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  • 1
    Electronic Resource
    Electronic Resource
    Involvement of DnaK protein in mini-F plasmid replication: Temperature-sensitive seg mutations are located in the dnaK gene (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 183-189 
    Details
    ISSN: 1617-4623
    Keywords: dnaK gene ; seg mutations ; F plasmid ; Replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seg mutants (seg-1 and seg-2) of Escherichia coli cannot support the replication of the F factor and mini-F plasmids at 42°C. We cloned the wild-type E. coli chromosomal DNA fragment complementing the seg-1 and seg-2 mutations and found that both mutations were complemented by the wild-type dnaK gene coding for a heat shock protein. Transduction with phage P1 indicated that the seg-2 mutation is located at about 0.3 min in the region containing the dnaK gene in the order trpR-thrA-seg-2-leuB, consistent with the locus of the dnaK gene. Cloning and sequencing of the dnaK gene of the seg mutants showed that there was one base substitution within the dnaK gene in each mutant causing an amino acid substitution. These results indicate that the seg gene in which the seg-1 and seg-2 mutations occurred is identical to the dnaK gene. The mini-F plasmid pXX325 did not transform a dnaK null mutant to ampicillin resistance at 30°C in contrast to plasmids pBR322, pACYC184 and pSC101, which did. The active dnaK (seg) gene product is therefore essential for replication of the mini-F plasmid at both 30° and 42°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331267
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Purification and characterization of the sopB gene product which is responsible for stable maintenance of mini-F plasmid (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 431-436 
    Details
    ISSN: 1617-4623
    Keywords: F plasmid ; Plasmid stability ; DNA binding protein ; SopB protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mini-F plasmid has the trans-acting sopA, sopB genes and the cis-acting sopC DNA which are essential for plasmid partitioning. In this paper, we report the purification of the sopB gene product from extracts of cells harboring a pBR322 derivative carrying the sopB gene. The purity of the final preparation was more than 95%, as determined by densitometry. The amino acid sequence of the amino-terminal region of the protein for the 17 residues identified was identical to that predicted from the DNA sequence of the sopB gene. Therefore, it was concluded that the protein was the sopB gene product. Using anti-SopB serum, the SopB protein was detected in the cell lysates of F+, F′, and Hfr strains. The SopB protein bound to the plasmid DNA of a pBR322 derivative carrying the sopC DNA segment, but not to the vector plasmid pBR322.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332406
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Negative control of oriC plasmid replication by transcription of the oriC region (1985)
    Springer
    Molecular genetics and genomics 200 (1985), S. 21-26 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have demonstrated that the replication of the oriC plasmid, carrying the replication origin of the Escherichia coli chromosome, is inhibited by transcriptional readthrough from an oriC flanking region of the plasmid. This was drawn from an examination of the replication of an oriC plasmid, pKZ4, which bears the lacOP segment at the right-hand side of oriC (the asnA side) in such an orientation that transcription from the lac promoter proceeds towards oriC. Replication of pKZ4 was found to be drastically inhibited by inducing transcription from the lac promoter with IPTG, an inducer of the lactose operon. When trp transcription attenuator termination sequences were inserted near the right-hand end of the oriC region of pKZ4, the replication of the plasmid became considerably insensitive to the inhibitory effect of IPTG. This indicates that the inhibition is due to the frequent leftward transcription, which initiates at the lac promoter and proceeds into the oriC region. Since IPTG inhibits the replication of pKZ4, but not that of another coexisting oriC plasmid which is devoid of the lacOP segment, the replication inhibition is judged to act only in cis. Transcription from the promoter of the chloramphenicol resistance gene also caused the inhibition of oriC plasmid replication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383307
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Partitioning of the F plasmid: Overproduction of an essential protein for partition inhibits plasmid maintenance (1987)
    Springer
    Molecular genetics and genomics 208 (1987), S. 365-372 
    Details
    ISSN: 1617-4623
    Keywords: Plasmid incompabibility ; Plasmid partition ; F plasmid ; DNA sequencing ; Plasmid stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Multicopy plasmids carrying the sopB gene of the F plasmid inhibit stable inheritance of a coexisting mini-F plasmid. This incompatibility, termed IncG, is found to be caused by excess amounts of the SopB protein, which is essential for accuratepartitioning of plasmid DNA molecules into daughter cells. A sopB-carrying multicopy plasmid that shows the IncG+ phenotype was mutagenized in vitro and IncG negative mutant plasmids were isolated. Among these amber and missense mutants of sopB, mutants with a low plasmid copy number and a mutant in the Shine-Dalgarno sequence for translation of the SopB protein were obtained. These results demonstrate that the IncG phenotype is caused by the SopB protein, and that the incompatibility is expressed only when the protein is overproduced. This suggests that the protein must be kept at appropriate concentrations to ensure stable maintenance of the plasmid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328125
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    Paper (German National Licenses)
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