| | 2 | Author
| G. O., G. S. Chäfer, H. S. Tro, Tm An | Requires cookie* | | | Title
| Synthesis of 2'-/3'-0-Acylated Adenine Nucleotide Analogs and Their Interactions in Photophosphorylation  | | | | Abstract
| By mono esterification o f 3'(2')-hydroxyl residues o f adenine nucleotides with various carb-oxylic acids a series o f nucleotide analogs is available including fluorescent and photoaffinity labels. Their chemical synthesis is described. The equilibrium between 2' and 3' esters is determined by N M R spectroscopy, stability o f the esters and their tendency o f acyl migration is discussed. The interaction o f the A D P derivatives with the chloroplast ATP synthesizing system is in vestigated. Actually, the analogs are typical energy transfer inhibitors, strongly inhibiting photo phosphorylation and concom itant coupled electron transport (ci50 values ranging from 0.3 to 85 |iM). On the basis o f inhibitory activities o f analogs bearing varying 3'-(2')-substituents, struc-ture-activity relationships are discussed. The inhibitory properties o f the em ployed A D P analogs are based on their specific interaction with the catalytic AD P binding site o f CF] and their extrem ely slow phosphorylation on the enzyme (rate 0.25% or less com pared to A D P phosphorylation). Inhibition is com petitive to AD P but non-com petitive with regard to P; . It is specific for the A D P derivatives, whereas the corresponding ATP analogs are only weak inhibitors in phosphorylation and the AMP derivatives are com pletely inactive. In light-triggered ATP hydrolysis, however, the ATP analogs exhibit an even stronger com petitive inhibition than the A D P derivatives. The results suggest that a conformational change o f ATPase takes place when the chloroplasts are transferred from energized to de-energized conditions which greatly affects the properties o f the active site with respect to nucleotide binding. In tro d u c tio n | | | |
Reference
| Z. Naturforsch. 38c, 49 (1983); received October 7 1982 | | | |
Published
| 1983 | | | |
Keywords
| N ucleotide Analogs, Photophosphorylation, Energy Transfer Inhibition | | | |
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| default:Reihe_C/38/ZNC-1983-38c-0049.pdf | | | | Identifier
| ZNC-1983-38c-0049 | | | | Volume
| 38 | |
| 3 | Author
| Bernhard Huchzermeyer, Andreas Löhr | Requires cookie* | | | Title
| Diphenyl Ether Herbicides, a Tool to Elucidate the Mechanism of Photophosphorylation | | | | Abstract
| At least two different classes of A DP binding sites on chloroplast coupling factor are de scribed in the literature. High-affinity sites are assumed to entail regulatory functions while low-affinity sites are involved in catalysis. Diphenyl ether herbicides, acting as energy transfer inhibitors, interfere with nucleotide ex change on both categories of A D P binding sites. Their inhibitory potency varies depending on their substitution. We found that each diphenyl ether assayed revealed identical / 50 values for inhibition of nucleotide interaction with both classes of binding sites. We show here that diphenyl ether inhibition of energytransfer is primary based upon the interference with A DP binding to high-affinity binding sites. Thereby the control of proton permeability through the coupling factor complex is affected. Moreover, we found that the three ß-subunits are not absolutely fixed in one conformational state: After covalently block ing the high-affinity site by an azido-label, a new ß-subunit. | | | |
Reference
| Z. Naturforsch. 45c, 552—557 (1990); received October 10 1989 | | | |
Published
| 1990 | | | |
Keywords
| Diphenyl Ethers, Energy-Transfer Inhibition, Nitrofen, Photophosphorylation, Coupling Factor | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0552.pdf | | | | Identifier
| ZNC-1990-45c-0552 | | | | Volume
| 45 | |
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