Subunit structure of a class A aspartate transcarbamoylase from Pseudomonas fluorescens.

Bergh, Sandra T.; Evans, David R.

doi:10.1073/pnas.90.21.9818

Cited by 23 publications

(31 citation statements)

References 38 publications

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“…The class A ATCases are large-molecular-mass enzymes (470 to 600 kDa) that were thought to be dimeric until Bergh and Evans (3) showed that the Pseudomonas fluorescens enzyme exists as a trimer with a 34-kDa catalytic chain in a dodecameric association with a 45-kDa chain of unknown origin and function. Similar results from studies with purified protein have been obtained by Shepherdson and McPhail (38) for the ATCase from Pseudomonas syringae.…”

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confidence: 99%

Aspartate transcarbamoylase genes of Pseudomonas putida: requirement for an inactive dihydroorotase for assembly into the dodecameric holoenzyme

et al. 1995

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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.

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Aspartate transcarbamoylase genes of Pseudomonas putida: requirement for an inactive dihydroorotase for assembly into the dodecameric holoenzyme

et al. 1995

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“…An explanation for this could be that the catalytic and non- catalytic subunits dissociate very readily in these species, although we regard this as unlikely in view of the known stable binding of the two types of subunit in the fluorescent pseudomonads (Bergh & Evans, 1993 ;Shepherdson & McPhail, 1993). We have tried to exclude the possibility that the 100 kDa enzymes identified in this study are dissociation products of class A or class B ATCases.…”

Section: Discussionmentioning

confidence: 97%

“…The reasons for purifying this enzyme were similar. It has been shown that three fluorescent pseudomonads have ATCases with molecular mass values in the 480 kDa region and are constructed from polypeptides of around 34 and 45 kDa (Bergh & Evans, 1993 ; organisms within these groups. One such cluster-in the y-3 group is the fluorescent pseudomonads, the acinetobacters, the xanthomonads, S. maltophilia and lysobacters.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, three of these enzymes have been purified (Bergh & Evans, 1993;Shepherdson & McPhail, 1993;Schurr e t al., 1995) and shown to have molecular masses in the region of 480 kDa. In addition to the 34 kDa polypeptide chains of the catalytic subunit, the molecules contain polypeptide chains of around 45 kDa.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to the 34 kDa polypeptide chains of the catalytic subunit, the molecules contain polypeptide chains of around 45 kDa. It is proposed that the 34 kDa chains form two catalytic trimers which associate with six ' ' Cases molecular size, which varies depending on has not been achieved (Bergh & Evans, 1993 ; Shepherd-Class B ATCases include those from the enteric bacteria of which the ATCase from E. coli has been extensively studied; the molecule has two catalytic trimers and three homodimers of 17 kDa chains which mediate very precise allosteric regulation of activity by binding nucleotides (reviewed by Kantrowitz & Lipscomb, 1990). The molecular mass of ATCases in this group is approximately 300 kDa.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A reappraisal of the diversity and class distribution of aspartate transcarbamoylases in Gram-negative bacteria

1996

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Comparison of aspartate transcarbamoylase regulation in Pseudomonas alcaligenes and Pseudomonas mendocina

Santiago

West²

2003

J. Basic Microbiol.

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The regulation of aspartate transcarbamoylase activity in cell extracts of Pseudomonas alcaligenes ATCC 14909 and Pseudomonas mendocina ATCC 25411 was compared. Under saturating substrate concentrations, pyrophosphate, CTP, UDP and ADP were highly inhibitory of the P. alcaligenes transcarbamoylase activity while pyrophosphate, UDP, ADP, ATP and GTP were the most effective inhibitors of the P. mendocina transcarbamoylase. By examining transcarbamoylase inhibition by ribonucleotide triphosphates, it was possible to differentiate these species assigned to different DNA homology groups and such an analysis might prove useful in the reclassification of Pseudomonas species.

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Subunit structure of a class A aspartate transcarbamoylase from Pseudomonas fluorescens.

Abstract: The

Cited by 23 publications

References 38 publications

Aspartate transcarbamoylase genes of Pseudomonas putida: requirement for an inactive dihydroorotase for assembly into the dodecameric holoenzyme

Aspartate transcarbamoylase genes of Pseudomonas putida: requirement for an inactive dihydroorotase for assembly into the dodecameric holoenzyme

A reappraisal of the diversity and class distribution of aspartate transcarbamoylases in Gram-negative bacteria

Comparison of aspartate transcarbamoylase regulation in Pseudomonas alcaligenes and Pseudomonas mendocina

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