Photosynthetic thylakoid membranes in plants contain highly folded membrane layers enriched in photosystem II, which uses light energy to oxidize water and produce oxygen. The sunlight also causes quantitative phosphorylation of major photosystem II proteins. Analysis of the Arabidopsis thaliana stn7xstn8 double mutant deficient in thylakoid protein kinases STN7 and STN8 revealed light-independ...

In plants and cyanobacteria, the primary step in oxygenic photosynthesis, the light induced charge separation, is driven by two large membrane intrinsic protein complexes, the photosystems I and II. Photosystem I catalyses the light driven electron transfer from plastocyanin/cytochrome c(6) on the lumenal side of the membrane to ferredoxin/flavodoxin at the stromal side by a chain of electron c...

Sensitive differential scanning calorimetry was employed to investigate thylakoid membrane structure. Calorimetric scans of chloroplast membranes suspended in a low ionic strength Hepesbuffered medium revealed endothermic transitions centered at the following temperatures ( degrees C): A (42.5), B (60.6), C(1) (64.9), C(2) (69.6), D (75.8), E (84.3), and F (88.9). The B transition was demonstra...

1. Chemical modification of chloroplast membranes by diazonium benzenesulfonic acid (DABS) resulted in marked inhibition of noncyclic and cyclic photophosphorylation. Accompanying the inhibition of ATP synthesis there was an increased rate of basal electron flow and loss of the ability of ADP to stimulate the basal electron transport rate, both characteristic of uncoupling. 2. The calcium-depen...

The variable fluorescence yield of photosystem II is dependent on the redox state of the fluorescence quencher molecule or the primary electron acceptor of the system. We have carried out redox titrations of fluorescence yield of a photochemically active photosystem-II reaction-center particle and have measured the redox potential of the photosystem-II primary acceptor.During reductive titratio...

One copy of the psbA gene which codes for the photosystem II reaction center D-1 protein from the thermophilic cyanobacterium Synechococcus elongatus has been sequenced. It is feasible that a disulfide bridge between D-1 Cys212 and D-2 Cys212 is responsible for the thermostability of the photosystem II reaction center from Synechococcus elongatus.

Due to the great abundance of genomes and protein structures that today span a broad diversity of organisms, now more than ever before, it is possible to reconstruct the molecular evolution of protein complexes at an incredible level of detail. Here, I recount the story of oxygenic photosynthesis or how an ancestral reaction center was transformed into a sophisticated photochemical machine capa...

Jutta Thiemann and W olfgang Barz Institut für Biochemie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität, Hindenburgplatz 55, D-48143 Münster, Bundesrepublik Deutschland Dedicated to Professor Rolf Wiermann on the occasion o f his 60th birthday Z. Naturforsch. 49c, 791-801 (1994); received May 30/July 11, 1994 Chenopodium rubrum, Photoautotrophic Cell Cultures, Herbicide Resi...

Photosystem II, Low Temperature Fluorescence, Tobacco, Neottia The mykotrophic orchid Neottia nidus-avis does not evolve oxygen in the light but is able to perform photophosphorylation. The low temperature fluorescence emission spectrum lacks the 680 and 690 nm bands. Hence, the spectroscopic chlorophyll a forms which are attributed to photosystem II do not occur in plastids of this orchid. The...

Photoinhibition was studied in osmotically broken chloroplasts isolated from spinach leaves (Spinacia oleracea L.). Both whole chain electron transport (measured as ferricyanide-dependent O(2) evolution in the presence of NH(4)Cl) and photosystem II activity (measured as O(2) evolution in the presence of either silicomolybdate plus 3-(3,4-diphenyl)-1,1 dimethylurea or parabenzoquinone) showed s...