Availability of monovalent and divalent cations within intact chloroplasts for the action of ionophores nigericin and A23187.
1. A23187 will uncouple electron transport by broken chloroplasts in a divalent cation dependent manner provided that they have been treated with a low concentration of EDTA. 2. A23187 stimulates oxaloacetate-dependent oxygen evolution and inhibits phosphoglycerate reduction by intact chloroplasts isolated in a cation-free medium whereas the full effect of nigericin was dependent on the presence of external K+. 3. Uncoupling of oxaloacetate reduction by A23187 in intact chloroplasts is inhibited by EDTA and this effect is overcome by excess Mg2+. 4. The results suggest that divalent and not monovalent cations are available for collapsing the light-induced H+ gradient within the intact organelle.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology*; D002736:Chloroplasts / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D005292:Ferricyanides / Q000494:pharmacology; D005988:Glyceric Acids / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D009550:Nigericin / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000378:metabolism; D010071:Oxaloacetates / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D005292:Ferricyanides; D005988:Glyceric Acids; D009943:Organophosphorus Compounds; D010071:Oxaloacetates; D000001:Calcimycin; D004492:Edetic Acid; D008274:Magnesium; D009550:Nigericin; D011188:Potassium; D010100:Oxygen