| | 1 | Author
| KatherineE. Steinback, Klaus Pfister, CharlesJ. Amtzen | Requires cookie* | | | Title
| Trypsin-Mediated Removal of Herbicide Binding Sites within the Photosystem II Complex  | | | | Abstract
| Trypsin treatment of isolated chloroplast thylakoids resulted in a step-wise modification o f surface exposed membrane polypeptides. Early effects o f the protease action resulted in a decrease in inhibitory activity of atrazine, diuron, pyrazon, and bromacil, but an initial increase in the activity of bromnitrothymol and dinoseb. Direct measurements o f atrazine binding demonstrated that decreased inhibitory activity corresponded to a decreased binding affinity in the treated membranes. Longer term effects o f trypsin caused removal of atrazine binding sites and a concomitant block o f electron transport chains. The data are consistent with a concept that the traizine receptor protein is a component o f the electron transport chain which is successively degraded in two or more steps by protease attack. Polyacrylamide gel electrophoresis of trypsin-treated membranes and sub-membrane fragments derived from these membranes revealed that several polypeptides are membrane surface exposed. The involvement o f a 32000 dalton polypeptide in creating the atrazine binding site is discussed. | | | |
Reference
| Z. Naturforsch. 36c, 98 (1981); received September 221980 | | | |
Published
| 1981 | | | |
Keywords
| Photosynthesis, Atrazine, Diuron, Chloroplast Membranes, Receptor Protein | | | |
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| default:Reihe_C/36/ZNC-1981-36c-0098.pdf | | | | Identifier
| ZNC-1981-36c-0098 | | | | Volume
| 36 | |
| 3 | Author
| MarcelA K Jansen, ChristoM. Alan, Yoseph Shaaltiel, Jonathan Gressel | Requires cookie* | | | Title
| Mode of Evolved Photooxidant Resistance to Herbicides and Xenobiotics | | | | Abstract
| A few species have evolved resistance to paraquat after repeated selection. As paraquat still inhibited N A D P reduction, we hypothesized that resistance might be due to (a) detoxification o f the paraquat-generated active oxygen species and (b) that resistant plants would have some cross resistance to other xenobiotic oxidants as well as to photoinhibition, which we subse quently demonstrated. The levels o f plastid isozymes o f the oxygen detoxification pathway: (CuZn) superoxide dismutase, ascorbate peroxidase and glutathione reductase were genetical ly higher in the resistant than in the sensitive biotype o f C onyza bonariensis through the F2 generation. Resistance was suppressed by chelators o f copper and/or zinc. Intact chloroplasts from resistant plants had less membrane damage with and without paraquat, than those from sensitive plants. Resistant C onyza plants recover from paraquat inhibition o f photosynthesis in 3 -4 h in high light, whereas sensitive plants died. Both resistant and sensitive plants recov ered from paraquat in 3 -4 h in low light intensities. Paraquat-resistant Conyza plants were cross-tolerant to S 0 2, atrazine, acifluorfen and to photoinhibition. Drought-tolerant maize inbreds were cross-tolerant to paraquat, SO, and acifluorfen (compared to sensitive lines) and they also possessed higher levels o f (Cu/Zn) superoxide dismutase and glutathione reductase. The tolerance to oxidant stresses in C onyza and maize increases with plant age, suggesting that the shift to resistance is a constitutive, earlier expression o f the genes normally expressed later in development. | | | |
Reference
| Z. Naturforsch. 45c, 463 (1990); received November 9 1989 | | | |
Published
| 1990 | | | |
Keywords
| Paraquat, Acifluorfen, Atrazine, Photoinhibition, Superoxide Dismutase | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0463.pdf | | | | Identifier
| ZNC-1990-45c-0463 | | | | Volume
| 45 | |
| 4 | Author
| SimonP M Ackay, PatrickJ. O 'malley | Requires cookie* | | | Title
| Molecular Modelling of the Interactions between Optically Active Triazine Herbicides and Photosystem II | | | | Abstract
| The Q b binding site o f photosystem II in green plants displays stereoselectivity for the (S') stereoisomer o f the a-m ethylbenzyl derivative o f atrazine but not for derivatives with smaller substituents such as sec-butyl. We have shown that interactive models reflect the experimental data by determining the intermolecular energies between the D 1 protein binding region (resi dues Leu 210 to Val 280) and the triazine analogs. The intermolecular energy was calculated by van der W aals and electrostatic interactions after energy minimization o f the combined structures to reduce inter and intramolecular strain. On the basis o f these assumptions the role o f stereoselectivity for optically active triazines was site responsible such stereoselectivity was identified. | | | |
Reference
| Z. Naturforsch. 48c, 474 (1993); received January 13/February 16 1993 | | | |
Published
| 1993 | | | |
Keywords
| Atrazine, Electrostatic Interactions, Intermolecular Energy, Molecular M odelling, Photosystem II | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0474.pdf | | | | Identifier
| ZNC-1993-48c-0474 | | | | Volume
| 48 | |
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