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At least 325 records · Page 18Linked to original sources
PubMed1973

Regulation of early mRNA synthesis in bacteriophage T4-infected bacteria: dependence on bacteriophage-specific protein synthesis.

The mechanism of the transcriptional turn-off was studied for those species of mRNA in T4 infection which specify early phage proteins. Total synthesis of these early RNA species was determined by short-time labeling with uracil-5-(3)H after the infection of Escherichia coli B with DNA-negative, conditional lethal mutants, which produce no late mRNA under nonpermissive conditions. With both amber and temperature-sensitive mutants a decrease in incorporation into early RNA by more than 90% was observed within 15 min after infection. Analysis by thin-layer chromatography showed uracil-5-(3)H to enter nucleotide pools throughout the infection cycle. The observed decrease in early RNA synthesis was dependent on protein synthesis, since it could be prevented by chloramphenicol. By varying the time of chloramphenicol addition, the effect of this regulatory protein(s) was found to appear at 3 to 4 min and reached its full extent at 10 to 15 min after infection. The turn-off of transcription of a defined early gene was studied by 5-fluorouracil (FU) rescue of an early, DNA-negative, amber mutant (gene 1, deoxynucleotide kinase) at different times after infection. DNA synthesis could be rescued by FU addition early after infection, but not after 12 min. 5-fluorouracil was efficiently taken up into the nucleotide pools also at late times, as shown by thin-layer chromatography. After incubation in the presence of chloramphenicol from 3 min after infection, DNA synthesis could be rescued as late as 45 min after infection. Thus, when protein synthesis was blocked during the early period of infection, the shut-off of transcription of the studied early gene was prevented.

Carbon Isotopes↗
PubMed1974

Phospholipase activity in bacteriophage-infected Escherichia coli. I. Demonstration of a T4 bacteriophage-associated phospholipase.

Phospholipase activity has been found to be associated with T4 phage and T4 ghost particles. The attachment of the phospholipase to the phage persists during purification through cesium chloride gradients and dialysis, indicating that it is firmly bound. The presence of the enzymatic activity on T4 ghosts suggests that it is not normally packaged within the head of the virus. The enzyme has specificity for phosphatidylglycerol and its activity is stimulated by 0.1% Triton X-100 and 20% methanol. It does not have a requirement for Ca(2+) and is inactivated at temperatures above 60 C. The association of the phospholipase with T4 phage grown in a phospholipase-deficient host and its absence on unsuppressed T4amtA3 suggests that it may be phage gene specific.

Calcium↗
PubMed1975

Hexamer of bacteriophage f2 coat protein as a repressor of bacteriophage RNA polymerase synthesis.

Formation of complex I between phage f2 RNA and coat protein, leading to repression of phage RNA polymerase synthesis, depends nonlinearly upon the concentration of the coat protein. Maximum formation of complex I was observed when six molecules of coat protein were bound to one molecule of RNA. RNase digestion of a glutaraldehyde-fixed complex left, as the products, coat protein oligomers. The heaviest, hexamers, predominated in the mixture. It was also shown that, in an ionic environment required for phage protein synthesis, coat protein at a concentration optimum for complex I formation exists in solution as a dimer. The results indicate that the translational repression of the RNA polymerase cistron is due to a cooperative attachment to phage template of three dimers of coat protein, forming a hexameric cluster on an RNA strand.

Centrifugation, Density Gradient↗
PubMed1975

Escherichia coli capsule bacteriophages. IV. Primary structure of the bacteriophage 29 receptor, the E. coli serotype 29 capsular polysaccharide.

Using periodate oxidation, methylation analysis, characterization of oligosaccharides by Smith degradation or partial acid hydrolysis, as well as proton magnetic resonance, the primary structure of the Escherichia coli serotype 29 capsular polysaccharide (the receptor of E. coli K phage 29) was reinvestigated. The polymer was found to consist of hexasaccharide repeating units of the following structure: (see article).

Binding Sites↗
PubMed1975

Bacteriophage T4 baseplate components. II. Binding and location of bacteriophage-induced dihydrofolate reductase.

The location of T4D phage-induced dihydrofolate reductase (dfr) has been determined in intact and incomplete phage particles. It has been found that phage mutants inducing a temperature-sensitive dfr (dfrts) procude heat-labile phage particles. The structural dfr produced by these ts mutants was shown to assume different configurations depending on the temperature at which the phage is assembled. Morphogenesis of incomplete phage particles lacking the gene 11 protein on their baseplates was found to be inhibited by reagents binding to dfr, such as antibodies to dfr. Further, cofactor molecules for dfr, such as reduced nicotinamide adenine dinucleotide phosphate and reduced nicotinamide adenine dinucleotide, also inhibited the step in morphogenesis involving the addition of gene 11 product. On the other hand, inhibitors of dfr, such as adenosine dephosphoribose, stimulated the addition of the gene 11 protein. It has been concluded that the phage-induced dfr is a baseplate component which is partially covered by the gene 11 protein. The properties of phage particles produced after infection of the nonpermissive host with the one known T4D mutant containing a nonsense mutation in its dfr gene suggested that these progeny particles contained a partial polypeptide, which was large enough to serve as a structural element.

Adenine Nucleotides↗
PubMed1975

Bacteriophage T4 baseplate components. III. Location and properties of the bacteriophage structural thymidylate synthetase.

Two T4D thymidylate synthetase (td) temperature-sensitive mutants have been isolated and characterized. Both mutants produce heat-labile phage particles. This observation supports the view that this viral-induced protein is a phage structural component. Further, antiserum to td has been shown to block a specific step in tail plate morphogenesis. The results indicated that the td protein is largely covered by the T4D tail plate gene 11 protein. Since the phageinduced dihydrofolate reductase (dfr) also is partially covered by the gene 11 protein, it appears that td was adjacent to the tail plate dfr. This location has been confirmed by constructing a T4D mutant which is dfrtstdts and showing that these two tail plate constituents interact and give altered physical properties to the phage particles produced. A structural relationship for the tail plate folate, dfr, and td has been reported.

Coliphages↗
PubMed1976

Red system of bacteriophage lambda complements the growth of a bacteriophage T1 gene 4 mutant.

The ability of phage lambda to complement the growth of T1am23, a T1 gene 4 mutant with a DNA arrest phenotype, has been shown to require both lambda Red functions, redX and redB. lambdagam function, however, is not required. Therefore, the lambda Red function can substitute for T1 gene 4 function. However, T1+ does not substitute for lambda Red in allowing lambda to grow in a polA host.

Chromosome Mapping↗
PubMed1976

Properties of condensed bacteriophage T4 DNA isolated from Escherichia coli infected with bacteriophage T4.

Methods developed for isolating bacterial nucleoids were applied to bacteria infected with phage T4. The replicating pool of T4 DNA was isolated as a particle composed of condensed T4 DNA and certain RNA and protein components of the cell. The particles have a narrow sedimentation profile (weight-average s=2,500S) and have, on average, a T4 DNA content similar to that of the infected cell. Their dimensions observed via electron and fluorescence microscopy are similar to the dimensions of the intracellular DNA pool. The DNA packaging density is less than that of the isolated bacterial nucleoid but appears to be roughly similar to its state in vivo. Host-cell proteins and T4-specific proteins bound to the DNA were characterized by electrophoresis on polyacrylamide gels. The major host proteins are the RNA polymerase subunits and two envelope proteins (molecular weights, 36,000 and 31,000). Other major proteins of the host cell were absent or barely detectable. Single-strand breaks can be introduced into the DNA with gamma radiation or DNase without affecting its sedimentation rate. This and other studies of the effects of intercalated ethidium molecules have suggested that the average superhelical density of the condensed DNA is small. However, these studies also indicated that there may be a few domains in the DNA that become positively supercoiled in the presence of high concentrations of ethidium bromide. In contrast to the Escherichia coli nucleoid, the T4 DNA structure remains condensed after the RNA and protein components have been removed (although there may be slight relaxation in the state of condensation under these conditions).

Bacterial Proteins↗
PubMed1968

Escherichia coli K bacteriophages. I. Isolation and introductory characterization of five Escherichia coli K bacteriophages.

A set of five Escherichia coli K phages has been isolated. These phages are adsorbed to and lyse the capsular forms of the host bacteria, whereas their spontaneous, acapsular mutants are not affected. All host strains are heavily encapsulated test strains for E. coli K antigens of the thermostable A type and they readily segregate acapsular mutants. In four of the phage-host systems, all secondary growth obtained was found to be acapsular. When tested for host-range mutants on 38 strains of E. coli and Klebsiella, less than one mutant per 10(5) plaque-forming units was found. No cross-reacting neutralizing antibodies were obtained when rabbits were immunized with the K phages. The latent periods (between 16 and 30 min) and average burst sizes (between 145 and 580) were determined by one-step growth experiments.

Adsorption↗
PubMed1977

Bacteriophage proteins associated with the bacterial membrane after bacteriophage T7 infection.

The majority of the phage-induced proteins made after T7 infection of Escherichia coli are tightly associated with the bacterial membrane. Many of these have been identified. Selective extraction of proteins from these membranes by the detergent Sarkosyl or the chaotropic agent guanidine-hydrochloride indicated that most of these proteins are an integral part of the cytoplasmic membrane and the cell wall. No major changes in the distribution of bacterial proteins in the membrane were observed as a consequence of phage T7 infection.

Cell Membrane↗
PubMed1977

Transduction of bacteriophage Mu by bacteriophage T1.

Phage T1 transduces phage Mu PFU from Mu-lysogenic donor cells to sensitive recipient cells. The efficiency of transduction depends on the chromosomal location of the Mu prophage. T1, therefore, appears to package different regions of the bacterial chromosome with different efficiencies. Although T1 transduces bacterial markers with different efficiencies, there is no direct correlation between the efficiency of transduction of a bacterial marker and the efficiency of transduction of Mu PFU from donor cells with the Mu prophage located in that marker.

Coliphages↗