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Journal of Bacteriology, December 2004, p. 7888-7895, Vol. 186, No. 23
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.23.7888-7895.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Rubrerythrin from the Hyperthermophilic Archaeon Pyrococcus furiosus Is a Rubredoxin-Dependent, Iron-Containing Peroxidase

Michael V. Weinberg, Francis E. Jenney Jr., Xiaoyuan Cui,{dagger} and Michael W. W. Adams*

Department of Biochemistry & Molecular Biology and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia

Received 29 April 2004/ Accepted 20 August 2004

Rubrerythrin was purified by multistep chromatography under anaerobic, reducing conditions from the hyperthermophilic archaeon Pyrococcus furiosus. It is a homodimer with a molecular mass of 39.2 kDa and contains 2.9 ± 0.2 iron atoms per subunit. The purified protein had peroxidase activity at 85°C using hydrogen peroxide with reduced P. furiosus rubredoxin as the electron donor. The specific activity was 36 µmol of rubredoxin oxidized/min/mg with apparent Km values of 35 and 70 µM for hydrogen peroxide and rubredoxin, respectively. When rubrerythrin was combined with rubredoxin and P. furiosus NADH:rubredoxin oxidoreductase, the complete system used NADH as the electron donor to reduce hydrogen peroxide with a specific activity of 7.0 µmol of H2O2 reduced/min/mg of rubrerythrin at 85°C. Strangely, as-purified (reduced) rubrerythrin precipitated when oxidized by either hydrogen peroxide, air, or ferricyanide. The gene (PF1283) encoding rubrerythrin was expressed in Escherichia coli grown in medium with various metal contents. The purified recombinant proteins each contained approximately three metal atoms/subunit, ranging from 0.4 Fe plus 2.2 Zn to 1.9 Fe plus 1.2 Zn, where the metal content of the protein depended on the metal content of the E. coli growth medium. The peroxidase activities of the recombinant forms were proportional to the iron content. P. furiosus rubrerythrin is the first to be characterized from a hyperthermophile or from an archaeon, and the results are the first demonstration that this protein functions in an NADH-dependent, hydrogen peroxide:rubredoxin oxidoreductase system. Rubrerythrin is proposed to play a role in the recently defined anaerobic detoxification pathway for reactive oxygen species.


* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Life Sciences Bldg., University of Georgia, Athens, GA 30602-7229. Phone: (706) 542-2060. Fax: (706) 542-0229. E-mail: adams{at}bmb.uga.edu.

{dagger} Present address: National Starch and Chemical Co., Bridgewater, NJ 08807.


Journal of Bacteriology, December 2004, p. 7888-7895, Vol. 186, No. 23
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.23.7888-7895.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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