Mutants Constitutive for Nucleoside-Catabolizing Enzymes in Escherichia coli K 12. Isolation, Characterization and Mapping

Munch‐Petersen, Agnete; Nygaard, Per; Hammer-Jespersen, Karin; Fill, N P

doi:10.1111/j.1432-1033.1972.tb01828.x

Cited by 72 publications

(33 citation statements)

References 22 publications

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“…1A (Fig. 2B). [The biosynthesis of the transport system is strongly repressed by glucose through the cytR control system (7). For this reason, the cells used for transport studies were grown in medium containing glycerol as carbon source.…”

Section: Resultsmentioning

confidence: 99%

“…These are the cytR and deoR genes, which regulate the synthesis of the nucleoside-catabolizing enzymes (6,7). The nupC system is regulated by the cytR gene, whereas the nupG system responds to both regulatory genes (4).…”

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confidence: 99%

“…Strains with a deletion in the deo operon and with a mutation in the cytR gene were constructed by mating this strain with So 818 (Hfr Cavalli, Adeo, cytR), selecting for Met+. The cytR gene controls the synthesis of the nucleoside-transport systems (and of the nucleoside-catabolizing enzymes) (4,7), and the mutation was introduced in order to ensure efficient transport in the mutants. It cotransduces 80-90% with metB (7).…”

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confidence: 99%

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Stimulatory effect of low ATP pools on transport of purine nucleosides in cells of Escherichia coli.

Munch‐Petersen¹,

Pihl²

1980

Proc. Natl. Acad. Sci. U.S.A.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Stimulatory effect of low ATP pools on transport of purine nucleosides in cells of Escherichia coli.

Munch‐Petersen¹,

Pihl²

1980

Proc. Natl. Acad. Sci. U.S.A.

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“…Although regulatory mutants, deoR and deo-lac fusions 243 cytR, have been isolated (Ahmad & Pritchard, 197 1 ;Munch-Petersen et al, 1972), only one deo operator constitutive mutant has been obtained (Ahmad & Pritchard, 1973). Unfortunately, because of the method of selection employed, the strain also acquired a deoB mutation.…”

Section: R S B U X T O Nmentioning

confidence: 99%

Fusion of the lac Genes to the Proximal Promoters of the deo Operon of Escherichia coli K12

Buxton

1979

Journal of General Microbiology

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241Fusions of the ldC structural genes to the proximal promoters deoP and cytP of the deo operon have been isolated using a h (lac, Mu') phage. This phage was inserted into a heatinducible Mu prophage which had itself been inserted into the deoA gene. Selection was made for heat-resistant derivatives of this lysogen which maximally expressed the lac genes when an inducer of the deo operon was present; these were shown to have the lac genes fused to the deo operon-in some cases with a concomitant deletion of the deoC gene, whilst in others deoC was retained. The level of P-galactosidase activity in these strains was induced by growth in the presence of deoxyadenosine or cytidine, both of which lead to induction of the deo enzymes -deoxyadenosine through the deoOP system and cytidine through the cytOP system. The level of induction of P-galactosidase was of the same order as the level of induction of deoxyriboaldolase, the deoC gene product, in those strains retaining an intact deoC+ gene. Plaque-forming h phages carrying the deo-lac fusions were isolated by inducing the lysogens with mitomycin C.

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“…Genes coding for: thymidylate synthetase, thy; deoxyriboaldolase, dra; phosphodeoxyribomutase, drm; purine nucleoside phosphorylase, p u p ; thymidine phosphorylase, t p p ; regulatory gene for dra, drm, tpp and pup, deoR [12].…”

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confidence: 99%

Thymine Utilization in Escherichia coli K12 on the Role of Deoxyribose 1‐Phosphate and Thymidine Phosphorylase

Jensen¹,

Leer²,

Nygaard³

1973

European Journal of Biochemistry

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Exogenously supplied thymine is only poorly utilized by wild-type cells of Escherichia coli for the synthesis of their DNA. It appears that the lack of incorporation of exogenous thymine is due to a lack of endogenous deoxyribosyl groups, which are required for the synthesis of thymidine.Data to be presented in this paper indicate that the ability of different thymine auxotrophs to grow on progressively lower thymine concentrations is a function of their capacity to increase the internal pool of deoxyribose 1 -phosphate and/or the level of thymidine phosphorylase.Thymine incorporation in wild-type cells could be observed if the cells possessed an increased deoxyribose 1 -phosphate pool.The kinetics of thymine uptake in wild-type cells, in a mutant lacking thymidine phosphorylase and in thymine auxotrophs show that the initial rates of thymine uptake are almost identical and proportional to the external thymine concentration.The experiments in vivo led us to conclude that the incorporation of exogenous thymine occurs via thymidine, which is synthesized from thymine and deoxyribose 1-phosphate, catalyzed by thymidine phosphorylase. I n accordance with this studies in vitro with purified thymidine phosphorylase showed that thymidine is synthesized from deoxyribose I-phosphate and thymine rather than through a deoxyribose transfer from a deoxynucleoside.Wild-type cells of Escherichia coli do not readily utilize exogenous thymine for the synthesis of their DNA. I n contrast, thymidine is incorporated, but the incorporation soon terminates due t o a rapid degradation of the added thymidine [l --51. Experiments with EDTA-treated cells revealed that the limited utilization of exogenous thymine cannot be ascribed solely to permeability restrictions [4,5] but is, rather, related to the availability of deoxyribosyl donors [6,7]. Thus, when deoxyribonucleosides are added to the medium, exogenous thymine is readily taken up and utilized for DNA synthesis [3-51.Abbreviations. Genes coding for: thymidylate synthetase, thy; deoxyriboaldolase, dra; phosphodeoxyribomutase, drm; purine nucleoside phosphorylase, p u p ; thymidine phosphorylase, t p p ; regulatory gene for dra, drm, tpp and pup, deoR [12].Enzymes. Deoxyriboaldolase or 2-deoxy-D-ribose-5-phosphate : acetaldehyde-lyase (EC 4.1.2.4) ; thymidine phosphorylase or thymidine : orthophosphate deoxyribosyltransferase (EC 2.4.2.4) ; purine(deoxy)ribonucleoside phosphorylase, purine-nucleoside : orthophosphate(deoxy)ribosyltransferase (EC 2.4.2.1); thymidylate synthetase or methylenetetrahydrofolate : dUMP (methyltransferase) (EC 2.1.1.); thymidine lrinase or ATP : thymidine-5'-phosphotransferase (EC 2.7.1.21).The existence of thymine-requiring mutant strains shows that exogenous thymine can be used for dTMP synthesis and that the internal deoxyribosyl groups are furnished from an increased catabolism of deoxyribonucleotides [6-S]. Thymine-requiring mutants isolated by the aminopterin procedure [7,9] require high concentrations (160-400 pM) of exogenous thymine for growth. Fro...

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Mutants Constitutive for Nucleoside-Catabolizing Enzymes in Escherichia coli K 12. Isolation, Characterization and Mapping

Cited by 72 publications

References 22 publications

Stimulatory effect of low ATP pools on transport of purine nucleosides in cells of Escherichia coli.

Stimulatory effect of low ATP pools on transport of purine nucleosides in cells of Escherichia coli.

Fusion of the lac Genes to the Proximal Promoters of the deo Operon of Escherichia coli K12

Thymine Utilization in Escherichia coli K12 on the Role of Deoxyribose 1‐Phosphate and Thymidine Phosphorylase

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