title: A manganese(IV)/iron(III) cofactor in Chlamydia trachomatis ribonucleotide reductase.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: Danny
authors.initials: D
authors.lastname: Yun
authors.forename: Lana
authors.initials: L
authors.lastname: Saleh
authors.forename: Eric W
authors.initials: EW
authors.lastname: Barr
authors.forename: Gang
authors.initials: G
authors.lastname: Xing
authors.forename: Lee M
authors.initials: LM
authors.lastname: Hoffart
authors.forename: Monique-Anne
authors.initials: MA
authors.lastname: Maslak
authors.forename: Carsten
authors.initials: C
authors.lastname: Krebs
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bollinger
mesh_terms: D002692:Chlamydia trachomatis / Q000201:enzymology*; D003067:Coenzymes / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation; D005290:Ferric Compounds / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D003067:Coenzymes; D005290:Ferric Compounds; D014443:Tyrosine; D008345:Manganese; D007501:Iron; D012264:Ribonucleotide Reductases