A Time-Resolved FTIR Difference Study of the Plastoquinone Q<sub>A</sub> and Redox-Active Tyrosine Y<sub>Z</sub> Interactions in Photosystem II

Zhang, H; Razeghifard, M. Reza; Fischer, Gad; Wydrzynski, Tom

doi:10.1021/bi970815t

Cited by 48 publications

(85 citation statements)

References 29 publications

(40 reference statements)

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“…• (near P D2 ) both lead to a small spectral response at Ϸ1,704 cm Ϫ1 (42)(43)(44)(45). This analysis seems a likely interpretation because the cation state is localized mainly on P D1 (9), and the 1,704 cm Ϫ1 band has the largest amplitude in the P ϩ ͞P spectrum.…”

Section: Population Of H D1mentioning

confidence: 84%

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Groot

Pawlowicz

Wilderen

et al. 2005

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

202

258

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Despite the apparent similarity between the plant Photosystem II reaction center (RC) and its purple bacterial counterpart, we show in this work that the mechanism of charge separation is very different for the two photosynthetic RCs. By using femtosecond visible-pump-mid-infrared probe spectroscopy in the region of the chlorophyll ester and keto modes, between 1,775 and 1,585 cm ؊1 , with 150-fs time resolution, we show that the reduction of pheophytin occurs on a 0.6-to 0.8-ps time scale, whereas P ؉ , the precursor state for water oxidation, is formed after Ϸ6 ps. We conclude therefore that in the Photosystem II RC the primary charge separation occurs between the ''accessory chlorophyll'' ChlD1 and the pheophytin on the so-called active branch.electron transfer ͉ photosynthesis ͉ pump-probe T he primary steps of energy and electron transfer in green plants' photosynthesis occur in two large protein complexes called Photosystem I and Photosystem II (PSII). PSII is an aggregate of many individual pigment-protein complexes. The core of PSII consists of the chlorophyll (Chl)-binding antennaproteins CP43 and CP47, which feed excitation energy into the D 1 D 2 cytb559 reaction center (RC). Crystal structures of PSII cores from cyanobacteria have been resolved with increasingly high resolution (1-3); currently, the resolution is 3.2 Å (4). The structure of the PSII RC shows four Chls and two pheophytins (H) arranged in two branches very similar to the bacterial RC. In the heart of the PSII RC, there is a dimer of Chls, and in each branch there is one monomeric Chl and one H. Furthermore, there are two distant Chls bound to the periphery of the PSII RC. Although the structure suggests there may be a ''special pair'' of strongly electronically coupled pigments in the PSII RC, the visible absorption spectrum does not show a distinct band. This finding is in contrast to the bacterial RC, where the lowest energy absorption band fully originates from one of the exciton transitions of a special pair of bacteriochlorophylls.Since the first purification of the PSII RC in 1987 (5), it has been speculated that its way of operation would be similar to that of the bacterial RC, with a special pair that upon excitation drives a charge separation in Ϸ3 ps. This idea was based on the strong homology between the bacterial RC and the PSII RC, the strong similarity in the pigment composition, even details in the way the pigments interacted with the protein, and the near-identity of the electron transfer events at the acceptor side. Conversely, it was clear that major differences between the two RCs had to exist at the electron donor side where in the PSII RC charge separation eventually leads to the oxidation of water and the production of molecular oxygen, requiring a very large oxidation potential of the primary electron donor (Ͼ1.2 V vs. 0.45 V in the bacterial RC).In the mid-1990s, it was recognized that energy transfer and charge separation in the PSII RC most likely proceeded in a manner that is very different from that in the b...

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Section: Population Of H D1mentioning

confidence: 84%

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Groot

Pawlowicz

Wilderen

et al. 2005

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

202

258

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“…The Flash-Induced Formation of Y D • at 250 K. The lightminus-dark FTIR difference spectrum of the unlabeled Mndepleted wild-type* PSII particles (Figure 4) does not resemble the spectra of Chl Z • -minus-Chl Z (98), Car • -minusCar (99), Y Z • -minus-Y Z (100), or Q A •--minus-Q A (74,(101)(102)(103)(104). But then, neither Chl Z • nor Car • would be expected to form at 250 K (105-107) and the 10 s delay between the laser flash and the commencement of data acquisition should have been sufficient for the decay of Y Z • and Q A •- (44,63,64).…”

Section: Discussionmentioning

confidence: 98%

Evidence that the C-Terminus of the D1 Polypeptide of Photosystem II is Ligated to the Manganese Ion that Undergoes Oxidation During the S₁to S₂Transition: An Isotope-Edited FTIR Study

2004

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Isotope-edited FTIR difference spectroscopy was employed to determine if the C-terminal alpha-COO(-) group of the D1 polypeptide ligates the (Mn)(4) cluster in photosystem II (PSII) and, if so, if it ligates the Mn ion that undergoes an oxidation during the S(1) --> S(2) transition. Wild-type and mutant cells of the cyanobacterium Synechocystis sp. PCC 6803 were propagated photoautotrophically in the presence of L-[1-(13)C]alanine or unlabeled ((12)C) L-alanine. In wild-type cells, both the C-terminal alpha-COO(-) group of the D1 polypeptide at D1-Ala344 and all alanine-derived peptide carbonyl groups will be labeled. In D1-A344G and D1-A344S mutant cells, the C-terminal alpha-COO(-) group of the D1 polypeptide will not be labeled because this group is no longer provided by alanine. The resultant S(2)-minus-S(1) FTIR difference spectra of purified wild-type and mutant PSII particles showed that one symmetric carboxylate stretching mode that is altered during the S(1) --> S(2) transition is sensitive to L-[1-(13)C]alanine-labeling in wild-type PSII particles but not in D1-A344G and D1-A344S PSII particles. Because the only carboxylate group that can be labeled in the wild-type PSII particles but not in the mutant PSII particles is the C-terminal alpha-COO(-) group of the D1 polypeptide, we assign the L-[1-(13)C]alanine-sensitive symmetric carboxylate stretching mode to the alpha-COO(-) group of D1-Ala344. In unlabeled wild-type PSII particles, this mode appears at approximately 1356 cm(-1) in the S(1) state and at approximately 1339 or approximately 1320 cm(-1) in the S(2) state. These frequencies are consistent with unidentate ligation of the (Mn)(4) cluster by the alpha-COO(-) group of D1-Ala344 in both the S(1) and S(2) states. The apparent 17-36 cm(-1) downshift in frequency in response to the S(1) --> S(2) transition is consistent with the alpha-COO(-) group of D1-Ala344 ligating a Mn ion whose charge increases during the S(1) --> S(2) transition. Accordingly, we propose that the alpha-COO(-) group of D1-Ala344 ligates the Mn ion that undergoes an oxidation during the S(1) --> S(2) transition. Control experiments were conducted with Mn-depleted wild-type PSII particles. These experiments showed that tyrosine Y(D) may be structurally coupled to the carbonyl oxygen of an alanine-derived peptide carbonyl group.

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“…While the interpretation of these band shifts remains controversial (electrochromism (51,67,68) versus proton displacement within a hydrogen bond (69)), there is no disagreement as to their arising from one or more of the reaction center chlorophylls. These are likely the electronic counterparts of differences observed in the vibrational spectra for Y Z •-Y Z (70,71) and Y D •-Y D (72), attributed to the keto C 9 dO groups of P.…”

Section: Site-directed Mutationsmentioning

confidence: 93%

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

et al. 2001

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Site-directed mutations were introduced to replace D1-His198 and D2-His197 of the D1 and D2 polypeptides, respectively, of the photosystem II (PSII) reaction center of Synechocystis PCC 6803. These residues coordinate chlorophylls P A and P B which are homologous to the special pair Bchlorophylls of the bacterial reaction centers that are coordinated respectively by histidines L-173 and M-200 (202). P A and P B together serve as the primary electron donor, P, in purple bacterial reaction centers. In PS II, the site-directed mutations at D1 His198 affect the P + -P-absorbance difference spectrum. The bleaching maximum in the Soret region (in WT at 433 nm) is blue-shifted by as much as 3 nm. In the D1 His198Gln mutant, a similar displacement to the blue is observed for the bleaching maximum in the Q y region (672.5 nm in WT at 80 K), whereas features attributed to a band shift centered at 681 nm are not altered. In the Y Z •-Y Z -difference spectrum, the band shift of a reaction center chlorophyll centered in WT at 433-434 nm is shifted by 2-3 nm to the blue in the D1-His198Gln mutant. The D1-His198Gln mutation has little effect on the optical difference spectrum, 3 P-1 P, of the reaction center triplet formed by P + Pheo -charge recombination (bleaching at 681-684 nm), measured at 5-80 K, but becomes visible as a pronounced shoulder at 669 nm at temperatures g150 K. Measurements of the kinetics of oxidized donor-Q A -charge recombination and of the reduction of P + by redox active tyrosine, Y Z , indicate that the reduction potential of the redox couple P + /P can be appreciably modulated both positively and negatively by ligand replacement at D1-198 but somewhat less so at D2-197. On the basis of these observations and others in the literature, we propose that the monomeric accessory chlorophyll, B A , is a long-wavelength trap located at 684 nm at 5 K. B A * initiates primary charge separation at low temperature, a function that is increasingly shared with P A * in an activated process as the temperature rises. Charge separation from B A * would be potentially very fast and form P A + B A -and/or B A + Pheo -as observed in bacterial reaction centers upon direct excitation of B A ) Proc. Natl. Acad Sci. 96, 2054-2059. The cation, generated upon primary charge separation in PSII, is stabilized at all temperatures primarily on P A , the absorbance spectrum of which is displaced to the blue by the mutations. In WT, the cation is proposed to be shared to a minor extent (∼20%) with P B , the contribution of which can be modulated up or down by mutation. The band shift at 681 nm, observed in the P + -P difference spectrum, is attributed to an electrochromic effect of P A + on neighboring B A . Because of its low-energy singlet and therefore triplet state, the reaction center triplet state is stabilized on B A at e80 K but can be shared with P A at >80 K in a thermally activated process.

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A Time-Resolved FTIR Difference Study of the Plastoquinone Q_A and Redox-Active Tyrosine Y_Z Interactions in Photosystem II

Cited by 48 publications

References 29 publications

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Evidence that the C-Terminus of the D1 Polypeptide of Photosystem II is Ligated to the Manganese Ion that Undergoes Oxidation During the S₁to S₂Transition: An Isotope-Edited FTIR Study

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

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A Time-Resolved FTIR Difference Study of the Plastoquinone QA and Redox-Active Tyrosine YZ Interactions in Photosystem II

Cited by 48 publications

References 29 publications

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Evidence that the C-Terminus of the D1 Polypeptide of Photosystem II is Ligated to the Manganese Ion that Undergoes Oxidation During the S1to S2Transition: An Isotope-Edited FTIR Study

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

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A Time-Resolved FTIR Difference Study of the Plastoquinone Q_A and Redox-Active Tyrosine Y_Z Interactions in Photosystem II

Evidence that the C-Terminus of the D1 Polypeptide of Photosystem II is Ligated to the Manganese Ion that Undergoes Oxidation During the S₁to S₂Transition: An Isotope-Edited FTIR Study