A chlorophyll tilted 30° relative to the membrane in the Photosystem II reaction centre

Mieghem, F.J.E. van; Satoh, Kimiyuki; Rutherford, A. William

doi:10.1016/s0005-2728(05)80134-3

Cited by 145 publications

(139 citation statements)

References 32 publications

Supporting

Mentioning

123

Contrasting

Order By: Relevance

“…The spectra are virtually identical to those reported by van Mieghem and Rutherford (24) and are consistent with the localization of the triplet on a monomeric chlorophyll (19). There is no detectable contribution from triplets formed by intersystem crossing in the CP43 and CP47 core antenna.…”

Section: Site-directed Mutationssupporting

confidence: 88%

“…(2) The exciton coupling attributed to P (∼140 cm -1 ; 13-16) is far weaker than that associated with the bacterial primary donor (500-1000 cm -1 ; 1), most likely because of the greater separation (10 Å center to center) of P A and P B (17,18). (3) The P triplet, formed through charge recombination, at liquid helium temperature, between the primary donor-acceptor pair, is localized on a monomeric chlorophyll (19)(20)(21)(22)(23) with an orientation more like that of the bacterial reaction center monomeric accessory Bchlorophylls, B A or B B (15,24), while in bacterial reaction centers the triplet orientation is consistent with its localization on one or both of P A and P B (25,26). It has been suggested that the triplet and possibly the cation radical itself may be localized either on the PSII homologue of B A or B B (24,27) or that P A or P B or both in PSII have an orientation more like that of an accessory BChl than that of the special pair BChls of the bacterial reaction centers (24,28,29).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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.

show abstract

Section: Site-directed Mutationssupporting

confidence: 88%

Section: Introductionmentioning

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

View full text Add to dashboard Cite

show abstract

“…Compositionally, they resemble the so-called D1-D2-Cyt b 559 preparation that is purified by rather harsh detergent treatment from grana fractions of the thylakoid (70). This D1-D2-Cyt b 559 preparation has been extensively studied by spectroscopy, and much is known about its photochemistry and how light affects the photoreactions (71)(72)(73). The PSII reaction center we find here is not prepared by detergent and originates from totally different membrane locations in the margins, stroma lamellae, and the Y100 fraction.…”

Section: Table 4 Functional and Supramolecular Properties And Membranmentioning

confidence: 83%

Dimeric and Monomeric Organization of Photosystem II

Danielsson

Suorsa

Paakkarinen

et al. 2006

Journal of Biological Chemistry

118

View full text Add to dashboard Cite

The supramolecular organization of photosystem II (PSII) was characterized in distinct domains of the thylakoid membrane, the grana core, the grana margins, the stroma lamellae, and the so-called Y100 fraction. PSII supercomplexes, PSII core dimers, PSII core monomers, PSII core monomers lacking the CP43 subunit, and PSII reaction centers were resolved and quantified by blue native PAGE, SDS-PAGE for the second dimension, and immunoanalysis of the D1 protein. Dimeric PSII (PSII supercomplexes and PSII core dimers) dominate in the core part of the thylakoid granum, whereas the monomeric PSII prevails in the stroma lamellae. Considerable amounts of PSII monomers lacking the CP43 protein and PSII reaction centers (D1-D2-cytochrome b 559 complex) were found in the stroma lamellae. Our quantitative picture of the supramolecular composition of PSII, which is totally different between different domains of the thylakoid membrane, is discussed with respect to the function of PSII in each fraction. Steady state electron transfer, flash-induced fluorescence decay, and EPR analysis revealed that nearly all of the dimeric forms represent oxygen-evolving PSII centers. PSII core monomers were heterogeneous, and a large fraction did not evolve oxygen. PSII monomers without the CP43 protein and PSII reaction centers showed no oxygen-evolving activity.The thylakoid membrane of green plant chloroplasts hosts the large membrane-bound protein and pigment-protein complexes necessary for the photosynthetic light reactions (1). The thylakoid membrane has a complex organization where several domains can be distinguished: the appressed double planed region of grana, the nonappressed single planed grana margins, single planed stroma lamellae, and the two end membranes in the grana stack (2-4). The two photosystems are segregated in the thylakoid membrane: photosystem I (PSI) 3 with LHCI located to the stroma-exposed regions and PSII with LHCII located to the stacked grana core (5). This situation is dynamic and depends on many environmental factors (sun, shade, long or short light acclimation, etc.). In our greenhouse-grown leaf, there is 4 times more PSII than PSI in the central parts of grana, whereas in some parts of the stroma lamellae, there are more than 10 PSI per PSII (6). PSII, which contains more than 25 different proteins (7), initiates the photosynthetic electron transfer chain by using light as a driving force and water as an electron source (8, 9). To accomplish this, PSII operates at high oxidizing potentials (10, 11) and can therefore easily be damaged, especially under unfavorable environmental conditions (12). This gives rise to the photoinhibition-repair cycle, where damaged PSII centers are continuously being disassembled, repaired, and finally activated (12, 13). This continuous cycle, which at a given instance involves a large fraction of the PSII centers in the thylakoid membrane, is the main reason why PSII in vivo is very heterogeneous with respect to both functional and structural properties. In addition, the con...

show abstract

“…An electrochromic band-shift probably leads to the presence of the Chl D1 band as a shoulder in the (steady state) H D1 Ϫ spectrum. An alternative assignment for the Chl D1 keto stretch, however, is at 1,670 cm Ϫ1 , meaning that it is completely masked in our RP1 spectrum by the large positive (amide CAO) band at this frequency: The keto frequency of the tripletcarrying Chl at low temperature [either Chl D1 or Chl D2 (28,40,41)] has been reported to be at 1,670 cm Ϫ1 (28,31). Because the low temperature triplet-singlet spectrum in the visible coincides with the band in the P ϩ ͞P spectrum assigned to Chl D1 (9), Diner and coworkers (9) proposed Chl D1 as the triplet carrying Chl.…”

Section: Population Of H D1mentioning

confidence: 99%

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.

203

258

View full text Add to dashboard Cite

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...

show abstract

A chlorophyll tilted 30° relative to the membrane in the Photosystem II reaction centre

Cited by 145 publications

References 32 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

Dimeric and Monomeric Organization of Photosystem II

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

Contact Info

Product

Resources

About