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  • Articles  (24)
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  • Escherichia coli
  • 1990-1994  (24)
  • 1945-1949
  • 1990  (24)
  • 1
    Electronic Resource
    Electronic Resource
    Mobilization ofEscherichia coli R1 silver-resistance plasmid pJT1 by Tn5-Mob intoEscherichia coli C600 (1990)
    Springer
    BioMetals 3 (1990), S. 24-27 
    Details
    ISSN: 1572-8773
    Keywords: Silver-resistance-accumulation ; Escherichia coli ; Mobilization ; Tn5-Mob ; Plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Escherichia coli Rl is an Ag+-resistant strain that, as we have shown recently, harbours at least two large plasmids, pJT1 (83 kb) and pJT2 (77 kb). Tn5-Mob was introduced into theE. coli Rl host replicon via conjugation on membrane filters. The transfer functions of plasmid RP4-4 were provided in this process and Tn5-Mob clones mated withE. coli C600 yielded Ag+-resistant transconjugants. This mobilization procedure allowed transfer and expression of pJT1 Ag+ resistance inE. coli C600. Prior to use of Tn5-Mob mobilization, it was not possible to transfer Ag+-resistant determinant(s) intoE. coli by conjugation or transformation including high-voltage electroporation.E. coli C600 containing PJTI and PJT2 displayed decreased accumulation of Ag+ similar toE. coli R1.E. coli C600 could not tolerate 0.1 and 0.5 mM Ag+, rapidly accumulated Ag+ and became non-viable. Tn5-Mob mobilization may be useful in the study of metal resistance in bacteria, especially in strains not studied for resistance mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01141173
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  • 2
    Electronic Resource
    Electronic Resource
    Different physiological roles of two independent pathways for nitrite reduction to ammonia by enteric bacteria (1990)
    Springer
    Archives of microbiology 154 (1990), S. 349-354 
    Details
    ISSN: 1432-072X
    Keywords: Nitrite reduction ; Anaerobic regulation ; NarL protein ; Two-component regulatory systems ; Anaerobic respiration ; Nitrite detoxification ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Operon fusion strains and mutants of Escherichia coli K-12 lacking the NADH-dependent nitrite reductase have been used to determine the regulation and physiological roles of two independent pathways for nitrite reduction to ammonia. Both the formate-and NADH-dependent pathways (Nrf and Nir, respectively) were totally repressed during aerobic growth, partially active during anaerobic growth in the absence of nitrite and further induced anaerobically by nitrite. Both were dependent upon a functional Fnr protein (a transcription activator of genes for anaerobic respiration). During anaerobic growth in the presence of nitrate, the Nir pathway was fully induced but Nrf was strongly repressed. Mutants defective in the NarL protein, which induces transcription of nitrate reductase genes but represses fumarate reductase genes in the presence of nitrate, were derepressed for Nrf activity during growth with nitrate, but the Nir enzyme was less active. The synthesis of Nrf components was also sensitive to glucose repression and weak activation by NarL during growth in the absence of nitrate. These data indicate that the Nir pathway provides a mechanism for detoxifying nitrite formed in the cytoplasm as a product of nitrate reduction. In contrast, the electrogenic reduction of nitrite by the Nrf pathway provides a secondary source of energy during anaerobic growth and is consequently repressed by the NarL protein when the thermodynamically more favourable electron acceptor, nitrate, is available. Two short DNA sequences, 5′-TACCAT-3′ and 5′-CTCCTT-3′, were found in the promoters of operons known to be activated or repressed by the NarL protein. It is proposed that NarL activates nir B transcription by binding to one or both of these sequences located 5′ to the RNA polymerase binding site, but represses other operons, including nrf, by binding close to the transcription start.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276530
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  • 3
    Electronic Resource
    Electronic Resource
    The specific functions of menaquinone and demethylmenaquinone in anaerobic respiration with fumarate, dimethylsulfoxide, trimethylamine N-oxide and nitrate by Escherichia coli (1990)
    Springer
    Archives of microbiology 154 (1990), S. 60-66 
    Details
    ISSN: 1432-072X
    Keywords: Menaquinone ; Demethylmenaquinone ; Anaerobic respiration ; Fumarate respiration ; DMSO respiration ; Nitrate respiration ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The respiratory activities of E. coli with H2 as donor and with nitrate, fumarate, dimethylsulfoxide (DMSO) or trimethylamine N-oxide (TMAO) as acceptor were measured using the membrane fraction of quinone deficient strains. The specific activities of the membrane fraction lacking naphthoquinones with fumarate, DMSO or TMAO amounted to ≤2% of those measured with the membrane fraction of the wild-type strain. After incorporation of vitamin K1 [instead of menaquinone (MK)] into the membrane fraction deficient of naphthoquinones, the activities with fumarate or DMSO were 92% or 17%, respectively, of the activities which could be theoretically achieved. Incorporation of demethylmenaquinone (DMK) did not lead to a stimulation of the activities of the mutant. In contrast, the electron transport activity with TMAO was stimulated by the incorporation of either vitamin K1 or DMK. Nitrate respiration was fully active in membrane fractions lacking either naphthoquinones or Q, but was ≤3% of the wild-type activity, when all quinones were missing. Nitrate respiration was stimulated on the incorporation of either vitamin K1 or Q into the membrane fraction lacking quinones, while the incorporation of DMK was without effect. These results suggest that MK is specifically involved in the electron transport chains catalyzing the reduction of fumarate or DMSO, while either MK or DMK serve as mediators in TMAO reduction. Nitrate respiration requires either Q or MK.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249179
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  • 4
    Electronic Resource
    Electronic Resource
    Some effects of growth conditions on steady state and heat shock induced htpG gene expression in continuous cultures of Escherichia coli (1990)
    Springer
    Archives of microbiology 155 (1990), S. 7-12 
    Details
    ISSN: 1432-072X
    Keywords: Temperature ; Heat shock gene expression ; htpG ; Heat shock protein ; Escherichia coli ; Continuous culture ; Dilution rate ; Growth medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most of the data concerning heat shock gene expression reported in the literature are derived from batch culture experiments under substrate and nutrient sufficient conditions. Here, the effects of dilution rate and medium composition on the steady state and heat shock induced htpG gene expression have been investigated in continuous cultures of Escherichia coli, using a chromosomal htpG-lacZ gene fusion. During steady state growth temperature dependent patterns of the relative htpG expression were found to be largely similar, irrespective of the growth condition. However, nitrogen-limited growth resulted in a markedly reduced specific steady state htpG expression as compared to growth under carbon limitation or in complex medium, correlating qualitatively with the total cellular protein content. During heat shock, tight temperature controlled expression was evident. While the relative heat shock induced expression was largely identical at various dilution rates in a given growth medium, significantly different response patterns were observed in the three growth media at any give dilution rate. From these results a clearly temperature regulated htpG expression during both, steady and transient state growth in continuous culture is evident, which is further significantly affected by the growth condition used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291266
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  • 5
    Electronic Resource
    Electronic Resource
    The cis-acting DNA sequences required in vivo for bacteriophage Mu helper-mediated transposition and packaging (1990)
    Springer
    Archives of microbiology 154 (1990), S. 67-72 
    Details
    ISSN: 1432-072X
    Keywords: DNA transposition ; Virus encapsidation ; Phage Mu ; Cis-acting DNA sequences ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 37,000 bp double-stranded DNA genome of bacteriophage Mu behaves as a plaque-forming transposable element of Escherichia coli. We have defined the cis-acting DNA sequences required in vivo for transposition and packaging of the viral genome by monitoring the transposition and maturation of Mu DNA-containing pSC101 and pBR322 plasmids with an induced helper Mu prophage to provide the trans-acting functions. We found that nucleotides 1 to 54 of the Mu left end define an essential domain for transposition, and that sequences between nucleotides 126 and 203, and between 203 and 1,699, define two auxiliary domains that stimulate transposition in vivo. At the right extremity, the essential sequences for transposition require not more than the first 62 base pairs (bp), although the presence of sequences between 63 and 117 bp from the right end increases the transposition frequency about 15-fold in our system. Finally, we have delineated the pac recognition site for DNA maturation to nucleotides 32 to 54 of the Mu left end which reside inside of the first transposase binding site (L1) located between nucleotides 1–30. Thus, the transposase binding site and packaging domains of bacteriophage Mu DNA can be separated into two well-defined regions which do not appear to overlap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249180
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  • 6
    Electronic Resource
    Electronic Resource
    Glutathione-gated K+ channels of Escherichia coli carry out K+ efflux controlled by the redox state of the cell (1990)
    Springer
    Archives of microbiology 154 (1990), S. 475-482 
    Details
    ISSN: 1432-072X
    Keywords: K+ exit ; Glutathione ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of K+ efflux across the membranes of i) wild-type Escherichia coli poisoned by the thiol reagent N-ethylmaleimide, ii) K+ retention mutants and iii) glutathione-deficient mutants, have revealed a common “K+ leaky phenotype”; it is characterized by a very high rate of K+ efflux. The results suggest that the products of kefB and kefC genes could encode two K+ channels, both gated by glutathione. The possible function of these K+ channels seems to be a K+ exit controlled by the redox state of the cell; indeed, it can be inferred from the effects of several oxidants and reductants that turning on and off of the K+ efflux mediated by the channels can be correlated with the redox state of glutathione.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00245231
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanism of Na+/proline symport inEscherichia coli: Reappraisal of the effect of cation binding to the Na+/proline symport carrier (1990)
    Springer
    The journal of membrane biology 114 (1990), S. 143-151 
    Details
    ISSN: 1432-1424
    Keywords: proline carrier ; Na+-symport ; proline binding ; Escherichia coli ; transport model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The proton and sodium ion dependences of the proline binding and transport activities of the proline carrier inEscherichia coli were investigated in detail. The binding activity in cytoplasmic membrane vesicles from a carrier over-producing strain (PT21/pTMP5) was absolutely dependent on the presence of Na+, but did not necessarily require protonation of the carrier, in contrast to the model previously reported (Mogi, T., Anraku, Y. 1984.J. Biol. Chem. 259:7797–7801). Based on this and previous observations, we propose a modified model of the proline binding reaction of the proline carrier, in which a proton is supposed to be a regulatory factor for the binding activity. The apparent Michaelis constant of proline (Kt) of the transport activity of cytoplasmic membrane vesicles from the wild typeE. coli strain driven by a respiratory substrate, ascorbate, showed dependence on a low concentration of sodium ion. The Michaelis constant of sodium ion for transport (Kt Na) was estimated to be 25 μm. The proline transport activities in membrane vesicles and intact cells were modulated by H+ concentration, the inhibitory effect of protons (pK a ≈6) being similar to that observed previously (Mogi, T., Anraku, Y. 1984.J. Biol. Chem. 259:7802–7806). Based on these observations and the modified model of substrate binding to the proline carrier, a model of the proline/Na+ symport mechanism is proposed, in which a proton is postulated to be a regulatory factor of the transport activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869095
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  • 8
    Electronic Resource
    Electronic Resource
    The Escherichia cohi minB mutation resembles gyrB in defective nucleoid segregation and decreased negative supercoiling of plasmids (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 87-93 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; minB ; Minicells ; Segregation ; Supercoiling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nucleoid segregation in the Escherichia coli minB mutant and in cells that over-produce minB gene products appeared defective as measured from fluorescence micrographs. Electrophoretic resolution of topoisomers of plasmid isolates from the minB strain revealed a decreased level of negative supercoiling; in addition, multimerization was observed. Over-production of the minB gene product also resulted in a decreased level of negative supercoiling. This phenotype is typical of the gyrB(ts) mutant, which is known to be affected in chromosome decatenation and supercoiling. We propose that the minB mutation and over-production of the minB gene products cause a defect in nucleoid segregation, which may be related to the decrease in negative supercoiling. As in the gyrB(ts) mutant, retardation of nucleoid segregation is proposed to inhibit constriction initiation in the cell centre and to give rise to nucleoid-free cell poles. As a consequence, these cells divide between nucleoid and cell pole, resulting in minicell and (sometimes) in anucleate cell formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280372
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular and functional analysis of the ruv region of Escherichia coli K-12 reveals three genes involved in DNA repair and recombination (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 219-226 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; DNA repair ; recombination ; ruvA, ruvB, ruvC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recombinant plasmids carrying ruvA, ruvB, or both were constructed and used to investigate the genetic defects in a collection of UV-sensitive ruv mutants. The results revealed that efficient survival of UV-irradiated cells depends on both ruvA and ruvB, and on a third gene, ruvC, located upstream of the ruvAB operon. Southern blotting analysis was used to locate insertions in ruv and to examine putative deletion mutants. Two Tn10 insertions were located to the region encoding ruvA. Since these insertions caused a deficiency in the activities of both ruvA and ruvB, we concluded that they must exert a polar effect on ruvB. Two putative ruv deletion mutants were shown to be the result of deletion-inversion events mediated during imprecise excision of Tn10. The relevant inversion breakpoints in these mutants were located to ruvA and ruvC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261724
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  • 10
    Electronic Resource
    Electronic Resource
    Translational coupling in a penP-lacZ gene fusion in Bacillus subtilis and Escherichia coli: Use of AUA as a restart codon (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 267-272 
    Details
    ISSN: 1617-4623
    Keywords: Translational coupling ; penP-lacZ gene fusion ; Bacillus subtilis ; Escherichia coli ; AUA restart codon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An out-of-frame fusion between the penicillinase gene (penP) of Bacillus licheniformis and the β-galactosidase gene (lacZ) of Escherichia coli was shown to direct the synthesis of an active β-galactosidase with the same electrophoretic mobility as the wild-type protein, both in B. subtilis and E. coli. This synthesis was dependent on translation of the truncated penP gene and appeared to result from translational coupling. The fusion point between penP and lacZ contained the sequence AUAG, in which the UAG and AUA codons were in-frame with the penP and lacZ reading units, respectively. N-terminal amino acid sequence analysis of the β-galactosidase protein suggested that, both in B. subtilis and E. coli, reinitiation of translation occurred at the AUA codon present at the gene fusion point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261730
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  • 11
    Electronic Resource
    Electronic Resource
    Export incompatibility of N-terminal basic residues in a mature polypeptide of Eschericbia coli can be alleviated by optimising the signal peptide (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 466-474 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Signal peptide ; OmpA ; Export incompatibility ; Periplasmic proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Export of the outer membrane protein, OmpA, across the cytoplasmic membrane of Escherichia coli was severely inhibited by the presence of two, three, four or six additional basic residues at the N-terminus of the mature polypeptide, but not by three similarily positioned acidic residues. Because a few bacterial proteins do possess basic residues close to the leader peptidase cleavage site and because the type of inhibition described here could pose problems in the construction of hybrid secretory proteins, we also studied means of alleviating this form of export incompatibility. Inhibition was abolished when basic residues were preceded by acidic ones. Also, the processing rates of the mutants with two or six basic residues could be partially restored by increasing the length of the hydrophobic core of the signal peptide. Taking this as a precedent, it is suggested that the structure of the signal peptide is an important feature for maintenance of a reasonable rate of translocation of those exported proteins which possess basic residue(s) at the N-terminus of the mature polypeptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00259413
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  • 12
    Electronic Resource
    Electronic Resource
    Cauliflower mosaic virus P35S promoter activity in Escherichia coli (1990)
    Springer
    Molecular genetics and genomics 223 (1990), S. 517-520 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; CaMV P35S promoter ; Kanamycin resistance ; Transcription initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We present evidence that the cauliflower mosaic virus promoter P35S can direct expression of the bacterial neomycin phosphotransferase II (NPTll) gene in . Transcription is initiated at several sites, the major one being located approximately 315 bases upstream of the plant start site. The nucleotide sequence directly preceding this start site is strongly homologous to the prokaryotic promoter consensus sequence. Thus constructs designed for introduction into plants can be expressed in E. coli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264462
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  • 13
    Electronic Resource
    Electronic Resource
    Use of recA803, a partial suppressor of recF, to analyze the effects of the mutant Ssb (single-stranded DNA-binding) proteins in vivo and in vitro (1990)
    Springer
    Molecular genetics and genomics 224 (1990), S. 129-135 
    Details
    ISSN: 1617-4623
    Keywords: recA803 ; ssb mutation ; recF ; Recombinational repair ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined the possibility that the ssb-1 and ssb-113 mutants exert some of their effects by interfering with the normal function of wild-type RecF protein. Consistent with this possibility, we found that recA803, which partially suppresses recF mutations, also partially suppresses both ssb mutations, as detected by an increase in UV resistance. No evidence was obtained for suppression of the defect in lexA regulon inducibility caused by the ssb mutations. Consequently we suggest that suppression occurs by increasing recombinational repair. In vitro tests of Ssb mutant and wild-type proteins revealed that the single-stranded DNA dependent ATPase activity of RecA protein is more susceptible to inhibition than the joint-molecule-forming activity. All three Ssb proteins inhibit the ATPase activity of RecA wild-type protein almost completely while under similar conditions they inhibit the joint-molecule-forming activity only slightly. Both activities of RecA803 protein were found to be less inhibited by the three Ssb proteins than those of RecA wild-type protein. This is consistent with the suppressing ability of recA803. We found no evidence to contradict the previously proposed hypothesis that ssb-1 affects recombinational repair by acting as a weaker form of Ssb protein. We found, however, only very weak evidence that Ssb-113 protein interferes directly with recombinational repair so that the possibility that it interferes with a normal function of RecF protein must remain open.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00259459
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  • 14
    Electronic Resource
    Electronic Resource
    Genetic mapping of phe V, an Escherichia coli gene for tRNAPhe (1990)
    Springer
    Molecular genetics and genomics 220 (1990), S. 317-319 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; tRNAPhe gene ; Ornithine decarboxylase gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the physical and genetic mapping of pheV, an Escherichia coli gene for phenylalanine tRNA, to 64 min on the chromosomal map in the near vicinity of speC coding for ornithine decarboxylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260501
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  • 15
    Electronic Resource
    Electronic Resource
    Measurement of in vivo expression of nrdA and nrdB genes of Escherichia coli by using IacZ gene fusions (1990)
    Springer
    Molecular genetics and genomics 220 (1990), S. 400-408 
    Details
    ISSN: 1617-4623
    Keywords: nrdAB transcription ; lacZ fusion ; SOS repair ; RecA protein ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By using a promoter probe plasmid we investigated expression of the linked nrdA and nrdB genes coding for the two different subunits of the ribonucleoside diphosphate reductase enzyme of Escherichia coli. For this reason, nrdA-lacZ, nrdAB-lacZ and nrdB-lacZ fusions were constructed. Results obtained indicate that the nrdB gene has a promoter from which it may be transcribed independently of the nrdA gene. Furthermore, the nrdB gene may also be transcribed from the nrdA promoter. The expression of the nrdB gene is about 14-fold higher from the nrdA promoter than from its own promoter. The induction of both nrdA and nrdB genes by DNA-damaging agents in the wild-type strain as well as in several SOS mutants was also studied; nrdA gene expression was increased by these treatments in RecA–, RecA−, and LexAInd− strains, although in both RecA− and LexAInd− mutants the nrdA gene expression was considerably lower than that in RecA– cells. nrdB gene expression was stimulated by DNA damage only when its transcription was from the nrdA promoter, but there was no effect when nrdB was transcribed from its own promoter. In addition, the basal level of nrdA-lacZ and nrdAB-lacZ fusions was reduced in strains containing either RecA− and LexAInd− mutations or a multicopy plasmid carrying the lexA – gene, whereas the presence of a LexA5lDef mutation increased the constitutive expression of both fusions. On the contrary, the basal level of the nrdB-lacZ fusion remained constant in all these strains. Together these results indicate that induction of the SOS response enhances expression of the nrd genes from the nrdA promoter.
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    URL: http://dx.doi.org/10.1007/BF00391745
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  • 16
    Electronic Resource
    Electronic Resource
    The Mu1 transposable element of maize contains two promoter signals recognized by the Escherichia coli RNA polymerase (1990)
    Springer
    Molecular genetics and genomics 222 (1990), S. 71-76 
    Details
    ISSN: 1617-4623
    Keywords: Transposable elements ; Promoters ; Maize ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The galactokinase (GaIK) expression plasmid vector system pK0-1 has been used to screen for promoter elements in the maize transposable element Mu1 that function in Escherichia coli. Two transcriptional start points, named S1 and S2, were identified, which are located in the two direct repeats of the transposable element. This paper demonstrates that sequence elements exist in a plant transposable element which function as prokaryotic promotors.
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    URL: http://dx.doi.org/10.1007/BF00283025
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  • 17
    Electronic Resource
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    Transcription and regulation of the cpdB gene in Escherichia coli K12 and Salmonella typhimurium LT2: Evidence for modulation of constitutive promoters by cyclic AMP-CRP complex (1990)
    Springer
    Molecular genetics and genomics 222 (1990), S. 161-165 
    Details
    ISSN: 1617-4623
    Keywords: Cyclic phosphodiesterase ; Cyclic AMP receptor protein ; Escherichia coli ; Salmonella ; Gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Measurements of cyclic phosphodiesterase, or of β-galactosidase in the case of cpdB′-′ZacZ fusions, indicate that cpdB expression in both Escherichia coli and Salmonella typhimurium is modulated by carbon source availability, consistent with previous observations in Salmonella. Nucleotide sequence analysis and transcription mapping of both cpdB genes have revealed, in their 5′ flanking regions, sequences with good similarity to consensus −10 and −35 regions and cyclic AMP-cyclic AMP receptor protein (cAMP-CRP) binding sites. Furthermore, they are strongly conserved in both organisms. Deletion analysis of an E. coli cpdB′-′ lacZ fusion supports the identification of these elements, and a role for the cAMP-CRP binding site in modulating constitutive cyclic phosphodiesterase expression.
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    URL: http://dx.doi.org/10.1007/BF00283039
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  • 18
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    T-T Cyclobutane dimers are misinstructive, rather than non-instructive, mutagenic lesions (1990)
    Springer
    Molecular genetics and genomics 222 (1990), S. 166-168 
    Details
    ISSN: 1617-4623
    Keywords: Cyclobutane pyrimidine dimers ; Non-instructive mutagenic lesions ; Escherichia coli ; Single specific mutagenic lesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The lesions produced by SOS-dependent mutagens in Escherichia coli are commonly referred to as non-pairing or non-instructive. Although these terms are likely to be appropriate for some lesions, particularly the abasic site, for others, such as the cyclobutane dimer, their suitability is open to question. To address this question, we have compared the error frequencies and spectra that result when a uniquely located T-T sequence, carried in a single-stranded vector, contains either a cis-syn or a trans-syn cyclobutane dimer, or when either the 5′T or 3′T is converted to an abasic site. The data suggest that the high accuracy with which the dimer-containing templates are replicated is unlikely to be the consequence of polymerase preference for the non-instructive insertion of dAMP. Similarly, mis-pairing, rather than non-pairing, is likely to cause mutations. Cyclobutane dimers seem therefore to be misinstructive rather than non-instructive lesions, and the common feature shared by SOS-inducing lesions is more their ability to block replication than inability to form correct base pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283040
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  • 19
    Electronic Resource
    Electronic Resource
    Iron(III)hydroxamate transport of Escherichia coli K12: Single amino acid replacements at potential ATP-binding sites inactivate the FhuC protein (1990)
    Springer
    Molecular genetics and genomics 223 (1990), S. 159-162 
    Details
    ISSN: 1617-4623
    Keywords: Iron transport ; Energization ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mechanism of iron(III)hydroxamate transport appears to be of the periplasmic binding protein dependent transport (PBT) kind which is energized by ATP hydrolysis. The FhuC protein contains two domains typical of ATP-binding proteins. Lysine in domain I was replaced by glutamine and glutamate, and aspartate in domain II by asparagine and glutamate, resulting in FhuC derivatives which no longer transported ferrichrome and albomycin. FhuC inactivation by the aspartate-glutamate substitution is especially noteworthy since the negative charge thought to be involved in Mg2+-ATP binding remains the same and the two amino acid side chains differ in only a CH2 group. It is concluded that the two domains that represent consensus sequences among all peripheral cytoplasmic membrane proteins of PBT systems are involved in substrate transport.
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    URL: http://dx.doi.org/10.1007/BF00315810
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  • 20
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    The glutamate dehydrogenase structural gene of Escherichin coli (1990)
    Springer
    Molecular genetics and genomics 223 (1990), S. 508-512 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Glutamate dehydrogenase ; gdhA gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The glutamate dehydrogenase structural gene, gdhA, was mapped at 38.6 min on the genetic map and at 1860 kb on the physical map. A detailed map of this region is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264460
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    Mutant of the glutamine transfer RNA gene as UGA suppressor in Escherichia coli (1990)
    Springer
    Molecular genetics and genomics 223 (1990), S. 433-437 
    Details
    ISSN: 1617-4623
    Keywords: UGA suppressor ; tRNA 2 Gln gene ; Lethal effect ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A UGA suppressor derived from a glutamine tRNA gene of Escherichia coli K 12 was isolated and characterized. Phages carrying the suppressor su+2UGA could be obtained only from a hybrid transducing phage, h 80 cI 857psu +2oc, but not from the original transducing phage λcI 857psu +2oc. By DNA sequence analysis, it was found that the su +2 UGA suppressor obtained has two mutations; one is in the anticodon (TTA→TCA), as expected, and the other (C→T) is at the 7th position from the 3′ end of tRNA 2 Gln . The significance of these mutations and the lethal effect on phage λ of the increased amounts of UGA suppressor tRNAs are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264450
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    Electronic Resource
    Signal peptide mutants ofEscherichia coli (1990)
    Springer
    Journal of bioenergetics and biomembranes 22 (1990), S. 233-269 
    Details
    ISSN: 1573-6881
    Keywords: Signal peptide ; loop model ; mutation ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Numerous secretory proteins of the Gram-negative bacteriaE. coli are synthesized as precursor proteins which require an amino terminal extension known as the signal peptide for translocation across the cytoplasmic membrane. Following translocation, the signal peptide is proteolytically cleaved from the precursor to produce the mature exported protein. Signal peptides do not exhibit sequence homology, but invariably share common structural features: (1) The basic amino acid residues positioned at the amino terminus of the signal peptide are probably involved in precursor protein binding to the cytoplasmic membrane surface. (2) A stretch of 10 to 15 nonpolar amino acid residues form a hydrophobic core in the signal peptide which can insert into the lipid bilayer. (3) Small residues capable of β-turn formation are located at the cleavage site in the carboxyl terminus of the signal peptide. (4) Charge characteristics of the amino terminal region of the mature protein can also influence precursor protein export. A variety of mutations in each of the structurally distinct regions of the signal peptide have been constructedvia site-directed mutagenesis or isolated through genetic selection. These mutants have shed considerable light on the structure and function of the signal peptide and are reviewed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00763167
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    Export and sorting of theEscherichia coli outer membrane protein OmpA (1990)
    Springer
    Journal of bioenergetics and biomembranes 22 (1990), S. 441-449 
    Details
    ISSN: 1573-6881
    Keywords: Escherichia coli ; plasma membrane ; outer membrane ; OmpA ; protein translocation/sorting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Results of studies, mostly using the outer membrane, 325 residue protein OmpA, are reviewed which concern its translocation across the plasma membrane and incorporation into the outer membrane ofEscherichia coli. For translocation, neither a unique export signal, acting in a positive fashion within the mature part of the precursor, nor a unique conformation of the precursor is required. Rather, the mature part of a secretory protein has to be export-compatible. Export-incompatibility can be caused by a stretch of 16 (but not 8 or 12) hydrophobic residues, too low a size of the polypeptide (smaller than 75 residue precursors), net positive charge at the N-terminus, or lack of a turn potential at the same site. It is not yet clear whether binding sites for chaperonins (SecB, trigger factor, GroEL) within OmpA are importantin vivo. The mechanism of sorting of outer membrane proteins is not yet understood. The membrane part of OmpA, encompassing residues 1 to about 170, it thought to traverse the membrane eight times in antiparallel β-sheet conformation. At least the structure of the last β-strand (residues 160–170) is of crucial importance for membrane assembly. It must be amphiphilic or hydrophobic, these properties must extend over at least nine residues, and it must not contain a proline residue at or near its center. Membrane incorporation of OmpA involves a conformational change of the protein and it could be that the last β-strand initiates folding and assembly in the outer membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00763176
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    Physical constraints on microbial behavior How you act if you are very small (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 119-120 
    Details
    ISSN: 1573-1561
    Keywords: Chemotaxis ; sensory transduction ; diffusion ; viscous flow ; Escherichia coli ; Bacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Physical constraints limit the way in which an organism as small asEscherichia coli can interact with its surroundings. These constraints are listed, together with references to the relevant literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01021273
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