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PMID:9422605

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Citation

Sadowsky, MJ, Tong, Z, de Souza, M and Wackett, LP (1998) AtzC is a new member of the amidohydrolase protein superfamily and is homologous to other atrazine-metabolizing enzymes. J. Bacteriol. 180:152-8

Abstract

Pseudomonas sp. strain ADP metabolizes atrazine to cyanuric acid via three plasmid-encoded enzymes, AtzA, AtzB, and AtzC. The first enzyme, AtzA, catalyzes the hydrolytic dechlorination of atrazine, yielding hydroxyatrazine. The second enzyme, AtzB, catalyzes hydroxyatrazine deamidation, yielding N-isopropylammelide. In this study, the third gene in the atrazine catabolic pathway, atzC, was cloned from a Pseudomonas sp. strain ADP cosmid library as a 25-kb EcoRI DNA fragment in Escherichia coli. The atzC gene was further delimited by functional analysis following transposon Tn5 mutagenesis and subcloned as a 2.0-kb EcoRI-AvaI fragment. An E. coli strain containing this DNA fragment expressed N-isopropylammelide isopropylamino hydrolase activity, metabolizing N-isopropylammelide stoichiometrically to cyanuric acid and N-isopropylamine. The 2.0-kb DNA fragment was sequenced and found to contain a single open reading frame of 1,209 nucleotides, encoding a protein of 403 amino acids. AtzC showed modest sequence identity of 29 and 25%, respectively, to cytosine deaminase and dihydroorotase, both members of an amidohydrolase protein superfamily. The sequence of AtzC was compared to that of E. coli cytosine deaminase in the regions containing the five ligands to the catalytically important metal for the protein. Pairwise comparison of the 35 amino acids showed 61% sequence identity and 85% sequence similarity. AtzC is thus assigned to the amidohydrolase protein family that includes cytosine deaminase, urease, adenine deaminase, and phosphotriester hydrolase. Similar sequence comparisons of the most highly conserved regions indicated that the AtzA and AtzB proteins also belong to the same amidohydrolase family. Overall, the data suggest that AtzA, AtzB, and AtzC diverged from a common ancestor and, by random events, have been reconstituted onto an atrazine catabolic plasmid.

Links

PubMed PMC106861

Keywords

Amidohydrolases/chemistry; Amidohydrolases/genetics; Amino Acid Sequence; Atrazine/metabolism; Bacterial Proteins; Base Composition; Base Sequence; Cloning, Molecular; DNA, Bacterial/chemistry; DNA, Bacterial/genetics; Escherichia coli/genetics; Evolution, Molecular; Genes, Bacterial/genetics; Hydrolases/genetics; Molecular Sequence Data; Molecular Weight; Mutagenesis, Insertional; Pseudomonas/enzymology; Pseudomonas/genetics; Recombinant Fusion Proteins; Restriction Mapping; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Amino Acid

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

PSESD:ATZC

Contributes to

GO:0018764: N-isopropylammelide isopropylaminohydrolase activity

ECO:0000314:

F

AtzC codes for the enzyme which transforms N-isopropylammelide to cyanuric acid and isopropylamine by hydrolytic deamination.

Table 1 shows the control strain of Pseduomonas had this activity. The E.coli strains which had a plasmid insterted containing the AtzC gene also transformed N-isopropylammelide to cyanuric acid and isopropylamine.

complete
CACAO 4878


See also

References

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