Assignment of the Q<i><sub>y</sub></i> Absorbance Bands of Photosystem II Chromophores by Low-Temperature Optical Spectroscopy of Wild-Type and Mutant Reaction Centers

Stewart, David; Nixon, Peter J.; Diner, Bruce A.; Brudvig, Gary W.

doi:10.1021/bi001246j

Cited by 37 publications

(60 citation statements)

References 53 publications

(112 reference statements)

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“…The long-wavelength assignment for B A is also consistent with low-temperature electrochromic band shifts observed upon reduction of Q A (64). As the ordering of the triplet state energies is parallel to that of the singlet states (99), it is clear that at low temperature the triplet excitation will reside on B A , regardless of where the triplet were generated.…”

Section: Location Of 3 P As a Function Of Temperaturesupporting

confidence: 71%

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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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Section: Location Of 3 P As a Function Of Temperaturesupporting

confidence: 71%

“…The spectrum of Q A --Q A in the Q y region was examined in these complexes in Stewart et al (64). The contribution of this difference spectrum to that of P + Q A --PQ A is approximately 1% between 660 and 680 nm and 5% between 680 and 690 nm.…”

Section: Site-directed Mutationsmentioning

confidence: 99%

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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“…At low temperature, accessory Chl D has its lowest energy absorption (Q y ) at ~682-664 nm (Konermann and Holzwarth, 1996;Stewart et al, 2000), while the Q y band of the P D1 , P D2 pair lies a little higher (~679-680 nm; Braun et al, 1990;Konermann and Holzwarth, 1996). This is consistent with the discovery that Chl D1 is the the primary electron donor of P680 and P D1 the secondary (Diner et al, 2001;Holzwarth et al, 2006).…”

Section: Core Complexessupporting

confidence: 74%

“…Discrepant results have been published for the reduced Pheo at low temperature. Thus Pheo D1 has been assigned Q y maxima at ~670-672 (Braun et al, 1990;Konermann and Holzwarth, 1996;Tomo et al, 2008), and at ~681-685 nm (Stewart et al, 2000).…”

Section: Core Complexesmentioning

confidence: 99%

Fluorescence Emission from the Photosynthetic Apparatus

Papageorgiou

2011

Photosynthesis

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“…6803 PS II core complexes. Mutations of the amino acids located around Pheo D1 (Stewart et al 2000) were shown to induce strong influences on the Q A -electrochromic shifts in both Q x and Q y . Mutations around Chl D1 were shown to shift the triplet bleach ) but induce little changes in Q x electrochromism.…”

Section: Photo-reduction Of Pheo D1 At Ambient Temperaturesmentioning

confidence: 99%

Spectral characteristics of PS II reaction centres: as isolated preparations and when integral to PS II core complexes

2008

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The discovery that the native PS II enzyme undergoes charge separation via an absorption extending to 730 nm has led us to re-examine the low-temperature absorption spectra of Nanba-Satoh PS II reaction centre preparations with particular focus on the long wavelength region. It is shown that these preparations do not exhibit absorption in the 700-730 nm region at 1.7 K. Absorption in the Nanba-Satoh type preparations analogous to the 'red tail' as observed in functional PS II core complexes is likely shifted to higher energy by >20 nm. Spectral changes associated with the stable reduction of pheo(a) in chemically treated reaction centre preparations are also revisited. Dithionite treatment of PS II preparations in the dark leads to changes of pigment-pigment and/or pigment-protein interactions, as evidenced by changes in absorption and CD spectra. Absorption and CD changes associated with stable Pheo(D1) photo-reduction in PS II core complexes and Nanba-Satoh preparations are compared. For Nanba-Satoh preparations, Q(y) bleaches are approximately 3x broader than in PS II core complexes and are blue-shifted by approximately 4 nm. These data are discussed in terms of current models of PS II, and suggest a need to consider protein-induced changes of some electronic properties of reaction centre pigments.

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Assignment of the Q_y Absorbance Bands of Photosystem II Chromophores by Low-Temperature Optical Spectroscopy of Wild-Type and Mutant Reaction Centers

Cited by 37 publications

References 53 publications

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

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

Fluorescence Emission from the Photosynthetic Apparatus

Spectral characteristics of PS II reaction centres: as isolated preparations and when integral to PS II core complexes

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Assignment of the Qy Absorbance Bands of Photosystem II Chromophores by Low-Temperature Optical Spectroscopy of Wild-Type and Mutant Reaction Centers

Cited by 37 publications

References 53 publications

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

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

Fluorescence Emission from the Photosynthetic Apparatus

Spectral characteristics of PS II reaction centres: as isolated preparations and when integral to PS II core complexes

Contact Info

Product

Resources

About

Assignment of the Q_y Absorbance Bands of Photosystem II Chromophores by Low-Temperature Optical Spectroscopy of Wild-Type and Mutant Reaction Centers