Inhibition of Escherichia coliATP synthase by dietary pomegranate phenolics.

BACKGROUND: A wide range of natural and synthetic compounds bind and inhibit ATP synthase. Dietary polyphenols found in fruits, vegetables, and spices such as tea, olives, grapes, cantaloupes, garlic, and pomegranate possess antimicrobial activities. Dietary pomegranate polyphenols (DPPs) have been shown to exhibit anticancer, antioxidant, and antimicrobial properties. In the current study we are exploring the connection between antimicrobial properties of DPPs and the inhibition of microbial ATP synthase. ATP synthase is the main source of ATP in almost all organisms from bacteria to man. Selective inhibition of bacterial ATP synthase could help in combating microbial infections.

METHODS: Wild type E. coli pBWU13.4 is grown on minimal media to late log phase. Cells are harvested, French Pressed and centrifuged to isolate and purify membrane bound F1 FO ATP synthase. Our null control is E. coli pUC118 with deleted ATPase gene. DPPs and its analogs induced inhibition of wild-type and mutant membrane-bound ATP synthase is performed at room temperature. Wild-type, mutant, and null cell growth assays on limiting glucose are evaluated at OD595 using AccuSkan Plate reader over a period of 24 hours.

RESULTS: Variable oxidative phosphorylation and ATPase activity pattern was observed between wild type phytochemical binding site mutant strains. Western blot showed purity and integrity of wild type and mutant enzymes. DPPs and its analogs caused variable inhibition of ATP synthase. The wild-type enzyme was fully inhibited while mutant enzyme showed variable resistance in presence of DPPs. Variation in the growth pattern was in agreement with the inhibitory profiles of isolated enzymes.

CONCLUSIONS: The inhibitory profiles of isolated E. coli membrane-bound ATP synthase shows that DPPs are potent inhibitors of ATP synthase. Inhibition of E. coli cell growth was also related to DPPs caused ATP synthase inhibition suggesting that ATP synthase is a valuable molecular drug target to combat microbial infection.