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Abstract
Protein prenylation, like other lipid posttranslational modifications of eukaryotic proteins, plays important roles in protein-membrane association and protein-protein interactions. In Arabidopsis, hundreds of proteins involved in a great variety of biological processes are potential prenylation substrates that need to be verified, including heterotrimeric G proteins and most Rop and Rab small GTPases. Also, genetic evidence suggests substrate cross-specificity among different prenyltransferases and/or the existence of unidentified prenylation players. In this chapter we describe a direct and flexible in vitro enzymatic assay designed for testing prenylation activity and substrate specificity in vitro. This protocol takes Arabidopsis Rab-GGT as example and starts with preparation of purified protein components of the reaction, followed by reconstitution of the prenylation reaction in vitro, and autoradiographic detection for qualitative and semiquantitative analysis.
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Affiliation(s)
- Wan Shi
- Washington University in Saint Louis, St. Louis, MO, USA
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2
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Posttranslational Modifications of Plasma Membrane Proteins and Their Implications for Plant Growth and Development. THE PLANT PLASMA MEMBRANE 2011. [DOI: 10.1007/978-3-642-13431-9_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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3
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Lan P, Li W, Wang H, Ma W. Characterization, sub-cellular localization and expression profiling of the isoprenylcysteine methylesterase gene family in Arabidopsis thaliana. BMC PLANT BIOLOGY 2010; 10:212. [PMID: 20868530 PMCID: PMC3017835 DOI: 10.1186/1471-2229-10-212] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 09/27/2010] [Indexed: 05/25/2023]
Abstract
BACKGROUND Isoprenylcysteine methylesterases (ICME) demethylate prenylated protein in eukaryotic cell. Until now, knowledge about their molecular information, localization and expression pattern is largely unavailable in plant species. One ICME in Arabidopsis, encoded by At5g15860, has been identified recently. Over-expression of At5g15860 caused an ABA hypersensitive phenotype in transgenic Arabidopsis plants, indicating that it functions as a positive regulator of ABA signaling. Moreover, ABA induced the expression of this gene in Arabidopsis seedlings. The current study extends these findings by examining the sub-cellular localization, expression profiling, and physiological functions of ICME and two other ICME-like proteins, ICME-LIKE1 and ICME-LIKE2, which were encoded by two related genes At1g26120 and At3g02410, respectively. RESULTS Bioinformatics investigations showed that the ICME and other two ICME-like homologs comprise a small subfamily of carboxylesterase (EC 3.1.1.1) in Arabidopsis. Sub-cellular localization of GFP tagged ICME and its homologs showed that the ICME and ICME-like proteins are intramembrane proteins predominantly localizing in the endoplasmic reticulum (ER) and Golgi apparatus. Semi-quantitative and real-time quantitative PCR revealed that the ICME and ICME-like genes are expressed in all examined tissues, including roots, rosette leaves, cauline leaves, stems, flowers, and siliques, with differential expression levels. Within the gene family, the base transcript abundance of ICME-LIKE2 gene is very low with higher expression in reproductive organs (flowers and siliques). Time-course analysis uncovered that both ICME and ICME-like genes are up-regulated by mannitol, NaCl and ABA treatment, with ICME showing the highest level of up-regulation by these treatments. Heat stress resulted in up-regulation of the ICME gene significantly but down-regulation of the ICME-LIKE1 and ICME-LIKE2 genes. Cold and dehydration stimuli led to no significant change of both ICME and ICME-like gene expression. Mutant icme-like2-1 showed increased sensitivity to ABA but slightly decreased sensitivity to salt and osmotic stresses during seed germination. CONCLUSIONS It is concluded that the ICME family is involved in stress and ABA signaling in Arabidopsis, probably through mediating the process of demethylating prenylated proteins. Identification of these prenylated proteins will help to better understand the significance of protein prenylation in Planta.
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Affiliation(s)
- Ping Lan
- State Agricultural Biotechnology Centre, Murdoch University; & Western Australian Department of Agriculture & Food; Murdoch, WA 6150, Australia
| | - Wenfeng Li
- State Agricultural Biotechnology Centre, Murdoch University; & Western Australian Department of Agriculture & Food; Murdoch, WA 6150, Australia
| | - Huizhong Wang
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 310036, China
| | - Wujun Ma
- State Agricultural Biotechnology Centre, Murdoch University; & Western Australian Department of Agriculture & Food; Murdoch, WA 6150, Australia
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4
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Andrews M, Huizinga DH, Crowell DN. The CaaX specificities of Arabidopsis protein prenyltransferases explain era1 and ggb phenotypes. BMC PLANT BIOLOGY 2010; 10:118. [PMID: 20565889 PMCID: PMC3017772 DOI: 10.1186/1471-2229-10-118] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 06/18/2010] [Indexed: 05/20/2023]
Abstract
BACKGROUND Protein prenylation is a common post-translational modification in metazoans, protozoans, fungi, and plants. This modification, which mediates protein-membrane and protein-protein interactions, is characterized by the covalent attachment of a fifteen-carbon farnesyl or twenty-carbon geranylgeranyl group to the cysteine residue of a carboxyl terminal CaaX motif. In Arabidopsis, era1 mutants lacking protein farnesyltransferase exhibit enlarged meristems, supernumerary floral organs, an enhanced response to abscisic acid (ABA), and drought tolerance. In contrast, ggb mutants lacking protein geranylgeranyltransferase type 1 exhibit subtle changes in ABA and auxin responsiveness, but develop normally. RESULTS We have expressed recombinant Arabidopsis protein farnesyltransferase (PFT) and protein geranylgeranyltransferase type 1 (PGGT1) in E. coli and characterized purified enzymes with respect to kinetic constants and substrate specificities. Our results indicate that, whereas PFT exhibits little specificity for the terminal amino acid of the CaaX motif, PGGT1 exclusively prenylates CaaX proteins with a leucine in the terminal position. Moreover, we found that different substrates exhibit similar K(m) but different k(cat) values in the presence of PFT and PGGT1, indicating that substrate specificities are determined primarily by reactivity rather than binding affinity. CONCLUSIONS The data presented here potentially explain the relatively strong phenotype of era1 mutants and weak phenotype of ggb mutants. Specifically, the substrate specificities of PFT and PGGT1 suggest that PFT can compensate for loss of PGGT1 in ggb mutants more effectively than PGGT1 can compensate for loss of PFT in era1 mutants. Moreover, our results indicate that PFT and PGGT1 substrate specificities are primarily due to differences in catalysis, rather than differences in substrate binding.
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Affiliation(s)
- Michelle Andrews
- Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA
| | - David H Huizinga
- Department of Biology, Indiana University-Purdue University, Indianapolis, IN 46202, USA
- Dow AgroSciences LLC, Indianapolis, IN 46268, USA
| | - Dring N Crowell
- Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA
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5
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Huizinga DH, Omosegbon O, Omery B, Crowell DN. Isoprenylcysteine methylation and demethylation regulate abscisic acid signaling in Arabidopsis. THE PLANT CELL 2008; 20:2714-28. [PMID: 18957507 PMCID: PMC2590716 DOI: 10.1105/tpc.107.053389] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Isoprenylated proteins bear an isoprenylcysteine methyl ester at the C terminus. Although isoprenylated proteins have been implicated in meristem development and negative regulation of abscisic acid (ABA) signaling, the functional role of the terminal methyl group has not been described. Here, we show that transgenic Arabidopsis thaliana plants overproducing isoprenylcysteine methyltransferase (ICMT) exhibit ABA insensitivity in stomatal closure and seed germination assays, establishing ICMT as a negative regulator of ABA signaling. By contrast, transgenic plants overproducing isoprenylcysteine methylesterase (ICME) exhibit ABA hypersensitivity in stomatal closure and seed germination assays. Thus, ICME is a positive regulator of ABA signaling. To test the hypothesis that ABA signaling is under feedback regulation at the level of isoprenylcysteine methylation, we examined the effect of ABA on ICMT and ICME gene expression. Interestingly, ABA induces ICME gene expression, establishing a positive feedback loop whereby ABA promotes ABA responsiveness of plant cells via induction of ICME expression, which presumably results in the demethylation and inactivation of isoprenylated negative regulators of ABA signaling. These results suggest strategies for metabolic engineering of crop species for drought tolerance by targeted alterations in isoprenylcysteine methylation.
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Affiliation(s)
- David H Huizinga
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202-5132, USA
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6
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Overy DP, Larsen TO, Dalsgaard PW, Frydenvang K, Phipps R, Munro MHG, Christophersen C. Andrastin A and barceloneic acid metabolites, protein farnesyl transferase inhibitors from Penicillium albocoremium: chemotaxonomic significance and pathological implications. ACTA ACUST UNITED AC 2005; 109:1243-9. [PMID: 16279417 DOI: 10.1017/s0953756205003734] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A survey of Penicillium albocoremium was undertaken to identify potential taxonomic metabolite markers. One major and four minor metabolites were consistently produced by the 19 strains surveyed on three different media. Following purification and spectral studies, the metabolites were identified as the known protein farnesyl transferase inhibitors andrastin A (1) and barceloneic acid A (2) along with barceloneic acid B (3), barceloneic lactone (4), and methyl barceloneate (5). These compounds are significant taxonomic markers for P. albocoremium; moreover this is the first report of a methyl ester of a barceloneic acid being produced as a secondary metabolite. Tissue extracts created following pathogenicity trials involving P. albocoremium and Allium cepa confirmed the production of these five metabolites in planta. Barceloneic acid B was found to be biologically active against a P388 murine leukemia cell line.
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Affiliation(s)
- David P Overy
- Centre for Microbial Biotechnology, Biocentrum-DTU, Technical University of Denmark, Kgs Lyngby, Denmark.
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7
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Johnson CD, Chary SN, Chernoff EA, Zeng Q, Running MP, Crowell DN. Protein geranylgeranyltransferase I is involved in specific aspects of abscisic acid and auxin signaling in Arabidopsis. PLANT PHYSIOLOGY 2005; 139:722-33. [PMID: 16183844 PMCID: PMC1255991 DOI: 10.1104/pp.105.065045] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Arabidopsis (Arabidopsis thaliana) mutants lacking a functional ERA1 gene, which encodes the beta-subunit of protein farnesyltransferase (PFT), exhibit pleiotropic effects that establish roles for protein prenylation in abscisic acid (ABA) signaling and meristem development. Here, we report the effects of T-DNA insertion mutations in the Arabidopsis GGB gene, which encodes the beta-subunit of protein geranylgeranyltransferase type I (PGGT I). Stomatal apertures of ggb plants were smaller than those of wild-type plants at all concentrations of ABA tested, suggesting that PGGT I negatively regulates ABA signaling in guard cells. However, germination of ggb seeds in response to ABA was similar to the wild type. Lateral root formation in response to exogenous auxin was increased in ggb seedlings compared to the wild type, but no change in auxin inhibition of primary root growth was observed, suggesting that PGGT I is specifically involved in negative regulation of auxin-induced lateral root initiation. Unlike era1 mutants, ggb mutants exhibited no obvious developmental phenotypes. However, era1 ggb double mutants exhibited more severe developmental phenotypes than era1 mutants and were indistinguishable from plp mutants lacking the shared alpha-subunit of PFT and PGGT I. Furthermore, overexpression of GGB in transgenic era1 plants partially suppressed the era1 phenotype, suggesting that the relatively weak phenotype of era1 plants is due to partial redundancy between PFT and PGGT I. These results are discussed in the context of Arabidopsis proteins that are putative substrates of PGGT I.
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Affiliation(s)
- Cynthia D Johnson
- Department of Biology, Indiana University-Purdue University, Indianapolis, 46202-5132, USA
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8
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Courdavault V, Thiersault M, Courtois M, Gantet P, Oudin A, Doireau P, St-Pierre B, Giglioli-Guivarc'h N. CaaX-prenyltransferases are essential for expression of genes involvedin the early stages of monoterpenoid biosynthetic pathway in Catharanthus roseus cells. PLANT MOLECULAR BIOLOGY 2005; 57:855-70. [PMID: 15952070 DOI: 10.1007/s11103-005-3095-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Accepted: 03/03/2005] [Indexed: 05/02/2023]
Abstract
CaaX-prenyltransferases (CaaX-PTases) catalyse the covalent attachment of isoprenyl groups to conserved cysteine residues located at the C-terminal CaaX motif of a protein substrate. This post-translational modification is required for the function and/or subcellular localization of some transcription factors and components of signal transduction and membrane trafficking machinery. CaaX-PTases, including protein farnesyltransferase (PFT) and type-I protein geranylgeranyltransferase (PGGT-I), are heterodimeric enzymes composed of a common alpha subunit and a specific beta subunit. We have established RNA interference cell lines targeting the beta subunits of PFT and PGGT-I, respectively, in the Catharanthus roseus C20D cell line, which synthesizes monoterpenoid indole alkaloids in response to auxin depletion from the culture medium. In both types of RNAi cell lines, expression of a subset of genes involved in the early stage of monoterpenoid biosynthetic pathway (ESMB genes), including the MEP pathway, is strongly decreased. The role of CaaX-PTases in ESMB gene regulation was confirmed by using the general prenyltransferase inhibitor s-perillyl alcohol (SP) and the specific PFT inhibitor Manumycin A on the wild type line. Furthermore, supplementation of SP inhibited cells with monoterpenoid intermediates downstream of the steps encoded by the ESMB genes restores monoterpenoid indole alkaloids biosynthesis. We conclude that protein targets for both PFT and PGGT-I are required for the expression of ESMB genes and monoterpenoid biosynthesis in C. roseus, this represents a non previously described role for protein prenyltransferase in plants.
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Affiliation(s)
- Vincent Courdavault
- Biomolecules et Biotechnologies Vegetales, Labaratoire de Physiologie Vegetale, UFR Science et Techniques, Universite Francois-Rabelais de Tours, EA2106, 37200 , Parc de Grandmont, Tours, France
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9
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Courdavault V, Thiersault M, Courtois M, Gantet P, Oudin A, Doireau P, St-Pierre B, Giglioli-Guivarc'h N. CaaX-prenyltransferases are essential for expression of genes involvedin the early stages of monoterpenoid biosynthetic pathway in Catharanthus roseus cells. PLANT MOLECULAR BIOLOGY 2005. [PMID: 15952070 DOI: 10.1016/j.plantsci.2004.12.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
CaaX-prenyltransferases (CaaX-PTases) catalyse the covalent attachment of isoprenyl groups to conserved cysteine residues located at the C-terminal CaaX motif of a protein substrate. This post-translational modification is required for the function and/or subcellular localization of some transcription factors and components of signal transduction and membrane trafficking machinery. CaaX-PTases, including protein farnesyltransferase (PFT) and type-I protein geranylgeranyltransferase (PGGT-I), are heterodimeric enzymes composed of a common alpha subunit and a specific beta subunit. We have established RNA interference cell lines targeting the beta subunits of PFT and PGGT-I, respectively, in the Catharanthus roseus C20D cell line, which synthesizes monoterpenoid indole alkaloids in response to auxin depletion from the culture medium. In both types of RNAi cell lines, expression of a subset of genes involved in the early stage of monoterpenoid biosynthetic pathway (ESMB genes), including the MEP pathway, is strongly decreased. The role of CaaX-PTases in ESMB gene regulation was confirmed by using the general prenyltransferase inhibitor s-perillyl alcohol (SP) and the specific PFT inhibitor Manumycin A on the wild type line. Furthermore, supplementation of SP inhibited cells with monoterpenoid intermediates downstream of the steps encoded by the ESMB genes restores monoterpenoid indole alkaloids biosynthesis. We conclude that protein targets for both PFT and PGGT-I are required for the expression of ESMB genes and monoterpenoid biosynthesis in C. roseus, this represents a non previously described role for protein prenyltransferase in plants.
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Affiliation(s)
- Vincent Courdavault
- Biomolecules et Biotechnologies Vegetales, Labaratoire de Physiologie Vegetale, UFR Science et Techniques, Universite Francois-Rabelais de Tours, EA2106, 37200 , Parc de Grandmont, Tours, France
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10
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Allen GJ, Murata Y, Chu SP, Nafisi M, Schroeder JI. Hypersensitivity of abscisic acid-induced cytosolic calcium increases in the Arabidopsis farnesyltransferase mutant era1-2. THE PLANT CELL 2002; 14:1649-62. [PMID: 12119381 PMCID: PMC150713 DOI: 10.1105/tpc.010448] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2001] [Accepted: 03/21/2002] [Indexed: 05/18/2023]
Abstract
Cytosolic calcium increases were analyzed in guard cells of the Arabidopsis farnesyltransferase deletion mutant era1-2 (enhanced response to abscisic acid). At low abscisic acid (ABA) concentrations (0.1 microM), increases of guard cell cytosolic calcium and stomatal closure were activated to a greater extent in the era1-2 mutant compared with the wild type. Patch clamping of era1-2 guard cells showed enhanced ABA sensitivity of plasma membrane calcium channel currents. These data indicate that the ERA1 farnesyltransferase targets a negative regulator of ABA signaling that acts between the points of ABA perception and the activation of plasma membrane calcium influx channels. Experimental increases of cytosolic calcium showed that the activation of S-type anion currents downstream of cytosolic calcium and extracellular calcium-induced stomatal closure were unaffected in era1-2, further supporting the positioning of era1-2 upstream of cytosolic calcium in the guard cell ABA signaling cascade. Moreover, the suppression of ABA-induced calcium increases in guard cells by the dominant protein phosphatase 2C mutant abi2-1 was rescued partially in era1-2 abi2-1 double mutant guard cells, further reinforcing the notion that ERA1 functions upstream of cytosolic calcium and indicating the genetic interaction of these two mutations upstream of ABA-induced calcium increases.
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Affiliation(s)
- Gethyn J Allen
- Cell and Developmental Biology Section, Division of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116, USA
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11
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Assmann SM. Heterotrimeric and unconventional GTP binding proteins in plant cell signaling. THE PLANT CELL 2002; 14 Suppl:S355-73. [PMID: 12045288 PMCID: PMC151266 DOI: 10.1105/tpc.001792] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2002] [Accepted: 03/24/2002] [Indexed: 05/17/2023]
Affiliation(s)
- Sarah M Assmann
- Biology Department, Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA.
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12
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Assmann SM. Heterotrimeric and unconventional GTP binding proteins in plant cell signaling. THE PLANT CELL 2002; 14 Suppl:S355-S373. [PMID: 12045288 DOI: 10.1105/tpc.001792.s356] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- Sarah M Assmann
- Biology Department, Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA.
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13
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Abstract
Plant protein isoprenylation has received considerable attention in the past decade. Since the initial discovery of isoprenylated plant proteins and their respective protein isoprenyltransferases, several research groups have endeavored to understand the physiological significance of this process in plants. Various experimental approaches, including inhibitor studies, systematic methods of protein identification, and mutant analyses in Arabidopsis thaliana, have enabled these groups to elucidate important roles for isoprenylated proteins in cell cycle control, signal transduction, cytoskeletal organization, and intracellular vesicle transport. This article reviews recent progress in understanding the functional implications of protein isoprenylation in plants.
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Affiliation(s)
- D N Crowell
- Department of Biology, Indiana University-Purdue University at Indianapolis, 723 West Michigan Street, IN 46202-5132, Indianapolis, USA
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14
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Yang W, Urano J, Tamanoi F. Protein farnesylation is critical for maintaining normal cell morphology and canavanine resistance in Schizosaccharomyces pombe. J Biol Chem 2000; 275:429-38. [PMID: 10617635 DOI: 10.1074/jbc.275.1.429] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein farnesyltransferase (FTase) plays important roles in the growth and differentiation of eukaryotic cells. In this paper, we report the identification of the Schizosaccharomyces pombe gene cpp1(+) encoding the beta-subunit of FTase. The predicted amino acid sequence of the cpp1(+) gene product shares significant similarity with FTase beta-subunits from a variety of organisms. S. pombe FTase purified from E. coli exhibits high enzymatic activity toward the CAAX farnesylation motif substrates (where C represents cysteine, A represents aliphatic amino acid, and X is preferentially methionine, cysteine, serine, alanine, or glutamine) while showing little preference for CAAL geranylgeranylation motif substrates (where L represents leucine or phenylalanine). cpp1(+) is not essential for growth as shown by gene disruption; however, mutant cells exhibit rounded or irregular cell morphology. Expression of a geranylgeranylated mutant form, Ras1-CVIL, which can bypass farnesylation, rescues these morphological defects. We also identify a novel phenotype of cpp1(-) mutants, hypersensitivity to canavanine. This appears to be due to a 3-4-fold increase in the rate of arginine uptake as compared with wild-type cells. Expression of the geranylgeranylated mutant form of a novel farnesylated small GTPase, SpRheb, is able to suppress the elevated arginine uptake rate. These results demonstrate that protein farnesylation is critical for maintaining normal cell morphology through Ras1 and canavanine resistance through SpRheb.
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Affiliation(s)
- W Yang
- Department of Microbiology, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California 90095-1489, USA
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15
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Abstract
Increasing numbers of plant proteins are being shown to have posttranslationally-attached lipids. The modifications include N-myristoylation, S-palmitoylation, prenylation by farnesyl or geranylgeranyl moieties, or attachment of glycosylphosphatidylinositol anchors. This report summarizes recent findings regarding the structure, metabolism and physiological functions of these important protein-linked lipids.
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Affiliation(s)
- G A Thompson
- Section of Molecular Cell and Developmental Biology, School of Biological Sciences, University of Texas, Austin, USA.
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16
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Nambara E, McCourt P. Protein farnesylation in plants: a greasy tale. CURRENT OPINION IN PLANT BIOLOGY 1999; 2:388-392. [PMID: 10508754 DOI: 10.1016/s1369-5266(99)00010-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Although farnesylation is required for a number of abscisic acid mediated responses in plants, knowledge of how this lipid modification of proteins regulates specific developmental and physiological processes remains unclear. Recent information from the Arabidopsis genome-sequencing project in combination with mutants deficient in farnesylation should unravel the role(s) of this process in plant signaling.
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Affiliation(s)
- E Nambara
- Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Canada M5S 3B2
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17
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Rodríguez-Concepción M, Yalovsky S, Gruissem W. Protein prenylation in plants: old friends and new targets. PLANT MOLECULAR BIOLOGY 1999; 39:865-870. [PMID: 10344192 DOI: 10.1023/a:1006170020836] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- M Rodríguez-Concepción
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA
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18
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Pei ZM, Ghassemian M, Kwak CM, McCourt P, Schroeder JI. Role of farnesyltransferase in ABA regulation of guard cell anion channels and plant water loss. Science 1998; 282:287-90. [PMID: 9765153 DOI: 10.1126/science.282.5387.287] [Citation(s) in RCA: 308] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Desiccation of plants during drought can be detrimental to agricultural production. The phytohormone abscisic acid (ABA) reduces water loss by triggering stomatal pore closure in leaves, a process requiring ion-channel modulation by cytoplasmic proteins. Deletion of the Arabidopsis farnesyltransferase gene ERA1 or application of farnesyltransferase inhibitors resulted in ABA hypersensitivity of guard cell anion-channel activation and of stomatal closing. ERA1 was expressed in guard cells. Double-mutant analyses of era1 with the ABA-insensitive mutants abi1 and abi2 showed that era1 suppresses the ABA-insensitive phenotypes. Moreover, era1 plants exhibited a reduction in transpirational water loss during drought treatment.
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Affiliation(s)
- Z M Pei
- Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093-0116, USA
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19
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Crowell DN, Sen SE, Randall SK. Prenylcysteine alpha-carboxyl methyltransferase in suspension-cultured tobacco cells. PLANT PHYSIOLOGY 1998; 118:115-23. [PMID: 9733531 PMCID: PMC34848 DOI: 10.1104/pp.118.1.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/1998] [Accepted: 05/23/1998] [Indexed: 05/19/2023]
Abstract
Isoprenylation is a posttranslational modification that is believed to be necessary, but not sufficient, for the efficient association of numerous eukaryotic cell proteins with membranes. Additional modifications have been shown to be required for proper intracellular targeting and function of certain isoprenylated proteins in mammalian and yeast cells. Although protein isoprenylation has been demonstrated in plants, postisoprenylation processing of plant proteins has not been described. Here we demonstrate that cultured tobacco (Nicotiana tabacum cv Bright Yellow-2) cells contain farnesylcysteine and geranylgeranylcysteine alpha-carboxyl methyltransferase activities with apparent Michaelis constants of 73 and 21 &mgr;M for N-acetyl-S-trans, trans-farnesyl-L-cysteine and N-acetyl-S-all-trans-geranylgeranyl-L-cysteine, respectively. Furthermore, competition analysis indicates that the same enzyme is responsible for both activities. These results suggest that alpha-carboxyl methylation is a step in the maturation of isoprenylated proteins in plants.
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Affiliation(s)
- DN Crowell
- Department of Biology, Indiana University-Purdue University at Indianapolis, 723 West Michigan Street, Indianapolis, Indiana 46202 (D.N.C., S.K.R.)
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20
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Trueblood CE, Boyartchuk VL, Rine J. Substrate specificity determinants in the farnesyltransferase beta-subunit. Proc Natl Acad Sci U S A 1997; 94:10774-9. [PMID: 9380709 PMCID: PMC23482 DOI: 10.1073/pnas.94.20.10774] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Protein prenyltransferases catalyze the covalent attachment of isoprenoid lipids (farnesyl or geranylgeranyl) to a cysteine near the C terminus of their substrates. This study explored the specificity determinants for interactions between the farnesyltransferase of Saccharomyces cerevisiae and its protein substrates. A series of substitutions at amino acid 149 of the farnesyltransferase beta-subunit were tested in combination with a series of substitutions at the C-terminal amino acid of CaaX protein substrates Ras2p and a-factor. Efficient prenylation was observed when oppositely charged amino acids were present at amino acid 149 of the yeast farnesyltransferase beta-subunit and the C-terminal amino acid of the CaaX protein substrate, but not when like charges were present at these positions. This evidence for electrostatic interaction between amino acid 149 and the C-terminal amino acid of CaaX protein substrates leads to the prediction that the C-terminal amino acid of the protein substrate binds near amino acid 149 of the yeast farnesyltransferase beta-subunit.
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Affiliation(s)
- C E Trueblood
- Division of Genetics, Department of Molecular and Cell Biology, 401 Barker Hall, University of California, Berkeley, CA 94720, USA
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21
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Yalovsky S, Trueblood CE, Callan KL, Narita JO, Jenkins SM, Rine J, Gruissem W. Plant farnesyltransferase can restore yeast Ras signaling and mating. Mol Cell Biol 1997; 17:1986-94. [PMID: 9121446 PMCID: PMC232045 DOI: 10.1128/mcb.17.4.1986] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Farnesyltransferase (FTase) is a heterodimeric enzyme that modifies a group of proteins, including Ras, in mammals and yeasts. Plant FTase alpha and beta subunits were cloned from tomato and expressed in the yeast Saccharomyces cerevisiae to assess their functional conservation in farnesylating Ras and a-factor proteins, which are important for cell growth and mating. The tomato FTase beta subunit (LeFTB) alone was unable to complement the growth defect of ram1 delta mutant yeast strains in which the chromosomal FTase beta subunit gene was deleted, but coexpression of LeFTB with the plant alpha subunit gene (LeFTA) restored normal growth, Ras membrane association, and mating. LeFTB contains a novel 66-amino-acid sequence domain whose deletion reduces the efficiency of tomato FTase to restore normal growth to yeast ram1 delta strains. Coexpression of LeFTA and LeFTB in either yeast or insect cells yielded a functional enzyme that correctly farnesylated CaaX-motif-containing peptides. Despite their low degree of sequence homology, yeast and plant FTases shared similar in vivo and in vitro substrate specificities, demonstrating that this enzymatic modification of proteins with intermediates from the isoprenoid biosynthesis pathway is conserved in evolutionarily divergent eukaryotes.
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Affiliation(s)
- S Yalovsky
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA
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22
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Del Villar K, Mitsuzawa H, Yang W, Sattler I, Tamanoi F. Amino acid substitutions that convert the protein substrate specificity of farnesyltransferase to that of geranylgeranyltransferase type I. J Biol Chem 1997; 272:680-7. [PMID: 8995312 DOI: 10.1074/jbc.272.1.680] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Protein farnesyltransferase (FTase), a heterodimer enzyme consisting of alpha and beta subunits, catalyzes the addition of farnesyl groups to the C termini of proteins such as Ras. In this paper, we report that the protein substrate specificity of yeast FTase can be switched to that of a closely related enzyme, geranylgeranyltransferase type I (GGTase I) by a single amino acid change at one of the three residues: Ser-159, Tyr-362, or Tyr-366 of its beta-subunit, Dpr1. All three Dpr1 mutants can function as either FTase or GGTase I beta subunit in vivo, although some differences in efficiency were observed. These results point to the importance of two distinct regions (one at 159 and the other at 362 and 366) of Dpr1 for the recognition of the protein substrate. Analysis of the protein, after site directed mutagenesis was used to change Ser-159 to all possible amino acids, showed that either asparagine or aspartic acid at this position allowed FTase beta to function as GGTase I beta. A similar site-directed mutagenesis study on Tyr-362 showed that leucine, methionine, or isoleucine at this position also resulted in the ability of mutant FTase beta to function as GGTase I beta. Interestingly, in both position 159 and 362 substitutions, amino acids that could change the protein substrate specificity had similar van der Waals volumes. Biochemical characterization of the S159N and Y362L mutant proteins showed that their kcat/Km values for GGTase I substrate are increased about 20-fold compared with that of the wild type protein. These results demonstrate that the conversion of the protein substrate specificity of FTase to that of GGTase I can be accomplished by introducing a distinct size amino acid at either of the two residues, 159 and 362.
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Affiliation(s)
- K Del Villar
- Department of Microbiology and Molecular Genetics, Molecular Biology Institute, UCLA, Los Angeles, California 90095-1489, USA
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23
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Qian D, Zhou D, Ju R, Cramer CL, Yang Z. Protein farnesyltransferase in plants: molecular characterization and involvement in cell cycle control. THE PLANT CELL 1996; 8:2381-94. [PMID: 8989889 PMCID: PMC161360 DOI: 10.1105/tpc.8.12.2381] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Farnesylation is required for membrane targeting, protein-protein interactions, and the biological activity of key regulatory proteins, such as Ras small GTPases and protein kinases in a wide range of eukaryotes. In this report, we describe the molecular identification of a plant protein farnesyltransferase (FTase) and evidence for its role in the control of the cell cycle in plants. A pea gene encoding a homolog of the FTase beta subunit was previously cloned using a polymerase chain reaction-based strategy. A similar approach was used to clone a pea gene encoding a homolog of the FTase alpha subunit. The biochemical function of the pea FTase homologs was demonstrated by the reconstitution of FTase enzyme activity using FTase fusion proteins coexpressed in Escherichia coll. RNA gel blot analyses showed that levels of FTase mRNAs are generally higher in tissues, such as those of nodules, that are active in cell division. The relationship of FTase to cell division was further analyzed during the growth of suspension-cultured tobacco BY-2 cells. A biphasic fluctuation of FTase enzyme activity preceded corresponding changes in mitotic activity at the early log phase of cell growth. Moreover, manumycin, a specific inhibitor of FTase, was effective in inhibiting mitosis and growth in these cells. Using synchronized BY-2 cells, manumycin completely blocked mitosis when added at the early S phase but not when added at the G2 phase. These data suggest that FTase is required for the plant cell cycle, perhaps by modulating the progression through the S phase and the transition from G1 to the S phase.
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Affiliation(s)
- D Qian
- Department of Plant Biology, Ohio State University, Columbus 43210, USA
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24
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Schmitt D, Callan K, Gruissem W. Molecular and biochemical characterization of tomato farnesyl-protein transferase. PLANT PHYSIOLOGY 1996; 112:767-777. [PMID: 8883388 PMCID: PMC158001 DOI: 10.1104/pp.112.2.767] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The prenylation of membrane-associated proteins involved in the regulation of eukaryotic cell growth and signal transduction is critically important for their subcellular localization and biological activity. In contrast to mammalian cells and yeast, however, the function of protein prenylation in plants is not well understood and only a few prenylated proteins have been identified. We partially purified and characterized farnesyl-protein transferase from tomato (Lycopersicon esculentum, LeFTase) to analyze its biochemical and molecular properties. Using Ras- and G gamma-specific peptide substrates and competition assays we showed that tomato protein extracts have both farnesyl-protein transferase and geranylgeranyl-protein transferase 1 activities. Compared with the heterologous synthetic peptide substrates, the plant-specific CaaX sequence of the ANJ1 protein is a less efficient substrate for LeFTase in vitro. LeFTase activity profiles and LeFTase beta-subunit protein (LeFTB) levels differ significantly in various tissues and are regulated during fruit development. Partially purified LeFTase requires Zn2+ and Mg2+ for enzymatic activity and has an apparent molecular mass of 100 kD Immunoprecipitation experiments using anti-alpha LeFTB antibodies confirmed that LeFTB is a component of LeFTase but not of tomato geranylgeranyl-protein transferase 1. Based on their conserved bio-chemical activities, we expect that prenyltransferases are likely integrated with the sterol biosynthesis pathway in the control of plant cell growth.
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Affiliation(s)
- D Schmitt
- Department of Plant Biology, University of California, Berkeley 94720, USA
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25
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26
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Abstract
The occurrence of protein farnesyltransferase has been demonstrated in spinach. The enzyme transferred different prenyl groups to the nonapeptide acceptor. All-trans isoprenoid diphosphates were utilized most efficiently in contrast to long-chain mainly cis-polyprenyl diphosphates and dolichyl diphosphates. The activity of the enzyme was stimulated by divalent cations. The presence of protein farnesyltransferase activity in several plant species has been confirmed.
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Affiliation(s)
- E Skoczylas
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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27
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Parmryd I, Shipton CA, Swiezewska E, Andersson B, Dallner G. Identification of spinach farnesyl protein transferase. Dithiothreitol as an acceptor in vitro. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 234:723-31. [PMID: 8575428 DOI: 10.1111/j.1432-1033.1995.723_a.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Spinach seedlings were found to contain farnesyl protein transferase. The enzyme is activated by Zn2+, but not by Mg2+. The pH optimum is approximately 7.0 and maximal activity is obtained at 40-45 degrees C. The apparent Km for the farnesyl diphosphate substrate is 7 microM. Western blotting of soluble proteins with an antiserum raised against mammalian farnesyl protein transferase demonstrated a specific cross-reactivity with the spinach enzyme. The antiserum preferentially recognises the beta-subunit of the heterodimeric farnesyl protein transferase, and the corresponding spinach polypeptide has a molecular mass of 42 kDa on SDS/PAGE. The enzyme can employ dithiothreitol as an acceptor for the farnesyl moiety and catalyses the formation of a thioether linkage between these substrates. On the basis of this discovery, a new method was developed utilising the hydrophobicity of the reaction product, and its interaction with poly(propylene). During in vivo labelling, the plants took up dithiothreitol, which inhibited the incorporation of [3H]mevalonate metabolites into proteins, indicating that dithiothreitol might be isoprenylated in vivo as well as in vitro. However, isoprenylation of some proteins remains unaffected by dithiothreitol suggesting the existence of different isoprenylation mechanisms. Thus, it is demonstrated that plants possess farnesyl protein transferase, which resembles its mammalian and yeast homologues.
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Affiliation(s)
- I Parmryd
- Arrhenius Laboratories for Natural Sciences, Biochemistry Department, Stockholm University, Sweden
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28
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Enjuto M, Lumbreras V, Marín C, Boronat A. Expression of the Arabidopsis HMG2 gene, encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, is restricted to meristematic and floral tissues. THE PLANT CELL 1995; 7:517-27. [PMID: 7780305 PMCID: PMC160801 DOI: 10.1105/tpc.7.5.517] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The synthesis of mevalonate, which is considered the first rate-limiting step in isoprenoid biosynthesis, is catalyzed by the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR; EC 1.1.1.34). In Arabidopsis, HMGR is encoded by two differentially expressed genes (HMG1 and HMG2). The transcriptional activity of the HMG2 gene was studied after fusing different regions of its 5' flanking region to the beta-glucuronidase (GUS) reporter gene and transforming the resulting constructs into tobacco plants. The spatial and temporal expression directed by the HMG2 promoter in the transgenic plants is consistent with the expression pattern previously established by RNA analysis using an HMG2-specific probe. HMG2 expression is restricted to meristematic (root tip and shoot apex) and floral (secretory zone of the stigma, mature pollen grains, gynoecium vascular tissue, and fertilized ovules) tissues. Deletion analysis of the HMG2 5' flanking region was conducted in transgenic plants and transfected protoplasts. The region containing nucleotides -857 to +64 of the HMG2 gene was sufficient to confer high levels of expression in both floral and meristematic tissues, although deletion to nucleotide -503 resulted in almost complete loss of expression. Sequences contained within the 5' transcribed, untranslated region are also important for gene expression. The biological significance of the restricted pattern of expression of HMG2 is also discussed.
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Affiliation(s)
- M Enjuto
- Departament de Bioquímica i Fisiologia, Facultat de Química, Universitat de Barcelona, Spain
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29
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Shipton CA, Parmryd I, Swiezewska E, Andersson B, Dallner G. Isoprenylation of plant proteins in vivo. Isoprenylated proteins are abundant in the mitochondria and nuclei of spinach. J Biol Chem 1995; 270:566-72. [PMID: 7822281 DOI: 10.1074/jbc.270.2.566] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Protein isoprenylation in vivo is demonstrated using spinach seedlings labeled with [3H]mevalonate. This report provides evidence for the occurrence of a large number of isoprenylated proteins in plants. Seedlings, without roots, were labeled quantitatively through the cut stem. Mevinolin treatment of the seedlings resulted in increased incorporation of radiolabel into proteins. Approximately 30 labeled bands could be detected after autoradiography of SDS-polyacrylamide gel electrophoresis-separated polypeptides, ranging in molecular mass from 6 to 200 kDa. Methyl iodide hydrolysis resulted in the release of covalently bound farnesol, geranylgeraniol, phytol, and some unidentified isoprenoid compounds from mevalonate-labeled proteins. It was found that all cellular fractions contained some isoprenylated proteins, although most were located in the mitochondria and nuclei. Subfractionation of the nucleus revealed that the majority of isoprenylated proteins in this compartment were components of the nuclear matrix. The results demonstrate that in vivo labeling of a complex organism can be performed using a plant system in order to study protein isoprenylation and distribution of modified proteins in different cellular compartments.
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Affiliation(s)
- C A Shipton
- Arrhenius Laboratories for Natural Sciences, Biochemistry Department, University of Stockholm, Sweden
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30
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Grünler J, Ericsson J, Dallner G. Branch-point reactions in the biosynthesis of cholesterol, dolichol, ubiquinone and prenylated proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1212:259-77. [PMID: 8199197 DOI: 10.1016/0005-2760(94)90200-3] [Citation(s) in RCA: 208] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- J Grünler
- Department of Biochemistry, University of Stockholm, Sweden
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31
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Photoaffinity-labeling peptide substrates for farnesyl-protein transferase and the intersubunit location of the active site. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42374-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Gillaspy G, Ben-David H, Gruissem W. Fruits: A Developmental Perspective. THE PLANT CELL 1993. [PMID: 12271039 DOI: 10.2307/3869794] [Citation(s) in RCA: 176] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Affiliation(s)
- G. Gillaspy
- Department of Plant Biology, University of California, Berkeley, California 94720
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33
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Gillaspy G, Ben-David H, Gruissem W. Fruits: A Developmental Perspective. THE PLANT CELL 1993; 5:1439-1451. [PMID: 12271039 PMCID: PMC160374 DOI: 10.1105/tpc.5.10.1439] [Citation(s) in RCA: 472] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- G. Gillaspy
- Department of Plant Biology, University of California, Berkeley, California 94720
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34
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Zhu JK, Bressan RA, Hasegawa PM. Isoprenylation of the plant molecular chaperone ANJ1 facilitates membrane association and function at high temperature. Proc Natl Acad Sci U S A 1993; 90:8557-61. [PMID: 8378331 PMCID: PMC47396 DOI: 10.1073/pnas.90.18.8557] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We demonstrate that ANJ1, a higher plant homolog of the bacterial molecular chaperone DnaJ, is a substrate in vitro for protein farnesyl- and geranylgeranyl-transferase activities present in cell extracts of the plant Atriplex nummularia and yeast Saccharomyces cerevisiae. Isoprenylation did not occur when cysteine was replaced by serine in the CAQQ motif at the carboxyl terminus of ANJ1, indicating that this sequence functions as a CaaX consensus sequence for polyisoprenylation (where C is cysteine, a is an aliphatic residue, and X is any amino acid residue). Substitution of leucine for the terminal glutamine did not result in the expected geranylgeranylation as occurs with mammalian proteins containing a carboxyl-terminal leucine. Unlike the wild-type ANJ1, neither of the proteins containing these amino acid substitutions could functionally complement the yeast temperature-sensitive mutant mas5. Farnesylation enhanced the association of ANJ1 with A. nummularia microsomal membranes. Electrophoretic mobility of ANJ1 from the plant indicated that the protein is isoprenylated in vivo.
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Affiliation(s)
- J K Zhu
- Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165
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35
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Yang Z, Watson JC. Molecular cloning and characterization of rho, a ras-related small GTP-binding protein from the garden pea. Proc Natl Acad Sci U S A 1993; 90:8732-6. [PMID: 8378356 PMCID: PMC47432 DOI: 10.1073/pnas.90.18.8732] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The rho proteins, members of the ras superfamily of small GTP-binding proteins, play a central role in the modulation of cellular functions involving the actin cytoskeleton such as in the establishment of cell polarity and morphology. As a first step in elucidating signal transduction pathways leading to processes mediated by the actin cytoskeleton in plants, we initiated cloning and characterization of rho proteins from pea. One rho-related, partial cDNA clone of 167 bp was isolated utilizing a polymerase chain reaction-based cloning strategy, using degenerate primers that correspond to conserved domains within the rho proteins. A full-length cDNA was isolated by screening a pea cDNA library using the 167-bp cDNA as a probe. The Rho1Ps cDNA contains an open reading frame encoding a polypeptide (Rho1Ps) of 197 amino acids that shows 45-64% sequence identity to members of the rho family and about 30% identity to other members of the ras superfamily. In addition to the nucleotide-binding and GTPase domains, Rho1Ps shares conserved residues and motifs unique to the rho proteins. Purified Rho1Ps protein expressed in Escherichia coli retains specific GTP-binding activity. These data indicate that Rho1Ps encodes a small GTP-binding protein of the rho family. The Rho1Ps transcript is expressed in all organs of pea seedlings, being more abundant in root tips and apical buds. DNA gel blot analyses show that the rho proteins in pea are encoded by a multigene family.
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Affiliation(s)
- Z Yang
- Department of Botany, University of Maryland, College Park 20742-5815
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36
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Randall SK, Marshall MS, Crowell DN. Protein isoprenylation in suspension-cultured tobacco cells. THE PLANT CELL 1993; 5:433-42. [PMID: 8485402 PMCID: PMC160282 DOI: 10.1105/tpc.5.4.433] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Many mammalian and yeast proteins, including small ras-like GTP binding proteins, heterotrimeric G protein gamma subunits, and nuclear lamins, have been shown to be covalently linked to isoprenoid derivatives of mevalonic acid. Isoprenylation of these proteins is required for their assembly into membranes and, hence, for their biological activity. In this report, it is shown that cultured tobacco cells, when pretreated with an inhibitor of endogenous mevalonic acid synthesis (lovastatin), incorporate radioactivity from 14C-mevalonic acid into proteins. Most of these proteins are membrane associated, and many are similar in mass to mammalian ras-like GTP binding proteins and nuclear lamins. Furthermore, it is shown that tobacco cell extracts catalyze the transfer of radioactivity from 3H-farnesyl pyrophosphate and 3H-geranylgeranyl pyrophosphate to protein substrates in vitro. These studies indicate the presence of at least two distinct prenyl:protein transferases in tobacco extracts: one that utilizes farnesyl pyrophosphate and preferentially modifies a substrate protein with a CAIM carboxy terminus (farnesyl:protein transferase) and one that utilizes geranylgeranyl pyrophosphate and preferentially modifies a substrate protein with a CAIL carboxy terminus (geranylgeranyl:protein transferase type I). This work provides a basis for future work on the role of protein isoprenylation in plant cell growth, signal transduction, and membrane biogenesis.
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Affiliation(s)
- S K Randall
- Department of Biology, Indiana University-Purdue University, Indianapolis 46202-5132
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