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At least 55 records · Page 3Linked to original sources
PubMed1980

DNA-RNA polymerase complexes associated with the membrane from bacteriophage T2- or T4-infected Escherichia coli. II. A comparison of in vitro RNA with the in vivo RNA products.

Membrane preparations, containing DNA-RNA polymerase from bacteriophage T2- or T4-infected Escherichia coli, caused the asymmetric synthesis of RNA classes similar to those produced sequentially in vivo: 1, Pre-early RNA was formed when a membrane preparation was isolated 1 min after infection. 2, Pre-early and delayed early RNA, in roughly the same proportion as that obtained in vivo, was synthesized by a preparation obtained 6 min after infection. 3, Pre-early, delayed early and late genes were transcribed by preparations isolated from cells during the late period of infection. In late preparations, however, less late and more pre-early RNA was usually synthesized in vitro than that obtained in vivo. Late RNA was not synthesized when a phage T4 mutant defective in either gene 33 or gene 55 was used. Evidence is presented to show that late RNA synthesis cannot solely be accounted for from the completion of already initiated chains.

Cell Membrane↗
PubMed1977

RNA-linked nascent DNA pieces in T7 phage-infected Escherichia coli cells. I. Role of gene 6 exonuclease in removal of the linked RNA.

The presence of RNA-linked nascent DNA pieces in T7 phage-infected Escherichia coli cells has been shown by the selective degradation of the 5'-hydroxyl-terminated nascent DNA, produced by alkali or RNase treatment, with spleen exonuclease. At 43 degrees C, the proportion of RNA-linked DNA pieces in nascent short dna is 50 to 60% in T7 ts136 (ts mutant of gene 6) phage-infected E. coli, whereas that in T7 wild-type phage-infected cells is less than 6%. Joining of the nascent pieces is greatly retarded in T7 ts136-infected E. coli temperature sensitive polA mutants at 43 degrees C. These results suggest that gene 6 exonuclease plays a role in removal of the linked RNA during the discontinuous replication of T7 DNA.

Animals↗
PubMed1975

Transcription of bacteriophage T4 genome in vitro. Heterogeneity of RNA polymerase in crude extracts of normal and T4-infected Escherichia coli B.

In order to obtain RNA polymerase preparations carrying the necessary specificity determinants to transcribe the delayed-early genes of bacteriophage T4, crude extracts of uninfected and T4-infected Escherichia coli were fractionated in glycerol gradients of low ionic strength. In contrast to the reported sedimentation behavior of the purified enzyme, the RNA polymerase activity in crude extracts of normal and infected cells sedimented heterogeneously over a wide range of sedimentation coefficients. When the "heavy" (24-33 S) and "light" (14-20 S) regions of the gradient were precipitated with ammonium sulfate and recentrifuged, the former split into two subfractions, one again sedimenting heavy and the other sedimenting light. The latter did not split under the same conditions. The resulting subfractions from uninfected cell extracts had different thermal thermal stabilities at 50 degrees (half-lives ranging from 2-3 to 25 min) while those from T4-infected cell extracts were very thermolabile (half-life of 1-2 min). All the subfractions were more active on T4 DNA than on calf-thymus DNA. They also formed rifampicin-resistant, RNA chain initiation complexes with T4 DNA. Based on the kinetics of heat inactivation with T4 and calf thymus DNAs as templates and preferential transcription of T4 DNA, it is proposed that the T4-infected cell enzymes prepared as described here harbor heat-labile initiation factor(s). During infection the heavy sedimenting RNA polymerase activity disappears after 2.5 min at 37 degrees. This appears to require phage-specific protein synthesis because (a) it does not happen in the presence of chloramphenicol and (b) it does not happen in T4 ghost-infected cells.

Coliphages↗
PubMed1975

F-Factor-mediated restriction of bacteriophage T7: protein synthesis in cell-free systems from T7-infected Escherichia coli F- and F+ cells.

A characteristic phenomenon in the F-factor-mediated inhibition of T7 phage is a virtual absence of T7 late protein synthesis in T7-infected Escherichia coli male cells, in spite of the presence of T7 late mRNA which is translatable in vitro when isolated from the cell. To determine whether the translational defect in T7-infected F+ cells is due to a T7 late mRNA-specific translational block, or to a general decrease of F+ cell translational activity, we compared the activities of cell-free, protein-synthesizing systems prepared from isogenic F- and F+ cells harvested at different times of T7 infection. The cell-free systems from uninfected F- and F+ cells translated T7late mRNA equally as well as MS2 RNA and T7early mRNA. The activity of cell-free systems from T7-infected F+ cells to translate MS2 RAN, T7 early mRNA, and T7 late mRNA decreased concomitantly at a much faster rate than that of T7-infected F- cells. Therefore, the abortive infection of F+ cells by T7 does not result from a T7 late mRNA-specific translational inhibition, although a general reduction of the translational activity appears to be a major factor for the inability of the F+ cells to produce a sufficient amount of T7 late proteins.

Cell-Free System↗
PubMed1980

A DNA-dependent ATPase from T4-infected Escherichia coli. Purification and properties of a 63,000-dalton enzyme and its conversion to a 22,000-dalton form.

A DNA-dependent ATPase with a molecular weight of 63,000 has been purified to near homogeneity from T4-infected Escherichia coli. This enzyme is not present in uninfected E. coli. It is present in E. coli infected with amber mutants of gene 44 or gene 62 and with the data mutant. The enzyme can be eluted from single-stranded DNA-cellulose at NaCl molarities greater than 0.6 M and from ATP agarose with 80 mM MgATP. The enzyme hydrolyzes MgATP or MgdATP to the diphosphates with equal maximum velocities and the Km values are 0.30 and 0.75 mM, respectively. The enzyme hydrolyzes MgCTP with 13% and MgUTP with 7% of the velocity observed with MgATP. Apparent Km values are reported for single-stranded T4 DNA and for a series of synthetic polynucleotides. The 63,000-dalton enzyme can be cleaved proteolytically to an active 22,000-dalton form. This can be demonstrated by storage of infected cells, by mixing of cell extracts, and by inhibition with phenylmethylsulfonyl fluoride. The Mr = 22,000 enzyme cross-reacts with antibody made to the Mr = 63,000 enzyme. This antibody inhibits the 22,000-dalton species. The 22,000-dalton enzyme forms a complex with gene 32 protein in the absence of DNA.

Adenosine Triphosphatases↗
PubMed1980

Isolation and characterization of a putative bacteriophage T5 transcription.replication enzyme complex from infected Escherichia coli.

A well defined enzyme comples of approximately 5 X 10(6) daltons that contains phage and host cell components known to be required for the processes of phage transcription and DNA replication has been isolated from bacteriophage T5-infected Escherichia coli cells. In addition to the RNA polymerase of the host cell, the complex contains the phage-encoded: gpC2 which has been implicated genetically as a controlling element of late transcription; gpD9, the DNA polymerase required for T5 DNA replication; the proteins gpD5 (DNA-binding protein), and gpD15 (nuclease) which are both known to be essential for T5 DNA replication and for the initiation of late transcription. The viral gpD5 derived from the purified complex is a phosphoprotein. The enzyme complex also contains, protected from the action of nuclease, double-stranded DNA with an approximate molecular weight of 1 to 2 X 10(6) (2 to 3% of the size of the T5 genome) which is derived preferentially from the center of the T5 DNA molecule. The composition of the enzyme complex suggests that the processes of transcription and replication are integrated in T5-infected cells.

DNA Helicases↗
PubMed1989

Bacteriophage T4 DNA topoisomerase is the target of antitumor agent 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) in T4-infected Escherichia coli.

The mammalian type II DNA topoisomerase has been proposed to be the intracellular target of a variety of antitumor agents, including m-AMSA [4'-(9-acridinylamino)-methanesulfon-m-anisidide]. Because the bacteriophage T4-encoded topoisomerase resembles the mammalian enzyme, we are using T4 as a simple model system to investigate the mechanism of action of m-AMSA. A mutation that renders T4 growth m-AMSA-resistant is closely linked to an amber mutation in T4 gene 39, which encodes one of the topoisomerase subunits. In addition, the gene 39 subunit from the m-AMSA-resistant mutant phage has an altered net charge, strongly indicating that the drug-resistance mutation is within gene 39. Topoisomerase purified from mutant phage-infected Escherichia coli exhibits drug-insensitive DNA relaxation and DNA cleavage activities. Because a single mutation results in both drug-resistant phage growth and a drug-insensitive viral topoisomerase, we conclude that the T4-encoded type II DNA topoisomerase is the physiological target of m-AMSA in phage-infected E. coli.

Amsacrine↗
PubMed1995

Resolution time of Escherichia coli cystitis is correlated with levels of preinfection antibody to the infecting Escherichia coli strain.

OBJECTIVES: A number of studies in animals have demonstrated that immunization against uropathogenic bacteria can lessen the severity or duration of induced urinary tract infections (UTI). This study examined whether preinfection levels of serum or urinary anti-Escherichia coli antibodies were correlated with length of time needed to resolve an induced E coli cystitis. METHODS: Serum and urine anti-E coli antibody levels in 36 control and 42 vaginally immunized cynomolgus monkeys were measured by enzyme-linked immunosorbent assay. Regression analyses were used to determine correlations between resolution time and preinfection antibody level, and to estimate antibody levels that might be associated with effective resolution of an E coli UTI. RESULTS: Linear regression analysis showed significant correlations between short resolution time and high levels of serum immunoglobulin M (IgM), urinary secretory IgA, and urinary IgG specific for the infecting E coli strain. Serum IgM and urinary IgG anti-E coli levels in monkeys that cleared infections early were significantly higher than in animals with protracted infections. Logistic regression estimated the serum IgM and urinary IgG anti-E coli levels associated with a 50% probability of accelerated clearance to be 3.3 micrograms/mL and 2.7 micrograms/24 hours, respectively. CONCLUSIONS: For this primate model, the observed correlations between short resolution time and pre-existing serum and urinary antibody suggest that antibody-mediated immunity is an important component of host defense against UTI.

Animals↗
PubMed1983

Structure of the 2-keto-3-deoxy-D-manno-octonic-acid-containing capsular polysaccharide (K12 antigen) of the urinary-tract-infective Escherichia coli O4:K12:H-.

The primary structure of the K12 antigenic capsular polysaccharide (K12 antigen) of Escherichia coli O4:K12:H- was elucidated by composition, nuclear magnetic resonance spectroscopy, methylation, periodate oxidation and oligosaccharide analysis. The polysaccharide consists of repeating trisaccharide alpha-rhamnosyl-1,2-alpha-rhamnosyl-1,5-dOclA units (dOclA = 2-keto-3-deoxy-D-manno-octonic acid) which are joined through beta-2,3-linkages. About 50% of the dOclA units are O-acetylated at C7 or C8. The sequence of acetylated and non-acetylated dOclA residues is not known. As had been reported before, the polysaccharide is linked to a phosphatidic acid at the reducing end (dOclA) via a phosphodiester bridge. The serologically specific part of the K12 antigen is its polysaccharide moiety.

Antigens↗
PubMed1981

Construction and expression of recombinant plasmids encoding type 1 or D-mannose-resistant pili from a urinary tract infection Escherichia coli isolate.

Isolates of Escherichia coli from human urinary tract infections frequently express adherence properties found less often among normal intestinal isolates. These properties include adherence to human uroepithelial cells and primary monkey kidney cells, as well as D-mannose-resistant hemagglutination of human erythrocytes, and they are mediated by a pilus type different from type 1. The genes encoding this pilus type (pyelonephritis-associated pili, pap) and those encoding type 1 pili have been cloned from a urinary tract infection isolate of E. coli and transferred to an E. coli K-12 derivative. The recombinant plasmids were found to express functional pili and to endow the new host with all of the adherence properties of the urinary tract infection isolate. Both pilus types were found to be genetically distinct, and unlike the adherence genes from bovine, porcine, and human diarrheal isolates, both were found to be chromosomally encoded.

Adhesiveness↗
PubMed1992

Role of fimbrial adhesins in the pathogenesis of Escherichia coli infections.

Escherichia coli strains are able to cause intestinal (enteritis, diarrhoeal diseases) and extraintestinal (urinary tract infections, sepsis, meningitis) infections. Most pathogenic E. coli strains produce specific fimbrial adhesins, which represent essential colonization factors: intestinal E. coli strains very often carry transferable plasmids with gene clusters specific for fimbrial adhesins, like K88 and K99, or colonization factor antigens (CFA) I and II. In contrast, the fimbrial gene clusters of extraintestinal E. coli strains, such as P, S, or F1C fimbriae, are located on the chromosomes. The fimbrial adhesin complexes consist of major and minor subunit proteins. Their binding specificity can generally be assayed in hemagglutination tests. In the case of fimbrial adhesins of intestinal E. coli strains, the major subunit proteins preferentially represent the hemagglutinating adhesins, whereas minor subunit proteins are the hemagglutinins of extraintestinal E. coli strains. Recently "alternative" adhesin proteins were identified, which have the capacity to bind to eukaryotic structures different from the receptors of the erythrocytes. Fimbrial adhesins are not constitutively expressed but are stringently regulated on the molecular level. Extraintestinal E. coli wild-type strains normally carry three or more fimbrial adhesin determinants, which have the capacity to influence the expression of one another (cross talk). Furthermore the fimbrial gene clusters undergo phase variation, which seems to be important for their contribution to pathogenesis of E. coli.

Animals↗
PubMed1971

Occurrence of lysophosphatides in bacteriophage T4rII-infected Escherichia coli S-6.

Hydrolysis of phospholipids was observed to start about 15 min after Escherichia coli S/6 cells were infected with T4rII bacteriophage mutants. Hydrolysis continued through the latent period and well past the time when cell lysis occurs. The hydrolytic products that accumulated were free fatty acids, 2-acyl lysophosphatidylethanolamine, and various lysocardiolipins. These products indicated the action of phospholipase A(1). From 15 to 22 min after infection, there were equivalent amounts of fatty acids and lysophosphatides in extracts of cellular lipids. Thereafter, free fatty acids were produced in excess. This suggests that lysophospholipase was active at the later time. We also observed a stoichiometric relation between loss of phosphatidylglycerol and increase of cardiolipin plus lysocardiolipins. This continued well past the normal lysis time (25 min). The appearance of lipase activities during the latent period seems to be specific to infection with rII mutants. Neither the wild-type bacteriophage nor rI mutants produced similar activities by 22 min after infection.

Acetates↗
PubMed1994

Phosphorylation of elongation factor G and ribosomal protein S6 in bacteriophage T7-infected Escherichia coli.

Bacteriophage T7 expresses a serine/threonine-specific protein kinase activity during infection of its host, Escherichia coli. The protein kinase (gp0.7 PK), encoded by the T7 early gene 0.7, enhances phage reproduction under sub-optimal growth conditions. It was previously shown that ribosomal protein S1 and translation initiation factors IF1, IF2, and IF3 are phosphorylated in T7-infected cells, and it was suggested that phosphorylation of these proteins may serve to stimulate translation of the phage late mRNAs. Using high-resolution two-dimensional gel electrophoresis and specific immunoprecipitation, we show that elongation factor G and ribosomal protein S6 are phosphorylated following T7 infection. The gel electrophoretic data moreover indicate that elongation factor P is phosphorylated in T7-infected cells. T7 early and late mRNAs are processed by ribonuclease III, whose activity is stimulated through phosphorylation by gp0.7 PK. Specific overexpression and phosphorylation was used to locate the RNase III polypeptide in the standard two-dimensional gel pattern, and to confirm that serine is the phosphate-accepting amino acid. The two-dimensional gels show that the in vivo expression of gp0.7 PK results in the phosphorylation of over 90 proteins, which is a significantly higher number than previous estimates. The protein kinase activities of the T7-related phages T3 and BA14 produce essentially the same pattern of phosphorylated proteins as that of T7. Finally, several experimental variables are analysed which influence the production and pattern of phosphorylated proteins in both uninfected and T7-infected cells.

Amino Acids↗
PubMed1969

Amino acid regulation of messenger ribonucleic acid synthesis in T4-infected Escherichia coli.

The effect of amino acid starvation on the synthesis of T4 messenger ribonucleic acid (mRNA) was studied by measuring the uptake of labeled precursors into Escherichia coli cells which were infected prior to amino acid starvation. The results indicated that the rate of uptake of labeled uracil and adenine into T4 mRNA was reduced by approximately 50% when amino acids were withheld from stringent K-12 strains, but not when they were withheld from a stringent strain B or a relaxed strain K-12. Chloramphenicol reversed the inhibition of precursor uptake resulting from amino acid starvation in the RC(str) K-12 strain. Pulse-labeling experiments reinforced these observations. Pulse-decay experiments in conjunction with actinomycin D indicated that the observed pattern of precursor uptake was probably not due to differences in mRNA decay rate. It is concluded that if amino acids exert any direct effect on the synthesis of T4 mRNA such an effect is much smaller than that observed for bulk RNA synthesis in the uninfected cell. These experiments also indicated that actual translation of the genetic message is not necessary for its transcription.

Adenine↗
PubMed1979

A DNA-unwinding enzyme induced in bacteriophage-T4-infected Escherichia coli cells.

A single-stranded DNA-dependent ATP gamma-phosphohydrolase of Mr 56000 induced after infection of Escherichia coli cells with bacteriophage T4, probably the ATPase dependent on gene dda of the phage, was isolated. Studies on the enzyme show that in the presence of ATP and M2+ ions it is capable of dissociating partially double-stranded fd bacteriophage DNA into the single strands and that some 3000 enzyme copies are required to unwind the 6400-nucleotides-long DNA. Unwinding is inhibited by reducing the length of the single-stranded portion of DNA to two nucleotides. In addition it can be inhibited by sulfhydryl reagents which block the ATPase or by trapping free enzyme molecules in the assay system. The results suggest that unwinding is initiated near the single-stranded portion of the DNA and is driven by the ATPase. It further appears that the enzyme unwinds by adsorbing to the DNA. Affinity of the enzyme for double-standed DNA is not detectable by DNA binding assay.

Adenosine Triphosphatases↗
PubMed1969

Selective translation of T4 template RNA by ribosomes from T4-infected Escherichia coli.

The present studies indicate that T4 infection induces an alteration in host ribosomes which restricts the translation of host and other T4-unrelated template RNAs but permits normal translation of T4 RNA. A heat-labile factor has been isolated from T4-infected cell ribosomes which, when combined with normal cell ribosomes, confers upon the latter the property of selective T4 template RNA translation.

Coliphages↗