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  • 1
    Electronic Resource
    Electronic Resource
    Molecular analysis of two ScrR repressors and of a ScrR–FruR hybrid repressor for sucrose and D-fructose specific regulons from enteric bacteria (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 9 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The scr regulon of pUR400 and the chromosomally encoded scr regulon of Klebsiella pneumoniae KAY2026 are both negatively controlled by a specific repressor (ScrR). As deduced from the nucleotide sequences, both scrR genes encode polypeptides of 334 residues (85.5% identical base pairs, 91.3% identical amino acids), containing an N-terminal helix-turn-helix motif. Comparison with other regulatory proteins revealed 30.6% identical amino acids to FruR, 27.0% to Lacl and 28.1% to GaIR. Six scrRs super-repressor mutations define the inducer-binding domain. The scr operator sequences were identified by in vivo titration tests of the sucrose repressor and by in vitro electrophoretic mobility shift assays. D-fructose, an intracellular product of sucrose transport and hydrolysis, and D-fructose 1-phosphate were shown to be molecular inducers of both scr regulons. An active ScrR–FruR hybrid repressor protein was constructed with the N-terminal part of the sucrose repressor of K. pneumoniae and the C-terminal part of the fructose repressor of Salmonella typhimurium, LT2. Gel retardation assays showed that the hybrid protein bound to scr-specific operators, and that D-fructose 1-phosphate, the inducer for FruR, was the only inducer. In vivo, neither the operators of the fru operon nor of the pps, operon, the natural targets for FruR, were recognized, but the scr operators were. These data and the data obtained from the super-repressor alleles confirm previous models on the binding of repressors of the Lacl family to their operators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01681.x
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  • 2
    Electronic Resource
    Electronic Resource
    Cloning and physical mapping of the sor genes for L-sorbose transport and metabolism from Klebsiella pneumoniae (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The sor genes of Klebsiella pneumoniae KAY2026, which enable the bacterium to metabolize the ketose L-sorbose, have been cloned on an 8.3kb DNA fragment into the multicopy plasmid, pACYC184. The genes were mapped by restriction analysis, by deletion mapping and by insertion mutagenesis with Tn1725. The corresponding gene products were identified by the maxicell technique. The structural genes sorD, sorA and sorE code for a D-glucitol-6-P dehydrogenase (27 kilodalton (kD)), an Enzymell (EIISor) activity specific for L-sorbose and an L-sorbose-1-P reductase (45kD). Besides these genes for known functions, three additional genes were discovered: sorC, coding for a transcriptional 40kD regulatory protein, and sorF and sorB, coding for two proteins of 14kD and 19kD, respectively, involved in transport. The genes form an operon (gene order sorCpCDFBAE) and are inducible by L-sorbose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb02067.x
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  • 3
    Electronic Resource
    Electronic Resource
    Plasmid-mediated sucrose metabolism in Escherichia coli K12: mapping of the scr genes of pUR400 (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The scr genes located on plasmid pUR400 and responsible for sAucrose (Scr) metabolism of Escherichia coli K12 and other enteric bacteria have been cloned on a 9.3 kb DNA fragment. The different genes were mapped by transposon insertion mutagenesis, by restriction endonuclease and deletion mapping, and the corresponding gene products were identified. Besides the known structural genes scrA, coding for an EnzymellScr (45 kD) of the phosphoenolypyruvate-dependent phosphotransferase system (PTS), and scrB, coding for a sucrose 6-phosphate hydrolase (invertase) (55 kD), two new structural genes were discovered. Gene scrK apparently codes for an intracellular and ATP-dependent fructokinase (39 kD), while scry seems to code for a sucrose porin (58 kD) in the outer cell membrane. No genes for an Enzyme IIIScr of the PTS or for (a) glycosyltransferase(s) were detected. The four genes form an scr operon (gene order, scrK scrY scrA scrB, transcription from K to B), regulated by a repressor (gene scrR, 37 kD) and inducible by sucrose, fructose and fructose-containing oligosaccharides
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00001.x
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  • 4
    Electronic Resource
    Electronic Resource
    Suppression of IIIGlc-defects by Enzymes IINag and IIBgl of the PEP:carbohydrate phosphotransferase system (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Enzymes II of the PEP:carbohydrate phosphotransferase system (PTS) specific for N-acetylglucosamine (IINag) and β-glucosides (IIBgl) contain C-terminal domains that show homology with Enzyme IIIGlc of the PTS. We investigated whether one or both of the Enzymes II could substitute functionally for IIIGlc. The following results were obtained: (i) Enzyme IINag, synthesized from either a chromosomal or a plasmidencoded nagE+ gene could replace IIIGlc in glucose, methyl α-glucoside and sucrose transport via the corresponding Enzymes II. An Enzyme IINag with a large deletion in the N-terminal domain but with an intact C-terminal domain could also replace IIIGlc in IIGlc-dependent glucose transport, (ii) After decryptification of the Escherichia coli bgl operon, Enzyme IIBgl could substitute for IIIGlc. (iii) Phospho-HPr-dependent phosphorylation of methyl α-glucoside via IINag/IIGlc is inhibited by antiserum against IIIGlc as is N-acetyl-glucosamine phosphorylation via IINag. (iv) In strains that contained the plasmid which coded for IINag, a protein band with a molecular weight of 62000 D could be detected with antiserum against IIIGlc. We conclude from these results that the IIIGlc-like domain of Enzyme IINag and IIBgl can replace IIIGlc in IIIGlc-dependent carbohydrate transport and phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00082.x
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  • 5
    Electronic Resource
    Electronic Resource
    DNA sequence of the gene scrA encoding the sucrose transport protein EnzymellScr of the phosphotransferase system from enteric bacteria: homology of the EnzymellScr and EnzymellBgl proteins (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The nucleotide sequence of the structural gene, scrA, which codes for sucrose-specific EnzymellScr (EIIScr) of the phosphoenolpyruvate-dependent carbohydrate: phosphotransferase system (PTS), was determined. EllScr requires an Enzymelll, the product of the gene crr, for full activity. The gene scrA is preceded immediately by a classical Shine-Dalgarno sequence (AAGAGGGTA). It contains 1368 nucleotides with an increased GC-content (58%) corresponding to a polypeptide of 455 amino acid residues (Mr 47 500). The protein has the hydropathic profile (average hydropathy +0.82) of an integral membrane protein lacking extended α-helical structures and a signal peptide. Comparison with the sequence of the β-glucoside-specific Enzymell (EllBgl, 625 amino acids, Mr 66480; Bramley and Kornberg, 1987a; Schnetz et al., 1987) revealed strong homologies between EllScr and the first 458 residues of EllBgl. The 162 carboxyterminal residues of EllBgl, however, showed a high homology with the sequence of Enzymelll (Nelson et al., 1984), a homology also described recently by Bramley and Kornberg (1987b). The evolutionary and functional significance of the similarities with four other Enzymesll is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00002.x
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  • 6
    Electronic Resource
    Electronic Resource
    A sugar-specific porin, ScrY, is involved in sucrose uptake in enteric bacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: 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 58kDa), localized in the outer membrane, led, as shown here, to an increase in the apparent Km for sucrose transport in whole cells from 10 μM in wild-type cells to 300 μM 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 μM, 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb00769.x
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular analysis of two fructokinases involved in sucrose metabolism of enteric bacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sucrose-positive derivatives of Escherichia coli K-12, containing the plasmid pUR400, and of Klebsiella pneumoniae hydrolyse intracellular sucrose 6-phosphate by means of an invertase into d-glucose 6-phosphate and free d-fructose. The latter is phosphorylated by an ATP-dependent fructokinase (gene scrK of an scr regulon) to d-fructose 6-phosphate. The lack of ScrK does not cause any visible phenotype in wild-type strains of both organisms. Using genes and enzymes normally involved in d-arabinitol metabolism from E. coli C and K. pneumoniae, derivatives of E. coli K-12 were constructed which allowed the identification of scrK mutations on conventional indicator plates. Cloning and sequencing of scrK from sucrose plasmid pUR400 and from the chromosome of K. pneumoniae revealed an open reading frame of 924 bp in both cases — the equivalent of a peptide containing 307 amino acid residues (Mr, 39 and 34 kDa, respectively, on sodium dodecyl sulphate gels). The sequences showed overall identity among each other (69% identical residues) and to a kinase from Vibrio alginoiyticus (57%) also involved in sucrose metabolism, lower overall identity (39%) to a d-ribose-kinase from E. coli, and local similarity to prokaryotic, and eukaryotic phosphofructokinases at the putative ATP-binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb01851.x
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  • 8
    Electronic Resource
    Electronic Resource
    Carbohydrate transport in bacteria under environmental conditions, a black box? (1993)
    Springer
    Antonie van Leeuwenhoek 63 (1993), S. 275-288 
    Details
    ISSN: 1572-9699
    Keywords: carbohydrate ; transport ; bacteria ; strategies ; environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A typical eubacterium carries a battery of substrate transport systems which are the ultimate pacemakers for growth. These systems reflect a billion year old selection for coping with rapidly changing conditions in the environment and each of them is optimised for specific growth conditions. Metabolic pathways in combination with transport systems can be interpreted as transient sensory systems, where a transport system corresponds to a sensor for external stimuli. Characteristic is a tightly linked common control between a carbohydrate metabolic pathway and the corresponding transport system. Many of the observed growth phenomena are a direct result of adaptation and regulation of transport capacity to rapid changes in environmental conditions. Some of the better understood examples are discussed. Nevertheless, knowledge on bacterial carbohydrate transport under environmental conditions as documented in the literature is still scarce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00871223
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of a chromosomally encoded, non-PTS metabolic pathway for sucrose utilization in Escherichia coli EC3132 (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 22-32 
    Details
    ISSN: 1617-4623
    Keywords: Sucrose ; Non-PTS pathway ; H+-symport ; Chromosomal genes ; E. coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A wild-type isolate, EC3132, of Escherichia coli, that is able to grow on sucrose was isolated and its csc genes (mnemonic for chromosomally coded sucrose genes) transferred to strains of E. coli K12. EC3132 and all sucrose-positive exconjugants and transductants invariably showed a D-serine deaminase (Dsd)-negative phenotype. The csc locus maps adjacent to dsdA, the structural gene for the D-serine deaminase, and contains an inducible regulon, controlled by a sucrose-specific repressor CscR, together with structural genes for a sucrose hydrolase (invertase) CscA, for a d-fructokinase CscK, and for a transport system CscB. Based on DNA sequencing studies, this last codes for a hydrophobic protein of 415 amino acids. CscB is closely related to the β-galactoside transport system LacY (31.2% identical residues) and a raffinose transport system RafB (32,3% identical residues) of the enteric bacteria, both of the proton symport type. A two-dimensional model common to the three transport proteins, which is based on the integrated consensus sequence, will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286177
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular analysis of the scrA and scrB genes from Klebsiella pneumoniae and plasmid pUR400, which encode the sucrose transport protein Enzyme IIScr of the phosphotransferase system and a sucrose-6-phosphate invertase (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 197-206 
    Details
    ISSN: 1617-4623
    Keywords: Key words Sucrose metabolism ; Invertase ; Phosphotransferase system (PTS) ; Transporter ; Enteric bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Klebsiella pneumoniae genes scrA and scrB are indispensable for sucrose (Scr) utilisation. Gene scrA codes for an Enzyme IIScr (IIScr) transport protein of the phosphoenolpyruvate-dependent carbohydrate: phosphotransferase system (PTS), while scrB encodes a sucrose 6-phosphate specific invertase. A 3.7 kb scrAB DNA fragment has been cloned from K. pneumoniae and expressed in Escherichia coli. Its nucleotide sequence was determined and the coding regions for scrA (1371 bp) and scrB (1401 bp) were identified by genetic complementation, enzyme activity tests and radiolabelling of the gene products. In addition, the nucleotide sequence of the scrB gene from the conjugative plasmid pUR400 isolated from Salmonella typhimurium was also determined and errors in the previously published sequence of the scrA gene of pUR400 were corrected. Extensive similarity was found between the sequences of ScrA and other Enzymes II, as well as between the two invertases and other sucrose hydrolysing enzymes. Based on the analysis of seven IIScr proteins, a hypothetical model of the secondary structure of IIScr is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02174179
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