Identification and sequencing of pyrG, the CTP synthetase gene of Azospirillum brasilense Sp7

Abstract An 18.5-kb DNA fragment carrying the trpGDC cluster of Azospirillum brasilense Sp7 was previously cloned, yielding cosmid pAB1005. Attempts to identify trpA in the vicinity of trpGDC failed but led to the detection of a locus strongly homologous to pyrG , the structural gene for the CTP synthetase. The function of the A. brasilense pyrG gene was verified by complementation of the cytidine-requiring PyrG-deficient mutant JF646 of Escherichia coli . A second open reading frame was identified downstream of pyrG . The deduced amino acid sequence showed homology to dienelactone hydrolases of Pseudomonas and Alcaligenes , enzymes involved in utilization of halogenated aromatic compounds.