The Relationship of DCCD-Membrane Interaction to Coupling Factor Function in the Proton Pump

Abstract

The experiments of MCCARTY and RACKER showed that the protein (CF₁) extracted from spinach chloroplasts by EDTA-washing is functional as a Ca⁺⁺ ATPase and their immunochemical experiments showed that this protein is identical to the grana-bound Mg+ + ATPase and the enzyme responsible for coupling ATP synthesis to electron flow. Their work implicated this protein in the proton uptake reaction; however, their results and subsequent investigations on energy transfer inhibition have shown that the transphosphory1 at ion function of this protein is not essential to the proton pump (MCCARTY & RACKER 1965, IZAWA & HIND 1967, URIBE 1970). The experiments reported by URIBE and JAGENDORF demonstrated that CF₁ is not essential to the physical properties of the grana membranes as determined by osmotic response (URIBE & JAGENDORF 1968); thus the CF₁-membrane interaction was thought to be specifically related to the proton permeability of the grana membrane. Coupling factor (CF₁) binding could reduce proton permeability thereby producing or maintaining and energetic state which could be expressed as proton accumulation and phosphorylation under appropriate experimental conditions.