ATP synthesis driven by a K⁺‐valinomycin‐induced charge imbalance across chloroplast grana membranes

ATP synthesis driven by a protonmotive force inStreptococcus lactis

“…In these organelles formation of ATP also occurs when an insufficiently large pH gradient is supplemented with the electrical potential generated by potassium movements in the presence of valinomycin. This has been shown in cases where the suboptimal pH gradient was established by either a limited acid-base transition (Schuldiner, Rottenberg & Avron, 1972;Uribe, 1973;Uribe & Li, 1973) or by prior illumination (Schuldiner et al, 1972(Schuldiner et al, , 1973. Comparable results have recently been obtained using chromatophores from Rhodospirillum rubrurn (Schuldiner et al, 1973;Leiser & Gromet-Elhanan, 1974;Gromet-Elhanan & Leiser, 1975).…”

ATP synthesis by the F1Fo ATP synthase of Escherichia coli is obligatorily dependent on the electric potential

“…With a calculated K + /valinomycin diffusion potential of 100 mV and no ΔpH, ATP was synthesized at an initial rate of 1/s, whereas no ATP was formed with a calculated ΔpH of 194 mV [pH in =5.0 (MES); pH out =8.3 (glycylglycine)] and no ΔΨ. These results are in contrast to the general view that ΔpH and ΔΨ are kinetically equivalent driving forces for ATP synthesis, where one parameter of sufficient magnitude can completely compensate for the other [5–10]. In a previous study with the E. coli enzyme, Fischer et al [14]were unable to demonstrate ATP synthesis in the absence of ΔpH.…”

“…In a classical study with the ATP synthase of chloroplasts Jagendorf and Uribe [5]reported that ATP was synthesized following an acid/base transition with succinate, pH 4 as the acidic and Tris, pH 8 as the basic buffer. Alternatively, ATP formation could be energized by a potassium diffusion potential [6]and its rate depended apparently equally on ΔpH and ΔΨ [7]. Kinetic equivalence of ΔpH and ΔΨ for driving ATP synthesis was also reported for other ATP synthases [8–10].…”

Membrane‐bound ATP synthesis generated by an external electrical field

“…The reaction medium contained 10 -2 M tricine adjusted to pH 7 or pH 8 with NaOH fig.l), the yield and rate in respect to the effective area is even higher. The yield obtained with an imposed diffusion potential (see Introduction) which maintains probably one second across the membrane is at ApH = 0 about 6 • 10 --4 Mol ATP/Mol Chl [15]. If we assume that there exists one ATPase per 860 chlorophyll molecules [19] at least 6.5 ATP molecules were synthesized per ATPase by the external electrical pulses.…”

“…ATP formation by an artificial electrical potential difference set up with a K÷-gradient across the membrane gave reasonable yields only when this gradient was superimposed on a preexisting pH gradient of ApH >~ 1-3 [13,14]. At ApH = 0 the generated amount of ATP is extremely small [ 15] (see Discussion). The purpose of the present work is to prove if phosphorylation can be induced by an external electrical field.…”