Photosystem II Dotaz Zobrazit nápovědu
In nature, plants are continuously exposed to varying environmental conditions. They have developed a wide range of adaptive mechanisms, which ensure their survival and maintenance of stable photosynthetic performance. Photosynthesis is delicately regulated at the level of the thylakoid membrane of chloroplasts and the regulatory mechanisms include a reversible formation of a large variety of specific protein-protein complexes, supercomplexes or even larger assemblies known as megacomplexes. Revealing their structures is crucial for better understanding of their function and relevance in photosynthesis. Here we focus our attention on the isolation and a structural characterization of various large protein supercomplexes and megacomplexes, which involve Photosystem II and Photosystem I, the key constituents of photosynthetic apparatus. The photosystems are often attached to other protein complexes in thylakoid membranes such as light harvesting complexes, cytochrome b 6 f complex, and NAD(P)H dehydrogenase. Structural models of individual supercomplexes and megacomplexes provide essential details of their architecture, which allow us to discuss their function as well as physiological significance.
- Klíčová slova
- Clear native gel electrophoresis, Electron microscopy, Megacomplex, Photosystem I, Photosystem II, Supercomplex,
- MeSH
- fotosyntéza fyziologie MeSH
- fotosystém I (proteinový komplex) * chemie metabolismus MeSH
- fotosystém II (proteinový komplex) * chemie metabolismus MeSH
- tylakoidy enzymologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- fotosystém I (proteinový komplex) * MeSH
- fotosystém II (proteinový komplex) * MeSH
N-(Alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides (series A) and N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides (series B) affecting photosystem (PS) II inhibited photosynthetic electron transport (PET) in spinach chloroplasts. Their inhibitory activity depended on the compound lipophilicity as well as on the position of the alkoxy substituent. The most potent PET inhibitors were 2-hydroxy-N-phenylnaphthalene-1-carboxamide and N-[3-(but-2-yloxy)phenyl]-2-hydroxynaphthalene-1-carboxamide within series A (IC50=28.9 and 42.5µM, respectively) and 1-hydroxy-N-(3-propoxyphenyl)naphthalene-2-carboxamide and 1-hydroxy-N-(3-ethoxyphenyl)-naphthalene-2-carboxamide (IC50=2.0 and 3.1µM, respectively) within series B. The inhibitory activity of C'(3) or C'(4) alkoxy substituted compounds of series B was considerably higher than that of C'(2) ones within series A. The PET-inhibiting activities of both series were compared with the PET inhibition of isomeric N-alkoxyphenyl-3-hydroxynaphthalene-2-carboxamides (series C) reported recently. Interactions of the studied compounds with chlorophyll a and aromatic amino acids present in pigment-protein complexes mainly in PS II were documented by fluorescence spectroscopy. The section between P680 and plastoquinone QB in the PET chain occurring on the acceptor side of PSII can be suggested as the site of action of the compounds.
- Klíčová slova
- Hill reaction, Hydroxynaphthalenecarboxamides, Photosystem II, Structure–activity relationships,
- MeSH
- antibakteriální látky chemie metabolismus MeSH
- fotosystém II (proteinový komplex) antagonisté a inhibitory metabolismus MeSH
- naftaleny chemie metabolismus MeSH
- rostlinné proteiny antagonisté a inhibitory metabolismus MeSH
- Spinacia oleracea účinky léků metabolismus MeSH
- transport elektronů účinky léků MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- antibakteriální látky MeSH
- fotosystém II (proteinový komplex) MeSH
- naftaleny MeSH
- rostlinné proteiny MeSH
BACKGROUND: Photosystem II proteins of higher plant chloroplasts are prone to oxidative stress, and most prominently the reaction center-binding D1 protein is damaged under abiotic stress. The reactive oxygen species produced under these stress conditions have been suggested to be responsible for the protein injury. SCOPE OF REVIEW: Recently, it has been shown that the primary and secondary products of non-enzymatic and enzymatic lipid peroxidation have a capability to modify photosystem II proteins. Here, we give an overview showing how lipid peroxidation products formed under light stress and heat stress in the thylakoid membranes cause oxidative modification of proteins in higher plant photosystem II. MAJOR CONCLUSIONS: Damage to photosystem II proteins by lipid peroxidation products represents a new mechanism underlying photoinhibition and heat inactivation. GENERAL SIGNIFICANCE: Complete characterization of photosystem II protein damage is of crucial importance because avoidance of the damage makes plants to survive under various abiotic stresses. Further physiological significance of photosystem II protein oxidation by lipid peroxidation product should have a potential relevance to plant acclimation because the oxidized proteins might serve as signaling molecules.
- Klíčová slova
- Lipid peroxidation, Photosystem II, Protein oxidation, Reactive carbonyl species, Reactive oxygen species,
- MeSH
- chloroplasty metabolismus fyziologie MeSH
- fotosystém II (proteinový komplex) metabolismus fyziologie MeSH
- fyziologický stres fyziologie MeSH
- oxidace-redukce MeSH
- oxidační stres fyziologie MeSH
- peroxidace lipidů fyziologie MeSH
- reaktivní formy kyslíku metabolismus MeSH
- rostliny metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- fotosystém II (proteinový komplex) MeSH
- reaktivní formy kyslíku MeSH
Photosystem II (PSII) is a multi-subunit pigment-protein complex and is one of several protein assemblies that function cooperatively in photosynthesis in plants and cyanobacteria. As more structural data on PSII become available, new questions arise concerning the nature of the charge separation in PSII reaction center (RC). The crystal structure of PSII RC from cyanobacteria Thermosynechococcus vulcanus was selected for the computational study of conformational changes in photosystem II associated to the charge separation process. The parameterization of cofactors and lipids for classical MD simulation with Amber force field was performed. The parametrized complex of PSII was embedded in the lipid membrane for MD simulation with Amber in Gromacs. The conformational behavior of protein and the cofactors directly involved in the charge separation were studied by MD simulations and QM/MM calculations. This study identified the most likely mechanism of the proton-coupled reduction of plastoquinone QB. After the charge separation and the first electron transfer to QB, the system undergoes conformational change allowing the first proton transfer to QB- mediated via Ser264. After the second electron transfer to QBH, the system again adopts conformation allowing the second proton transfer to QBH-. The reduced QBH2 would then leave the binding pocket.
- Klíčová slova
- MD simulations, Photosystem II reaction center, Plastoquinone, Proton-coupled reduction,
- MeSH
- bakteriální proteiny chemie MeSH
- fotosystém II (proteinový komplex) chemie MeSH
- lipidové dvojvrstvy chemie MeSH
- simulace molekulární dynamiky * MeSH
- sinice enzymologie MeSH
- Thermosynechococcus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- bakteriální proteiny MeSH
- fotosystém II (proteinový komplex) MeSH
- lipidové dvojvrstvy MeSH
Photosysthetic cleavage of water molecules to molecular oxygen is a crucial process for all aerobic life on the Earth. Light-driven oxidation of water occurs in photosystem II (PSII) - a pigment-protein complex embedded in the thylakoid membrane of plants, algae and cyanobacteria. Electron transport across the thylakoid membrane terminated by NADPH and ATP formation is inadvertently coupled with the formation of reactive oxygen species (ROS). Reactive oxygen species are mainly produced by photosystem I; however, under certain circumstances, PSII contributes to the overall formation of ROS in the thylakoid membrane. Under limitation of electron transport reaction between both photosystems, photoreduction of molecular oxygen by the reducing side of PSII generates a superoxide anion radical, its dismutation to hydrogen peroxide and the subsequent formation of a hydroxyl radical terminates the overall process of ROS formation on the PSII electron acceptor side. On the PSII electron donor side, partial or complete inhibition of enzymatic activity of the water-splitting manganese complex is coupled with incomplete oxidation of water to hydrogen peroxide. The review points out the mechanistic aspects in the production of ROS on both the electron acceptor and electron donor side of PSII.
Structure and organisation of Photosystem I and Photosystem II isolated from red alga Cyanidium caldarium was determined by electron microscopy and single particle image analysis. The overall structure of Photosystem II was found to be similar to that known from cyanobacteria. The location of additional 20 kDa (PsbQ') extrinsic protein that forms part of the oxygen evolving complex was suggested to be in the vicinity of cytochrome c-550 (PsbV) and the 12 kDa (PsbU) protein. Photosystem I was determined as a monomeric unit consisting of PsaA/B core complex with varying amounts of antenna subunits attached. The number of these subunits was seen to be dependent on the light conditions used during cell cultivation. The role of PsaH and PsaG proteins of Photosystem I in trimerisation and antennae complexes binding is discussed.
- MeSH
- fotosystém I (proteinový komplex) chemie izolace a purifikace metabolismus ultrastruktura MeSH
- fotosystém II (proteinový komplex) chemie izolace a purifikace metabolismus ultrastruktura MeSH
- Rhodophyta chemie MeSH
- sinice chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
- Názvy látek
- fotosystém I (proteinový komplex) MeSH
- fotosystém II (proteinový komplex) MeSH
Photosystem II (PSII) complexes are organized into large supercomplexes with variable amounts of light-harvesting proteins (Lhcb). A typical PSII supercomplex in plants is formed by four trimers of Lhcb proteins (LHCII trimers), which are bound to the PSII core dimer via monomeric antenna proteins. However, the architecture of PSII supercomplexes in Norway spruce[Picea abies (L.) Karst.] is different, most likely due to a lack of two Lhcb proteins, Lhcb6 and Lhcb3. Interestingly, the spruce PSII supercomplex shares similar structural features with its counterpart in the green alga Chlamydomonas reinhardtii [Kouřil et al. (2016) New Phytol. 210, 808-814]. Here we present a single-particle electron microscopy study of isolated PSII supercomplexes from Norway spruce that revealed binding of a variable amount of LHCII trimers to the PSII core dimer at positions that have never been observed in any other plant species so far. The largest spruce PSII supercomplex, which was found to bind eight LHCII trimers, is even larger than the current largest known PSII supercomplex from C. reinhardtii. We have also shown that the spruce PSII supercomplexes can form various types of PSII megacomplexes, which were also identified in intact grana membranes. Some of these large PSII supercomplexes and megacomplexes were identified also in Pinus sylvestris, another representative of the Pinaceae family. The structural variability and complexity of LHCII organization in Pinaceae seems to be related to the absence of Lhcb6 and Lhcb3 in this family, and may be beneficial for the optimization of light-harvesting under varying environmental conditions.
- Klíčová slova
- Picea abies, Pinus sylvestris, clear native polyacrylamide electrophoresis, grana membrane, megacomplex, photosystem II, single-particle electron microscopy, supercomplex,
- MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- smrk metabolismus MeSH
- světlosběrné proteinové komplexy chemie metabolismus MeSH
- terciární struktura proteinů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- fotosystém II (proteinový komplex) MeSH
- světlosběrné proteinové komplexy MeSH
Robust photosynthesis in chloroplasts and cyanobacteria requires the participation of accessory proteins to facilitate the assembly and maintenance of the photosynthetic apparatus located within the thylakoid membranes. The highly conserved Ycf48 protein acts early in the biogenesis of the oxygen-evolving photosystem II (PSII) complex by binding to newly synthesized precursor D1 subunit and by promoting efficient association with the D2 protein to form a PSII reaction center (PSII RC) assembly intermediate. Ycf48 is also required for efficient replacement of damaged D1 during the repair of PSII. However, the structural features underpinning Ycf48 function remain unclear. Here we show that Ycf48 proteins encoded by the thermophilic cyanobacterium Thermosynechococcus elongatus and the red alga Cyanidioschyzon merolae form seven-bladed beta-propellers with the 19-aa insertion characteristic of eukaryotic Ycf48 located at the junction of blades 3 and 4. Knowledge of these structures has allowed us to identify a conserved "Arg patch" on the surface of Ycf48 that is important for binding of Ycf48 to PSII RCs but also to larger complexes, including trimeric photosystem I (PSI). Reduced accumulation of chlorophyll in the absence of Ycf48 and the association of Ycf48 with PSI provide evidence of a more wide-ranging role for Ycf48 in the biogenesis of the photosynthetic apparatus than previously thought. Copurification of Ycf48 with the cyanobacterial YidC protein insertase supports the involvement of Ycf48 during the cotranslational insertion of chlorophyll-binding apopolypeptides into the membrane.
- Klíčová slova
- chlorophyll-binding proteins, photosynthesis, photosystem II,
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- fotosystém I (proteinový komplex) biosyntéza genetika MeSH
- fotosystém II (proteinový komplex) biosyntéza genetika MeSH
- sinice genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- bakteriální proteiny MeSH
- fotosystém I (proteinový komplex) MeSH
- fotosystém II (proteinový komplex) MeSH
Cytochrome (Cyt) b559 is a key component of the photosystem II complex (PSII) that is essential for its proper functioning and assembly. Site-directed mutants of the model cyanobacterium Synechocystis sp. PCC6803 with mutated heme axial ligands of Cyt b559 have little PSII and are therefore unable to grow photoautotrophically. Here we describe two types of Synechocystis autotrophic transformants that retained the same mutations in Cyt b559 but are able to accumulate PSII and grow photoautotrophically. Whole-genome sequencing revealed that all of these autotrophic transformants carried a variable number of tandem repeats (from 5 to 15) of chromosomal segments containing the psbEFLJ operon. RNA-seq analysis showed greatly increased transcript levels of the psbEFLJ operon in these autotrophic transformants. Multiple copies of the psbEFLJ operon in these transformants were only maintained during autotrophic growth, while its copy numbers gradually decreased under photoheterotrophic conditions. Two-dimensional PAGE analysis of membrane proteins revealed a strong deficiency in PSII complexes in the Cyt b559 mutants that was reversed in the autotrophic transformants. These results illustrate how tandem gene amplification restores PSII accumulation and photoautotrophic growth in Cyt b559 mutants of cyanobacteria, and may serve as an important adaptive mechanism for cyanobacterial survival.
- Klíčová slova
- cyanobacterium, cytochrome b559, photosynthesis, photosystem II (PSII), tandem gene amplification,
- MeSH
- amplifikace genu MeSH
- cytochromy b genetika metabolismus MeSH
- cytochromy typu b genetika metabolismus MeSH
- fotosystém II (proteinový komplex) * genetika metabolismus MeSH
- Synechocystis * metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cytochromy b MeSH
- cytochromy typu b MeSH
- fotosystém II (proteinový komplex) * MeSH
Ring-substituted 8-hydroxyquinoline-2-carboxanilides inhibited photosynthetic electron transport (PET) through photosystem (PS) II. Their inhibitory efficiency depended on the compound lipophilicity, the electronic properties of the substituent R and the position of the substituent R on the benzene ring. The most effective inhibitors showing IC50 values in the range 2.3-3.6μM were substituted in C'(3) by F, CH3, Cl and Br. The dependence of the PET-inhibiting activity on the lipophilicity of the compounds was quasi-parabolic for 3-substituted derivatives, while for C'(2) ones a slight increase and for C'(4) derivatives a sharp decrease of the activity were observed with increasing lipophilicity. In addition, the dependence of PET-inhibiting activity on electronic Hammett's σ parameter of the substituent R was observed with optimum σ value 0.06 for C'(4) and 0.34 for C'(3) substituted derivatives, while the value of σ parameter did not significantly influence the PET-inhibiting activity of C'(2) substituted compounds. Interactions of the studied compounds with chlorophyll a and aromatic amino acids present in the pigment-protein complexes mainly in PS II were documented by fluorescence spectroscopy. The section between P680 and plastoquinone QB occurring on the acceptor side of PS II can be suggested as the site of action of the compounds.
- Klíčová slova
- 8-Hydroxyquinolines, Hill reaction, Photosystem II, Structure–activity relationships,
- MeSH
- anilidy chemická syntéza chemie metabolismus MeSH
- chlorofyl a MeSH
- chlorofyl chemie MeSH
- chloroplasty metabolismus MeSH
- fluorescenční spektrometrie MeSH
- fotosyntéza MeSH
- fotosystém II (proteinový komplex) antagonisté a inhibitory metabolismus MeSH
- oxychinolin chemie MeSH
- Spinacia oleracea metabolismus MeSH
- transport elektronů MeSH
- vazba proteinů MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- anilidy MeSH
- chlorofyl a MeSH
- chlorofyl MeSH
- fotosystém II (proteinový komplex) MeSH
- oxychinolin MeSH
