ATP synthesis reappeared when FI was reconstituted back(the solubilized F, alone can catalyze ATP hydrolysis, thus was originally named as F,ATPase) f was the first essential factor identified for oxidative phosphorylation• ATP synthesis reappeared when F1 was reconstituted back (the solubilized F1 alone can catalyze ATP hydrolysis, thus was originally named as F1ATPase). • F1 was the first essential factor identified for oxidative phosphorylation