Cl- channel inhibitors of the arylaminobenzoate type act as photosystem II herbicides: a functional and structural study.
The Cl- channel blocker NPPB (5-nitro-2-(3-phenylpropylamino) benzoic acid) inhibited photosynthetic oxygen evolution of isolated thylakoid membranes in a pH-dependent manner with a K(i) of about 2 microM at pH 6. Applying different electron acceptors, taking electrons either directly from photosystem II (PS II) or photosystem I (PS I), the site of inhibition was localized within PS II. Measurements of fluorescence induction kinetics and thermoluminescence suggest that the binding of NPPB to the QB binding site of PS II is similar to the herbicide DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea). The effects of different arylaminobenzoate derivatives and other Cl- channel inhibitors on photosynthetic electron transport were investigated. The structure--activity relationship of the inhibitory effect on PS II shows interesting parallels to the one observed for the arylaminobenzoate block of mammalian Cl- channels. A molecular modeling approach was used to fit NPPB into the QB binding site and to identify possible molecular interactions between NPPB and the amino acid residues of the binding site in PS II. Taken together, these data give a detailed molecular picture of the mechanism of NPPB binding.
Institut für Biologie II, Biochemie der Pflanzen, Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany.
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Bock
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Krieger-Liszkay
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Beitia Ortiz de Zarate
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Schönknecht
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D001667:Binding, Competitive; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D006540:Herbicides / Q000737:chemistry* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008163:Luminescent Measurements; D008958:Models, Molecular; D009579:Nitrobenzoates / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D010100:Oxygen / Q000037:antagonists & inhibitors / Q000378:metabolism; D018532:Pisum sativum; D010782:Photolysis / Q000187:drug effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D018724:Spinacia oleracea; D013329:Structure-Activity Relationship; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism
D018118:Chloride Channels; D006540:Herbicides; D009579:Nitrobenzoates; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010100:Oxygen