2-Deoxyribose Gene-Enzyme Complex in
            <i>Salmonella typhimurium</i>
            : Regulation of Phosphodeoxyribomutase

A mutant of Salmonella typhimurium with a defect in the regulation of pyr-gene expression was obtained during a selection for mutants resistant to a combination of the two pyrimidine analogs, 5-fluorouracil and 5-fluorouridine. The mutant possesses 4-fold elevated pools of the pyrnmidine nucleoside triphosphates, UTP and CTP. The specific activities of aspartate transcarbamylase and orotate phosphoribosyltransferase are 40-fold and 7-fold higher in the mutant than in the parent strain when grown in minimal media. Fur#iennore, the synthesis of the two enzymes in the mutant is not repressed following addition of exogenous pyrimidines. The levels of carbamoylphosphate synthase and orotidine 5' -monophosphate decarboxylase are O3-fold enhanced, while the activities of dihydroorotase and dihydroorotate oxidase appear largely unaffected by the mutation. The mutation responsible for these effects was shown to map between two known point mutations in the rpoBC gene cluster encoding the (3 and ,B' subunits of RNA polymerase. These observations indicate a regulatory function of RNA polymerase in the control ofpyr-gene expression in S. typhimurium.

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“…Tetracycline resistance was selected and uracil auxotrophs were picked. (Hoffee and Robertson, 1969).…”

Section: Levels Ofpyrimidine Nucleotide Biosynthetic Enzymes In Wildtmentioning

confidence: 99%

RNA polymerase involvement in the regulation of expression of Salmonella typhimurium pyr genes. Isolation and characterization of a fluorouracil-resistant mutant with high, constitutive expression of the pyrB and pyrE genes due to a mutation in rpoBC.

Jensen¹,

Neuhard²,

Schack³

1982

The EMBO Journal

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“…With the information available from the reports of Kammen (13) and of Hoffee and Robertson (11), EDTA, manganous ions, ME, and HDP were added to ultrasonic extracts containing dRiP. The three supplements together allowed a very substantial rate of disappearance of dRlP as illustrated by Fig.…”

Section: Downloaded Frommentioning

confidence: 98%

“…The addition of 1O3 M Mn2+ stimulated the activity to a variable degree from culture to culture obtained under the same conditions of growth. For more reproducible results, it was decided to include EDTA (11), which revealed the absolute requirement for Mn2+ in every experiment. C) 10 Vn Protein, %% FK;.…”

Section: Downloaded Frommentioning

confidence: 99%

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Regulation of Thymidine Metabolism in Escherichia coli K-12: Optimal Conditions for the Assay of 1,5-Phosphodeoxyribomutase in Ultrasonic Extracts

Bonney

Weinfeld

1970

J Bacteriol

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Assay conditions have been established which allow maximum expression of phosphodeoxyribomutase activity in ultrasonic extracts of Escherichia coli K-12. The enzyme requires 2-mercaptoethanol, manganous ions, and glucose 1,6-diphosphate for optimal activity. When cells are grown in minimal medium with glycerol as the carbon source and supplemented with 10 −3 m thymidine, phosphodeoxyribomutase is induced three- to four-fold. Cell pellets may be frozen for 24 hr before sonic disruption without loss of enzyme activity. The assay is highly reproducible.

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“…for determination of nucleoside monophosphates. The numbers designate the following compounds: (1) dUMP, (2) dTMP, (3) dRib-5-P, (4) UMP, (5) AMP, (6) dAMP, (7) CMP, (8) dCMP…”

Section: Thin-layer Chromatographymentioning

confidence: 99%

Deoxyribonucleoside Catabolism and Thymine Incorporation in Mutants of Escherichia coli Lacking Deoxyriboaldolase

Munch‐Petersen¹

1970

Eur J Biochem

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Mutants of E'scherichia coli lacking the enzyme deoxyriboaldolase cannot catabolize the deoxyribose moiety of deoxyribonucleosides. When deoxyribonucleosides are added to the growth medium a severe growth inhibition is observed under aerobic as well as anaerobic conditions. The toxic substance is presumably deoxyribose-5-phosphate, which is shown t o accumulate in the cells. Normal growth is restored when this compound is broken down or if a ribonucleoside is added simultaneously t o the medium.dra-Mutants arise spontaneously as secondary mutants from cultures of thymine-requiring mutants, isolated by means of the trimethoprim selection procedure.dra-Mutants may also be obtained by mutagenization, penicillin treatment, and selection on thymidine as carbon source. Mutants, isolated in this way, have an additional mutation in the deoxyribonucleoside catabolizing system, which has been identified as an altered thymidine phosphorylase.A number of different thy-and dra-strains have been screened for incorporation of exogenous thymine in relation to pyrimidine deoxyribonucleotide pools. Low pools of dTTP and high pools of dUMP are found in all thymine incorporating mutants. It is concluded that incorporation depends primarily on the cellular pools of thymine nucleotides, which by regulatory mechanisms determine the availability of deoxyribosyl donors for thymidine synthesis. Catabolism of deoxyribonucleosides in Esckrichia cola' occurs through the following reactions :Purine deoxyribonucleoside purine basePyrimidine deoxyribonucleoside pyrimidine base dRib-1-P + Or'+ pi purine nueleoside phosphorylasethymidine phosphorylaseIf deoxyribonucleosides are added to the growth medium, the enzymes catalyzing these reactions are induced several-fold [l-61, and the deoxyribose moiety of the added deoxyribonucleoside is rapidly metabolized. One of the intermediates in the metabolic sequence, dRib-5-P, is supposed to be the inducer If the cells lack deoxyriboaldolase, for which dRib-5-P is the substrate, addition of deoxyribonucleosides causes inhibition of growth. dRib-5-P has been suggested [6,8,9] as the actual inhibitor, and this is supported by the results presented in this paper where the inhibitory effect and its consequences for cell metabolism have been studied more closely.Thymine auxotrophy is another metabolic condition in which the metabolism of deoxyribonucleosides becomes important. Since auxotrophic cells have lost the methylating systems which normally lead to the formation of dTTP, thymine for DNA-synthesis must be supplied from the outside. The initial reaction in the sequence of processes that lead to thymine incorporation into DNA (see Fig.1 Fig.l), and the methylation and deamination of dCTP to dTTP as reported by Holldorf and coworkers [1l,i2] (Reaction 2 in Fig.1 I n thymine auxotrophs the loss of these pathways necessitates a channeling of the flow of deoxyribosyl groups required for synthesis of dTTP through deoxyribonucleosides and deoxyribose-1-phosphate for synthesis of thymidine from exogenous thymin...

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2-Deoxyribose Gene-Enzyme Complex in Salmonella typhimurium : Regulation of Phosphodeoxyribomutase

Cited by 43 publications

References 16 publications

RNA polymerase involvement in the regulation of expression of Salmonella typhimurium pyr genes. Isolation and characterization of a fluorouracil-resistant mutant with high, constitutive expression of the pyrB and pyrE genes due to a mutation in rpoBC.

RNA polymerase involvement in the regulation of expression of Salmonella typhimurium pyr genes. Isolation and characterization of a fluorouracil-resistant mutant with high, constitutive expression of the pyrB and pyrE genes due to a mutation in rpoBC.

Regulation of Thymidine Metabolism in Escherichia coli K-12: Optimal Conditions for the Assay of 1,5-Phosphodeoxyribomutase in Ultrasonic Extracts

Deoxyribonucleoside Catabolism and Thymine Incorporation in Mutants of Escherichia coli Lacking Deoxyriboaldolase

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