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Akimoto‐Tomiyama C, Tanabe S, Kajiwara H, Minami E, Ochiai H. Loss of chloroplast-localized protein phosphatase 2Cs in Arabidopsis thaliana leads to enhancement of plant immunity and resistance to Xanthomonas campestris pv. campestris infection. MOLECULAR PLANT PATHOLOGY 2018; 19:1184-1195. [PMID: 28815858 PMCID: PMC6637992 DOI: 10.1111/mpp.12596] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 08/08/2017] [Accepted: 08/12/2017] [Indexed: 05/20/2023]
Abstract
Protein phosphatases (PPs) counteract kinases in reversible phosphorylation events during numerous signal transduction pathways in eukaryotes. PP2Cs, one of the four major classes of the serine/threonine-specific PP family, are greatly expanded in plants. Thus, PP2Cs are thought to play a specific role in signal transduction pathways. Some rice PP2Cs classified in subgroup K are responsive to infection by the compatible Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight. In Arabidopsis thaliana, orthologous PP2C genes (AtPP2C62 and AtPP2C26) classified to subgroup K are also responsive to Xanthomonas campestris pv. campestris (Xcc, causal agent of black rot) infection. To elucidate the function of these subgroup K PP2Cs, atpp2c62- and atpp2c26-deficient A. thaliana mutants were characterized. A double mutant plant which was inoculated with a compatible Xcc showed reduced lesion development, as well as the suppression of bacterial multiplication. AtPP2C62 and AtPP2C26 localized to the chloroplast. Furthermore, the photosynthesis-related protein, chaperonin-60, was indicated as the potential candidate for the dephosphorylated substrate catalysed by AtPP2C62 and AtPP2C26 using two-dimensional isoelectric focusing sodium dodecylsulfate-polyacrylamide gel electrophoresis (2D-IDF-SDS-PAGE). Taken together, AtPP2C62 and AtPP2C26 are suggested to be involved in both photosynthesis and suppression of the plant immune system. These results imply the occurrence of crosstalk between photosynthesis and the plant defence system to control productivity under pathogen infection.
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Affiliation(s)
- Chiharu Akimoto‐Tomiyama
- Institute of Agrobiological Sciences, National Agriculture and Food Research OrganizationTsukubaIbaraki 305‐8602, Japan
| | - Shigeru Tanabe
- Institute of Agrobiological Sciences, National Agriculture and Food Research OrganizationTsukubaIbaraki 305‐8602, Japan
- Present address:
Sakata Seed CorporationYokohamaJapan
| | - Hideyuki Kajiwara
- Advanced Analysis CenterNational Agriculture and Food Research OrganizationTsukubaIbaraki 305‐8602, Japan
| | - Eiichi Minami
- Institute of Agrobiological Sciences, National Agriculture and Food Research OrganizationTsukubaIbaraki 305‐8602, Japan
| | - Hirokazu Ochiai
- Institute of Agrobiological Sciences, National Agriculture and Food Research OrganizationTsukubaIbaraki 305‐8602, Japan
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Kim SR, Yang JI, An G. OsCpn60α1, encoding the plastid chaperonin 60α subunit, is essential for folding of rbcL. Mol Cells 2013; 35:402-9. [PMID: 23620301 PMCID: PMC3887859 DOI: 10.1007/s10059-013-2337-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 03/12/2013] [Accepted: 03/12/2013] [Indexed: 01/06/2023] Open
Abstract
Chaperonins are involved in protein-folding. The rice genome encodes six plastid chaperonin subunits (Cpn60) - three α and three β. Our study showed that they were differentially expressed during normal plant development. Moreover, five were induced by heat stress (42°C) but not by cold (10°C). The oscpn60α1 mutant had a pale-green phenotype at the seedling stage and development ceased after the fourth leaf appeared. Transiently expressed OsCpn60α1:GFP fusion protein was localized to the chloroplast stroma. Immuno-blot analysis indicated that the level of Rubisco large subunit (rbcL) was severely reduced in the mutant while levels were unchanged for some imported proteins, e.g., stromal heat shock protein 70 (Hsp70) and chlorophyll a/b binding protein 1 (Lhcb1). This demonstrated that OsCpn60α1 is required for the folding of rbcL and that failure of that process is seedling-lethal.
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Affiliation(s)
- Sung-Ryul Kim
- Crop Biotech Institute and Department of Genetic Engineering, Kyung Hee University, Yongin 446-701,
Korea
| | - Jung-Il Yang
- Crop Biotech Institute and Department of Genetic Engineering, Kyung Hee University, Yongin 446-701,
Korea
| | - Gynheung An
- Crop Biotech Institute and Department of Genetic Engineering, Kyung Hee University, Yongin 446-701,
Korea
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Hao JH, Dong CJ, Zhang ZG, Wang XL, Shang QM. Insights into salicylic acid responses in cucumber (Cucumis sativus L.) cotyledons based on a comparative proteomic analysis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 187:69-82. [PMID: 22404834 DOI: 10.1016/j.plantsci.2012.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 12/20/2011] [Accepted: 01/04/2012] [Indexed: 05/04/2023]
Abstract
To investigate the response of cucumber seedlings to exogenous salicylic acid (SA) and gain a better understanding of SA action mechanism, we generated a proteomic profile of cucumber (Cucumis sativus L.) cotyledons treated with exogenous SA. Analysis of 1500 protein spots from each gel revealed 63 differentially expressed proteins, 59 of which were identified successfully. Of the identified proteins, 97% matched cucumber proteins using a whole cucumber protein database based on the newly completed genome established by our laboratory. The identified proteins were involved in various cellular responses and metabolic processes, including antioxidative reactions, cell defense, photosynthesis, carbohydrate metabolism, respiration and energy homeostasis, protein folding and biosynthesis. The two largest functional categories included proteins involved in antioxidative reactions (23.7%) and photosynthesis (18.6%). Furthermore, the SA-responsive protein interaction network revealed 13 key proteins, suggesting that the expression changes of these proteins could be critical for SA-induced resistance. An analysis of these changes suggested that SA-induced resistance and seedling growth might be regulated in part through pathways involving antioxidative reactions and photosynthesis.
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Affiliation(s)
- J H Hao
- The Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Haidian District, Beijing 100081, PR China
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Balaji B, Gilson M, Roy H. Binding of a transition state analog to newly synthesized Rubisco. PHOTOSYNTHESIS RESEARCH 2006; 89:43-8. [PMID: 16763877 DOI: 10.1007/s11120-006-9067-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2006] [Accepted: 04/22/2006] [Indexed: 05/10/2023]
Abstract
Radioactive amino acids, when added to isolated pea chloroplasts or chloroplast extracts engaged in protein synthesis, are incorporated into Rubisco large subunits that co-migrate with native Rubisco during nondenaturing electrophoresis. We have added the transition state analog 2'-carboxyarabinitol bisphosphate (CABP) to chloroplast extracts after in organello or in vitro incorporation of radioactive amino acids into Rubisco large subunits. Upon addition of CABP the radioactive bands co-migrating with native Rubisco undergo a readily detected shift in electrophoretic mobility just as the native enzyme, thus demonstrating the ability of the newly assembled molecules to interact with this transition state analog.
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Affiliation(s)
- Boovaraghan Balaji
- Biology Department, Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA
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Dickson R, Weiss C, Howard RJ, Alldrick SP, Ellis RJ, Lorimer G, Azem A, Viitanen PV. Reconstitution of higher plant chloroplast chaperonin 60 tetradecamers active in protein folding. J Biol Chem 2000; 275:11829-35. [PMID: 10766808 DOI: 10.1074/jbc.275.16.11829] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Unlike the GroEL homologs of eubacteria and mitochondria, oligomer preparations of the higher plant chloroplast chaperonin 60 (cpn60) consist of roughly equal amounts of two divergent subunits, alpha and beta. The functional significance of these isoforms, their structural organization into tetradecamers, and their interactions with the unique binary chloroplast chaperonin 10 (cpn10) have not been elucidated. Toward this goal, we have cloned the alpha and beta subunits of the ch-cpn60 of pea (Pisum sativum), expressed them individually in Escherichia coli, and subjected the purified monomers to in vitro reconstitution experiments. In the absence of other factors, neither subunit (alone or in combination) spontaneously assembles into a higher order structure. However, in the presence of MgATP, the beta subunits form tetradecamers in a cooperative reaction that is potentiated by cpn10. In contrast, alpha subunits only assemble in the presence of beta subunits. Although beta and alpha/beta 14-mers are indistinguishable by electron microscopy and can both assist protein folding, their specificities for cpn10 are entirely different. Similar to the authentic chloroplast protein, the reconstituted alpha/beta 14-mers are functionally compatible with bacterial, mitochondrial, and chloroplast cpn10. In contrast, the folding reaction mediated by the reconstituted beta 14-mers is only efficient with mitochondrial cpn10. The ability to reconstitute two types of functional oligomer in vitro provides a unique tool, which will allow us to investigate the mechanism of this unusual chaperonin system.
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Affiliation(s)
- R Dickson
- Molecular Biology Division, Central Research and Development Department, E. I. DuPont de Nemours and Company, Experimental Station, Wilmington, Delaware 19880-0402, USA
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Boston RS, Viitanen PV, Vierling E. Molecular chaperones and protein folding in plants. PLANT MOLECULAR BIOLOGY 1996; 32:191-222. [PMID: 8980480 DOI: 10.1007/bf00039383] [Citation(s) in RCA: 282] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Protein folding in vivo is mediated by an array of proteins that act either as 'foldases' or 'molecular chaperones'. Foldases include protein disulfide isomerase and peptidyl prolyl isomerase, which catalyze the rearrangement of disulfide bonds or isomerization of peptide bonds around Pro residues, respectively. Molecular chaperones are a diverse group of proteins, but they share the property that they bind substrate proteins that are in unstable, non-native structural states. The best understood chaperone systems are HSP70/DnaK and HSP60/GroE, but considerable data support a chaperone role for other proteins, including HSP100, HSP90, small HSPs and calnexin. Recent research indicates that many, if not all, cellular proteins interact with chaperones and/or foldases during their lifetime in the cell. Different chaperone and foldase systems are required for synthesis, targeting, maturation and degradation of proteins in all cellular compartments. Thus, these diverse proteins affect an exceptionally broad array of cellular processes required for both normal cell function and survival of stress conditions. This review summarizes our current understanding of how these proteins function in plants, with a major focus on those systems where the most detailed mechanistic data are available, or where features of the chaperone/foldase system or substrate proteins are unique to plants.
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Affiliation(s)
- R S Boston
- Department of Botany, North Carolina State University, Raleigh 27695, USA
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8
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Boston RS, Viitanen PV, Vierling E. Molecular chaperones and protein folding in plants. PLANT MOLECULAR BIOLOGY 1996. [PMID: 8980480 DOI: 10.1007/978-94-009-0353-1_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Protein folding in vivo is mediated by an array of proteins that act either as 'foldases' or 'molecular chaperones'. Foldases include protein disulfide isomerase and peptidyl prolyl isomerase, which catalyze the rearrangement of disulfide bonds or isomerization of peptide bonds around Pro residues, respectively. Molecular chaperones are a diverse group of proteins, but they share the property that they bind substrate proteins that are in unstable, non-native structural states. The best understood chaperone systems are HSP70/DnaK and HSP60/GroE, but considerable data support a chaperone role for other proteins, including HSP100, HSP90, small HSPs and calnexin. Recent research indicates that many, if not all, cellular proteins interact with chaperones and/or foldases during their lifetime in the cell. Different chaperone and foldase systems are required for synthesis, targeting, maturation and degradation of proteins in all cellular compartments. Thus, these diverse proteins affect an exceptionally broad array of cellular processes required for both normal cell function and survival of stress conditions. This review summarizes our current understanding of how these proteins function in plants, with a major focus on those systems where the most detailed mechanistic data are available, or where features of the chaperone/foldase system or substrate proteins are unique to plants.
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Affiliation(s)
- R S Boston
- Department of Botany, North Carolina State University, Raleigh 27695, USA
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9
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Abstract
The folding of many newly synthesized proteins in the cell depends on a set of conserved proteins known as molecular chaperones. These prevent the formation of misfolded protein structures, both under normal conditions and when cells are exposed to stresses such as high temperature. Significant progress has been made in the understanding of the ATP-dependent mechanisms used by the Hsp70 and chaperonin families of molecular chaperones, which can cooperate to assist in folding new polypeptide chains.
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Affiliation(s)
- F U Hartl
- Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York 10021, USA
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10
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Viitanen PV, Schmidt M, Buchner J, Suzuki T, Vierling E, Dickson R, Lorimer GH, Gatenby A, Soll J. Functional characterization of the higher plant chloroplast chaperonins. J Biol Chem 1995; 270:18158-64. [PMID: 7629128 DOI: 10.1074/jbc.270.30.18158] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The higher plant chloroplast chaperonins (ch-cpn60 and ch-cpn10) have been purified and their structural/functional properties examined. In all plants surveyed, both proteins were constitutively expressed, and only modest increases in their levels were detected upon heat shock. Like GroEL and GroES of Escherichia coli, the chloroplast chaperonins can physically interact with each other. The asymmetric complexes that form in the presence of ADP are "bullet-shaped" particles that likely consist of 1 mol each of ch-cpn60 and ch-cpn10. The purified ch-cpn60 is a functional molecular chaperone. Under "nonpermissive" conditions, where spontaneous folding was not observed, it was able to assist in the refolding of two different target proteins. In both cases, successful partitioning to the native state also required ATP hydrolysis and chaperonin 10. Surprisingly, however, the "double-domain" ch-cpn10, comprised of unique 21-kDa subunits, was not an obligatory co-chaperonin. Both GroES and a mammalian mitochondrial homolog were equally compatible with the ch-cpn60. Finally, the assisted-folding reaction mediated by the chloroplast chaperonins does not require K+ ions. Thus, the K(+)-dependent ATPase activity that is observed with other known groEL homologs is not a universal property of all chaperonin 60s.
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Affiliation(s)
- P V Viitanen
- Central Research and Development Department, E. I. DuPont de Nemours and Company, Wilmington, Delaware 19880-0402, USA
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11
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Thompson MD, Paavola CD, Lenvik TR, Gantt JS. Chlamydomonas transcripts encoding three divergent plastid chaperonins are heat-inducible. PLANT MOLECULAR BIOLOGY 1995; 27:1031-1035. [PMID: 7766872 DOI: 10.1007/bf00037029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Three cDNAs encoding plastid cpn60 chaperonin subunits have been isolated from the unicellular green alga Chlamydomonas reinhardtii. Based on comparisons of the predicted amino acid sequences, we conclude that Chlamydomonas, like higher plants, contains divergent plastid cpn60-alpha and cpn60-beta subunits. The predicted amino acid sequences of the two Chlamydomonas cpn60-beta subunits differ significantly (24% divergent), indicating that the two cpn60-beta subunits have been selectively maintained for a considerable period of time. Unlike plastid chaperonin transcripts in higher plants, heat shock conditions (42 degrees C) lead to a rapid increase (10- to 30-fold) in the level of each of the three plastid transcripts.
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Affiliation(s)
- M D Thompson
- Department of Plant Biology, University of Minnesota, St. Paul 55108, USA
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12
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Assembly of in vitro synthesized large subunits into ribulose-bisphosphate carboxylase/oxygenase. Formation and discharge of an L8-like species. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)38680-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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13
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Mayer F. Principles of functional and structural organization in the bacterial cell: 'compartments' and their enzymes. FEMS Microbiol Rev 1993; 10:327-45. [PMID: 8318263 DOI: 10.1111/j.1574-6968.1993.tb05874.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Most bacteria lack obvious compartmentation, i.e., structural partition of the cell into functional entities (organelles) formed by a closed biological membrane. Nevertheless, these organisms exhibit sophisticated regulation and interactions of their catabolic and anabolic pathways; they are able to exploit a great variety of carbon and energy sources, and they conserve and transform energy in an efficient manner. In a less stringent sense, 'compartments' are also present in bacteria if one accepts that bacterial 'compartments' are not necessarily surrounded by a membrane, but are rather defined as mere functional entities characterized by their structural components, their enzymes and other functional proteins such as binding proteins. This view would mean that the bacterial cell can be described as a highly organized structured system comprised of these functional entities. Regulated transport processes within 'compartments' and across boundaries involving low and high molecular mass compounds, solutes, and ions take place within the 'framework' constituted by this structured system. Special emphasis is given to the fact that many of the transport processes take place involving the functional entity 'energized membrane'. This 'framework', the structural basis for the functional potential of a bacterial cell, can be studied by electron microscopy. Advanced sample preparation techniques and imaging modes are available which keep the danger of artefact formation low; they can be applied at cellular and macromolecular levels. Recent developments in immunoelectron microscopy and affinity labelling techniques provide tools which allow to unequivocally locate enzymes and other antigens in the cell and to identify polypeptide chains in enzyme complexes. Application of these approaches in studies on cellular and macromolecular organization of bacteria and their enzyme systems confirmed some old views but also extended our knowledge. This is exemplified by a description of selected enzyme complexes located in the bacterial cytoplasm, in the cytoplasmic membrane or attached to it, in the periplasmic space, and attached to the cell wall or set free into the surrounding medium.
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Affiliation(s)
- F Mayer
- Institut für Mikrobiologie, Georg-August-Universität Göttingen, FRG
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Zabaleta E, Oropeza A, Jiménez B, Salerno G, Crespi M, Herrera-Estrella L. Isolation and characterization of genes encoding chaperonin 60β from Arabidopsis thaliana. Gene 1992; 111:175-81. [PMID: 1347275 DOI: 10.1016/0378-1119(92)90685-i] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Chaperonins (Cpn) are implicated in the folding and assembly of multimeric proteins in plastids and mitochondria of eukaryotes and in prokaryotes. Plastid Cpn is composed of two different polypeptides termed Cpn60 alpha and Cpn60 beta. We have isolated cDNA and genomic clones encoding Cpn60 beta from Arabidopsis thaliana. The steady-state level of the cpn60 beta mRNAs is higher in etiolated leaves and sucrose-treated plants as compared to control leaves. The A. thaliana cpn60 beta gene family consists of at least three different coding units. It was confirmed that Cpn beta-encoding genes have a high level of conservation among plants.
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Affiliation(s)
- E Zabaleta
- Centro de Investigaciones Biológicas, FIBA, Mar del Plata, Argentina
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15
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Viitanen PV, Donaldson GK, Lorimer GH, Lubben TH, Gatenby AA. Complex interactions between the chaperonin 60 molecular chaperone and dihydrofolate reductase. Biochemistry 1991; 30:9716-23. [PMID: 1680394 DOI: 10.1021/bi00104a021] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The spontaneous refolding of chemically denatured dihydrofolate reductase (DHFR) is completely arrested by chaperonin 60 (GroEL). This inhibition presumably results from the formation of a stable complex between chaperonin 60 and one or more intermediates in the folding pathway. While sequestered on chaperonin 60, DHFR is considerably more sensitive to proteolysis, suggesting a nonnative structure. Bound DHFR can be released from chaperonin 60 with ATP, and although chaperonin 10 (GroES) is not obligatory, it does potentiate the maximum effect of ATP. Hydrolysis of ATP is also not required for DHFR release since certain nonhydrolyzable analogues are capable of partial discharge. "Native" DHFR can also form a stable complex with chaperonin 60. However, in this case, complex formation is not instantaneous and can be prevented by the presence of DHFR substrates. This suggests that native DHFR exists in equilibrium with at least one conformer which is recognizable by chaperonin 60. Binding studies with 35S-labeled DHFR support these conclusions and further demonstrate that DHFR competes for a common saturable site with another protein (ribulose-1,5-bisphosphate carboxylase) known to interact with chaperonin 60.
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Affiliation(s)
- P V Viitanen
- Central Research and Development Department, E.I. du Pont de Nemours and Company, Wilmington, Delaware 19880-0402
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16
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Langer T, Neupert W. Heat shock proteins hsp60 and hsp70: their roles in folding, assembly and membrane translocation of proteins. Curr Top Microbiol Immunol 1991; 167:3-30. [PMID: 1675979 DOI: 10.1007/978-3-642-75875-1_1] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- T Langer
- Institut für Physiologische Chemie, Universität München, FRG
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17
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Newman SM, Cattolico RA. Ribulose bisphosphate carboxylase in algae: synthesis, enzymology and evolution. PHOTOSYNTHESIS RESEARCH 1990; 26:69-85. [PMID: 24420459 DOI: 10.1007/bf00047078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/1990] [Accepted: 06/08/1990] [Indexed: 06/03/2023]
Abstract
Studies demonstrating differences in chloroplast structure and biochemistry have been used to formulate hypotheses concerning the origin of algal plastids. Genetic and biochemical experiments indicate that significant variation occurs in ribulose-1,5-bisphosphate carboxylase (Rubisco) when supertaxa of eukaryotic algae are compared. These differences include variations in the organelle location of the genes and their arrangement, mechanism of Rubisco synthesis, polypeptide immunological reactivity and sequence, as well as efficacy of substrate (ribulose bisphosphate and CO2) binding and inhibitor (6-phosphogluconate) action. The structure-function relationships observed among chromophytic, rhodophytic, chlorophytic and prokaryotic Rubisco demonstrate that: (a) similarities among chromophytic and rhodophytic Rubisco exist in substrate/inhibitor binding and polypeptide sequence, (b) characteristic differences in enzyme kinetics and subunit polypeptide structure occur among chlorophytes, prokaryotes and chromophytes/rhodophytes, and (c) there is structural variability among chlorophytic plant small subunit polypeptides, in contrast to the conservation of this polypeptide in chromophytes and rhodophytes. Taxa-specific differences among algal Rubisco enzymes most likely reflect the evolutionary history of the plastid, the functional requirements of each polypeptide, and the consequences of encoding the large and small subunit genes in the same or different organelles.
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Affiliation(s)
- S M Newman
- Department of Botany, University of Washington, 98195, Seattle, WA, USA
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18
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Identification and characterization of a testis-specific isoform of a chaperonin in a moth, Heliothis virescens. J Mol Biol 1990; 214:407-22. [PMID: 1974308 DOI: 10.1016/0022-2836(90)90190-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Two relatively abundant proteins having subunit molecular weights of 60,000 and 63,000 (p60 and p63, respectively) have been purified as a 16 to 18S complex from sperm mitochondria of a moth. Heliothis virescens. Although the function of these proteins had heretofore not been established, interest in the p63 polypeptide stemmed from its sperm-specific expression and its striking occurrence as a net charge variant among several insect species surveyed, using two-dimensional gel electrophoresis. Genomic and cDNA clones corresponding to the p63 protein have now been isolated and their sequencing has revealed extensive amino acid sequence identity with both the Escherichia coli GroEL protein and its eukaryotic homologues, the chaperonins. Immunoblot studies with a Tetrahymena chaperonin antiserum demonstrated that the p60 protein, which is expressed in all cell types, is structurally related to p63 and is itself a chaperonin subunit. While the chaperonin complex from Heliothis sperm shares certain properties with GroEL, including the ability to hydrolyze ATP and organization of its subunits into a seven-member ring, electron microscopic analysis revealed that its higher-order structure differed from GroEL (and other lower eukaryotic chaperonins) in that the native particle comprises one such ring rather than a doublet. It is not yet known whether the two chaperonin isoforms coexpressed in moth sperm assemble separately or give rise to hybrid particles. In either case, the existence of multiple chaperonin subunits in sperm leaves open the possibility that some aspect of mitochondrial biogenesis that is dependent upon the activity of these proteins is qualitatively or quantitatively different in this cell type.
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19
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Lubben TH, Donaldson GK, Viitanen PV, Gatenby AA. Several proteins imported into chloroplasts form stable complexes with the GroEL-related chloroplast molecular chaperone. THE PLANT CELL 1989; 1:1223-1230. [PMID: 2577724 PMCID: PMC159857 DOI: 10.1105/tpc.1.12.1223] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Nine different proteins were imported into isolated pea chloroplasts in vitro. For seven of these [the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), beta-subunit of ATP synthase, glutamine synthetase, the light-harvesting chlorophyll a/b binding protein, chloramphenicol acetyltransferase, and pre-beta-lactamase], a fraction was found to migrate as a stable high-molecular-weight complex during nondenaturing gel electrophoresis. This complex contained the mature forms of the imported proteins and the groEL-related chloroplast chaperonin 60 (previously known as Rubisco subunit binding protein). Thus, the stable association of imported proteins with this molecular chaperone is widespread and not necessarily restricted to Rubisco subunits or to chloroplast proteins. With two of the imported proteins (ferredoxin and superoxide dismutase), such complexes were not observed. It seems likely that, in addition to its proposed role in assembly of Rubisco, the chloroplast chaperonin 60 is involved in the assembly or folding of a wide range of proteins in chloroplasts.
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Affiliation(s)
- T H Lubben
- Molecular Biology Division, E.I. DuPont de Nemours & Co., Wilmington, Delaware 19880-0402
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20
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Abstract
Subcellular compartments in which folding and assembly of proteins occur seem to have a set of PCB proteins capable of mediating these and related processes, such as translocation across membranes. When a domain of a polypeptide chain emerges from a ribosome during synthesis or from the distal side of a membrane during translocation, successive segments of the chain are incrementally exposed to solvent and yet are unlikely to be able to fold. This topological restriction on folding likely mandates a need for PCB proteins to prevent aggregation. Catalysis of topologically restricted folding by PCB proteins is likely to involve both an antifolding activity that postpones folding until entire domains are available and, more speculatively, a folding activity resulting from a programmed stepwise release that employs the energy of ATP hydrolysis to ensure a favorable pathway. We are left with a new set of problems. How do proteins fold in cells? What are the sequences or structural signals that dictate folding pathways? The new challenge will be to understand folding as a combination of physical chemistry, enzymology, and cell biology.
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Affiliation(s)
- J E Rothman
- Department of Biology, Princeton University, New Jersey 08544
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21
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Roy H. Rubisco assembly: a model system for studying the mechanism of chaperonin action. THE PLANT CELL 1989; 1:1035-1042. [PMID: 2577726 PMCID: PMC159840 DOI: 10.1105/tpc.1.11.1035] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- H Roy
- Plant Science Group, Biology Department, Rensselaer Polytechnic Institute, Troy, New York 12180
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22
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Prasad TK, Hallberg RL. Identification and metabolic characterization of the Zea mays mitochondrial homolog of the Escherichia coli groEL protein. PLANT MOLECULAR BIOLOGY 1989; 12:609-618. [PMID: 24271194 DOI: 10.1007/bf00044152] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/1988] [Accepted: 02/06/1989] [Indexed: 06/02/2023]
Abstract
We have characterized an abundant mitochondrial protein from Zea mays and have shown it to be structurally and metabolically indistinguishable from a previously described Tetrahymena thermophila and Saccharomyces cerevisiae mitochondrial protein, referred to as hsp60, which is homologous to the groEL protein of Escherichia coli. This Z. mays protein, which we also refer to as hsp60, was found to be antigenically quite distinct from the chloroplast Rubisco-binding protein, another groEL homolog. Using an antiserum directed against the T. thermophila hsp60, we determined that the relative concentration of Z. mays hsp60 was two to four times higher in mitochondria isolated from tissues of early developmental stages than that found in mitochondria isolated from more adult tissues. Given the known and suggested roles of the other members of the groEL family of proteins, our results suggest that the Z. mays hsp60 may play an important role in mitochondrial biogenesis during early plant development.
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Affiliation(s)
- T K Prasad
- Department of Zoology, Iowa State University, 50011, Ames, Iowa, USA
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23
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Landry SJ, Bartlett SG. The Small Subunit of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase and its Precursor Expressed in Escherichia coli Are Associated with groEL Protein. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)81906-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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24
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Chaudhari P, Roy H. Delayed Osmotic Effect on in Vitro Assembly of RuBisCO : Relationship to Large Subunit-Binding Protein Complex Dissociation. PLANT PHYSIOLOGY 1989; 89:1366-71. [PMID: 16666711 PMCID: PMC1056023 DOI: 10.1104/pp.89.4.1366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Higher plant ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) cannot reassociate after dissociation, and its subunits do not assemble into active RuBisCO when synthesized in Escherichia coli. Newly synthesized subunits of RuBisCO are associated with a high molecular weight binding protein complex in pea chloroplasts. The immediate donor for large subunits which assemble into RuBisCO is a low molecular weight complex which may be derived from the high molecular weight binding protein complex. When the high molecular weight binding protein complex is diluted, it tends to dissociate, forming low molecular weight complexes. When the large subunit-binding protein complexes were examined after in organello protein synthesis, it was found that the low molecular weight complexes were more abundant when protein synthesis was carried out under hypotonic conditions. This increase in the assembly competent population of low molecular weight large subunit complexes can account for the increased amount of in vitro RuBisCO assembly which occurs under these conditions. The data indicate that the assembly of large subunits into RuBisCO is a function of the aggregation state of the large subunit binding protein complex during protein synthesis. This implies that the binding protein exerts its effects during or shortly after large subunit synthesis.
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Affiliation(s)
- P Chaudhari
- Plant Science Group, Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12180-3590
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25
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Reading DS, Hallberg RL, Myers AM. Characterization of the yeast HSP60 gene coding for a mitochondrial assembly factor. Nature 1989; 337:655-9. [PMID: 2563898 DOI: 10.1038/337655a0] [Citation(s) in RCA: 284] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The hsp60 protein isolated from the protozoan Tetrahymena thermophila is induced in response to heat stress and is a member of an immunologically conserved family represented in Escherichia coli and in mitochondria of plants and animals. We report here the cloning and characterization of a nuclear gene, HSP60, which codes for the hsp60 homologue from the yeast Saccharomyces cerevisiae. Nucleotide sequence analysis revealed that yeast hsp60 is related to the groEL protein of E. coli and the RUBISCO-binding protein (RBP) of chloroplasts. HSP60 was found to be the genetic locus of the conditional-lethal mutation described by Cheng et al., which at non-permissive temperature is defective in the assembly of several different multisubunit complexes in mitochondria. These data are consistent with the hypothesis that the groEL-related proteins serve an evolutionarily conserved function as accessory factors facilitating the folding and/or association of individual subunits of multimeric protein complexes.
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Affiliation(s)
- D S Reading
- Department of Zoology, Iowa State University, Ames 50011
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26
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Holzenburg A, Mayer F. D-ribulose-1,5-bisphosphate carboxylase/oxygenase: function-dependent structural changes. ELECTRON MICROSCOPY REVIEWS 1989; 2:139-69. [PMID: 2491339 DOI: 10.1016/0892-0354(89)90014-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The key carboxylating enzyme of the reductive pentose phosphate cycle, D-ribulose-1,5-bisphosphate carboxylase/oxygenase [RuBisCO] isolated from the chemolithoautotrophic, H2-oxidizing bacterium Alcaligenes eutrophus H16 has been analyzed by several different techniques that allow conclusions about structure and function-dependent structural changes. The techniques include a novel approach in which the enzyme was induced to form 2D-crystals suitable for electron microscopy in each of its three stable functional states: as active enzyme [Ea] (in the presence of Mg2+ and HCO3-); as inactivated enzyme [Eia] (in the absence of Mg2+ and HCO3-) and as enzyme locked in an in vitro transition state [CABP-E] (Ea fully saturated with the transition state analogue 2-carboxy-D-arabinitol-1,5-bisphosphate [CABP-E]). In conjunction with X-ray crystallography, X-ray small angle scattering and other biophysical and biochemical data, the results obtained by electron microscopy support the idea that drastic configurational changes occur. Upon transition from Ea to the CABP-E the upper and lower L4S4 halves of the molecule consisting of eight large and eight small subunits (L8S8; MW = 536,000 Da) are assumed to be laterally shifted by as much as 3.6 nm relative to one another while the location of the small subunits on top of the large subunits, and relative to them, remains the same. For the Eia a similar sliding-layer configurational change in the range of 2-2.5 nm is proposed and in addition it is suggested that other configurational/conformational changes take place. The proposed structural changes are discussed with respect to the current model for the tobacco enzyme and correlated with data obtained for various other plant and (cyano) bacterial L8S8 RuBisCOs leading to speculations about structure-function relationships.
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Affiliation(s)
- A Holzenburg
- Institut für Mikrobiologie der Georg-August-Universität Göttingen, F.R.G
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27
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Roy H, Cannon S, Gilson M. Assembly of Rubisco from native subunits. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 957:323-34. [PMID: 3058207 DOI: 10.1016/0167-4838(88)90221-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Large subunits of ribulosebisphosphate carboxylase/oxygenase (Rubisco) (3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39) from prokaryotic sources can assemble into intact enzyme either in vitro or in Escherichia coli cells. Large subunits of higher plant Rubisco do not assemble into Rubisco in E. coli cells, nor is it possible to reconstitute higher plant Rubisco from its dissociated subunits in vitro. This behavior represents an obstacle to any practical attempts at engineering the higher plant enzyme, and it suggests that the in vivo assembly mechanism of higher plant Rubisco must be more complex than is commonly expected for oligomeric proteins of organelles. In pea chloroplasts, a binding protein interacts with newly synthesized large subunits, in quantities expected for an intermediate in the assembly process, as judged by Western blotting. Radiotracer-labeled large subunits which interact with this binding protein can be shown to assemble into Rubisco in reactions which lead to changes in the aggregation state of the binding protein. Antibody to this binding protein specifically inhibits the assembly of these subunits into Rubisco. Rubisco synthesis appears to be subject to many types of control: gene dosage, transcription rate, selective translation of message, post-translational degradation and threshold concentration effects have been observed in various organisms' synthesis of Rubisco. The biochemical mechanisms underlying most of these effects have not been elucidated. The post-translational assembly mechanism in particular appears to require further study.
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Affiliation(s)
- H Roy
- Biology Department, Rensselaer Polytechnic Institute, Troy, NY 12180-3590
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28
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Rodermel SR, Abbott MS, Bogorad L. Nuclear-organelle interactions: nuclear antisense gene inhibits ribulose bisphosphate carboxylase enzyme levels in transformed tobacco plants. Cell 1988; 55:673-81. [PMID: 3052855 DOI: 10.1016/0092-8674(88)90226-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The biosynthesis of ribulose bisphosphate carboxylase (RUBISCO) provides a model system for studying the coordination of nuclear and organelle gene expression, since this abundantly transcribed and expressed chloroplast enzyme is composed of small (SS) and large subunits (LS) encoded by a nuclear multigene family and a single chloroplast gene, respectively. We have tested the possibility that SS mRNA or protein levels affect LS mRNA amounts or LS protein production and accumulation. We find that expression of antisense DNA sequences for the SS in transgenic tobacco plants drastically reduces the accumulation of SS mRNA and SS protein. These changes are accompanied by corresponding reductions of LS protein but not LS mRNA amounts; accumulation of the LS protein appears to be regulated by translational and posttranslational factors. We also find that the transgenic plants display striking variations in growth that are correlated with antisense gene dosage.
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Affiliation(s)
- S R Rodermel
- Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138
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29
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Newman S, Cattolico RA. Synthesis of active Olisthodiscus luteus ribulose-1,5-bisphosphate carboxylase in Escherichia coli. PLANT MOLECULAR BIOLOGY 1988; 11:821-831. [PMID: 24272632 DOI: 10.1007/bf00019522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/1988] [Accepted: 09/21/1988] [Indexed: 06/02/2023]
Abstract
The ribulose-1,5-bisphosphate carboxylase (Rubisco) large- and small-subunit genes are encoded on the chloroplast genome of the eukaryotic chromophytic alga Olisthodiscus luteus. Northern blot experiments indicate that both genes are co-transcribed into a single (>6 kb) mRNA molecule. Clones from the O. luteus rbc gene region were constructed with deleted 5' non-coding regions and placed under control of the lac promoter, resulting in the expression of high levels of O. luteus Rubisco large and small subunits in Escherichia coli. Sucrose gradient centrifugation of soluble extracts fractionated a minute amount of carboxylase activity that cosedimented with native hexadecameric O. luteus Rubisco. Most of the large subunit synthesized in E. coli appeared insoluble or formed an aggregate with the small subunit possessing an altered charge: mass ratio compared to the native holoenzyme. The presence in O. luteus of a polypeptide that has an identical molecular mass and cross reacts with antiserum generated against pea large-subunit binding protein may indicate that a protein of similar function is required for Rubisco assembly in O. luteus.
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Affiliation(s)
- S Newman
- Department of Botany KB-15, University of Washington, 98195, Seattle, WA, USA
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30
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Hemmingsen SM, Woolford C, van der Vies SM, Tilly K, Dennis DT, Georgopoulos CP, Hendrix RW, Ellis RJ. Homologous plant and bacterial proteins chaperone oligomeric protein assembly. Nature 1988; 333:330-4. [PMID: 2897629 DOI: 10.1038/333330a0] [Citation(s) in RCA: 931] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
An abundant chloroplast protein is implicated in the assembly of the oligomeric enzyme ribulose bisphosphate carboxylase-oxygenase, which catalyses photosynthetic CO2-fixation in higher plants. The product of the Escherichia coli groEL gene is essential for cell viability and is required for the assembly of bacteriophage capsids. Sequencing of the groEL gene and the complementary cDNA encoding the chloroplast protein has revealed that these proteins are evolutionary homologues which we term 'chaperonins'. Chaperonins comprise a class of molecular chaperones that are found in chloroplasts, mitochondria and prokaryotes. Assisted post-translational assembly of oligomeric protein structures is emerging as a general cellular phenomenon.
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Affiliation(s)
- S M Hemmingsen
- Plant Biotechnology Institute, National Research Council, Saskatoon, Saskatchewan, Canada
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31
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Roy H, Cannon S. Ribulose bisphosphate carboxylase assembly: what is the role of the large subunit binding protein? Trends Biochem Sci 1988; 13:163-5. [PMID: 3255196 DOI: 10.1016/0968-0004(88)90139-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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32
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Ellis RJ, Van Der Vies SM. The Rubisco subunit binding protein. PHOTOSYNTHESIS RESEARCH 1988; 16:101-115. [PMID: 24430994 DOI: 10.1007/bf00039488] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/1987] [Accepted: 09/30/1987] [Indexed: 06/03/2023]
Abstract
Chloroplasts contain an abundant soluble protein that binds non-covalently newly synthesized large and small subunits of the enzyme ribulose bisphosphate carboxylase-oxygenase. This binding protein has been purified from Pisum sativum and Hordeum vulgare in the form of a dodecamer consisting of equal amounts of two types of subunit. These subunits are synthesized as higher molecular mass precursors by cytoplasmic ribosomes before import into the chloroplast. Antibodies raised against the purified binding protein from Pisum sativum detect polypeptides not only in extracts of plastids from several plant species but also in cell extracts of several bacterial species. The oligomeric binding protein dissociates reversibly into monomeric subunits in the presence of 1-5 mmol/liter MgATP. For one type of subunit the cDNA sequence has been isolated and determined and reveals homology with certain bacterial proteins.These observations are discussed in relation to the idea that the binding protein is an example of a general class of proteins termed "molecular chaperones" which are required for the correct assembly of certain oligomeric proteins such as the carboxylase from their subunits.
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Affiliation(s)
- R J Ellis
- Department of Biological Sciences, University of Warwick, CV4 7AL, Coventry, UK
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33
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Roy H, Hubbs A, Cannon S. Stability and Dissociation of the Large Subunit RuBisCO Binding Protein Complex in Vitro and in Organello. PLANT PHYSIOLOGY 1988; 86:50-3. [PMID: 16665892 PMCID: PMC1054426 DOI: 10.1104/pp.86.1.50] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
We are studying the stability of the binding protein which associates with newly synthesized large subunits of ribulose bisphosphate carboxylase. In chloroplast extracts, it has been shown that a dodecameric complex of the large subunit binding protein dissociates extensively into binding protein monomers and 7S (117 kilodaltons) large subunit-containing complexes in the presence of ATP. The concentrations of ATP which bring this about are quite low, prompting some investigators to suggest that the dodecameric complex might not exist in vivo. We have found, however, that in concentrated chloroplast extracts, at protein concentrations which are closer to those which occur in organello, the dissociation of the binding protein complex by ATP is much less extensive. For this reason, we have tested the stability of the binding protein in organello, by illuminating chloroplasts followed by lysis and polyacrylamide gel electrophoresis of the extracts. Radioactive large subunits associated with the dodecameric binding protein dissociated extensively in the light. The results are consistent with the idea that the high molecular weight form of the binding protein can function as a reservoir of large subunits which can be tapped in vivo, in a reaction dependent on light and ATP.
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Affiliation(s)
- H Roy
- Plant Science Group, Biology Department, Rensselaer Polytechnic Institute, Troy, New York, 12180-3590
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34
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Roy H, Chaudhari P, Cannon S. Incorporation of Large Subunits into Ribulose Bisphosphate Carboxylase in Chloroplast Extracts : Influence of Added Small Subunits and of Conditions during Synthesis. PLANT PHYSIOLOGY 1988; 86:44-9. [PMID: 16665891 PMCID: PMC1054425 DOI: 10.1104/pp.86.1.44] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The incorporation of newly synthesized large subunits into ribulose bisphosphate carboxylase/oxygenase (RuBisCO) in pea chloroplast extracts occurs at the expense of intermediate forms of the large subunit which are complexed with a binding protein. Most subunits of this binding protein are found in dodecameric complexes in chloroplast extracts. Addition of small subunits to these extracts results in approximately 40 to 60% increased incorporation of newly made large subunits into RuBisCO at low or zero concentrations of ATP, but is without significant effect at high concentrations of ATP, a condition in which the dodecameric binding protein complex is dissociated into subunits. Overall, these data support the assumption that the incorporation of large subunits into RuBisCO in chloroplast extracts reflects de novo assembly rather than ;mere' exchange of subunits. The in vitro assembly of large subunits into RuBisCO is a function of the conditions under which the large subunits are synthesized in organello. When the large subunits are made in chloroplasts suspended in 188 millimolar sorbitol, they are approximately 2- to 3-fold better able to assemble into RuBisCO when subsequently incubated in vitro than when they are synthesized in chloroplasts suspended in 375 millimolar sorbitol. This observation indicates that mere synthesis of large subunits is not sufficient to confer maximal assembly competence on large subunits.
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Affiliation(s)
- H Roy
- Plant Science Group, Biology Department, Rensselaer Polytechnic Institute, Troy, New York, 12180-3590
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35
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Strzalka K, Ngernprasirtsiri J, Watanabe A, Akazawa T. Sycamore amyloplasts can import and process precursors of nuclear encoded chloroplast proteins. Biochem Biophys Res Commun 1987; 149:799-806. [PMID: 3322282 DOI: 10.1016/0006-291x(87)90438-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Amyloplasts isolated from white-wild suspension-cultured cells of sycamore (Acer pseudoplatanus L.) are found to import and process the precursor of the small subunit (pS) of ribulose-1,5-bisphosphate carboxylase/oxygenase of spinach, but they lack the ability to form its holoenzyme due to the absence of both the large subunit and its binding-protein. They also import the precursor of the 33-kDa extrinsic protein (p33-kDa) of the O2-evolving complex of Photosystem II from spinach, but process is only to an intermediate form (i33-kDa). Chloroplasts from green-mutant cells of sycamore process p33-kDa to its mature form in this heterologous system. These results suggest that the thylakoid-associated protease responsible for the second processing step of p33-kDa is missing in amyloplasts, possibly due to the absence of thylakoid-membranes. In contrast, the apparent import of the precursor of the light-harvesting chlorophyll a/b-binding apoprotein (pLHCP) from spinach was not detected. Sycamore amyloplasts may lack the ability to import this particular thylakoid-protein, or rapidly degrade the imported molecules in the absence of thylakoid-membranes for their proper insertion.
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Affiliation(s)
- K Strzalka
- Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Japan
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36
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Radetzky R, Zetsche K. Effects of specific inhibitors on the coordination of the concentrations of ribulose-bisphosphate-carboxylase subunits and their corresponding mRNAs in the alga Chlorogonium. PLANTA 1987; 172:38-46. [PMID: 24225785 DOI: 10.1007/bf00403026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/1987] [Accepted: 04/10/1987] [Indexed: 06/02/2023]
Abstract
Investigations were carried out on the effects of inhibitors of transcription and translation on the concentrations of the subunits of the plastid enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCase) and their corresponding mRNAs in the unicellular green alga Chlorogonium elongatum Dangeard. The light-induced increase of nuclear-coded small-subunit mRNA was strongly inhibited by α-amanitin while the increase of plastid-coded large-subunit mRNA was only weakly affected: Consequently, the mRNAs of the two subunits were present in very different proportions. Nevertheless, the light-induced increase of both subunits was strongly reduced by α-amanitin to the same degree, and hence the ratio of their concentrations was not affected compared with the untreated control cells. The effect of cycloheximide on the subunit mRNAs was similar to but weaker than that of α-amanitin. Again the increases in the subunit levels were strongly inhibited to the same degree. By contrast, rifampicin and chloramphenicol inhibited the light-induced increase of large-subunit mRNA more strongly than that of small-subunit mRNA, but the differences were less distinct than those caused by α-amanitin and cycloheximide. Again, the increase in both subunits was inhibited almost to the same extent. These results - especially those of the α-amanitin experiments - clearly show that the fine coordination of the RuBPCase subunits occurs posttranscriptionally at the level of translation and-or degradation. This conclusion was confirmed by pulse-chase experiments. Inhibition of the synthesis of the large subunits by chloramphenicol resulted - as also found by other authors-in a degradation of excess small subunits in the plastid. On the other hand, inhibition of the concentration of small subunits caused a proportionate reduction in the synthesis of large subunits, but no rapid degradation of large subunits could be detected. Therefore, the fine coordination of both subunits of RuBPCase is achieved by the degradation of an excess of small subunits, while the level of large subunits is adapted to the small subunit concentration, probably by adjustment of translation of the large-subunit mRNA. Furthermore, our experiments with α-amanitin and cycloheximide allow us to conclude that in the blue-light induction of large-subunit mRNA in the plastid the nucleocytoplasmic compartment is not directly involved.
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Affiliation(s)
- R Radetzky
- Institut für Pflanzenphysiologie der Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, D-6300, Gießen, Federal Republic of Germany
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