In all organisms the deoxyribonucleotide precursors required for DNA synthesis are synthesized from ribonucleotides, a reaction catalyzed by ribonucleotide reductase. In a previous study we showed that Chlamydia trachomatis growth was inhibited by hydroxyurea, an inhibitor of ribonucleotide reductase, and a mutant resistant to the cytotoxic effects of the drug was isolated. Here we report the c...

An iron-sensitive mutant of E. coli with a Mudl phage insertion in the nrdB gene lacks subunit B2 of the key enzyme of DNA synthesis, ribonucleotide reductase. Nevertheless, these cells are capable of growing in minimal media under anaerobic conditions, indicating a second enzyme or pathway for deoxyribonucleotide synthesis. We here show that ribonucleotide reduction cannot be unambiguously mea...

Ribonucleotide reductase is an essential enzyme in mammalian DNA replication. In quiescent BHK-21/C13 cells exhibiting a low level of ribonucleotide reductase activity, infection with herpes simplex virus (HSV) resulted in the early induction of an altered ribonucleotide reductase. The extent of the induction was dependent upon the m.o.i. and could be diminished or prevented by u.v. treatment o...

When highly purified cobamide-dependent ribonucleotide reductase from Lacfobacillus leichmannii is incubated with synthetically prepared 5,6-dimethylbenzimidazolylcobamide 5’-deoxyadenosyl coenzyme containing tritium attached to carbon atom 5’ of the deoxyadenosyl moiety (DBCC-5’-3H), tritium is transferred from DBCC-5’-3H to Hz0 in a reaction requiring substrate, enzyme, and dithiol reductant....

Incubation of the pyrimidine [3'-3H]UDP with ribonucleotide reductase resulted in an isotope effect on the conversion to dUDP which varied as a function of pH and allosteric effectors (pH, kH/kT, effector): 6.6, 4.7, ATP; 7.6, 3.3, ATP; 7.6, 2.6, dATP; 7.6, 2.0, TTP; 8.4, 2.8, ATP. During this reaction 3H2O was also released. The lower the pH of the reaction, the larger the isotope effect, and ...

Ribonucleoside-diphosphate reductase (ribonucleotide reductase, EC 1.17.4.1) is the enzyme responsible for the in vivo production of deoxyribonucleotides for DNA synthesis and is essential for cell proliferation. We examined the signal transduction pathways leading to expression of the M1 and M2 subunits of this enzyme in Swiss 3T3 mouse fibroblasts by Northern blot analysis. Stimulation of qui...

Bleomycin is a commonly used chemotherapeutic agent known to cause extensive DNA damage. In this paper we show that bleomycin inhibits ribonucleotide reductase activity in mouse L-cells. The effectiveness of the drug is a result of its metal-chelating properties which enable it to inactivate the iron containing M2 subunit of the enzyme. A hydroxyurea-resistant mouse L-cell line was used to show...

In this study herpes simplex virus type 1-encoded ribonucleotide reductase was shown to be able to utilize thioredoxin purified from the cyanobacterium Anabaena variabilis as a hydrogen donor for the enzyme. An assay has been developed to search for proteins which can function as a hydrogen donor for the viral ribonucleotide reductase. A protein has been identified and purified to homogeneity f...

Clam oocytes display a striking difference in the pattern of protein synthesis on fertilization, which is maintained when cell-free extracts are assayed in the rabbit reticulocyte lysate. The mRNAs encoding ribonucleotide reductase and cyclin A (the major masked messages in the oocyte extracts) can be translationally activated by gel filtration in 0.5 M KCl, presumably by removal of repressor p...