The γ subunit in chloroplast F1‐ATPase can rotate in a unidirectional and counter‐clockwise manner

Abstract
Rotation of the γ subunit in chloroplast F1‐ATPase (CF1) was investigated by using a single molecule observation technique, which is developed by Noji et al. to observe the rotation of a central γ subunit portion in the α3β3γ sub‐complex of F1‐ATPase from thermophilic Bacillus PS3 (TF1) during ATP hydrolysis [Noji, H. et al. (1997) Nature 386, 299–302]. We used two cysteines of the γ subunit (Cys‐199 and Cys‐205) of CF1‐ATPase, which are involved in the regulation of this enzyme, to fix the fluorochrome‐labeled actin filament. Then we successfully observed a unidirectional, counter‐clockwise rotation of the actin filament with the fluorescent microscope indicating the rotation of the γ subunit in CF1‐ATPase. We conclude that the rotation of the γ subunit in the F1‐motor is a ubiquitous phenomenon in all F1‐ATPases in prokaryotes as well as in eukaryotes.