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1: Science. 2007 May 25;316(5828):1188-91.
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A manganese(IV)/iron(III) cofactor in Chlamydia trachomatis ribonucleotide reductase.

Jiang W, Yun D, Saleh L, Barr EW, Xing G, Hoffart LM, Maslak MA, Krebs C, Bollinger JM Jr.

Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.

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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PMID: 17525338 [PubMed - indexed for MEDLINE]