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Aspartate transcarbamoylase genes of Pseudomonas putida: requirement for an inactive dihydroorotase for assembly into the dodecameric holoenzyme.
- Source :
-
Journal of bacteriology [J Bacteriol] 1995 Apr; Vol. 177 (7), pp. 1751-9. - Publication Year :
- 1995
-
Abstract
- The nucleotide sequences of the genes encoding the enzyme aspartate transcarbamoylase (ATCase) from Pseudomonas putida have been determined. Our results confirm that the P. putida ATCase is a dodecameric protein composed of two types of polypeptide chains translated coordinately from overlapping genes. The P. putida ATCase does not possess dissociable regulatory and catalytic functions but instead apparently contains the regulatory nucleotide binding site within a unique N-terminal extension of the pyrB-encoded subunit. The first gene, pyrB, is 1,005 bp long and encodes the 334-amino-acid, 36.4-kDa catalytic subunit of the enzyme. The second gene is 1,275 bp long and encodes a 424-residue polypeptide which bears significant homology to dihydroorotase (DHOase) from other organisms. Despite the homology of the overlapping gene to known DHOases, this 44.2-kDa polypeptide is not considered to be the functional product of the pyrC gene in P. putida, as DHOase activity is distinct from the ATCase complex. Moreover, the 44.2-kDa polypeptide lacks specific histidyl residues thought to be critical for DHOase enzymatic function. The pyrC-like gene (henceforth designated pyrC') does not complement Escherichia coli pyrC auxotrophs, while the cloned pyrB gene does complement pyrB auxotrophs. The proposed function for the vestigial DHOase is to maintain ATCase activity by conserving the dodecameric assembly of the native enzyme. This unique assembly of six active pyrB polypeptides coupled with six inactive pyrC' polypeptides has not been seen previously for ATCase but is reminiscent of the fused trifunctional CAD enzyme of eukaryotes.
- Subjects :
- Amino Acid Sequence
Aspartate Carbamoyltransferase chemistry
Aspartate Carbamoyltransferase isolation & purification
Cloning, Molecular
Dihydroorotase genetics
Molecular Sequence Data
Pseudomonas putida enzymology
Sequence Alignment
Aspartate Carbamoyltransferase genetics
Dihydroorotase physiology
Genes, Bacterial
Pseudomonas putida genetics
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9193
- Volume :
- 177
- Issue :
- 7
- Database :
- MEDLINE
- Journal :
- Journal of bacteriology
- Publication Type :
- Academic Journal
- Accession number :
- 7896697
- Full Text :
- https://doi.org/10.1128/jb.177.7.1751-1759.1995