1.97.1.12 additional information in the Phaeodactylum tricornutum alga, as inmost diatoms, cytochrome c6 is the only electron donor to photosystem I, and thus they lack plastocyanin as an alternative electron carrier. Analysis of electron transfer to Phaeodactylum photosystem I from several plastocyanins from cyanobacteria, green algae and plants, as compared with its own cytochrome c6, overview. Diatom photosystem I is able to effectively react with eukaryotic acidic plastocyanins, although with less efficiency than with Phaeodactylum cytochrome c6. This efficiency increases in some green alga plastocyanin mutants mimicking the electrostatics of the interaction site on the diatom cytochrome. In addition, the structure of the transient electron transfer complex between cytochrome c6 and photosystem I from Phaeodactylum is analyzed by computational docking and compared to that of green lineage and mixed systems. The Phaeodactylum system shows a lower efficiency than the green systems, both in the formation of the properly arranged [cytochrome c6-photosystem I] complex and in the electron transfer itself. Structural modeling, overview Phaeodactylum tricornutum ? - ? 89 1.97.1.12 additional information in vitro plastoquinone reduction assay with the addition of ferredoxin Flaveria bidentis ? - ? 89 1.97.1.12 additional information interaction analysis of photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 containing various quinones in the A1-site (phylloquinone PhQ in the wild-type strain and plastoquinone (PQ) or 2,3-dichloronaphthoquinone (Cl2NQ) in the menB deletion strain) and different numbers of Fe4S4 clusters (intact wild-type and ferredoxin-core complexes depleted of FA/FB centers) with external acceptors, overview. The electron transfer chain of PS I consists of the primary donor-chlorophyll (Chl) dimer P700, primary acceptor A0 (four Chl molecules), A1 (two phylloquinone molecules), and iron-sulfur clusters FX, FA, and FB.The terminal FA/FB clusters are located on the small extrinsic PsaC subunit. Electron transport in PS I occurs through both branches of the redox cofactors A and B from P700 to FX. Reaction center of PS I contains two molecules of phylloquinone (PhQ) that are characterized by extremely low midpoint redox potential Synechocystis sp. PCC 6803 ? - ? 89 1.97.1.12 additional information oxygen uptake in the light is analyzed in suspensions of isolated pea thylakoids upon inhibition of electron transport from photosystem II (PS II) by diuron and delivery of electrons to photosystem I (PS I) by means of artificial donors in the presence of ascorbate, O2 reduction in PS I. 2,6-dichlorophenolindophenol (DCPIP) cannot be used as the donor for photosystem I. N,N,N',N'-tetramethyl-p-phenylene diamine (TMPD), applied as a donor, does not affect immediately the reaction of the O2 reduction, since an increase in its concentration does not lead to an increase in the oxygen uptake rate in the light. In the experiments with TMPD, an increase in light intensity leads to an increase in the oxygen uptake rate, and this fact was interpreted as a consequence of the increase in the apparent rate constant of the reaction of the O2 reduction by the components of the acceptor side of photosystem I. TMPD redox transformation consists of only one step, while the DCPIP transformation includes two steps. Ascorbate is capable of donating electrons to the primary pair of PS I cofactors, P700+. Addition of either DCPIP or TMPD at concentration of 0.05 mM to the suspension containing both DCMU and ascorbate results in the twofold increase in the rate of the O2 consumption. O2 reduction by PS I uses ascorbate alone or in combination with lipophilic compounds as immediate donor of electrons Pisum sativum ? - ? 89 1.97.1.12 additional information photo-oxidation of P700 causes a broad increase in absorption in the near-infrared region due to presence of a chlorophyll cation radical (P700+) Synechocystis sp. PCC 6803 ? - ? 89 1.97.1.12 additional information photo-oxidation of P700 causes a broad increase in absorption in the near-infrared region due to presence of a chlorophyll cation radical (P700+) Chlamydomonas reinhardtii ? - ? 89 1.97.1.12 additional information reduction of ferredoxin by photosystem I (PSI) involves the [4Fe-4S] clusters FA and FB harbored by subunit PsaC, with FB being the direct electron transfer partner of ferredoxin. Assay in presence of 5 mM MgCl2, 30 mM NaCl and 0.03% beta-dodecyl-maltoside, with 1-2.5 mM sodium ascorbate and 0.008-0.025 mM 2,6-dichlorophenolindophenol Thermosynechococcus vestitus ? - ? 89 1.97.1.12 additional information reduction of ferredoxin by photosystem I (PSI) involves the [4Fe-4S] clusters FA and FB harbored by subunit PsaC, with FB being the direct electron transfer partner of ferredoxin. Assay in presence of 5 mM MgCl2, 30 mM NaCl and 0.03% beta-dodecyl-maltoside, with 1-2.5 mM sodium ascorbate and 0.008-0.025 mM 2,6-dichlorophenolindophenol Synechocystis sp. PCC 6803 ? - ? 89 1.97.1.12 additional information thylakoids freshly isolated from spinach are assayed for their ability to generate a light driven proton gradient. While high rates of cyclic electron flow are observed in vivo, isolated thylakoids show only very slow rates, suggesting that the activity of a key complex is lost or downregulated upon isolation. Isolation of thylakoids in the complete absence of DTTRED leads to loss of CEF activity that is only partially restored by subsequent addition of 2 mM DTTRED, redox titration of CEF activity, overview Spinacia oleracea ? - ? 89 1.97.1.12 additional information upon light excitation, the excited singlet state of the primary electron donor, P700 delivers an electron to the primary Chl acceptor A0A/ A0B forming the charge-separated state P700 +A0-. The electron is then transferred in sequence to A1A/ A1B, to the iron-sulfur cluster FX, and ultimately to FA/FB. The side production of superoxide radical in the A1-site by oxygen reduction via the Mehler reaction might comprise about 0.3% of the total electron flow in photosystem I, PS I. Interaction of PS I with external acceptors, methylviologen, 2,3-dichloro-naphthoquinone and oxygen, overview. Analysis of PS I complexes containing various quinones in the A1-binding site, i.e. phylloquinone PhQ, plastoquinone-9 PQ and 2,3-dichloro-naphthoquinone, as well as FX-core complexes, depleted of terminal iron-sulfur FA/FB clusters Synechocystis sp. PCC 6803 ? - ? 89 1.97.1.12 reduced cytochrome b6 + oxidized ferredoxin + hv - Flaveria bidentis oxidized cytochrome b6 + reduced ferredoxin - ? 442529 1.97.1.12 reduced cytochrome b6 + oxidized ferredoxin + hv - Spinacia oleracea oxidized cytochrome b6 + reduced ferredoxin - ? 442529 1.97.1.12 reduced cytochrome c6 + oxidized ferredoxin + hv - Phaeodactylum tricornutum oxidized cytochrome c6 + reduced ferredoxin - ? 442530 1.97.1.12 reduced cytochrome c6 + oxidized ferredoxin + hv - Synechocystis sp. PCC 6803 oxidized cytochrome c6 + reduced ferredoxin - ? 442530 1.97.1.12 reduced cytochrome c6 + oxidized flavodoxin + hv - Synechocystis sp. PCC 6803 oxidized cytochrome c6 + reduced flavodoxin - ? 442531 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Chlamydomonas reinhardtii oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Spinacia oleracea oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Arabidopsis thaliana oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Synechococcus sp. oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Synechocystis sp. oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Flaveria bidentis oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Mastigocladus laminosus oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Thermosynechococcus vestitus oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Cucumis sativus oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Synechocystis sp. PCC 6803 oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Psychotria henryi oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv characterization of the electron donor (plastocyanin) binding site. Plastocyanin binds in a small cavity on the lumenal surface of photosystem I, close to the center and with a slight bias toward the PsaL subunit of the complex Spinacia oleracea oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv photosystem I (PS I) mediates electron-transfer from plastocyanin to ferredoxin via a photochemically active chlorophyll dimer (P700), a monomeric chlorophyll electron acceptor (A0), a phylloquinone (A1), and three [4Fe-4S] clusters (FX/A/B) Synechococcus sp. oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv recombinant plastocyanin is the superior electron donor to photosystem I. Detailed analysis of PSI-mediated linear electron transfer from reduced plastocyanin to NADP+, in thylakoid membranes of wild type and a psaE mutant of Synechocystis PCC 6803 Synechocystis sp. oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv subunit PsaE (a peripheral subunit of the PSI complex) is involved in the docking of ferredoxin/flavodoxin to the PSI complex and also participates in the cyclic electron transfer around phosphosystem I Mastigocladus laminosus oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv the light-harvesting complexes and internal antenna of photosystem I absorb photons and transfer the excitation energy to P700, the primary electron donor. The subsequent charge separation and electron transport leads to the reduction of ferredoxin Chlamydomonas reinhardtii oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv the light-harvesting complexes and internal antenna of photosystem I absorb photons and transfer the excitation energy to P700, the primary electron donor. The subsequent charge separation and electron transport leads to the reduction of ferredoxin Arabidopsis thaliana oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv the light-harvesting complexes and internal antenna of photosystem I absorb photons and transfer the excitation energy to P700, the primary electron donor. The subsequent charge separation and electron transport leads to the reduction of ferredoxin Synechocystis sp. oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv the photosystem 1 subunit PsaF is involved in the docking of the electron-donor proteins plastocyanin and cytochrome c6, the recombinant protein binds to plastocyanin by a specific, native-like, electrostatic interaction Spinacia oleracea oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv variations in the luminal Mg(II) concentration may modulate the binding between plastocyanin and photosystem I subunit PsaF during the light-dark transitions, being stronger in the illuminated state Spinacia oleracea oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv ferredoxin from Thermosynechococcus elongatus Thermosynechococcus vestitus oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv ferredoxin from Thermosynechococcus elongatus Synechocystis sp. PCC 6803 oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv plastocyanins from Nostoc sp. PCC 7119, Monoraphidium braunii, Arabidopsis thaliana, Spinacia oleracea, and wild-type and mutant (E85K, Q88R, E85K/Q88R, E85V, and V93K) plastocyanins from Chlamydomonas reinhardtii, docking simulations and modeling Phaeodactylum tricornutum oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Arabidopsis thaliana Col-0 oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv - Chlamydomonas reinhardtii KRC91-1A oxidized plastocyanin + reduced ferredoxin - ? 413562 1.97.1.12 reduced plastocyanin + oxidized flavodoxin + hv - Synechocystis sp. PCC 6803 oxidized plastocyanin + reduced flavodoxin - ? 442538