title: Dual action of ionophore A23187 on intact chloroplasts.
abstract: 1. Ionophore A23187 induces uncoupling of potassium ferricyanide-dependent O2 evolution by envelope-free chloroplasts and oxaloacetate-dependent O2 evolution by intact chloroplasts. The half maximal concentration (C1/2) for stimulation of oxygen evolution in both cases is approximately 4 micrometer . 100 microgram chlorophyll . ml-1. 2. Ionophore A23187 also induces inhibition of CO2 and 3-phosphoglycerate-dependent O2 evolution by intact chloroplasts in the presence of 3 mM MgCl2. The half maximal concentrations (C1/2) for inhibition of O2 evolution are 3 micrometer and 5 micrometer respectively . 100 microgram-1 chlorophyll . ml-1. 3. A very high concentration of ionophore A23187 (10 microgram . 20 microgram-1 chlorophyll . ml-1) plus 0.1 mM EDTA lowers the fluorescence yield of intact chloroplasts suspended in a cation-free medium in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, indicating loss of divalent cation from the diffuse double layers of the thylakoid membranes. 4. These results are discussed in relation to ionophore A23187-induced divalent cation/proton exchange at both the thylakoid and the envelope membranes of intact chloroplasts.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects*; D004237:Diuron / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005994:Glycerophosphates / Q000378:metabolism; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D010071:Oxaloacetates / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D005994:Glycerophosphates; D010071:Oxaloacetates; D002245:Carbon Dioxide; D000001:Calcimycin; D004492:Edetic Acid; D004237:Diuron; D008274:Magnesium; D010100:Oxygen