNA fragments containing either the K. aerogenes cysb promoter or the S. typhimurium cysJIH promoter. Acetylserine enhances CysB binding to the cysJIH promoter fragment while diminishing its binding to the cysB promoter fragment. Fluorescence-emission-spectroscopy measurements suggest strongly that N-acetylserine binds to CysB apoprotein but that O-acetylserine does not, and support the notion that N-acetylserine is the physiological inducer of cysteine biosynthesis.
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PMID:Characterization of the CysB protein of Klebsiella aerogenes: direct evidence that N-acetylserine rather than O-acetylserine serves as the inducer of the cysteine regulon. 816 30

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