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Journal of Bacteriology, October 2007, p. 7376-7383, Vol. 189, No. 20
0021-9193/07/$08.00+0     doi:10.1128/JB.00772-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Characterization of an Acid-Dependent Arginine Decarboxylase Enzyme from Chlamydophila pneumoniae{triangledown}

Teresa N. Giles1 and David E. Graham1,2*

Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712,1 Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 787122

Received 17 May 2007/ Accepted 6 August 2007

Genome sequences from members of the Chlamydiales encode diverged homologs of a pyruvoyl-dependent arginine decarboxylase enzyme that nonpathogenic euryarchaea use in polyamine biosynthesis. The Chlamydiales lack subsequent genes required for polyamine biosynthesis and probably obtain polyamines from their host cells. To identify the function of this protein, the CPn1032 homolog from the respiratory pathogen Chlamydophila pneumoniae was heterologously expressed and purified. This protein self-cleaved to form a reactive pyruvoyl group, and the subunits assembled into a thermostable ({alpha}ß)3 complex. The mature enzyme specifically catalyzed the decarboxylation of L-arginine, with an unusually low pH optimum of 3.4. The CPn1032 gene complemented a mutation in the Escherichia coli adiA gene, which encodes a pyridoxal 5'-phosphate-dependent arginine decarboxylase, restoring arginine-dependent acid resistance. Acting together with a putative arginine-agmatine antiporter, the CPn1032 homologs may have evolved convergently to form an arginine-dependent acid resistance system. These genes are the first evidence that obligately intracellular chlamydiae may encounter acidic conditions. Alternatively, this system could reduce the host cell arginine concentration and produce inhibitors of nitric oxide synthase.

* Corresponding author. Mailing address: Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712. Phone: (512) 471-4491. Fax: (512) 471-8696. E-mail: degraham{at}mail.utexas.edu

{triangledown} Published ahead of print on 10 August 2007.

Journal of Bacteriology, October 2007, p. 7376-7383, Vol. 189, No. 20
0021-9193/07/$08.00+0     doi:10.1128/JB.00772-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Smith, C. B., Graham, D. E. (2008). Outer and Inner Membrane Proteins Compose an Arginine-Agmatine Exchange System in Chlamydophila pneumoniae. J. Bacteriol. 190: 7431-7440 [Abstract] [Full Text]  
  • Giles, T. N., Graham, D. E. (2008). Crenarchaeal Arginine Decarboxylase Evolved from an S-Adenosylmethionine Decarboxylase Enzyme. J. Biol. Chem. 283: 25829-25838 [Abstract] [Full Text]  


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