Ribonucleic Acid Synthesis in Bacteria Treated with Toluene

Escherichia coli and Bacillus megaterium rendered permeable to ribonucleoside triphosphates by toluene treatment retain the capacity to synthesize discrete ribonucleic acid species.     

Complementary Functioning of Nitrogenase Components from a Blue-Green Alga and a Photosynthetic Bacterium

Nitrogenases from Anabaena cylindrica and Chloropseudomonas ethylicum were partially purified into two components. A. cylindrica fraction I protein complemented fraction II protein from C. ethylicum. However, the reciprocal cross between C. ethylicum fraction I and A. cylindrica fraction II was negative.     

Changes in Hepatic Glycogen, Protein, and Ribonucleic Acid Synthesis, and Some Effects of Cortisol, During Q Fever

Liver glycogen is depleted in guinea pigs infected with Coxiella burneti. Syntheses of the glycogen precursors uridine triphosphate and uridine diphosphate glucose are unaffected during Q fever, but glycogen synthetase activity is inhibited. Exogenous cortisol relieves this inhibition in infected animals. Orotate and amino acids are more rapidly incorporated into ribonucleic acid and protein during infection. It is proposed that the biochemical defect in the synthesis of glycogen lies in the inactivation of glycogen synthetase.     

Dark Repair of Ultraviolet-Irradiated Deoxyribonucleic Acid by Bacteriophage T4: Purification and Characterization of a Dimer-Specific Phage-Induced Endonuclease

The purification and properties of an ultraviolet (UV) repair endonuclease are described. The enzyme is induced by infection of cells of Escherichia coli with phage T4 and is missing from extracts of cells infected with the UV-sensitive and excision-defective mutant T4V(1). The enzyme attacks UV-irradiated deoxyribonucleic acid (DNA) containing either hydroxymethylcytosine or cytosine, but does not affect native DNA. The specific substrate in UV-irradiated DNA appears to be pyrimidine dimer sites. The purified enzyme alone does not excise pyrimidine dimers from UV-irradiated DNA. However, dimer excision does occur in the presence of the purified endonuclease plus crude extract of cells infected with the mutant T4V(1).     

Fluorouracil and the isolation of mutants lacking uridine phosphorylase in Escherichia coli: location of the gene

Summary A selective technique is described for the isolation of mutants of Escherichia coli lacking uridine phosphorylase and the location of the gene specifying this enzyme on the bacterial chromosome is determined. Using strains with appropriate lesions it is shown that there are three routes via which 5-fluorouracil can be converted to compounds which inhibit cell growth.     

A genetic and biochemical study of streptomycin- and spectinomycin-resistance in Salmonella typhimurium

Summary In Salmonella typhimurium, streptomycin resistance can occur by mutation at the strA or the strB mutants have altered ribosomes which are refractory to the drug in cell-free amino acid incorporation systems, and in ³H-dihydrostreptomycin binding studies. StrB mutants, unlike the strA mutants, are resistant to several aminoglycoside antibiotics and resistance is not due to a mutational change in the cell's protein synthetic machinery. Spectinomycin resistant mutants of S. typhimurium also fall into two classes, only one of which is ribosomal in mechanism. The spcA and spcB loci are closely linked to strA, aroC, and argG on the S. typhimurium linkage map.     

The in vitro synthesis and characteristics of ribosomal RNA in imaginal discs of Drosophila melanogaster

Summary Late third instar imaginal discs of Drosophila melanogaster cultured in vitro in Robb's tissue culture medium synthesize 38S, 28S and 18S ribosomal RNAs which are qualitatively indistinguishable from their in vivo synthesized counterparts (Fig. 1). As found in other insect systems, the 38S molecule appears to be the precursor for both the 28S and 18S rRNAs (Figs. 2, 3 and 4). The 28S rRNA and a portion of the 38S pre-rRNA shift in sedimentation value upon exposure to heat or dimethylsulfoxide (Figs. 5 and 8). Studies of the thermal denaturations of these molecules (Figs. 6, 7 and 9) indicate the existence of a single class of 28S rRNA, but three classes of 38S pre-rRNAs. The addition of -ecdysone to the in vitro culture medium stimulates the net amount of rRNA synthesized, increases the rate of processing of the 38S precursor and increases the relative amount of 18S material produced (Figs. 10 and 12).This work was supported in part by grants from the National Science Foundation (GB-8176) and from the Atomic Energy Commission (AT-04-3-34).Predoctoral Trainees, PHS Training Grant No. 2-Tl-GM367 from Research Training Grants Branch, National Institute of General Medical Sciences.1 For purposes of simplification we shall refer to the rRNA molecules of D. melanogaster as being 38S, 30S, 28S and 18S; however, it should be noted that these values are approximate (see Hastings and Kirby, 1966; Greenberg, 1969; Tartof and Perry, 1970).     

Metabolic studies on retinoic acid in the rat

The nature of metabolites in the urine arising from differentially labelled retinoic acid was investigated after injection of physiological doses into retinol-deficient rats. Distribution of radioactivity after partition of urine into ether-soluble, acidic and water-soluble fractions revealed that there were at least six metabolites in urine. Of these, the major metabolite(s) was one lacking both C-14 and C-15 of retinoic acid. Enzymic or alkaline hydrolysis of acidic and water-soluble fractions did not release any retinoic acid, thus indicating that retinoyl beta-glucuronide was not present in urine in significant amounts.     

Protein-bound phosphorylserine in acid hydrolysates of brain tissue. The determination of [32P]phosphorylserine by ion-exchange chromatography and electrophoresis

1. Partial acid hydrolysates of proteins derived from cortical slices of guinea-pig brain were divided into two parts and fractionated by ion-exchange chromatography and high-voltage electrophoresis. 2. The apparent yield of protein-bound phosphorylserine by the ion-exchange method was about three times that obtained by electrophoresis. 3. The specific radioactivity of phosphorylserine isolated from (32)P-labelled slices by electrophoresis was twice that isolated by chromatography. 4. The discrepancies were found to be due to the presence of unlabelled phosphates of unknown composition in the ;phosphorylserine' fraction obtained by the ion-exchange method. 5. Electrical stimulation of slices respiring in the presence of [(32)P]phosphate increased the specific radioactivity of the total phosphate in the chromatographic ;phosphorylserine' fraction by 53+/-11%, as compared with only 19+/-5% for the phosphorylserine isolated by electrophoresis.