Effect of nucleotides on potential and pH changes across the thylakoid membrane of spinach chloroplasts

ATP hydrolysis and membrane potential in spinach chloroplasts

“…The resulting 'proton-motive force' is the sum of an electrical (A$) and of a concentration-dependent (ApH) component. In chloroplasts, ATP hydrolysis [2,4] is coupled to an inward transport of H' (ApH) but a concomitant change of the membrane potential (A*) has not yet been evidenced, contrary to what has been observed in other similar systems, mitochondria or bacterial chromotophores.…”

“…Chloroplasts, able to hydrolyse ATP in the darkness, were prepared as in [4]. In brief, freshly harvested spinach leaves were illuminated for 30 min in ice-cold water.…”

“…This ATPase activity has been observed in intact chloroplasts [3] but also in chloroplasts which have lost their external membranes and are freely permeated by nucleotides [4]; the latter chloroplasts, when kept in the dark at O"C, slowly lose their activity in several hours and recover it after a short period of Illumination [4,5].…”

Synthesis of ATP induced in pea chloroplasts by single turnover flashes

“…Type B chloroplasts [16] were prepared as in [14] from freshly harvested, 2-weeks-old pea leaves 'pois nains d'Annonay tr~s hatifs, G. Delbard' which were illuminated for 30 min in ice-cold water before grinding.…”

“…Chloroplasts prepared from pre-illuminated leaves [14] have an active ATPase. A stable pH difference of 1.2 is measured across the thylakoid membranes in the dark from the distribution of the [14C]-methylamine inside and outside the thylakoid.…”