1
|
Recent developments in the engineering of Rubisco activase for enhanced crop yield. Biochem Soc Trans 2023; 51:627-637. [PMID: 36929563 DOI: 10.1042/bst20221281] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 03/01/2023] [Accepted: 03/03/2023] [Indexed: 03/18/2023]
Abstract
Rubisco activase (RCA) catalyzes the release of inhibitory sugar phosphates from ribulose-1,6-biphosphate carboxylase/oxygenase (Rubisco) and can play an important role in biochemical limitations of photosynthesis under dynamic light and elevated temperatures. There is interest in increasing RCA activity to improve crop productivity, but a lack of understanding about the regulation of photosynthesis complicates engineering strategies. In this review, we discuss work relevant to improving RCA with a focus on advances in understanding the structural cause of RCA instability under heat stress and the regulatory interactions between RCA and components of photosynthesis. This reveals substantial variation in RCA thermostability that can be influenced by single amino acid substitutions, and that engineered variants can perform better in vitro and in vivo under heat stress. In addition, there are indications RCA activity is controlled by transcriptional, post-transcriptional, post-translational, and spatial regulation, which may be important for balancing between carbon fixation and light capture. Finally, we provide an overview of findings from recent field experiments and consider the requirements for commercial validation as part of efforts to increase crop yields in the face of global climate change.
Collapse
|
2
|
Waheeda K, Kitchel H, Wang Q, Chiu PL. Molecular mechanism of Rubisco activase: Dynamic assembly and Rubisco remodeling. Front Mol Biosci 2023; 10:1125922. [PMID: 36845545 PMCID: PMC9951593 DOI: 10.3389/fmolb.2023.1125922] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 01/31/2023] [Indexed: 02/12/2023] Open
Abstract
Ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase (Rubisco) enzyme is the limiting step of photosynthetic carbon fixation, and its activation is regulated by its co-evolved chaperone, Rubisco activase (Rca). Rca removes the intrinsic sugar phosphate inhibitors occupying the Rubisco active site, allowing RuBP to split into two 3-phosphoglycerate (3PGA) molecules. This review summarizes the evolution, structure, and function of Rca and describes the recent findings regarding the mechanistic model of Rubisco activation by Rca. New knowledge in these areas can significantly enhance crop engineering techniques used to improve crop productivity.
Collapse
Affiliation(s)
- Kazi Waheeda
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States
| | - Heidi Kitchel
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States
| | - Quan Wang
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Po-Lin Chiu
- School of Molecular Sciences, Arizona State University, Tempe, AZ, United States
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, United States
| |
Collapse
|
3
|
Mao Y, Catherall E, Díaz-Ramos A, Greiff GRL, Azinas S, Gunn L, McCormick AJ. The small subunit of Rubisco and its potential as an engineering target. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:543-561. [PMID: 35849331 PMCID: PMC9833052 DOI: 10.1093/jxb/erac309] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/07/2022] [Indexed: 05/06/2023]
Abstract
Rubisco catalyses the first rate-limiting step in CO2 fixation and is responsible for the vast majority of organic carbon present in the biosphere. The function and regulation of Rubisco remain an important research topic and a longstanding engineering target to enhance the efficiency of photosynthesis for agriculture and green biotechnology. The most abundant form of Rubisco (Form I) consists of eight large and eight small subunits, and is found in all plants, algae, cyanobacteria, and most phototrophic and chemolithoautotrophic proteobacteria. Although the active sites of Rubisco are located on the large subunits, expression of the small subunit regulates the size of the Rubisco pool in plants and can influence the overall catalytic efficiency of the Rubisco complex. The small subunit is now receiving increasing attention as a potential engineering target to improve the performance of Rubisco. Here we review our current understanding of the role of the small subunit and our growing capacity to explore its potential to modulate Rubisco catalysis using engineering biology approaches.
Collapse
Affiliation(s)
- Yuwei Mao
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - Ella Catherall
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - Aranzazú Díaz-Ramos
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - George R L Greiff
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Stavros Azinas
- Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden
| | - Laura Gunn
- Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
| | - Alistair J McCormick
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| |
Collapse
|
4
|
Flecken M, Wang H, Popilka L, Hartl FU, Bracher A, Hayer-Hartl M. Dual Functions of a Rubisco Activase in Metabolic Repair and Recruitment to Carboxysomes. Cell 2020; 183:457-473.e20. [PMID: 32979320 DOI: 10.1016/j.cell.2020.09.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/13/2020] [Accepted: 09/01/2020] [Indexed: 01/19/2023]
Abstract
Rubisco, the key enzyme of CO2 fixation in photosynthesis, is prone to inactivation by inhibitory sugar phosphates. Inhibited Rubisco undergoes conformational repair by the hexameric AAA+ chaperone Rubisco activase (Rca) in a process that is not well understood. Here, we performed a structural and mechanistic analysis of cyanobacterial Rca, a close homolog of plant Rca. In the Rca:Rubisco complex, Rca is positioned over the Rubisco catalytic site under repair and pulls the N-terminal tail of the large Rubisco subunit (RbcL) into the hexamer pore. Simultaneous displacement of the C terminus of the adjacent RbcL opens the catalytic site for inhibitor release. An alternative interaction of Rca with Rubisco is mediated by C-terminal domains that resemble the small Rubisco subunit. These domains, together with the N-terminal AAA+ hexamer, ensure that Rca is packaged with Rubisco into carboxysomes. The cyanobacterial Rca is a dual-purpose protein with functions in Rubisco repair and carboxysome organization.
Collapse
Affiliation(s)
- Mirkko Flecken
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Huping Wang
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Leonhard Popilka
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Andreas Bracher
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| |
Collapse
|
5
|
Probing the rice Rubisco-Rubisco activase interaction via subunit heterooligomerization. Proc Natl Acad Sci U S A 2019; 116:24041-24048. [PMID: 31712424 DOI: 10.1073/pnas.1914245116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
During photosynthesis the AAA+ protein and essential molecular chaperone Rubisco activase (Rca) constantly remodels inhibited active sites of the CO2-fixing enzyme Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) to release tightly bound sugar phosphates. Higher plant Rca is a crop improvement target, but its mechanism remains poorly understood. Here we used structure-guided mutagenesis to probe the Rubisco-interacting surface of rice Rca. Mutations in Ser-23, Lys-148, and Arg-321 uncoupled adenosine triphosphatase and Rca activity, implicating them in the Rubisco interaction. Mutant doping experiments were used to evaluate a suite of known Rubisco-interacting residues for relative importance in the context of the functional hexamer. Hexamers containing some subunits that lack the Rubisco-interacting N-terminal domain displayed a ∼2-fold increase in Rca function. Overall Rubisco-interacting residues located toward the rim of the hexamer were found to be less critical to Rca function than those positioned toward the axial pore. Rca is a key regulator of the rate-limiting CO2-fixing reactions of photosynthesis. A detailed functional understanding will assist the ongoing endeavors to enhance crop CO2 assimilation rate, growth, and yield.
Collapse
|
6
|
Yao X, Tan YH, Yang JB, Wang Y, Corlett RT, Manen JF. Exceptionally high rates of positive selection on the rbcL gene in the genus Ilex (Aquifoliaceae). BMC Evol Biol 2019; 19:192. [PMID: 31638910 PMCID: PMC6805373 DOI: 10.1186/s12862-019-1521-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 09/27/2019] [Indexed: 12/26/2022] Open
Abstract
Background The genus Ilex (Aquifoliaceae) has a near-cosmopolitan distribution in mesic habitats from tropical to temperate lowlands and in alpine forests. It has a high rate of hybridization and plastid capture, and comprises four geographically structured plastid groups. A previous study showed that the plastid rbcL gene, coding for the large subunit of Rubisco, has a particularly high rate of non-synonymous substitutions in Ilex, when compared with other plant lineages. This suggests a strong positive selection on rbcL, involved in yet unknown adaptations. We therefore investigated positive selection on rbcL in 240 Ilex sequences from across the global range. Results The rbcL gene shows a much higher rate of positive selection in Ilex than in any other plant lineage studied so far (> 3000 species) by tests in both PAML and SLR. Most positively selected residues are on the surface of the folded large subunit, suggesting interaction with other subunits and associated chaperones, and coevolution between positively selected residues is prevalent, indicating compensatory mutations to recover molecular stability. Coevolution between positively selected sites to restore global stability is common. Conclusions This study has confirmed the predicted high incidence of positively selected residues in rbcL in Ilex, and shown that this is higher than in any other plant lineage studied so far. The causes and consequences of this high incidence are unclear, but it is probably associated with the similarly high incidence of hybridization and introgression in Ilex, even between distantly related lineages, resulting in large cytonuclear discordance in the phylogenies.
Collapse
Affiliation(s)
- Xin Yao
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China. .,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, China.
| | - Yun-Hong Tan
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China.,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, China.,Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Yezin, Nay Pyi Taw, Myanmar
| | - Jun-Bo Yang
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Yan Wang
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China
| | - Richard T Corlett
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China. .,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, China.
| | - Jean-François Manen
- Laboratoire de Systématique Végétale et Biodiversité, University of Geneva (retired), Chemin de l'Impératrice 1, CH-1292, Chambésy, Switzerland.
| |
Collapse
|
7
|
Wilson RH, Thieulin-Pardo G, Hartl FU, Hayer-Hartl M. Improved recombinant expression and purification of functional plant Rubisco. FEBS Lett 2019; 593:611-621. [PMID: 30815863 PMCID: PMC6593764 DOI: 10.1002/1873-3468.13352] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 02/24/2019] [Accepted: 02/25/2019] [Indexed: 12/22/2022]
Abstract
Improving the performance of the key photosynthetic enzyme Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) by protein engineering is a critical strategy for increasing crop yields. The extensive chaperone requirement of plant Rubisco for folding and assembly has long been an impediment to this goal. Production of plant Rubisco in Escherichia coli requires the coexpression of the chloroplast chaperonin and four assembly factors. Here, we demonstrate that simultaneous expression of Rubisco and chaperones from a T7 promotor produces high levels of functional enzyme. Expressing the small subunit of Rubisco with a C-terminal hexahistidine-tag further improved assembly, resulting in a ~ 12-fold higher yield than the previously published procedure. The expression system described here provides a platform for the efficient production and engineering of plant Rubisco.
Collapse
Affiliation(s)
- Robert H Wilson
- Chaperonin-assisted Protein Folding Group, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Gabriel Thieulin-Pardo
- Chaperonin-assisted Protein Folding Group, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Franz-Ulrich Hartl
- Cellular Biochemistry Group, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Manajit Hayer-Hartl
- Chaperonin-assisted Protein Folding Group, Max Planck Institute of Biochemistry, Martinsried, Germany
| |
Collapse
|
8
|
Serban AJ, Breen IL, Bui HQ, Levitus M, Wachter RM. Assembly-disassembly is coupled to the ATPase cycle of tobacco Rubisco activase. J Biol Chem 2018; 293:19451-19465. [PMID: 30352875 PMCID: PMC6302163 DOI: 10.1074/jbc.ra118.005047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/09/2018] [Indexed: 11/06/2022] Open
Abstract
The carbon-fixing activity of enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is regulated by Rubisco activase (Rca), a ring-forming ATPase that catalyzes inhibitor release. For higher plant Rca, the catalytic roles played by different oligomeric species have remained obscure. Here, we utilized fluorescence-correlation spectroscopy to estimate dissociation constants for the dimer-tetramer, tetramer-hexamer, hexamer-12-mer, and higher-order assembly equilibria of tobacco Rca. A comparison of oligomer composition with ATPase activity provided evidence that assemblies larger than hexamers are hydrolytically inactive. Therefore, supramolecular aggregates may serve as storage forms at low-energy charge. We observed that the tetramer accumulates only when both substrate and product nucleotides are bound. During rapid ATP turnover, about one in six active sites was occupied by ADP, and ∼36% of Rca was tetrameric. The steady-state catalytic rate reached a maximum between 0.5 and 2.5 μm Rca. In this range, significant amounts of dimers, tetramers, and hexamers coexisted, although none could fully account for the observed activity profile. Therefore, we propose that dynamic assembly-disassembly partakes in the ATPase cycle. According to this model, the association of dimers with tetramers generates a hexamer that forms a closed ring at high ATP and magnesium levels. Upon hydrolysis and product release, the toroid breaks open and dissociates into a dimer and tetramer, which may be coupled to Rubisco remodeling. Although a variant bearing the R294V substitution assembled in much the same way, highly stabilized states could be generated by binding of a transition-state analog. A tight-binding pre-hydrolysis state appears to become more accessible in thermally labile Rcas.
Collapse
Affiliation(s)
- Andrew J Serban
- From the School of Molecular Sciences
- Center for Bioenergy and Photosynthesis
- Biodesign Center for Applied Structural Discovery, and
| | - Isabella L Breen
- From the School of Molecular Sciences
- Center for Bioenergy and Photosynthesis
- Biodesign Center for Applied Structural Discovery, and
| | - Hoang Q Bui
- From the School of Molecular Sciences
- Center for Bioenergy and Photosynthesis
- Biodesign Center for Applied Structural Discovery, and
| | - Marcia Levitus
- From the School of Molecular Sciences,
- the Biodesign Center for Single Molecule Biophysics, Arizona State University, Tempe, Arizona 85287
| | - Rebekka M Wachter
- From the School of Molecular Sciences,
- Center for Bioenergy and Photosynthesis
- Biodesign Center for Applied Structural Discovery, and
| |
Collapse
|
9
|
Pottier M, Gilis D, Boutry M. The Hidden Face of Rubisco. TRENDS IN PLANT SCIENCE 2018; 23:382-392. [PMID: 29525130 DOI: 10.1016/j.tplants.2018.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 01/28/2018] [Accepted: 02/06/2018] [Indexed: 05/21/2023]
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) fixes atmospheric CO2 into organic compounds and is composed of eight copies each of a large subunit (RbcL) and a small subunit (RbcS). Recent reports have revealed unusual RbcS, which are expressed in particular tissues and confer higher catalytic rate, lesser affinity for CO2, and a more acidic profile of the activity versus pH. The resulting Rubisco was proposed to be adapted to a high CO2 environment and recycle CO2 generated by the metabolism. These RbcS belong to a cluster named T (for trichome), phylogenetically distant from cluster M, which gathers well-characterized RbcS expressed in mesophyll or bundle-sheath tissues. Cluster T is largely represented in different plant phyla, including pteridophytes and bryophytes, indicating an ancient origin.
Collapse
Affiliation(s)
- Mathieu Pottier
- Institut des Sciences de la Vie, University of Louvain, 1348 Louvain-la-Neuve, Belgium
| | - Dimitri Gilis
- Bioinformatique génomique et structurale, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Marc Boutry
- Institut des Sciences de la Vie, University of Louvain, 1348 Louvain-la-Neuve, Belgium.
| |
Collapse
|
10
|
Peterson-Forbrook DS, Hilton MT, Tichacek L, Henderson JN, Bui HQ, Wachter RM. Nucleotide Dependence of Subunit Rearrangements in Short-Form Rubisco Activase from Spinach. Biochemistry 2017; 56:4906-4921. [PMID: 28795566 DOI: 10.1021/acs.biochem.7b00574] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Higher-plant Rubisco activase (Rca) plays a critical role in regulating the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). In vitro, Rca is known to undergo dynamic assembly-disassembly processes, with several oligomer stoichiometries coexisting over a broad concentration range. Although the hexamer appears to be the active form, changes in quaternary structure could play a role in Rubisco regulation. Therefore, fluorescent labels were attached to the C-termini of spinach β-Rca, and the rate of subunit mixing was monitored by measuring energy transfer as a function of nucleotide and divalent cation. Only dimeric units appeared to exchange. Poorly hydrolyzable substrate analogues provided locked complexes with high thermal stabilities (apparent Tm = 60 °C) and an estimated t1/2 of at least 7 h, whereas ATP-Mg provided tight assemblies with t1/2 values of 30-40 min and ADP-Mg loose assemblies with t1/2 values of <15 min. Accumulation of ADP to 20% of the total level of adenine nucleotide substantially accelerated equilibration. An initial lag period was observed with ATP·Mg, indicating inhibition of subunit exchange at low ADP concentrations. The ADP Ki value was estimated to exceed the Km for ATP (0.772 ± 96 mM), suggesting that the equilibration rate is a function of the relative contributions of high- and low-affinity states. C-Terminal cross-linking generated covalent dimers, required the N-terminal extension to the AAA+ domain, and provided evidence of different classes of sites. We propose that oligomer reorganization may be stalled during periods of high Rubisco reactivation activity, whereas changes in quaternary structure are stimulated by the accumulation of ADP at low light levels.
Collapse
Affiliation(s)
- Dayna S Peterson-Forbrook
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | - Matthew T Hilton
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | - Laura Tichacek
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | - J Nathan Henderson
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | - Hoang Q Bui
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | - Rebekka M Wachter
- School of Molecular Sciences, School of Life Sciences, and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| |
Collapse
|
11
|
Bhat JY, Miličić G, Thieulin-Pardo G, Bracher A, Maxwell A, Ciniawsky S, Mueller-Cajar O, Engen JR, Hartl FU, Wendler P, Hayer-Hartl M. Mechanism of Enzyme Repair by the AAA + Chaperone Rubisco Activase. Mol Cell 2017; 67:744-756.e6. [PMID: 28803776 DOI: 10.1016/j.molcel.2017.07.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/07/2017] [Accepted: 07/01/2017] [Indexed: 01/16/2023]
Abstract
How AAA+ chaperones conformationally remodel specific target proteins in an ATP-dependent manner is not well understood. Here, we investigated the mechanism of the AAA+ protein Rubisco activase (Rca) in metabolic repair of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits containing eight catalytic sites. Rubisco is prone to inhibition by tight-binding sugar phosphates, whose removal is catalyzed by Rca. We engineered a stable Rca hexamer ring and analyzed its functional interaction with Rubisco. Hydrogen/deuterium exchange and chemical crosslinking showed that Rca structurally destabilizes elements of the Rubisco active site with remarkable selectivity. Cryo-electron microscopy revealed that Rca docks onto Rubisco over one active site at a time, positioning the C-terminal strand of RbcL, which stabilizes the catalytic center, for access to the Rca hexamer pore. The pulling force of Rca is fine-tuned to avoid global destabilization and allow for precise enzyme repair.
Collapse
Affiliation(s)
- Javaid Y Bhat
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Goran Miličić
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Gabriel Thieulin-Pardo
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Andreas Bracher
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Andrew Maxwell
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Susanne Ciniawsky
- Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Oliver Mueller-Cajar
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115-5000, USA
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Petra Wendler
- Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| |
Collapse
|
12
|
Mueller-Cajar O. The Diverse AAA+ Machines that Repair Inhibited Rubisco Active Sites. Front Mol Biosci 2017; 4:31. [PMID: 28580359 PMCID: PMC5437159 DOI: 10.3389/fmolb.2017.00031] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 04/29/2017] [Indexed: 11/13/2022] Open
Abstract
Gaseous carbon dioxide enters the biosphere almost exclusively via the active site of the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). This highly conserved catalyst has an almost universal propensity to non-productively interact with its substrate ribulose 1,5-bisphosphate, leading to the formation of dead-end inhibited complexes. In diverse autotrophic organisms this tendency has been counteracted by the recruitment of dedicated AAA+ (ATPases associated with various cellular activities) proteins that all use the energy of ATP hydrolysis to remodel inhibited Rubisco active sites leading to release of the inhibitor. Three evolutionarily distinct classes of these Rubisco activases (Rcas) have been discovered so far. Green and red-type Rca are mostly found in photosynthetic eukaryotes of the green and red plastid lineage respectively, whereas CbbQO is associated with chemoautotrophic bacteria. Ongoing mechanistic studies are elucidating how the various motors are utilizing both similar and contrasting strategies to ultimately perform their common function of cracking the inhibited Rubisco active site. The best studied mechanism utilized by red-type Rca appears to involve transient threading of the Rubisco large subunit C-terminal peptide, reminiscent of the action performed by Clp proteases. As well as providing a fascinating example of convergent molecular evolution, Rca proteins can be considered promising crop-improvement targets. Approaches aiming to replace Rubisco in plants with improved enzymes will need to ensure the presence of a compatible Rca protein. The thermolability of the Rca protein found in crop plants provides an opportunity to fortify photosynthesis against high temperature stress. Photosynthesis also appears to be limited by Rca when light conditions are fluctuating. Synthetic biology strategies aiming to enhance the autotrophic CO2 fixation machinery will need to take into consideration the requirement for Rubisco activases as well as their properties.
Collapse
Affiliation(s)
- Oliver Mueller-Cajar
- School of Biological Sciences, Nanyang Technological UniversitySingapore, Singapore
| |
Collapse
|
13
|
Bracher A, Whitney SM, Hartl FU, Hayer-Hartl M. Biogenesis and Metabolic Maintenance of Rubisco. ANNUAL REVIEW OF PLANT BIOLOGY 2017; 68:29-60. [PMID: 28125284 DOI: 10.1146/annurev-arplant-043015-111633] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) mediates the fixation of atmospheric CO2 in photosynthesis by catalyzing the carboxylation of the 5-carbon sugar ribulose-1,5-bisphosphate (RuBP). Rubisco is a remarkably inefficient enzyme, fixing only 2-10 CO2 molecules per second. Efforts to increase crop yields by bioengineering Rubisco remain unsuccessful, owing in part to the complex cellular machinery required for Rubisco biogenesis and metabolic maintenance. The large subunit of Rubisco requires the chaperonin system for folding, and recent studies have shown that assembly of hexadecameric Rubisco is mediated by specific assembly chaperones. Moreover, Rubisco function can be inhibited by a range of sugar-phosphate ligands, including RuBP. Metabolic repair depends on remodeling of Rubisco by the ATP-dependent Rubisco activase and hydrolysis of inhibitory sugar phosphates by specific phosphatases. Here, we review our present understanding of the structure and function of these auxiliary factors and their utilization in efforts to engineer more catalytically efficient Rubisco enzymes.
Collapse
Affiliation(s)
- Andreas Bracher
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ; , ,
| | - Spencer M Whitney
- Research School of Biology, Australian National University, Acton, Australian Capital Territory 2601, Australia;
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ; , ,
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ; , ,
| |
Collapse
|
14
|
Bhat JY, Thieulin-Pardo G, Hartl FU, Hayer-Hartl M. Rubisco Activases: AAA+ Chaperones Adapted to Enzyme Repair. Front Mol Biosci 2017; 4:20. [PMID: 28443288 PMCID: PMC5385338 DOI: 10.3389/fmolb.2017.00020] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/23/2017] [Indexed: 01/01/2023] Open
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the key enzyme of the Calvin-Benson-Bassham cycle of photosynthesis, requires conformational repair by Rubisco activase for efficient function. Rubisco mediates the fixation of atmospheric CO2 by catalyzing the carboxylation of the five-carbon sugar ribulose-1,5-bisphosphate (RuBP). It is a remarkably inefficient enzyme, and efforts to increase crop yields by bioengineering Rubisco remain unsuccessful. This is due in part to the complex cellular machinery required for Rubisco biogenesis and metabolic maintenance. To function, Rubisco must undergo an activation process that involves carboxylation of an active site lysine by a non-substrate CO2 molecule and binding of a Mg2+ ion. Premature binding of the substrate RuBP results in an inactive enzyme. Moreover, Rubisco can also be inhibited by a range of sugar phosphates, some of which are “misfire” products of its multistep catalytic reaction. The release of the inhibitory sugar molecule is mediated by the AAA+ protein Rubisco activase (Rca), which couples hydrolysis of ATP to the structural remodeling of Rubisco. Rca enzymes are found in the vast majority of photosynthetic organisms, from bacteria to higher plants. They share a canonical AAA+ domain architecture and form six-membered ring complexes but are diverse in sequence and mechanism, suggesting their convergent evolution. In this review, we discuss recent advances in understanding the structure and function of this important group of client-specific AAA+ proteins.
Collapse
Affiliation(s)
- Javaid Y Bhat
- Department of Cellular Biochemistry, Max-Planck-Institute of BiochemistryMartinsried, Germany
| | - Gabriel Thieulin-Pardo
- Department of Cellular Biochemistry, Max-Planck-Institute of BiochemistryMartinsried, Germany
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max-Planck-Institute of BiochemistryMartinsried, Germany
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max-Planck-Institute of BiochemistryMartinsried, Germany
| |
Collapse
|
15
|
Feller U. Drought stress and carbon assimilation in a warming climate: Reversible and irreversible impacts. JOURNAL OF PLANT PHYSIOLOGY 2016; 203:84-94. [PMID: 27083537 DOI: 10.1016/j.jplph.2016.04.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 04/01/2016] [Accepted: 04/04/2016] [Indexed: 06/05/2023]
Abstract
Global change is characterized by increased CO2 concentration in the atmosphere, increasing average temperature and more frequent extreme events including drought periods, heat waves and flooding. Especially the impacts of drought and of elevated temperature on carbon assimilation are considered in this review. Effects of extreme events on the subcellular level as well as on the whole plant level may be reversible, partially reversible or irreversible. The photosynthetically active biomass depends on the number and the size of mature leaves and the photosynthetic activity in this biomass during stress and subsequent recovery phases. The total area of active leaves is determined by leaf expansion and senescence, while net photosynthesis per leaf area is primarily influenced by stomatal opening (stomatal conductance), mesophyll conductance, activity of the photosynthetic apparatus (light absorption and electron transport, activity of the Calvin cycle) and CO2 release by decarboxylation reactions (photorespiration, dark respiration). Water status, stomatal opening and leaf temperature represent a "magic triangle" of three strongly interacting parameters. The response of stomata to altered environmental conditions is important for stomatal limitations. Rubisco protein is quite thermotolerant, but the enzyme becomes at elevated temperature more rapidly inactivated (decarbamylation, reversible effect) and must be reactivated by Rubisco activase (carbamylation of a lysine residue). Rubisco activase is present under two forms (encoded by separate genes or products of alternative splicing of the pre-mRNA from one gene) and is very thermosensitive. Rubisco activase was identified as a key protein for photosynthesis at elevated temperature (non-stomatal limitation). During a moderate heat stress Rubisco activase is reversibly inactivated, but during a more severe stress (higher temperature and/or longer exposure) the protein is irreversibly inactivated, insolubilized and finally degraded. On the level of the leaf, this loss of photosynthetic activity may still be reversible when new Rubisco activase is produced by protein synthesis. Rubisco activase as well as enzymes involved in the detoxification of reactive oxygen species or in osmoregulation are considered as important targets for breeding crop plants which are still productive under drought and/or at elevated leaf temperature in a changing climate.
Collapse
Affiliation(s)
- Urs Feller
- Institute of Plant Sciences and Oeschger Centre for Climate Change Research (OCCR), University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland.
| |
Collapse
|
16
|
Scafaro AP, Gallé A, Van Rie J, Carmo-Silva E, Salvucci ME, Atwell BJ. Heat tolerance in a wild Oryza species is attributed to maintenance of Rubisco activation by a thermally stable Rubisco activase ortholog. THE NEW PHYTOLOGIST 2016; 211:899-911. [PMID: 27145723 DOI: 10.1111/nph.13963] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 03/03/2016] [Indexed: 05/10/2023]
Abstract
The mechanistic basis of tolerance to heat stress was investigated in Oryza sativa and two wild rice species, Oryza meridionalis and Oryza australiensis. The wild relatives are endemic to the hot, arid Australian savannah. Leaf elongation rates and gas exchange were measured during short periods of supra-optimal heat, revealing species differences. The Rubisco activase (RCA) gene from each species was sequenced. Using expressed recombinant RCA and leaf-extracted RCA, the kinetic properties of the two isoforms were studied under high temperatures. Leaf elongation was undiminished at 45°C in O. australiensis. The net photosynthetic rate was almost 50% slower in O. sativa at 45°C than at 28°C, while in O. australiensis it was unaffected. Oryza meridionalis exhibited intermediate heat tolerance. Based on previous reports that RCA is heat-labile, the Rubisco activation state was measured. It correlated positively with leaf elongation rates across all three species and four periods of exposure to 45°C. Sequence analysis revealed numerous polymorphisms in the RCA amino acid sequence from O. australiensis. The O. australiensis RCA enzyme was thermally stable up to 42°C, contrasting with RCA from O. sativa, which was inhibited at 36°C. We attribute heat tolerance in the wild species to thermal stability of RCA, enabling Rubisco to remain active.
Collapse
Affiliation(s)
- Andrew P Scafaro
- Department of Biological Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, 2109, Australia
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Alexander Gallé
- Bayer CropScience NV, Innovation Center - Trait Research, Technologiepark 38, Zwijnaarde (Gent), 9052, Belgium
| | - Jeroen Van Rie
- Bayer CropScience NV, Innovation Center - Trait Research, Technologiepark 38, Zwijnaarde (Gent), 9052, Belgium
| | | | - Michael E Salvucci
- US Department of Agriculture, Agricultural Research Service, Arid-Land Agricultural Research Center, Maricopa, AZ, 85138, USA
| | - Brian J Atwell
- Department of Biological Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, 2109, Australia
| |
Collapse
|
17
|
Hazra S, Henderson JN, Liles K, Hilton MT, Wachter RM. Regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activase: product inhibition, cooperativity, and magnesium activation. J Biol Chem 2015; 290:24222-36. [PMID: 26283786 PMCID: PMC4591810 DOI: 10.1074/jbc.m115.651745] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 08/04/2015] [Indexed: 12/24/2022] Open
Abstract
In many photosynthetic organisms, tight-binding Rubisco inhibitors are released by the motor protein Rubisco activase (Rca). In higher plants, Rca plays a pivotal role in regulating CO2 fixation. Here, the ATPase activity of 0.005 mm tobacco Rca was monitored under steady-state conditions, and global curve fitting was utilized to extract kinetic constants. The kcat was best fit by 22.3 ± 4.9 min(-1), the Km for ATP by 0.104 ± 0.024 mm, and the Ki for ADP by 0.037 ± 0.007 mm. Without ADP, the Hill coefficient for ATP hydrolysis was extracted to be 1.0 ± 0.1, indicating noncooperative behavior of homo-oligomeric Rca assemblies. However, the addition of ADP was shown to introduce positive cooperativity between two or more subunits (Hill coefficient 1.9 ± 0.2), allowing for regulation via the prevailing ATP/ADP ratio. ADP-mediated activation was not observed, although larger amounts led to competitive product inhibition of hydrolytic activity. The catalytic efficiency increased 8.4-fold upon cooperative binding of a second magnesium ion (Hill coefficient 2.5 ± 0.5), suggesting at least three conformational states (ATP-bound, ADP-bound, and empty) within assemblies containing an average of about six subunits. The addition of excess Rubisco (24:1, L8S8/Rca6) and crowding agents did not modify catalytic rates. However, high magnesium provided for thermal Rca stabilization. We propose that magnesium mediates the formation of closed hexameric toroids capable of high turnover rates and amenable to allosteric regulation. We suggest that in vivo, the Rca hydrolytic activity is tuned by fluctuating [Mg(2+)] in response to changes in available light.
Collapse
Affiliation(s)
- Suratna Hazra
- From the Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287
| | - J Nathan Henderson
- From the Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287
| | - Kevin Liles
- From the Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287
| | - Matthew T Hilton
- From the Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287
| | - Rebekka M Wachter
- From the Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287
| |
Collapse
|
18
|
Carmo-Silva E, Scales JC, Madgwick PJ, Parry MAJ. Optimizing Rubisco and its regulation for greater resource use efficiency. PLANT, CELL & ENVIRONMENT 2015; 38:1817-32. [PMID: 25123951 DOI: 10.1111/pce.12425] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 08/01/2014] [Accepted: 08/03/2014] [Indexed: 05/19/2023]
Abstract
Rubisco catalyses the carboxylation of ribulose-1,5-bisphosphate (RuBP), enabling net CO2 assimilation in photosynthesis. The properties and regulation of Rubisco are not optimal for biomass production in current and projected future environments. Rubisco is relatively inefficient, and large amounts of the enzyme are needed to support photosynthesis, requiring large investments in nitrogen. The competing oxygenation of RuBP by Rubisco decreases photosynthetic efficiency. Additionally, Rubisco is inhibited by some sugar phosphates and depends upon interaction with Rubisco activase (Rca) to be reactivated. Rca activity is modulated by the chloroplast redox status and ADP/ATP ratios, thereby mediating Rubisco activation and photosynthetic induction in response to irradiance. The extreme thermal sensitivity of Rca compromises net CO2 assimilation at moderately high temperatures. Given its central role in carbon assimilation, the improvement of Rubisco function and regulation is tightly linked with irradiance, nitrogen and water use efficiencies. Although past attempts have had limited success, novel technologies and an expanding knowledge base make the challenge of improving Rubisco activity in crops an achievable goal. Strategies to optimize Rubisco and its regulation are addressed in relation to their potential to improve crop resource use efficiency and climate resilience of photosynthesis.
Collapse
Affiliation(s)
| | - Joanna C Scales
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
| | - Pippa J Madgwick
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
| | - Martin A J Parry
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
| |
Collapse
|
19
|
Hauser T, Popilka L, Hartl FU, Hayer-Hartl M. Role of auxiliary proteins in Rubisco biogenesis and function. NATURE PLANTS 2015; 1:15065. [PMID: 27250005 DOI: 10.1038/nplants.2015.65] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 04/20/2015] [Indexed: 05/05/2023]
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyses the conversion of atmospheric CO2 into organic compounds during photosynthesis. Despite its pivotal role in plant metabolism, Rubisco is an inefficient enzyme and has therefore been a key target in bioengineering efforts to improve crop yields. Much has been learnt about the complex cellular machinery involved in Rubisco assembly and metabolic repair over recent years. The simple form of Rubisco found in certain bacteria and dinoflagellates comprises two large subunits, and generally requires the chaperonin system for folding. However, the evolution of hexadecameric Rubisco, which comprises eight large and eight small subunits, from its dimeric precursor has rendered Rubisco in most plants, algae, cyanobacteria and proteobacteria dependent on an array of additional factors. These auxiliary factors include several chaperones for assembly as well as ATPases of the AAA+ family for functional maintenance. An integrated view of the pathways underlying Rubisco biogenesis and repair will pave the way for efforts to improve the enzyme with the goal of increasing crop yields.
Collapse
Affiliation(s)
- Thomas Hauser
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Leonhard Popilka
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| |
Collapse
|
20
|
Singh J, Pandey P, James D, Chandrasekhar K, Achary VMM, Kaul T, Tripathy BC, Reddy MK. Enhancing C3 photosynthesis: an outlook on feasible interventions for crop improvement. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:1217-30. [PMID: 25196090 DOI: 10.1111/pbi.12246] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 07/14/2014] [Accepted: 07/20/2014] [Indexed: 05/05/2023]
Abstract
Despite the declarations and collective measures taken to eradicate hunger at World Food Summits, food security remains one of the biggest issues that we are faced with. The current scenario could worsen due to the alarming increase in world population, further compounded by adverse climatic conditions, such as increase in atmospheric temperature, unforeseen droughts and decreasing soil moisture, which will decrease crop yield even further. Furthermore, the projected increase in yields of C3 crops as a result of increasing atmospheric CO2 concentrations is much less than anticipated. Thus, there is an urgent need to increase crop productivity beyond existing yield potentials to address the challenge of food security. One of the domains of plant biology that promises hope in overcoming this problem is study of C3 photosynthesis. In this review, we have examined the potential bottlenecks of C3 photosynthesis and the strategies undertaken to overcome them. The targets considered for possible intervention include RuBisCO, RuBisCO activase, Calvin-Benson-Bassham cycle enzymes, CO2 and carbohydrate transport, and light reactions among many others. In addition, other areas which promise scope for improvement of C3 photosynthesis, such as mining natural genetic variations, mathematical modelling for identifying new targets, installing efficient carbon fixation and carbon concentrating mechanisms have been touched upon. Briefly, this review intends to shed light on the recent advances in enhancing C3 photosynthesis for crop improvement.
Collapse
Affiliation(s)
- Jitender Singh
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India; School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Kuriata AM, Chakraborty M, Henderson JN, Hazra S, Serban AJ, Pham TVT, Levitus M, Wachter RM. ATP and magnesium promote cotton short-form ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase hexamer formation at low micromolar concentrations. Biochemistry 2014; 53:7232-46. [PMID: 25357088 DOI: 10.1021/bi500968h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We report a fluorescence correlation spectroscopy (FCS) study of the assembly pathway of the AAA+ protein ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase (Rca), a ring-forming ATPase responsible for activation of inhibited Rubisco complexes for biological carbon fixation. A thermodynamic characterization of simultaneously populated oligomeric states appears critical in understanding Rca structure and function. Using cotton β-Rca, we demonstrate that apparent diffusion coefficients vary as a function of concentration, nucleotide, and cation. Using manual fitting procedures, we provide estimates for the equilibrium constants for the stepwise assembly and find that in the presence of ATPγS, the Kd for hexamerization is 10-fold lower than with ADP (∼0.1 vs ∼1 μM). Hexamer fractions peak at 30 μM and dominate at 8-70 μM Rca, where they comprise 60-80% of subunits with ATPγS, compared with just 30-40% with ADP. Dimer fractions peak at 1-4 μM Rca, where they comprise 15-18% with ATPγS and 26-28% with ADP. At 30 μM Rca, large aggregates begin to form that comprise ∼10% of total protein with ATPγS and ∼25% with ADP. FCS data collected on the catalytically impaired WalkerB-D173N variant in the presence of ATP provided strong support for these results. Titration with free magnesium ions lead to the disaggregation of larger complexes in favor of hexameric forms, suggesting that a second magnesium binding site with a Kd value of 1-3 mM mediates critical subunit contacts. We propose that closed-ring toroidal hexameric forms are stabilized by binding of Mg·ATP plus Mg2+, whereas Mg·ADP promotes continuous assembly to supramolecular aggregates such as spirals.
Collapse
Affiliation(s)
- Agnieszka M Kuriata
- Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University , Tempe, Arizona 85287, United States
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Scales JC, Parry MAJ, Salvucci ME. A non-radioactive method for measuring Rubisco activase activity in the presence of variable ATP: ADP ratios, including modifications for measuring the activity and activation state of Rubisco. PHOTOSYNTHESIS RESEARCH 2014; 119:355-65. [PMID: 24390640 PMCID: PMC3923112 DOI: 10.1007/s11120-013-9964-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/19/2013] [Indexed: 05/19/2023]
Abstract
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes carboxylation of ribulose-1,5-bisphosphate, the first in a series of reactions leading to the incorporation of atmospheric CO₂ into biomass. Rubisco requires Rubisco activase (RCA), an AAA+ ATPase that reactivates Rubisco by remodelling the conformation of inhibitor-bound sites. RCA is regulated by the ratio of ADP:ATP, with the precise response potentiated by redox regulation of the alpha-isoform. Measuring the effects of ADP on the activation of Rubisco by RCA using the well-established photometric assay is problematic because of the adenine nucleotide requirement of 3-phosphoglycerate (3-PGA) kinase. Described here is a novel assay for measuring RCA activity in the presence of variable ratios of ADP:ATP. The assay couples the formation of 3-PGA from ribulose 1,5-bisphosphate and CO₂ to NADH oxidation through cofactor-dependent phosphoglycerate mutase, enolase, PEP carboxylase and malate dehydrogenase. The assay was used to determine the effects of Rubisco and RCA concentration and ADP:ATP ratio on RCA activity, and to measure the activation of a modified Rubisco by RCA. Variations of the basic assay were used to measure the activation state of Rubisco in leaf extracts and the activity of purified Rubisco. The assay can be automated for high-throughput processing by conducting the reactions in two stages.
Collapse
Affiliation(s)
- Joanna C. Scales
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ UK
| | - Martin A. J. Parry
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ UK
| | - Michael E. Salvucci
- Arid-Land Agricultural Research Center, U.S. Department of Agriculture-Agricultural Research Service, 21881 N. Cardon Lane, Maricopa, AZ 85138 USA
| |
Collapse
|