Photosystem I of Synechococcus elongatus at 4 Å resolution: comprehensive structure analysis

Schubert, Wolf‐Dieter; Klukas, Olaf; Krauß, Norbert; Saenger, Wolfram; Fromme, Petra; Witt, H. T.

doi:10.1006/jmbi.1997.1269

Cited by 274 publications

(318 citation statements)

References 142 publications

(162 reference statements)

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“…Although the shape of the Gloeobacter PS I spectrum is normal, it has a surprisingly low amplitude, indicating a Chl:P700 ratio of 147. This is large in comparison with the antenna size for PS I preparations from higher plants and other cyanobacteria, which is about 90 Chl per P700 (Schubert et al 1997). An even larger value of 175 chlorophyll molecules per P700 was observed earlier for isolated plasma membranes from Gloeobacter under illumination with continuous blue light (Koenig and Schmidt 1995).…”

Section: Difference Spectroscopymentioning

confidence: 85%

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Mangels

Kruip

Berry

et al. 2002

Photosynthesis Research

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Photosystem I from the unusual cyanobacterium Gloeobacter violaceus Mangels, D.; Kruip, J.; Berry, S.; Rögner, M.; Boekema, E.J.; Koenig, F. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Key words: antenna system, electron microscopy, fluorescence, light harvesting, photosynthesis, plasma membrane AbstractPhotosystem I (PS I) from the primitive cyanobacterium Gloeobacter violaceus has been purified and characterised. Despite the fact that the isolated complexes have the same subunit composition as complexes from other cyanobacteria, the amplitude of flash-induced absorption difference spectra indicates a much bigger antenna size with about 150 chlorophylls per P700 as opposed to the usual 90. Image analysis of the PS I preparation from Gloeobacter reveals that the PS I particles exist both in a trimeric and in a monomeric form and that their size and shape closely resembles other cyanobacterial PS I particles. However, the complexes exhibit a higher molecular weight as could be shown by gel filtration. The preparation contains novel polypeptides not related to known Photosystem I subunits. The N-terminal sequence of one of those polypeptides has been determined and reveals no homology to known or hypothetical proteins. Immunoblotting shows a cross-reaction of three of the polypeptide bands with an antibody raised against the major LHC from the diatom Cyclotella cryptica. Electron microscopy reveals a novel T-shaped complex which has never been observed in any other cyanobacterial PS I preparation. 77 K spectra of purified PS I show an extreme blue-shift of the fluorescence emission, indicating an unusual organisation of the PS I antenna system in Gloeobacter.Abbreviations: PS -photosystem; Chl -chlorophyll; DM -dodecyl-β-D-maltoside; ECL -enhanced chemiluminescence; HPLC -high performance liquid chromatography; IEC -ion exchange chromatography; GF -gel filtration; LHC I -light harvesting complex associated with Photosystem I; P700 -primary electron donor of photosystem I; SDS -sodium dodecyl sulfate; SQDG -sulfoquinovosyl diacylglycerol; PAGE -polyacrylamide gel electrophoresis; F760 (F730) -fluorescence band with maximal emission at 760 nm (730 nm)

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Section: Difference Spectroscopymentioning

confidence: 85%

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Mangels

Kruip

Berry

et al. 2002

Photosynthesis Research

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“…The cyanobacterial PSI complex is dissociated eight times faster in the monomeric than in the trimeric form as shown by urea treatment of monomers and trimers (4,31). Plant PSI is a monomer that is more stable upon urea treatment than the trimeric cyanobacterial PSI (8).…”

Section: Discussionmentioning

confidence: 99%

Cosuppression of Photosystem I Subunit PSI-H in Arabidopsis thaliana

Naver¹,

Haldrup²,

Scheller³

1999

Journal of Biological Chemistry

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PSI-H is an intrinsic membrane protein of 10 kDa that is a subunit of photosystem I (PSI). PSI-H is one of the three PSI subunits found only in eukaryotes. The function of PSI-H was characterized in Arabidopsis plants transformed with a psaH cDNA in sense orientation. Cosuppressed plants containing less than 3% PSI-H are smaller than wild type when grown on sterile media but are similar to wild type under optimal conditions. PSI complexes lacking PSI-H contain 50% PSI-L, whereas other PSI subunits accumulate in wild type amounts. PSI devoid of PSI-H has only 61% NADP ؉ photoreduction activity compared with wild type and is highly unstable in the presence of urea as determined from flashinduced absorbance changes at 834 nm. Our data show that PSI-H is required for stable accumulation of PSI and efficient electron transfer in the complex. The plants lacking PSI-H compensate for the less efficient PSI with a 15% increase in the P700/chlorophyll ratio, and this compensation is sufficient to prevent overreduction of the plastoquinone pool as evidenced by normal photochemical quenching of fluorescence. Nonphotochemical quenching is approximately 60% of the wild type value, suggesting that the proton gradient across the thylakoid membrane is decreased in the absence of PSI-H.

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“…Following charge separation in PS-I, the oxidized reaction center chlorophyll pair (P700 ϩ ) is reduced by plastocyanin (Pc). The oxidized Pc is ultimately reduced in the cytochrome b 6 f complex (reviewed in Ref. 3).…”

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The Location of Plastocyanin in Vascular Plant Photosystem I

Ruffle¹,

Mustafa²,

Kitmitto³

et al. 2002

Journal of Biological Chemistry

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We have studied the binding sites of the electron donor and acceptor proteins of vascular plant photosystem I by electron microscopy/crystallography. Previously, we identified the binding site for the electron acceptor (ferredoxin). In this paper we complete these studies with the characterization of the electron donor (plastocyanin) binding site. After cross-linking, plastocyanin is detected using Fourier difference analysis of two dimensionally ordered arrays of photosystem I located at the periphery of chloroplast grana. Plastocyanin binds in a small cavity on the lumenal surface of photosystem I, close to the center and with a slight bias toward the PsaL subunit of the complex. The recent release of the full coordinates for the cyanobacterial photosystem I reaction center has allowed a detailed comparison between the structures of the eukaryotic and prokaryotic systems. This reveals a very close homology, which is particularly striking for the lumenal side of photosystem I.The multisubunit protein complexes responsible for the light reactions of photosynthesis are found in the thylakoid membranes within the chloroplasts of vascular plants. Photosystem I (PS-I) 1 is found at the edges of the granal stacks and in the stromal lamellae of these thylakoid membranes (1, 2). PS-I catalyzes the part of the light reactions responsible for the absorption of light energy and generating reduced ferredoxin via a series of electron carriers across the thylakoid membrane. Following charge separation in PS-I, the oxidized reaction center chlorophyll pair (P700 ϩ ) is reduced by plastocyanin (Pc). The oxidized Pc is ultimately reduced in the cytochrome b 6 f complex (reviewed in Ref.3).The three-dimensional structure of a cyanobacterial PS-I reaction center has been described for Synechococcus elongatus (4 -8) to a current resolution better than 3 Å resolution. This structure does not show the location of the mobile electron carriers Pc and ferredoxin (Fd) as they are lost during the purification of the complex.Two-dimensional crystals of a P22 1 2 1 plane group occurring at the edges of grana in spinach thylakoids have been shown to contain PS-I and have yielded structural data to 2.7 nm (2) and refined three-dimensional data to 2.5 nm resolution (9). Unlike cyanobacteria, spinach PS-I does not appear to form trimers but does show many common structural features (2, 9). In neither of the studies on spinach (2, 9) were the mobile electron carriers Pc and Fd retained. However, studies on the binding site for Fd, the terminal mobile electron acceptor in PS-I, have recently been possible (10) using a cross-linking and image analysis approach.In-vivo, cyanobacterial and algal PS-I can be reduced by either Pc or the alternative electron donor cytochrome c6, whereas vascular plant PS-I is reduced only by Pc. Structural insight into Pc binding in cyanobacteria has been derived from modeling studies using PS-I from the cyanobacterium S. elongatus and Pc from Enteromorpha prolifera (a green alga) (7). This study concluded that the li...

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Photosystem I of Synechococcus elongatus at 4 Å resolution: comprehensive structure analysis

Cited by 274 publications

References 142 publications

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Cosuppression of Photosystem I Subunit PSI-H in Arabidopsis thaliana

The Location of Plastocyanin in Vascular Plant Photosystem I

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