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Biomedical subjects

R A Warren

Publications and source records attributed to R A Warren.

At least 163 records · Page 9Linked to original sources
PubMed1980

Bacteriophage phi W-14-infected Pseudomonas acidovorans synthesizes hydroxymethyldeoxyuridine triphosphate.

The infection of Pseudomonas acidovorans with bacteriophage phi W-14 leads to the gradual disappearance of dTTP from the cells and to the appearance of hydroxymethy dUTP (hmdUTP). Infected-cell contain dUMP hydroxymethylase and activities converting hmdUMP to humdUDP and hmdUTP. Hydroxymethylase appears immediately after infection, reaching a maximum 20 min later. Thymidylate synthase activity decreases to less than 10% of the preinfection level during the initial 40 min after infection. Newly replicated DNA contains 2 to 3% hydroxymethyluracil. Although uracil is released from newly replicated DNA by acid hydrolysis, uracil is not incorporated as such into phi W-14 DNA, and dUTP is not present in the acid-soluble pool of infected cells. It is concluded that the thymine and alpha-putrescinylthymine in phi W-14 DNA are formed from hydroxymethyluracil at the polynucleotide level and that an intermediate in one or both of these conversions is degraded to uracil by acid hydrolysis. The modification of hydroxymethyluracil is coupled tightly to replication.

Bacteriophages↗
PubMed1980

Synthesis of thymine and alpha-putrescinylthymine in bacteriophage phi W-14-infected Pseudomonas acidovorans.

Host DNA synthesis stopped about 10 min after the infection of Pseudomonas acidovorans with bacteriophage phi W-14, but host DNA was not degraded to acid-soluble fragments. The synthesis of host but not of phage DNA was inhibited by 5-fluorodeoxyuridine. The nucleotide pools of infected cells did not contain dTTP, and infection resulted in the appearance of dTTPase activity. Although ornithine labeled the alpha-putrescinylthymine residues of phi W-14 DNA, ornithine-labeled nucleotides were not detected in infected cells. A new deoxynucleoside triphosphate did appear in infected cells, but it was not labeled by ornithine. It is concluded that the thymine and alpha-putrescinylthymine in phi W-14 DNA are synthesized at the polynucleotide level.

Bacteriophages↗
PubMed1979

Incompatibility group P-1 bla+ plasmids do not increase penicillin resistance of Pseudomonas acidovorans.

Incompatibility group P-1 plasmids with the bla+ genotype were transferred from various Escherichia coli strains to Pseudomonas acidovorans strain 29. When resistance to ampicillin was used as the criterion, none of these plasmids appeared able to express their Bla+ phenotype in this host. When the plasmids were subsequently transferred back from these ampicillin-sensitive P. acdiovorans transcipients to E. coli strains, it was found that the Bla+ phenotype was again expressed. Although beta-lactamase was not detected in cultures of P. acidovorans transcipients, macroiodometric determinations of beta-lactamase activity made on broken cell suspensions revealed that beta-lactamase was indeed synthesized. It was concluded that P. acidovorans strain 29 allows expression of the bla gene within the cell but that this organism is unable to excrete the enzyme.

Ampicillin↗
PubMed1979

Mixed bacteriophage infection of Escherichia coli: exclusion of superinfecting T4 by T7.

Escherichia coli was infected with T7, then with T4. When the time between the addition of the tow phages was 5 or more minutes, T4 was excluded and most of the infective centres yielded T7 progeny. The DNA of excluded T4 was injected, but it did not replicate nor was it degraded extensively. Transcription of this T4 DNA was largely inhibited, and the transcripts produced were not translated. A variety of T7 amber mutants was examined for the capacity to exclude T4. Amongst the early T7 genes, only the product of gene 1, the T7 RNA polymerase, was essential for T4 exclusion. None of the late genes examined was essential for exclusion.

DNA, Viral↗
PubMed1976

Polyamines in bacteriophage phi W-14 and in phi W-14-infected Pseudomonas acidovorans.

Bacteriophage phi W-14 is sensitive to osmotic shock. It contain sufficient free putrescine, 2-hydroxyputrescine and spermidine to neutralize about 15% of the DNA phosphates. The alpha-putrescinylthymine residues of the DNA could neutralize a further 25% of the phosphates. Label is transferred from ornithine to the alpha-putrescinyl residues of phi W-14 DNA. The rates of polyamine synthesis in Pseudomonas acidovorans are increased by phi W-14 infection.

Bacteriophages↗
PubMed1975

Alkali lability of bacteriophage phi W-14 DNA.

The molecular weight of bacteriophage phi W-14 DNA, determined by velocity sedimentation in neutral sucrose gradients, was 92 +/- 6 X 10(6). The DNA showed marked fragmentation in alkaline sucrose gradients. This fragmentation was not a consequence of preexisting single-strand interruptions in the DNA, since thermal denaturation of DNA yielded intact single strands. The alpha-putrescinylthymine groups in phi W-14 DNA appeared to be labile; some, or parts of some, of these groups were cleaved from the DNA in alkali.

Bacteriophages↗
PubMed1973

Studies on the biosynthesis of alpha-putrescinylthymine in bacteriophage phi W-14-infected Pseudomonas acidovorans.

The alpha-putrescinylthymine (putThy) in bacteriophage phiW-14 DNA is synthesized at the mononucleotide level: it is labeled by uracil or deoxyuridine but not by thymidine, and it appears in the acid-soluble pool of infected cells before the onset of phage DNA synthesis. The methylene group at the C-5 position of the pyrimidine moiety of putThy is derived in vivo from a C(1) unit. Extracts of a phage infected thymidine auxotroph of the host, Pseudomonas acidovorans, apparently contain a phage-specific thymidylate synthetase and a phage-specific activity which forms 5-hydroxymethyl dUMP from N(5), N(10)-methylene-tetrahydrofolate and dUMP.

Bacteriophages↗