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  • 1
    Electronic Resource
    Electronic Resource
    Cysteinyl residues of Escherichia coli recA protein (1984)
    s.l. : American Chemical Society
    Biochemistry 23 (1984), S. 2363-2367 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00306a006
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  • 2
    Electronic Resource
    Electronic Resource
    Utilization of exogenous folate in the human malaria parasite Plasmodium falciparum and its critical role in antifolate drug synergy (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The antifolate combination pyrimethamine/sulphadoxine (PYR/SDX; Fansidar) is frequently used to combat chloroquine-resistant malaria. Its success depends upon pronounced synergy between the two components, which target dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) in the folate pathway. This synergy permits clearance of parasites resistant to either drug alone, but its molecular basis is still unexplained. Plasmodium falciparum can use exogenous folate, which is normally present in vivo, bypassing SDX inhibition of DHPS and, apparently, precluding synergy under these conditions. However, we have measured parasite inhibition by SDX/PYR combinations in assays in which folate levels are strictly controlled. In parasites that use exogenous folate efficiently, SDX inhibition can be restored by levels of PYR significantly lower than those required to inhibit DHFR. Isobolograms show that the degree of synergy between PYR and SDX is highly dependent upon prevailing folate concentrations and are indicative of PYR acting to block folate uptake and/or utilization. No significant synergy was observed at physiological drug levels when PYR/SDX acted on purified DHFR, whether wild type or mutant. We conclude that the primary basis for antifolate synergy in these organisms arises from PYR targeting a site (or sites) in addition to DHFR, which restores DHPS as a relevant target for SDX.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01437.x
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  • 3
    Electronic Resource
    Electronic Resource
    Replication of ColE2 and ColE3 plasmids: The regions sufficient for autonomous replication (1988)
    Springer
    Molecular genetics and genomics 212 (1988), S. 225-231 
    Details
    ISSN: 1617-4623
    Keywords: ColE2 and ColE3 ; Autonomous replication ; Trans-acting factor ; Origin ; Plasmid specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have localized the regions sufficient for autonomous replication on the genomes of the colicin E2 (ColE2) and colicin E3 (ColE3) plasmids and analyzed the replication functions carried by these regions. A 1.3 kb segment of each plasmid is sufficient for autonomous replication. Plasmids carrying this segment retain the replication properties of the original plasmid. The 1.3 kb segment consists of three functional portions. Firstly, a 0.9 kb region which specifies at least one trans-acting factor required for replication of each plasmid. Secondly, a 0.4 kb region located adjacent to one end of the 0.9 kb region, which is required for expression of the trans-acting factor(s) and probably contains the promoter. The region across the border of these two portions of ColE2 is involved in copy number control of the plasmid. The third portion is a 50 bp region adjacent to the other end of the 0.9 kb region, which contains a cis-acting site (origin) where replication initiates in the presence of the trans-acting factor(s). The action of the trans-acting factor(s) on the origin is plasmid specific. The 50 bp regions functioning as the origins of replication of ColE2 and ColE3 are the smallest among those in prokaryotic replicons so far identified and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334689
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  • 4
    Electronic Resource
    Electronic Resource
    Replication of ColE2 and ColE3 plasmids In vitro replication dependent on plasmid-coded proteins (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 249-255 
    Details
    ISSN: 1617-4623
    Keywords: ColE2 and ColE3 ; In vitro DNA replication ; Rep protein ; Replication origin ; Plasmid specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We developed an in vitro replication system for ColE2 and ColE3 plasmids using cell extracts prepared from bacteria with or without these plasmids. DNA synthesis depended on host DNA polymerase I and was sensitive to rifampicin and chloramphenicol. Preincubation of the extracts with plasmid DNA, however, allowed replication of template DNA added subsequently in a plasmid-specific manner in the presence of rifampicin and chloramphenicol. The plasmid-specified trans-acting factor(s) was detected in cell extracts from bacteria carrying a recombinant plasmid with the region of ColE2 or ColE3 encoding the Rep protein. The plasmid-specified factor(s) consisted at least in part of protein, probably the Rep protein. In vitro replication started within a region of ColE2 or ColE3 containing the smallest cis-acting segment essential for in vivo replication and proceeded in a fixed direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261184
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  • 5
    Electronic Resource
    Electronic Resource
    Functional domains of Escherichia coli recA protein deduced from the mutational sites in the gene (1984)
    Springer
    Molecular genetics and genomics 193 (1984), S. 288-292 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The sites of recA mutations of Escherichia coli, recA441 (tif-1), recA1, recA430 (lexB30) and recA44, were determined by analyses of the nucleotide sequences. All mutations are single point missense mutations within the coding region of the recA gene. In the recA441, recA1, recA430 and recA44 proteins, the 38th, 160th, 204th, and 246th amino acids, respectively, from the amino terminal ends are altered. Based on the properties of these mutant proteins and modified forms of recA protein, the locations of various regions of the recA protein that are involved in binding with ATP, binding with single-stranded DNA, hydrolysis of ATP, interaction between the recA protein molecules and interaction with the λcI or lexA repressors are mapped on the primary structure of the protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330682
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  • 6
    Electronic Resource
    Electronic Resource
    Replication of ColE2 and ColE3 plasmids: Two ColE2 incompatibility functions (1988)
    Springer
    Molecular genetics and genomics 214 (1988), S. 451-455 
    Details
    ISSN: 1617-4623
    Keywords: ColE2 and ColE3 ; Incompatibility ; Copy number control ; Trans-acting factor ; Origin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have identified and localized two incompatibility determinants (IncA and IncB) within a 1.3 kb segment of ColE2 sufficient for autonomous replication. The IncA determinant is localized in a region shorter than 250 bp and expresses incompatibility against both ColE2 and ColE3. The region which determines sensitivity to the IncA determinant seems to overlap with the region specifying the IncA determinant. The expression of the trans-acting factor(s) specifically required for replication of ColE2 interferes with expression of the IncA determinant against ColE2 but not against ColE3. The IncA determinant might be at least partly responsible for the copy number control of the plasmid. The IncB determinant is localized in a 50 bp region (origin) which is sufficient for initiation of replication in the presence of the trans-acting factor(s). The IncB determinant is specific for ColE2 and seems to be due to titration of the trans-acting essential replication factor(s) by binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330479
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and functional organization of ColE2 and ColE3 replicons (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 209-216 
    Details
    ISSN: 1617-4623
    Keywords: ColE2 and ColE3 ; Nucleotide sequence ; Trans-acting replication protein ; Origin ; Plasmid specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The complete nucleotide sequences of the 1.5 kb regions of ColE2 and ColE3 plasmids containing the segments sufficient for autonomous replication have been determined. They are quite homologous (greater than 90%), indicating that these two plasmids share common mechanisms of initiation of replication and its regulation. An open reading frame with a coding capacity for a protein of about 300 amino acids is present in both ColE2 and ColE3 and it actually specifies the Rep (for replication) protein, which is the plasmid specific trans-acting factor required for autonomous replication. The amino acid sequences of the Rep proteins of ColE2 and ColE3 are quite homologous (greater than 90%). The cis-acting sites (origins) where replication initiates in the presence of the trans-acting factors consist of 32 bp for ColE2 and 33 bp for ColE3. They are the smallest of all the prokaryotic replication origins so far reported. They are nonhomologous only at two positions, one of which, a deletion of a single nucleotide in ColE2 (or an insertion in ColE3), determines the plasmid specificity in interaction of the origins with the Rep proteins. Both plasmids carry a region with an identical nucleotide sequence and the one in ColE2, the IncA region, has been shown to express incompatibility against both ColE2 and ColE3. These results indicate that these plasmids share a common IncA determinant. A possibility that a small antisense RNA is involved in copy number control and incompatibility (IncA function) was suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339719
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