Control of ATP hydrolysis in chloroplasts

• Published in: FEBS letters 1987-09, Vol.221 (2), p.265-269
• Main Authors: Strotmann, Heinrich, Kleefeld, Sigrid, Lohse, Detlev
• Format: Article
• Language: English
• Subjects: 9-Aminoacridine fluorescence; ATP; ATP synthesis; ATPase; Biological and medical sciences; Cell structures and functions; Chloroplast; Chloroplast, photosynthetic membrane and photosynthesis; chloroplasts; DTT, dithiothreitol; Fundamental and applied biological sciences. Psychology; Kinetic control; Molecular and cellular biology; PMS, phenazine methosulfate; Spinacea oleracea; Spinach
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(87)80938-9

Dark ATP hydrolysis catalysed by the membrane-bound preactivated thiol-modified chloroplast ATPase was measured at constant initial ATP concentration and constant initial phosphate potential c ATP/ c ADP·c P i which was adjusted by inverse variation of the concentrations of ADP and P i. Under these conditions, the rate of ATP hydrolysis is strongly inhibited as the concentration of ADP is increased and the concentration of P i is decreased. Inhibition is preferentially caused by ADP-dependent inactivation of ATPase molecules. At low initial ADP concentration, the transmembrane proton gradient generated by effective ATP hydrolysis protects the enzyme from deactivation in spite of progressive accumulation of ADP because energy-dependent release of ADP counteracts its binding. Deactivation due to incorporation of ADP occurs, however, when the proton gradient decreases as a consequence of exhaustion of substrate ATP.