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Zhang JH, Wang S, Yang S, Yi J, Liu Y, Xi JH. DIFFERENTIAL PROTEOME ANALYSIS OF THE MALE AND FEMALE ANTENNAE FROM Holotrichia parallela. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2016; 92:274-287. [PMID: 27396371 DOI: 10.1002/arch.21338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
To understand the olfactory mechanisms of Holotrichia parallela antennae in detecting volatile compounds in the environment, protein profiles of H. parallela antennae were analyzed using two-dimensional electrophoresis followed by mass spectrometry and bioinformatics analyses. Approximately 1,100 protein spots in silver staining gel were detected. Quantitative image analysis revealed that in total 47 protein spots showed significant changes in different genders of adult antennae. Thirty-five differentially expressed proteins were identified by Matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF) tandem mass spectrometer, among which 65.7% are involved in carbohydrate and energy metabolism, antioxidant system, transport, and amino acid/nucleotide metabolism. Some proteins identified here have not been reported previously in insect antennae. Identified male-biased proteins included odorant-binding protein 4, pheromone-binding protein-related protein 2, odorant-binding protein 14, prophenoloxidase-I, acyl-CoA dehydrogenase, aldo-keto reductase-like, carbamoyl phosphate synthetase, etc. whereas some proteins are female biased, such as antennae-rich cytochrome P450, aldehyde dehydrogenase, and putative glutamine synthetase. Alterations in the levels of some proteins were further confirmed by real time polymerase chain reaction (RT-PCR). The proteomic resources displayed here are valuable for the discovery of proteins from H. parallela antennae.
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Affiliation(s)
- Ju-Hong Zhang
- College of Plant Science, Jilin University, ChangChun, P. R. China
| | - Shang Wang
- College of Plant Science, Jilin University, ChangChun, P. R. China
| | - Shuang Yang
- College of Plant Science, Jilin University, ChangChun, P. R. China
| | - Jiankun Yi
- College of Plant Science, Jilin University, ChangChun, P. R. China
| | - Yan Liu
- College of Plant Science, Jilin University, ChangChun, P. R. China
| | - Jing-Hui Xi
- College of Plant Science, Jilin University, ChangChun, P. R. China
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Müller R, Jenny A, Stanley P. The EGF repeat-specific O-GlcNAc-transferase Eogt interacts with notch signaling and pyrimidine metabolism pathways in Drosophila. PLoS One 2013; 8:e62835. [PMID: 23671640 PMCID: PMC3650022 DOI: 10.1371/journal.pone.0062835] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/26/2013] [Indexed: 11/18/2022] Open
Abstract
The O-GlcNAc transferase Eogt modifies EGF repeats in proteins that transit the secretory pathway, including Dumpy and Notch. In this paper, we show that the Notch ligands Delta and Serrate are also substrates of Eogt, that mutation of a putative UDP-GlcNAc binding DXD motif greatly reduces enzyme activity, and that Eogt and the cytoplasmic O-GlcNAc transferase Ogt have distinct substrates in Drosophila larvae. Loss of Eogt is larval lethal and disrupts Dumpy functions, but does not obviously perturb Notch signaling. To identify novel genetic interactions with eogt, we investigated dominant modification of wing blister formation caused by knock-down of eogt. Unexpectedly, heterozygosity for several members of the canonical Notch signaling pathway suppressed wing blister formation. And importantly, extensive genetic interactions with mutants in pyrimidine metabolism were identified. Removal of pyrimidine synthesis alleles suppressed wing blister formation, while removal of uracil catabolism alleles was synthetic lethal with eogt knock-down. Therefore, Eogt may regulate protein functions by O-GlcNAc modification of their EGF repeats, and cellular metabolism by affecting pyrimidine synthesis and catabolism. We propose that eogt knock-down in the wing leads to metabolic and signaling perturbations that increase cytosolic uracil levels, thereby causing wing blister formation.
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Affiliation(s)
- Reto Müller
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Andreas Jenny
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, United States of America
- Department of Genetics, Albert Einstein College of Medicine, New York, New York, United States of America
- * E-mail: (AJ); (PS)
| | - Pamela Stanley
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York, United States of America
- * E-mail: (AJ); (PS)
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Divergent functions through alternative splicing: the Drosophila CRMP gene in pyrimidine metabolism, brain, and behavior. Genetics 2012; 191:1227-38. [PMID: 22649077 DOI: 10.1534/genetics.112.141101] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
DHP and CRMP proteins comprise a family of structurally similar proteins that perform divergent functions, DHP in pyrimidine catabolism in most organisms and CRMP in neuronal dynamics in animals. In vertebrates, one DHP and five CRMP proteins are products of six genes; however, Drosophila melanogaster has a single CRMP gene that encodes one DHP and one CRMP protein through tissue-specific, alternative splicing of a pair of paralogous exons. The proteins derived from the fly gene are identical over 90% of their lengths, suggesting that unique, novel functions of these proteins derive from the segment corresponding to the paralogous exons. Functional homologies of the Drosophila and mammalian CRMP proteins are revealed by several types of evidence. Loss-of-function CRMP mutation modifies both Ras and Rac misexpression phenotypes during fly eye development in a manner that is consistent with the roles of CRMP in Ras and Rac signaling pathways in mammalian neurons. In both mice and flies, CRMP mutation impairs learning and memory. CRMP mutant flies are defective in circadian activity rhythm. Thus, DHP and CRMP proteins are derived by different processes in flies (tissue-specific, alternative splicing of paralogous exons of a single gene) and vertebrates (tissue-specific expression of different genes), indicating that diverse genetic mechanisms have mediated the evolution of this protein family in animals.
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Bonavia A, Franti M, Pusateri Keaney E, Kuhen K, Seepersaud M, Radetich B, Shao J, Honda A, Dewhurst J, Balabanis K, Monroe J, Wolff K, Osborne C, Lanieri L, Hoffmaster K, Amin J, Markovits J, Broome M, Skuba E, Cornella-Taracido I, Joberty G, Bouwmeester T, Hamann L, Tallarico JA, Tommasi R, Compton T, Bushell SM. Identification of broad-spectrum antiviral compounds and assessment of the druggability of their target for efficacy against respiratory syncytial virus (RSV). Proc Natl Acad Sci U S A 2011; 108:6739-44. [PMID: 21502533 PMCID: PMC3084118 DOI: 10.1073/pnas.1017142108] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The search for novel therapeutic interventions for viral disease is a challenging pursuit, hallmarked by the paucity of antiviral agents currently prescribed. Targeting of viral proteins has the inextricable challenge of rise of resistance. Safe and effective vaccines are not possible for many viral pathogens. New approaches are required to address the unmet medical need in this area. We undertook a cell-based high-throughput screen to identify leads for development of drugs to treat respiratory syncytial virus (RSV), a serious pediatric pathogen. We identified compounds that are potent (nanomolar) inhibitors of RSV in vitro in HEp-2 cells and in primary human bronchial epithelial cells and were shown to act postentry. Interestingly, two scaffolds exhibited broad-spectrum activity among multiple RNA viruses. Using the chemical matter as a probe, we identified the targets and identified a common cellular pathway: the de novo pyrimidine biosynthesis pathway. Both targets were validated in vitro and showed no significant cell cytotoxicity except for activity against proliferative B- and T-type lymphoid cells. Corollary to this finding was to understand the consequences of inhibition of the target to the host. An in vivo assessment for antiviral efficacy failed to demonstrate reduced viral load, but revealed microscopic changes and a trend toward reduced pyrimidine pools and findings in histopathology. We present here a discovery program that includes screen, target identification, validation, and druggability that can be broadly applied to identify and interrogate other host factors for antiviral effect starting from chemical matter of unknown target/mechanism of action.
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Affiliation(s)
- Aurelio Bonavia
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Michael Franti
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Erin Pusateri Keaney
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Kelli Kuhen
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Mohindra Seepersaud
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Branko Radetich
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Jian Shao
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Ayako Honda
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Janetta Dewhurst
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Kara Balabanis
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - James Monroe
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Karen Wolff
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Colin Osborne
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Leanne Lanieri
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Keith Hoffmaster
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Jakal Amin
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Judit Markovits
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Michelle Broome
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Elizabeth Skuba
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Ivan Cornella-Taracido
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Gerard Joberty
- Cellzome AG, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Tewis Bouwmeester
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Lawrence Hamann
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - John A. Tallarico
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Ruben Tommasi
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Teresa Compton
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
| | - Simon M. Bushell
- Novartis Institutes for Biomedical Research, Inc., 250 Massachusetts Avenue, Cambridge, MA 02139; and
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Caldara M, Charlier D, Cunin R. The arginine regulon of Escherichia coli: whole-system transcriptome analysis discovers new genes and provides an integrated view of arginine regulation. MICROBIOLOGY-SGM 2007; 152:3343-3354. [PMID: 17074904 DOI: 10.1099/mic.0.29088-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Analysis of the response to arginine of the Escherichia coli K-12 transcriptome by microarray hybridization and real-time quantitative PCR provides the first coherent quantitative picture of the ArgR-mediated repression of arginine biosynthesis and uptake genes. Transcriptional repression was shown to be the major control mechanism of the biosynthetic genes, leaving only limited room for additional transcriptional or post-transcriptional regulation. The art genes, encoding the specific arginine uptake system, are subject to ArgR-mediated repression, with strong repression of artJ, encoding the periplasmic binding protein of the system. The hisJQMP genes of the histidine transporter (part of the lysine-arginine-ornithine uptake system) were discovered to be a part of the arginine regulon. Analysis of their control region with reporter gene fusions and electrophoretic mobility shift in the presence of pure ArgR repressor showed the involvement in repression of the ArgR protein and an ARG box 120 bp upstream of hisJ. No repression of the genes of the third uptake system, arginine-ornithine, was observed. Finally, comparison of the time course of arginine repression of gene transcription with the evolution of the specific activities of the cognate enzymes showed that while full genetic repression was achieved 2 min after arginine addition, enzyme concentrations were diluted at the rate of cell division. This emphasizes the importance of feedback inhibition of the first enzymic step in the pathway in controlling the metabolic flow through biosynthesis in the period following the onset of repression.
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Affiliation(s)
- Marina Caldara
- Laboratorium voor Erfelijkheidsleer en Microbiologie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Daniel Charlier
- Laboratorium voor Erfelijkheidsleer en Microbiologie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Raymond Cunin
- Laboratorium voor Erfelijkheidsleer en Microbiologie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
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Rawls JM. Analysis of pyrimidine catabolism in Drosophila melanogaster using epistatic interactions with mutations of pyrimidine biosynthesis and beta-alanine metabolism. Genetics 2005; 172:1665-74. [PMID: 16361227 PMCID: PMC1456268 DOI: 10.1534/genetics.105.052753] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The biochemical pathway for pyrimidine catabolism links the pathways for pyrimidine biosynthesis and salvage with beta-alanine metabolism, providing an array of epistatic interactions with which to analyze mutations of these pathways. Loss-of-function mutations have been identified and characterized for each of the enzymes for pyrimidine catabolism: dihydropyrimidine dehydrogenase (DPD), su(r) mutants; dihydropyrimidinase (DHP), CRMP mutants; beta-alanine synthase (betaAS), pyd3 mutants. For all three genes, mutants are viable and fertile and manifest no obvious phenotypes, aside from a variety of epistatic interactions. Mutations of all three genes disrupt suppression by the rudimentary gain-of-function mutation (r(Su(b))) of the dark cuticle phenotype of black mutants in which beta-alanine pools are diminished; these results confirm that pyrimidines are the major source of beta-alanine in cuticle pigmentation. The truncated wing phenotype of rudimentary mutants is suppressed completely by su(r) mutations and partially by CRMP mutations; however, no suppression is exhibited by pyd3 mutations. Similarly, su(r) mutants are hypersensitive to dietary 5-fluorouracil, CRMP mutants are less sensitive, and pyd3 mutants exhibit wild-type sensitivity. These results are discussed in the context of similar consequences of 5-fluoropyrimidine toxicity and pyrimidine catabolism mutations in humans.
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Affiliation(s)
- John M Rawls
- Molecular and Cellular Biology Group, Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA.
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Schröder M, Giermann N, Zrenner R. Functional analysis of the pyrimidine de novo synthesis pathway in solanaceous species. PLANT PHYSIOLOGY 2005; 138:1926-38. [PMID: 16024685 PMCID: PMC1183384 DOI: 10.1104/pp.105.063693] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/14/2005] [Accepted: 05/16/2005] [Indexed: 05/03/2023]
Abstract
Pyrimidines are particularly important in dividing tissues as building blocks for nucleic acids, but they are equally important for many biochemical processes, including sucrose and cell wall polysaccharide metabolism. In recent years, the molecular organization of nucleotide biosynthesis in plants has been analyzed. Here, we present a functional analysis of the pyrimidine de novo synthesis pathway. Each step in the pathway was investigated using transgenic plants with reduced expression of the corresponding gene to identify controlling steps and gain insights into the phenotypic and metabolic consequences. Inhibition of expression of 80% based on steady-state mRNA level did not lead to visible phenotypes. Stepwise reduction of protein abundance of Asp transcarbamoylase or dihydro orotase resulted in a corresponding inhibition of growth. This was not accompanied by pleiotropic effects or by changes in the developmental program. A more detailed metabolite analysis revealed slightly different responses in roots and shoots of plants with decreased abundance of proteins involved in pyrimidine de novo synthesis. Whereas in leaves the nucleotide and amino acid levels were changed only in the very strong inhibited plants, the roots show a transient increase of these metabolites in intermediate plants followed by a decrease in the strong inhibited plants. Growth analysis revealed that elongation rates and number of organs per plant were reduced, without large changes in the average cell size. It is concluded that reduced pyrimidine de novo synthesis is compensated for by reduction in growth rates, and the remaining nucleotide pools are sufficient for running basic metabolic processes.
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Affiliation(s)
- Michael Schröder
- Botanisches Institut, Im Neuenheimer Feld 360, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg, Germany
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Simmons CQ, Simmons AJ, Haubner A, Ream A, Davidson JN. Substitutions in hamster CAD carbamoyl-phosphate synthetase alter allosteric response to 5-phosphoribosyl-alpha-pyrophosphate (PRPP) and UTP. Biochem J 2004; 378:991-8. [PMID: 14651476 PMCID: PMC1224011 DOI: 10.1042/bj20031228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2003] [Revised: 12/02/2003] [Accepted: 12/03/2003] [Indexed: 11/17/2022]
Abstract
CPSase (carbamoyl-phosphate synthetase II), a component of CAD protein (multienzymic protein with CPSase, aspartate transcarbamylase and dihydro-orotase activities), catalyses the regulated steps in the de novo synthesis of pyrimidines. Unlike the orthologous Escherichia coli enzyme that is regulated by UMP, inosine monophosphate and ornithine, the mammalian CPSase is allosterically inhibited by UTP, and activated by PRPP (5-phosphoribosyl-a-pyrophosphate) and phosphorylation. Four residues (Thr974, Lys993, Lys954 and Thr977) are critical to the E. coli inosine monophosphate/UMP-binding pocket. In the present study, three of the corresponding residues in the hamster CPSase were altered to determine if they affect either PRPP activation or UTP inhibition. Substitution of the hamster residue, positionally equivalent to Thr974 in the E. coli enzyme, with alanine residue led to an enzyme with 5-fold lower activity and a near loss of PRPP activation. Whereas replacement of the tryptophan residue at position 993 had no effect, an Asp992-->Asn substitution yielded a much-activated enzyme that behaved as if PRPP was present. The substitution Lys954-->Glu had no effect on PRPP stimulation. Only modest decreases in UTP inhibitions were observed with each of the altered CPSases. The results also show that while PRPP and UTP can act simultaneously, PRPP activation is dominant. Apparently, UTP and PRPP have distinctly different associations within the mammalian enzyme. The findings of the present study may prove relevant to the neuropathology of Lesch-Nyhan syndrome
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Affiliation(s)
- Christine Q Simmons
- Department of Microbiology, Immunology and Molecular Genetics, Albert B. Chandler Medical Center and Lucille P. Markey Cancer Center, University of Kentucky, Lexington, KY 40536-0293, USA
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Evans DR, Guy HI. Mammalian pyrimidine biosynthesis: fresh insights into an ancient pathway. J Biol Chem 2004; 279:33035-8. [PMID: 15096496 DOI: 10.1074/jbc.r400007200] [Citation(s) in RCA: 291] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- David R Evans
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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Löffler M, Knecht W, Rawls J, Ullrich A, Dietz C. Drosophila melanogaster dihydroorotate dehydrogenase: the N-terminus is important for biological function in vivo but not for catalytic properties in vitro. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2002; 32:1159-1169. [PMID: 12213251 DOI: 10.1016/s0965-1748(02)00052-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Dihydroorotate dehydrogenase (DHODH, EC 1.3.99.11), the fourth enzyme of pyrimidine de novo synthesis, is an integral flavoprotein of the inner mitchondrial membrane and is functionally connected to the respiratory chain. Here, experiments have been directed toward determining the roles of the N-terminal sequence motifs both in enzymatic properties of insect DHODH produced in vitro and the in vivo function of the protein. Full-length and three N-terminal truncated derivatives of the Drosophila melanogaster enzyme were expressed in Escherichia coli and purified. For identification on Western blots of recombinant DHODH as well as the native enzyme from flies polyclonal anti-DHODH immunoglobulins were generated and affinity-purified. The enzymatic characteristics of the four versions of DHODH were very similar, indicating that the N-terminus of the enzyme does not influence its catalytic function or its susceptibility to prominent DHODH inhibitors: A77-1726, brequinar, dichloroallyl-lawsone and redoxal. Whereas the efficacy of A77-1726 and dichloroallyl-lawsone were similar with Drosophila and human DHODH, that of brequinar and redoxal differed significantly. The differences in responses of insect DHODH and the enzyme from other species may allow the design of new agents that will selectively control insect growth, due to pyrimidine nucleotide limitation. In vivo expression of the full-length and N-truncated DHODHs from engineered transgenes revealed that the truncated proteins could not support normal de novo pyrimidine biosynthesis during development of the fly (i.e., failure to complement dhod-null mutations), apparently due to instability of the truncated proteins. It is concluded that the proper intracellular localization, directed by the N-terminal targeting and transmembrane motifs, is required for stability and subsequent proper biological function in vivo.
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Affiliation(s)
- Monika Löffler
- Institute for Physiological Chemistry, Philipps-University Marburg, Karl-von-Frisch-Str. 1, D-35033 Marburg, Germany.
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Benoist P, Feau P, Pliss A, Vorisek J, Antonelli R, Raska I, Denis-Duphil M. The yeast Ura2 protein that catalyses the first two steps of pyrimidines biosynthesis accumulates not in the nucleus but in the cytoplasm, as shown by immunocytochemistry and Ura2-green fluorescent protein mapping. Yeast 2000; 16:1299-312. [PMID: 11015727 DOI: 10.1002/1097-0061(200010)16:14<1299::aid-yea593>3.0.co;2-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Ura2 multidomain protein catalyses the first two steps of pyrimidines biosynthesis in Saccharomyces cerevisiae. It consists of a 240 kDa polypeptide which contains carbamyl phosphate synthetase and aspartate transcarbamylase domains. The Ura2 protein was believed to be nucleoplasmic, since one of the aspartate transcarbamylase reaction products, monophosphate, was reported to be precipitated by lead ions inside nuclei. However, this ultracytochemical approach was recently shown to give artifactual lead polyphosphate precipitates, and the use of cerium instead of lead failed to reveal this nucleoplasmic localization. Ura2 localization has therefore been undertaken by means of three alternative approaches based on the detection of the protein itself: (a) indirect immunofluorescence of yeast protoplasts; (b) immunogold labelling of ultrathin sections of embedded yeast cells (both approaches using affinity purified primary antibodies directed against the 240 kDa Ura2 polypeptide chain, or against a 22 residue peptide specific of the carbamyl phosphate synthetase domain); and (c) direct fluorescence of cells expressing an Ura2-green fluorescent protein hybrid. All three approaches localize the bulk of Ura2 to the cytoplasm, whereas the signals associated with the nucleus, mitochondria or vacuoles are close to or at the background level.
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Affiliation(s)
- P Benoist
- Instituto de Investigaciones Biomédicas, C.S.I.C, 4, Arturo Duperier, ES-28029 Madrid, Spain
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Qiu Y, Davidson JN. Substitutions in the aspartate transcarbamoylase domain of hamster CAD disrupt oligomeric structure. Proc Natl Acad Sci U S A 2000; 97:97-102. [PMID: 10618377 PMCID: PMC26622 DOI: 10.1073/pnas.97.1.97] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aspartate transcarbamoylase (ATCase; EC 2.1.3.2) is one of three enzymatic domains of CAD, a protein whose native structure is usually a hexamer of identical subunits. Alanine substitutions for the ATCase residues Asp-90 and Arg-269 were generated in a bicistronic vector that encodes a 6-histidine-tagged hamster CAD. Stably transfected mammalian cells expressing high levels of CAD were easily isolated and CAD purification was simplified over previous procedures. The substitutions reduce the ATCase V(max) of the altered CADs by 11-fold and 46-fold, respectively, as well as affect the enzyme's affinity for aspartate. At 25 mM Mg(2+), these substitutions cause the oligomeric CAD to dissociate into monomers. Under the same dissociating conditions, incubating the altered CAD with the ATCase substrate carbamoyl phosphate or the bisubstrate analogue N-phosphonacetyl-L-aspartate unexpectedly leads to the reformation of hexamers. Incubation with the other ATCase substrate, aspartate, has no effect. These results demonstrate that the ATCase domain is central to hexamer formation in CAD and suggest that the ATCase reaction mechanism is ordered in the same manner as the Escherichia coli ATCase. Finally, the data indicate that the binding of carbamoyl phosphate induces conformational changes that enhance the interaction of CAD subunits.
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Affiliation(s)
- Y Qiu
- Department of Microbiology, Albert B. Chandler Medical Center, University of Kentucky, Lexington, KY 40536-0084, USA
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