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Giles, TN and Graham, DE (2007) Characterization of an acid-dependent arginine decarboxylase enzyme from Chlamydophila pneumoniae. J. Bacteriol. 189:7376-83


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 (alphabeta)(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.


PubMed PMC2168457 Online version:10.1128/JB.00772-07


Acids/pharmacology; Adaptation, Physiological/genetics; Amino Acid Sequence; Anti-Bacterial Agents/pharmacology; Arginine/metabolism; Carboxy-Lyases/chemistry; Carboxy-Lyases/genetics; Carboxy-Lyases/metabolism; Chlamydiales; Chlamydophila pneumoniae/enzymology; Cloning, Molecular; Drug Resistance, Bacterial/genetics; Drug Resistance, Bacterial/physiology; Enzyme Stability; Escherichia coli/drug effects; Escherichia coli/genetics; Gene Deletion; Genetic Complementation Test; Hydrogen-Ion Concentration; Molecular Sequence Data; Protein Subunits; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/isolation & purification; Recombinant Proteins/metabolism; Sequence Alignment; Substrate Specificity