Direct Measurement of the Radical Translocation Distance in the Class i Ribonucleotide Reductase from Chlamydia trachomatis

Jovan Livada, Ryan J. Martinie, Laura M.K. Dassama, Carsten Krebs, J. Martin Bollinger, Alexey Silakov

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Ribonucleotide reductases (RNRs) catalyze conversion of ribonucleotides to deoxyribonucleotides in all organisms via a free-radical mechanism that is essentially conserved. In class I RNRs, the reaction is initiated and terminated by radical translocation (RT) between the α and β subunits. In the class Ic RNR from Chlamydia trachomatis (Ct RNR), the initiating event converts the active S = 1 Mn(IV)/Fe(III) cofactor to the S = 1/2 Mn(III)/Fe(III) "RT-product"? form in the β subunit and generates a cysteinyl radical in the α active site. The radical can be trapped via the well-described decomposition reaction of the mechanism-based inactivator, 2′-azido-2′-deoxyuridine-5′-diphosphate, resulting in the generation of a long-lived, nitrogen-centered radical (N) in α. In this work, we have determined the distance between the Mn(III)/Fe(III) cofactor in β and N in α to be 43 ± 1 Å by using double electron-electron resonance experiments. This study provides the first structural data on the Ct RNR holoenzyme complex and the first direct experimental measurement of the inter-subunit RT distance in any class I RNR.

Original languageEnglish (US)
Pages (from-to)13777-13784
Number of pages8
JournalJournal of Physical Chemistry B
Issue number43
StatePublished - Oct 29 2015


All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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