ATP synthase is independent of the electrochemical potential generating proteins. In the words of the text: generation and utilization of chemiosmotic mechanism are independent. An experiment confirming this was done by E. Racker and W. Stoeckenius in which an artificial system resembling an ATP factory was constructed. Artificial lipid bilayers with the light-driven proton pump, bacteriorhodopsin from a bacterium, was confirmed as generating a pH gradient in response to light. A foreign ATP synthase from beef heart was added. With these two elements ATP was synthesized when the experiment was exposed to light. Because of the very different nature and source of the two proteins it was concluded that the two events are independent.