Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The alternative sigma factor sigma 54 is required for transcription of nitrogen fixation genes in Klebsiella pneumoniae and other diazotrophs. The nif genes, and other E sigma 54-dependent genes whose products are necessary for a wide range of processes, are postively regulated. A unifying model that is well supported by studies on nif and other nitrogen-regulated (ntr) genes includes the central tenet that sigma 54 confers upon core RNA polymerase the ability to recognize and bind specific promoter sequences, but not the ability to isomerize to the open complex without assistance from the appropriate activator protein. Direct physical evidence for formation of an activator-independent complex between E sigma 54 and the NifA-dependent K. pneumoniae nifH and nifU promoters has, to date, been lacking. Using purified components we have now demonstrated formation of the closed complex at these promoters, indicating that it is an intermediate along the pathway to open complex formation. The closed complex was not detected when conserved features of the promoter were altered by mutation, nor was its stability increased when integration host factor protein was bound adjacent to the E sigma 54 recognition sequence.
Mol Microbiol 1992 Jun
PMID:Activator-independent formation of a closed complex between sigma 54-holoenzyme and nifH and nifU promoters of Klebsiella pneumoniae. 149 90

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)
Mol Microbiol 1992 Jul
PMID:NADH formation by Na(+)-coupled reversed electron transfer in Klebsiella pneumoniae. 150 43

We have determined the sequence of the lamB gene from Klebsiella pneumoniae. It encodes the precursor to the LamB protein, a 429 amino acid polypeptide with maltoporin function. Comparison with the Escherichia coli LamB protein reveals a high degree of homology, with 325 residues strictly identical. The N-terminal third of the protein is the most conserved part of the molecule (1 change in the signal sequence, and 13 changes up to residue 146 of the mature protein). Differences between the two mature proteins are clustered mainly in six regions comprising residues 145-167, 173-187, 197-226, 237-300, 311-329, and 367-387 (K. pneumoniae LamB sequence). The most important changes were found in regions predicted by the two-dimensional model of LamB folding to form loops on the cell surface. In vivo maltose and maltodextrin transport properties of E. coli K12 and K. pneumoniae strains were identical. However, none of the E. coli K12 LamB-specific phages was able to plaque onto K. pneumoniae. Native K. pneumoniae LamB protein forms highly stable trimers. The protein could be purified by affinity chromatography on starch-Sepharose as efficiently as the E. coli K12 LamB protein, indicating a conservation of the binding site for dextrins. However, none of the monoclonal antibodies directed against native E. coli K12 LamB protein recognized native purified K. pneumoniae LamB protein. These data indicate that most of the variability occurs within exposed regions of the protein and provide additional support for the proposed model of LamB folding.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Gen Genet 1992 Jun
PMID:DNA sequence analysis of the lamB gene from Klebsiella pneumoniae: implications for the topology and the pore functions in maltoporin. 153 83

Klebsiella pullulanase is a lipoprotein synthesized as a precursor with a signal peptide, which is processed by lipoprotein signal peptidase. To clarify the role of lipid modification of pullulanase, we purified lipid-modified wild-type and the unmodified (mutant) pullulanases and compared their properties. The Km and Vmax values of both pullulanases for pullulan were the same. The optimal pH and temperature, the stabilities over pH and temperature ranges, the specificity of substrates, and the patterns of inhibition of the lipid-modified and unmodified pullulanases were also the same. However, we found that the wild-type pullulanase formed trimers whereas the unmodified enzyme did not, and that the migrations of the two enzymes on sodium dodecyl sulphate/electrophoresis were different when the samples were applied on the gel without heating. The results presented in this paper and in previous work show that the correct processing and translocation of pullulanase in K. aerogenes require modification of lipid. However, the enzymatic properties and physical stabilities of pullulanase were not affected by the lipid modification.
Mol Microbiol 1992 Feb
PMID:Role of lipid modification on a starch-debranching enzyme, Klebsiella pullulanase: comparison of properties of lipid-modified and unmodified pullulanases. 155 52

The last gene (pulO) of the pulC-O pullulanase secretion gene operon of Klebsiella oxytoca codes for a protein that is 52% identical to the product of the pilD/xcpA gene required for extracellular protein secretion and type IV pilus biogenesis in Pseudomonas aeruginosa. The PilD/XcpA protein is known to remove the first six amino acids of the signal sequence of the type IV pilin precursor by cleaving after the glycine residue in the conserved sequence GF(M)XXXE (where X represents hydrophobic amino acids). This prepilin peptidase cleavage site is present in the products of four genes in the pulC-O operon (PulG, PulH, Pull and PulJ proteins). It is shown here that PulO processes the pulG gene product in vivo. Processing was maximal within 15 seconds, but experiments in which the expression of pulO was uncoupled from that of the other genes in the secretion operon suggest that processing can also occur post-translationally. The products of two pulG derivatives with internal inframe deletions were also processed by PulO, but the three PulG-PhoA hybrids, two PulJ-PhoA hybrids and the single PulH-PhoA hybrid tested did not appear to be processed. Sucrose gradient fraction experiments showed that both precursor and mature forms of PulG appear to be associated with low-density, outer membrane vesicles prepared by osmotic lysis of sphaeroplasts. Neither the xcpA gene nor the Bacillus subtilis gene comC, which is also homologous to pulO and codes for a protein with type IV prepilin peptidase activity, can correct the pullulanase secretion defect in an Escherichia coli strain carrying all of the genes required for secretion except pulO. Furthermore, neither XcpA nor ComC is able to process prePulG protein in vivo.
Mol Microbiol 1992 Mar
PMID:An enzyme with type IV prepilin peptidase activity is required to process components of the general extracellular protein secretion pathway of Klebsiella oxytoca. 157 4

The positive control protein NifA of Klebsiella pneumoniae activates transcription by RNA polymerase containing sigma 54 by catalysing open promoter complex formation. We show that the integrity of the putative ATP-binding pocket in the central domain of NifA is necessary for the positive control function of NifA, but is not required for DNA-binding or recognition of NifA by NifL. The inactive mutant NifA proteins are trans dominant to wild-type NifA and are unable to catalyse formation of open promoter complexes irrespective of whether a closed promoter complex at the nifH promoter has preformed. Formation of the closed complex results in a DNA structural distortion adjacent to the DNA region melted in the open promoter complex. This distortion lies at the leading edge of the E sigma 54 footprint. Although unable to catalyse open complex formation, some mutant NifAs altered the chemical reactivity of the distorted base-pair indicating that they retain the ability to recognize the closed promoter complex. The activation phenotype of partially active NifA molecules was sensitive to promoter sequences known to influence closed complex formation, indicating differences in (1) the susceptibility of the closed complexes towards activation and (2) their requirements for NifA during activation.
J Mol Biol 1992 May 20
PMID:Central domain of the positive control protein NifA and its role in transcriptional activation. 159 20

Transcription from the sigma 54-dependent Klebsiella pneumoniae nifL and glnAp2 promoters is activated by the general nitrogen regulatory protein NTRC. Unlike the glnAp2 promoter, which is relatively insensitive to changes in DNA supercoiling, transcription from nifL in vitro in a chloride-based buffer is supercoiling-dependent at physiological salt concentrations. The replacement of chloride with an acetate-based buffer decreases the stringency of the nifL supercoiling response, but open complexes formed on linear nifL promoter DNA under these conditions are unstable and less extensive than those found on supercoiled (form I) DNA. We have introduced mutations in particular elements of the nifL promoter that increase its homology to glnAp2. At the wild-type nifL promoter, sigma 54-RNA polymerase makes only limited contacts with the promoter in the absence of NTRC. However, a G to T change at -26 (nifL74) allows the formation of a stable closed complex with sigma 54-holoenzyme on both linear and form I templates in the absence of the activator. The combination of C to T mutations at -3 and -1 (nifL18) increases the A+T rich nature of the melted region and stabilizes open complexes formed on linear DNA. Open complex formation as a function of superhelical density was assessed at each promoter. Formation of open complexes at glnAp2 peaks at -0.024 and declines at higher superhelical densities, whereas at the wild-type nifL promoter, open complex formation peaks at -0.067 and is not detectable at superhelical densities less than -0.032. Both the nifL74 and nifL18 mutations altered the supercoiling response, increasing the ability to form open complexes at low superhelical densities. The presence of the nifL74 and nifL18 mutations in combination further altered the response of the promoter to DNA supercoiling. These observations suggest that the promoter as a whole, and not any one promoter element, mediates the transcriptional response to DNA supercoiling.
J Mol Biol 1992 Jun 05
PMID:DNA supercoiling response of the sigma 54-dependent Klebsiella pneumoniae nifL promoter in vitro. 160 72

During the molecular analysis of a plasmid-coded sucrose metabolic pathway of enteric bacteria, a gene, scrY, was found whose product, ScrY, had all the properties of a bacterial porin (Schmid et al., 1988). Loss of this protein (Mr 58 kDa), localized in the outer membrane, led, as shown here, to an increase in the apparent Km for sucrose transport in whole cells from 10 microM in wild-type cells to 300 microM in mutant cells. This contrasts with the Km for sucrose phosphorylation as measured in membrane vesicles from mutant and wild-type cells, which remained unchanged at about 10 microM, and reflects the activity of the sucrose-specific Enzymell of the phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system (PTS) responsible for uptake through the inner membrane. Furthermore, the presence of ScrY restored growth on maltodextrins in cells devoid of LamB, thus complementing the lack of this maltoporin. The amino acid sequence deduced from the DNA sequence was determined for the plasmid-coded and the ScrY porin coded in the chromosome of Klebsiella pneumoniae. Both show high identity (86%) to each other, and to the channel domain of LamB, further corroborating the conclusion that they constitute porins.
Mol Microbiol 1991 Apr
PMID:A sugar-specific porin, ScrY, is involved in sucrose uptake in enteric bacteria. 164 46

Tn21-related transposons are widespread among bacteria and carry various resistance determinants at preferential sites, hs1 and hs2. In an in vivo integrative recombination assay it was demonstrated that these hot spots direct the integration of aminoglycoside resistance genes like aadB from Klebsiella pneumoniae and aacAI from Serratia marcescens, in a recA- background. The maximum required recognition sequence which must be present in both the donor and recipient plasmids is 5' CTAAAACAAAGTTA 3' (hs2). The double-site-specific recombination occurred with a frequency of 10(-5)-10(-6). The resulting structures include not only replicon fusion products but also more complex structures carrying two copies of the donor plasmid or simply the donor gene flanked by hs elements. hs1 and hs2 are thought to act as recognition sites for a transacting site-specific recombinase. By the use of Tn21 deletion derivatives, it has been shown that the recombinase is not encoded by Tn21. This new integrative recombination system is involved in the acquisition of new genes by Tn21-related transposons and their spread among bacterial populations.
Mol Gen Genet 1991 Sep
PMID:Site-specific integration of genes into hot spots for recombination flanking aadA in Tn21 transposons. 165 5

Four substitutions at serine residue 160 which increase the activity of the sigma 54-dependent activator protein NTRC in the absence of NTRB have been analysed in detail. Mutagenesis of the putative phosphoacceptor site of NTRC and analysis of double mutants indicate that the positive control function of the S160W and S160C mutants is phosphorylation-dependent, whereas the activity of the S160Y and S160F mutants is phosphorylation-independent. This was confirmed with two purified mutant proteins in vitro. Occupancy of tandem NTRC-binding sites upstream of the Klebsiella pneumoniae nifL promoter by S160W protein is also phosphorylation-dependent in contrast to occupancy by S160F protein, confirming that both the DNA-binding and activator functions of NTRC are influenced by phosphorylation. The S160W and S160C mutants are apparently more responsive than wild-type protein to 'cross-talk' by other members of the histidine protein kinase family but are less responsive to phosphorylation and dephosphorylation mediated by NTRB.
Mol Microbiol 1991 Jul
PMID:Substitutions at a single amino acid residue in the nitrogen-regulated activator protein NTRC differentially influence its activity in response to phosphorylation. 165 38


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>