F1-ATPase obtained from mesophilic organisms is inhibited by specific inhibitors, such as aurovertin, efrapeptin, quercetin and several local anesthetics. This property has been explained by the common structure at the catalytic center of F1. However thermophilic F1 (TF1), which has the same primary structure at the center as other F1's, was shown to be resistant to these F1-specific inhibitors. Thus, the inhibitory mechanism may be explained not by the common structure at the catalytic site, but by some conformational changes of the flexible mesophilic F1 molecules or the absence of an inhibitor binding site in thermophilic F1.