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J. Biol. Chem., Vol. 282, Issue 38, 27792-27801, September 21, 2007

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The Significance of Type II and PrxQ Peroxiredoxins for Antioxidative Stress Response in the Purple Bacterium Rhodobacter sphaeroides^*

Masahiro Wakita, Shinji Masuda¹, Ken Motohashi^¶, Toru Hisabori^¶, Hiroyuki Ohta^||2, and Ken-ichiro Takamiya^||

From the Graduate School of Bioscience and Biotechnology, Chemical Resources Laboratory, ^||Research Center for the Evolving Earth and Planets, Tokyo Institute of Technology, Yokohama 226-8501 and the ^¶ATP System Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Yokohama 226-0026, Japan

Two peroxiredoxins, classified as Type II and PrxQ, were characterized in the purple non-sulfur photosynthetic bacterium Rhodobacter sphaeroides. Both recombinant proteins showed remarkable thioredoxin-dependent peroxidase activity with broad substrate specificity in vitro. Nevertheless, PrxQ of R. sphaeroides, unlike typical PrxQs studied to date, does not contain one of the two conserved catalytic Cys residues. We found that R. sphaeroides PrxQ and other PrxQ-like proteins from several organisms conserve a different second Cys residue, indicating that these proteins should be categorized into a novel PrxQ subfamily. Disruption of either the Type II or PrxQ gene in R. sphaeroides had a dramatic effect on cell viability when the cells were grown under aerobic light or oxidative stress conditions created by exogenous addition of reactive oxygen species to the medium. Growth rates of the mutants were significantly decreased compared with that of wild type under aerobic but not anaerobic conditions. These results indicate that the peroxiredoxins are crucial for antioxidative stress response in this bacterium. The gene disruptants also demonstrated reduced levels of photopigment synthesis, suggesting that the peroxiredoxins are directly or indirectly involved in regulated synthesis of the photosynthetic apparatus.

Received for publication, April 4, 2007 , and in revised form, July 20, 2007.

^* This work was supported in part by the Sumitomo Foundation, Research Foundation For Opto-Science and Technology, Grant-in-aid for Young Scientists (B) 19770028 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (to S. M.), and Grant-in-aid for Scientific Research on Priority Areas 17051009 from MEXT (to H. O.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1.

This paper is dedicated to the late Prof. K. Takamiya.

² Present address: Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama 226–8501, Japan.

¹ To whom correspondence should be addressed. Tel.: 81-45-924-5737; Fax: 81-45-924-5823; E-mail: shmasuda{at}bio.titech.ac.jp.

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