ATP formation caused by acid-base transition of spinach chloroplasts.

Abstract

Previous workl-5 has shown the existence of a high-energy condition of isolated chloroplasts, caused by illumination in the absence of phosphate or ADP. This state is inferred from the ability to form ATP in the postillumination darkness. Accompanying the condition is an apparent uptake of hydrogen ions6z I together with an excretion of Mg++ or other cations.8 A feasible interpretation, stemming from the "chemi-osmotic" hypothesis for the mechanism of phosphorylation in double membrane containing organelles,9' 10 is that illumination causes the uptake of hydrogen ions into the inner space of the grana disk double membranes. The resulting inequality in hydrogen ion electrochemical activity across the membrane is postulated to be, in itself, the high-energy condition, able to drive the formation of ATP. If this interpretation is correct, then the same high-energy condition should be formed artificially, entirely in the dark and without electron transport, by loading the inner space of the grana disk membranes with protons. If this could be accomplished by placing chloroplasts in an acid medium, when first returned to pH 8 they might be expected to make some ATP due to the pH gradient across the membranes. The operational formation of ATP in this manner, entirely in the dark, was discovered and noted briefly earlier.4 The present paper represents an extension and further exploration of this phenomenon of "acid-bath" dark phosphorylation by chloroplasts. Materiats and Methods.-Chloroplasts were prepared from market spinach as described pre

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

“…Spinach chloroplast fragments with a high volume to surface ratio were prepared by osmotic shock as previously described [4] by washing whole chloroplasts in a medium containing impermeant osmotic supports such as 10 mM sodium succinate and 0.1 n-M tricine pH 8.0 or 10 mM sucrose containing 1 mM MgCl, and 0.1 mM sodium tricine at pH 8.0. The washed chloroplasts were resuspended in the above solutions for use in the experiments described herein.…”

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H+‐ATPase from chloroplasts

“…This electrochemical potential difference of protons, ~x+. gives rise to a proton flux across the membra.ne, and the membrane-bound H +-ATPase can use the energy front this "down-hill" proton flux for synthesis of ATE ATP synthesis in chloroplasts can be driven by an artificially generated ApH (acid-base-transition [3]7 and dr/ (extental electric field [4] during the reaction time. Here, we measured the initial rate of" ATP synthesis with a rapid-mixing quenchedflow apparatus [5].…”

Berger C. Mayne (1920–2011): a friend and his contributions to photosynthesis research

“…At about this time, Jagendorf and Uribe (1966) reported that chloroplasts could form ATP without illumination if they were incubated briefly in a low pH medium (acid) followed by quick addition of a base. The acid-base transition was believed to have created a proton concentration difference across the thylakoid membrane.…”