Stabilization of the oxygen-evolving complex of photosystem II by�bicarbonate and glycinebetaine in thylakoid and subthylakoid�preparations (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1984
Four procedures utilizing different detergent and salt conditions were used to isolate oxygen-evolving Photosystem II (PS II) preparations from spinach thylakoid membranes. These PS II preparations have been characterized by freeze-fracture electron microscopy, SDS-polyacrylamide gel electrophoresis, steady-state and pulsed oxygen evolution, 77 K fluorescence, and room-temperature electron paramagnetic resonance. All of the O2-evoiving PS II samples were found to be highly purified grana membrane fractions composed of paired, appressed membrane fragments. The lumenal surfaces of the membranes and thus the O2-evoiving enzyme complex, are directly exposed to the external environment. Biochemical and biophysical analyses indicated that all four preparations are enriched in the chlorophyll a/b-light-harvesting complex and Photosystem I1, and depleted to varying degrees in the stroma-associated components, Photosystem I and the CFI-ATPase. The four PS II samples also varied in their cytochrome f content. All preparations showed enhanced stability of oxygen production and oxygen-rate electrode activitY compared to control thylakoids, apparently promoted by low concentrations of residual detergent in the PS II preparations. A model is presented which summarizes the effects of the salt and detergent treatments on thylakoid structure and, consequently, on the configuration and composition of the oxygen-evolving PS II samples.
Biochemistry, 1997
The characteristic period four oscillation patterns of oxygen evolution induced by a train of single-turnover flashes were measured as a function of temperature in dark-adapted photosystem II (PS II) membrane fragments that were reconstituted with native plastoquinone-9 (PQ-9) by a recently developed procedure [Kurreck, J., Seeliger, A. G., Reifarth, F., Karge, M., & Renger, G. (1995) Biochemistry 34, 15721-15731]. The following results were obtained: (a) within the range 0-35°C, the probabilities of misses (R) and double-hits ( ) and the dark population of redox state S 1 exhibit similar dependencies on the temperature; (b) below a characteristic temperature ϑ c these parameters remain virtually independent of temperature, above ϑ c (ϑ c ) 20°C for R and ; ϑ c ) 30°C for S 1 ) the values of R and increase whereas S 1 decreases; and (c) the dark decay of S 2 and S 3 via fast and slow kinetics owing to reduction of the water oxidase by Y D and other endogenous electron donor(s), respectively, exhibits comparatively strong temperature dependencies with the following activation energies: E A (S 2 fast ) ) 60 ( 10 kJ/mol, E A (S 3 fast ) ) 55 ( 10 kJ/mol, E A (S 2 slow ) ) 80 ( 5 kJ/mol, and E A (S 3 slow ) ) 75 ( 5 kJ/mol. These values of PQ-9 reconstituted PS II membrane fragments are very similar to those that were previously reported for thylakoids [Messinger, J., Schröder, W. P., & Renger, G. (1993) Biochemistry 32, 7658-7668]. These findings reveal that the reaction coordinates of feeding electrons by endogenous electron donors into the water oxidizing complex (WOC) that attains the redox states S 2 and S 3 is virtually invariant to Triton X-100 treatment used in the isolation procedure of PS II membrane fragments from thylakoids. Implications of these findings are discussed.
Biologia Plantarum, 2011
The effects of temperature (25-45 °C) and pH (7.5-5.5) on photosystem (PS) 2 was studied in spinach (Spinacia oleracea L.) thylakoid membranes using chlorophyll a fluorescence induction kinetics. In high temperature and low pH treated thylakoid membranes a decline in the variable to maximum fluorescence ratio (F v /F m) and PS 2 electron transport rate were observed. More stacking in thylakoid membranes, studied by digitonin fractionation method, was observed at low pH, while the degree of unstacking increased under high temperature conditions. We conclude that the change in pH does not significantly affect the donor/acceptor side of PS 2 while high temperature does. Fluorescence emission spectra at 77 K indicated that low pH is associated with energy redistribution between the two photosystems while high temperature induced changes do not involve energy redistribution. We suggest that both, high temperature and low pH, show an inhibitory effect on PS 2 but their mechanisms of action are different.
Oxygen-evolution patterns from spinach Photosystem II preparations
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1983
Patterns of O 2 evolution resulting from sequences of short flashes are reported for Photosystem (PS) II preparations isolated from spinach and containing an active, O2-evolving system. The results can be interpreted in terms of the S-state model developed to explain the process of photosynthetic water splitting in chloroplasts and algae. The PS II samples display damped, oscillating patterns of 02 evolution with a period of four flashes. Unlike chloroplasts, the flash yields of the preparations decay with increasing flash number due to the limited plastoquinone acceptor pool on the reducing side of PS II. The optimal pH for 0 2 evolution in this system (pH 5.5-6.5) is more acidic than in chloroplasts (pH 6.5-8.0). The O2-evolution , inactivation half-time of dark-adapted preparations was 91 min (on the rate electrode) at room temperature. Dark-inactivation half-times of 14 h were observed ff the samples were aged off the electrode at room temperature. Under our conditions (experimental conditions can influence flash-sequence results), deactivation of S 3 was first order with a half-time of 105 s while that of S 2 was biphasic. The half-times for the first-order rapid phase were 17 s (one preflash) and 23 s (two preflashes). The longer S 2 phase deactivated very slowly (the minimum half-time observed was 265 s). These results indicate that deactivation from S 3-, S 2 ~ St, thought to be the dominant pathway in chloroplasts, is not the case for PS II preparations. Finally, it was demonstrated that the ratio of S~ to S o can be set by previously developed techniques, that S o is formed mostly from activated S 3 ($4), and that both S o and S t are stable in the dark.
Carlsberg Research Communications, 1982
Purified inside-out photosystem II vesicles with retained capacity for oxygen evolution and a simple polypeptide composition were found to be more sensitive to washing with tris(hydroxymethyl)aminomethane (Tris) at alkaline pH than right-side out thylakoids. This suggests that the thylakoid membrane limits the penetration of the active unprotonated form of Tris. The inhibition of photosynthetic oxygen evolution by alkaline Tris-washing (pH 8.5) coincided with the release of a polypeptide with a molecular weight of 32,000 from the inside-out vesicles. Only this polypeptide was released with concentrations of Tris up to 200 mM, while higher concentrations removed additional polypeptides with a molecular weight of 34,000 and 56,000. About 70 96 of the membrane bound manganese is lost by washing the vesicles with 200 mM-Tris. Oxygen evolution was not inhibited nor were polypeptides released with Tris buffered at pH 6.5. From right-side out thylakoids the 32,000 molecular weight polypeptide could not be extracted into the ambient medium by Tris-washing. Restoration of oxygen evolution of Tris-inactivated inside-out and right-side out vesicles was possible with the aid of reduced dichlorophenol indophenol but without the addition of the 32,000 molecular weight polypeptide or manganese.
Physiologia Plantarum, 1999
Depletion of bicarbonate (carbon dioxide) from oxygenic cells reaction center subunits of photosystem II, as well as to form ligands to the non-heme iron between the D1 and D2 proteins. or organelles not only causes cessation of carbon dioxide fixation, but also a strong decrease in the activity of photosys-Bicarbonate, at physiological pH, has an important role in the tem II; the photosystem II activity can be restored by readdi-water-plastoquinone oxido-reductase: on the one hand it may tion of bicarbonate. Effects of bicarbonate exist on both the stabilize, by conformational means, the reaction center protein acceptor as well as on the donor side of photosystem II. The of photosystem II that allows efficient electron flow and protonation of certain amino acids near the secondary quinone influence on the acceptor side is located between the primary electron acceptor of photosystem II; and, on the other hand, it and secondary quinone electron acceptor of photosystem II, appears to play a significant role in the assembly or function-and can be demonstrated in intact cells or leaves as well as in ing of the manganese complex at the donor side. Functional isolated thylakoids and reaction center preparations. At physroles of bicarbonate in vivo, including protection against iological pH, bicarbonate ions are suggested to form hydrogen bonds to several amino acids on both D1 and D2 proteins, the photoinhibition, are also discussed.
Biochemistry, 2007
A mild sonication and phase fractionation method has been used to isolate five regions of the thylakoid membrane in order to characterize the functional lateral heterogeneity of photosynthetic reaction centers and light harvesting complexes. Low-temperature fluorescence and absorbance spectra, absorbance cross-section measurements, and picosecond time-resolved fluorescence decay kinetics were used to determine the relative amounts of photosystem II (PSII) and photosystem I (PSI), to determine the relative PSII antenna size, and to characterize the excited-state dynamics of PSI and PSII in each fraction. Marked progressive increases in the proportion of PSI complexes were observed in the following sequence: grana core (BS), whole grana (B3), margins (MA), stroma lamellae (T3), and purified stromal fraction (Y100). PSII antenna size was drastically reduced in the margins of the grana stack and stroma lamellae fractions as compared to the grana. Picosecond time-resolved fluorescence decay kinetics of PSII were characterized by three exponential decay components in the grana fractions, and were found to have only two decay components with slower lifetimes in the stroma. Results are discussed in the framework of existing models of chloroplast thylakoid membrane lateral heterogeneity and the PSII repair cycle. Kinetic modeling of the PSII fluorescence decay kinetics revealed that PSII populations in the stroma and grana margin fractions possess much slower primary charge separation rates and decreased photosynthetic efficiency when compared to PSII populations in the grana stack. 905 688-1855. Phone: 905 688-5550 ext 3826. ‡ Brock University. § Uppsala University. 1 Abbreviations: PS, photosystem; RC, reaction center; Chl, chlorophyll; P680, primary electron donor in photosystem II; Q A , primary quinone electron acceptor in photosystem II; DAS, decay-associated spectrum; F 0, the minimal fluorescence level associated with photochemically active or "open" reaction centers with an oxidized primary quinone electron acceptor, QA; FM, the maximal level of fluorescence associated with photochemically inactive or "closed" reaction centers with reduced primary quinone electron acceptor, Q A .