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Structure of the high-valent FeIIIFeIVstate in ribonucleotide reductase (RNR) ofChlamydia trachomatis—Combined EPR,57Fe-,1H-ENDOR and X-ray studies

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics
Publication Date
DOI: 10.1016/j.bbapap.2007.07.001
  • Ribonucleotide Reductase Class I
  • Chlamydia Trachomatis
  • Structure Of The High-Valent Fe(Iii)Fe(Iv)Diiron State X
  • F127Y X-Ray Structure
  • 57Fe-Electron Nuclear Double Resonance Endor
  • Medicine


Abstract A recently discovered subgroup of class I ribonucleotide reductase (RNR) found in the infectious bacterium Chlamydia trachomatis ( C. trachomatis) was shown to exhibit a high-valent Fe IIIFe IV center instead of the tyrosyl radical observed normally in all class I RNRs. The X-ray structure showed that C. trachomatis WT RNR has a phenylalanine at the position of the active tyrosine in Escherichia coli RNR. In this paper the X-ray structure of variant F127Y is presented, where the tyrosine is restored. Using 1H- and 57Fe-ENDOR spectroscopy it is shown, that in WT and variants F127Y and Y129F of C. trachomatis RNR, the Fe IIIFe IV center is virtually identical with the short-lived intermediate X observed during the iron oxygen reconstitution reaction in class I RNR from E. coli. The experimental data are consistent with a recent theoretical model for X, proposing two bridging oxo ligands and one terminal water ligand. A surprising extension of the lifetime of the Fe IIIFe IV state in C. trachomatis from a few seconds to several hours at room temperature was observed under catalytic conditions in the presence of substrate. These findings suggest a possible new role for the Fe IIIFe IV state also in other class I RNR, during the catalytic radical transfer reaction, by which the substrate turnover is started.

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