A Manganese(IV)/Iron(III) Cofactor in Chlamydia trachomatis Ribonucleotide Reductase
Wei Jiang,1
Danny Yun,1*
Lana Saleh,1
Eric W. Barr,1
Gang Xing,1
Lee M. Hoffart,1
Monique-Anne Maslak,1
Carsten Krebs,1,2
J. Martin Bollinger, Jr.1,2
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.
1 Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
2 Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA.
* Present address: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Present address: New England Biolabs, 240 County Road, Ipswich, MA 01938, USA.
To whom correspondence should be addressed. E-mail: ckrebs{at}psu.edu (C.K.), jmb21{at}psu.edu (J.M.B.)
