Light-induced Mg2+ ATPase activity of coupling factor in intact chloroplasts.
Intense illumination isolated, intact, spinach chloroplasts triggers the well known proton-pumping Mg2+ ATPase activity of coupling factor, which can be assayed in subsequently lysed chloroplasts by monitoring ATP-driven quenching of 9-aminoacridine fluorescence. The light-triggered ATPase activity decays slowing in the dark and is inhibited by N,N'-dicyclohexylcarbodiimide. After osmotic lysis and washing of the chloroplasts, preillumination no longer triggers maximal proton-pumping ATPase until methylviologen and dithiothreitol are added to the medium. It is suggested that intact organelles contain soluble or loosely bound cofactors necessary for light-triggering of coupling factor ATPase. On osmotic lysis, these endogenous cofactors are diluted or inactivated and must be replaced by addition of a dithiol reagent and an electron acceptor.
D000251:Adenosine Triphosphatases / Q000378:metabolism* / Q000528:radiation effects; D000609:Aminoacridines; D002736:Chloroplasts / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D008027:Light; D008274:Magnesium / Q000378:metabolism; D010785:Photophosphorylation / Q000528:radiation effects*; D010944:Plants / Q000201:enzymology*; D013050:Spectrometry, Fluorescence
D000609:Aminoacridines; D000251:Adenosine Triphosphatases; D008274:Magnesium; D004229:Dithiothreitol