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Journal of Bacteriology, November 2009, p. 6709-6721, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00932-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The PqrR Transcriptional Repressor of Pseudomonas aeruginosa Transduces Redox Signals via an Iron-Containing Prosthetic Group{triangledown} ,{dagger}

Wanilada Rungrassamee,1,# Kelly C. Ryan,2 Michael J. Maroney,2 and Pablo J. Pomposiello1,3*

Department of Microbiology,1 Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003,2 Microbionta S.L., 28760 Tres Cantos, Madrid, Spain3

Received 16 July 2009/ Accepted 24 August 2009

Inducible defenses against oxidative stress are coordinated by redox-sensitive transcription factors that transduce oxidative damage into differential gene expression. The opportunistic human pathogen Pseudomonas aeruginosa has evolved under physiological and host-derived sources of oxidative stress. Previous work showed that the pqrABC and pqrR genes of P. aeruginosa, all lacking known functions, were induced by treatment of three different isolates of P. aeruginosa with paraquat (PQ), a superoxide-producing agent. Insertional mutation of the pqrABCR genes resulted in hypersensitive phenotypes to a variety of oxidants, although the hypersensitivity to PQ was marginal. Mutation of pqrR and complementation assays showed that PqrR regulated the pqrABC genes in response to PQ. PqrR, a member of the MarR family of transcriptional regulators, contains a C-terminal region with four conserved cysteines, which suggested redox-regulated transcriptional activity. Purified PqrR bound to two discrete sites at the pqrA and pqrR regulatory regions. The in vitro DNA binding activity of PqrR was decreased by exposure to air and reconstituted by treatment with DL-dithiothreitol. Elemental analysis and preliminary electron paramagnetic resonance experiments showed that PqrR contains iron. Interestingly, site-directed mutagenesis of C-terminal cysteines demonstrated that the four conserved cysteine residues are essential for in vivo redox sensing by PqrR.

* Corresponding author. Mailing address: Microbionta S.L., 28760 Tres Cantos, Madrid, Spain. Phone: (34) 91-806-0068, ext. 60. Fax: (34) 91-141-7151. E-mail: ppomposiello{at}microbionta.com

{triangledown} Published ahead of print on 28 August 2009.

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

# Present address: National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Thailand Science Park, Phahonyothin Road, Klong 1, Klong Luang, Pathum Thani 12120, Thailand.

Journal of Bacteriology, November 2009, p. 6709-6721, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00932-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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