Inhibition of ATPase activity of Escherichia coli ATP synthase by polyphenols

We have studied the inhibitory effect of five polyphenols namely, resveratrol, piceatannol, quercetin, quercetrin, and quercetin-3-β-d glucoside on Escherichia coli ATP synthase. Recently published X-ray crystal structures of bovine mitochondrial ATP synthase inhibited by resveratrol, piceatannol, and quercetin, suggest that these compounds bind in a hydrophobic pocket between the γ-subunit C-terminal tip and the hydrophobic inside of the surrounding annulus in a region critical for rotation of the γ-subunit. Herein, we show that resveratrol, piceatannol, quercetin, quercetrin, or quercetin-3-β-d glucoside all inhibit E. coli ATP synthase but to different degrees. Whereas piceatannol inhibited ATPase essentially completely (～0 residual activity), inhibition by other compounds was partial with ～20% residual activity by quercetin, ～50% residual activity by quercetin-3-β-d glucoside, and ～60% residual activity by quercetrin or resveratrol. Piceatannol was the most potent inhibitor (IC₅₀ ～14 μM) followed by quercetin (IC₅₀ ～33 μM), quercetin-3-β-d glucoside (IC₅₀ ～71 μM), resveratrol (IC₅₀ ～94 μM), quercitrin (IC₅₀ ～120 μM). Inhibition was identical in both F₁F_o membrane preparations as well as in isolated purified F₁. In all cases inhibition was reversible. Interestingly, resveratrol and piceatannol inhibited both ATPase and ATP synthesis whereas quercetin, quercetrin or quercetin-3-β-d glucoside inhibited only ATPase activity and not ATP synthesis.