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Microbiology 155 (2009), 16-24; DOI  10.1099/mic.0.022756-0
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Microbiology 155 (2009), 16-24; DOI  10.1099/mic.0.022756-0
© 2009 Society for General Microbiology

Pathway for H2O2 and O2 detoxification in Clostridium acetobutylicum

Oliver Riebe1, Ralf-Jörg Fischer1, David A. Wampler2, Donald M. Kurtz, Jr2 and Hubert Bahl1

1 Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18051 Rostock, Germany
2 Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA

Correspondence
Hubert Bahl
hubert.bahl{at}uni-rostock.de

An unusual non-haem diiron protein, reverse rubrerythrin (revRbr), is known to be massively upregulated in response to oxidative stress in the strictly anaerobic bacterium Clostridium acetobutylicum. In the present study both in vivo and in vitro results demonstrate an H2O2 and O2 detoxification pathway in C. acetobutylicum involving revRbr, rubredoxin (Rd) and NADH : rubredoxin oxidoreductase (NROR). RevRbr exhibited both NADH peroxidase (NADH : H2O2 oxidoreductase) and NADH oxidase (NADH : O2 oxidoreductase) activities in in vitro assays using NROR as the electron-transfer intermediary from NADH to revRbr. Rd increased the NADH consumption rate by serving as an intermediary electron-transfer shuttle between NROR and revRbr. While H2O2 was found to be the preferred substrate for revRbr, its relative oxidase activity was found to be significantly higher than that reported for other Rbrs. A revRbr-overexpressing strain of C. acetobutylicum showed significantly increased tolerance to H2O2 and O2 exposure. RevRbr thus appears to protect C. acetobutylicum against oxidative stress by functioning as the terminal component of an NADH peroxidase and NADH oxidase.

Abbreviations: Dfx, desulfoferrodoxin; FNR, ferredoxin-NADP+ reductase; HRP, horseradish peroxidase; NROR, NADH : rubredoxin oxidoreductase; Rd, rubredoxin; revRbr, reverse rubrerythrin; ROS, reactive oxygen species; SOD, superoxide dismutase

A supplementary figure is available with the online version of this paper.






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