| | 1 | 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 | |
| 2 | Author
| P. He, K. P. Bader, G. H. Schm, G. Renger, K. P. Bader, G. H. Schmid | Requires cookie* | | | Title
| Mass Spectrometric Analysis of N 2-Formation Induced by the Oxidation of Hydrazine and Hydroxylamine in Flash Illuminated Thylakoid Preparations of the Filamentous Cyanobacterium Oscillatoria chalybea | | | | Abstract
| Analogue In tobacco chloroplasts hydrazine-dependent dinitrogen form ation measured by mass spec trometry as the consequence o f short saturating light flashes is always linked to a substantial oxygen uptake (1990). However, in thylakoids o f the filamentous cyanobacterium Oscillatoria chalybea this dinitrogen formation is not linked to an apparent 0 2-uptake, even at the high concentration o f 1 mM hydrazine. Whereas in tobacco chloroplasts Tris-treatment does not affect hydrazine de pendent dinitrogen formation up to a concentration o f 3 mM hydrazine, Tris-treatment o f thy lakoids o f O. chalybea affects strongly both oxygen evolution and dinitrogen evolution under a single turnover flash as well as under ten flashes. In contrast to tobacco chloroplasts, the pres ence o f hydrazine up to concentrations o f 3 mM does not substantially affect photosynthetic 0-,-evolution. The observed dinitrogen evolution is affected by D C M U regardless whether in duced by a single turnover flash or by ten flashes, whereas in tobacco dinitrogen evolution and the 0-,-uptake linked to it (which is not observed in the cyanobacterium) were clearly not af fected by D C M U in the single turnover flash. In Oscillatoria the earlier described Photosystem II-mediated H-,0-, formation and decom position is influenced by hydrazine. In the presence o f 300 hm hydrazine the usually present 0 2-uptake leading to H:0 : formation appears dimin ished. | | | |
Reference
| Z. Naturforsch. 46c, 629 (1991); received March 21 1991 | | | |
Published
| 1991 | | | |
Keywords
| Filamentous Cyanobacterium, Photosystem II, Water Splitting, S-States, Hydrogen-Peroxide | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0629.pdf | | | | Identifier
| ZNC-1991-46c-0629 | | | | Volume
| 46 | |
| 3 | Author
| S. C. Sabat, V. Vijayavergiya, B. C. Tripathy, PrasannaM. Ohanty | Requires cookie* | | | Title
| Inhibitory Effect of Crown Compound on Photoelectron Transport Activity of Beet Spinach Thylakoid Membranes | | | | Abstract
| The effect o f K-picrate-18-crown-6 (crown) on the photoelectron transport activity o f beet spinach thylakoid membranes was investigated. A ddition o f micromolar concentration o f crown to thylakoid preparation inhibited p-benzoquinone, chloride-indophenol, methyl violo-gen supported Hill activities maximally by 75 per cent in a concentration dependent manner. However, the photosystem I catalyzed reaction remained insensitive to crown suggesting that crown specifically inhibits photosystem II electron transport. Addition o f exogenous electron donors like hydroxylamine or diphenylcarbazide failed to restore the crown induced inhibition o f photosystem II electron transport and lowering o f steady state chlorophyll a fluorescence yield. These observations suggest that crown also inhibits photosystem II catalyzed electron transport after the donation sites o f these exogenous donors. Washing o f the crown pre-treat-ed thylakoids with isolation buffer, relieved the crown inhibited electron transport activity, indicating that this inhibition is reversible. Furthermore, in hydroxylamine washed thylakoids which are devoid o f 0 2 evolution capacity, the hydroxylamine induced increase in chlorophyll a fluorescence o f variable yield was quenched by the addition o f crown. These observations suggest that crown affects the oxygen evolution and inhibits at a site close to photosystem II reaction centres. | | | |
Reference
| Z. Naturforsch. 46c, 87 (1991); received August 14 1990 | | | |
Published
| 1991 | | | |
Keywords
| Crown-Ether, Electron Transport, Photosystem II, Thylakoids, Beet Spinach ( Beta vulgaris) | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0087.pdf | | | | Identifier
| ZNC-1991-46c-0087 | | | | Volume
| 46 | |
| 4 | Author
| Bengt Svensson, Imre Vass, Stenbjörn Styring | Requires cookie* | | | Title
| Sequence Analysis of the D 1 and D 2 Reaction Center Proteins of Photosystem II | | | | Abstract
| A com pilation o f 38 sequences for the D1 and 15 sequences for the D 2 reaction center pro teins o f photosystem II is presented. The sequences have been compared and a similarity index that takes into account the degree o f conservation and the quality o f the changes in each posi tion has been calculated. The similarity index is used to identify and describe functionally im portant domains in the D 1 /D 2 heterodimer. Comparative hydropathy plot are presented for the aminoacid sidechains that constitute the binding domain o f the tyrosine radicals, Tyrz and TyrD, in photosystem II. The structure around Tyrz is more hydrophilic than the structure around TyrD. The hydrophilic residues are clustered in the part o f the binding pocket for Tyrz that is turned towards the lumenal side o f the thylakoid membrane. M ost prominent is the presence o f two conserved carboxylic am inoacids, D l-A sp 170 and D l-G lu 189. Their respec tive carboxyl-groups com e close in space and are proposed to constitute a metal binding site together with D l-G ln 165. The distance between the proposed metal binding site and the cen ter o f the ring o f Tyrz is approximately 7Ä . The cavity that constitutes the binding site for TyrD is com posed o f residues from the D 2 protein. Its character is more hydrophobic than the Tyrz site and the environment around TyrD lacks the cluster o f putative metal binding side chains. | | | |
Reference
| Z. Naturforsch. 46c, 765 (1991); received March 13 1991 | | | |
Published
| 1991 | | | |
Keywords
| Photosystem II, D1 Protein, D 2 Protein, Tyrosine, M anganese, Reaction Center | | | |
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| default:Reihe_C/46/ZNC-1991-46c-0765.pdf | | | | Identifier
| ZNC-1991-46c-0765 | | | | Volume
| 46 | |
| 5 | Author
| Gudrun Wälzlein, ElfriedeK. Pistorius | Requires cookie* | | | Title
| Inactivation of Photosynthetic 0 2 Evolution in the Cyanobacterium Anacystis nidulans PCC 6301: Influence of Nitrogen Metabolites and Divalent Cation Concentration | | | | Abstract
| A n investigation about the in vivo inactivation o f photosynthetic water oxidation has been carried out in the cyanobacterium Anacystis nidulans (Synechococcus PC C 6301). Photosystem II and photosystem I activity as well as the relative am ount of the D 1 and manganese stabiliz ing peptide o f photosystem II were determined after growing the cells in nutrient media with variations in the nitrogen source and the concentration of the major divalent cations (M g 2+ and C a :+). The results show a rapid inactivation of water oxidation in A. nidulans in response to nitrogen deficiency and in response to reduced M g:+ and C a2+ concentrations. The inactiva tion o f water oxidation observed under divalent cation deficiency could be greatly accelerated when L-amino acids instead o f am m onia or nitrate were used as nitrogen source. Under these conditions inactivation o f water oxidation correlated with a rapid loss o f D 1 and with a slower loss o f the manganese stabilizing peptide from photosystem II. A possible regulation o f the photosystem II activity in A. nidulans by nitrogen metabolites is suggested. | | | |
Reference
| Z. Naturforsch. 46c, 1024—1032 (1991); received June 26/August 19 1991 | | | |
Published
| 1991 | | | |
Keywords
| Cyanobacteria, Anacystis nidulans PCC6301, Synechococcus PCC6301, Photosystem II, Photosystem I, Nitrogen Metabolism | | | |
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| default:Reihe_C/46/ZNC-1991-46c-1024.pdf | | | | Identifier
| ZNC-1991-46c-1024 | | | | Volume
| 46 | |
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