Tyrosyl free radical formation in the small subunit of mouse ribonucleotide reductase.

Ochiai, E; Mann, Graham J.; Gräslund, Astrid; Thelander, Lars

doi:10.1016/s0021-9258(18)55462-4

Cited by 83 publications

(66 citation statements)

References 17 publications

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“…These reactants can deplete NO and restore RIL (40,41). The major catalytic components of ILK are ferric ions coupled through/~-oxo bridges, tyrosyl radicals, and reduced thiols (17)(18)(19)(20)22). Each is a possible site for NO-mediated inactivation.…”

Section: Discussionmentioning

confidence: 99%

“…Ribonucleotide reductase (RR), a rate-limiting 1 Abbreviations used in this paper: FAD, flavin adenine dinucleotide; GC/MS, gas chromotography/mass spectrometry; re~z, mass-to -charge ratio; NO, nitric oxide; RR, ribonucleotide reductase. 761 enzyme in DNA synthesis, depends on thiols (17,18) and on non-heine iron in its reaction center (17,19), which are crucial for maintaining a key tyrosyl radical (20). Thus, RR is a candidate for inactivation by NO, and inactivation of RR might explain the cytostatic effect of NO-producing macrophages (8,12).…”

mentioning

confidence: 99%

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Inhibition of tumor cell ribonucleotide reductase by macrophage-derived nitric oxide.

Kwon

Stuehr

Nathan

1991

The Journal of Experimental Medicine

407

154

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SummaryMacrophage-derived nitric oxide (NO) is cytostatic to tumor cells and microbial pathogens. We tested whether one molecular target for the cytostatic action of NO may be ribonucleotide reductase (RR), a rate-limiting enzyme in DNA synthesis. In a concentration-dependent manner, NO gas and lysates of activated macrophages that generated comparable amounts of NO led to the same degree of inhibition of partially purified RR from L1210 mouse lymphoma cells. Lysates from nonactivated macrophages, which do not produce NO, were noninhibitory. With lysates from activated macrophages, RR was protected by omitting t-arginine or by adding the NO synthase inhibitors diphenyleneiodonium, N'~-methyl+arginine, or N'~-amino+arginine. t-Arginine, but not D-arginine, abolished the protective effect of N'~ The prototypic pharmacologic inhibitor of IkR is hydroxyurea. Its structural resemblance to N '~-hydroxy-t-arginine, a reaction intermediate of NO synthase, prompted us to test if hydroxyurea can generate NO. In the presence of H202 and CuSO4, hydroxyurea produced NO2-/NO3-, aerobic reaction products of NO. Addition of morpholine blocked NO2-/NO3-generation from hydroxyurea and led to formation of nitrosomorpholine, as detected by gas chromatography/mass spectrometry. Thus, hydroxyurea can produce an NO-like, nitrosating reactant. L1210 cell DNA synthesis was inhibited completely by activated macrophages or by hydroxyurea, and was partially restored to the same degree in both settings by providing deoxyribonucleosides to bypass the block in RR. Thus, both NO gas and NO generated by activated macrophage lysates inhibit tumor cell RR. The RR inhibitor hydroxyurea can also generate an NO-like species. Similar, partial restoration of tumor cell DNA synthesis by deoxyribonucleosides in the presence of activated macrophages or hydroxyurea suggests that cytostasis by activated macrophages and by hydroxyurea has comparable mechanisms, including, but probably not limited to, inhibition of RR.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Inhibition of tumor cell ribonucleotide reductase by macrophage-derived nitric oxide.

Kwon

Stuehr

Nathan

1991

The Journal of Experimental Medicine

407

154

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“…There have been many recent studies on the formation of the diferric center and tyrosyl radical. ,,− The R2 activation reaction can be formally written as The second atom of oxygen from O 2 is also reduced to the level of water, but resonance Raman experiments have shown that it is incorporated into the binuclear iron cluster as the bridging oxygen …”

Section: R2 Activation and Intermediates Involved In This Process1 De...mentioning

confidence: 99%

“…Four electrons are required to reduce O 2 to two waters; three of which derive from oxidation of the 2Fe(II) and the formation of the oxidized tyrosyl radical. It is known that in vitro , the fourth reducing equivalent can be donated from a chemical reductant such as ascorbate, an additional Fe(II) ion, or even the reduced binuclear iron site in the neighboring protomer. ,, The ability to activate the R2 protein in vitro by chemical methods has allowed some elegant experiments that focused on the intermediates in the R2 activation reaction. As they were originally formulated, these experiments involved rapidly mixing R2 apo with Fe(II) and O 2 .…”

Section: R2 Activation and Intermediates Involved In This Process1 De...mentioning

confidence: 99%

Dioxygen Activation by Enzymes Containing Binuclear Non-Heme Iron Clusters

1996

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“…To reduce fully molecular oxygen, four electrons are needed. In the radical generation reaction one of these electrons comes from each of the two ferrous ions, another from Tyr122 and the fourth is provided from another source, which in vivo is most likely Fe 2+ [15,16].…”

Section: Introductionmentioning

confidence: 99%

Crystal structure of reduced protein R2 of ribonucleotide reductase: the structural basis for oxygen activation at a dinuclear iron site

et al. 1996

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Carboxylate shifts are often important for carboxylate coordinated metal clusters; they allow the metals to achieve different coordination modes in redox reactions. In the case of reduced R2 these carboxylate shifts allow the formation of accessible reaction sites for dioxygen. The Ser211--> Ala mutant displays a conformational change in the helix containing the mutation, explaining its altered reduction kinetics.

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Tyrosyl free radical formation in the small subunit of mouse ribonucleotide reductase.

Cited by 83 publications

References 17 publications

Inhibition of tumor cell ribonucleotide reductase by macrophage-derived nitric oxide.

Inhibition of tumor cell ribonucleotide reductase by macrophage-derived nitric oxide.

Dioxygen Activation by Enzymes Containing Binuclear Non-Heme Iron Clusters

Crystal structure of reduced protein R2 of ribonucleotide reductase: the structural basis for oxygen activation at a dinuclear iron site

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