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  • Title: Pulsed ELDOR spectroscopy measures the distance between the two tyrosyl dadicals in the R2 subunit of the E. coli ribonucleotide reductase.
    Author: Bennati M, Weber A, Antonic J, Perlstein DL, Robblee J, Stubbe J.
    Journal: J Am Chem Soc; 2003 Dec 10; 125(49):14988-9. PubMed ID: 14653724.
    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.
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