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Journal of Bioenergetics and... Feb 1994Plastocyanin is one of the best characterized of the photosynthetic electron transfer proteins. Since the determination of the structure of poplar plastocyanin in 1978,... (Review)
Review
Plastocyanin is one of the best characterized of the photosynthetic electron transfer proteins. Since the determination of the structure of poplar plastocyanin in 1978, the structure of algal (Scenedesmus, Enteromorpha, Chlamydomonas) and plant (French bean) plastocyanins has been determined either by crystallographic or NMR methods, and the poplar structure has been refined to 1.33 A resolution. Despite the sequence divergence among plastocyanins of algae and vascular plants (e.g., 62% sequence identity between the Chlamydomonas and poplar proteins), the three-dimensional structures are remarkably conserved (e.g., 0.76 A rms deviation in the C alpha positions between the Chlamydomonas and poplar proteins). Structural features include a distorted tetrahedral copper binding site at one end of an eight-stranded antiparallel beta-barrel, a pronounced negative patch, and a flat hydrophobic surface. The copper site is optimized for its electron transfer function, and the negative and hydrophobic patches are proposed to be involved in recognition of physiological reaction partners. Chemical modification, cross-linking, and site-directed mutagenesis experiments have confirmed the importance of the negative and hydrophobic patches in binding interactions with cytochrome f and Photosystem I, and validated the model of two functionally significant electron transfer paths in plastocyanin. One putative electron transfer path is relatively short (approximately 4 A) and involves the solvent-exposed copper ligand His-87 in the hydrophobic patch, while the other is more lengthy (approximately 12-15 A) and involves the nearly conserved residue Tyr-83 in the negative patch.
Topics: Amino Acid Sequence; Molecular Sequence Data; Plastocyanin; Protein Conformation; Sequence Homology, Amino Acid; Structure-Activity Relationship
PubMed: 8027022
DOI: 10.1007/BF00763219 -
Proceedings of the National Academy of... Jun 2020In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by...
In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by macromolecular crowding. For thylakoid membranes of higher plants, a long-standing question has been which of the two mobile electron carriers, plastoquinone or plastocyanin, mediates electron transport from stacked grana thylakoids where photosystem II (PSII) is localized to distant unstacked regions of the thylakoids that harbor PSI. Here, we confirm that plastocyanin is the long-range electron carrier by employing mutants with different grana diameters. Furthermore, our results explain why higher plants have a narrow range of grana diameters since a larger diffusion distance for plastocyanin would jeopardize the efficiency of electron transport. In the light of recent findings that the lumen of thylakoids, which forms the diffusion space of plastocyanin, undergoes dynamic swelling/shrinkage, this study demonstrates that plastocyanin diffusion is a crucial regulatory element of plant photosynthetic electron transport.
Topics: Computer Simulation; Electron Transport; Gene Expression Regulation, Plant; Magnoliopsida; Models, Biological; Photosystem I Protein Complex; Photosystem II Protein Complex; Plastocyanin
PubMed: 32541018
DOI: 10.1073/pnas.2005832117 -
The Biochemical Journal Jun 2021Photosystem I is defined as plastocyanin-ferredoxin oxidoreductase. Taking advantage of genetic engineering, kinetic analyses and cryo-EM, our data provide novel...
Photosystem I is defined as plastocyanin-ferredoxin oxidoreductase. Taking advantage of genetic engineering, kinetic analyses and cryo-EM, our data provide novel mechanistic insights into binding and electron transfer between PSI and Pc. Structural data at 2.74 Å resolution reveals strong hydrophobic interactions in the plant PSI-Pc ternary complex, leading to exclusion of water molecules from PsaA-PsaB/Pc interface once the PSI-Pc complex forms. Upon oxidation of Pc, a slight tilt of bound oxidized Pc allows water molecules to accommodate the space between Pc and PSI to drive Pc dissociation. Such a scenario is consistent with the six times larger dissociation constant of oxidized as compared with reduced Pc and mechanistically explains how this molecular machine optimized electron transfer for fast turnover.
Topics: Binding Sites; Chlamydomonas reinhardtii; Electron Transport; Hydrophobic and Hydrophilic Interactions; Kinetics; Models, Molecular; Oxidation-Reduction; Photosystem I Protein Complex; Plastocyanin; Protein Binding; Protein Conformation
PubMed: 34085703
DOI: 10.1042/BCJ20210267 -
Expression of the plastocyanin gene PETE2 in Camelina sativa improves seed yield and salt tolerance.Journal of Plant Physiology Nov 2023Plastocyanin functions as an electron carrier in the photosynthetic electron transport chain, located at the thylakoid membrane. In several species, endogenous...
Plastocyanin functions as an electron carrier in the photosynthetic electron transport chain, located at the thylakoid membrane. In several species, endogenous plastocyanin levels are correlated with the photosynthetic electron transport rate. Overexpression of plastocyanin genes in Arabidopsis thaliana increases plant size, but this phenomenon has not been observed in crop species. Here, we investigated the effects of heterologous expression of a gene encoding a plastocyanin isoform from Arabidopsis, AtPETE2, in the oil seed crop Camelina sativa under standard growth conditions and under salt stress. AtPETE2 heterologous expression enhanced photosynthetic activity in Camelina, accelerating plant development and improving seed yield under standard growth conditions. Additionally, CsPETE2 from Camelina was induced by salt stress and AtPETE2 expression lines had larger primary roots and more lateral roots than the wild type. AtPETE2 expression lines also had larger seeds and higher total seed yield under long-term salt stress compared with non-transgenic Camelina. Our results demonstrate that increased plastocyanin levels in Camelina can enhance photosynthesis and productivity, as well as tolerance to osmotic and salt stresses. Heterologous expression of plastocyanin may be a useful strategy to mitigate crop stress in saline soils.
Topics: Plastocyanin; Salt Tolerance; Brassicaceae; Arabidopsis; Seeds
PubMed: 37788546
DOI: 10.1016/j.jplph.2023.154103 -
Biochemistry Oct 1989Spinach plastocyanin and turnip cytochrome f have been covalently linked by using a water-soluble carbodiimide to yield an adduct of the two proteins. The redox...
Spinach plastocyanin and turnip cytochrome f have been covalently linked by using a water-soluble carbodiimide to yield an adduct of the two proteins. The redox potential of cytochrome f in the adduct was shifted by -20 mV relative to that of free cytochrome f, while the redox potential of plastocyanin in the adduct was the same as that of free plastocyanin. Solvent perturbation studies showed the degree of heme exposure in the adduct to be less than in free cytochrome f, indicating that plastocyanin was linked in such a way as to bury the exposed heme edge. Small changes were also observed when the resonance Raman spectrum of the adduct was compared to that of free cytochrome f. The adduct was incapable of interacting with or donating electrons to photosystem I. Peptide mapping and sequencing studies revealed two sites of linkage between the two proteins. In one site of linkage, Asp-44 of plastocyanin is covalently linked to Lys-187 of cytochrome f. This represents the first identification of a group on cytochrome f that is involved in the interaction with plastocyanin. The other site of linkage involves Glu-59 and/or Glu-60 of plastocyanin to as yet unidentified amino groups on cytochrome f. Euglena cytochrome c-552 could also be covalently linked to turnip cytochrome f, although with a lower efficiency than spinach plastocyanin. In contrast, a variety of cyanobacterial cytochrome c-553's and a cyanobacterial plastocyanin could not be covalently linked to turnip cytochrome f.
Topics: Amino Acid Sequence; Chromatography, High Pressure Liquid; Cyanogen Bromide; Cytochromes; Cytochromes f; Electron Transport; Electrophoresis, Polyacrylamide Gel; Heme; Molecular Sequence Data; Molecular Weight; Oxidation-Reduction; Oxygen Consumption; Photosynthesis; Plant Proteins; Plants; Plastocyanin; Spectrophotometry, Ultraviolet; Spectrum Analysis, Raman
PubMed: 2605172
DOI: 10.1021/bi00446a011 -
Nucleic Acids Research Aug 1989
Topics: Amino Acid Sequence; Base Sequence; Molecular Sequence Data; Plant Proteins; Plants; Plastocyanin; Protein Precursors
PubMed: 2771658
DOI: 10.1093/nar/17.15.6414 -
FEBS Letters Mar 2012Transient complexes, with a lifetime ranging between microseconds and seconds, are essential for biochemical reactions requiring a fast turnover. That is the case of the... (Review)
Review
Transient complexes, with a lifetime ranging between microseconds and seconds, are essential for biochemical reactions requiring a fast turnover. That is the case of the interactions between proteins engaged in electron transfer reactions, which are involved in relevant physiological processes such as respiration and photosynthesis. In the latter, the copper protein plastocyanin acts as a soluble carrier transferring electrons between the two membrane-embedded complexes cytochrome b(6)f and photosystem I. Here we review the combination of experimental efforts in the literature to unveil the functional and structural features of the complex between cytochrome f and plastocyanin, which have widely been used as a suitable model for analyzing transient redox interactions.
Topics: Bacterial Proteins; Cytochromes f; Electron Transport; Kinetics; Models, Molecular; Multiprotein Complexes; Plastocyanin; Protein Binding; Protein Conformation; Protein Structure, Tertiary
PubMed: 21889503
DOI: 10.1016/j.febslet.2011.08.035 -
Journal of Biomolecular Structure &... Mar 2022In the light reaction of oxygenic photosynthesis, plastocyanin (PC) and ferredoxins (Fd) are small/diffusible redox-active proteins playing key roles in electron...
In the light reaction of oxygenic photosynthesis, plastocyanin (PC) and ferredoxins (Fd) are small/diffusible redox-active proteins playing key roles in electron transfer/transport phenomena. In the Z-scheme mechanistic purview, they are considered as specific affinity binding-based electron-relay agents, linking the functions of Cytochrome (Cyt. ), Photosystem I (PS I) and Fd:NADPH oxidoreductase (FNR). The murburn explanation for photolytic photophosphorylation deems PC/Fd as generic 'redox capacitors', temporally accepting and releasing one-electron equivalents in reaction milieu. Herein, we explore the two theories with respect to structural, distributional and functional aspects of PC/Fd. Amino acid residues located on the surface loci of key patches of PC/Fd vary in electrostatic/contour (topography) signatures. Crystal structures of four different complexes each of Cyt.-PC and Fd-FNR show little conservation in the contact-surfaces, thereby discrediting 'affinity binding-based electron transfers (ET)' as an evolutionary logic. Further, thermodynamic and kinetic data of wildtype and mutant proteins interactions do not align with Z-scheme. Furthermore, micromolar physiological concentrations of PC and the non-conducive architecture of chloroplasts render the classical model untenable. In the murburn model, as PC is optional, the observation that plants lacking PC survive and grow is justified. Further, the low physiological concentration/distribution of PC in chloroplast lumen/stroma is supported by murburn equilibriums, as higher concentrations would limit electron transfers. Thus, structural evidence, interactive dynamics with redox partners and physiological distribution/role of PC/Fd support the murburn perspective that these proteins serve as generic redox-capacitors in chloroplasts.Communicated by Ramaswamy H. Sarma.
Topics: Electron Transport; Electrons; Ferredoxins; Oxidation-Reduction; Photosynthesis; Plastocyanin
PubMed: 33073701
DOI: 10.1080/07391102.2020.1835715 -
The Journal of Biological Chemistry Aug 2003Plastocyanin is a soluble copper-containing protein present in the thylakoid lumen, which transfers electrons to photosystem I. In the chloroplast of the flowering plant...
Plastocyanin is a soluble copper-containing protein present in the thylakoid lumen, which transfers electrons to photosystem I. In the chloroplast of the flowering plant Arabidopsis thaliana, a cytochrome c6-like protein is present, which was recently suggested to function as an alternative electron carrier to plastocyanin. We show that Arabidopsis plants mutated in both of the two plastocyanin-coding genes and with a functional cytochrome c6 cannot grow photoautotrophically because of a complete block in light-driven electron transport. Even increased dosage of the gene encoding the cytochrome c6-like protein cannot complement the double mutant phenotype. This demonstrates that in Arabidopsis only plastocyanin can donate electrons to photosystem I in vivo.
Topics: Arabidopsis; Base Sequence; DNA Transposable Elements; Electron Transport; Mutagenesis; Photosynthesis; Photosynthetic Reaction Center Complex Proteins; Photosystem I Protein Complex; Phylogeny; Plastocyanin
PubMed: 12773541
DOI: 10.1074/jbc.M302876200 -
Journal of Computational Chemistry Jun 2017Plastocyanin is a copper containing protein that is involved in the electron transfer process in photosynthetic organisms. The active site of plastocyanin is described...
Plastocyanin is a copper containing protein that is involved in the electron transfer process in photosynthetic organisms. The active site of plastocyanin is described as an entatic state whereby its structure represents a compromise between the structures favored by the oxidized and reduced forms. In this study, the nature of the entatic state is investigated through density functional theory-based hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations. The strain energy is computed to be 12.8 kcal/mol and 14.5 kcal/mol for the oxidized and reduced forms of the protein, indicating that the active site has an intermediate structure. It is shown that the energy gap between the oxidized and reduced forms varies significantly with the fluctuations in the structure of the active site at room temperature. An accurate determination of the reorganization energy requires averaging over conformation and a large region of the protein around the active site to be treated at the quantum mechanical level. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
Topics: Catalytic Domain; Electron Transport; Molecular Dynamics Simulation; Oxidation-Reduction; Plastocyanin; Protein Conformation; Quantum Theory; Thermodynamics
PubMed: 27859435
DOI: 10.1002/jcc.24666