-
Molecular Plant Mar 2009Two homologous plastocyanin isoforms are encoded by the genes PETE1 and PETE2 in the nuclear genome of Arabidopsis thaliana. The PETE2 transcript is expressed at...
Two homologous plastocyanin isoforms are encoded by the genes PETE1 and PETE2 in the nuclear genome of Arabidopsis thaliana. The PETE2 transcript is expressed at considerably higher levels and the PETE2 protein is the more abundant isoform. Null mutations in the PETE genes resulted in plants, designated pete1 and pete2, with decreased plastocyanin contents. However, despite reducing plastocyanin levels by over approximately 90%, a pete2 null mutation on its own affects rates of photosynthesis and growth only slightly, whereas pete1 knockout plants, with about 60-80% of the wild-type plastocyanin level, did not show any alteration. Hence, plastocyanin concentration is not limiting for photosynthetic electron flow under optimal growth conditions, perhaps implying other possible physiological roles for the protein. Indeed, plastocyanin has been proposed previously to cooperate with cytochrome c(6A) (Cyt c(6A)) in thylakoid redox reactions, but we find no evidence for a physical interaction between the two proteins, using interaction assays in yeast. We observed homodimerization of Cyt c(6A) in yeast interaction assays, but also Cyt c(6A) homodimers failed to interact with plastocyanin. Moreover, phenotypic analysis of atc6-1 pete1 and atc6-1 pete2 double mutants, each lacking Cyt c(6A) and one of the two plastocyanin-encoding genes, failed to reveal any genetic interaction. Overexpression of either PETE1 or PETE2 in the pete1 pete2 double knockout mutant background results in essentially wild-type photosynthetic performance, excluding the possibility that the two plastocyanin isoforms could have distinct functions in thylakoid electron flow.
Topics: Amino Acid Sequence; Arabidopsis; Electron Transport; Molecular Sequence Data; Mutation; Oxidation-Reduction; Photosynthesis; Plastocyanin; Protein Isoforms; Sequence Homology, Amino Acid; Thylakoids
PubMed: 19825610
DOI: 10.1093/mp/ssn041 -
Frontiers in Plant Science 2014The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity... (Review)
Review
The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity and light quality, and to changing metabolic demands for ATP and NADPH imposed by stresses and leaf aging. By changing photosynthetic complex stoichiometry, a long-term imbalance between the photosynthetic production of ATP and NADPH and their metabolic consumption is avoided, and cytotoxic side reactions are minimized. Otherwise, an excess capacity of the light reactions, relative to the demands of primary metabolism, could result in a disturbance of cellular redox homeostasis and an increased production of reactive oxygen species, leading to the destruction of the photosynthetic apparatus and the initiation of cell death programs. In this review, changes of the abundances of the different constituents of the photosynthetic apparatus in response to environmental conditions and during leaf ontogenesis are summarized. The contributions of the different photosynthetic complexes to photosynthetic flux control and the regulation of electron transport are discussed.
PubMed: 24860580
DOI: 10.3389/fpls.2014.00188 -
FEBS Letters Oct 2003The results of studies of charge transfer in cyanobacterial photosystem I (PS I) using the photoelectric method are reviewed. The electrogenicity in the PS I complex and... (Review)
Review
The results of studies of charge transfer in cyanobacterial photosystem I (PS I) using the photoelectric method are reviewed. The electrogenicity in the PS I complex and its interaction with natural donors (plastocyanin, cytochrome c(6)), natural acceptors (ferredoxin, flavodoxin), or artificial acceptors and donors (methyl viologen and other redox dyes) were studied. The operating dielectric constant values in the vicinity of the charge transfer carriers in situ were calculated. The profile of distribution of the dielectric constant along the PS I pigment-protein complex (from plastocyanin or cytochrome c(6) through the chlorophyll dimer P700 to the acceptor complex) was estimated, and possible mechanisms of correlation between the local dielectric constant and electron transfer rate constant were discussed.
Topics: Chlorophyll; Cyanobacteria; Electric Conductivity; Electrochemistry; Electron Transport; Light; Membrane Proteins; Photosynthetic Reaction Center Complex Proteins; Thermodynamics
PubMed: 14572628
DOI: 10.1016/s0014-5793(03)01032-9 -
Biomolecules Apr 2023Due to the similarity in the basic coordination behavior of their mono-charged cations, silver biochemistry is known to be linked to that of copper in biological...
Due to the similarity in the basic coordination behavior of their mono-charged cations, silver biochemistry is known to be linked to that of copper in biological systems. Still, Cu/ is an essential micronutrient in many organisms, while no known biological process requires silver. In human cells, copper regulation and trafficking is strictly controlled by complex systems including many cytosolic copper chaperones, whereas some bacteria exploit the so-called "blue copper" proteins. Therefore, evaluating the controlling factors of the competition between these two metal cations is of enormous interest. By employing the tools of computational chemistry, we aim to delineate the extent to which Ag might be able to compete with the endogenous copper in its Type I (T1Cu) proteins, and where and if, alternatively, it is handled uniquely. The effect of the surrounding media (dielectric constant) and the type, number, and composition of amino acid residues are taken into account when modelling the reactions in the present study. The obtained results clearly indicate the susceptibility of the T1Cu proteins to a silver attack due to the favorable composition and geometry of the metal-binding centers, along with the similarity between the Ag/Cu-containing structures. Furthermore, by exploring intriguing questions of both metals' coordination chemistry, an important background for understanding the metabolism and biotransformation of silver in organisms is provided.
Topics: Humans; Copper; Silver
PubMed: 37189429
DOI: 10.3390/biom13040681 -
Antioxidants (Basel, Switzerland) Oct 2023Recent phylogenetic studies have unveiled a novel class of ascorbate peroxidases called "ascorbate peroxidase-related" (APX-R). These enzymes, found in green...
Recent phylogenetic studies have unveiled a novel class of ascorbate peroxidases called "ascorbate peroxidase-related" (APX-R). These enzymes, found in green photosynthetic eukaryotes, lack the amino acids necessary for ascorbate binding. This study focuses on the sole APX-R from referred to as ascorbate peroxidase 2 (APX2). We used immunoblotting to locate APX2 within the chloroplasts and in silico analysis to identify key structural motifs, such as the twin-arginine transport (TAT) motif for lumen translocation and the metal-binding MxxM motif. We also successfully expressed recombinant APX2 in . Our in vitro results showed that the peroxidase activity of APX2 was detected with guaiacol but not with ascorbate as an electron donor. Furthermore, APX2 can bind both copper and heme, as evidenced by spectroscopic, and fluorescence experiments. These findings suggest a potential interaction between APX2 and plastocyanin, the primary copper-containing enzyme within the thylakoid lumen of the chloroplasts. Predictions from structural models and evidence from H-NMR experiments suggest a potential interaction between APX2 and plastocyanin, emphasizing the influence of APX2 on the copper-binding abilities of plastocyanin. In summary, our results propose a significant role for APX2 as a regulator in copper transfer to plastocyanin. This study sheds light on the unique properties of APX-R enzymes and their potential contributions to the complex processes of photosynthesis in green algae.
PubMed: 38001799
DOI: 10.3390/antiox12111946 -
Cellular and Molecular Life Sciences :... May 2004Computational techniques are becoming increasingly important in structural and functional biology, in particular as tools to aid the interpretation of experimental... (Review)
Review
Computational techniques are becoming increasingly important in structural and functional biology, in particular as tools to aid the interpretation of experimental results and the design of new systems. This review reports on recent studies employing a variety of computational approaches to unravel the microscopic details of the structure-function relationships in plastocyanin and other proteins belonging to the blue copper superfamily. Aspects covered include protein recognition, electron transfer and protein-solvent interaction properties of the blue copper protein family. The relevance of integrating diverse computational approaches to address the analysis of a complex protein system, such as a cupredoxin metalloprotein, is emphasized.
Topics: Algorithms; Azurin; Bacterial Proteins; Binding Sites; Carrier Proteins; Computational Biology; Copper; Electrons; Heme; Kinetics; Models, Molecular; Oxidation-Reduction; Plant Proteins; Plastocyanin; Protein Binding; Protein Structure, Secondary; Software; Structure-Activity Relationship
PubMed: 15141299
DOI: 10.1007/s00018-004-3181-5 -
Structure (London, England : 1993) Mar 1998The reduction of plastocyanin by cytochrome f is part of the chain of photosynthetic electron transfer reactions that links photosystems II and I. The reaction is rapid...
BACKGROUND
The reduction of plastocyanin by cytochrome f is part of the chain of photosynthetic electron transfer reactions that links photosystems II and I. The reaction is rapid and is influenced by charged residues on both proteins. Previously determined structures show that the plastocyanin copper and cytochrome f haem redox centres are some distance apart from the relevant charged sidechains, and until now it was unclear how a transient electrostatic complex can be formed that brings the redox centres sufficiently close for a rapid reaction.
RESULTS
A new approach was used to determine the structure of the transient complex between cytochrome f and plastocyanin. Diamagnetic chemical shift changes and intermolecular pseudocontact shifts in the NMR spectrum of plastocyanin were used as input in restrained rigid-body molecular dynamics calculations. An ensemble of ten structures was obtained, in which the root mean square deviation of the plastocyanin position relative to cytochrome f is 1.0 A. Electrostatic interaction is maintained at the same time as the hydrophobic side of plastocyanin makes close contact with the haem area, thus providing a short electron transfer pathway (Fe-Cu distance 10.9 A) via residues Tyr1 or Phe4 (cytochrome f) and the copper ligand His87 (plastocyanin).
CONCLUSIONS
The combined use of diamagnetic and paramagnetic chemical shift changes makes it possible to obtain detailed information about the structure of a transient complex of redox proteins. The structure suggests that the electrostatic interactions 'guide' the partners into a position that is optimal for electron transfer, and which may be stabilised by short-range interactions.
Topics: Binding Sites; Cytochromes; Cytochromes f; Electron Transport; Magnetic Resonance Spectroscopy; Models, Molecular; Plastocyanin; Protein Binding; Protein Conformation
PubMed: 9551554
DOI: 10.1016/s0969-2126(98)00035-5 -
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 -
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 -
FEBS Letters Nov 2003Photosystem I (PS I) is a large membrane protein complex that catalyzes the first step of solar conversion, the light-induced transmembrane electron transfer, and... (Review)
Review
Photosystem I (PS I) is a large membrane protein complex that catalyzes the first step of solar conversion, the light-induced transmembrane electron transfer, and generates reductants for CO2 assimilation. It consists of 12 different proteins and 127 cofactors that perform light capturing and electron transfer. The function of PS I includes inter-protein electron transfer between PS I and smaller soluble electron transfer proteins. The structure of PS I is discussed with respect to the potential docking sites for the soluble electron acceptors, ferredoxin/flavodoxin, at the stromal side and the soluble electron donors, cytochrome c6/plastocyanin, at the luminal side of the PS I complex. Furthermore, the potential interaction sites with the peripheral antenna proteins are discussed.
Topics: Binding Sites; Cytochromes c6; Electron Transport; Ferredoxins; Flavodoxin; Macromolecular Substances; Models, Molecular; Photosystem I Protein Complex; Plastocyanin; Solubility; Static Electricity
PubMed: 14630316
DOI: 10.1016/s0014-5793(03)01124-4