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1.
Jensen PE Haldrup A Zhang S Scheller HV 《The Journal of biological chemistry》2004,279(23):24212-24217
PSI-O is a subunit of photosystem I in eukaryotes. The function of PSI-O was characterized in Arabidopsis plants using RNA interference. Several transformants with the psaO-RNAi construct were generated, and a high proportion of the plants contained only very little or virtually no residual PSI-O. Plants lacking PSI-O have a 50% reduction in state transitions indicating a role for PSI-O in the balancing of excitation energy between the two photosystems. PSI-H and -L have been shown previously to be involved in state transitions, and immunoblot analysis revealed that plants devoid of PSI-L or -H also have 80-90% reduction in the abundance of PSI-O. In contrast, down-regulation of PSI-O has no negative effect on the content of PSI-H and -L. The interaction between PSI-O and the PSI-L was confirmed by chemical cross-linking. A model of PSI is proposed in which PSI-L as the most ancient subunit is closest to the reaction center, and PSI-O is positioned close to PSI-L on the PSI-H/-L/-I side of the PSI complex. PSI-H, -L, -O, and possibly -I are all involved in forming a domain in PSI that is involved in the interaction with light-harvesting complex II. 相似文献
2.
Shin-ichiro Ozawa Takahito Onishi Yuichiro Takahashi 《The Journal of biological chemistry》2010,285(26):20072-20079
Photosystem I (PSI) is a multiprotein complex consisting of the PSI core and peripheral light-harvesting complex I (LHCI) that together form the PSI-LHCI supercomplex in algae and higher plants. The supercomplex is synthesized in steps during which 12–15 core and 4–9 LHCI subunits are assembled. Here we report the isolation of a PSI subcomplex that separated on a sucrose density gradient from the thylakoid membranes isolated from logarithmic growth phase cells of the green alga Chlamydomonas reinhardtii. Pulse-chase labeling of total cellular proteins revealed that the subcomplex was synthesized de novo within 1 min and was converted to the mature PSI-LHCI during the 2-h chase period, indicating that the subcomplex was an assembly intermediate. The subcomplex was functional; it photo-oxidized P700 and demonstrated electron transfer activity. The subcomplex lacked PsaK and PsaG, however, and it bound PsaF and PsaJ weakly and was not associated with LHCI. It seemed likely that LHCI had been integrated into the subcomplex unstably and was dissociated during solubilization and/or fractionation. We, thus, infer that PsaK and PsaG stabilize the association between PSI core and LHCI complexes and that PsaK and PsaG bind to the PSI core complex after the integration of LHCI in one of the last steps of PSI complex assembly. 相似文献
3.
Erica Belgio Stefano Santabarbara David Bína Eliška Trsková Miroslava Herbstová Radek Kaňa Giuseppe Zucchelli Ondřej Prášil 《BBA》2017,1858(1):56-63
In the present work, we report the first comparative spectroscopic investigation between Photosystem I (PSI) complexes isolated from two red clade algae. Excitation energy transfer was measured in PSI from Chromera velia, an alga possessing a split PsaA protein, and from the model diatom Phaeodactylum tricornutum. In both cases, the estimated effective photochemical trapping time was in the 15–25 ps range, i.e. twice as fast as higher plants. In contrast to green phototrophs, the trapping time was rather constant across the whole emission spectrum. The weak wavelength dependence was attributed to the limited presence of long-wavelength emitting chlorophylls, as verified by low temperature spectroscopy. As the trapping kinetics of C. velia PSI were barely distinguishable from those of P. tricornutum PSI, it was concluded that the scission of PsaA protein had no significant impact on the overall PSI functionality. In conclusion, the two red clade algae analysed here, carried amongst the most efficient charge separation so far reported for isolated Photosystems. 相似文献
4.
Prasinophyceae are a broad class of early-branching eukaryotic green algae. These picophytoplankton are found ubiquitously throughout the ocean and contribute considerably to global carbon-fixation. Ostreococcus tauri, as the first sequenced prasinophyte, is a model species for studying the functional evolution of light-harvesting systems in photosynthetic eukaryotes. In this study we isolated and characterized O. tauri pigment-protein complexes. Two photosystem I (PSI) fractions were obtained by sucrose density gradient centrifugation in addition to free light-harvesting complex (LHC) fraction and photosystem II (PSII) core fractions. The smaller PSI fraction contains the PSI core proteins, LHCI, which are conserved in all green plants, Lhcp1, a prasinophyte-specific LHC protein, and the minor, monomeric LHCII proteins CP26 and CP29. The larger PSI fraction contained the same antenna proteins as the smaller, with the addition of Lhca6 and Lhcp2, and a 30% larger absorption cross-section. When O. tauri was grown under high-light conditions, only the smaller PSI fraction was present. The two PSI preparations were also found to be devoid of the far-red chlorophyll fluorescence (715-730 nm), a signature of PSI in oxygenic phototrophs. These unique features of O. tauri PSI may reflect primitive light-harvesting systems in green plants and their adaptation to marine ecosystems. Possible implications for the evolution of the LHC-superfamily in photosynthetic eukaryotes are discussed. 相似文献
5.
Ravi Danielsson 《BBA》2004,1608(1):53-61
Electron paramagnetic resonance (EPR) was used to quantify Photosystem I (PSI) and PSII in vesicles originating from a series of well-defined but different domains of the thylakoid membrane in spinach prepared by non-detergent techniques. Thylakoids from spinach were fragmented by sonication and separated by aqueous polymer two-phase partitioning into vesicles originating from grana and stroma lamellae. The grana vesicles were further sonicated and separated into two vesicle preparations originating from the grana margins and the appressed domains of grana (the grana core), respectively. PSI and PSII were determined in the same samples from the maximal size of the EPR signal from P700+ and YD, respectively. The following PSI/PSII ratios were found: thylakoids, 1.13; grana vesicles, 0.43; grana core, 0.25; grana margins, 1.28; stroma lamellae 3.10. In a sub-fraction of the stroma lamellae, denoted Y-100, PSI was highly enriched and the PSI/PSII ratio was 13. The antenna size of the respective photosystems was calculated from the experimental data and the assumption that a PSII center in the stroma lamellae (PSIIβ) has an antenna size of 100 Chl. This gave the following results: PSI in grana margins (PSIα) 300, PSI (PSIβ) in stroma lamellae 214, PSII in grana core (PSIIα) 280. The results suggest that PSI in grana margins have two additional light-harvesting complex II (LHCII) trimers per reaction center compared to PSI in stroma lamellae, and that PSII in grana has four LHCII trimers per monomer compared to PSII in stroma lamellae. Calculation of the total chlorophyll associated with PSI and PSII, respectively, suggests that more chlorophyll (about 10%) is associated with PSI than with PSII. 相似文献
6.
A cDNA clone encoding a 15.501 Da photosystem I (PSI) subunit of barley was isolated using an oligonucleotide based on the NH2-terminal amino acid sequence of the isolated protein. The polypeptide, which migrates with an apparent molecular mass of 9.5 kDa on denaturing SDS-PAGE, has been designated PSI-N, and the corresponding gene is PsaN. Analysis of the deduced protein sequence indicates a mature protein of 85 amino acid residues and a molecular mass of 9818 Da. PSI-N is a hydrophilic, extrinsic protein with no predicted membrane-spanning regions. The transit peptide of 60 residues (5683 Da) contains a predicted hydrophobic -helix, suggesting that the protein is routed into the thylakoid lumen. Thus, PSI-N is the second known lumenal protein component associated with PSI, together with PSI-F. 相似文献
7.
The membrane protein components of photosystem I (PSI) and II (PSII) from different species were prefractionated by liquid extraction and sucrose gradient ultracentrifugation and subsequently analyzed by reversed-phase high-performance liquid chromatography-electrospray ionization-mass spectrometry (RP-HPLC-ESI-MS) using poly-(styrene-divinylbenzene)-based monolithic capillary columns. The analytical method was shown to be very flexible and enabled the identification of antenna proteins as well as most of the proteins of the reaction center from PSI and PSII in various plant species with few RP-HPLC-ESI-MS analyses necessitating only minor adaptations in the gradients of acetonitrile in 0.05% aqueous trifluoroacetic acid. The membrane proteins, ranging in molecular mass (Mr) from 4196 (I protein) to more than 80,000 (PSI A/B) as well as isoforms were identified on the basis of their intact Mr and comparison with Mr deduced from known DNA or protein sequences. High quality mass spectra enabled the identification and quantitation of the nonphosphorylated and phosphorylated reaction center subunits D1, D2, and CP43 of PSII, containing five to seven membrane-spanning alpha-helices. Because of its high flexibility and suitability for proteins having a very wide range of Mr and hydrophobicities, the method is generally applicable to the analysis of complex mixtures of membrane proteins. 相似文献
8.
Maize Photosystem I : Identification of the Subunit which Binds Plastocyanin 总被引:1,自引:0,他引:1
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Photosystem I (PSI) has been isolated from mesophyll chloroplasts of mature maize leaves. The isolated PSI (PSI-200) was used as starting material for preparing an antenna-depleted core (PSI-100). Both of these preparations appear to be quite analogous to PSI complexes isolated from other plant tissue sources, such as those from C3 plants, as judged from NADP photoreduction assays, immunoblotting, and the ability of the complexes to form a covalent crosslinked product with spinach plastocyanin. The study suggests that the PSI complex from a C4 plant is similar to that isolated from a C3 plant in that both contain the plastocyanin docking protein although the apparent molecular weight of these respective subunits differ slightly. 相似文献
9.
Oxygenic photosynthesis is driven via sequential action of Photosystem II (PSII) and (PSI)reaction centers via the Z-scheme. Both of these pigment–membrane protein complexes are found in cyanobacteria, algae, and plants. Unlike PSII, PSI is remarkably stable and does not undergo limiting photo-damage. This stability, as well as other fundamental structural differences, makes PSI the most attractive reaction centers for applied photosynthetic applications. These applied applications exploit the efficient light harvesting and high quantum yield of PSI where the isolated PSI particles are redeployed providing electrons directly as a photocurrent or, via a coupled catalyst to yield H2. Recent advances in molecular genetics, synthetic biology, and nanotechnology have merged to allow PSI to be integrated into a myriad of biohybrid devices. In photocurrent producing devices, PSI has been immobilized onto various electrode substrates with a continuously evolving toolkit of strategies and novel reagents. However, these innovative yet highly variable designs make it difficult to identify the rate-limiting steps and/or components that function as bottlenecks in PSI-biohybrid devices. In this study we aim to highlight these recent advances with a focus on identifying the similarities and differences in electrode surfaces, immobilization/orientation strategies, and artificial redox mediators. Collectively this work has been able to maintain an annual increase in photocurrent density (A cm− 2) of ~ 10-fold over the past decade. The potential drawbacks and attractive features of some of these schemes are also discussed with their feasibility on a large-scale. As an environmentally benign and renewable resource, PSI may provide a new sustainable source of bioenergy. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: Keys to Produce Clean Energy. 相似文献
10.
We report a structural characterization by electron microscopy and image analysis of a supramolecular complex consisting of Photosystem I (PSI) and the chlorophyll-binding protein IsiA from a mutant of the cyanobacterium Synechocystis PCC 6803 lacking the PsaF and PsaJ subunits. The circular complex consists of a central PSI trimer surrounded by a ring of 17 IsiA units, one less than in the wild-type supercomplex. We conclude that PsaF and PsaJ are not obligatory for the binding of the IsiA ring, and that the size of the PSI complex determines the number of IsiA units in the ring. The resulting number of 17 copies implies that each PSI monomer has a different association to the IsiA ring. 相似文献
11.
Phosphorylation-dependent movement of the light-harvesting complex II (LHCII) between photosystem II (PSII) and photosystem I (PSI) takes place in order to balance the function of the two photosystems. Traditionally, the phosphorylatable fraction of LHCII has been considered as the functional unit of this dynamic regulation. Here, a mechanical fractionation of the thylakoid membrane of Spinacia oleracea was performed from leaves both in the phosphorylated state (low light, LL) and in the dephosphorylated state (dark, D) in order to compare the phosphorylation-dependent protein movements with the excitation changes occurring in the two photosystems upon LHCII phosphorylation. Despite the fact that several LHCII proteins migrate to stroma lamellae when LHCII is phosphorylated, no increase occurs in the 77 K fluorescence emitted from PSI in this membrane fraction. On the contrary, such an increase in fluorescence occurs in the grana margin fraction, and the functionally important mobile unit is the PSI-LHCI complex. A new model for LHCII phosphorylation driven regulation of relative PSII/PSI excitation thus emphasises an increase in PSI absorption cross-section occurring in grana margins upon LHCII phosphorylation and resulting from the movement of PSI-LHCI complexes from stroma lamellae and subsequent co-operation with the P-LHCII antenna from the grana. The grana margins probably give a flexibility for regulation of linear and cyclic electron flow in plant chloroplasts. 相似文献
12.
In this study, the photosystem I (PSI) highly hydrophobic proteins present within stroma lamellae of the thylakoid membrane were separated by RP-HPLC and identified either by in-solution trypsin digestion peptide fragment fingerprinting or by the close correspondence between the intact mass measurements (IMMs) and those expected from the DNA sequence. Protein identification performed by MS/MS was as reliable as IMMs. Thus, IMM is an easy and valid method for identifying proteins that have no PTMs. This paper reports the M(r) for all PSI proteins in ten different species, including those whose genes have not yet been cloned. Lhca5 was revealed unequivocally in four species, corroborating that it is indeed a protein belonging to the light-harvesting antenna of PSI. In all species examined, the product of the Lhca6 gene has never been revealed. Concerning core proteins, Psa-O has been revealed in three species; isoforms of Psa-D and Psa-E have been found in both monocots and dicots. Small proteins like Psa-I and Psa-J are well separated and identified. RP-HPLC produces reliable fingerprints and reveals that the relative amounts of PSI proteins appear to be markedly different. 相似文献
13.
The precursor of photosystem I (PSI) subunit II (pre-subunit II) synthesized in vitro, was found to bind to the holo-PSI complex, both within the thylakoids and outside, after detergent extraction of PSI from the membranes. Chloroplast stromal fraction added to the purified PSI complexes, containing the labeled pre-subunit II, induced the processing of the precursor to the mature form. This implies that processing can occur within the isolated complex, after the integration of the precursor. The results presented suggest that certain aspects of biogenesis of membranal protein complexes can be studied in detergent-extracted purified complexes. 相似文献
14.
K.N. Sathish Yadav Dmitry A. Semchonok Lukáš Nosek Roman Kouřil Geoffrey Fucile Egbert J. Boekema Lutz A. Eichacker 《BBA》2017,1858(1):12-20
Photosystem I (PSI) is a pigment-protein complex required for the light-dependent reactions of photosynthesis and participates in light-harvesting and redox-driven chloroplast metabolism. Assembly of PSI into supercomplexes with light harvesting complex (LHC) II, cytochrome b6f (Cytb6f) or NAD(P)H dehydrogenase complex (NDH) has been proposed as a means for regulating photosynthesis. However, structural details about the binding positions in plant PSI are lacking. We analyzed large data sets of electron microscopy single particle projections of supercomplexes obtained from the stroma membrane of Arabidopsis thaliana. By single particle analysis, we established the binding position of Cytb6f at the antenna side of PSI. The rectangular-shaped Cytb6f dimer binds at the side where Lhca1 is located. The complex binds with its short side rather than its long side to PSI, which may explain why these supercomplexes are difficult to purify and easily disrupted. Refined analysis of the interaction between PSI and the NDH complex indicates that in total up to 6 copies of PSI can arrange with one NDH complex. Most PSI-NDH supercomplexes appeared to have 1–3 PSI copies associated. Finally, the PSI-LHCII supercomplex was found to bind an additional LHCII trimer at two positions on the LHCI side in Arabidopsis. The organization of PSI, either in a complex with NDH or with Cytb6f, may improve regulation of electron transport by the control of binding partners and distances in small domains. 相似文献
15.
Monomerization and trimerization of photosystem I (PSI) in cyanobacteria are reversible to response to light switched off
and on, which leads to “energy spillover” to regulate excitation of the two photosystems in balance. Considering that PSI
is a trans-membrane protein embedded in thylakoid membranes, the monomerization or trimerization must involve a movement of
PSI in the membranes. In this work, the mobility of PSI was demonstrated by dependence of the monomerization and trimerization
on temperature for intact Spirulina platensis cells undergoing a light-to-dark or a dark-to-light transition. Based on the characteristic absorbance of monomers and trimmers,
it confirms that both monomerization and trimerization are temperature-sensitive. The relative populations of the monomers
and trimmers are invariable above the phase transition temperature (T
PT) while directly proportional to temperature below T
PT. On the other hand, the rate to reach the equilibrium population is proportional to temperature above T
PT but invariable below T
PT. The PSI mobility and the temperature-dependent population are contrary to those of plastoquinone (PQ) molecules because
PSI is a trans-membrane protein while PQ molecules are small diffusive electron carriers in thylakoid membranes as well as
their distinctive sizes and environments. The less monomerization of PSI but the invariable time constant at lower temperature
below T
PT may be due to that accumulation of the reduced PQ molecules results in decrease of the stromal-side H+ concentration which is a driving force of PSI monomerization. 相似文献
16.
Two formerly-uncharacterized subunits of 9 kDa and 14 kDa were found in spinach PSI complex. The 9 kDa subunit was released upon removal of antenna chlorophyll complex, whereas the 14 kDa subunit was tightly bound to the core complex. We determined the N-terminal amino acid sequence of the 9 kDa, and an internal sequence of the 14 kDa subunit after protease treatment, since the N-terminus of the latter protein was blocked. These partial sequences suggested that both subunits are new PSI components. 相似文献
17.
An active photosystem (PSI) complex was isolated from a phycobilisome-less mutant of the mesophilic cyanobacterium Synechococcus PCC 7002 by a mild procedure. Purification of PS I was achieved using a sucrose density gradient and an isoelectric focussing subsequent to the extraction of PSI from thylakoids with dodecyl--maltoside. Electron microscopy and gel filtration HPLC suggested that the isolated complex represents a trimeric form of PSI. The trimeric form was resistant to pH or detergent exchange. A molecular weight of 690 kDa to 760 kDa has been determined for the complex by gel filtration HPLC in several detergents or mixtures of detergents.The PSI complex contains the polypeptides of the psaA, psaB, psaC, psaD, psaE, psaL gene products and two small polypeptides as determined by SDS-PAGE and N-terminal sequencing; its antenna size is 77±2 Chl a/P700. The full set of Fe-S clusters (FA, FB and FX) was observed by EPR-spectroscopy. A preliminary characterization of crystals obtained from this preparation was carried out using SDS-PAGE, optical and EPR spectroscopy.Abbreviations BA
benzamidine
- CAS
6-amino-n-caproic acid
- C8-G
octyl--D-glucopyranoside
- C12-M
lauryl--D-maltoside
- C10-M
decyl--D-maltoside
- C8-TG
octyl--D-thioglucoside
- Chl a
chlorophyll a
- EPR
electron paramagnetic resonance
- FA, FB, FX
iron-sulfur centers
- HPLC
high perfomance liquid chromatography
- kDa
kilodalton(s)
- LDAO
lauryldimethylamine oxide
- MES
2-(N-morpholino)ethanesulfonic acid
- PSI
Photosystem I
- PS II
Photosystem II
- P700
primary electron donor
- SB12
sulfobetain 12
- SDS-PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis
- Tris
tris(hydroxymethyl)-aminomethane 相似文献
18.
Currently, there are very little data available regarding the photosynthetic apparatus of red algae. We have analyzed the genes for Photosystem I in the recently sequenced genome of the red alga Galdieria sulphuraria. All subunits that are conserved between plants and cyanobacteria were unambiguously identified in the Galdieria genome: PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaI, PsaJ, PsaK and PsaL. From the plant specific subunits, PsaN and PsaO were identified but the sequence homology was much lower than for the subunits that are present in plants and cyanobacteria. The subunit PsaX, which is specific for thermophilic cyanobacteria, is not present in the Galdieria genome, whereas PsaM is a plastid-encoded protein as in other red algae. The sequences of the core subunits of PSI were further analyzed by mapping of the conserved areas in the crystal structures of cyanobacterial and plant PSI. The structural comparison shows that PSI from the red alga Galdieria may represent a common ancestral structure at the interface between cyanobacterial and plant PSI. Some subunits have a “zwitter” structure that contains structural elements that show similarities with either plant or cyanobacterial PSI. The structure of PsaL, which is responsible for the trimerization of PSI in cyanobacteria, lacks a short helix and the Ca2+ binding site, which are essential for trimer formation indicating that the Galdieria PSI is a monomer. However the sequence homology to plant PsaL is low and lacks strong conservation of the interaction sites with PsaH. Furthermore, the sites for interaction of plant PSI with the LHCI complex are not well conserved between plants and Galdieria, which may indicate that Galdieria may contain a PSI that is evolutionarily much more ancient than PSI from green algae, plants and the current cyanobacteria. 相似文献
19.
Ruan X Xu Q Mao HB Li GF Wei J Gong YD Kuang TY Zhao NM 《Journal of Protein Chemistry》2001,20(3):247-254
Changes in the protein secondary structure and electron transport activity of the Triton X-100-treated photosystem I (PSI) and photosystem II (PSII) complexes after strong illumination treatment were studied using Fourier transform-infrared (FT-IR) spectroscopy and an oxygen electrode. Short periods of photoinhibitory treatment led to obvious decreases in the rates of PSI-mediated electron transport activity and PSII-mediated oxygen evolution in the native or Triton-treated PSI and PSII complexes. In the native PSI and PSII complexes, the protein secondary structures had little changes after the photoinhibitory treatment. However, in both Triton-treated PSI and PSII complexes, short photoinhibition times caused significant loss of -helical content and increase of -sheet structure, similar to the conformational changes in samples of Triton-treated PSI and PSII complexes after long periods of dark incubation. Our results demonstrate that strong-light treatment to the Triton-treated PSI and PSII complexes accelerates destruction of the transmembrane structure of proteins in the two photosynthetic membranes. 相似文献
20.
Insertion and assembly of the precursor of subunit II into the photosystem I complex may precede its processing.
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The biogenesis and assembly of subunit II of photosystem I (PSI) (psaD gene product) were studied and characterized. The precursor and the mature form were produced in vitro and incubated with intact plastids or isolated thylakoids. Following import of the precursor into isolated plastids, mostly the mature form of subunit II was found in the thylakoids. However, when the processing activity was inhibited only the precursor form was present in the membranes. The precursor was processed by a stromal peptidase and processing could occur before or after insertion of the precursor into the thylakoids. Following insertion into isolated thylakoids, both the precursor and the mature form of subunit II were confined to the PSI complex. Insertion of the mature form of subunit II was much less efficient than that of the precursor. Kinetic studies showed that the precursor was inserted into the membrane. Only at a later stage, the mature form began to accumulate. These results suggest that in vivo the precursor of subunit II is inserted and embedded in the thylakoids, as part of the PSI complex. Only later, it is processed to the mature form through the action of a stromal peptidase. 相似文献