This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kawasaki, S.
Right arrow Articles by Niimura, Y.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kawasaki, S.
Right arrow Articles by Niimura, Y.
Agricola
Right arrow Articles by Kawasaki, S.
Right arrow Articles by Niimura, Y.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, February 2009, p. 1021-1029, Vol. 75, No. 4
0099-2240/09/$08.00+0     doi:10.1128/AEM.01425-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

O2 and Reactive Oxygen Species Detoxification Complex, Composed of O2-Responsive NADH:Rubredoxin Oxidoreductase-Flavoprotein A2-Desulfoferrodoxin Operon Enzymes, Rubperoxin, and Rubredoxin, in Clostridium acetobutylicum{triangledown} ,{dagger}

Shinji Kawasaki,* Yu Sakai, Tohru Takahashi, Ippei Suzuki, and Youichi Niimura

Department of Biosciences, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan

Received 26 June 2008/ Accepted 8 December 2008

Clostridium acetobutylicum, an obligate anaerobe, grows normally under continuous-O2-flow culture conditions, where the cells consume O2 proficiently. An O2-responsive NADH:rubredoxin oxidoreductase operon composed of three genes (nror, fprA2, and dsr), encoding NROR, functionally uncharacterized flavoprotein A2 (FprA2), and the predicted superoxide reductase desulfoferrodoxin (Dsr), has been proposed to participate in defense against O2 stress. To functionally characterize these proteins, native NROR from C. acetobutylicum, recombinant NROR (rNROR), FprA2, Dsr, and rubredoxin (Rd) expressed in Escherichia coli were purified. Purified native NROR and rNROR both exhibited weak H2O2-forming NADH oxidase activity that was slightly activated by Rd. A mixture of NROR, Rd, and FprA2 functions as an efficient H2O-forming NADH oxidase with a high affinity for O2 (the Km for O2 is 2.9 ± 0.4 µM). A mixture of NROR, Rd, and Dsr functions as an NADH-dependent O2– reductase. A mixture of NROR, Rd, and rubperoxin (Rpr, a rubrerythrin homologue) functions as an inefficient H2O-forming NADH oxidase but an efficient NADH peroxidase with a low affinity for O2 and a high affinity for H2O2 (the Kms for O2 and H2O2 are 303 ± 39 µM and ≤1 µM, respectively). A gene encoding Rd is dicistronically transcribed with a gene encoding a glutaredoxin (Gd) homologue, and the expression levels of the genes encoding Gd and Rd were highly upregulated upon exposure to O2. Therefore, nror operon enzymes, together with Rpr, efficiently function to scavenge O2, O2–, and H2O2 by using an O2-responsive rubredoxin as a common electron carrier protein.

* Corresponding author. Mailing address: Department of Bioscience, Tokyo University of Agriculture, 1-1-1 Setagaya-ku, Tokyo 156-8502, Japan. Phone and fax: 81-3-5477-2764. E-mail: kawashin{at}nodai.ac.jp

{triangledown} Published ahead of print on 5 January 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, February 2009, p. 1021-1029, Vol. 75, No. 4
0099-2240/09/$08.00+0     doi:10.1128/AEM.01425-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»