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Journal of Bacteriology, November 2001, p. 6517-6524, Vol. 183, No. 22
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.22.6517-6524.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Molecular Characterization and Regulation of the aguBA Operon, Responsible for Agmatine Utilization in Pseudomonas aeruginosa PAO1

Yuji Nakada,1 Ying Jiang,2 Takayuki Nishijyo,1 Yoshifumi Itoh,1 and Chung-Dar Lu2,*

National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan,1 and Department of Biology, Georgia State University, Atlanta, Georgia 303032

Received 30 May 2001/Accepted 22 August 2001

Pseudomonas aeruginosa PAO1 utilizes agmatine as the sole carbon and nitrogen source via two reactions catalyzed successively by agmatine deiminase (encoded by aguA; also called agmatine iminohydrolase) and N-carbamoylputrescine amidohydrolase (encoded by aguB). The aguBA and adjacent aguR genes were cloned and characterized. The predicted AguB protein (Mr 32,759; 292 amino acids) displayed sequence similarity (<= 60% identity) to enzymes of the beta -alanine synthase/nitrilase family. While the deduced AguA protein (Mr 41,190; 368 amino acids) showed no significant similarity to any protein of known function, assignment of agmatine deiminase to AguA in this report discovered a new family of carbon-nitrogen hydrolases widely distributed in organisms ranging from bacteria to Arabidopsis. The aguR gene encoded a putative regulatory protein (Mr 24,424; 221 amino acids) of the TetR protein family. Measurements of agmatine deiminase and N-carbamoylputrescine amidohydrolase activities indicated the induction effect of agmatine and N-carbamoylputrescine on expression of the aguBA operon. The presence of an inducible promoter for the aguBA operon in the aguR-aguB intergenic region was demonstrated by lacZ fusion experiments, and the transcription start of this promoter was localized 99 bp upstream from the initiation codon of aguB by S1 nuclease mapping. Experiments with knockout mutants of aguR established that expression of the aguBA operon became constitutive in the aguR background. Interaction of AguR overproduced in Escherichia coli with the aguBA regulatory region was demonstrated by gel retardation assays, supporting the hypothesis that AguR serves as the negative regulator of the aguBA operon, and binding of agmatine and N-carbamoylputrescine to AguR would antagonize its repressor function.

* Corresponding author. Mailing address: Department of Biology, Georgia State University, P.O. Box 4010, Atlanta, GA 30302-4010. Phone: (404) 651-2531. Fax: (404) 651-2509. E-mail: biocdl{at}panther.gsu.edu.

Journal of Bacteriology, November 2001, p. 6517-6524, Vol. 183, No. 22
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.22.6517-6524.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.