Conditional-lethal deoxyribonucleic acid ligase mutant of Escherichia coli.

A new Escherichia coli deoxyribonucleic acid (DNA) ligase mutant has been identified among a collection of temperature-sensitive DNA replication mutants isolated recently (Sevastopoulos, Wehr, and Glaser, Proc. Natl. Acad. Sci. U.S.A. 74:3485-3489, 1977). At the nonpermissive temperature DNA synthesis in the mutant stops rapidly, the DNA is degraded to acid-soluble material, and cell death ensures. This suggests that the mutant may be among the most ligase-deficient strains yet characterized.     

Rifampicin resistant DNA synthesis in phage T4 infected Escherichia coli

We have found that net DNA synthesis in T4 infected cells is rifampicin resistant. This finding implies that both the initiation of each T4 genome and its elongation are rifampicin resistant processes.     

Osmotic adaptation of T4 infected Escherichia coli

In contrast to enzymatic adaptation, osmotic adaption is possible with T4-infected Escherichia coli B cells. After an osmotic shift from 220 mOsM to 690 mOsM the intracellular content of potassium rises in infected cells as well as in uninfected cells. After osmotic shock the involved TrKA transport system shows an increased discrimination against rubidium (Rb⁺) and for potassium (K⁺).     

Role of deoxyribonucleic acid polymerases and deoxyribonucleic acid ligase in x-ray-induced repair synthesis in toluene-treated Escherichia coli K-12.

The biosynthesis of ribosomal ribonucleic acid (rRNA) In wild-type Neurospora crassa growing at 25 degrees C was investigated by continuous-labeling and pulsechase experiments using [5-3H]uridine. The results of these experiments suggest the following precursor-product relationships: the first RNA molecule to be synthesized in significant quantities is the 2.4 X 10(6)-dalton (2.4-Mdal) ribosomal precursor RNA. This RNA is cleaved to produce two species of RNA with weights of 0.7 and 1.4-Mdal. The former is the mature 17S rRNA of the 37S ribosomal subunit. The 1.4-Mdal RNA is subsequently cleaved to produce the mature 1.27-Mdal (25S) and 61,000-dalton (5.8S) rRNA's of the 60S ribosomal subunit. In the maturation process, approximately 15 to 20% of the 2.4-Mdal ribosomal precursor rRNA molecule is lost. As in other eukaryotes that have been examined, 5S rRNA is not derived from this precursor molecule.     

A stereochemical study of the mechanism of activation of donor oligonucleotides by RNA ligase from bacteriophage T4 infected Escherichia coli

RNA ligase from bacteriophage T4 infected Escherichia coli catalyzes the activation of adenosine 3',5'-bisphosphate (representing the donor oligonucleotide) by adenosine 5'-[(S)-alpha-17O,alpha,alpha-18O2]triphosphate with retention of configuration at P alpha. Since single-step enzyme-catalyzed nucleotidyl transfer reactions proceed with inversion, this stereochemical result provides support for a double displacement mechanism involving an adenylyl-enzyme intermediate as proposed previously from isotope exchange experiments.     

Altered properties of deoxyribonucleic acid polymerase I isolated from the membrane of bacteriophage T4-infected Escherichia coli.

Previous studies have shown that a large fraction of the host cell deoxyribonucleic acid (DNA) polymerase I (EC 2.7.7.7) becomes associated with the cell membrane shortly after infection with bacteriophages T4 and T7. The present investigation of the bound enzyme revealed that the polymerase activity can be eluted from the membrane with chelating agents, and that the material thus obtained shows many properties that distinguish it from purified DNA polymerase I. These include its chromatographic behavior, sedimentation rate, sensitivity to anti-DNA polymerase I antiserum, and activity with synthetic and natural DNA primers. Several of these physical and biological parameters were shown to revert slowly during storage to those exhibited by the purified enzyme. Efforts to determine whether the unusual properties of the membrane enzyme resulted from its association with DNA failed to support that possibility. These observations suggest that either the cause or the result of membrane binding of DNA polymerase I is a transient change in conformation or structure of the enzyme, with a resultant change in its enzymatic activity.     

Role of superinfecting phage in lysis inhibition with phage T4 in Escherichia coli

Rutberg, Blanka (Karolinska Institutet, Stockholm, Sweden), and Lars Rutberg. Role of superinfecting phage in lysis inhibition with phage T4 in Escherichia coli. J. Bacteriol. 90:891-894. 1965.-The ability of bacteriophage T4 to induce lysis inhibition upon superinfection was investigated after various treatments of the phage. This ability was found not to be a property of the external protein part of the phage, nor was it dependent on the functional and possibly structural integrity of the phage genetic material.