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Nielipinski M, Pietrzyk-Brzezinska AJ, Wlodawer A, Sekula B. Structural analysis and molecular substrate recognition properties of Arabidopsis thaliana ornithine transcarbamylase, the molecular target of phaseolotoxin produced by Pseudomonas syringae. FRONTIERS IN PLANT SCIENCE 2023; 14:1297956. [PMID: 38179474 PMCID: PMC10765591 DOI: 10.3389/fpls.2023.1297956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 11/17/2023] [Indexed: 01/06/2024]
Abstract
Halo blight is a plant disease that leads to a significant decrease in the yield of common bean crops and kiwi fruits. The infection is caused by Pseudomonas syringae pathovars that produce phaseolotoxin, an antimetabolite which targets arginine metabolism, particularly by inhibition of ornithine transcarbamylase (OTC). OTC is responsible for production of citrulline from ornithine and carbamoyl phosphate. Here we present the first crystal structures of the plant OTC from Arabidopsis thaliana (AtOTC). Structural analysis of AtOTC complexed with ornithine and carbamoyl phosphate reveals that OTC undergoes a significant structural transition when ornithine enters the active site, from the opened to the closed state. In this study we discuss the mode of OTC inhibition by phaseolotoxin, which seems to be able to act only on the fully opened active site. Once the toxin is proteolytically cleaved, it mimics the reaction transition state analogue to fit inside the fully closed active site of OTC. Additionally, we indicate the differences around the gate loop region which rationally explain the resistance of some bacterial OTCs to phaseolotoxin.
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Affiliation(s)
- Maciej Nielipinski
- Institute of Molecular and Industrial Biotechnology, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, Lodz, Poland
| | - Agnieszka J. Pietrzyk-Brzezinska
- Institute of Molecular and Industrial Biotechnology, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, Lodz, Poland
| | - Alexander Wlodawer
- Center for Structural Biology, National Cancer Institute, Frederick, MD, United States
| | - Bartosz Sekula
- Institute of Molecular and Industrial Biotechnology, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, Lodz, Poland
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2
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Characterization and assembly of the Pseudomonas aeruginosa aspartate transcarbamoylase-pseudo dihydroorotase complex. PLoS One 2020; 15:e0229494. [PMID: 32126100 PMCID: PMC7053772 DOI: 10.1371/journal.pone.0229494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 02/09/2020] [Indexed: 02/02/2023] Open
Abstract
Pseudomonas aeruginosa is a virulent pathogen that has become more threatening with the emergence of multidrug resistance. The aspartate transcarbamoylase (ATCase) of this organism is a dodecamer comprised of six 37 kDa catalytic chains and six 45 kDa chains homologous to dihydroorotase (pDHO). The pDHO chain is inactive but is necessary for ATCase activity. A stoichiometric mixture of the subunits associates into a dodecamer with full ATCase activity. Unlike other known ATCases, the P. aeruginosa catalytic chain does not spontaneously assemble into a trimer. Chemical-crosslinking and size-exclusion chromatography showed that P. aeruginosa ATCase is monomeric which accounts for its lack of catalytic activity since the active site is a composite comprised of residues from adjacent monomers in the trimer. Circular dichroism spectroscopy indicated that the ATCase chain adopts a structure that contains secondary structure elements although neither the ATCase nor the pDHO subunits are very stable as determined by a thermal shift assay. Formation of the complex increases the melting temperature by about 30°C. The ATCase is strongly inhibited by all nucleotide di- and triphosphates and exhibits extreme cooperativity. Previous studies suggested that the regulatory site is located in an 11-residue extension of the amino end of the catalytic chain. However, deletion of the extensions did not affect catalytic activity, nucleotide inhibition or the assembly of the dodecamer. Nucleotides destabilized the dodecamer which probably accounts for the inhibition and apparent cooperativity of the substrate saturation curves. Contrary to previous interpretations, these results suggest that P. aeruginosa ATCase is not allosterically regulated by nucleotides.
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3
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Del Caño-Ochoa F, Moreno-Morcillo M, Ramón-Maiques S. CAD, A Multienzymatic Protein at the Head of de Novo Pyrimidine Biosynthesis. Subcell Biochem 2020; 93:505-538. [PMID: 31939163 DOI: 10.1007/978-3-030-28151-9_17] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
CAD is a 1.5 MDa particle formed by hexameric association of a 250 kDa protein that carries the enzymatic activities for the first three steps in the de novo biosynthesis of pyrimidine nucleotides: glutamine-dependent Carbamoyl phosphate synthetase, Aspartate transcarbamoylase and Dihydroorotase. This metabolic pathway is essential for cell growth and proliferation and is conserved in all living organisms. However, the fusion of the first three enzymatic activities of the pathway into a single multienzymatic protein only occurs in animals. In prokaryotes, by contrast, these activities are encoded as distinct monofunctional enzymes that function independently or by forming more or less transient complexes. Whereas the structural information about these enzymes in bacteria is abundant, the large size and instability of CAD has only allowed a fragmented characterization of its structure. Here we retrace some of the most significant efforts to decipher the architecture of CAD and to understand its catalytic and regulatory mechanisms.
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Affiliation(s)
- Francisco Del Caño-Ochoa
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain
| | - María Moreno-Morcillo
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain
| | - Santiago Ramón-Maiques
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain.
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4
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Shi D, Allewell NM, Tuchman M. From Genome to Structure and Back Again: A Family Portrait of the Transcarbamylases. Int J Mol Sci 2015; 16:18836-64. [PMID: 26274952 PMCID: PMC4581275 DOI: 10.3390/ijms160818836] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 07/29/2015] [Accepted: 07/30/2015] [Indexed: 11/18/2022] Open
Abstract
Enzymes in the transcarbamylase family catalyze the transfer of a carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate. The two best-characterized members, aspartate transcarbamylase (ATCase) and ornithine transcarbamylase (OTCase), are present in most organisms from bacteria to humans. Recently, structures of four new transcarbamylase members, N-acetyl-l-ornithine transcarbamylase (AOTCase), N-succinyl-l-ornithine transcarbamylase (SOTCase), ygeW encoded transcarbamylase (YTCase) and putrescine transcarbamylase (PTCase) have also been determined. Crystal structures of these enzymes have shown that they have a common overall fold with a trimer as their basic biological unit. The monomer structures share a common CP binding site in their N-terminal domain, but have different second substrate binding sites in their C-terminal domain. The discovery of three new transcarbamylases, l-2,3-diaminopropionate transcarbamylase (DPTCase), l-2,4-diaminobutyrate transcarbamylase (DBTCase) and ureidoglycine transcarbamylase (UGTCase), demonstrates that our knowledge and understanding of the spectrum of the transcarbamylase family is still incomplete. In this review, we summarize studies on the structures and function of transcarbamylases demonstrating how structural information helps to define biological function and how small structural differences govern enzyme specificity. Such information is important for correctly annotating transcarbamylase sequences in the genome databases and for identifying new members of the transcarbamylase family.
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Affiliation(s)
- Dashuang Shi
- Center for Genetic Medicine Research, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
- Department of Integrative Systems Biology, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
| | - Norma M Allewell
- Department of Cell Biology and Molecular Genetics, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, MD 20742, USA.
- Department of Chemistry and Biochemistry, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, MD 20742, USA.
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
- Department of Integrative Systems Biology, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
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5
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Kanagarajan S, Mutharasappan N, Dhamodharan P, Jeyaraman M, Ramadas K, Jeyaraman J. Exploring the structural features of Aspartate Trans Carbamoylase (TtATCase) fromThermus thermophilusHB8 through in silico approaches: a potential drug target for inborn error of pyrimidine metabolism. J Biomol Struct Dyn 2013; 32:591-601. [DOI: 10.1080/07391102.2013.782825] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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6
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Peterson AW, Cockrell GM, Kantrowitz ER. A second allosteric site in Escherichia coli aspartate transcarbamoylase. Biochemistry 2012; 51:4776-8. [PMID: 22667327 DOI: 10.1021/bi3006219] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Escherichia coli aspartate transcarbamoylase is feedback inhibited by CTP and UTP in the presence of CTP. Here, we show by X-ray crystallography that UTP binds to a unique site on each regulatory chain of the enzyme that is near but not overlapping with the known CTP site. These results bring into question all of the previously proposed mechanisms of allosteric regulation in aspartate transcarbamoylase.
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Affiliation(s)
- Alexis W Peterson
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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7
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Harris KM, Cockrell GM, Puleo DE, Kantrowitz ER. Crystallographic snapshots of the complete catalytic cycle of the unregulated aspartate transcarbamoylase from Bacillus subtilis. J Mol Biol 2011; 411:190-200. [PMID: 21663747 PMCID: PMC3211067 DOI: 10.1016/j.jmb.2011.05.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 05/19/2011] [Accepted: 05/24/2011] [Indexed: 01/07/2023]
Abstract
Here, we report high-resolution X-ray structures of Bacillus subtilis aspartate transcarbamoylase (ATCase), an enzyme that catalyzes one of the first reactions in pyrimidine nucleotide biosynthesis. Structures of the enzyme have been determined in the absence of ligands, in the presence of the substrate carbamoyl phosphate, and in the presence of the bisubstrate/transition state analog N-phosphonacetyl-L-aspartate. Combining the structural data with in silico docking and electrostatic calculations, we have been able to visualize each step in the catalytic cycle of ATCase, from the ordered binding of the substrates, to the formation and decomposition of the tetrahedral intermediate, to the ordered release of the products from the active site. Analysis of the conformational changes associated with these steps provides a rationale for the lack of cooperativity in trimeric ATCases that do not possess regulatory subunits.
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Affiliation(s)
- Katharine M. Harris
- Department of Chemistry, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467 USA
| | - Gregory M. Cockrell
- Department of Chemistry, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467 USA
| | - David E. Puleo
- Department of Chemistry, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467 USA
| | - Evan R. Kantrowitz
- Department of Chemistry, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467 USA
- Corresponding author. E. R. Kantrowitz, Department of Chemistry, Boston College, Merkert Chemistry Center 239, Chestnut Hill, MA 02467 USA.,
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8
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Matoba K, Nara T, Aoki T, Honma T, Tanaka A, Inoue M, Matsuoka S, Inaoka DK, Kita K, Harada S. Crystallization and preliminary X-ray analysis of aspartate transcarbamoylase from the parasitic protist Trypanosoma cruzi. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:933-6. [PMID: 19724137 PMCID: PMC2795605 DOI: 10.1107/s1744309109031959] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Accepted: 08/12/2009] [Indexed: 05/28/2023]
Abstract
Aspartate transcarbamoylase (ATCase), the second enzyme of the de novo pyrimidine-biosynthetic pathway, catalyzes the production of carbamoyl aspartate from carbamoyl phosphate and L-aspartate. In contrast to Escherichia coli ATCase and eukaryotic CAD multifunctional fusion enzymes, Trypanosoma cruzi ATCase lacks regulatory subunits and is not part of the multifunctional fusion enzyme. Recombinant T. cruzi ATCase expressed in E. coli was purified and crystallized in a ligand-free form and in a complex with carbamoyl phosphate at 277 K by the sitting-drop vapour-diffusion technique using polyethylene glycol 3350 as a precipitant. Ligand-free crystals (space group P1, unit-cell parameters a = 78.42, b = 79.28, c = 92.02 A, alpha = 69.56, beta = 82.90, gamma = 63.25 degrees) diffracted X-rays to 2.8 A resolution, while those cocrystallized with carbamoyl phosphate (space group P2(1), unit-cell parameters a = 88.41, b = 158.38, c = 89.00 A, beta = 119.66 degrees) diffracted to 1.6 A resolution. The presence of two homotrimers in the asymmetric unit (38 kDa x 6) gives V(M) values of 2.3 and 2.5 A(3) Da(-1) for the P1 and P2(1) crystal forms, respectively.
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Affiliation(s)
- Kazuaki Matoba
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Takeshi Nara
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Takashi Aoki
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Teruki Honma
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan
| | - Akiko Tanaka
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeru Matsuoka
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Daniel Ken Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeharu Harada
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
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9
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Lipscomb WN. Aspartate transcarbamylase from Escherichia coli: activity and regulation. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 68:67-151. [PMID: 8154326 DOI: 10.1002/9780470123140.ch3] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- W N Lipscomb
- Department of Chemistry, Harvard University, Cambridge, MA
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10
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Kilstrup M, Hammer K, Ruhdal Jensen P, Martinussen J. Nucleotide metabolism and its control in lactic acid bacteria. FEMS Microbiol Rev 2005. [DOI: 10.1016/j.fmrre.2005.04.006] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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11
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De Vos D, Hulpiau P, Vergauwen B, Savvides SN, Van Beeumen J. Expression, purification, crystallization and preliminary X-ray crystallographic studies of a cold-adapted aspartate carbamoyltransferase from Moritella profunda. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:279-81. [PMID: 16511017 PMCID: PMC1952289 DOI: 10.1107/s174430910500285x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Accepted: 01/26/2005] [Indexed: 11/11/2022]
Abstract
Aspartate carbamoyltransferase (ATCase) catalyzes the carbamoylation of the alpha-amino group of L-aspartate by carbamoyl phosphate (CP) to yield N-carbamoyl-L-aspartate and orthophosphate in the first step of de novo pyrimidine biosynthesis. Apart from its key role in nucleotide metabolism, the enzyme is generally regarded as a model system in the study of proteins exhibiting allosteric behaviour. Here, the successful preparation, crystallization and diffraction data collection of the ATCase from the psychrophilic bacterium Moritella profunda are reported. To date, there is no structural representative of a cold-adapted ATCase. The structure of M. profunda ATCase is thus expected to provide important insights into the molecular basis of allosteric activity at low temperatures. Furthermore, through comparisons with the recently reported structure of an extremely thermostable ATCase from Sulfolobus acidocaldarius, it is hoped to contribute to general principles governing protein adaptation to extreme environments. A complete native data to 2.85 A resolution showed that the crystal belongs to space group P3(2)21, with unit-cell parameters a = 129.25, b = 129.25, c = 207.23 A, alpha = beta = 90, gamma = 120 degrees, and that it contains three catalytic and three regulatory subunits per asymmetric unit. The three-dimensional structure of the Escherichia coli ATCase was sufficient to solve the structure of the M. profunda ATCase via the molecular-replacement method and to obtain electron density of good quality.
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Affiliation(s)
- Dirk De Vos
- Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, K. L. Ledeganckstraat 35, Ghent, Belgium
| | - Paco Hulpiau
- Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, K. L. Ledeganckstraat 35, Ghent, Belgium
| | - Bjorn Vergauwen
- Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, K. L. Ledeganckstraat 35, Ghent, Belgium
| | - Savvas N. Savvides
- Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, K. L. Ledeganckstraat 35, Ghent, Belgium
| | - Jozef Van Beeumen
- Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, K. L. Ledeganckstraat 35, Ghent, Belgium
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12
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Vickrey JF, Herve G, Evans DR. Pseudomonas aeruginosa aspartate transcarbamoylase. Characterization of its catalytic and regulatory properties. J Biol Chem 2002; 277:24490-8. [PMID: 11959858 DOI: 10.1074/jbc.m200009200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aspartate transcarbamoylase from Pseudomonadaceae is a class A enzyme consisting of six copies of a 36-kDa catalytic chain and six copies of a 45-kDa polypeptide of unknown function. The 45-kDa polypeptide is homologous to dihydroorotase but lacks catalytic activity. Pseudomonas aeruginosa aspartate transcarbamoylase was overexpressed in Escherichia coli. The homogeneous His-tagged protein isolated in high yield, 30 mg/liter of culture, by affinity chromatography and crystallized. Attempts to dissociate the catalytic and pseudo-dihydroorotase (pDHO) subunits or to express catalytic subunits only were unsuccessful suggesting that the pDHO subunits are required for the proper folding and assembly of the complex. As reported previously, the enzyme was inhibited by micromolar concentrations of all nucleotide triphosphates. In the absence of effectors, the aspartate saturation curves were hyperbolic but became strongly sigmoidal in the presence of low concentrations of nucleotide triphosphates. The inhibition was unusual in that only free ATP, not MgATP, inhibits the enzyme. Moreover, kinetic and binding studies with a fluorescent ATP analog suggested that ATP induces a conformational change that interferes with the binding of carbamoyl phosphate but has little effect once carbamoyl phosphate is bound. The peculiar allosteric properties suggest that the enzyme may be a potential target for novel chemotherapeutic agents designed to combat Pseudomonas infection.
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Affiliation(s)
- John F Vickrey
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michiagan 48201, USA
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13
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Mejias-Torres IA, Zimmermann BH. Molecular cloning, recombinant expression and partial characterization of the aspartate transcarbamoylase from Toxoplasma gondii. Mol Biochem Parasitol 2002; 119:191-201. [PMID: 11814571 DOI: 10.1016/s0166-6851(01)00415-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A cDNA coding for a monofunctional aspartate transcarbamoylase (ATCase) was isolated from a Toxoplasma gondii tachyzoite cDNA library using a complementation method. The calculated molecular mass of the deduced amino acid sequence was 46.8 kDa, with a predicted pI of 7.1. Size exclusion chromatography/laser-light scattering showed a single, monodisperse peak with molecular mass of 144 kDa. Amino acid sequence alignments revealed that active site residues of the Escherichia coli ATCase catalytic chain were conserved in the T. gondii sequence, and the latter shared 26-33% overall sequence identity with other ATCases. A recombinant enzyme was overexpressed in E. coli, and was purified with a yield of approximately 0.8 mg l(-1) culture. The temperature dependence of the recombinant enzyme was similar to that of native ATCase in T. gondii extracts. The K(m)'s for aspartate and carbamoyl phosphate were 7.82 mM, and 67.6 microM, respectively. The V(max) was 23900 micromol h(-1) mg(-1). Pyrimidine nucleotides had no significant effect on the enzyme's activity. N-phosphonoacetyl-L-aspartate (PALA) inhibited the enzyme with K(i)=0.38 microM. The T. gondii ATCases contained two additional sequences of approximately 24 residues each, which are not found in other ATCases. One of these sequences was susceptible to proteolysis by elastase.
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Affiliation(s)
- Ida A Mejias-Torres
- Department of Biochemistry, University of Puerto Rico School of Medicine, Medical Sciences Campus, San Juan, PR 00935, USA
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14
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Helmstaedt K, Krappmann S, Braus GH. Allosteric regulation of catalytic activity: Escherichia coli aspartate transcarbamoylase versus yeast chorismate mutase. Microbiol Mol Biol Rev 2001; 65:404-21, table of contents. [PMID: 11528003 PMCID: PMC99034 DOI: 10.1128/mmbr.65.3.404-421.2001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Allosteric regulation of key metabolic enzymes is a fascinating field to study the structure-function relationship of induced conformational changes of proteins. In this review we compare the principles of allosteric transitions of the complex classical model aspartate transcarbamoylase (ATCase) from Escherichia coli, consisting of 12 polypeptides, and the less complicated chorismate mutase derived from baker's yeast, which functions as a homodimer. Chorismate mutase presumably represents the minimal oligomerization state of a cooperative enzyme which still can be either activated or inhibited by different heterotropic effectors. Detailed knowledge of the number of possible quaternary states and a description of molecular triggers for conformational changes of model enzymes such as ATCase and chorismate mutase shed more and more light on allostery as an important regulatory mechanism of any living cell. The comparison of wild-type and engineered mutant enzymes reveals that current textbook models for regulation do not cover the entire picture needed to describe the function of these enzymes in detail.
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Affiliation(s)
- K Helmstaedt
- Abteilung Molekulare Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität, Grisebachstr. 8, D-37077 Göttingen, Germany
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15
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Wales ME, Madison LL, Glaser SS, Wild JR. Divergent allosteric patterns verify the regulatory paradigm for aspartate transcarbamylase. J Mol Biol 1999; 294:1387-400. [PMID: 10600393 DOI: 10.1006/jmbi.1999.3315] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The native Escherichia coli aspartate transcarbamoylase (ATCase, E.C. 2.1.3.2) provides a classic allosteric model for the feedback inhibition of a biosynthetic pathway by its end products. Both E. coli and Erwinia herbicola possess ATCase holoenzymes which are dodecameric (2(c3):3(r2)) with 311 amino acid residues per catalytic monomer and 153 and 154 amino acid residues per regulatory (r) monomer, respectively. While the quaternary structures of the two enzymes are identical, the primary amino acid sequences have diverged by 14 % in the catalytic polypeptide and 20 % in the regulatory polypeptide. The amino acids proposed to be directly involved in the active site and nucleotide binding site are strictly conserved between the two enzymes; nonetheless, the two enzymes differ in their catalytic and regulatory characteristics. The E. coli enzyme has sigmoidal substrate binding with activation by ATP, and inhibition by CTP, while the E. herbicola enzyme has apparent first order kinetics at low substrate concentrations in the absence of allosteric ligands, no ATP activation and only slight CTP inhibition. In an apparently important and highly conserved characteristic, CTP and UTP impose strong synergistic inhibition on both enzymes. The co-operative binding of aspartate in the E. coli enzyme is correlated with a T-to-R conformational transition which appears to be greatly reduced in the E. herbicola enzyme, although the addition of inhibitory heterotropic ligands (CTP or CTP+UTP) re-establishes co-operative saturation kinetics. Hybrid holoenzymes assembled in vivo with catalytic subunits from E. herbicola and regulatory subunits from E. coli mimick the allosteric response of the native E. coli holoenzyme and exhibit ATP activation. The reverse hybrid, regulatory subunits from E. herbicola and catalytic subunits from E. coli, exhibited no response to ATP. The conserved structure and diverged functional characteristics of the E. herbicola enzyme provides an opportunity for a new evaluation of the common paradigm involving allosteric control of ATCase.
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Affiliation(s)
- M E Wales
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
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16
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Turner GJ, Miercke LJ, Mitra AK, Stroud RM, Betlach MC, Winter-Vann A. Expression, purification, and structural characterization of the bacteriorhodopsin-aspartyl transcarbamylase fusion protein. Protein Expr Purif 1999; 17:324-38. [PMID: 10545282 DOI: 10.1006/prep.1999.1111] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We are testing a strategy for creating three-dimensional crystals of integral membrane proteins which involves the addition of a large soluble domain to the membrane protein to provide crystallization contacts. As a test of this strategy we designed a fusion between the membrane protein bacteriorhodopsin (BR) and the catalytic subunit of aspartyl transcarbamylase from Escherichia coli. The fusion protein (designated BRAT) was initially expressed in E. coli at 51 mg/liter of culture, to yield active aspartyl transcarbamylase and an unfolded bacterio-opsin (BO) component. In Halobacterium salinarum, BRAT was expressed at a yield of 7 mg/liter of culture and formed a high-density purple membrane. The visible absorption properties of BRAT were indistinguishable from those of BR, demonstrating that the fusion with aspartyl transcarbamylase had no effect on BR structure. Electron microscopy of BRAT membrane sheets showed that the fusion protein was trimeric and organized in a two-dimensional crystalline lattice similar to that in the BR purple membrane. Following solubilization and size-exclusion purification in sodium dodecyl sulfate, the BO portion of the fusion was quantitatively refolded in tetradecyl maltoside (TDM). Ultracentrifugation demonstrated that BR and BRAT-TDM mixed micelles had molecular masses of 138 and 162 kDa, respectively, with a stoichiometry of one protein per micelle. High TDM concentrations (>20 mM) were required to maintain BRAT solubility, hindering three-dimensional crystallization trials. We have demonstrated that BR can functionally accommodate massive C-terminal fusions and that these fusions may be expressed in quantities required for structural investigation in H. salinarum.
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Affiliation(s)
- G J Turner
- Department of Physiology & Biophysics, University of Miami School of Medicine, Miami, Florida, 33101, USA.
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17
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Durbecq V, Thia-Toong TL, Charlier D, Villeret V, Roovers M, Wattiez R, Legrain C, Glansdorff N. Aspartate carbamoyltransferase from the thermoacidophilic archaeon Sulfolobus acidocaldarius. Cloning, sequence analysis, enzyme purification and characterization. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:233-41. [PMID: 10447693 DOI: 10.1046/j.1432-1327.1999.00619.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The genes coding for aspartate carbamoyltransferase (ATCase) in the extremely thermophilic archaeon Sulfolobus acidocaldarius have been cloned by complementation of a pyrBI deletion mutant of Escherichia coli. Sequencing revealed the existence of an enterobacterial-like pyrBI operon encoding a catalytic chain of 299 amino acids (34 kDa) and a regulatory chain of 170 amino acids (17.9 kDa). The deduced amino acid sequences of the pyrB and pyrI genes showed 27.6-50% identity with archaeal and enterobacterial ATCases. The recombinant S. acidocaldarius ATCase was purified to homogeneity, allowing the first detailed studies of an ATCase isolated from a thermophilic organism. The recombinant enzyme displayed the same properties as the ATCase synthesized in the native host. It is highly thermostable and exhibits Michaelian saturation kinetics for carbamoylphosphate (CP) and positive homotropic cooperative interactions for the binding of L-aspartate. Moreover, it is activated by nucleoside triphosphates whereas the catalytic subunits alone are inhibited. The holoenzyme purified from recombinant E. coli cells or present in crude extract of the native host have an Mr of 340 000 as estimated by gel filtration, suggesting that it has a quaternary structure similar to that of E. coli ATCase. Only monomers could be found in extracts of recombinant E. coli or Saccharomyces cerevisiae cells expressing the pyrB gene alone. In the presence of CP these monomers assembled into trimers. The stability of S. acidocaldarius ATCase and the allosteric properties of the enzyme are discussed in function of a modeling study.
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Affiliation(s)
- V Durbecq
- Laboratoire de Microbiologie, Université de Libre de Bruxelles, Belgium
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18
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Beernink PT, Endrizzi JA, Alber T, Schachman HK. Assessment of the allosteric mechanism of aspartate transcarbamoylase based on the crystalline structure of the unregulated catalytic subunit. Proc Natl Acad Sci U S A 1999; 96:5388-93. [PMID: 10318893 PMCID: PMC21869 DOI: 10.1073/pnas.96.10.5388] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The lack of knowledge of the three-dimensional structure of the trimeric, catalytic (C) subunit of aspartate transcarbamoylase (ATCase) has impeded understanding of the allosteric regulation of this enzyme and left unresolved the mechanism by which the active, unregulated C trimers are inactivated on incorporation into the unliganded (taut or T state) holoenzyme. Surprisingly, the isolated C trimer, based on the 1.9-A crystal structure reported here, resembles more closely the trimers in the T state enzyme than in the holoenzyme:bisubstrate-analog complex, which has been considered as the active, relaxed (R) state enzyme. Unlike the C trimer in either the T state or bisubstrate-analog-bound holoenzyme, the isolated C trimer lacks 3-fold symmetry, and the active sites are partially disordered. The flexibility of the C trimer, contrasted to the highly constrained T state ATCase, suggests that regulation of the holoenzyme involves modulating the potential for conformational changes essential for catalysis. Large differences in structure between the active C trimer and the holoenzyme:bisubstrate-analog complex call into question the view that this complex represents the activated R state of ATCase.
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Affiliation(s)
- P T Beernink
- Department of Molecular and Cell Biology and Virus Laboratory, University of California, Berkeley, CA 94720-3206, USA
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19
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Ha Y, McCann MT, Tuchman M, Allewell NM. Substrate-induced conformational change in a trimeric ornithine transcarbamoylase. Proc Natl Acad Sci U S A 1997; 94:9550-5. [PMID: 9275160 PMCID: PMC23215 DOI: 10.1073/pnas.94.18.9550] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The crystal structure of Escherichia coli ornithine transcarbamoylase (OTCase, EC 2.1.3.3) complexed with the bisubstrate analog N-(phosphonacetyl)-L-ornithine (PALO) has been determined at 2.8-A resolution. This research on the structure of a transcarbamoylase catalytic trimer with a substrate analog bound provides new insights into the linkages between substrate binding, protein-protein interactions, and conformational change. The structure was solved by molecular replacement with the Pseudomonas aeruginosa catabolic OTCase catalytic trimer (Villeret, V., Tricot, C., Stalon, V. & Dideberg, O. (1995) Proc. Natl. Acad. Sci. USA 92, 10762-10766; Protein Data Bank reference pdb 1otc) as the model and refined to a crystallographic R value of 21.3%. Each polypeptide chain folds into two domains, a carbamoyl phosphate binding domain and an L-ornithine binding domain. The bound inhibitor interacts with the side chains and/or backbone atoms of Lys-53, Ser-55, Thr-56, Arg-57, Thr-58, Arg-106, His-133, Asn-167, Asp-231, Met-236, Leu-274, Arg-319 as well as Gln-82 and Lys-86 from an adjacent chain. Comparison with the unligated P. aeruginosa catabolic OTCase structure indicates that binding of the substrate analog results in closure of the two domains of each chain. As in E. coli aspartate transcarbamoylase, the 240s loop undergoes the largest conformational change upon substrate binding. The clinical implications for human OTCase deficiency are discussed.
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Affiliation(s)
- Y Ha
- Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul, MN 55108, USA
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20
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Jin L, Seaton BA, Head JF. Crystal structure at 2.8 A resolution of anabolic ornithine transcarbamylase from Escherichia coli. NATURE STRUCTURAL BIOLOGY 1997; 4:622-5. [PMID: 9253409 DOI: 10.1038/nsb0897-622] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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21
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Van de Casteele M, Chen P, Roovers M, Legrain C, Glansdorff N. Structure and expression of a pyrimidine gene cluster from the extreme thermophile Thermus strain ZO5. J Bacteriol 1997; 179:3470-81. [PMID: 9171389 PMCID: PMC179137 DOI: 10.1128/jb.179.11.3470-3481.1997] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
On a 4.7-kbp HindIII clone of Thermus strain ZO5 DNA, complementing an aspartate carbamoyltransferase mutation in Escherichia coli, we identified a cluster of four potential open reading frames corresponding to genes pyrR, and pyrB, an unidentified open reading frame named bbc, and gene pyrC. The transcription initiation site was mapped at about 115 nucleotides upstream of the pyrR translation start codon. The cognate Thermus pyr promoter also functions in heterologous expression of Thermus pyr genes in E. coli. In Thermus strain ZO5, pyrB and pyrC gene expression is repressed three- to fourfold by uracil and increased twofold by arginine. Based on the occurrence of several transcription signals in the Thermus pyr promoter region and strong amino acid sequence identities (about 60%) between Thermus PyrR and the PyrR attenuation proteins of two Bacillus sp., we propose a regulatory mechanism involving transcriptional attenuation to control pyr gene expression in Thermus. In contrast to pyr attenuation in Bacillus spp., however, control of the Thermus pyr gene cluster would not involve an antiterminator structure but would involve a translating ribosome for preventing formation of the terminator RNA hairpin. The deduced amino acid sequence of Thermus strain ZO5 aspartate carbamoyltransferase (ATCase; encoded by pyrB) exhibits the highest similarities (about 50% identical amino acids) with ATCases from Pseudomonas sp. For Thermus strain ZO5 dihydroorotase (DHOase; encoded by pyrC), the highest similarity scores (about 40% identity) were obtained with DHOases from B. caldolyticus and Bacillus subtilis. The enzyme properties of ATCase expressed from truncated versions of the Thermus pyr gene cluster in E. coli suggest that Thermus ATCase is stabilized by DHOase and that the translation product of bbc plays a role in feedback inhibition of the ATCase-DHOase complex.
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Affiliation(s)
- M Van de Casteele
- Department of Microbiology, Vlaams Interuniversitair Instituut voor Biotechnologie and Vrije Universiteit Brussel, Belgium
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22
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Bergh ST, Evans DR. Subunit structure of a class A aspartate transcarbamoylase from Pseudomonas fluorescens. Proc Natl Acad Sci U S A 1993; 90:9818-22. [PMID: 8234318 PMCID: PMC47663 DOI: 10.1073/pnas.90.21.9818] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The class A aspartate transcarbamoylase (ATCase, EC 2.1.3.2) from Pseudomonas fluorescens was purified to homogeneity with retention of full catalytic and regulatory functions. Careful determinations under conditions that minimized proteolysis showed that the molecule is a 1:1 stoichiometric complex of two polypeptide chains of 34 and 45 kDa. Pyridoxal phosphate is a competitive inhibitor of the enzyme (Ki = 1 microM). Reduction of the pyridoxal phosphate enzyme adduct with sodium boro[3H]hydride showed that the active site is located on the 34-kDa polypeptide. Affinity labeling with 5'-[p-(fluorosulfonyl)benzoyl]adenosine, an ATP analog, suggested that the regulatory site is also located on the 34-kDa species. While the function of the 45-kDa subunit is unknown, neither carbamoyl phosphate synthetase nor dihydroorotase activities are associated with the ATCase. The molecular mass of the enzyme was determined by gel filtration, sedimentation velocity, and electron microscopy to be 464 kDa. Thus the enzyme is composed of six copies of the 34-kDa polypeptide and six copies of the 45-kDa polypeptide. The molecule has a Stokes' ratio of 70.9 A and a frictional ratio of 1.37, suggesting a compact globular shape. We propose that the P. fluorescens ATCase is composed of two trimers of 34-kDa catalytic chains and is likely to be a D3 dodecamer with an arrangement of subunits analogous to that of the class B ATCase molecules.
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Affiliation(s)
- S T Bergh
- Department of Biochemistry, Wayne State University School of Medicine, Detroit, MI 48201
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23
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Baker DP, Kantrowitz ER. The conserved residues glutamate-37, aspartate-100, and arginine-269 are important for the structural stabilization of Escherichia coli aspartate transcarbamoylase. Biochemistry 1993; 32:10150-8. [PMID: 8104480 DOI: 10.1021/bi00089a034] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Aspartate transcarbamoylase from Escherichia coli is a dodecameric enzyme consisting of two trimeric catalytic subunits and three dimeric regulatory subunits. The X-ray structure of this enzyme indicates that the side chains of His-41, Asp-100, and Asp-90 from one catalytic chain form interactions with the side chains of Glu-37, Arg-65, and Arg-269, respectively, from an adjacent catalytic chain. In order to determine whether these interactions are important for the structural stabilization of the enzyme and/or homotropic and heterotropic effects, four mutant versions of aspartate transcarbamoylase, Glu-37-->Ala, Asp-100-->Asn, Asp-100-->Ala, and Arg-269-->Ala, were created by site-specific mutagenesis. The Glu-37-->Ala holoenzyme exhibits essentially wild-type behavior with respect to homotropic cooperativity and heterotropic regulation by ATP and CTP. The Glu-37-->Ala catalytic subunit exhibits a half-life of inactivation at 69 +/- 0.5 degrees C of 4.9 min, as compared to 5.8 min for the wild-type catalytic subunit. The Asp-100-->Asn and Asp-100-->Ala holoenzymes are slightly more active than the wild-type holoenzyme, exhibit 1.4-fold and 1.8-fold reductions in the aspartate concentration at half the maximal specific activity, respectively, and show increased affinities for ATP and CTP. Both the Asp-100-->Asn and Asp-100--> Ala catalytic subunits exhibit a 2-fold reduction in the half-life of inactivation at 69 +/- 0.5 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D P Baker
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02167
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24
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Stebbins JW, Robertson DE, Roberts MF, Stevens RC, Lipscomb WN, Kantrowitz ER. Arginine 54 in the active site of Escherichia coli aspartate transcarbamoylase is critical for catalysis: a site-specific mutagenesis, NMR, and X-ray crystallographic study. Protein Sci 1992; 1:1435-46. [PMID: 1303763 PMCID: PMC2142124 DOI: 10.1002/pro.5560011105] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The replacement of Arg-54 by Ala in the active site of Escherichia coli aspartate transcarbamoylase causes a 17,000-fold loss of activity but does not significantly influence the binding of substrates or substrate analogs (Stebbins, J.W., Xu, W., & Kantrowitz, E.R., 1989, Biochemistry 28, 2592-2600). In the X-ray structure of the wild-type enzyme, Arg-54 interacts with both the anhydride oxygen and a phosphate oxygen of carbamoyl phosphate (CP) (Gouaux, J.E. & Lipscomb, W.N., 1988, Proc. Natl. Acad. Sci. USA 85, 4205-4208). The Arg-54-->Ala enzyme was crystallized in the presence of the transition state analog N-phosphonacetyl-L-aspartate (PALA), data were collected to a resolution limit of 2.8 A, and the structure was solved by molecular replacement. The analysis of the refined structure (R factor = 0.18) indicates that the substitution did not cause any significant alterations to the active site, except that the side chain of the arginine was replaced by two water molecules. 31P-NMR studies indicate that the binding of CP to the wild-type catalytic subunit produces an upfield chemical shift that cannot reflect a significant change in the ionization state of the CP but rather indicates that there are perturbations in the electronic environment around the phosphate moiety when CP binds to the enzyme. The pH dependence of this upfield shift for bound CP indicates that the catalytic subunit undergoes a conformational change with a pKa approximately 7.7 upon CP binding. Furthermore, the linewidth of the 31P signal of CP bound to the Arg-54-->Ala enzyme is significantly narrower than that of CP bound to the wild-type catalytic subunit at any pH, although the change in chemical shift for the CP bound to the mutant enzyme is unaltered. 31P-NMR studies of PALA complexed to the wild-type catalytic subunit indicate that the phosphonate group of the bound PALA exists as the dianion at pH 7.0 and 8.8, whereas in the Arg-54-->Ala catalytic subunit the phosphonate group of the bound PALA exists as the monoanion at pH 7.0 and 8.8. Thus, the side chain of Arg-54 is essential for the proper ionization of the phosphonate group of PALA and by analogy the phosphate group in the transition state. These data support the previously proposed proton transfer mechanism, in which a fully ionized phosphate group in the transition state accepts a proton during catalysis.
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Affiliation(s)
- J W Stebbins
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02167
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