Uncouplers Release Electron Transport from Phosphorylation

Uncouplers Release Electron Transport from Phosphorylation... 

UiKOupliitg of oxidative phosphorylation. The release of energy in the electron transport chain becomes uncoupled from the formation of energy by the phosplxirylation of adenosine diphosphate (ADP) to ATP. 

Further evidence for the light-driven proton translocation by bacteriorhodopsin was obtained by Racker and Stoeckenius who carried out reconstitution ofthe purple membrane into phospholipid vesicles. In the light, the reconstituted vesicles took up protons from the exterior at a rate of 50-200 ng per mg of bacteriorhodopsin, and released them in the dark. The rate of proton uptake in the fight and release in the dark was accelerated by the addition ofvalinomycin, while uncouplers of oxidative phosphorylation abolished the uptake of protons altogether. Note that the direction of proton transport from outside to the inside of the vesicle reported by the authors was opposite to that observed in intact cells, the possibility that bacteriorhodopsin might be oppositely oriented in cells and vesicles, was subsequently confirmed by freeze-etch electron microscopy. 

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