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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 205 (1994), S. 802-806 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Plasmid 32 (1994), S. 89-94 
    ISSN: 0147-619X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0378-1119
    Keywords: Phage development ; complementation ; lysogenization ; plaque morphology ; positive control ; rpoA mutants
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Keywords: Regulation of DNA replication ; Coliphageλ ; DnaA initiator ; Transcriptional activation ; Chaperone proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We demonstrate a variation in the effects of seven alleles of theEscherichia coli dnaA gene, which cause temperature sensitivity of initiation of chromosomal replication, on the replication ofλ phage-derived plasmids at 30° C. These mutants showed no allele specificity ofdnaA function in replication of either of twoλπ plasmids studied. On the other hand, the inability of theλP + plasmid to replicate indnaA508, 46 and204 cells, indnaB (groP A15) or in cells that are temperature sensitive for the chaperone genesdnaK756, dnaJ259 andgrpE280 and 30° C was suppressible by a singleπ mutation. This suggests that it is a common property of theπ protein, probably its weaker interaction with DnaB helicase, that is responsible for the suppression. One can also conclude that the DnaA-regulated transcriptional activation oforiλ acts at the step, in which all these gene products cooperate, i.e. during preprimosome loading and chaperone-mediated release of DnaB from P protein inhibition.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Keywords: Key words Bacteriophage λ ; DnaA-DNA interactions ; Electron microscopy ; DNA-protein complexes ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interaction of the Escherichia coli DnaA (replication initiator) protein with restriction fragments of phage λ DNA demonstrated differential binding of DnaA along the whole λ DNA. Interaction of DnaA with the λ replication region (from the promoter p R to the origin of replication, oriλ) demonstrated a strong binding of DnaA to the region around the p o promoter where synthesis of a short antisense oop RNA is initiated. The four sequences protected by DnaA (two 9mers and two 5mers) are not related even to a relaxed DnaA box. The pattern of protection of these four sequences and the location of three DNase I hypersensitive sites in the λ DNA r strand, together with results of mobility shift assays and electron microscopy studies, may indicate an interaction involving DnaA monomers bound to different DNA positions on one side of the helix and the formation of higher-order nucleoprotein structures. Therefore, it is tempting to suggest that DnaA, in addition to its activity in regulation of replication and transcription, could be considered as a factor which structures certain chromosomal regions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 243 (1994), S. 374-378 
    ISSN: 1617-4623
    Keywords: Stringent control ; pBR322 replication ; Rom protein ; Amino acid starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The stringent response causes inhibition of replication of plasmid pBR322 in amino acid-starved Escherichia coli cells whereas in relaxed mutants the replication of this plasmid proceeds for several hours. On the basis of density shift experiments and pulse-labelling experiments we showed that most of the pBR322 molecules begin replication during the relaxed response and the rate of plasmid DNA synthesis in unstarved and isoleucine-starved relA −] bacteria is similar. We found that the Rom function plays a key role in the stringent control of plasmid pBR322 replication, as insertional inactivation of the rom gene causes amplification of pBR322rom − in both relA − and relA + strains during amino acid starvation. Moreover, pUC19, which is a pBR322-derived plasmid lacking the rom gene, behaves like pBR322rom −, whereas introduction of the rom gene into the pUC19 replicon drives it into the pBR322 mode of replication in amino acid-starved bacteria. A model for the regulation of pBR322 plasmid DNA replication by Rom protein in amino acid-starved Escherichia coli strains is proposed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1617-4623
    Keywords: Key words Stringent/relaxed response ; Bacteriophage λpR promoter ; Replication of λ plasmids ; dnaA ; Guanosine 5′-diphosphate-3′-diphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was previously demonstrated that the activity of bacteriophage λ promoter p R is decreased in wild-type Escherichia coli cells starved for amino acids (during the stringent response). Since p R activity is necessary for the transcriptional activation of oriλ, this leads to inhibition of the replication of plasmids derived from phage λ. These results led to the proposal that the p R promoter is susceptible to control by the stringent response. However, subsequent studies demonstrated that this promoter is activated by the host dnaA gene product and since the dnaA promoter was reported to be controlled by the stringent response, it is possible that the inhibition of p R activity in amino acid-starved cells is indirect, and results from the impairment of DnaA-mediated transcriptional activation. Here we present evidence that p R is negatively regulated by ppGpp, even when DnaA protein is provided in excess as well as in cells devoid of DnaA function. We have checked that the level of ppGpp is increased during prolonged (up to 4 h) starvation for isoleucine in relA + cells but not in the relA − mutant. At the same time we observed inhibition of λ plasmid replication during the stringent, but not relaxed, response, even when DnaA was overproduced. Finally, we found that the activity of a p R-lacZ fusion is inhibited after gratuitously induced overproduction of ppGpp in unstarved cells, irrespective of the status of the dnaA gene product. We conclude that the activity of the p R promoter is inhibited directly by ppGpp.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 261 (1999), S. 762-769 
    ISSN: 1617-4623
    Keywords: Key wordsdnaA function ; seqA function ; Membrane permeability ; Bacteriophage λRID=""ID="" 〈E6〉Acknowledgements〈/E6〉 We thank Monika Glinkowska for her help during construction of bacterial strains, and Walter Messer and Christoph Weigel for providing the &Dgr;〈E5〉seqA〈/E5〉::Tn〈E5〉10〈/E5〉 mutant and for discussions. This work was supported by Polish State Committee for Scientific Research (KBN project no. 6 P04A 016 16).RID=""ID="" Communicated by A. KondorosiRID=""ID="" 〈E5〉Correspondence to〈/E5〉 G. We¸grzyn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present evidence that biological properties of cell membranes are altered in dnaA and seqA mutants of Escherichia coli relative to wild-type bacteria. We found that bacteriophage λ forms extremely large plaques on the dnaA seqA double mutants. On the single mutants, dnaA and seqA, the plaques are also bigger than those formed on the wild-type host. However, no significant differences in intracellular phage λ development were observed between wild-type and mutant hosts, indicating that differences in burst size do not account for the observed differences in plaque size. On the other hand, more efficient release of the phage lytic proteins and/or higher sensitivity of the cell membranes to these proteins may result in more efficient cell lysis. We found that the efficiency of adsorption of bacteriophage λ to the dnaA seqA mutant cells is decreased at 0° C , but not at 30° C, relative to the wild-type strain. A considerable increase in the permeability of membranes of the mutant cells for β-galactosidase is demonstrated. The dnaA and seqA mutants are more sensitive to ethanol (an organic solvent) than wild-type bacteria, and the seqA strain and the double mutant dnaA seqA are very sensitive to deoxycholate (a detergent). We conclude that lesions in the genes dnaA and seqA result in alterations in cell membranes, such that the permeability and possibly also other properties of the membranes are significantly altered relative to wild-type bacteria.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1617-4623
    Keywords: Key words DnaA box ; DnaA protein ; Promoter ; Autoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The regulatory region of the Streptomyces dnaA gene comprises a single promoter and two DnaA boxes that are located upstream of the promoter. Comparative analysis of the dnaA promoter region from S. chrysomallus, S. lividans and S. reticuli revealed that the location, spacing and orientation of the DnaA boxes are conserved. In vitro studies demonstrated that efficient binding of the Streptomyces DnaA protein to DNA requires the presence of two DnaA boxes. In vivo analysis of dnaA promoter mutants deleted for one or both DnaA boxes indicated that the dnaA gene is autoregulated. However, the degree of derepression observed is relatively modest.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 258 (1998), S. 494-502 
    ISSN: 1617-4623
    Keywords: Key words Bacteriophage λ development ; Cold shock ; λ phage replication ; λ plasmid replication ; CII activator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was previously demonstrated that while lysogenic development of bacteriophage λ in Escherichia coli proceeds normally at low temperature (20–25° C), lytic development is blocked under these conditions owing to the increased stability of the phage CII protein. This effect was proposed to be responsible for the increased stimulation of the p E promoter, which interferes with expression of the replication genes, leading to inhibition of phage DNA synthesis. Here we demonstrate that the burst size of phage λcIb2, which is incapable of lysogenic development, increases gradually over the temperature range from 20 to 37° C, while no phage progeny are observed at 20° C. Contrary to previous reports, it is possible to demonstrate that p E promoter activation by CII may be more efficient at lower temperature. Using density-shift experiments, we found that phage DNA replication is completely blocked at 20° C. Phage growth was also inhibited in cells overexpressing cII, which confirms that CII is responsible for inhibition of phage DNA replication. Unexpectedly, we found that replication of plasmids derived from bacteriophage λ is neither inhibited at 20° C nor in cells overexpressing cII. We propose a model to explanation the differences in replication observed between λ phage and λ plasmid DNA at low temperature.
    Type of Medium: Electronic Resource
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