Effect of the tyrosyl radical on the reduction and structure of the Escherichia coli ribonucleotide reductase protein R2 diferric site as probed by EPR on the mixed-valent state

Biochemistry
R DavydovA Ehrenberg

Abstract

It was recently shown by EPR that high yields of a sterically constrained mixed-valent species may be formed in radical free protein metR2 of Escherichia coli ribonucleotide reductase by gamma-irradiation at 77 K [Davydov, R., Kuprin, S., Gräslund, A., & Ehrenberg, A. (1994) J. Am. Chem. Soc. 116, 11120]. This species, with S = 1/2, essentially retains the ligand geometry of the original diferric center and should be a sensitive probe for structural changes in the diferric centers. Here we apply this probe and demonstrate that there is a structural difference between the diferric iron center of the complete site of protein R2, with a tyrosyl radical, and that of metR2, without radical. The EPR spectrum of the mixed-valent species of metR2 shows pure axial symmetry, while complete sites show rhombic distortion and a shifted high-field turning point. Differences also remain in the EPR of the first S = 9/2 species obtained by annealing at 165 K, but disappear after relaxation at 200 K. In addition, the diferric center of a complete site is not reduced radiolytically until the associated tyrosyl radical has been reduced, indicating that an electron first reaching the iron center may be transferred to the radical. This route of elec...Continue Reading

References

Jul 5, 1993·Journal of Molecular Biology·P Nordlund, H Eklund

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Citations

Apr 19, 2013·Journal of the American Chemical Society·Adam R OffenbacherBridgette A Barry
Sep 6, 2002·Insect Biochemistry and Molecular Biology·D Q D PhamJ J Winzerling
Apr 12, 2000·European Journal of Biochemistry·D E CoufalS J Lippard
May 26, 2004·Biochimica Et Biophysica Acta·Matthias KolbergK Kristoffer Andersson
Feb 13, 2003·Journal of Molecular Biology·Pramod P WangikarSunita Sarawagi
Feb 18, 2004·The Journal of Biological Chemistry·Theodora ZlatevaMarian T Stankovich
Jun 21, 2001·Journal of the American Chemical Society·J TelserB M Hoffman
Nov 7, 1996·Chemical Reviews·Bradley J. Wallar, John D. Lipscomb

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