pheophytin-a and plastoquinol
pheophytin-a has been researched along with plastoquinol* in 3 studies
Other Studies
3 other study(ies) available for pheophytin-a and plastoquinol
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Atomistic and Coarse Grain Topologies for the Cofactors Associated with the Photosystem II Core Complex.
Electron transfers within and between protein complexes are core processes of the electron transport chains occurring in thylakoid (chloroplast), mitochondrial, and bacterial membranes. These electron transfers involve a number of cofactors. Here we describe the derivation of molecular mechanics parameters for the cofactors associated with the function of the photosystem II core complex: plastoquinone, plastoquinol, heme b, chlorophyll A, pheophytin, and β-carotene. Parameters were also obtained for ubiquinol and ubiquinone, related cofactors involved in the respiratory chain. Parameters were derived at both atomistic and coarse grain (CG) resolutions, compatible with the building blocks of the GROMOS united-atom and Martini CG force fields, respectively. Structural and thermodynamic properties of the cofactors were compared to experimental values when available. The topologies were further tested in molecular dynamics simulations of the cofactors in their physiological environment, e.g., either in a lipid membrane environment or in complex with the heme binding protein bacterioferritin. Topics: beta Carotene; Chlorophyll; Chlorophyll A; Heme; Lipid Bilayers; Molecular Dynamics Simulation; Molecular Structure; Octanols; Pheophytins; Photosystem II Protein Complex; Plastoquinone; Protein Conformation; Thermodynamics; Ubiquinone; Water | 2015 |
Dissection of photosynthetic electron transport process in sweet sorghum under heat stress.
Plant photosynthesis and photosystem II (PSII) are susceptible to high temperature. However, photosynthetic electron transport process under heat stress remains unclear. To reveal this issue, chlorophyll a fluorescence and modulated 820 nm reflection were simultaneously detected in sweet sorghum. At 43°C, J step in the chlorophyll a fluorescence transient was significantly elevated, suggesting that electron transport beyond primary quinone of PSII (Q(A)) (primary quinone electron acceptor of PSII) was inhibited. PSI (Photosystem I) photochemical capacity was not influenced even under severe heat stress at 48°C. Thus, PSI oxidation was prolonged and PSI re-reduction did not reach normal level. The inhibition of electron transport between PSII and PSI can reduce the possibility of PSI photoinhibition under heat stress. PSII function recovered entirely one day after heat stress at 43°C, implying that sweet sorghum has certain self-remediation capacity. When the temperature reached 48°C, the maximum quantum yield for primary photochemistry and the electron transport from PSII donor side were remarkably decreased, which greatly limited the electron flow to PSI, and PSI re-reduction suspended. The efficiency of an electron transferred from the intersystem electron carrier (plastoquinol, PQH₂) to the end electron acceptors at the PSI acceptor side increased significantly at 48°C, and the reason was the greater inhibition of electron transport before PQH₂. Thus, the fragment from Q(A) to PQH₂ is the most heat sensitive in the electron transport chain between PSII and PSI in sweet sorghum. Topics: Chlorophyll; Chlorophyll A; Electron Transport; Heat-Shock Response; Kinetics; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Plant Leaves; Plant Proteins; Plastoquinone; Sorghum | 2013 |
Photosystem II proteins PsbL and PsbJ regulate electron flow to the plastoquinone pool.
The psbEFLJ operon of tobacco plastids encodes four bitopic low molecular mass transmembrane components of photosystem II. Here, we report the effect of inactivation of psbL on the directional forward electron flow of photosystem II as compared to that of the wild type and the psbJ deletion mutant, which is impaired in PSII electron flow to plastoquinone [Regel et al. (2001) J. Biol. Chem. 276, 41473-41478]. Exposure of Delta psbL plants to a saturating light pulse gives rise to the maximal fluorescence emission, Fm(L), which is followed within 4-6 s by a broader hitherto not observed second fluorescence peak in darkness, Fm(D). Conditions either facilitating oxidation or avoiding reduction of the plastoquinone pool do not affect the Fm(L) level of Delta psbL plants but prevent the appearance of Fm(D). The level of Fm(D) is proportional to the intensity and duration of the light pulse allowing reduction of the plastoquinone pool in dark-adapted leaves prior to the activation of PSI and oxidation of plastoquinol. Lowering the temperature decreases the Fm(D) level in the Delta psbL mutant, whereas it increases considerably the lifetime of Q(A)*- in the Delta psbJ mutant. The thermoluminescence signal generated by Q(A)*-/S(2) charge recombination is not affected; on the other hand, charge recombination of Q(B)*-/S(2,3) could not be detected in Delta psbL plants. PSII is highly sensitive to photoinhibition in Delta psbL. We conclude that PsbL prevents reduction of PSII by back electron flow from plastoquinol protecting PSII from photoinactivation, whereas PsbJ regulates forward electron flow from Q(A)*- to the plastoquinone pool. Therefore, both proteins contribute substantially to ensure unidirectional forward electron flow from PSII to the plastoquinone pool. Topics: Bacterial Proteins; Chlorophyll; Chlorophyll A; Darkness; Electron Transport; Hot Temperature; Kinetics; Light; Luminescent Measurements; Membrane Proteins; Mutation; Nicotiana; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Plant Leaves; Plastoquinone; Protein Subunits; Spectrometry, Fluorescence; Temperature | 2004 |