1
|
Wang W, Xu L, Jiang G, Li Z, Bi YH, Zhou ZG. Characterization of a novel γ-type carbonic anhydrase, Sjγ-CA2, in Saccharina japonica: Insights into carbon concentration mechanism in macroalgae. Int J Biol Macromol 2024; 263:130506. [PMID: 38423426 DOI: 10.1016/j.ijbiomac.2024.130506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 02/23/2024] [Accepted: 02/26/2024] [Indexed: 03/02/2024]
Abstract
Carbonic anhydrase (CA) is a crucial component of CO2-concentrating mechanism (CCM) in macroalgae. In Saccharina japonica, an important brown seaweed, 11 CAs, including 5 α-, 3 β-, and 3 γ-CAs, have been documented. Among them, one α-CA and one β-CA were localized in the periplasmic space, one α-CA was found in the chloroplast, and one γ-CA was situated in mitochondria. Notably, the known γ-CAs have predominantly been identified in mitochondria. In this study, we identified a chloroplastic γ-type CA, Sjγ-CA2, in S. japonica. Based on the reported amino acid sequence of Sjγ-CA2, the epitope peptide for monoclonal antibody production was selected as 165 Pro-305. After purification and specificity identification, anti-SjγCA2 monoclonal antibody was employed in immunogold electron microscopy. The results illustrated that Sjγ-CA2 was localized in the chloroplasts of both gametophytes and sporophytes of S. japonica. Subsequently, immunoprecipitation coupled with LC-MS/MS analysis revealed that Sjγ-CA2 mainly interacted with photosynthesis-related proteins. Moreover, the first 65 amino acids at N-terminal of Sjγ-CA2 was identified as the chloroplast transit peptide by the transient expression of GFP-SjγCA2 fused protein in tabacco. Real-time PCR results demonstrated an up-regulation of the transcription of Sjγ-CA2 gene in response to high CO2 concentration. These findings implied that Sjγ-CA2 might contribute to minimizing the leakage of CO2 from chloroplasts and help maintaining a high concentration of CO2 around Rubisco.
Collapse
Affiliation(s)
- Wen Wang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred By Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Ling Xu
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred By Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Gang Jiang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred By Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Zhi Li
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred By Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Yan-Hui Bi
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred By Ministry of Education, Shanghai Ocean University, Shanghai 201306, China.
| | - Zhi-Gang Zhou
- International Research Center for Marine Biosciences Conferred By Ministry of Science and Technology, Shanghai Ocean University, Shanghai 201306, China.
| |
Collapse
|
2
|
Saw WG, Le KCM, Shin J, Kwek JHM, Wong CF, Ragunathan P, Fong TC, Müller V, Grüber G. Atomic insights of an up and down conformation of the Acinetobacter baumannii F 1 -ATPase subunit ε and deciphering the residues critical for ATP hydrolysis inhibition and ATP synthesis. FASEB J 2023; 37:e23040. [PMID: 37318822 DOI: 10.1096/fj.202300175rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/23/2023] [Accepted: 06/05/2023] [Indexed: 06/16/2023]
Abstract
The Acinetobacter baumannii F1 FO -ATP synthase (α3 :β3 :γ:δ:ε:a:b2 :c10 ), which is essential for this strictly respiratory opportunistic human pathogen, is incapable of ATP-driven proton translocation due to its latent ATPase activity. Here, we generated and purified the first recombinant A. baumannii F1 -ATPase (AbF1 -ATPase) composed of subunits α3 :β3 :γ:ε, showing latent ATP hydrolysis. A 3.0 Å cryo-electron microscopy structure visualizes the architecture and regulatory element of this enzyme, in which the C-terminal domain of subunit ε (Abε) is present in an extended position. An ε-free AbF1 -ɑβγ complex generated showed a 21.5-fold ATP hydrolysis increase, demonstrating that Abε is the major regulator of AbF1 -ATPase's latent ATP hydrolysis. The recombinant system enabled mutational studies of single amino acid substitutions within Abε or its interacting subunits β and γ, respectively, as well as C-terminal truncated mutants of Abε, providing a detailed picture of Abε's main element for the self-inhibition mechanism of ATP hydrolysis. Using a heterologous expression system, the importance of Abε's C-terminus in ATP synthesis of inverted membrane vesicles, including AbF1 FO -ATP synthases, has been explored. In addition, we are presenting the first NMR solution structure of the compact form of Abε, revealing interaction of its N-terminal β-barrel and C-terminal ɑ-hairpin domain. A double mutant of Abε highlights critical residues for Abε's domain-domain formation which is important also for AbF1 -ATPase's stability. Abε does not bind MgATP, which is described to regulate the up and down movements in other bacterial counterparts. The data are compared to regulatory elements of F1 -ATPases in bacteria, chloroplasts, and mitochondria to prevent wasting of ATP.
Collapse
Affiliation(s)
- Wuan-Geok Saw
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
| | - Khoa Cong Minh Le
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Joon Shin
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jes Hui Min Kwek
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Chui Fann Wong
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Priya Ragunathan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Tuck Choy Fong
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Volker Müller
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt, Germany
| | - Gerhard Grüber
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| |
Collapse
|
3
|
Sekiguchi T, Yoshida K, Wakabayashi KI, Hisabori T. Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins. J Biol Chem 2022; 298:102541. [PMID: 36174673 PMCID: PMC9626944 DOI: 10.1016/j.jbc.2022.102541] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/15/2022] [Accepted: 09/21/2022] [Indexed: 12/05/2022] Open
Abstract
Chloroplast FoF1-ATP synthase (CFoCF1) uses an electrochemical gradient of protons across the thylakoid membrane (ΔμH+) as an energy source in the ATP synthesis reaction. CFoCF1 activity is regulated by the redox state of a Cys pair on its central axis, that is, the γ subunit (CF1-γ). When the ΔμH+ is formed by the photosynthetic electron transfer chain under light conditions, CF1-γ is reduced by thioredoxin (Trx), and the entire CFoCF1 enzyme is activated. The redox regulation of CFoCF1 is a key mechanism underlying the control of ATP synthesis under light conditions. In contrast, the oxidative deactivation process involving CFoCF1 has not been clarified. In the present study, we analyzed the oxidation of CF1-γ by two physiological oxidants in the chloroplast, namely the proteins Trx-like 2 and atypical Cys-His-rich Trx. Using the thylakoid membrane containing the reduced form of CFoCF1, we were able to assess the CF1-γ oxidation ability of these Trx-like proteins. Our kinetic analysis indicated that these proteins oxidized CF1-γ with a higher efficiency than that achieved by a chemical oxidant and typical chloroplast Trxs. Additionally, the CF1-γ oxidation rate due to Trx-like proteins and the affinity between them were changed markedly when ΔμH+ formation across the thylakoid membrane was manipulated artificially. Collectively, these results indicate that the formation status of the ΔμH+ controls the redox regulation of CFoCF1 to prevent energetic disadvantages in plants.
Collapse
Affiliation(s)
- Takatoshi Sekiguchi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Ken-Ichi Wakabayashi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan.
| |
Collapse
|
4
|
Buchert F, Bailleul B, Joliot P. Disentangling chloroplast ATP synthase regulation by proton motive force and thiol modulation in Arabidopsis leaves. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148434. [PMID: 33932368 DOI: 10.1016/j.bbabio.2021.148434] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 04/06/2021] [Accepted: 04/20/2021] [Indexed: 11/29/2022]
Abstract
The chloroplast ATP synthase (CF1Fo) contains a specific feature to the green lineage: a γ-subunit redox domain that contains a cysteine couple which interacts with the torque-transmitting βDELSEED-loop. This thiol modulation equips CF1Fo with an important environmental fine-tuning mechanism. In vitro, disulfide formation in the γ-redox domain slows down the activity of the CF1Fo at low transmembrane electrochemical proton gradient ( [Formula: see text] ), which agrees with its proposed role as chock based on recently solved structure. The γ-dithiol formation at the onset of light is crucial to maximize photosynthetic efficiency since it lowers the [Formula: see text] activation level for ATP synthesis in vitro. Here, we validate these findings in vivo by utilizing absorption spectroscopy in Arabidopsis thaliana. To do so, we monitored the [Formula: see text] present in darkness and identified its mitochondrial sources. By following the fate and components of light-induced extra [Formula: see text] , we estimated the ATP lifetime that lasted up to tens of minutes after long illuminations. Based on the relationship between [Formula: see text] and CF1Fo activity, we conclude that the dithiol configuration in vivo facilitates photosynthesis by driving the same ATP synthesis rate at a significative lower [Formula: see text] than in the γ-disulfide state. The presented in vivo findings are an additional proof of the importance of CF1Fo thiol modulation, reconciling biochemical in vitro studies and structural insights.
Collapse
Affiliation(s)
- Felix Buchert
- Laboratory of Chloroplast Biology and Light-Sensing in Microalgae - UMR7141, IBPC, CNRS-Sorbonne Université, Paris, France; Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, 48143 Münster, Germany.
| | - Benjamin Bailleul
- Laboratory of Chloroplast Biology and Light-Sensing in Microalgae - UMR7141, IBPC, CNRS-Sorbonne Université, Paris, France
| | - Pierre Joliot
- Laboratory of Chloroplast Biology and Light-Sensing in Microalgae - UMR7141, IBPC, CNRS-Sorbonne Université, Paris, France
| |
Collapse
|
5
|
Rotor subunits adaptations in ATP synthases from photosynthetic organisms. Biochem Soc Trans 2021; 49:541-550. [PMID: 33890627 PMCID: PMC8106487 DOI: 10.1042/bst20190936] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/17/2021] [Accepted: 03/22/2021] [Indexed: 11/17/2022]
Abstract
Driven by transmembrane electrochemical ion gradients, F-type ATP synthases are the primary source of the universal energy currency, adenosine triphosphate (ATP), throughout all domains of life. The ATP synthase found in the thylakoid membranes of photosynthetic organisms has some unique features not present in other bacterial or mitochondrial systems. Among these is a larger-than-average transmembrane rotor ring and a redox-regulated switch capable of inhibiting ATP hydrolysis activity in the dark by uniquely adapted rotor subunit modifications. Here, we review recent insights into the structure and mechanism of ATP synthases specifically involved in photosynthesis and explore the cellular physiological consequences of these adaptations at short and long time scales.
Collapse
|
6
|
Petri J, Nakatani Y, Montgomery MG, Ferguson SA, Aragão D, Leslie AGW, Heikal A, Walker JE, Cook GM. Structure of F 1-ATPase from the obligate anaerobe Fusobacterium nucleatum. Open Biol 2019; 9:190066. [PMID: 31238823 PMCID: PMC6597759 DOI: 10.1098/rsob.190066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The crystal structure of the F1-catalytic domain of the adenosine triphosphate (ATP) synthase has been determined from the pathogenic anaerobic bacterium Fusobacterium nucleatum. The enzyme can hydrolyse ATP but is partially inhibited. The structure is similar to those of the F1-ATPases from Caldalkalibacillus thermarum, which is more strongly inhibited in ATP hydrolysis, and in Mycobacterium smegmatis, which has a very low ATP hydrolytic activity. The βE-subunits in all three enzymes are in the conventional ‘open’ state, and in the case of C. thermarum and M. smegmatis, they are occupied by an ADP and phosphate (or sulfate), but in F. nucleatum, the occupancy by ADP appears to be partial. It is likely that the hydrolytic activity of the F. nucleatum enzyme is regulated by the concentration of ADP, as in mitochondria.
Collapse
Affiliation(s)
- Jessica Petri
- 1 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago , Dunedin 9054 , New Zealand
| | - Yoshio Nakatani
- 1 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago , Dunedin 9054 , New Zealand.,2 Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland , Private Bag 92019, Auckland 1042 , New Zealand
| | - Martin G Montgomery
- 3 Medical Research Council Mitochondrial Biology Unit , Cambridge Biomedical Campus, Cambridge CB2 0XY , UK
| | - Scott A Ferguson
- 1 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago , Dunedin 9054 , New Zealand
| | - David Aragão
- 4 Australian Synchrotron , 800 Blackburn Road, Clayton, Victoria 3168 , Australia
| | - Andrew G W Leslie
- 5 Medical Research Council Laboratory of Molecular Biology , Cambridge Biomedical Campus, Cambridge CB2 0QH , UK
| | - Adam Heikal
- 1 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago , Dunedin 9054 , New Zealand.,2 Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland , Private Bag 92019, Auckland 1042 , New Zealand
| | - John E Walker
- 3 Medical Research Council Mitochondrial Biology Unit , Cambridge Biomedical Campus, Cambridge CB2 0XY , UK
| | - Gregory M Cook
- 1 Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago , Dunedin 9054 , New Zealand.,2 Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland , Private Bag 92019, Auckland 1042 , New Zealand
| |
Collapse
|
7
|
The structure of the catalytic domain of the ATP synthase from Mycobacterium smegmatis is a target for developing antitubercular drugs. Proc Natl Acad Sci U S A 2019; 116:4206-4211. [PMID: 30683723 DOI: 10.1073/pnas.1817615116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The crystal structure of the F1-catalytic domain of the adenosine triphosphate (ATP) synthase has been determined from Mycobacterium smegmatis which hydrolyzes ATP very poorly. The structure of the α3β3-component of the catalytic domain is similar to those in active F1-ATPases in Escherichia coli and Geobacillus stearothermophilus However, its ε-subunit differs from those in these two active bacterial F1-ATPases as an ATP molecule is not bound to the two α-helices forming its C-terminal domain, probably because they are shorter than those in active enzymes and they lack an amino acid that contributes to the ATP binding site in active enzymes. In E. coli and G. stearothermophilus, the α-helices adopt an "up" state where the α-helices enter the α3β3-domain and prevent the rotor from turning. The mycobacterial F1-ATPase is most similar to the F1-ATPase from Caldalkalibacillus thermarum, which also hydrolyzes ATP poorly. The βE-subunits in both enzymes are in the usual "open" conformation but appear to be occupied uniquely by the combination of an adenosine 5'-diphosphate molecule with no magnesium ion plus phosphate. This occupation is consistent with the finding that their rotors have been arrested at the same point in their rotary catalytic cycles. These bound hydrolytic products are probably the basis of the inhibition of ATP hydrolysis. It can be envisaged that specific as yet unidentified small molecules might bind to the F1 domain in Mycobacterium tuberculosis, prevent ATP synthesis, and inhibit the growth of the pathogen.
Collapse
|
8
|
Hahn A, Vonck J, Mills DJ, Meier T, Kühlbrandt W. Structure, mechanism, and regulation of the chloroplast ATP synthase. Science 2018; 360:eaat4318. [PMID: 29748256 PMCID: PMC7116070 DOI: 10.1126/science.aat4318] [Citation(s) in RCA: 229] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/09/2018] [Indexed: 12/13/2022]
Abstract
The chloroplast adenosine triphosphate (ATP) synthase uses the electrochemical proton gradient generated by photosynthesis to produce ATP, the energy currency of all cells. Protons conducted through the membrane-embedded Fo motor drive ATP synthesis in the F1 head by rotary catalysis. We determined the high-resolution structure of the complete cF1Fo complex by cryo-electron microscopy, resolving side chains of all 26 protein subunits, the five nucleotides in the F1 head, and the proton pathway to and from the rotor ring. The flexible peripheral stalk redistributes differences in torsional energy across three unequal steps in the rotation cycle. Plant ATP synthase is autoinhibited by a β-hairpin redox switch in subunit γ that blocks rotation in the dark.
Collapse
Affiliation(s)
- Alexander Hahn
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Deryck J Mills
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Thomas Meier
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
| | - Werner Kühlbrandt
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
| |
Collapse
|
9
|
Ma F, Hu Y, Ju Y, Jiang Q, Cheng Z, Zhang Q. A novel tetratricopeptide repeat protein, WHITE TO GREEN1, is required for early chloroplast development and affects RNA editing in chloroplasts. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:5829-5843. [PMID: 29140512 PMCID: PMC5854136 DOI: 10.1093/jxb/erx383] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Accepted: 10/05/2017] [Indexed: 05/24/2023]
Abstract
The chloroplast is essential for plant photosynthesis and production, but the regulatory mechanism of chloroplast development is still elusive. Here, a novel gene, WHITE TO GREEN1 (WTG1), was identified to have a function in chloroplast development and plastid gene expression by screening Arabidopsis leaf coloration mutants. WTG1 encodes a chloroplast-localized tetratricopeptide repeat protein that is expressed widely in Arabidopsis cells. Disruption of WTG1 suppresses plant growth, retards leaf greening and chloroplast development, and represses photosynthetic gene expression, but complemented expression of WTG1 restored a normal phenotype. Moreover, WTG1 protein is associated with the organelle RNA editing factors MORF8 and MORF9, and RNA editing of the plastid petL-5 and ndhG-50 transcripts was affected in wtg1 mutants. These results indicate that WTG1 affects both transcriptional and posttranscriptional regulation of plastid gene expression, and provide evidence for the involvement of a tetratricopeptide repeat protein in chloroplast RNA editing in Arabidopsis.
Collapse
Affiliation(s)
- Fei Ma
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, China
| | - Yingchun Hu
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, China
| | - Yan Ju
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, China
| | - Qianru Jiang
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, China
| | - Zhijun Cheng
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, China
| | - Quan Zhang
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, China
| |
Collapse
|
10
|
Trypanosoma brucei TbIF1 inhibits the essential F1-ATPase in the infectious form of the parasite. PLoS Negl Trop Dis 2017; 11:e0005552. [PMID: 28414727 PMCID: PMC5407850 DOI: 10.1371/journal.pntd.0005552] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 04/27/2017] [Accepted: 04/04/2017] [Indexed: 12/01/2022] Open
Abstract
The mitochondrial (mt) FoF1-ATP synthase of the digenetic parasite, Trypanosoma brucei, generates ATP during the insect procyclic form (PF), but becomes a perpetual consumer of ATP in the mammalian bloodstream form (BF), which lacks a canonical respiratory chain. This unconventional dependence on FoF1-ATPase is required to maintain the essential mt membrane potential (Δψm). Normally, ATP hydrolysis by this rotary molecular motor is restricted to when eukaryotic cells experience sporadic hypoxic conditions, during which this compulsory function quickly depletes the cellular ATP pool. To protect against this cellular treason, the highly conserved inhibitory factor 1 (IF1) binds the enzyme in a manner that solely inhibits the hydrolytic activity. Intriguingly, we were able to identify the IF1 homolog in T. brucei (TbIF1), but determined that its expression in the mitochondrion is tightly regulated throughout the life cycle as it is only detected in PF cells. TbIF1 appears to primarily function as an emergency brake in PF cells, where it prevented the restoration of the Δψm by FoF1-ATPase when respiration was chemically inhibited. In vitro, TbIF1 overexpression specifically inhibits the hydrolytic activity but not the synthetic capability of the FoF1-ATP synthase in PF mitochondria. Furthermore, low μM amounts of recombinant TbIF1 achieve the same inhibition of total mt ATPase activity as the FoF1-ATPase specific inhibitors, azide and oligomycin. Therefore, even minimal ectopic expression of TbIF1 in BF cells proved lethal as the indispensable Δψm collapsed due to inhibited FoF1-ATPase. In summary, we provide evidence that T. brucei harbors a natural and potent unidirectional inhibitor of the vital FoF1-ATPase activity that can be exploited for future structure-based drug design. Enzymes are catalysts that drive both a forward and reverse chemical reaction depending on the thermodynamic properties. FoF1-ATP synthase is a multiprotein enzyme that under normal physiological conditions generates ATP. However, when respiration is impeded, this rotary molecular machine reverses and hydrolyzes ATP to pump protons and maintain the essential mitochondrial membrane potential. While this activity is exceptional in most eukaryotic cells, the unique composition of the Trypanosoma brucei mitochondrion dictates that the infectious stage of this human parasite is utterly dependent on the hydrolytic activity of FoF1-ATPase. While searching for better chemotherapeutics against Human African Trypanosomiasis, several trypanocidal compounds were determined to interact with this enzyme, but they indiscriminately inhibit both the ATP hydrolytic and synthetic activities. A more promising approach involves the conserved eukaryotic protein IF1, a unidirectional inhibitor that prevents just ATP hydrolysis. Auspiciously, we identified this protein homolog in T. brucei (TbIF1) and its expression is tightly regulated between life stages of the parasite. Importantly, the introduction of exogenous TbIF1 protein specifically inhibits FoF1-ATPase and is lethal for the infectious stage of T. brucei. Therefore, we have identified a natural inhibitor of an essential and druggable enzyme that can be exploited for future structure-based drug design.
Collapse
|
11
|
Shen W, Ye L, Ma J, Yuan Z, Zheng B, Lv C, Zhu Z, Chen X, Gao Z, Chen G. The existence of C4-bundle-sheath-like photosynthesis in the mid-vein of C3 rice. RICE (NEW YORK, N.Y.) 2016; 9:20. [PMID: 27164981 PMCID: PMC4864733 DOI: 10.1186/s12284-016-0094-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 04/30/2016] [Indexed: 05/12/2023]
Abstract
BACKGROUND Recent studies have shown that C4-like photosynthetic pathways partly reside in photosynthetic cells surrounding the vascular system of C3 dicots. However, it is still unclear whether this is the case in C3 monocots, especially at the molecular level. RESULTS In order to fill this gap, we investigated several characteristics required for C4 photosynthesis, including C4 pathway enzymes, cyclic/non-cyclic photophosphorylation rates, the levels and assembly state of photosynthetic machineries, in the mid-veins of C3 monocots rice with leaf laminae used as controls. The signature of photosystem photochemistry was also recorded via non-invasive chlorophyll a fluorescence and reflectance changes at 820 nm in vivo. Our results showed that rice mid-veins were photosynthetically active with higher levels of three C4 decarboxylases. Meanwhile, the linear electron transport chain was blocked in mid-veins due to the selective loss of dysfunctional photosystem II subunits. However, photosystem I was sufficient to support cyclic electron flow in mid-veins, reminiscent of the bundle sheath in C4 plants. CONCLUSIONS The photosynthetic attributes required for C4 photosynthesis were identified for the first time in the monocotyledon model crop rice, suggesting that this is likely a general innate characteristic of C3 plants which might be preconditioned for the C4 pathway evolution. Understanding these attributes would provide a base for improved strategies for engineering C4 photosynthetic pathways into rice.
Collapse
Affiliation(s)
- Weijun Shen
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Luhuan Ye
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Jing Ma
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Zhongyuan Yuan
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Baogang Zheng
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Chuangen Lv
- Institute of Food and Crops, Jiangsu Academy of Agricultural Sciences, 50 Zhongling Street, Nanjing, 210014, China
| | - Ziqiang Zhu
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Xiang Chen
- University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Zhiping Gao
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
| | - Guoxiang Chen
- College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
| |
Collapse
|
12
|
Carrillo LR, Froehlich JE, Cruz JA, Savage LJ, Kramer DM. Multi-level regulation of the chloroplast ATP synthase: the chloroplast NADPH thioredoxin reductase C (NTRC) is required for redox modulation specifically under low irradiance. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 87:654-63. [PMID: 27233821 DOI: 10.1111/tpj.13226] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/17/2016] [Accepted: 05/23/2016] [Indexed: 05/26/2023]
Abstract
The chloroplast ATP synthase is known to be regulated by redox modulation of a disulfide bridge on the γ-subunit through the ferredoxin-thioredoxin regulatory system. We show that a second enzyme, the recently identified chloroplast NADPH thioredoxin reductase C (NTRC), plays a role specifically at low irradiance. Arabidopsis mutants lacking NTRC (ntrc) displayed a striking photosynthetic phenotype in which feedback regulation of the light reactions was strongly activated at low light, but returned to wild-type levels as irradiance was increased. This effect was caused by an altered redox state of the γ-subunit under low, but not high, light. The low light-specific decrease in ATP synthase activity in ntrc resulted in a buildup of the thylakoid proton motive force with subsequent activation of non-photochemical quenching and downregulation of linear electron flow. We conclude that NTRC provides redox modulation at low light using the relatively oxidizing substrate NADPH, whereas the canonical ferredoxin-thioredoxin system can take over at higher light, when reduced ferredoxin can accumulate. Based on these results, we reassess previous models for ATP synthase regulation and propose that NTRC is most likely regulated by light. We also find that ntrc is highly sensitive to rapidly changing light intensities that probably do not involve the chloroplast ATP synthase, implicating this system in multiple photosynthetic processes, particularly under fluctuating environmental conditions.
Collapse
Affiliation(s)
- L Ruby Carrillo
- Biochemistry & Molecular Biology, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
| | - John E Froehlich
- Biochemistry & Molecular Biology, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
| | - Jeffrey A Cruz
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
| | - Linda J Savage
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA
| | - David M Kramer
- Biochemistry & Molecular Biology, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA.
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, Rm 106, East Lansing, MI, 48824, USA.
| |
Collapse
|
13
|
Turina P, Petersen J, Gräber P. Thermodynamics of proton transport coupled ATP synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:653-64. [PMID: 26940516 DOI: 10.1016/j.bbabio.2016.02.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 01/16/2016] [Accepted: 02/28/2016] [Indexed: 10/22/2022]
Abstract
The thermodynamic H(+)/ATP ratio of the H(+)-ATP synthase from chloroplasts was measured in proteoliposomes after energization of the membrane by an acid base transition (Turina et al. 2003 [13], 418-422). The method is discussed, and all published data obtained with this system are combined and analyzed as a single dataset. This meta-analysis led to the following results. 1) At equilibrium, the transmembrane ΔpH is energetically equivalent to the transmembrane electric potential difference. 2) The standard free energy for ATP synthesis (reference reaction) is ΔG°(ref)=33.8±1.3kJ/mol. 3) The thermodynamic H(+)/ATP ratio, as obtained from the shift of the ATP synthesis equilibrium induced by changing the transmembrane ΔpH (varying either pH(in) or pH(out)) is 4.0±0.1. The structural H(+)/ATP ratio, calculated from the ratio of proton binding sites on the c-subunit-ring in F(0) to the catalytic nucleotide binding sites on the β-subunits in F(1), is c/β=14/3=4.7. We infer that the energy of 0.7 protons per ATP that flow through the enzyme, but do not contribute to shifting the ATP/(ADP·Pi) ratio, is used for additional processes within the enzyme, such as activation, and/or energy dissipation, due e.g. to internal uncoupling. The ratio between the thermodynamic and the structural H(+)/ATP values is 0.85, and we conclude that this value represents the efficiency of the chemiosmotic energy conversion within the chloroplast H(+)-ATP synthase.
Collapse
Affiliation(s)
- Paola Turina
- Department of Biology, BiGeA, University of Bologna, Via Irnerio 42, I-40126 Bologna, Italy
| | - Jan Petersen
- Biomedicine Discovery Institute, Monash University, 1 Wellington Rd., Clayton, Vic 3800, Australia
| | - Peter Gräber
- Institut für Physikalische Chemie, University of Freiburg, Albertstr, 23a, D-79104 Freiburg, Germany.
| |
Collapse
|
14
|
Ma J, Lv C, Xu M, Chen G, Lv C, Gao Z. Photosynthesis performance, antioxidant enzymes, and ultrastructural analyses of rice seedlings under chromium stress. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:1768-78. [PMID: 26396015 DOI: 10.1007/s11356-015-5439-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 09/15/2015] [Indexed: 05/03/2023]
Abstract
The present study was conducted to examine the effects of increasing concentrations of chromium (Cr(6+)) (0, 25, 50, 100, and 200 μmol) on rice (Oryza sativa L.) morphological traits, photosynthesis performance, and the activities of antioxidative enzymes. In addition, the ultrastructure of chloroplasts in the leaves of hydroponically cultivated rice (O. sativa L.) seedlings was analyzed. Plant fresh and dry weights, height, root length, and photosynthetic pigments were decreased by Cr-induced toxicity (200 μM), and the growth of rice seedlings was starkly inhibited compared with that of the control. In addition, the decreased maximum quantum yield of primary photochemistry (Fv/Fm) might be ascribed to the decreased the number of active photosystem II reaction centers. These results were confirmed by inhibited photophosphorylation, reduced ATP content and its coupling factor Ca(2+)-ATPase, and decreased Mg(2+)-ATPase activities. Furthermore, overtly increased activities of antioxidative enzymes were observed under Cr(6+) toxicity. Malondialdehyde and the generation rates of superoxide (O2̄) also increased with Cr(6+) concentration, while hydrogen peroxide content first increased at a low Cr(6+) concentration of 25 μM and then decreased. Moreover, transmission electron microscopy showed that Cr(6+) exposure resulted in significant chloroplast damage. Taken together, these findings indicate that high Cr(6+)concentrations stimulate the production of toxic reactive oxygen species and promote lipid peroxidation in plants, causing severe damage to cell membranes, degradation of photosynthetic pigments, and inhibition of photosynthesis.
Collapse
Affiliation(s)
- Jing Ma
- Jiangsu Key Lab of Biodiversity and Biotechnology, School of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, 210023, Jiangsu, China
| | - Chunfang Lv
- Jiangsu Key Lab of Biodiversity and Biotechnology, School of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, 210023, Jiangsu, China
| | - Minli Xu
- Jiangsu Key Lab of Biodiversity and Biotechnology, School of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, 210023, Jiangsu, China
| | - Guoxiang Chen
- Jiangsu Key Lab of Biodiversity and Biotechnology, School of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, 210023, Jiangsu, China
| | - Chuangen Lv
- Institute of Food and Crops, Jiangsu Academy of Agricultural Sciences, 50 Zhongling Street, Nanjing, 210014, China
| | - Zhiping Gao
- Jiangsu Key Lab of Biodiversity and Biotechnology, School of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, 210023, Jiangsu, China.
| |
Collapse
|
15
|
Buchert F, Konno H, Hisabori T. Redox regulation of CF1-ATPase involves interplay between the γ-subunit neck region and the turn region of the βDELSEED-loop. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:441-450. [PMID: 25660164 DOI: 10.1016/j.bbabio.2015.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/23/2014] [Accepted: 01/27/2015] [Indexed: 11/26/2022]
Abstract
The soluble F1 complex of ATP synthase (FoF1) is capable of ATP hydrolysis, accomplished by the minimum catalytic core subunits α3β3γ. A special feature of cyanobacterial F1 and chloroplast F1 (CF1) is an amino acid sequence inserted in the γ-subunit. The insertion is extended slightly into the CF1 enzyme containing two additional cysteines for regulation of ATPase activity via thiol modulation. This molecular switch was transferred to a chimeric F1 by inserting the cysteine-containing fragment from spinach CF1 into a cyanobacterial γ-subunit [Y. Kim et al., redox regulation of rotation of the cyanobacterial F1-ATPase containing thiol regulation switch, J Biol Chem, 286 (2011) 9071-9078]. Under oxidizing conditions, the obtained F1 tends to lapse into an ADP-inhibited state, a common regulation mechanism to prevent wasteful ATP hydrolysis under unfavorable circumstances. However, the information flow between thiol modulation sites on the γ-subunit and catalytic sites on the β-subunits remains unclear. Here, we clarified a possible interplay for the CF1-ATPase redox regulation between structural elements of the βDELSEED-loop and the γ-subunit neck region, i.e., the most convex part of the α-helical γ-termini. Critical residues were assigned on the β-subunit, which received the conformation change signal produced by disulfide/dithiol formation on the γ-subunit. Mutant response to the ATPase redox regulation ranged from lost to hypersensitive. Furthermore, mutant cross-link experiments and inversion of redox regulation indicated that the γ-redox state might modulate the subunit interface via reorientation of the βDELSEED motif region.
Collapse
Affiliation(s)
- Felix Buchert
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Hiroki Konno
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan; Imaging Research Division, Bio-AFM Frontier Research Center, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
| | - Toru Hisabori
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan.
| |
Collapse
|
16
|
Bauermeister H, Schlodder E, Gräber P. Electric Field-Driven ATP Synthesis Catalyzed by the Membrane-Bound ATP-Synthase from Chloroplasts. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.198800258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
17
|
The Arabidopsis pentatricopeptide repeat protein PDM1 is associated with the intergenic sequence of S11-rpoA for rpoA monocistronic RNA cleavage. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11434-012-5278-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
|
18
|
Konno H, Nakane T, Yoshida M, Ueoka-Nakanishi H, Hara S, Hisabori T. Thiol modulation of the chloroplast ATP synthase is dependent on the energization of thylakoid membranes. PLANT & CELL PHYSIOLOGY 2012; 53:626-34. [PMID: 22362842 DOI: 10.1093/pcp/pcs018] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Thiol modulation of the chloroplast ATP synthase γ subunit has been recognized as an important regulatory system for the activation of ATP hydrolysis activity, although the physiological significance of this regulation system remains poorly characterized. Since the membrane potential required by this enzyme to initiate ATP synthesis for the reduced enzyme is lower than that needed for the oxidized form, reduction of this enzyme was interpreted as effective regulation for efficient photophosphorylation. However, no concrete evidence has been obtained to date relating to the timing and mode of chloroplast ATP synthase reduction and oxidation in green plants. In this study, thorough analysis of the redox state of regulatory cysteines of the chloroplast ATP synthase γ subunit in intact chloroplasts and leaves shows that thiol modulation of this enzyme is pivotal in prohibiting futile ATP hydrolysis activity in the dark. However, the physiological importance of efficient ATP synthesis driven by the reduced enzyme in the light could not be demonstrated. In addition, we investigated the significance of the electrochemical proton gradient in reducing the γ subunit by the reduced form of thioredoxin in chloroplasts, providing strong insights into the molecular mechanisms underlying the formation and reduction of the disulfide bond on the γ subunit in vivo.
Collapse
Affiliation(s)
- Hiroki Konno
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-Ku, Yokohama, Japan
| | | | | | | | | | | |
Collapse
|
19
|
Gao ZP, Yu QB, Zhao TT, Ma Q, Chen GX, Yang ZN. A functional component of the transcriptionally active chromosome complex, Arabidopsis pTAC14, interacts with pTAC12/HEMERA and regulates plastid gene expression. PLANT PHYSIOLOGY 2011; 157:1733-45. [PMID: 22010110 PMCID: PMC3327189 DOI: 10.1104/pp.111.184762] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 10/14/2011] [Indexed: 05/18/2023]
Abstract
The SET domain-containing protein, pTAC14, was previously identified as a component of the transcriptionally active chromosome (TAC) complexes. Here, we investigated the function of pTAC14 in the regulation of plastid-encoded bacterial-type RNA polymerase (PEP) activity and chloroplast development. The knockout of pTAC14 led to the blockage of thylakoid formation in Arabidopsis (Arabidopsis thaliana), and ptac14 was seedling lethal. Sequence and transcriptional analysis showed that pTAC14 encodes a specific protein in plants that is located in the chloroplast associated with the thylakoid and that its expression depends on light. In addition, the transcript levels of all investigated PEP-dependent genes were clearly reduced in the ptac14-1 mutants, while the accumulation of nucleus-encoded phage-type RNA polymerase-dependent transcripts was increased, indicating an important role of pTAC14 in maintaining PEP activity. pTAC14 was found to interact with pTAC12/HEMERA, another component of TACs that is involved in phytochrome signaling. The data suggest that pTAC14 is essential for proper chloroplast development, most likely by affecting PEP activity and regulating PEP-dependent plastid gene transcription in Arabidopsis together with pTAC12.
Collapse
|
20
|
Oja V, Eichelmann H, Laisk A. The size of the lumenal proton pool in leaves during induction and steady-state photosynthesis. PHOTOSYNTHESIS RESEARCH 2011; 110:73-88. [PMID: 22002818 DOI: 10.1007/s11120-011-9697-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 09/28/2011] [Indexed: 05/16/2023]
Abstract
This report describes a new method to measure the chloroplastic lumenal proton pool in leaves (tobacco and sunflower). The method is based on measurement of CO(2) outbursts from leaves caused by the shift in the CO(2) + H(2)O ↔ HCO(3)(-) + H(+) equilibrium in the chloroplast stroma as protons return from the lumen after darkening. Protons did not accumulate in the lumen to a significant extent when photosynthesis was light-limited, but a large pool of >100 μmol H(+) m(-2) accumulated in the lumen as photosynthesis became light-saturated. During thylakoid energization in the light, large amounts of protons are moved from binding sites in the stroma to binding sites in the lumen. The transthylakoidal difference in the chemical potential of free protons (ΔpH) is largely based on the difference in the chemical potential of bound protons in the lumenal and stromal compartments (pK). Over the course of the dark-light induction of photosynthesis protons accumulate in the lumen during reduction of 3-phosphoglycerate. The accumulation of electrons in reduced compounds of the stroma and cytosol is the natural cause for accumulation of a stoichiometric pool of lumenal protons during this transient event.
Collapse
Affiliation(s)
- Vello Oja
- Institute of Molecular and Cellular Biology, University of Tartu, Riia St. 23, 51010 Tartu, Estonia
| | | | | |
Collapse
|
21
|
Chattopadhyay A, Subba P, Pandey A, Bhushan D, Kumar R, Datta A, Chakraborty S, Chakraborty N. Analysis of the grasspea proteome and identification of stress-responsive proteins upon exposure to high salinity, low temperature, and abscisic acid treatment. PHYTOCHEMISTRY 2011; 72:1293-307. [PMID: 21353267 DOI: 10.1016/j.phytochem.2011.01.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 01/08/2011] [Accepted: 01/17/2011] [Indexed: 05/18/2023]
Abstract
Abiotic stress causes diverse biochemical and physiological changes in plants and limits crop productivity. Plants respond and adapt to such stress by altering their cellular metabolism and activating various defense machineries. To understand the molecular basis of stress tolerance in plants, we have developed differential proteomes in a hardy legume, grasspea (Lathyrus sativus L.). Five-week-old grasspea seedlings were subjected independently to high salinity, low temperature and abscisic acid treatment for duration of 36h. The physiological changes of stressed seedlings were monitored, and correlated with the temporal changes of proteome using two-dimensional gel electrophoresis. Approximately, 400 protein spots were detected in each of the stress proteome with one-fourth showing more than 2-fold differences in expression values. Eighty such proteins were subjected to LC-tandem MS/MS analyses that led to the identification of 48 stress-responsive proteins (SRPs) presumably involved in a variety of functions, including metabolism, signal transduction, protein biogenesis and degradation, and cell defense and rescue. While 33 proteins were responsive to all three treatments, 15 proteins were expressed in stress-specific manner. Further, we explored the possible role of ROS in triggering the stress-induced degradation of large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase (Rubisco). These results might help in understanding the spectrum of stress-regulated proteins and the biological processes they control as well as having implications for strategies to improve stress adaptation in plants.
Collapse
Affiliation(s)
- Arnab Chattopadhyay
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Buchert F, Forreiter C. Singlet oxygen inhibits ATPase and proton translocation activity of the thylakoid ATP synthase CF1CFo. FEBS Lett 2010; 584:147-52. [PMID: 19925794 DOI: 10.1016/j.febslet.2009.11.040] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Revised: 10/30/2009] [Accepted: 11/12/2009] [Indexed: 11/26/2022]
Abstract
Singlet oxygen ((1)O(2)) produced in plants during photosynthesis has a strong damaging effect not only on both photosystems but also on the whole photosynthetic machinery. This is also applicable for the adenosine triphosphate (ATP) synthase. Here we describe the impact of (1)O(2) generated by the photosensitizer Rose Bengal on the ATP hydrolysis and ATP-driven proton translocation activity of CF1CFo. Both activities were reduced dramatically within 1min of exposure. Interestingly, it is shown that oxidized thylakoid ATP synthase is more susceptible to (1)O(2) than CF1CFo in its reduced state, a new insight on the mechanism of (1)O(2) interaction with the gamma subunit.
Collapse
Affiliation(s)
- Felix Buchert
- Pflanzenphysiologie, Justus-Liebig Universität, Zeughaus, Giessen, Germany
| | | |
Collapse
|
23
|
Wu G, Ort DR. Mutation in the cysteine bridge domain of the gamma-subunit affects light regulation of the ATP synthase but not photosynthesis or growth in Arabidopsis. PHOTOSYNTHESIS RESEARCH 2008; 97:185-193. [PMID: 18566910 DOI: 10.1007/s11120-008-9315-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Accepted: 05/22/2008] [Indexed: 05/26/2023]
Abstract
The chloroplast ATP synthase synthesizes ATP from ADP and free phosphate coupled by the electrochemical potential across the thylakoid membrane in the light. The light-dependent regulation of ATP synthase activity is carried out in part through redox modulation of a cysteine disulfide bridge in CF1 gamma-subunit. In order to investigate the function of the redox regulatory domain and the physiological significance of redox modulation for higher plants, we designed four mutations in the redox regulatory domain of the gamma-subunit to create functional mimics of the permanently reduced form of the gamma-subunit. While the inability to reduce the regulatory disulfide results in lower photosynthesis and growth, unexpectedly, the results reported here show that inability to reoxidize the dithiol may not be of any direct detriment to plant photosynthetic performance or growth.
Collapse
Affiliation(s)
- Guosheng Wu
- Department of Plant Biology, University of Illinois, 1201 W. Gregory Dr., Urbana, IL 61801, USA
| | | |
Collapse
|
24
|
Samra HS, He F, Degner NR, Richter ML. The role of specific beta-gamma subunit interactions in oxyanion stimulation of the MgATP hydrolysis of a hybrid photosynthetic F1-ATPase. J Bioenerg Biomembr 2008; 40:69-76. [PMID: 18415008 DOI: 10.1007/s10863-008-9131-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 01/09/2008] [Indexed: 11/25/2022]
Abstract
Pairs of cysteine residues were introduced into the twisted N- and C-terminal helices of the gamma subunit of the chloroplast F1-ATPase to test, via disulfide cross-linking, potential inter-helical movements involved in catalysis of ATP hydrolysis. The extent of disulfide cross-linking was determined by estimating the amount of free sulfhydryl available for labeling with fluoresceinyl maleimide before and after cross-linking. Significant disulfide formation (50-75%) was observed between cysteines introduced at positions 30 and 31 in the N-terminal helix and 276 and 278 in the C-terminal helix. Cross-linking had no apparent effect on catalysis, therefore eliminating the involvement of large-scale inter-helical movements within this region of the gamma subunit in cooperative ATP hydrolysis. However, the presence of the two cysteines together in the gammaV31C/A276C double mutant, irrespective of whether or not they were cross-linked together, lowered the MgATPase activity by more than 70% and completely eliminated the well-known activating effect of the oxyanion sulfite. The CaATPase activity was unaffected. Similar but less pronounced effects were seen with the gammaK30C/A276C double mutant. The results indicate that residues at or near positions 31 and 276 within the twisted helical pair of the gamma subunit are required to overcome Mg2+ inhibition of ATP hydrolysis. These residues are likely to be involved in forming a point of contact between the gamma and beta subunits that is responsible for this effect.
Collapse
Affiliation(s)
- Hardeep S Samra
- Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
| | | | | | | |
Collapse
|
25
|
Datiles MJ, Johnson EA, McCarty RE. Inhibition of the ATPase activity of the catalytic portion of ATP synthases by cationic amphiphiles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:362-8. [DOI: 10.1016/j.bbabio.2008.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 12/05/2007] [Accepted: 01/22/2008] [Indexed: 10/22/2022]
|
26
|
The thermodynamic H+/ATP ratios of the H+-ATPsynthases from chloroplasts and Escherichia coli. Proc Natl Acad Sci U S A 2008; 105:3745-50. [PMID: 18316723 DOI: 10.1073/pnas.0708356105] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The H(+)/ATP ratio is an important parameter for the energy balance of all cells and for the coupling mechanism between proton transport and ATP synthesis. A straightforward interpretation of rotational catalysis predicts that the H(+)/ATP coincides with the ratio of the c-subunits to beta-subunits, implying that, for the chloroplast and Escherichia coli ATPsynthases, numbers of 4.7 and 3.3 are expected. Here, the energetics described by the chemiosmotic theory was used to determine the H(+)/ATP ratio for the two enzymes. The isolated complexes were reconstituted into liposomes, and parallel measurements were performed under identical conditions. The internal phase of the liposomes was equilibrated with the acidic medium during reconstitution, allowing to measure the internal pH with a glass electrode. An acid-base transition was carried out and the initial rates of ATP synthesis or ATP hydrolysis were measured with luciferin/luciferase as a function of DeltapH at constant Q = [ATP]/([ADP][P(i)]). From the shift of the equilibrium DeltapH as a function of Q the standard Gibbs free energy for phosphorylation, DeltaG(p)(0)'; and the H(+)/ATP ratio were determined. It resulted DeltaG(p)(0)' = 38 +/- 3 kJ.mol(-1) and H(+)/ATP = 4.0 +/- 0.2 for the chloroplast and H(+)/ATP = 4.0 +/- 0.3 for the E. coli enzyme, indicating that the thermodynamic H(+)/ATP ratio is the same for both enzymes and that it is different from the subunit stoichiometric ratio.
Collapse
|
27
|
He F, Samra HS, Johnson EA, Degner NR, McCarty RE, Richter ML. C-Terminal mutations in the chloroplast ATP synthase gamma subunit impair ATP synthesis and stimulate ATP hydrolysis. Biochemistry 2007; 47:836-44. [PMID: 18092810 DOI: 10.1021/bi701581y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two highly conserved amino acid residues, an arginine and a glutamine, located near the C-terminal end of the gamma subunit, form a "catch" by hydrogen bonding with residues in an anionic loop on one of the three catalytic beta subunits of the bovine mitochondrial F1-ATPase [Abrahams, J. P., Leslie, A. G., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628]. The catch is considered to play a critical role in the binding change mechanism whereby binding of ATP to one catalytic site releases the catch and induces a partial rotation of the gamma subunit. This role is supported by the observation that mutation of the equivalent arginine and glutamine residues in the Escherichia coli F1 gamma subunit drastically reduced all ATP-dependent catalytic activities of the enzyme [Greene, M. D., and Frasch, W. D. (2003) J. Biol. Chem. 278, 5194-5198]. In this study, we show that simultaneous substitution of the equivalent residues in the chloroplast F1 gamma subunit, arginine 304 and glutamine 305, with alanine decreased the level of proton-coupled ATP synthesis by more than 80%. Both the Mg2+-dependent and Ca2+-dependent ATP hydrolysis activities increased by more than 3-fold as a result of these mutations; however, the sulfite-stimulated activity decreased by more than 60%. The Mg2+-dependent, but not the Ca2+-dependent, ATPase activity of the double mutant was insensitive to inhibition by the phytotoxic inhibitor tentoxin, indicating selective loss of catalytic cooperativity in the presence of Mg2+ ions. The results indicate that the catch residues are required for efficient proton coupling and for activation of multisite catalysis when MgATP is the substrate. The catch is not, however, required for CaATP-driven multisite catalysis or, therefore, for rotation of the gamma subunit.
Collapse
Affiliation(s)
- Feng He
- Department of Molecular Biosciences, The University of Kansas, Lawrence, Kansas 66045, USA
| | | | | | | | | | | |
Collapse
|
28
|
Wu G, Ortiz-Flores G, Ortiz-Lopez A, Ort DR. A Point Mutation in atpC1 Raises the Redox Potential of the Arabidopsis Chloroplast ATP Synthase γ-Subunit Regulatory Disulfide above the Range of Thioredoxin Modulation. J Biol Chem 2007; 282:36782-9. [DOI: 10.1074/jbc.m707007200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
|
29
|
McCallum JR, McCarty RE. Proton flux through the chloroplast ATP synthase is altered by cleavage of its gamma subunit. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:974-9. [PMID: 17559799 DOI: 10.1016/j.bbabio.2007.04.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 04/02/2007] [Accepted: 04/23/2007] [Indexed: 11/21/2022]
Abstract
Electron transport, the proton gradient and ATP synthesis were determined in thylakoids that had been briefly exposed to a low concentration of trypsin during illumination. This treatment cleaves the gamma subunit of the ATP synthase into two large fragments that remain associated with the enzyme. Higher rates of electron transport are required to generate a given value of the proton gradient in the trypsin-treated membranes than in control membranes, indicating that the treated membranes are proton leaky. Since venturicidin restores electron transport and the proton gradient to control levels, the proton leak is through the ATP synthase. Remarkably, the synthesis of ATP by the trypsin-treated membranes at saturating light intensities is only slightly inhibited even though the proton gradient is significantly lower in the treated thylakoids. ATP synthesis and the proton gradient were determined as a function of light intensity in control and trypsin-treated thylakoids. The trypsin-treated membranes synthesized ATP at lower values of the proton gradient than the control membranes. Cleavage of the gamma subunit abrogates inhibition of the activity of the chloroplast ATP synthase by the epsilon subunit. Our results suggest that overcoming inhibition by the epsilon subunit costs energy.
Collapse
Affiliation(s)
- Jeremy R McCallum
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | | |
Collapse
|
30
|
Zhang CJ, Chu HJ, Chen GX, Shi DW, Zuo M, Wang J, Lu CG, Wang P, Chen L. Photosynthetic and biochemical activities in flag leaves of a newly developed superhigh-yield hybrid rice (Oryza sativa) and its parents during the reproductive stage. JOURNAL OF PLANT RESEARCH 2007; 120:209-17. [PMID: 17077941 DOI: 10.1007/s10265-006-0038-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Accepted: 08/16/2006] [Indexed: 05/08/2023]
Abstract
Responses of net photosynthetic rates to intercellular CO(2) concentration (P (n)/C (i) curves) and photochemical characteristics were investigated in flag leaves of newly developed superhigh-yield hybrid rice (Oryza sativa L.) LiangYouPeiJiu (LYPJ) and its maternal PeiAi64S (PA64S) and paternal WuMang9311 (WM9311) lines grown in the field during the reproductive stage. The results showed that photosynthetic functions, such as the electron transport activities of photosystems and photophosphorylation, assessed in vivo from P (n)/C (i) curves under field conditions declined more or earlier than those obtained in vitro. The degradation of polypeptides of thylakoid membranes was slower than those for P (Ca=360) (light-saturated net photosynthetic rate measured at 360 mumol mol(-1)) and CE (carboxylation efficiency, obtained from the initial slope of the P (n)/C (i) curve). The initial inhibition of the PSII electron transport and oxygen-evolving activity induced by senescence occurred before the degradation of the oxygen-evolving complex. In comparison, LYPJ had intermediate photosynthetic functions in the early stage of leaf development, but greater photochemical activities in the mid and late stages. WM9311 showed a similar pattern of changes but lower values, and PA64S had higher values in the early stage but showed a faster rate of senescence than LYPJ. These findings implied that the hybrid LYPJ demonstrated intermediate photosynthetic activities between its parents in the early stage of leaf development, whereas it had higher photosynthetic activities than its parents in the mid and late stages, which may be responsible for its high yield.
Collapse
Affiliation(s)
- C-J Zhang
- Key Lab of Biodiversity and Biotechnology of Jiangsu Province, College of Life Sciences, Nanjing Normal University, Nanjing, PR China
| | | | | | | | | | | | | | | | | |
Collapse
|
31
|
McCarty RE. The decay of the ATPase activity of light plus thiol-activated thylakoid membranes in the dark. J Bioenerg Biomembr 2006; 38:67-74. [PMID: 16775764 DOI: 10.1007/s10863-006-9007-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Oxidized ATP synthase of spinach thylakoid membranes catalyzes high rates of ATP synthesis in the light, but very low rates of ATP hydrolysis in the dark. Reduction of the disulfide bond in the gamma subunit of the ATP synthase in the light enhances the rate of Mg2+-ATP hydrolysis in the dark. The light plus thiol-activated state decays in a few minutes in the dark after illumination in Tris buffer, but not when Tricine was used in place of Tris. In this paper, it is shown that Tris in the assay mixture is an inhibitor of the light plus thiol-activated ATPase activity of thylakoids, but only after the activated membranes had incubated in the dark. Aminopropanediols and diethanolamine, also selectively inhibited ATPase activity of activated membranes after storage in the dark, whereas NH4Cl and imidazole inhibit the ATPase activity of activated thylakoids almost equally whether they are added directly after the illumination or several minutes later. The fluorescence of 9-amino-6-chloro-2-methoxyacridine (ACMA) is quenched by the establishment of proton gradients by ATP-dependent proton uptake. Addition of ATP to activated membranes results in rapid quenching of ACMA fluorescence. If the activated membranes were incubated in the dark prior to ATP addition, a lag in the ATP-dependent ACMA fluorescence quenching as well as a similar lag in the rate ATP hydrolysis were seen. It is concluded that ADP rebinds to CF1 in the dark following illumination and inhibits the activity of the ATP synthase. Reactivation of the ATP synthase in the dark can occur by the slow generation of proton gradients by ATP hydrolysis in the dark. This reactivation takes place in Tricine buffer, but not in Tris because of its uncoupling action. Whether ADP binding plays a role in the regulation of the activity of the ATP synthase in situ remains to be established.
Collapse
Affiliation(s)
- Richard E McCarty
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
| |
Collapse
|
32
|
Samra HS, Gao F, He F, Hoang E, Chen Z, Gegenheimer PA, Berrie CL, Richter ML. Structural Analysis of the Regulatory Dithiol-containing Domain of the Chloroplast ATP Synthase γ Subunit. J Biol Chem 2006; 281:31041-9. [PMID: 16895914 DOI: 10.1074/jbc.m603315200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma subunit of the F1 portion of the chloroplast ATP synthase contains a critically placed dithiol that provides a redox switch converting the enzyme from a latent to an active ATPase. The switch prevents depletion of intracellular ATP pools in the dark when photophosphorylation is inactive. The dithiol is located in a special regulatory segment of about 40 amino acids that is absent from the gamma subunits of the eubacterial and mitochondrial enzymes. Site-directed mutagenesis was used to probe the relationship between the structure of the gamma regulatory segment and its function in ATPase regulation via its interaction with the inhibitory epsilon subunit. Mutations were designed using a homology model of the chloroplast gamma subunit based on the analogous structures of the bacterial and mitochondrial homologues. The mutations included (a) substituting both of the disulfide-forming cysteines (Cys199 and Cys205) for alanines, (b) deleting nine residues containing the dithiol, (c) deleting the region distal to the dithiol (residues 224-240), and (d) deleting the entire segment between residues 196 and 241 with the exception of a small spacer element, and (e) deleting pieces from a small loop segment predicted by the model to interact with the dithiol domain. Deletions within the dithiol domain and within parts of the loop segment resulted in loss of redox control of the ATPase activity of the F1 enzyme. Deleting the distal segment, the whole regulatory domain, or parts of the loop segment had the additional effect of reducing the maximum extent of inhibition obtained upon adding the epsilon subunit but did not abolish epsilon binding. The results suggest a mechanism by which the gamma and epsilon subunits interact with each other to induce the latent state of the enzyme.
Collapse
Affiliation(s)
- Hardeep S Samra
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Richter ML, Samra HS, He F, Giessel AJ, Kuczera KK. Coupling proton movement to ATP synthesis in the chloroplast ATP synthase. J Bioenerg Biomembr 2006; 37:467-73. [PMID: 16691485 DOI: 10.1007/s10863-005-9493-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The chloroplast F(0)F(1)-ATP synthase-ATPase is a tiny rotary motor responsible for coupling ATP synthesis and hydrolysis to the light-driven electrochemical proton gradient. Reversible oxidation/reduction of a dithiol, located within a special regulatory domain of the gamma subunit of the chloroplast F(1) enzyme, switches the enzyme between an inactive and an active state. This regulatory mechanism is unique to the ATP synthases of higher plants and its physiological significance lies in preventing nonproductive depletion of essential ATP pools in the dark. The three-dimensional structure of the chloroplast F(1) gamma subunit has not yet been solved. To examine the mechanism of dithiol regulation, a model of the chloroplast gamma subunit was obtained through segmental homology modeling based on the known structures of the mitochondrial and bacterial gamma subunits, together with de novo construction of the unknown regulatory domain. The model has provided considerable insight into how the dithiol might modulate catalytic function. This has, in turn, suggested a mechanism by which rotation of subunits in F(0), the transmembrane proton channel portion of the enzyme, can be coupled, via the epsilon subunit, to rotation of the gamma subunit of F(1) to achieve the 120 degrees (or 90 degrees +30 degrees) stepping action that is characteristic of F(1) gamma subunit rotation.
Collapse
Affiliation(s)
- Mark L Richter
- Departments of Chemistry and Molecular Biosciences, The University of Kansas, Lawrence, Kansas 66045, USA.
| | | | | | | | | |
Collapse
|
34
|
Gong P, Wu G, Ort DR. Slow dark deactivation of Arabidopsis chloroplast ATP synthase caused by a mutation in a nonplastidic SAC domain protein. PHOTOSYNTHESIS RESEARCH 2006; 88:133-42. [PMID: 16453058 DOI: 10.1007/s11120-006-9041-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Accepted: 01/08/2006] [Indexed: 05/06/2023]
Abstract
Coupling factor slow recovery (cfs) is a recessive mutant of Arabidopsis with anomalous ATP synthase activation/deactivation characteristics as well as a distinct growth phenotype. The most significant feature of this mutant is that the dark-adapted deactivation of ATP synthase is a very slow relative to the wild type, indicating interference with ATP synthase regulation. Physical mapping of the mutation delimited it to a region in a pair of bacterial artificial chromosome clones. Examination of T-DNA insertion lines of all 34 putative genes located in this region identified two homozygous T-DNA insertion lines of the same gene, At3g59770, possessing phenotypes indistinguishable from the cfs mutant. At3g59770 had been previously identified as suppressor of actin 9 (SAC9), a protein with a SAC domain, a protein-protein interaction module containing two conserved tryptophans known as a WW domain, and an ATP/GTP-binding site motif A. Sequence analysis of cfs revealed a point mutation of G to A resulting in an amino acid substitution from tryptophan to STOP, thereby coding a truncated protein. Real-time-PCR amplification of the gene specific fragments showed that the T-DNA mutants did not have full-length transcripts whereas the cfs mutant transcribed a full-length mutated transcript. Further investigation of SAC9 RNA expression levels in different tissues of wild-type plants by RT-PCR revealed the highest expression in leaves. SAC 9 dysfunction interferes with ATP synthase deactivation, possibly by an alteration in phosphoinositide signaling inducing a stress mimicry response.
Collapse
Affiliation(s)
- Ping Gong
- Department of Plant Biology, University of Illinois, 190 ERML, Urbana, IL 61801, USA
| | | | | |
Collapse
|
35
|
Wilhelm C, Büchel C, Fisahn J, Goss R, Jakob T, Laroche J, Lavaud J, Lohr M, Riebesell U, Stehfest K, Valentin K, Kroth PG. The regulation of carbon and nutrient assimilation in diatoms is significantly different from green algae. Protist 2006; 157:91-124. [PMID: 16621693 DOI: 10.1016/j.protis.2006.02.003] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Christian Wilhelm
- Department of Plant Physiology, Institute of Biology I, University of Leipzig, Johannisallee 23, 04103 Leipzig, Germany.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Feniouk BA, Suzuki T, Yoshida M. The role of subunit epsilon in the catalysis and regulation of FOF1-ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:326-38. [PMID: 16701076 DOI: 10.1016/j.bbabio.2006.03.022] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/13/2006] [Accepted: 03/30/2006] [Indexed: 10/24/2022]
Abstract
The regulation of ATP synthase activity is complex and involves several distinct mechanisms. In bacteria and chloroplasts, subunit epsilon plays an important role in this regulation, (i) affecting the efficiency of coupling, (ii) influencing the catalytic pathway, and (iii) selectively inhibiting ATP hydrolysis activity. Several experimental studies indicate that the regulation is achieved through large conformational transitions of the alpha-helical C-terminal domain of subunit epsilon that occur in response to membrane energization, change in ATP/ADP ratio or addition of inhibitors. This review summarizes the experimental data obtained on different organisms that clarify some basic features as well as some molecular details of this regulatory mechanism. Multiple functions of subunit epsilon, its role in the difference between the catalytic pathways of ATP synthesis and hydrolysis and its influence on the inhibition of ATP hydrolysis by ADP are also discussed.
Collapse
Affiliation(s)
- Boris A Feniouk
- ATP System Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation (JST), 5800-3 Nagatsuta, Midori-ku, Yokohama 226-0026, Japan.
| | | | | |
Collapse
|
37
|
Richter M, Daufenbach J, Drebing S, Vucetic V, Nguyen DT. Light-induced proton slip and proton leak at the thylakoid membrane. JOURNAL OF PLANT PHYSIOLOGY 2004; 161:1325-1337. [PMID: 15658803 DOI: 10.1016/j.jplph.2004.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A treatment of leaves of Spinacia oleracea L. with light or with the thiol reagent dithiothreitol in the dark led to partly uncoupled thylakoids. After induction in intact leaves, the partial uncoupling was irreversible at the level of isolated thylakoids. We distinguish between uncoupling by proton slip, which means a decrease of the H+/e(-) -ratio due to less efficient proton pumping, and proton leak as defined by enhanced kinetics of proton efflux. Proton slip and proton leak made about equal contributions to the total uncoupling. The enhanced proton efflux kinetics corresponded to reduction of subunit CF1-gamma of the ATP synthase as shown by fluorescence labeling of thylakoid proteins with the sulfhydryl probe 5-iodoacetamido fluorescein. The maximum value of the fraction of reduced CF1-gamma was only 36%, which indicates that in vivo the reduction of CF1-gamma could be limited by fast reoxidation and/or restricted accessibility of CF1-gamma to thioredoxin. Measurements of the ratio ATP/2e indicated that only the uncoupling related to less efficient proton pumping led to a decrease in the ATP yield.
Collapse
Affiliation(s)
- Michael Richter
- Institut für Allgemeine Botanik, Johannes Gutenberg Universität, D-55099 Mainz, Germany.
| | | | | | | | | |
Collapse
|
38
|
Konno H, Suzuki T, Bald D, Yoshida M, Hisabori T. Significance of the epsilon subunit in the thiol modulation of chloroplast ATP synthase. Biochem Biophys Res Commun 2004; 318:17-24. [PMID: 15110747 DOI: 10.1016/j.bbrc.2004.03.179] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2004] [Indexed: 11/24/2022]
Abstract
To understand the regulatory function of the gamma and epsilon subunits of chloroplast ATP synthase in the membrane integrated complex, we constructed a chimeric FoF1 complex of thermophilic bacteria. When a part of the chloroplast F1 gamma subunit was introduced into the bacterial FoF1 complex, the inverted membrane vesicles with this chimeric FoF1 did not exhibit the redox sensitive ATP hydrolysis activity, which is a common property of the chloroplast ATP synthase. However, when the whole part or the C-terminal alpha-helices region of the epsilon subunit was substituted with the corresponding region from CF1-epsilon together with the mutation of gamma, the redox regulation property emerged. In contrast, ATP synthesis activity did not become redox sensitive even if both the regulatory region of CF1-gamma and the entire epsilon subunit from CF1 were introduced. These results provide important features for the regulation of FoF1 by these subunits: (1) the interaction between gamma and epsilon is important for the redox regulation of FoF1 complex by the gamma subunit, and (2) a certain structural matching between these regulatory subunits and the catalytic core of the enzyme must be required to confer the complete redox regulation mechanism to the bacterial FoF1. In addition, a structural requirement for the redox regulation of ATP hydrolysis activity might be different from that for the ATP synthesis activity.
Collapse
Affiliation(s)
- Hiroki Konno
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | | | | | | | | |
Collapse
|
39
|
Nowak KF, McCarty RE. Regulatory role of the C-terminus of the epsilon subunit from the chloroplast ATP synthase. Biochemistry 2004; 43:3273-9. [PMID: 15023078 DOI: 10.1021/bi035820d] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ATP synthases from chloroplasts and Escherichia coli are regulated by several factors, one of which is the epsilon subunit. This small subunit is also required for ATP synthesis. Thylakoid membranes reconstituted with CF1 lacking the epsilon subunit (CF1-epsilon) exhibit no ATP synthesis and very high ATP hydrolysis. Either native or recombinant epsilon restores ATP synthesis and inhibits ATP hydrolysis. Previously, we showed that truncated epsilon, lacking the last 45 C-terminal amino acids, restored ATP synthesis to membranes reconstituted with CF1-epsilon but was not an efficient inhibitor of ATP hydrolysis. In this paper, we show that this truncated epsilon is unable to inhibit ATP hydrolysis when Mg(2+) is the divalent cation present, both for the enzyme in solution and on the thylakoid membrane. In addition, the rate of reduction of the disulfide bond of the gamma subunit by dithiothreitol is not decreased by truncated epsilon, although full-length epsilon greatly impedes reduction. Thylakoid membranes can synthesize ATP at the expense of proton gradients generated by pH transitions in the dark. Our reconstituted membranes are able to produce a limited amount of ATP under these "acid-bath" conditions, with approximately equal amounts produced by the membranes containing wild-type epsilon and those containing truncated epsilon. However, the membranes containing truncated epsilon exhibit much higher background ATP hydrolysis under the same acid-bath conditions, leading to the conclusion that, without the C-terminus of epsilon, the CF1CFo is unable to check unwanted ATP hydrolysis.
Collapse
Affiliation(s)
- Kristine F Nowak
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218-2685, USA
| | | |
Collapse
|
40
|
Dal Bosco C, Lezhneva L, Biehl A, Leister D, Strotmann H, Wanner G, Meurer J. Inactivation of the chloroplast ATP synthase gamma subunit results in high non-photochemical fluorescence quenching and altered nuclear gene expression in Arabidopsis thaliana. J Biol Chem 2003; 279:1060-9. [PMID: 14576160 DOI: 10.1074/jbc.m308435200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The nuclear atpC1 gene encoding the gamma subunit of the plastid ATP synthase has been inactivated by T-DNA insertion mutagenesis in Arabidopsis thaliana. In the seedling-lethal dpa1 (deficiency of plastid ATP synthase 1) mutant, the absence of detectable amounts of the gamma subunit destabilizes the entire ATP synthase complex. The expression of a second gene copy, atpC2, is unaltered in dpa1 and is not sufficient to compensate for the lack of atpC1 expression. However, in vivo protein labeling analysis suggests that assembly of the ATP synthase alpha and beta subunits into the thylakoid membrane still occurs in dpa1. As a consequence of the destabilized ATP synthase complex, photophosphorylation is abolished even under reducing conditions. Further effects of the mutation include an increased light sensitivity of the plant and an altered photosystem II activity. At low light intensity, chlorophyll fluorescence induction kinetics is close to those found in wild type, but non-photochemical quenching strongly increases with increasing actinic light intensity resulting in steady state fluorescence levels of about 60% of the minimal dark fluorescence. Most fluorescence quenching relaxed within 3 min after dark incubation. Spectroscopic and biochemical studies have shown that a high proton gradient is responsible for most quenching. Thylakoids of illuminated dpa1 plants were swollen due to an increased proton accumulation in the lumen. Expression profiling of 3292 nuclear genes encoding mainly chloroplast proteins demonstrates that most organelle functions are down-regulated. On the contrary, the mRNA expression of some photosynthesis genes is significantly up-regulated, probably to compensate for the defect in dpa1.
Collapse
Affiliation(s)
- Cristina Dal Bosco
- Ludwig-Maximilians-Universität, Department Biologie I, Botanik, Menzingerstrasse 67, 80638 München, Germany
| | | | | | | | | | | | | |
Collapse
|
41
|
Haldrup A, Lunde C, Scheller HV. Arabidopsis thaliana plants lacking the PSI-D subunit of photosystem I suffer severe photoinhibition, have unstable photosystem I complexes, and altered redox homeostasis in the chloroplast stroma. J Biol Chem 2003; 278:33276-83. [PMID: 12794067 DOI: 10.1074/jbc.m305106200] [Citation(s) in RCA: 56] [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
The PSI-D subunit of photosystem I is a hydrophilic subunit of about 18 kDa, which is exposed to the stroma and has an important function in the docking of ferredoxin to photosystem I. We have used an antisense approach to obtain Arabidopsis thaliana plants with only 5-60% of PSI-D. No plants were recovered completely lacking PSI-D, suggesting that PSI-D is essential for a functional PSI in plants. Plants with reduced amounts of PSI-D showed a similar decrease in all other subunits of PSI including the light harvesting complex, suggesting that in the absence of PSI-D, PSI cannot be properly assembled and becomes degraded. Plants with reduced amounts of PSI-D became light-stressed even in low light although they exhibited high non-photochemical quenching (NPQ). The high NPQ was generated by upregulating the level of violaxanthin de-epoxidase and PsbS, which are both essential components of NPQ. Interestingly, the lack of PSI-D affected the redox state of thioredoxin. During the normal light cycle thioredoxin became increasingly oxidized, which was observed as decreasing malate dehydrogenase activity over a 4-h light period. This result shows that photosynthesis was close to normal the first 15 min, but after 2-4 h photoinhibition dominated as the stroma progressively became less reduced. The change in the thiol disulfide redox state might be fatal for the PSI-D-less plants, because reduction of thioredoxin is one of the main switches for the initiation of CO2 assimilation and photoprotection upon light exposure.
Collapse
Affiliation(s)
- Anna Haldrup
- Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
| | | | | |
Collapse
|
42
|
Hisabori T, Ueoka-Nakanishi H, Konno H, Koyama F. Molecular evolution of the modulator of chloroplast ATP synthase: origin of the conformational change dependent regulation. FEBS Lett 2003; 545:71-5. [PMID: 12788494 DOI: 10.1016/s0014-5793(03)00395-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Chloroplast ATP synthase synthesizes ATP by utilizing a proton gradient as an energy supply, which is generated by photosynthetic electron transport. The activity of the chloroplast ATP synthase is regulated in several specific ways to avoid futile hydrolysis of ATP under various physiological conditions. Several regulatory signals such as Delta mu H(+), tight binding of ADP and its release, thiol modulation, and inhibition by the intrinsic inhibitory subunit epsilon are sensed by this complex. In this review, we describe the function of two regulatory subunits, gamma and epsilon, of ATP synthase based on their possible conformational changes and discuss the evolutionary origin of these regulation systems.
Collapse
Affiliation(s)
- Toru Hisabori
- Chemical Resources Laboratory, Tokyo Institute of Technology, and ATP System Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Yokohama, Japan.
| | | | | | | |
Collapse
|
43
|
Nowak KF, Tabidze V, McCarty RE. The C-terminal domain of the epsilon subunit of the chloroplast ATP synthase is not required for ATP synthesis. Biochemistry 2002; 41:15130-4. [PMID: 12484749 DOI: 10.1021/bi026594v] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The epsilon subunit of the ATP synthases from chloroplasts and Escherichia coli regulates the activity of the enzyme and is required for ATP synthesis. The epsilon subunit is not required for the binding of the catalytic portion of the chloroplast ATP synthase (CF1) to the membrane-embedded part (CFo). Thylakoid membranes reconstituted with CF1 lacking its epsilon subunit (CF1-epsilon) have high ATPase activity and no ATP synthesis activity, at least in part because the membranes are very leaky to protons. Either native or recombinant epsilon subunit inhibits ATPase activity and restores low proton permeability and ATP synthesis. In this paper we show that recombinant epsilon subunit from which 45 amino acids were deleted from the C-terminus is as active as full-length epsilon subunit in restoring ATP synthesis to membranes containing CF1-epsilon. However, the truncated form of the epsilon subunit was significantly less effective as an inhibitor of the ATPase activity of CF1-epsilon, both in solution and bound to thylakoid membranes. Thus, the C-terminus of the epsilon subunit is more involved in regulation of activity, by inhibiting ATP hydrolysis, than in ATP synthesis.
Collapse
Affiliation(s)
- Kristine F Nowak
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218-2685, USA
| | | | | |
Collapse
|
44
|
Hisabori T, Konno H, Ichimura H, Strotmann H, Bald D. Molecular devices of chloroplast F(1)-ATP synthase for the regulation. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1555:140-6. [PMID: 12206906 DOI: 10.1016/s0005-2728(02)00269-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In chloroplasts, synthesis of ATP is energetically coupled with the utilization of a proton gradient formed by photosynthetic electron transport. The involved enzyme, the chloroplast ATP synthase, can potentially hydrolyze ATP when the magnitude of the transmembrane electrochemical potential difference of protons (Delta(micro)H(+)) is small, e.g. at low light intensity or in the dark. To prevent this wasteful consumption of ATP, the activity of chloroplast ATP synthase is regulated as the occasion may demand. As regulation systems Delta(micro)H(+) activation, thiol modulation, tight binding of ADP and the role of the intrinsic inhibitory subunit epsilon is well documented. In this article, we discuss recent progress in understanding of the regulation system of the chloroplast ATP synthase at the molecular level.
Collapse
Affiliation(s)
- Toru Hisabori
- Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan.
| | | | | | | | | |
Collapse
|
45
|
Süss KH. Neighbouring subunits of CF0and between CF1and CF0of the soluble chloroplast ATP synthase (CF1-CF0) as revealed by chemical protein cross-linking. FEBS Lett 2001. [DOI: 10.1016/0014-5793(86)80571-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
46
|
Andralojc P, Harris D. Two distinct types of ɛ-binding site exist in chloroplast coupling factor (CF1). FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80471-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
47
|
|
48
|
Evron Y, McCarty RE. Simultaneous measurement of deltapH and electron transport in chloroplast thylakoids by 9-aminoacridine fluorescence. PLANT PHYSIOLOGY 2000; 124:407-14. [PMID: 10982453 PMCID: PMC59153 DOI: 10.1104/pp.124.1.407] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2000] [Accepted: 05/29/2000] [Indexed: 05/22/2023]
Abstract
Electron transport and the electrochemical proton gradient across the thylakoid membrane are two fundamental parameters of photosynthesis. A combination of the electron acceptor, ferricyanide and the DeltapH indicator, 9-aminoacridine, was used to measure simultaneously electron transport rates and DeltapH solely by changes in the fluorescence of 9-aminoacridine. This method yields values for the rate of electron transport that are comparable with those obtained by established methods. Using this method a relationship between the rate of electron transport and DeltapH at various uncoupler concentrations or light intensities was obtained. In addition, the method was used to study the effect of reducing the disulfide bridge in the gamma-subunit of the chloroplast ATP synthase on the relation of electron transport to DeltapH. When the ATP synthase is reduced and alkylated, the threshold DeltapH at which the ATP synthase becomes leaky to protons is lower compared with the oxidized enzyme. Proton flow through the enzyme at a lower DeltapH may be a key step in initiation of ATP synthesis in the reduced enzyme and may be the way by which reduction of the disulfide bridge in the gamma-subunit enables high rates of ATP synthesis at low DeltapH values.
Collapse
Affiliation(s)
- Y Evron
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
| | | |
Collapse
|
49
|
Hutchison RS, Groom Q, Ort DR. Differential effects of chilling-induced photooxidation on the redox regulation of photosynthetic enzymes. Biochemistry 2000; 39:6679-88. [PMID: 10828986 DOI: 10.1021/bi0001978] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photosynthesis in plant species that are evolutionarily adapted for growth in warm climates is highly sensitive to illumination under cool conditions. Although it is well documented that illumination of these sensitive species under cool conditions results in the photosynthetic production of reactive oxygen molecules, the underlying mechanism for the inhibition of photosynthesis remains uncertain. Determinations of chloroplast fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase activity showed that the light-dependent, reductive activation of these key carbon reduction cycle enzymes was substantially inhibited in tomato (Lycopersicon esculentum) following illumination at 4 degrees C. However, other chloroplast enzymes also dependent on thioredoxin-mediated reductive activation were largely unaffected. We performed equilibrium redox titrations to investigate the thermodynamics of the thiol/disulfide exchange between thioredoxin f and the regulatory sulfhydryl groups of fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase, phosphoribulokinase, NADP-glyceraldehyde phosphate dehydrogenase, and the chloroplast ATPsynthase. We determined that the redox midpoint potentials for the regulatory sulfhydryl groups of the various enzymes spanned a broad range ( approximately 50 mV at pH 7. 9). The electron-sharing equilibria among thioredoxin f and its target enzymes largely explained the differential effects of photooxidation induced at low temperature on thioredoxin-mediated activation of chloroplast enzymes in tomato. These results not only provide a plausible mechanism for the low-temperature-induced inhibition of photosynthesis in this important group of plants, but also provide a quantitative basis to evaluate the influence of thioredoxin/target enzyme electron-sharing equilibria on the differential activation and deactivation kinetics of thioredoxin-regulated chloroplast enzymes.
Collapse
Affiliation(s)
- R S Hutchison
- Photosynthesis Research Unit, USDA/ARS, and Department of Plant Biology, University of Illinois, Urbana, Illinois 61801-3838, USA
| | | | | |
Collapse
|
50
|
Richter ML, Hein R, Huchzermeyer B. Important subunit interactions in the chloroplast ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1458:326-42. [PMID: 10838048 DOI: 10.1016/s0005-2728(00)00084-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
General structural features of the chloroplast ATP synthase are summarized highlighting differences between the chloroplast enzyme and other ATP synthases. Much of the review is focused on the important interactions between the epsilon and gamma subunits of the chloroplast coupling factor 1 (CF(1)) which are involved in regulating the ATP hydrolytic activity of the enzyme and also in transferring energy from the membrane segment, chloroplast coupling factor 0 (CF(0)), to the catalytic sites on CF(1). A simple model is presented which summarizes properties of three known states of activation of the membrane-bound form of CF(1). The three states can be explained in terms of three different bound conformational states of the epsilon subunit. One of the three states, the fully active state, is only found in the membrane-bound form of CF(1). The lack of this state in the isolated form of CF(1), together with the confirmed presence of permanent asymmetry among the alpha, beta and gamma subunits of isolated CF(1), indicate that ATP hydrolysis by isolated CF(1) may involve only two of the three potential catalytic sites on the enzyme. Thus isolated CF(1) may be different from other F(1) enzymes in that it only operates on 'two cylinders' whereby the gamma subunit does not rotate through a full 360 degrees during the catalytic cycle. On the membrane in the presence of a light-induced proton gradient the enzyme assumes a conformation which may involve all three catalytic sites and a full 360 degrees rotation of gamma during catalysis.
Collapse
Affiliation(s)
- M L Richter
- Department of Molecular Biosciences, The University of Kansas, Lawrence 66045, USA
| | | | | |
Collapse
|