The light-intensity-dependence of the efficacy of 2-(3-chloro-4-trifluoromethyl)-anilino-3,5-dinitrothiophene (Ant2p) to inhibit the photosystem 2 reactions of chloroplasts.
The mechanism by which Ant2p [2-(3-chloro-4-trifluoromethyl)anilino-3, 5-dinitrothiophene] inhibits the oxygen evolution capacity of chloroplasts is thought to be due to a rapid reduction of the S2 and S3 oxidation states of the oxygen-evolving complex mediated by the oxidation of endogenous donors such as cytochrome b559. The results presented in this paper show that the degree of inhibition by Ant2p of the photosystem 2-supported electron transfer reactions, registered by the light-dependent rate of dichlorophenolindophenol reduction, varies according to the actinic light intensity. Moreover, a similar intensity-dependence can be detected in the extent of the Ant2p-induced cytochrome b559HP photo-oxidation. We show, however, that the dependence of the cytochrome oxidation is not due to the oxidation per se, but reflects changes in the high light-driven re-reduction reaction. The close correlation between the two Ant2p reactions is interpreted as indicating that the effect of Ant2p might be due to an inhibition of the S-state turnovers and not necessarily due to a deactivation process.
D015086:2,6-Dichloroindophenol / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D003573:Cytochrome b Group / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D005976:Glutaral / Q000494:pharmacology; D008027:Light; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000037:antagonists & inhibitors*; D013053:Spectrophotometry; D013876:Thiophenes / Q000494:pharmacology*
D003573:Cytochrome b Group; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D013876:Thiophenes; C003891:ANT 2p; C019313:cytochrome b559; D015086:2,6-Dichloroindophenol; D005976:Glutaral