Photophosphorylation in Digitonin Subchloroplast Particles: ABSENCE OF A LIGHT-INDUCED pH SHIFT

Abstract

Abstract Subchloroplast particles were prepared by incubation with digitonin and differential centrifugation. Such particles show a high rate of cyclic photophosphorylation but have little or no capacity to form the reversible, light-dependent pH gradient. They also have no activity in the formation of the nonphosphorylated high energy intermediate, in acid-base phosphorylation, and in light-induced absorbance change. ATP formation in these particles is insensitive to amines, nigericin plus KCl, and low concentrations of Triton X-100. It is inhibited by atebrin, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, and citrate. It is concluded from the above and from other experimental results that the light-induced formation of a pH differential in chloroplasts is secondary to and in equilibrium with a postulated high energy intermediate. A mode of action for various uncouplers in photophosphorylation in chloroplasts is suggested.