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  • Title: A manganese(IV)/iron(III) cofactor in Chlamydia trachomatis ribonucleotide reductase.
    Author: Jiang W, Yun D, Saleh L, Barr EW, Xing G, Hoffart LM, Maslak MA, Krebs C, Bollinger JM.
    Journal: Science; 2007 May 25; 316(5828):1188-91. PubMed ID: 17525338.
    Abstract:
    In a conventional class I ribonucleotide reductase (RNR), a diiron(II/II) cofactor in the R2 subunit reacts with oxygen to produce a diiron(III/IV) intermediate, which generates a stable tyrosyl radical (Y*). The Y* reversibly oxidizes a cysteine residue in the R1 subunit to a cysteinyl radical (C*), which abstracts the 3'-hydrogen of the substrate to initiate its reduction. The RNR from Chlamydia trachomatis lacks the Y*, and it had been proposed that the diiron(III/IV) complex in R2 directly generates the C* in R1. By enzyme activity measurements and spectroscopic methods, we show that this RNR actually uses a previously unknown stable manganese(IV)/iron(III) cofactor for radical initiation.
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