ATP formation caused by acid-base transition of spinach chloroplasts.
Year: 1966
Type: article
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.8A 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 hy- drogen ions into the inner space of the grana disk double membranes.The resulting inequality in hydrogen ion electrochemical activity across the membrane is postu- lated 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 ac- complished 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 mem- branes.The operational formation of ATP in this manner, entirely in the dark, was discovered and noted briefly earlier.4The present paper represents an extension and further exploration of this phenomenon of "acid-bath" dark phosphoryla- tion by chloroplasts.Materiats and Methods.-Chloroplasts were prepared from market spinach as described pre-
Authors: A T Jagendorf, E Uribe
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1987585417