The Native Reaction Centre of Photosystem II: A New Paradigm for P680

Hughes, Joseph L.; Prince, Barry J.; Årsköld, Sindra Peterson; Smith, Paul J.; Pace, Ronald; Riesen, Hans; Krausz, Elmars

doi:10.1071/ch04140

Cited by 11 publications

(24 citation statements)

References 25 publications

(52 reference statements)

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“…This work has indicated that the D1/D2/cytb 559 sub-assembly is both spectrally shifted and significantly inhomogeneously broadened compared to the properties of the equivalent native assembly. 38,39 By contrast, key spectral features in core complexes, membrane-bound PSII 26,27,40 and even thylakoid preparations (unpublished results) show the same positions, widths and intensities. It is only in the last solubilisation step, with removal of CP43 and CP47, that the reaction centre becomes severely affected.…”

Section: Psii Sub-assembliesmentioning

confidence: 93%

Oxygen-evolving Photosystem II core complexes: a new paradigm based on the spectral identification of the charge-separating state, the primary acceptor and assignment of low-temperature fluorescence

Krausz

Hughes

Smith

et al. 2005

Photochem Photobiol Sci

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We review our recent low-temperature absorption, circular dichroism (CD), magnetic CD (MCD), fluorescence and laser-selective measurements of oxygen-evolving Photosystem II (PSII) core complexes and their constituent CP 4 3, CP 47 and D1/D2/cytb(559) sub-assemblies. Quantitative comparisons reveal that neither absorption nor fluorescence spectra of core complexes are simple additive combinations of the spectra of the sub-assemblies. The absorption spectrum of the D1/D2/cytb(559) component embedded within the core complex appears significantly better structured and red-shifted compared to that of the isolated sub-assembly. A characteristic MCD reduction or 'deficit' is a useful signature for the central chlorins in the reaction centre. We note a congruence of the MCD deficit spectra of the isolated D1/D2/cytb(559) sub-assemblies to their laser-induced transient bleaches associated with P 680. A comparison of spectra of core complexes prepared from different organisms helps distinguish features due to inner light-harvesting assemblies and the central reaction-centre chlorins. Electrochromic spectral shifts in core complexes that occur following low-temperature illumination of active core complexes arise from efficient charge separation and subsequent plastoquinone anion (Q(A)(-)) formation. Such measurements allow determinations of both charge-separation efficiencies and spectral characteristics of the primary acceptor, Pheo(D1). Efficient charge separation occurs with excitation wavelengths as long as 700 nm despite the illuminations being performed at 1.7 K and with an extremely low level of incident power density. A weak, homogeneously broadened, charge-separating state of PSII lies obscured beneath the CP 47 state centered at 690 nm. We present new data in the 690-760 nm region, clearly identifying a band extending to 730 nm. Active core complexes show remarkably strong persistent spectral hole-burning activity in spectral regions attributable to CP 43 and CP 47. Measurements of homogeneous hole-widths have established that, at low temperatures, excitation transfer from these inner light-harvesting assemblies to the reaction centre occurs with approximately 70-270 ps(-1) rates, when the quinone acceptor is reduced. The rate is slower for lower-energy sub-populations of an inhomogeneously broadened antenna (trap) pigment. The complex low-temperature fluorescence behaviour seen in PSII is explicable in terms of slow excitation transfer from traps to the weak low-energy charge-separating state and transfer to the more intense reaction-centre excitations near 685 nm. The nature and origin of the charge-separating state in oxygen-evolving PSII preparations is briefly discussed.

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Section: Psii Sub-assembliesmentioning

confidence: 93%

Oxygen-evolving Photosystem II core complexes: a new paradigm based on the spectral identification of the charge-separating state, the primary acceptor and assignment of low-temperature fluorescence

Krausz

Hughes

Smith

et al. 2005

Photochem Photobiol Sci

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“…We have reported low-temperature optical studies of active PS II core complexes and compared them to spectra of isolated CP43 and CP47 and Nanba-Satoh assemblies (Hughes et al 2004e;Krausz and Peterson Å rsköld 2005;Peterson Å rsköld et al 2004). Isolated reaction centre absorptions were found to be both spectrally shifted to the blue by *4 nm and exhibiting significantly greater inhomogeneous broadening, as compared to the spectrum of the integral reaction centre as present in a PS II core complex.…”

Section: Introductionmentioning

confidence: 93%

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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“…We have performed a series of measurements of low-temperature absorption, emission, circular dichroism, magnetic circular dichroism, hole burning and fluorescence line narrowing, concentrating on PSII core preparations isolated from spinach [5][6][7][8][9][10][11][12][13][14]. PSHB experiments [7] led to the initial discovery that charge separation could be induced in PSII with wavelengths as long as 700 nm [15] and that optical excitation of the putative 'trap' CP47 chl a leads to efficient charge separation.…”

Section: Introductionmentioning

confidence: 99%

Spectral hole burning at the low-energy absorption edge of photosystem II core complexes

Hughes

Smith

Pace

et al. 2006

Journal of Luminescence

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The Native Reaction Centre of Photosystem II: A New Paradigm for P680

Cited by 11 publications

References 25 publications

Oxygen-evolving Photosystem II core complexes: a new paradigm based on the spectral identification of the charge-separating state, the primary acceptor and assignment of low-temperature fluorescence

Oxygen-evolving Photosystem II core complexes: a new paradigm based on the spectral identification of the charge-separating state, the primary acceptor and assignment of low-temperature fluorescence

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

Spectral hole burning at the low-energy absorption edge of photosystem II core complexes

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