The Primary Reaction of Plant Photosystem Ii

Knaff, David B.

doi:10.1111/j.1751-1097.1977.tb07494.x

Cited by 14 publications

(6 citation statements)

References 93 publications

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“…Because the spectra presented in Figure 3A and B were obtained with equal amounts of Chl, the fluorescence intensity of membranes before treatment with Triton X-100 was less in Figure 3B than that shown in Figure 3A and corresponded to the 1 5-min point for the F/Chl ratio in Figure 1. These results suggest that newly formed LHCs, which accounted for about half the total Chl in the sample shown in Figure 3B, were coupled to reaction centers and quenched by a nonradiative energy decay process (2,9,17). In contrast, the residual LHCs apparently remained uncoupled to reaction centers.…”

Section: Ps11 Activity Develops In Parallel With Newly Synthesized Chimentioning

confidence: 59%

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Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Jk¹,

Co²,

Lg³

1991

Plant Physiol.

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The origin of thylakoid membranes was studied in Chlamydomonas reinhardtii y-1 cells during greening at 380C. Previous studies showed that, when dark-grown cells are exposed to light under these conditions, the initial rates of accumulation of chlorophyll and the chlorophyll a/b-binding proteins in membranes are maximal (MA Maloney JK Hoober, DB Marks [1989] Plant Physiol 91: 1100-1106; JK Hoober MA Maloney, LR Asbury, DB Marks [1990] Plant Physiol 92: 419-426). As shown in this paper, photosystem 11 activity, which was nearly absent in dark-grown cells, also increased at a linear rate in parallel with chlorophyll. As compared with those made at 250C, photosystem 11 units assembled during greening at 380C were photochemically more efficient, as judged by saturation at a lower fluence of light and a negligible loss of excitation energy as fluorescence. Electron microscopy of cells in light for 5 or 15 minutes at 380C showed that these initial, functional thylakoid membranes developed in association with the chloroplast envelope.

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Section: Ps11 Activity Develops In Parallel With Newly Synthesized Chimentioning

confidence: 59%

“…ref. 17). The quenching of fluorescence clearly was a consequence of the environment of the Chls, because dissociation of LHCs with Triton X-100 increased the fluorescence yield to the level expected with free Chl.…”

mentioning

confidence: 99%

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Jk¹,

Co²,

Lg³

1991

Plant Physiol.

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“…For cMoroplast photosynthesis, it is tliought that the primary donor of photosystetn 1 (P700) is a ehloro-phyU a special pair (Norris et al, 1971;Norris et al, 1974). The primary donor of photosystem II (P680) is altnost certainly a speeialized fonn of ehlorophyU a, but that it has a special pair strueture is tiot firmly supported (Knaff, 1977). It is thought that the primary aeeeptor in photosystem I is an iron-sulphur protein (Bearden & Malkin, 1975).…”

Section: Porphyrins: Chlorophyll Protochlorophyll and Hemementioning

confidence: 99%

Photoreceptors for biosynthesis, energy storage and vision

Presti

Delbrück

1978

Plant Cell & Environment

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Dving organistns use light as a source of energy and as a tneans of obtaitiing infonnation about their environtnent. Photoreactivating enzytne, provitamins D, retinal (rhodopsins and bacteriorhodopsin), porphyrins (chlorophyll, protochlorophyll and heme), photosynthetic accessory pigtnents (carotenoids and bihns), phytochrotne and riboflavin: these are the tiiolecules wliich life has settled upon to play the role of liglit receptor. For sotne of these photoreceptor molecules a great deal is now known about the chetnistry wliich they perform upon absorbing hglit; for others virtually nothing is known. Riboflavin, tlie tnolecule believed to be futictiotiitig in a variety of organistns as the receptor for physiological responses to blue liglit, is an especially ititerestitig ease. Its widespread occurrence in cellular roles other tlian photoreception tnake it difficult to separate out the particular flavin wliich functions as the photoreceptor. It represents a case of a photoreceptor which is at once ubiquitous and elusive.

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“…8) or a monomer (9) of chlorophyll (Chl), and the primary acceptor, Q, a special form of plastoquinone (PQ) (8)(9)(10)(11)(12)(13)(14). From measurements of nanosecond recombination luminescence from PS II, the lifetime of the state [P68OPheo] has been found to be z3 ns at 295 K [3].…”

mentioning

confidence: 99%

Interaction between the intermediary electron acceptor (pheophytin) and a possible plastoquinone-iron complex in photosystem II reaction centers

Klimov

Dolan²,

Shaw³

et al. 1980

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

116

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Photoreduction of the intermediary electron acceptor, pheophytin (Pheo), in photosystem II reaction centers of spinach chloroplasts or subchloroplast particles (TSF-II and TSF-IIa) at 220 K and redox potential Eh = -450 mV produces an EPR doublet centered at g = 2.00 with a splitting of 52 G at 7 K in addition to a narrow signal attributed to Pheo (g = 2.0033, AH -13 G). The doublet is eliminated after extraction of lyophilized TSF-II with hexane containing 0. Phototrapping of Pheo-in PS II at 295 K is accompanied by the appearance of an EPR signal with g k 2.0035 and AH 13 G (1 G = 10-4 tesla) (6, 7), similar to that of the monomeric The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §17734 solely to indicate this fact. 7227anion radical of Pheo in vitro (18). After phototrapping of Pheo at 220 K, however, an EPR "doublet" centered at g = 2.00 with a splitting of m52 G is also observed (7). In analogy with a similar observation in bacterial reaction centers (19)(20)(21)(22), it was suggested that the doublet is probably the result of interaction of Pheo' with Q, which includes Fe or some other transition metal (7). Here we report data supporting the idea that a PQ-Fe complex acts as the stable "primary" electron acceptor in PS II reaction centers and that an exchange interaction of its singly reduced form with Pheo-accounts for the split EPR signal. MATERIALS AND METHODSSpinach chloroplasts and subchloroplast particles (Tritonfractionated subchloroplast fragments, TSF-II and TSF-IIa), highly enriched in PS II reaction center components and free of P700, were isolated as described (23- Iron was extracted by incubating PS II preparations (Chl at 50 mg/ml) in 10 mM Tris-HCI (pH 8.0) containing 0.3-1 M LiCl04 with or without 2.5 mM o-phenanthroline, for 2 hr at 20C, followed by centrifugation (200,000 X g for 40 min) and dialysis (12 hr at 2°C) of the pellet against 10 mM Tris-HCl (pH 8.0)/50 mM NaCI/10 AM EDTA (David Knaff, personal communication; also ref. 27). In the reconstitution experiments the extracted material was additionally dialyzed for 12 hr at 20C under anaerobic conditions against 10 mM acetate buffer (pH 5.5) containing 0.2 M LiCl04 and 1 MM EDTA, with or without 0.2 mM Fe(NH4)2(SO4)2, MnSO4, or MgSO4.Nonheme iron content was determined by the bathophenanthroline method (28). Changes in absorbance and fluorescence yield, induced by actinic light (intensity t0.05 Jcm2-s-l) from a 1000-W incandescent lamp filtered by 5 cm of CuSO4 solution, were measured in a phosphoroscopic pho-

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The Primary Reaction of Plant Photosystem Ii

Cited by 14 publications

References 93 publications

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Photoreceptors for biosynthesis, energy storage and vision

Interaction between the intermediary electron acceptor (pheophytin) and a possible plastoquinone-iron complex in photosystem II reaction centers

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