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He Y, Wang Y, Li X, Guo Y, Ma L. Breaking the bottleneck of organic light conversion agents: Preparation, performance evaluation and intrinsic mechanism. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 288:122161. [PMID: 36455463 DOI: 10.1016/j.saa.2022.122161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/20/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Poor photostability has become a major obstacle of organic fluorescent dyes (OFD) used as light conversion agent. To explore the intrinsic mechanisms of photodegradation and highly efficient means to enhance photostability, here, three s-triazine dyes and two 1,3,5-triphenylbenzene luminescent agents were designed and synthesized. Further, the relationships of photostability, intramolecular charge transfer effect, energy gap between singlet and triplet, and active oxygen generating capacity are analyzed and discussed. AIE activity, solid-state fluorescence emission, light conversion quality, and photostability combined with thermostability show TPT-DB (2,4,6-tris(4-(3,6-ditertbutyl-9H-carbazol-9-yl)phenyl)-1,3,5-triazine) is the best light conversion agent among of the dyes, whose photosynthetic photon flux density at 400-500 nm and 600-700 nm in doping film increased successively to 6.20% and 25.78% of the blank film, emission intensity can maintain 93.4% of the initial value after intensified UV radiation of 20 h (365 nm, 40 w), and has good thermal stability, Td up to 374 °C. Furthermore, oxygen-free environment was confirmed to be the most effective measure to enhance the photostability of OFD, thereby a simple and efficient method is adopted to block the diffusion of oxygen and significantly enhance the photostability of OFD by amphiphilic ethylene-vinyl alcohol copolymer. The work not only provides an excellent light conversion agent, but also clears the obstacles for the large-scale application of OFD as light conversion agents.
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Affiliation(s)
- Yanjin He
- Guangxi Key Laboratory of Electrochemical and Magneto-chemical Function Materia, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China
| | - Yongtao Wang
- Guangxi Key Laboratory of Electrochemical and Magneto-chemical Function Materia, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China.
| | - Xueming Li
- Guangxi Key Laboratory of Electrochemical and Magneto-chemical Function Materia, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China.
| | - Yanjun Guo
- Guangxi Key Laboratory of Electrochemical and Magneto-chemical Function Materia, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China.
| | - Lei Ma
- Tianjin International Center for Nanoparticles and Nanosystem, Tianjin University, Tianjin 300072, PR China
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Adams NBP, Bisson C, Brindley AA, Farmer DA, Davison PA, Reid JD, Hunter CN. The active site of magnesium chelatase. NATURE PLANTS 2020; 6:1491-1502. [PMID: 33257858 DOI: 10.1038/s41477-020-00806-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 10/14/2020] [Indexed: 06/12/2023]
Abstract
The insertion of magnesium into protoporphyrin initiates the biosynthesis of chlorophyll, the pigment that underpins photosynthesis. This reaction, catalysed by the magnesium chelatase complex, couples ATP hydrolysis by a ChlID motor complex to chelation within the ChlH subunit. We probed the structure and catalytic function of ChlH using a combination of X-ray crystallography, computational modelling, mutagenesis and enzymology. Two linked domains of ChlH in an initially open conformation of ChlH bind protoporphyrin IX, and the rearrangement of several loops envelops this substrate, forming an active site cavity. This induced fit brings an essential glutamate (E660), proposed to be the key catalytic residue for magnesium insertion, into proximity with the porphyrin. A buried solvent channel adjacent to E660 connects the exterior bulk solvent to the active site, forming a possible conduit for the delivery of magnesium or abstraction of protons.
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Affiliation(s)
- Nathan B P Adams
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK.
| | - Claudine Bisson
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
- Centre for Ultrastructural Imaging, New Hunt's House, Guy's Campus, King's College London, London, UK
| | - Amanda A Brindley
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - David A Farmer
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - Paul A Davison
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - James D Reid
- Department of Chemistry, The University of Sheffield, Sheffield, UK
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK.
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Chen HM, Wang YM, Yang HL, Zeng QY, Liu YJ. NRAMP1 promotes iron uptake at the late stage of iron deficiency in poplars. TREE PHYSIOLOGY 2019; 39:1235-1250. [PMID: 31115467 DOI: 10.1093/treephys/tpz055] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 02/15/2019] [Accepted: 05/10/2019] [Indexed: 05/26/2023]
Abstract
Iron (Fe) is an essential micronutrient for plant survival and proliferation. Plants have evolved complex mechanisms to maintain Fe homeostasis in response to Fe deficiency. In this study, we evaluated the physiological, biochemical and transcriptomic differences between poplars grown under Fe-sufficient and Fe-deficient conditions to elucidate the mechanistic responses of poplars to Fe deficiency. Our results revealed that chlorophyll synthesis and photosynthesis were inhibited under Fe-deficient conditions. The inhibition of these pathways caused chlorosis and reduced shoot growth. Although both photosynthetic systems (PSI and PSII) were inhibited under Fe limitation, PSI was affected more severely and earlier than PSII. Fe deficiency also promoted root growth and increased the accumulation of divalent metal ions in roots. IRT1 and NRAMP1 are both Fe2+ transporters for iron uptake in Arabidopsis. In this study, however, only NRAMP1 was induced to promote Fe2+ uptake in roots at the late stage of Fe deficiency response. It indicated that NRAMP1, rather than the more well-known IRT1, might be a major Fe2+ transporter at the late stage of Fe-deficiency in poplars.
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Affiliation(s)
- Hui-Min Chen
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing 100091, China
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi-Ming Wang
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China
| | - Hai-Ling Yang
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China
| | - Qing-Yin Zeng
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing 100091, China
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan-Jing Liu
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing 100091, China
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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The ChlD subunit links the motor and porphyrin binding subunits of magnesium chelatase. Biochem J 2019; 476:1875-1887. [PMID: 31164400 PMCID: PMC6604950 DOI: 10.1042/bcj20190095] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/22/2019] [Accepted: 06/04/2019] [Indexed: 11/26/2022]
Abstract
Magnesium chelatase initiates chlorophyll biosynthesis, catalysing the MgATP2−-dependent insertion of a Mg2+ ion into protoporphyrin IX. The catalytic core of this large enzyme complex consists of three subunits: Bch/ChlI, Bch/ChlD and Bch/ChlH (in bacteriochlorophyll and chlorophyll producing species, respectively). The D and I subunits are members of the AAA+ (ATPases associated with various cellular activities) superfamily of enzymes, and they form a complex that binds to H, the site of metal ion insertion. In order to investigate the physical coupling between ChlID and ChlH in vivo and in vitro, ChlD was FLAG-tagged in the cyanobacterium Synechocystis sp. PCC 6803 and co-immunoprecipitation experiments showed interactions with both ChlI and ChlH. Co-production of recombinant ChlD and ChlH in Escherichia coli yielded a ChlDH complex. Quantitative analysis using microscale thermophoresis showed magnesium-dependent binding (Kd 331 ± 58 nM) between ChlD and H. The physical basis for a ChlD–H interaction was investigated using chemical cross-linking coupled with mass spectrometry (XL–MS), together with modifications that either truncate ChlD or modify single residues. We found that the C-terminal integrin I domain of ChlD governs association with ChlH, the Mg2+ dependence of which also mediates the cooperative response of the Synechocystis chelatase to magnesium. The interaction site between the AAA+ motor and the chelatase domain of magnesium chelatase will be essential for understanding how free energy from the hydrolysis of ATP on the AAA+ ChlI subunit is transmitted via the bridging subunit ChlD to the active site on ChlH.
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Adams NBP, Brindley AA, Hunter CN, Reid JD. The catalytic power of magnesium chelatase: a benchmark for the AAA(+) ATPases. FEBS Lett 2016; 590:1687-93. [PMID: 27176620 PMCID: PMC4982103 DOI: 10.1002/1873-3468.12214] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/06/2016] [Accepted: 05/09/2016] [Indexed: 11/11/2022]
Abstract
In the first committed reaction of chlorophyll biosynthesis, magnesium chelatase couples ATP hydrolysis to the thermodynamically unfavorable Mg(2+) insertion into protoporphyrin IX (ΔG°' of circa 25-33 kJ·mol(-1) ). We explored the thermodynamic constraints on magnesium chelatase and demonstrate the effect of nucleotide hydrolysis on both the reaction kinetics and thermodynamics. The enzyme produces a significant rate enhancement (kcat /kuncat of 400 × 10(6) m) and a catalytic rate enhancement, kcat/KmDIXK0.5Mgkuncat, of 30 × 10(15) m(-1) , increasing to 300 × 10(15) m(-1) with the activator protein Gun4. This is the first demonstration of the thermodynamic benefit of ATP hydrolysis in the AAA(+) family.
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Affiliation(s)
- Nathan B P Adams
- Department of Molecular Biology and Biotechnology, University of Sheffield, UK
| | - Amanda A Brindley
- Department of Molecular Biology and Biotechnology, University of Sheffield, UK
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, UK
| | - James D Reid
- Department of Chemistry, University of Sheffield, UK
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Adams NBP, Vasilev C, Brindley AA, Hunter CN. Nanomechanical and Thermophoretic Analyses of the Nucleotide-Dependent Interactions between the AAA(+) Subunits of Magnesium Chelatase. J Am Chem Soc 2016; 138:6591-7. [PMID: 27133226 PMCID: PMC4882731 DOI: 10.1021/jacs.6b02827] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In chlorophyll biosynthesis, the magnesium chelatase enzyme complex catalyzes the insertion of a Mg(2+) ion into protoporphyrin IX. Prior to this event, two of the three subunits, the AAA(+) proteins ChlI and ChlD, form a ChlID-MgATP complex. We used microscale thermophoresis to directly determine dissociation constants for the I-D subunits from Synechocystis, and to show that the formation of a ChlID-MgADP complex, mediated by the arginine finger and the sensor II domain on ChlD, is necessary for the assembly of the catalytically active ChlHID-MgATP complex. The N-terminal AAA(+) domain of ChlD is essential for complex formation, but some stability is preserved in the absence of the C-terminal integrin domain of ChlD, particularly if the intervening polyproline linker region is retained. Single molecule force spectroscopy (SMFS) was used to determine the factors that stabilize formation of the ChlID-MgADP complex at the single molecule level; ChlD was attached to an atomic force microscope (AFM) probe in two different orientations, and the ChlI subunits were tethered to a silica surface; the probability of subunits interacting more than doubled in the presence of MgADP, and we show that the N-terminal AAA(+) domain of ChlD mediates this process, in agreement with the microscale thermophoresis data. Analysis of the unbinding data revealed a most probable interaction force of around 109 pN for formation of single ChlID-MgADP complexes. These experiments provide a quantitative basis for understanding the assembly and function of the Mg chelatase complex.
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Affiliation(s)
- Nathan B P Adams
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, United Kingdom
| | - Cvetelin Vasilev
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, United Kingdom
| | - Amanda A Brindley
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, United Kingdom
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, United Kingdom
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Brindley AA, Adams NBP, Hunter CN, Reid JD. Five glutamic acid residues in the C-terminal domain of the ChlD subunit play a major role in conferring Mg(2+) cooperativity upon magnesium chelatase. Biochemistry 2015; 54:6659-62. [PMID: 26513685 DOI: 10.1021/acs.biochem.5b01080] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Magnesium chelatase catalyzes the first committed step in chlorophyll biosynthesis by inserting a Mg(2+) ion into protoporphyrin IX in an ATP-dependent manner. The cyanobacterial (Synechocystis) and higher-plant chelatases exhibit a complex cooperative response to free magnesium, while the chelatases from Thermosynechococcus elongatus and photosynthetic bacteria do not. To investigate the basis for this cooperativity, we constructed a series of chimeric ChlD proteins using N-terminal, central, and C-terminal domains from Synechocystis and Thermosynechococcus. We show that five glutamic acid residues in the C-terminal domain play a major role in this process.
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Affiliation(s)
- Amanda A Brindley
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, U.K
| | - Nathan B P Adams
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, U.K
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, The University of Sheffield , Sheffield S10 2TN, U.K
| | - James D Reid
- Department of Chemistry, The University of Sheffield , Sheffield S3 7HF, U.K
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Kopečná J, Cabeza de Vaca I, Adams NBP, Davison PA, Brindley AA, Hunter CN, Guallar V, Sobotka R. Porphyrin Binding to Gun4 Protein, Facilitated by a Flexible Loop, Controls Metabolite Flow through the Chlorophyll Biosynthetic Pathway. J Biol Chem 2015; 290:28477-28488. [PMID: 26446792 DOI: 10.1074/jbc.m115.664987] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Indexed: 01/01/2023] Open
Abstract
In oxygenic phototrophs, chlorophylls, hemes, and bilins are synthesized by a common branched pathway. Given the phototoxic nature of tetrapyrroles, this pathway must be tightly regulated, and an important regulatory role is attributed to magnesium chelatase enzyme at the branching between the heme and chlorophyll pathway. Gun4 is a porphyrin-binding protein known to stimulate in vitro the magnesium chelatase activity, but how the Gun4-porphyrin complex acts in the cell was unknown. To address this issue, we first performed simulations to determine the porphyrin-docking mechanism to the cyanobacterial Gun4 structure. After correcting crystallographic loop contacts, we determined the binding site for magnesium protoporphyrin IX. Molecular modeling revealed that the orientation of α6/α7 loop is critical for the binding, and the magnesium ion held within the porphyrin is coordinated by Asn-211 residue. We also identified the basis for stronger binding in the Gun4-1 variant and for weaker binding in the W192A mutant. The W192A-Gun4 was further characterized in magnesium chelatase assay showing that tight porphyrin binding in Gun4 facilitates its interaction with the magnesium chelatase ChlH subunit. Finally, we introduced the W192A mutation into cells and show that the Gun4-porphyrin complex is important for the accumulation of ChlH and for channeling metabolites into the chlorophyll biosynthetic pathway.
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Affiliation(s)
- Jana Kopečná
- Institute of Microbiology, Academy of Sciences, 37981 Třeboň, Czech Republic
| | - Israel Cabeza de Vaca
- Joint Barcelona Supercomputing Center-Centre for Genomic Regulation-Institute for Research in Biomedicine Research Program, Carrer de Jordi Girona 29, 08034 Barcelona, Spain
| | - Nathan B P Adams
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Paul A Davison
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Amanda A Brindley
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Victor Guallar
- Joint Barcelona Supercomputing Center-Centre for Genomic Regulation-Institute for Research in Biomedicine Research Program, Carrer de Jordi Girona 29, 08034 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
| | - Roman Sobotka
- Institute of Microbiology, Academy of Sciences, 37981 Třeboň, Czech Republic; Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic.
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Structural and functional consequences of removing the N-terminal domain from the magnesium chelatase ChlH subunit of Thermosynechococcus elongatus. Biochem J 2015; 464:315-22. [PMID: 25471602 PMCID: PMC4255732 DOI: 10.1042/bj20140463] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnesium chelatase (MgCH) initiates chlorophyll biosynthesis by catalysing the ATP-dependent insertion of Mg2+ into protoporphyrin. This large enzyme complex comprises ChlH, I and D subunits, with I and D involved in ATP hydrolysis, and H the protein that handles the substrate and product. The 148 kDa ChlH subunit has a globular N-terminal domain attached by a narrow linker to a hollow cage-like structure. Following deletion of this ~18 kDa domain from the Thermosynechoccus elongatus ChlH, we used single particle reconstruction to show that the apo- and porphyrin-bound forms of the mutant subunit consist of a hollow globular protein with three connected lobes; superposition of the mutant and native ChlH structures shows that, despite the clear absence of the N-terminal ‘head’ region, the rest of the protein appears to be correctly folded. Analyses of dissociation constants shows that the ΔN159ChlH mutant retains the ability to bind protoporphyrin and the Gun4 enhancer protein, although the addition of I and D subunits yields an extremely impaired active enzyme complex. Addition of the Gun4 enhancer protein, which stimulates MgCH activity significantly especially at low Mg2+ concentrations, partially reactivates the ΔN159ChlH–I–D mutant enzyme complex, suggesting that the binding site or sites for Gun4 on H do not wholly depend on the N-terminal domain. The N-terminal domain of the 148 kDa ChlH is essential for normal activity of the ChlH–I–D magnesium chelatase complex. Deleting this 18 kDa domain retains the hollow cage-like structure and porphyrin binding. Chelatase activity is partially restored by the Gun4 protein.
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