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Appl. Environ. Microbiol., Mar 1997, 916-923, Vol 63, No. 3
KL Boundy-Mills, ML de Souza, RT Mandelbaum, LP Wackett and MJ Sadowsky
We previously reported the isolation of a 21.5-kb genomic DNA fragment from
Pseudomonas sp. strain ADP, which contains the atzA gene, encoding the
first metabolic step for the degradation of the herbicide atrazine (M. de
Souza, L. P. Wackett, K. L. Boundy-Mills, R. T. Mandelbaum, and M. J.
Sadowsky, Appl. Environ. Microbiol. 61:3373-3378, 1995). In this study, we
show that this fragment also contained the second gene of the atrazine
metabolic pathway, atzB. AtzB catalyzed the transformation of
hydroxyatrazine to N-isopropylammelide. The product was identified by use
of high-performance liquid chromatography, mass spectrometery, and nuclear
magnetic resonance spectroscopy. Tn5 mutagenesis of pMD1 was used to
determine that atzB was located 8 kb downstream of atzA. Hydroxyatrazine
degradation activity was localized to a 4.0-kb ClaI fragment, which was
subcloned into the vector pACYC184 to produce plasmid pATZB-2. The DNA
sequence of this region was determined and found to contain two large
overlapping divergent open reading frames, ORF1 and ORF2. ORF1 was
identified as the coding region of atzB by demonstrating that (i) only ORF1
was transcribed in Pseudomonas sp. strain ADP, (ii) a Tn5 insertion in ORF2
did not disrupt function, and (iii) codon usage was consistent with ORF1
being translated. AtzB had 25% amino acid identity with TrzA, a protein
that catalyzes a hydrolytic deamination of the s-triazine substrate
melamine. The atzA and atzB genes catalyze the first two steps of the
metabolic pathway in a bacterium that rapidly metabolizes atrazine to
carbon dioxide, ammonia, and chloride.
Copyright © 1997, American Society for Microbiology
The atzB gene of Pseudomonas sp. strain ADP encodes the second enzyme of a novel atrazine degradation pathway
Department of Soil, Water, and Climate, University of Minnesota, St. Paul 55108, USA.
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