DIRECT OBSERVATION OF THE ROTATION OF EPSILON-SUBUNIT IN F-1-ATPASE

Rotation of the epsilon subunit in F-1-ATPase from thermophilic Bacill us strain PS3 (TF1) was observed under a fluorescence microscope by th e method used for observation of the gamma subunit rotation (Noji, H., Yasuda, R., Yoshida, M., and Kinosita, K., Jr. (1997) Nature 386, 299 -302). The alpha(3)beta(3)gamma epsilon complex of TF, was fixed to a solid surface, and fluorescently labeled actin filament was attached t o the epsilon subunit through biotin-streptavidin. In the presence of ATP, the filament attached to epsilon subunit rotated in a unidirectio n. The direction of the rotation was the same as that observed for the gamma subunit. The rotational velocity was slightly slower than the f ilament attached to the gamma subunit, probably due to the experimenta l setup used. Thus, as suggested from biochemical studies (Aggeler, R. , Ogilvie, I., and Capaldi, R. A. (1997) J. Biol. Chem. 272, 19621-196 24), the epsilon subunit rotates with the gamma subunit in F-1-ATPase during catalysis.