| | 1 | Author
| John Bowyer1, Mark Hiltonb, Julian Whitelegge3, Philip Jewess6, Patrick Camillerib, Antony Croftsc, Howard Robinsonc | Requires cookie* | | | Title
| Molecular Modelling Studies on the Binding of Phenylurea Inhibitors to the D 1 Protein of Photosystem II  | | | | Abstract
| A hypothetical molecular model of part of the D 1 protein of photosystem II, based on the analogous portion of the L subunit of the Rhodopseudomonas viridis reaction centre, has been used to study the binding of an extended hydrophobic phenylurea inhibitor (N,N-dimethyl-carbamoyl)4 -amino-4 '-chloro-rra«5 -stilbene) (I) to the Q B site. The inhibitor was fitted by eye into a cleft in the site, and a limited part of the inhibitor/D 1 complex was energy minimized. The gross orientation of the inhibitor placed the dimethylurea moiety towards the predicted binding domain of the plastoquinone head group, and the stilbene moiety directed along the quinone isoprenoid side chain binding domain, suggesting a similar pathway of approach of the two molecules from the membrane into the binding site. Binding interactions of the inhibi tor included hydrogen bonds to the side chain hydroxyl of ser 264 and the peptide carbonyl group of ala 251, with the side chain hydroxyl of ser 268 as an alternative ligand. Numerous hydrophobic contacts were also possible. Although phenylureas do not bind to reaction centres of Rp. viridis, many of the binding interactions to D 1 could also be detected in Rp. viridis. However, the ß-CH2 and 5-C02-groups of glu 212 in Rp. viridis are located in the corresponding region of D 1 occupied by the dimethylurea moiety of the inhibitor in our model of its binding to D 1. This may explain why diuron (D C M U) does not bind to Rp. viridis reac tion centres. | | | |
Reference
| Z. Naturforsch. 45c, 379—387 (1990); received November 23 1989 | | | |
Published
| 1990 | | | |
Keywords
| Phenylureas, Photosystem II, D 1 Protein, Molecular Modelling | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0379.pdf | | | | Identifier
| ZNC-1990-45c-0379 | | | | Volume
| 45 | |
| 2 | Author
| SudhirK. Sopory3, M. Bruce, Greenbergb, RoshniA. Mehtaac, Marvin Edelmanab, AutarK. Mattooa | Requires cookie* | | | Title
| Free Radical Scavengers Inhibit Light-Dependent Degradation of the 32 kDa Photosystem II Reaction Center Protein | | | | Abstract
| Involvement of oxygen-free radicals in the rapid, light-dependent degradation of the 32 kDa photosystem II reaction center protein was investigated. The free radical scavengers propyl-gallate and uric acid inhibited 32 kDa protein degradation without affecting linear electron flow. The involvement of singlet oxygen was excluded. Protection from degradation was also afforded under ultra-violet and far-red radiations. These data implicate free-radical damage as a common step in the degradation process, and emphasize the oxygen environment as a causa tive factor in destabilization of the 32 kDa protein. | | | |
Reference
| Z. Naturforsch. 45c, 412—417 (1990); received December 28 1989 | | | |
Published
| 1990 | | | |
Keywords
| Spirodela oligorrhiza, Chloroplast, D 1 Protein, Photosynthesis | | | |
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| | | | | TEI-XML for
| default:Reihe_C/45/ZNC-1990-45c-0412.pdf | | | | Identifier
| ZNC-1990-45c-0412 | | | | Volume
| 45 | |
| 3 | Author
| A. Aiach, U. Bodner, U. Johanningm | Requires cookie* | | | Title
| A Herbicide Resistant Euglena Mutant Carrying a Ser to Thr Substitution at Position 265 in the D 1 Protein of Photosystem II | | | | Abstract
| A herbicide resistant Euglena mutant (M SI) has been obtained by adapting wild type cells to increasing concentrations o f D C M U (3-(3',4'-dichlorophenyl)-l ,1-dimethylurea). Lower re sistance levels towards D C M U and metribuzin were observed in MSI when compared with Euglena or C hlam ydom onas mutants with Ser 264 to Ala substitutions. RNA-sequence analysis identified a Ser to Thr change at position 265 (equivalent to position 264 in other organisms), thus making it possible to compare the influence o f amino acids Ser, Ala and Thr at identical positions on the inhibitory effect o f structurally different herbicides in the same species. | | | |
Reference
| Z. Naturforsch. 47c, 245 (1992); received October 31 1991 | | | |
Published
| 1992 | | | |
Keywords
| Herbicides, D 1-Protein, Point M utation, Resistance, Euglena | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0245.pdf | | | | Identifier
| ZNC-1992-47c-0245 | | | | Volume
| 47 | |
| 4 | Author
| Walter Oettmeier, Klaus Masson, Ralf Kloos, Ellen Reil | Requires cookie* | | | Title
| On the Orientation of Photosystem II Inhibitors in the QB-Binding Niche: Acridones, Xanthones and Quinones | | | | Abstract
| The orientation o f acridones, xanthones, 1,4-benzo-and naphthoquinones within the ph o tosystem II Q b herbicide-binding niche was studied by means o f mild trypsination and by esti mation o f p /50-values in Chlamydomonas reinhardtii D 1 mutants (Val219 > lie, A la25, > Val, Phe255 > Tyr, Ser264 > Ala, A sn266 > Thr, and Leu275 > Phe). A s judged from the R/S-values (ratios o f -^50 -values resistant versus susceptible type) close to 1 in all mutants, the acridones and xanthones do not have strong interactions with the parent amino acids. Contrary, the qui-nones exhibit extreme low R/S-values down to 0.003 (for 2,5-dibrom o-3-m ethyl-6-isopropyl-1,4-benzoquinone; D BM IB) in the Ser264 mutant. This extreme negative cross resistance or supersensitivity indicates that the quinones do not droxyl group. | | | |
Reference
| Z. Naturforsch. 48c, 146—151 (1993); received December 3 1992 | | | |
Published
| 1993 | | | |
Keywords
| Chlamydomonas reinhardtii Mutants, D 1 Protein, Antibody, Trypsination | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0146.pdf | | | | Identifier
| ZNC-1993-48c-0146 | | | | Volume
| 48 | |
| 5 | Author
| E. B. Racht, A. Trebst | Requires cookie* | | | Title
| Hypothesis on the Control of D 1 Protein Turnover by Nuclear Coded Proteins in Chlamydomonas reinhardtii | | | | Abstract
| A hypothesis is presented on the events in the degradation of the D 1 protein of photosys tem II in the light. It proposes the existence of a nuclear encoded cleavage system that is turning over and which is m odulated by its phosphorylation state. A new experimental ap proach is presented in which the D 1 protein degradation under photoinhibitory light is tested in Chlam ydom onas reinhardtii grown under phosphate deficiency and pretreated with cyclo-heximide. Under these conditions the degradation of the D 1 protein is delayed whereas in C hlam y dom onas reinhardtii grown in full medium the D 1 protein is rapidly disappearing in high light upon addition o f chloramphenicol (CAP) or lincomycin for inhibiting the resynthesis of the D 1 protein . Cycloheximide (C H I) has little effect on photoinhibition in such control cells. In cells grown, however, for 20 h in phosphate deficiency -such that there is not yet loss of photosynthesis capacity -pretreatment with cycloheximide or canavanine in low light the degradation of the D 1 protein even in 6 h high light is prevented to an appreciable extent. Further addition of CAP or lincomycin has only a small effect. [14C]leucine incorporation was used to show that there is no resynthesis and that the presence of the D 1 protein is due to a delay of degradation. The results are interpreted to show that excess high light which converts the D 1 protein into a potentially, degradable m ode is not sufficient for degradation of the D 1 protein. A cleavage system is needed as well. It is postulated that under phosphate deficiency and pre treatment with CHI or canavanine a nuclear coded cleavage system for the D 1 protein is depleted, i.e. the cleavage system for the rapidly turning over D 1 is also turning over. It is shown that under phosphate deficiency an alkaline phosphatase activity in the chloro plast and the thylakoid membrane o f Chlam ydom onas reinhardtii is increased. It is proposed that the ratio of kinase/phosphatase converts an active, stable phosphorylated cleavage system into a labile unphosphorylated and turning over state. | | | |
Reference
| Z. Naturforsch. 49c, 439 (1994); received January 31/May 13 1994 | | | |
Published
| 1994 | | | |
Keywords
| Chlamydomonas, D 1 Protein, Photoinhibition, Photosystem II, Phosphate Deficiency | | | |
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| default:Reihe_C/49/ZNC-1994-49c-0439.pdf | | | | Identifier
| ZNC-1994-49c-0439 | | | | Volume
| 49 | |
| 6 | Author
| J.Dirk Naber, JackJ S Van Rensen | Requires cookie* | | | Title
| Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein | | | | Abstract
| The reversible binding kinetics o f atrazine, diuron and ioxynil were measured via their bind ing and release parameters during steady state inhibition o f electron transport. The parameters were determined in isolated chloroplasts o f peas and o f triazine-resistant and -susceptible bio types o f Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns o f isolated broken chloroplasts. It was found that the binding parameters were always significantly higher in the case o f an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resist ance seems to originate from a significant increase o f the release kinetics. The release parame ters could be used to calculate the residence times o f the herbicides at the D 1 protein. The values o f these residence times were always much higher for the herbicides than for Q B; this explains the inhibition o f electron transport. The only exception was the residence time o f atra zine in the resistant biotype, where the value was close to that o f Q B. It is concluded that the "on" kinetics o f a com pound to its binding environment at the D 1 protein are determined principally by the accessibility o f the niche to the com pound. The dif ferences in activity between herbicides are mainly due to variations in the release kinetics. | | | |
Reference
| Z. Naturforsch. 46c, 575—5 (1991); received March 18 1991 | | | |
Published
| 1991 | | | |
Keywords
| Chloroplasts, Photosystem II, D 1 Protein, Herbicides, Triazine Resistance | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0575.pdf | | | | Identifier
| ZNC-1991-46c-0575 | | | | Volume
| 46 | |
| 7 | Author
| KlausG. Tietjen, Wilfried Draber, John Goossens, JohannesR. Jansen, JoachimF. Kluth, Michael Schindler, Heinz-Jürgen, Wroblowsky Bayer, A. G. | Requires cookie* | | | Title
| Binding of Triazines and Triazinones in the QB-Binding Niche of Photosystem II | | | | Abstract
| A series o f 20 triazines (derivatives o f 2-alkylam ino-4-benzylam ino-6-chloro-l,3,5-triazines) and 37 triazinones (derivatives o f 3-alkyl-4-am ino-6-phenyl-l,2,4-triazin-5-ones) is tested for inhibitory potency in photosynthetic electron flow through photosystem II o f wild type Chla-mydomonas reinhardtii and o f five mutants with aminoacid substitutions in the D 1 protein at valine 219, alanine 251, phenylalanine 255, serine 264, and leucine 275. The data are used for computer modelling o f .the possible location o f the com pounds within a three dimensional model o f the QB-binding niche o f the D 1 protein. | | | |
Reference
| Z. Naturforsch. 48c, 205 (1993); received November 23 1992 | | | |
Published
| 1993 | | | |
Keywords
| D 1 Protein, Herbicides, Molecular M odeling, Photosystem II, Q B-Binding Niche | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0205.pdf | | | | Identifier
| ZNC-1993-48c-0205 | | | | Volume
| 48 | |
| 8 | Author
| Aloysius Wild, Petra Strobel, Ute Flammersfeld | Requires cookie* | | | Title
| Studies of Components of the Thylakoid Membrane of Undamaged and Damaged Spruce Trees at Different Mountain Sites | | | | Abstract
| During a five-year period, com ponents o f the thylakoid membrane in needles o f the second generation o f undamaged and damaged trees o f Norway spruce were studied at three different mountain sites in W est Germany. Visible signs o f damage at these sites are a yellowing o f the light-exposed sides o f the needles as well as the loss o f needles. The goal o f this study was to determine damage-induced alterations in com position and physiological reactions o f the thy lakoid membranes in spruce needles. In order to meet this purpose, contents o f chlorophyll a and b, electron transport rate o f photosystem II, contents o f the D 1 protein, cytoch rom e/, as well as P-700 were measured. The chlorophyll content in the needles o f the damaged spruce trees was significantly lower than in the needles o f the undamaged trees. In addition to this, the typical annual course o f chlorophyll content was exclusively observed in the needles o f the undamaged spruce trees. If related to dry weight, a drastic reduction o f the electron transport rate and o f the redox com ponents o f the thylakoid membrane was observed due to damage, indicating a degeneration o f the photosynthetic membranes. The contents o f D 1 protein and the photosynthetic electron transport rates were also markedly reduced in the needles o f the damaged trees, when related to chlorophyll content o f thylakoids, suggesting an early and particular impairment o f photo system II. The comparison o f spruce trees showing different signs o f damage demonstrates that certain biochemical parameters concerning the photosynthetic membranes (chlorophyll, cytochrom e/ , ratio photosystem II/I) reflect the extent o f damage and are suitable for an early indication o f a beginning, but still invisible damage o f spruce trees. | | | |
Reference
| Z. Naturforsch. 48c, 911 (1993); received June 5/August 27 1993 | | | |
Published
| 1993 | | | |
Keywords
| Chlorophyll, Cytochrome /, D 1 Protein, Forest Decline, P-700, Photosynthetic Electron Transport | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0911.pdf | | | | Identifier
| ZNC-1993-48c-0911 | | | | Volume
| 48 | |
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