Structural and catalytic properties of the oxygen-evolving complex. Correlation of polypeptide and manganese release with the behavior of Z+ in chloroplasts and a highly resolved preparation of the PS II complex

Ghanotakis, Demetrios F.; Babcock, Gerald T.; Yocum, Charles F.

doi:10.1016/0005-2728(84)90180-4

Cited by 159 publications

(89 citation statements)

References 25 publications

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“…PSII-enriched membrane fragments were prepared from market spinach by the method described elsewhere (41,42). Under saturating continuous illumination, the oxygen evolution rate of the PSII membranes was 400-500 µmol of O 2 (mg of Chl) -1 h -1 in the presence of 1 mM K 3 Fe(CN) 6 and 0.25 mM 2,5-dichloro-p-benzoquinone (DCBQ) as electron acceptors.…”

Section: Methodsmentioning

confidence: 99%

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

et al. 2006

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Biogenesis and repair of the inorganic core (Mn 4 CaO x Cl y ), in the water-oxidizing complex of photosystem II (WOC-PSII), occurs through the light-induced (re)assembly of its free elementary ions and the apo-WOC-PSII protein, a reaction known as photoactivation. Herein, we use electron paramagnetic resonance (EPR) spectroscopy to characterize changes in the ligand coordination environment of the first photoactivation intermediate, the photo-oxidized Mn 3+ bound to apo-WOC-PSII. On the basis of the observed changes in electron Zeeman (g eff ), 55 Mn hyperfine (A Z ) interaction, and the EPR transition probabilities, the photogenerated Mn 3+ is shown to exist in two pH-dependent forms, differing in terms of strength and symmetry of their ligand fields. The transition from an EPR-invisible low-pH form to an EPR-active high-pH form occurs by deprotonation of an ionizable ligand bound to Mn 3+ , implicated to be a water molecule: [Mn 3+ (OH 2 In the absence of Ca 2+ , the EPR-active Mn 3+ exhibits a strong pH dependence (pH ∼6.5-9) of its ligand-field symmetry (rhombicity ∆δ ) 10%, derived from g eff ) and A Z (∆A Z ) 22%), attributable to a protein conformational change. Binding of Ca 2+ to its effector site eliminates this pH dependence and locks both g eff and A Z at values observed in the absence of Ca 2+ at alkaline pH. Thus, Ca 2+ directly controls the coordination environment and binds close to the highaffinity Mn 3+ , probably sharing a bridging ligand. This Ca 2+ effect and the pH-induced changes are consistent with the ionization of the bridging water molecule, predicting that [ A single tight-binding Ca 2+ ion is essential for photosynthethic O 2 evolution activity in ViVo (1-5). Calcium is located within the water-oxidizing complex of photosystem II (PSII-WOC), 1 comprised of an oxo/aquo-bridged inorganic core whose stoichiometry, Mn 4 CaO x , is based on several lines of evidence, including X-ray absorption (6-9), electron paramagnetic resonance (EPR) spectroscopy (10,11), and the recent X-ray diffraction (XRD) data (12, 13). Mn-, Sr-, and Ca-extended X-ray absorption fine structure (EXAFS) spectroscopies accurately place the calcium effector site at 3.3-3.5 Å from Mn atoms. However, the relative position of Ca 2+ within the Mn 4 O x cluster differs according to which type of data is emphasized and the assumptions of the models used to interpret the raw data. Spectroscopic and XRD data have constrained the possible core topologies to only a few types, with the structures given in Chart 1 proposed on the basis of one or more lines of evidence (9)(10)(11)13). These structural proposals have led to a number of mechanistic proposals for the role of calcium in O 2 evolution reviewed elsewhere (11,(14)(15)(16)(17).Dissection of the functional roles of the inorganic cofactors has come from in Vitro studies of the photoactivation process, which is defined as the assembly of the inorganic core during biogenesis and repair of the WOC. In Vitro photoactivation of the WOC is described by the following ...

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Section: Methodsmentioning

confidence: 99%

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

et al. 2006

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“…All procedures were carried at 0°C to 4°C. PSII core particles and LHCII were isolated according to Ghanotakis et al (1984) and Simidjiev et al (1997), respectively. The isolated complexes were stored in 0.5-mL Eppendorf tubes under 280°C.…”

Section: Isolation Of Thylakoid Membranes Psii Core Particles and Lmentioning

confidence: 99%

Heat Stress Induces an Aggregation of the Light-Harvesting Complex of Photosystem II in Spinach Plants

et al. 2006

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Whole spinach (Spinacia oleracea) plants were subjected to heat stress (25°C-50°C) in the dark for 30 min. At temperatures higher than 35°C, CO 2 assimilation rate decreased significantly. The maximal efficiency of photosystem II (PSII) photochemistry remained unchanged until 45°C and decreased only slightly at 50°C. Nonphotochemical quenching increased significantly either in the absence or presence of dithiothreitol. There was an appearance of the characteristic band at around 698 nm in 77 K fluorescence emission spectra of leaves. Native green gel of thylakoid membranes isolated immediately from heat-stressed leaves showed that many pigment-protein complexes remained aggregated in the stacking gel. The analyses of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting demonstrated that the aggregates were composed of the main light-harvesting complex of PSII (LHCIIb). To characterize the aggregates, isolated PSII core complexes were incubated at 25°C to 50°C in the dark for 10 min. At temperatures over 35°C, many pigment-protein complexes remained aggregated in the stacking gel of native green gel, and immunoblotting analyses showed that the aggregates were composed of LHCIIb. In addition, isolated LHCII was also incubated at 25°C to 50°C in the dark for 10 min. LHCII remained aggregated in the stacking gel of native green gel at temperatures over 35°C. Massive aggregation of LHCII was clearly observed by using microscope images, which was accompanied by a significant increase in fluorescence quenching. There was a linear relationship between the formation of LHCII aggregates and nonphotochemical quenching in vivo. The results in this study suggest that LHCII aggregates may represent a protective mechanism to dissipate excess excitation energy in heat-stressed plants.

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“…These preparations lacked PS I as well as the cytochrome b6-fcomplex, and a variable portion of cytochrome 6-559 (which amounted to about two molecules per reaction center) was found to be present in both its HP and LP states. However, a careful examination of the redox and acid/base properties of cytochrome b-559 and of its photochemical performance in these PS I1 particles has not yet been reported [25,26,[36][37][38][39][40][41][42]. To the best of our knowledge there is only a brief mention by Lam et al [39] that some photo-oxidation of cytochrome b-559 is observed and by Ghanotakis et al [42] that no lightinduced changes are seen.…”

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confidence: 99%

Redox and acid‐base characterization of cytochrome b‐559 in photosystem II particles

Ortega

Hervás

Losada

1988

European Journal of Biochemistry

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The redox and acidlbase states and midpoint potentials of cytochrome b-559 have been determined in oxygenevolving photosystem I1 (PS 11) particles at room temperature in the pH range from 6.5 to 8.5. At pH 7.5 the fresh PS I1 particles present about 213 of their cytochrome b-559 in its reduced and protonated (non-autooxidizable) high-potential form and about 1/3 in its oxidized and non-protonated low-potential form. Potentiometric reductive titration shows that the protonated high-potential couple is pH-independent (Eo, + 380 mV), whereas the low-potential couple is non-protonated and pH-independent above pH 7.6 (Eo, pH > 7.6, + 140 mV), but becomes pH-dependent below this pH, with a slope of -72 mV/pH unit. Moreover, evidence is presented that in PS I1 particles cytochrome b-559 can cycle, according to its established redox and acidlbase properties, as an energy transducer at two alternate midpoint potentials and at two alternate pKa values. Red light absorbed by PS I1 induces reduction of cytochrome b-559 in these particles at room temperature, the reaction being completely blocked by dichlorophenyldimethylurea.The location and function of cytochrome b-559 in the chloroplast electron-transport chain(s), although widely and intensively investigated, have remained enigmatic and controversial [l -81. Understanding the oxidation/reduction potential and pH dependence of this cytochrome in high-potential (HP) low-potential (LP) forms is essential for assessing its role as both an electron carrier and a proton carrier, but in this regard the literature is ambiguous and includes incomplete and contradictory data. Equally important is deciding whether cytochrome b-559 is reduced or oxidized by light absorbed by photosystem 11, since the reported results are also contradictory in this respect. [15] this effect, which is reversible upon raising the pH, is inhibited by 3-(3',4'-dichloropheny1)-1,l'-dimethylurea (+ 395 mV at pH 7.8; + 335 mV at pH 5.0, and + 380 mV at pH 5.0 and in the presence of dichlorophenyldimethylurea). More recently our group [19 -211 obtained solid evidence that in spinach thylakoids the HP couple of cytochrome b-559 is pH-independent in the pH range between 6.5 and 8.5 (Eb, + 340 mV), whereas the LP couple is pH-independent above pH 7.6 (Eo, pH > 7.6, + 75 mV), but becomes pH-dependent below this pH, with a slope of -60 mV/pH unit. According to our proposal [6,21] the cytochrome functions at low potential as electron acceptor of PS 11, and at high potential as electron donor to PS I, thus acting as a transducer of redox energy into acidlbase energy between the two photosystems.The HP form of cytochrome b-559 is labile towards treatments, such as aging, sonication, mild heating, incubation in Tris buffer or Triton X-100, addition of either carbonylcyanide p-trifluoromethoxyphenylhydrazone or carbonylcyanide 3-chlorophenylhydrazone (CCCP), trypsin digestion, NaCl washing, that may alter or disrupt membrane structure and that cause what is usually considered an 'irreversible' conversion to the LP fo...

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Structural and catalytic properties of the oxygen-evolving complex. Correlation of polypeptide and manganese release with the behavior of Z+ in chloroplasts and a highly resolved preparation of the PS II complex

Cited by 159 publications

References 25 publications

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

Heat Stress Induces an Aggregation of the Light-Harvesting Complex of Photosystem II in Spinach Plants

Redox and acid‐base characterization of cytochrome b‐559 in photosystem II particles

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Structural and catalytic properties of the oxygen-evolving complex. Correlation of polypeptide and manganese release with the behavior of Z+ in chloroplasts and a highly resolved preparation of the PS II complex

Cited by 159 publications

References 25 publications

Spectroscopic Evidence for Ca2+Involvement in the Assembly of the Mn4Ca Cluster in the Photosynthetic Water-Oxidizing Complex

Spectroscopic Evidence for Ca2+Involvement in the Assembly of the Mn4Ca Cluster in the Photosynthetic Water-Oxidizing Complex

Heat Stress Induces an Aggregation of the Light-Harvesting Complex of Photosystem II in Spinach Plants

Redox and acid‐base characterization of cytochrome b‐559 in photosystem II particles

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Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex