EPR stopped-flow studies of the reaction of the tyrosyl radical of protein R2 from ribonucleotide reductase with hydroxyurea

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Item Type:	Article
Title:	EPR stopped-flow studies of the reaction of the tyrosyl radical of protein R2 from ribonucleotide reductase with hydroxyurea
Creators Name:	Lassmann, G., Thelander, L. and Graeslund, A.
Abstract:	The reaction of the functional tyrosyl radical in protein R2 of ribonucleotide reductase from E. coli and mouse with the enzyme inhibitor hydroxyurea has been studied by EPR stopped-flow techniques at room temperature. The rate of disappearance of the tyrosyl radical in E. coli protein R2 is k2 = 0.43 M-1 s-1 at 25 degrees C. The reaction follows pseudo-first-order kinetics up to 450 mM hydroxyurea indicating that no saturation by hydroxyurea takes place even at this high concentration. Transient nitroxide-like radicals from hydroxyurea have been detected for the first time in the reaction of hydroxyurea with protein R2 from E. coli and mouse, indicating that 1-electron transfer from hydroxyurea to the tyrosyl radical is the dominating mechanism in the inhibitor reaction. The hydroxyurea radicals appear in low steady-state concentrations during 2-3 half-decay times of the tyrosyl radical and disappear thereafter.
Keywords:	Electron Spin Resonance Spectroscopy, Escherichia Coli, Free Radicals, Hydroxyurea, Kinetics, Macromolecular Substances, Oxidation-Reduction, Ribonucleotide Reductases, Animals, Mice
Source:	Biochemical and Biophysical Research Communications
ISSN:	0006-291X
Publisher:	Academic Press
Volume:	188
Number:	2
Page Range:	879-887
Date:	30 October 1992
Official Publication:	https://doi.org/10.1016/0006-291X(92)91138-G
PubMed:	View item in PubMed

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