Similarity of EPR Signal IIf rise and P-680+ decay kinetics in Tris-washed chloroplast Photosystem II preparations as a function of pH

Photosynthetic oxygen production by photosystem II (PSII) is responsible for the maintenance of aerobic life on earth. The production of oxygen occurs at the PSII oxygen-evolving complex (OEC), which contains a tetranuclear manganese (Mn) cluster. Photo-induced electron transfer events in the reaction center lead to the accumulation of oxidizing equivalents on the OEC. Four sequential photooxidation reactions are required for oxygen production. The oxidizing complex cycles among five oxidation states, called the S n states, where n refers to the number of oxidizing equivalents stored. Oxygen release occurs during the S 3-to-S0 transition from an unstable intermediate, known as the S4 state. In this report, we present data providing evidence for the production of an intermediate during each S state transition. These proteinderived intermediates are produced on the microsecond to millisecond time scale and are detected by time-resolved vibrational spectroscopy on the microsecond time scale. Our results suggest that a protein-derived conformational change or proton transfer reaction precedes Mn redox reactions during the S 2-to-S3 and S 3-to-S0 transitions.manganese cluster ͉ photosynthesis ͉ photosystem II ͉ time-resolved IR ͉ water oxidation T ime-resolved vibrational spectroscopy can detect chemical intermediates formed during enzymatic catalysis. Advantages include the technique's exquisite structural sensitivity and its high temporal resolution. Recent advances in methodology and interpretation have produced insights into the catalytic mechanism in several biological systems (for examples, see refs. 1-4).In this paper, we report the use of time-resolved IR spectroscopy to investigate the mechanism of photosynthetic water oxidation. Photosystem II (PSII) catalyzes the oxidation of water and the reduction of bound plastoquinone. Photoexcitation of PSII leads to the oxidation of the chlorophyll donor, P 680 , and the sequential reduction of a pheophytin (Fig. 1A, reaction 1) and a plastoquinone, Q A ( Fig. 1 A, reaction 2), in picoseconds. Q A reduces Q B to generate a semiquinone radical, Q B Ϫ , on the microsecond time scale (Fig. 1 A, reaction 3 ) (reviewed in ref. 5).A second photoexcitation leads to the reduction and protonation of Q B Ϫ to form the quinol Q B H 2 . The rate of reduction of Q B is faster than the rate of reduction of Q B Ϫ (see ref. 6 and references therein), which gives rise to a characteristic period-2 oscillation in kinetics originating on the PSII acceptor side (7).The primary chlorophyll donor, P 680 , oxidizes a tyrosine, Y Z (Y161 in the D1 subunit), on the nanosecond to microsecond time scale (Fig. 1 A, reaction 4). In turn, tyrosine Y Z ⅐ oxidizes the oxygen-evolving complex (OEC) on every flash (Fig. 1 A, reaction 5) (8). Four sequential photooxidation reactions are required for oxygen production, and the oxidizing complex cycles among five oxidation states, called the S n states, where n refers to the number of oxidizing equivalents stored (9). The rate of OEC oxidation slows as o...

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“…1 A is blocked. In this sample, Y Z reduces P 680 ϩ with a lifetime in the microsecond time domain (25,26). The blue trace in Fig.…”

Section: Resultsmentioning

confidence: 86%

“…2, blue trace). In this sample, the OEC is inactivated with 1.8 M alkaline Tris (24), Y Z is the terminal electron donor (25,26), and reaction 5 in Fig. 1 A is blocked.…”

Section: Resultsmentioning

confidence: 99%

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Barry

Cooper²,

Riso³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…It was interpreted to be a tightly bound plastoquinone molecule [13]. From the coinciding kinetics of the reduction of Chl-aIt and the oxidation of Z, respectively, it has been concluded that Z is the immediate donor to Chl-aIt in PS II inactive in oxygen evolution [12,14].…”

Section: Abbreviationsmentioning

confidence: 99%

Direct observation of the immediate electron donor to chlorophyll‐a⁺_II (P‐680⁺) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV

et al. 1987

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Flash-induced absorption changes in the UV have been monitored with nanosecond time resolution in oxygen-evolving photosystem II complexes from Synechococcus sp. At 260 nm, the oxidation of the immediate donor to Chl-a: (P-680+) in the l&500 ns range could be observed directly. The difference extinction coefficient for its oxidation is estimated to be 6000-8000 M-l .cm-' at 260 nm. The observed kinetics for the oxidation of the donor is identical with the reduction kinetics of Chl-a: as monitored at 824 nm. At 320 nm, the reduction of QA was found to be faster than 1 ns.

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“…Tris-inactivation of chloroplasts reduced the decay speed of flash-induced signals of P680 + [7~77], D1 + [78] and Z + [61,[79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] from nsec to 2-200 usec range. Slowing of these signal decays was useful to detect and analyze the primary photochemical reactions of PS ~.…”

Section: Iu Photooxidation and Dark-reduction Of P680 And Zmentioning

confidence: 99%

“…effect of chloroplast Mn on the protonspin4attice relaxation rate [67][68][69], (F). signals of light-induced oxidation and reduction of P680 [70][71][72][73][74][75][76][77], D 1 [78], Z [61,[79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96], C550 [28,[111][112], cytochrome b559 [28,31,[111][112][113][114], X320 [i15], X591 [28], A475 [46], A515 [46, 72, i07] and A520 [ii6], (G). peptides of 02-evolving center [6, 17, 97-i03], (H).…”

Section: Introductionmentioning

confidence: 99%

Modification of oxygen evolving center by Tris-washing

Yamashita

1986

Photosynth Res

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Tris-washing inhibits the O2-evolving center of chloroplasts and their particles specifically and reversibly, and it was applied to many investigations on O2-evolving center and PS II reaction center. In this review are introduced the various photosynthetic investigations in which Tris-washing was applied and are also discussed briefly on the site and the mechanism of Tris-inactivation, properties of P680 and Z, characteristic change in fluorescence and delayed light emission, and reactivation of O2-evolving center by DCPIP.H2-treatment and photo-reactivation of Tris-washed chloroplasts and their particles.

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Similarity of EPR Signal IIf rise and P-680+ decay kinetics in Tris-washed chloroplast Photosystem II preparations as a function of pH

Cited by 79 publications

References 19 publications

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Direct observation of the immediate electron donor to chlorophyll‐a⁺_II (P‐680⁺) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV

Modification of oxygen evolving center by Tris-washing

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Similarity of EPR Signal IIf rise and P-680+ decay kinetics in Tris-washed chloroplast Photosystem II preparations as a function of pH

Cited by 79 publications

References 19 publications

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Direct observation of the immediate electron donor to chlorophyll‐a+II (P‐680+) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV

Modification of oxygen evolving center by Tris-washing

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Direct observation of the immediate electron donor to chlorophyll‐a⁺_II (P‐680⁺) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV