Generation of a stable, aminotyrosyl radical-induced α2β2 complex of Escherichia coli class Ia ribonucleotide reductase

Proc Natl Acad Sci U S A. 2013 Mar 5;110(10):3835-40. doi: 10.1073/pnas.1220691110. Epub 2013 Feb 19.


Ribonucleotide reductase (RNR) catalyzes the conversion of nucleoside diphosphates to deoxynucleoside diphosphates (dNDPs). The Escherichia coli class Ia RNR uses a mechanism of radical propagation by which a cysteine in the active site of the RNR large (α2) subunit is transiently oxidized by a stable tyrosyl radical (Y•) in the RNR small (β2) subunit over a 35-Å pathway of redox-active amino acids: Y122• ↔ [W48?] ↔ Y356 in β2 to Y731 ↔ Y730 ↔ C439 in α2. When 3-aminotyrosine (NH2Y) is incorporated in place of Y730, a long-lived NH2Y730• is generated in α2 in the presence of wild-type (wt)-β2, substrate, and effector. This radical intermediate is chemically and kinetically competent to generate dNDPs. Herein, evidence is presented that NH2Y730• induces formation of a kinetically stable α2β2 complex. Under conditions that generate NH2Y730•, binding between Y730NH2Y-α2 and wt-β2 is 25-fold tighter (Kd = 7 nM) than for wt-α2

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Catalytic Domain
  • Electron Transport
  • Enzyme Stability
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Kinetics
  • Microscopy, Electron
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Protein Structure, Quaternary
  • Protein Subunits
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ribonucleotide Reductases / chemistry*
  • Ribonucleotide Reductases / classification
  • Ribonucleotide Reductases / genetics
  • Ribonucleotide Reductases / metabolism*
  • Scattering, Small Angle
  • Spectrometry, Fluorescence
  • X-Ray Diffraction


  • Escherichia coli Proteins
  • Protein Subunits
  • Recombinant Proteins
  • Ribonucleotide Reductases