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At least 343 records · Page 19Linked to original sources
PubMed1978

Exclusion of bacteriophage T1 by bacteriophage lambda. I. Early exclusion requires lambda N gene product and host factors involved in N gene expression.

Two modes of exclusion of T1 by lambda are distinguished. "Early" exclusion depends on gene N, but not on gene Q. It is at least partially ineffective against T1am23. "Late" exclusion depends on gene Q and effects T1am23 as well as T1+. Early exclusion is a direct effect of N gene product, rather than N gene being required for the expression of some other lambda gene. Three host mutations, groN, nusA, and nusB, known to interfere with lambda replication by affecting N gene expression, also interfere with the ability of lambda to exclude T1.

Coliphages↗
PubMed1979

Salmonella bacteriophage glycanases: endorhamnosidases of Salmonella typhimurium bacteriophages.

Twelve bacteriphages lysing only smooth Salmonella typhimurium strains were shown to have similar morphology--an icosahedric head to which a short, noncontractile tail carrying six spikes was attached. All phages degraded their lipopolysaccharide (LPS) receptors as shown by their ability to cleave off [14C]galactosyl-containing oligosaccharides from S. typhimurium cells labeled in their LPS. The oligosaccharides inhibited the alpha-D-galactosyl-specific Bandeiraea simplicifolia lectin agglutination of human type B erythrocytes, indicating that all 12 phage glycanases were of endorhamnosidase specificity, i.e., hydrolyzed the alpha-L-rhamnopyranosyl-(1 leads to 3)-D-galactopyranosyl linkage in the S. typhimurium O-polysaccharide chain. Two of the phages, 28B and 36, were studied in more detail. Whereas the phage 28B glycanase hydrolyzed the S. typhimurium LPS into dodeca- and octasaccharides, the phage 36 glycanase in addition cleaved off tetrasaccharides. Both phage enzymes hydrolyzed the O-polysaccharide chains of LPS from Salmonella belonging to serogroups A, B, and D1, which are built up of tetrasaccharide-repeating units identical except for the nature of the 3,6-dideoxyhexopyranosyl group (R). : FORMULA:(SEE TEXT). The phage 28B and 36 endorhamnosidases hydrolyzed also an LPS from which the 3,6-dideoxyhexosyl substituents had previously been hydrolyzed off. However, neither of the enzymes was active on LPS preparations in which the C2-C3 bond of the L-rhamnopyranosyl ring had been opened by periodate oxidation. Glucosylation at O-6 of the D-galactopyranosyl residues in the S. typhimurium LPS was found to be incompatible with hydrolysis by both enzymes. However, in an LPS glucosylated at O-4 of the D-galactopyranosyl residues, the adjacent alpha-L-rhamnopyranosyl linkages were found to be perferentially cleaved.

Glycoside Hydrolases↗
PubMed1969

Defective Bacteriophage PBSH in Bacillus subtilis: III. Properties of Adenine-16 Marker in Purified Bacteriophage Deoxyribonucleic Acid.

The adenine-16 (ade-16) marker (the marker nearest the chromosomal origin of Bacillus subtilis) in purified PBSH deoxyribonucleic acid (DNA) renatured more rapidly and to a greater extent than any other marker in the phage DNA, and more rapidly and to a greater extent than all markers, including ade-16, in bacterial DNA. The renaturation of the phage DNA ade-16 marker followed a first-order reaction, whereas renaturation of bacterial markers was initially a second-order reaction. No cross-linkages were detected in DNA molecules containing the ade-16 marker. Buoyant density measurements and inactivation by heat and micrococcal deoxyribonuclease of the ade-16 marker did not reveal large segments of clusters of the individual bases in these molecules. Alternative mechanisms for the unique renaturation behavior of the ade-16 marker are discussed.

Journal Article↗
PubMed1983

The bacteriophage P4 alpha gene is the structural gene for bacteriophage P4-induced RNA polymerase.

Two temperature-sensitive mutants of satellite phage P4 which do not synthesize P4 DNA at the nonpermissive temperature have been isolated. One of these phage is mutated in the P4 alpha gene. It complements a P4 delta mutant, but not a P4 alpha amber mutant; both mutants are phenotypically identical to alpha amber mutants in all properties studied. They synthesize P4 early proteins 1 and 2 as well as two additional P4-induced early proteins, 5 and 6, which are described here. P4 late proteins are not synthesized by these mutants and cannot be transactivated by helper phage P2. The mutants are unable to transactivate P2 late proteins from a P2 AB mutant. The P4 RNA polymerase activity which has been suggested to be involved in P4 DNA synthesis is not detected at the nonpermissive temperature. The P4 polymerase activity in partially purified extracts prepared from cells infected with the mutant at the permissive temperature is temperature sensitive. Reduced activity is found in vitro when these extracts are preincubated at 41 degrees C or assayed at temperatures higher than 37 degrees C. Thus, the P4 RNA polymerase is the product of the alpha gene. Temperature shift experiments show that the alpha gene product is required until late in the P4 cycle.

Coliphages↗
PubMed1984

Bacteriophage T4 bypass31 mutations that make gene 31 nonessential for bacteriophage T4 replication: mapping bypass31 mutations by UV rescue experiments.

The product of gene 31 is normally required for assembly of the T4 capsid. Two mutations that each bypass that requirement are shown to be located at separate sites in gene 23, which encodes the major structural protein of the capsid. A second phenotypic effect that characterizes both bypass31 mutant strains is the ability to multiply in host-defective strains, such as hdB3-1 and groEL mutants, on which wild-type T4 is unable to assemble capsids. The genetic data indicate that both phenotypic effects are due to the bypass31 mutation. Elimination of the requirement for both the phage protein, gp31, and the host protein, GroEL, by either of two single mutations in gene 23 indicates that GroEL and gp31 are normally needed to interact with gp23 in capsid assembly of wild-type T4.

DNA Replication↗
PubMed1971

Inhibition of T4 bacteriophage multiplication by superinfecting ghosts and the development of tolerance after bacteriophage infection.

Simultaneous addition of T4 phage and ghosts to host cells prevents infective center formation. Cells which have been infected with phage for less than 2 min are also inhibited by superinfecting ghosts. After this time, a chloramphenicol-inhibitable reaction occurs which causes the phage-infected cells to become increasingly tolerant of added ghosts.

Amino Acids↗
PubMed1971

Inhibition of replication of ribonucleic acid bacteriophage f2 by superinfection with bacteriophage T4.

Superinfection by phage T4 of cells infected by the ribonucleic acid (RNA) phage f2 results in inhibition of further f2 production. Experiments using rifampin show that the exclusion of f2 requires T4 gene function soon after T4 infection. By using a sensitive new peptide-mapping procedure to identify f2 coat protein in infected cells, we show that synthesis of the f2 coat occurs at a reduced level until 4 min after T4 superinfection and then ceases abruptly. Within 4 min after T4 superinfection, there are also several changes in f2 RNA metabolism, all of which require T4 gene function: preexisting f2 replicative intermediate RNA and f2 single-stranded RNA are degraded to small but still acid-precipitable fragments, and most f2-specific RNA is released from polyribosomes. We favor the hypothesis that T4 induces the synthesis of a specific endoribonuclease which degrades f2 RNA and that the inhibition of f2 protein synthesis may be a consequence of this degradation, rather than a direct effect of T4 upon translation.

Autoradiography↗
PubMed1972

Polyamines in the synthesis of bacteriophage deoxyribonucleic acid. I. Lack of dependence of polyamine synthesis on bacteriophage deoxyribonucleic acid synthesis.

To determine whether polyamine synthesis is dependent on deoxyribonucleic acid (DNA) synthesis, polyamine levels were estimated after infection of bacterial cells with ultraviolet-irradiated T4 or T4 am N 122, a DNA-negative mutant. Although phage DNA accumulation was restricted to various degrees in comparison to cells infected with T4D, nearly commensurate levels of putrescine and spermidine synthesis were observed after infection, regardless of the rate of phage DNA synthesis. We conclude from these data that polyamine synthesis after infection is independent of phage DNA synthesis.

Chromatography, Thin Layer↗
PubMed1975

Bacteriophage T7 Deoxyribonucleic acid replication in vitro. A protein of Escherichia coli required for bacteriophage T7 DNA polymerase activity.

In vivo, replication of T7 DNA does not occur after infection of Escherchia coli tsnC mutants (CHAMBERLIN, M. (1974) J. Virol. 14, 509-516). In vitro, extracts of tsnC mutant E. coli infected with T7 hage are incapable of replicating duplex T7 DNA, although extracts of wild type E. coli infected with T7 phage support replication of T7 DNA. In addition, extracts of the infected tsnC mutant are deficient in T7 DNA polymerase activity. Extracts prepared from uninfected E.coli tsnC-+ cells restore the ability of the infected tsnC extracts to replicate duplex T7 DNA, and also restore normal levels of the phage DNA polymerase activity. A 12,000-dalton heat-stable protein responsible for this complementation has been purified to near homogeneity from uninfected tsnC+ extracts and it is designated "TsnC protein."

Bacterial Proteins↗
PubMed1975

Bacteriophage T7 deoxyribonucleic acid replication invitro. Bacteriophage T7 DNA polymerase: an an emzyme composed of phage- and host-specific subunits.

The DNA polymerase induced after infection of Escherichia coli by phage T7 has been purified 500-fold to near homogeneity as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The purified enzyme complements extracts of cells infected with a T7 gene 5 mutant to permit cell-free replication of duplex T7 DNA. In contrast, purified T4 DNA polymerase or E. coli DNA polymerase I is unable to do so, thus suggesting a specific requirement for the T7 enzyme in the replication of the viral DNA. E. coli TsnC protein is present in purified T7 DNA polymerase in one-to-one stoichiometry with T7 gene 5 protein, and can be isolated in homogeneous form from heat-denatured enzyme by chromatography on DEAE-cellulose. The inactive form of T7 gene 5 protein that accumulates in tsnC hosts has been partially purified. When partially purified gene 5 protein is mixed with purified TsnC protein, DNA polymerase activity is restored, and formation of a one-to-one complex between the two proteins occurs. These results indicate that the functional form ofT7 DNA polymerase is a complex composed of phage- and host-specified subunits.

Bacterial Proteins↗
PubMed1975

Bacteriophage T7 deoxyribonucleic acid replication in vitro. Purification and properties of the gene 4 protein of bacteriophage T7.

The T7 gene 4 protein, a protein known from genetic analysis to participate in phage DNA replication in vivo, has been purified approximately 500-fold with an in vitro complementation assay. The protein, purified from cells infected with a T7 gene 4 temperature-sensitive mutant, is thermolabile, establishing that the complementation activity is in the protein product of the phage gene 4. The purified protein has no detectable nuclease, DNA polymerase, or RNA polymerase activity. However, in addition to stimulating the rate of DNA replication in crude extracts of T7 gene 4 mutant-infected cells, the gene 4 protein effects a marked stimulation of DNA synthesis by the purified T7 DNA polymerase when duplex T7 DNA is used as template. This effect is not observed when denatured T7 DNA is used as template, or when phage T4 DNA polymerase or Escherichia coli DNA polymerase I, II, OR III is substituted for the T4 enzyme. Analysis of the DNA synthesized by the T7 DNA polymerase in the presence of the gene 4 protein indicates that much of the product is in short DNA chains which are not covalently attached to the template. This result suggests a novel mechanism for the initiation of DNA chains in this reaction.

Bacterial Proteins↗