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Plant Signaling & Behavior 2015Plastocyanin is a copper (Cu)-requiring protein that functions in photosynthetic electron transport in the thylakoid lumen of plants. To allow plastocyanin maturation,...
Plastocyanin is a copper (Cu)-requiring protein that functions in photosynthetic electron transport in the thylakoid lumen of plants. To allow plastocyanin maturation, Cu must first be transported into the chloroplast stroma by means of the PAA1/HMA6 transporter and then into the thylakoid lumen by the PAA2/HMA8 transporter. Recent evidence indicated that the chloroplast regulates Cu transport into the thylakoids via Clp protease-mediated turnover of PAA2/HMA8. Here we present further genetic evidence that this regulatory mechanism for the adjustment of intra-cellular Cu distribution depends on stromal Cu levels. A key transcription factor mediating Cu homeostasis in plants is SQUAMOSA promoter binding protein-like7 (SPL7). SPL7 transcriptionally regulates Cu homeostasis when the nutrient becomes limiting by up-regulating expression of Cu importers at the cell membrane, and down-regulating expression of seemingly non-essential cuproproteins. It was proposed that this latter mechanism favors Cu delivery to the chloroplast. We propose a 2-tiered system which functions to control plant leaf Cu homeostasis: SPL7 dependent transcriptional regulation of cuproproteins, and PAA2/HMA8 turnover by the Clp system, which is independent on SPL7.
Topics: Adenosine Triphosphatases; Arabidopsis; Arabidopsis Proteins; Biological Transport; Chloroplast Proteins; Copper; Evolution, Molecular; Homeostasis; Models, Biological; Molecular Chaperones
PubMed: 26251885
DOI: 10.1080/15592324.2015.1046666 -
Biophysical Journal Mar 2005Using Brownian dynamics simulations, all of the charged residues in Chlamydomonas reinhardtii cytochrome c(6) (cyt c(6)) and plastocyanin (PC) were mutated to alanine...
Using Brownian dynamics simulations, all of the charged residues in Chlamydomonas reinhardtii cytochrome c(6) (cyt c(6)) and plastocyanin (PC) were mutated to alanine and their interactions with cytochrome f (cyt f) were modeled. Systematic mutation of charged residues on both PC and cyt c(6) confirmed that electrostatic interactions (at least in vitro) play an important role in bringing these proteins sufficiently close to cyt f to allow hydrophobic and van der Waals interactions to form the final electron transfer-active complex. The charged residue mutants on PC and cyt c(6) displayed similar inhibition classes. Our results indicate a difference between the two acidic clusters on PC. Mutations D44A and E43A of the lower cluster showed greater inhibition than do any of the mutations of the upper cluster residues. Replacement of acidic residues on cyt c(6) that correspond to the PC's lower cluster, particularly E70 and E69, was observed to be more inhibitory than those corresponding to the upper cluster. In PC residues D42, E43, D44, D53, D59, D61, and E85, and in cyt c(6) residues D2, E54, K57, D65, R66, E70, E71, and the heme had significant electrostatic contacts with cyt f charged residues. PC and cyt c(6) showed different binding sites and orientations on cyt f. As there are no experimental cyt c(6) mutation data available for algae, our results could serve as a good guide for future experimental work on this protein. The comparison between computational values and the available experimental data (for PC-cyt f interactions) showed overall good agreement, which supports the predictive power of Brownian dynamics simulations in mutagenesis studies.
Topics: Amino Acid Substitution; Animals; Binding Sites; Chlamydomonas reinhardtii; Computer Simulation; Cytochromes c6; Cytochromes f; Diffusion; Kinetics; Models, Chemical; Models, Molecular; Mutagenesis, Site-Directed; Plastocyanin; Protein Binding; Recombinant Proteins; Static Electricity
PubMed: 15626695
DOI: 10.1529/biophysj.104.053561 -
The Journal of Biological Chemistry May 2005The complex between cytochrome f and plastocyanin from the cyanobacterium Nostoc has been characterized by NMR spectroscopy. The binding constant is 16 mM(-1), and the...
Structure of the complex between plastocyanin and cytochrome f from the cyanobacterium Nostoc sp. PCC 7119 as determined by paramagnetic NMR. The balance between electrostatic and hydrophobic interactions within the transient complex determines the relative orientation of the two proteins.
The complex between cytochrome f and plastocyanin from the cyanobacterium Nostoc has been characterized by NMR spectroscopy. The binding constant is 16 mM(-1), and the lifetime of the complex is much less than 10 ms. Intermolecular pseudo-contact shifts observed for the plastocyanin amide nuclei, caused by the heme iron, as well as the chemical-shift perturbation data were used as the sole experimental restraints to determine the orientation of plastocyanin relative to cytochrome f with a precision of 1.3 angstroms. The data show that the hydrophobic patch surrounding tyrosine 1 in cytochrome f docks the hydrophobic patch of plastocyanin. Charge complementarities are found between the rims of the respective recognition sites of cytochrome f and plastocyanin. Significant differences in the relative orientation of both proteins are found between this complex and those previously reported for plants and Phormidium, indicating that electrostatic and hydrophobic interactions are balanced differently in these complexes.
Topics: Animals; Cytochromes f; Electrons; Heme; Kinetics; Magnetic Resonance Spectroscopy; Models, Molecular; Nostoc; Plasmodium; Plastocyanin; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Software; Static Electricity; Tyrosine
PubMed: 15705583
DOI: 10.1074/jbc.M413298200 -
Proceedings of the National Academy of... Oct 2019In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic...
In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic membranes, is widely used to quantify the activity of the photosynthetic chain. In cyanobacteria, ECS signals have never been used for physiological studies, although they can provide a unique tool to study the architecture and function of the respiratory and photosynthetic electron transfer chains, entangled in the thylakoid membranes. Here, we identified bona fide ECS signals, likely corresponding to carotenoid band shifts, in the model cyanobacteria PCC7942 and PCC6803. These band shifts, most likely originating from pigments located in photosystem I, have highly similar spectra in the 2 species and can be best measured as the difference between the absorption changes at 500 to 505 nm and the ones at 480 to 485 nm. These signals respond linearly to the electric field and display the basic kinetic features of ECS as characterized in other organisms. We demonstrate that these probes are an ideal tool to study photosynthetic physiology in vivo, e.g., the fraction of PSI centers that are prebound by plastocyanin/cytochrome in darkness (about 60% in both cyanobacteria, in our experiments), the conductivity of the thylakoid membrane (largely reflecting the activity of the ATP synthase), or the steady-state rates of the photosynthetic electron transport pathways.
Topics: Electron Transport; Electrophysiology; Membrane Potentials; Photosynthesis; Photosystem I Protein Complex; Plastocyanin; Synechococcus; Thylakoids
PubMed: 31591197
DOI: 10.1073/pnas.1913099116 -
Proceedings of the National Academy of... Jan 2022Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via...
Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via forward genetics and functional assessment of senescence-associated genes (SAGs) via reverse genetics, the senescence signal and the molecular mechanism that perceives and transduces the signal remain elusive. Here, using dark-induced senescence (DIS) of leaf as the experimental system, we show that exogenous copper induces the senescence syndrome and transcriptomic changes in light-grown plants parallel to those in DIS. By profiling the transcriptomes and tracking the subcellular copper distribution, we found that reciprocal regulation of plastocyanin, the thylakoid lumen mobile electron carrier in the Z scheme of photosynthetic electron transport, and SAG14 and plantacyanin (PCY), a pair of interacting small blue copper proteins located on the endomembrane, is a common thread in different leaf senescence scenarios, including DIS. Genetic and molecular experiments confirmed that the PCY-SAG14 module is necessary and sufficient for promoting DIS. We also found that the PCY-SAG14 module is repressed by a conserved microRNA, miR408, which in turn is repressed by phytochrome interacting factor 3/4/5 (PIF3/4/5), the key trio of transcription factors promoting DIS. Together, these findings indicate that intracellular copper redistribution mediated by PCY-SAG14 has a regulatory role in DIS. Further deciphering the copper homeostasis mechanism and its interaction with other senescence-regulating pathways should provide insights into our understanding of the fundamental question of how plants age.
Topics: Arabidopsis; Arabidopsis Proteins; Copper; Darkness; Gene Expression Regulation, Plant; Light; MicroRNAs; Phytochrome; Plant Leaves; Plant Senescence; Plants, Genetically Modified; Transcription Factors; Transcriptome
PubMed: 35022242
DOI: 10.1073/pnas.2116623119 -
Plant Physiology Nov 2017Increasing grain yield is the most important object of crop breeding. Here, we report that the elevated expression of a conserved microRNA, OsmiR408, could positively...
Increasing grain yield is the most important object of crop breeding. Here, we report that the elevated expression of a conserved microRNA, OsmiR408, could positively regulate grain yield in rice () by increasing panicle branches and grain number. We further showed that OsmiR408 regulates grain yield by down-regulating its downstream target, , which is an uclacyanin (UCL) gene of the phytocyanin family. The knock down or knock out of also increases grain yield, while the overexpression of results in an opposite phenotype. Spatial and temporal expression analyses showed that was highly expressed in pistils, young panicles, developing seeds, and inflorescence meristem and was nearly complementary to that of OsmiR408. Interestingly, the OsUCL8 protein was localized to the cytoplasm, distinct from a majority of phytocyanins, which localize to the plasma membrane. Further studies revealed that the cleavage of by miR408 affects copper homeostasis in the plant cell, which, in turn, affects the abundance of plastocyanin proteins and photosynthesis in rice. To our knowledge, this is the first report of the effects of miR408- in regulating rice photosynthesis and grain yield. Our study further broadens the perspective of microRNAs and UCLs and provides important information for breeding high-yielding crops through genetic engineering.
Topics: Gene Expression Profiling; Gene Expression Regulation, Plant; MicroRNAs; Oryza; Phenotype; Photosynthesis; Plant Proteins; Plants, Genetically Modified; Plastocyanin; RNA Interference; Seeds
PubMed: 28904074
DOI: 10.1104/pp.17.01169 -
International Journal of Molecular... Mar 2009We briefly review our studies on the folding/unfolding mechanisms of proteins. In biological self-assembly processes such as protein folding, the number of accessible... (Review)
Review
We briefly review our studies on the folding/unfolding mechanisms of proteins. In biological self-assembly processes such as protein folding, the number of accessible translational configurations of water in the system increases greatly, leading to a large gain in the water entropy. The usual view looking at only the water in the close vicinity of the protein surface is capable of elucidating neither the large entropic gain upon apoplastocyanin folding, which has recently been found in a novel experimental study, nor the pressure and cold denaturation. With the emphasis on the translational entropy of water, we are presently constructing a reliable method for predicting the native structure of a protein from its amino-acid sequence.
Topics: Apoproteins; Entropy; Plastocyanin; Pressure; Protein Denaturation; Protein Folding; Temperature; Water
PubMed: 19399238
DOI: 10.3390/ijms10031064 -
The Journal of Biological Chemistry May 2004On the lumenal side of photosystem I (PSI), each of the two large core subunits, PsaA and PsaB, expose a conserved tryptophan residue to the surface. PsaB-Trp(627) is...
The hydrophobic recognition site formed by residues PsaA-Trp651 and PsaB-Trp627 of photosystem I in Chlamydomonas reinhardtii confers distinct selectivity for binding of plastocyanin and cytochrome c6.
On the lumenal side of photosystem I (PSI), each of the two large core subunits, PsaA and PsaB, expose a conserved tryptophan residue to the surface. PsaB-Trp(627) is part of the hydrophobic recognition site that is essential for tight binding of the two electron donors plastocyanin and cytochrome c(6) to the donor side of PSI (Sommer, F., Drepper, F., and Hippler, M. (2002) J. Biol. Chem. 277, 6573-6581). To examine the function of PsaA-Trp(651) in binding and electron transfer of both donors to PSI, we generated the mutants PsaA-W651F and PsaA-W651S by site-directed mutagenesis and biolistic transformation of Chlamydomonas reinhardtii. The protein-protein interaction and the electron transfer between the donors and PSI isolated from the mutants were analyzed by flash absorption spectroscopy. The mutation PsaA-W651F completely abolished the formation of a first order electron transfer complex between plastocyanin (pc) and the altered PSI and increased the dissociation constant for binding of cytochrome (cyt) c(6) by more than a factor of 10 as compared with wild type. Mutation of PsaA-Trp(651) to Ser had an even larger impact on the dissociation constant. The K(D) value increased another 2-fold when the values obtained for the interaction and electron transfer between cyt c(6) and PSI from PsaA-W651S and PsaA-W651F are compared. In contrast, binding and electron transfer of pc to PSI from PsaA-W651S improved as compared with PSI from PsaA-W651F and admitted the formation of an inter-molecular electron transfer complex, resulting in a K(D) value of about 554 microm that is still five times higher than observed for wild type. These results demonstrate that PsaA-Trp(651) is, such as PsaB-Trp(627), crucial for high affinity binding of pc and cyt c(6) to PSI. Our results also indicate that the highly conserved structural recognition motif that is formed by PsaA-Trp(651) and PsaB-Trp(627) confers a differential selectivity in binding of both donors to PSI.
Topics: Animals; Bacterial Proteins; Binding Sites; Chlamydomonas reinhardtii; Crystallography, X-Ray; Cytochromes c6; Electrons; Electrophoresis, Polyacrylamide Gel; Immunoblotting; Kinetics; Models, Molecular; Mutagenesis, Site-Directed; Mutation; Photosystem I Protein Complex; Plastocyanin; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Spectrophotometry; Thylakoids
PubMed: 14996834
DOI: 10.1074/jbc.M313986200 -
The Journal of Biological Chemistry Sep 1992In certain cyanobacteria and algae, cytochrome c553 or plastocyanin can serve to carry electrons from the cytochrome bf complex to photosystem I. The availability of...
In certain cyanobacteria and algae, cytochrome c553 or plastocyanin can serve to carry electrons from the cytochrome bf complex to photosystem I. The availability of copper in the growth medium regulates which protein is present. To investigate copper induced control of gene expression we isolated these proteins from the cyanobacterium Synechocystis 6803. Using immunodetection and optical spectroscopy, the steady state levels of cytochrome c553 and plastocyanin were measured in cells grown at different copper concentrations. The results show that in cells grown in 20-30 nM copper, cytochrome c553 was present, whereas plastocyanin was not detected. The opposite behavior was observed in cells grown in the presence of 1 microM copper; plastocyanin was present, whereas cytochrome c553 could not be detected. Both proteins were present in cells grown in 0.3 microM copper. Northern analysis of total RNA, probed with a gene fragment for cytochrome c553 or the plastocyanin gene, showed that cells grown in the presence of 20-30 nM copper have message for cytochrome c553, but not for plastocyanin, whereas cells grown in 1 microM copper have message for plastocyanin, but not for cytochrome c553. These results demonstrate that copper regulates expression of both of the genes encoding cytochrome c553 and plastocyanin prior to translation in Synechocystis 6803.
Topics: Copper; Cyanobacteria; Cytochrome c Group; Gene Expression Regulation; Light; Plastocyanin; RNA, Messenger
PubMed: 1326543
DOI: No ID Found -
Journal of Biochemistry Oct 1980The protein-protein electron transfer reactions between cytochrome f and plastocyanin, both purified from Brassica komatsuna (Brassica rapa L. var. pervirdis Bailey),...
The protein-protein electron transfer reactions between cytochrome f and plastocyanin, both purified from Brassica komatsuna (Brassica rapa L. var. pervirdis Bailey), have been studied as a function of pH, ionic strength, and temperature. The second-order rate constant for the oxidation of ferrocytochrome f by plastocyanin was found to be k = 4.5 X 10(7) M-1 x S-1 at pH 7.0 mu 0.2 M, and 20 degrees C, with activation parameters delta H not equal to = 8.4 kcal/mol and delta S not equal to = 4.9 cal/mol x deg. Respective rate constant and activation parameters obtained for the reduction of ferricytochrome f by plastocyanin were k = 1.9 X 10(7) M-1 x S-1, delta H not equal to = 8.6 kcal/mol, and delta S not equal to = 3.9 cal/mol x deg. The high rate constants for these reactions and delta S not equal to = 4.9 cal/mol x deg. Respective rate constant and activation parameters obtained for the reduction of ferricytochrome f by plastocyanin were k = 1.9 X 10(7) M-1 x S-1, delta H not equal to = 8.6 kcal/mol, and delta S not equal to = 3.9 cal/mol x deg. The high rate constants for these reactions are attributable not to a low activation enthalpy but to a positive activation entropy term. The rate constants both for the oxidation and the reduction of cytochrome f by plastocyanin drastically decreased with increasing ionic strength, indicating the importance of electrostatic interactions. Divalent cations are more effective than monovalent cations in reducing the rates of these reactions. The rate constants for the oxidation of cytochrome f by plastocyanin are constant between pH 6.0 and 9.0 but decrease markedly above pH 9.0 and below pH 6.0. In the case of the reduction of cytochrome f by plastocyanin, an optimum pH around 7.0 was obtained and a biphasic feature was observed at alkaline pH. The results are discussed in relation to photosynthetic electron transport systems.
Topics: Brassica; Calorimetry; Cytochromes; Cytochromes f; Electron Transport; Hydrogen-Ion Concentration; Kinetics; Osmolar Concentration; Plant Proteins; Plants; Plastocyanin
PubMed: 7451412
DOI: 10.1093/oxfordjournals.jbchem.a133072