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 lyase (EC 4.1.3.6) catalyzes the cleavage of citrate to acetate and oxaloacetate and is composed of three subunits (alpha, beta, and gamma). The gamma-subunit serves as an acyl carrier protein (ACP) and contains the prosthetic group 2'-(5' '-phosphoribosyl)-3'-dephospho-CoA, which is attached via a phosphodiester linkage to serine-14 in the enzyme from Klebsiella pneumoniae. In this work, we demonstrate by genetic and biochemical studies with citrate lyase of Escherichia coli and K. pneumoniae that the conversion of apo-ACP into holo-ACP is dependent on the two proteins, CitX (20 kDa) and CitG (33 kDa). In the absence of CitX, only apo-ACP was synthesized in vivo, whereas in the absence of CitG, an adenylylated ACP was produced, with the AMP residue attached to serine-14. The adenylyltransferase activity of CitX could be verified in vitro with purified CitX and apo-ACP plus ATP as substrates. Besides ATP, CTP, GTP, and UTP also served as nucleotidyl donors in vitro, showing that CitX functions as a nucleotidyltransferase. The conversion of apo-ACP into holo-ACP was achieved in vitro by incubation of apo-ACP with CitX, CitG, ATP, and dephospho-CoA. ATP could not be substituted with GTP, CTP, UTP, ADP, or AMP. In the absence of CitG or dephospho-CoA, AMP-ACP was formed. Remarkably, it was not possible to further convert AMP-ACP to holo-ACP by subsequent incubation with CitG and dephospho-CoA. This demonstrates that AMP-ACP is not an intermediate during the conversion of apo- into holo-ACP, but results from a side activity of CitX that becomes effective in the absence of its natural substrate. Our results indicate that holo-ACP formation proceeds as follows. First, a prosthetic group precursor [presumably 2'-(5' '-triphosphoribosyl)-3'-dephospho-CoA] is formed from ATP and dephospho-CoA in a reaction catalyzed by CitG. Second, holo-ACP is formed from apo-ACP and the prosthetic group precursor in a reaction catalyzed by CitX.
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PMID:Biosynthesis of the prosthetic group of citrate lyase. 1092 39

Stable inactive 2 : 1 complexes of the Klebsiella pneumoniae nitrogenase components (Kp2/Kp1) were prepared with ADP or the fluorescent ADP analogue, 2'(3')-O-[N-methylanthraniloyl] ADP and AlF(4)(-) or BeF(3)(-) ions. By analogy with published crystallographic data [Schindelin et al. (1997) Nature 387, 370-376)], we suggest that the metal fluoride ions replaced phosphate at the two ATP-binding sites of the iron protein, Kp2. The beryllium (BeF(x)) and aluminium (AlF(4)(-)) containing complexes are proposed to correspond to the ATP-bound state and the hydrolytic transition states, respectively, by analogy with the equivalent complexes of myosin [Fisher et al. (1995) Biochemistry 34, 8960-8972]. (31)P NMR spectroscopy showed that during the initial stages of complex formation, MgADP bound to the complexed Kp2 in a manner similar to that reported for isolated Kp2. This process was followed by a second step that caused broadening of the (31)P NMR signals and, in the case of the AlF4- complex, slow hydrolysis of some of the excess ADP to AMP and inorganic phosphate. The purified BeFx complex contained 3.8 +/- 0.1 MgADP per mol Kp1. With the AlF(4)(-) complex, MgAMP and adenosine (from MgAMP hydrolysis) replaced part of the bound MgADP although four AlF(4)(-) ions were retained, demonstrating that full occupancy by MgADP is not required for the stability of the complex. The fluorescence emission maximum of 2'(3')-O-[N-methylanthraniloyl] ADP was blue-shifted by 6-8 nm in both metal fluoride complexes and polarization was 6-9 times that of the free analogue. The fluorescence yield of bound 2'(3')-O-[N-methylanthraniloyl] ADP was enhanced by 40% in the AlF(4)(-) complex relative to the solvent but no increase in fluorescence was observed in the BeFx complex. Resonance energy transfer from conserved tyrosine residues located in proximity to the Kp2 nucleotide-binding pocket was marked in the AlF(4)(-) complex but minimal in the BeFx fluoride complex, illustrating a clear conformational difference in the Fe protein of the two complexes. Our data indicate that complex formation during the nitrogenase catalytic cycle is a multistep process involving at least four conformational states of Kp2: similar to the free Fe protein; as initially complexed with detectable (31)P NMR; as detected in mature complexes with no detectable (31)P NMR; in the AlF(4)(-) complex in which an altered tyrosine interaction permits resonance energy transfer with 2'(3')-O-[N-methylanthraniloyl] ADP.
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PMID:Transition state complexes of the Klebsiella pneumoniae nitrogenase proteins. Spectroscopic properties of aluminium fluoride-stabilized and beryllium fluoride-stabilized MgADP complexes reveal conformational differences of the Fe protein. 1116 22

Klebsiella pneumoniae is able to grow anaerobically with citrate as a sole carbon and energy source by a fermentative pathway involving the Na(+)-dependent citrate carrier CitS, citrate lyase, and oxaloacetate decarboxylase. The corresponding genes are organized in the divergent citC and citS operons, whose expression is strictly dependent on the citrate-sensing CitA-CitB two-component system. Evidence is provided here that the citrate fermentation genes are subject to catabolite repression, since anaerobic cultivation with a mixture of citrate and glucose or citrate and gluconate resulted in diauxic growth. Glucose, gluconate, and also glycerol decreased the expression of a chromosomal citS-lacZ fusion by 60 to 75%, whereas a direct inhibition of the citrate fermentation enzymes was not observed. The purified cyclic AMP (cAMP) receptor protein (CRP) of K. pneumoniae bound to two sites in the citC-citS intergenic region, which were centered at position -41.5 upstream of the citC and citS transcriptional start sites. Binding was apparently stimulated by the response regulator CitB. These data indicate that catabolite repression of the citrate fermentation genes is exerted by CRP and that in the absence of repressing carbon sources the cAMP-CRP complex serves to enhance the basal, CitB-dependent transcription level.
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PMID:Catabolite repression of the citrate fermentation genes in Klebsiella pneumoniae: evidence for involvement of the cyclic AMP receptor protein. 1151 6

Local infection control measures, antibiotic consumption and patient demographics from 1999-2000 together with bacteriological analyses were investigated in 29 ICUs participating in the ICU-STRAMA programme. The median antibiotic consumption per ICU was 1147 (range 605-2143) daily doses per 1000 occupied bed d (DDD1000). Antibiotics to which > 90% of isolates of an organism were susceptible were defined as treatment alternatives (TA90). The mean number of TA90 was low (1-2 per organism) for Enterococcus faecium (vancomycin:VAN), coagulase negative staphylococci (VAN), Pseudomonas aeruginosa (ceftazidime:CTZ, netilmicin: NET) and Stenotrophomonas maltophilia (CTZ, trimethoprim-sulfamethoxazole: TSU), but higher (3-7) for Acinetobacter spp. (imipenem:IMI, NET, TSU), Enterococcus faecalis (ampicillin:AMP, IMI, VAN), Serratia spp. (ciprofloxacin:CIP, IMI, NET), Enterobacter spp. (CIP, IMI, NET, TSU), E. coli (cefuroxime:CXM, cefotaxime/eftazidime:CTX/CTZ, CIP, IMI, NET, piperacillin-tazobactam:PTZ, TSU), Klebsiella spp. (CTX/CTZ CIP, IMI, NET, PTZ, TSU) and Staphylococcus aureus (clindamycin, fusidic acid, NET, oxacillin, rifampicin, VAN). Of S. aureus isolates 2% were MRSA. Facilities for alcohol hand disinfection at each bed were available in 96% of the ICUs. The numbers of TA90 available were apparently higher than in ICUs in southern Europe and the US, despite a relatively high antibiotic consumption. This may be due to a moderate ecological impact of the used agents and the infection control routines in Swedish ICUs.
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PMID:High antibiotic susceptibility among bacterial pathogens in Swedish ICUs. Report from a nation-wide surveillance program using TA90 as a novel index of susceptibility. 1500 May 55

Inorganic polyphosphate (poly P), a polymer of tens or hundreds of phosphate residues linked by high-energy, ATP-like bonds, is found in all organisms and performs a wide variety of functions. Myxococcus xanthus, a social bacterium that feeds on other bacteria and forms fruiting bodies and spores, depends on poly P for motility, development, and nutritional predation. Two poly P metabolizing enzymes were studied in M. xanthus: poly P kinase 1, which synthesizes poly P reversibly from ATP, and poly P:AMP phosphotransferase, which uses poly P as a donor to also reversibly convert AMP to ADP. The null mutant of ppk1 is defective in social motility, overproduces pilin protein on the cell surface, is delayed in fruiting body formation, produces fewer spores, is delayed in germination, and forms far smaller plaques on a lawn of Klebsiella aerogenes. The pap mutant is also impaired in social motility, but shows only slightly reduced abilities in development and predation.
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PMID:Inorganic polyphosphate in the social life of Myxococcus xanthus: motility, development, and predation. 1617 37

MceIJ is a two protein complex responsible for attachment of a C-glycosylated and linearized derivative of enterobactin, an iron scavenger (siderophore) and product of nonribosomal peptide synthetase machinery, to the C-terminal serine residue of microcin E492 (MccE492), an 84 aa ribosomal antibiotic peptide produced by Klebsiella pneumoniae RYC492. The MceIJ-catalyzed formation of the glycosyl ester linkage between MccE492 and the siderophore requires ATP and Mg(II) as cofactors. This work addresses the ATP utilization, mechanism of C-terminal carboxylate activation, and substrate scope of MceIJ. Formation of the ribosomal peptide-nonribosomal peptide linkage between the MccE492 C-terminal decapeptide and monoglycosylated enterobactin (MGE) requires cleavage of the alpha,beta bond of ATP and formation of a putative peptidyl-CO-AMP intermediate. Attack of the peptidyl-CO-AMP carbonyl by the deprotonated C4' hydroxyl of the glucose moiety forms a glycosyl ester linkage with release of AMP. Site-directed mutagenesis of the three cysteines and five histidines in MceI to alanines reveals that these residues are not required structurally or catalytically. MceIJ recognizes all glycosylated enterobactin derivatives formed by the MccE492 gene cluster members MceC ( C-glycosyltransferase) and MceD (esterase) in vitro and a MGE derivative lacking the C6' hydroxyl moiety. The protein complex also accepts and modifies the C-terminal decapeptide substrate fragments of the structurally related microcins H47, I47, and M. MccE492 C-terminal decapeptides bearing fluorescein and biotin moieties on the N-terminus are also substrates for MceIJ, which provides a route for the chemoenzymatic synthesis of enterobactin conjugates with peptide linkages.
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PMID:Investigations of the MceIJ-catalyzed posttranslational modification of the microcin E492 C-terminus: linkage of ribosomal and nonribosomal peptides to form "trojan horse" antibiotics. 1869 Jul 11

The capacity to both ferment and oxidize L-ascorbate has been widely documented for a number of enteric bacteria. Here we present evidence that all the strains of Klebsiella pneumoniae tested in this study ferment L-ascorbate using the ula regulon-encoded proteins. Under aerobic conditions, several phenotypes were observed for the strains. Our results showed that the yiaK-S system is required for this aerobic metabolic process. Gel shift experiments performed with UlaR and YiaJ and probes corresponding to the specific promoters indicated that L-ascorbate-6-phosphate is the effector molecule recognized by both regulators, since binding of the repressors to their recognition sites was impaired by the presence of this compound. We demonstrated that in K. pneumoniae cells L-ascorbate-6-phosphate is formed only by the action of the UlaABC phosphotransferase system. This finding explains why strains that lack the ula genetic system and therefore are unable to form the inducer intracellularly cannot efficiently use this vitamin as a carbon source under either anaerobic or aerobic conditions. Thus, efficient aerobic metabolism of L-ascorbate in K. pneumoniae is dependent on the presence of both the yiaK-S and ula systems. The expression of the yiaK-S operon, but not the expression of the ula regulon, is controlled by oxygen availability. Both systems are regulated by the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex and by IHF.
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PMID:The yiaKLX1X2PQRS and ulaABCDEFG gene systems are required for the aerobic utilization of L-ascorbate in Klebsiella pneumoniae strain 13882 with L-ascorbate-6-phosphate as the inducer. 1870 99

Escherichia coli strains, in general, do not ferment cellobiose and aryl-beta-D-glucosidic sugars, although "cryptic" beta-d-glucoside systems have been characterized. Here we describe an additional cryptic operon (bgc) for the utilization of cellobiose and the aryl-beta-d-glucosides arbutin and salicin at low temperature. The bgc operon was identified by the characterization of beta-glucoside-positive mutants of an E. coli septicemia strain (i484) in which the well-studied bgl (aryl-beta-d-glucoside) operon was deleted. These bgc* mutants appeared after 5 days of incubation on salicin indicator plates at 28 degrees C. The bgc operon codes for proteins homologous to beta-glucoside/cellobiose-specific phosphoenolpyruvate-dependent phosphotransfer system permease subunits IIB (BgcE), IIC (BgcF), and IIA (BgcI); a porin (BgcH); and a phospho-beta-D-glucosidase (BgcA). Next to the bgc operon maps the divergent bgcR gene, which encodes a GntR-type transcriptional regulator. Expression of the bgc operon is dependent on the cyclic-AMP-dependent regulator protein CRP and positively controlled by BgcR. In the bgc* mutants, a single nucleotide exchange enhances the activity of the bgc promoter, rendering it BgcR independent. Typing of a representative collection of E. coli demonstrated the prevalence of bgc in strains of phylogenetic group B2, representing mainly extraintestinal pathogens, while it is rare among commensal E. coli strains. The bgc locus is also present in the closely related species Escherichia albertii. Further, bioinformatic analyses demonstrated that homologs of the bgc genes exist in the enterobacterial Klebsiella, Enterobacter, and Citrobacter spp. and also in gram-positive bacteria, indicative of horizontal gene transfer events.
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PMID:Characterization of a beta-glucoside operon (bgc) prevalent in septicemic and uropathogenic Escherichia coli strains. 1923 52

Pathogenic bacteria constitute an important cause of hospital-acquired infections. However, the misuse of available bactericidal agents has led to the appearance of antibiotic-resistant strains. Thus, efforts to seek new antimicrobials with different action mechanisms would have an enormous impact. Here, a novel antimicrobial protein (SiAMP2) belonging to the 2S albumin family was isolated from Sesamum indicum kernels and evaluated against several bacteria and fungi. Furthermore, in silico analysis was conducted in order to identify conserved residues through other 2S albumin antimicrobial proteins (2S-AMPs). SiAMP2 specifically inhibited Klebsiella sp. Specific regions in the molecule surface where cationic (RR/RRRK) and hydrophobic (MEYWPR) residues are exposed and conserved were proposed as being involved in antimicrobial activity. This study reinforces the hypothesis that plant storage proteins might also play as pathogen protection providing an insight into the mechanism of action for this novel 2S-AMP and evolutionary relations between antimicrobial activity and 2S albumins.
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PMID:Bactericidal activity identified in 2S Albumin from sesame seeds and in silico studies of structure-function relations. 2169 71

CD spectroscopy was used to investigate the interactions of a series of synthetic AMPs with LPS isolated from Pseudomonas aeruginosa and Klebsiella pneumoniae, as well as with various phospholipids to better approximate the chemical composition of the membranes of these two strains of Gram-negative bacteria. This investigation was conducted in order to probe how the contributions of key physicochemical properties of an AMP vary in different regions of the membranes of these two bacteria. The conclusions from this study are as follows. (1) The binding interactions between the AMP and the membranes are defined by the complementarity of delocalization of positive charge density of the basic amino side chains (i.e., electrostatics), molecular flexibility of the peptide backbone, and overall hydrophobicity. (2) The binding interactions of these AMPs to LPS seem to be predominantly with the lipid A region of the LPS. (3) Incorporation of phospholipids into the LPS containing SUVs resulted in dramatic changes in the conformational equilibrium of the bound AMPs. (4) For the LPS-phospholipid models of Pseudomonas aeruginosa, delocalization of the side chain positive charge plays a major role in determining the number of conformers that contribute to the binding conformational equilibrium. This relationship was not observed for the models of the outer and inner membranes of Klebsiella pneumoniae.
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PMID:Spectroscopic investigations of the binding mechanisms between antimicrobial peptides and membrane models of Pseudomonas aeruginosa and Klebsiella pneumoniae. 2493 Dec 76


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