ATP synthase (F-ATPase) function depends upon catalytic and rotation cycles of the F-1 sector. Previously, we found that F-1 ATPase activity is inhibited by the dietary polyphenols, curcumin, quercetin, and piceatannol, but that the inhibitory kinetics of curcumin differs from that of the other two polyphenols (Sekiya et al., 2012, 2014). In the present study, we analyzed Escherichia coli F-1 ATPase rotational catalysis to identify differences in the inhibitory mechanism of curcumin versus quercetin and piceatannol. These compounds did not affect the 120 rotation step for ATP binding and ADP release, though they significantly increased the catalytic dwell duration for ATP hydrolysis. Analysis of wild-type F-1 and a mutant lacking part of the piceatannol binding site (gamma Delta 277-286) indicates that curcumin binds to F-1 differently from piceatannol and quercetin. The unique inhibitory mechanism of curcumin is also suggested from its effect on F-1 mutants with defective beta-gamma subunit interactions (gamma Met23 to Lys) or beta conformational changes (beta Ser174 to Phe). These results confirm that smooth interaction between each beta subunit and entire gamma subunit in F-1 is pertinent for rotational catalysis. (C) 2014 Elsevier Inc. All rights reserved.