Pulsed ELDOR Spectroscopy Measures the Distance between the Two Tyrosyl Radicals in the R2 Subunit of the E. coli Ribonucleotide Reductase

Citations Over TimeTop 10% of 2003 papers

Abstract

Escherichia coli ribonucleotide reductase (RNR) catalyzes the conversion of nucleoside diphosphates (NDPs) to deoxynucleoside diphosphates (dNDPs). This RNR is composed of two homodimeric subunits: R1 and R2. R1 binds the NDPs in the active site, and R2 harbors the essential di-iron tyrosyl radical (Y*) cofactor. In this paper, we used PELDOR, a method that detects weak electron-electron dipolar coupling, to make the first direct measurement of the distance between the two Y*'s on each monomer of R2. In the crystal structure of R2, the Y*'s are reduced to tyrosines, and consequently R2 is inactive. In R2, where the Y*'s assume a well-defined geometry with respect to the protein backbone, the PELDOR method allows measurement of a distance of 33.1 +/- 0.2 A that compares favorably to the distance (32.4 A) between the center of mass of the spin density distribution of each Y* on each R2 monomer from the structure. The experiments provide the first direct experimental evidence for two Y*'s in a single R2 in solution.

Related Papers

• → Ribonucleotide reductases — a group of enzymes with different metallosites and a similar reaction mechanism(1997)145 cited
• → Regulation of Ribonucleotide Reductase(1981)105 cited
• → A rapid and sensitive assay for quantifying the activity of both aerobic and anaerobic ribonucleotide reductases acting upon any or all substrates(2022)6 cited
• → Mouse Ribonucleotide Reductase Control(2001)30 cited
• → Regulation of Synthesis of Ribonucleotide Reductase and Relationship to DNA Replication in Various Systems(1996)20 cited