F1-ATPase: A Rotary Motor Made of a Single Molecule




To observe rotation, the three β subunits were fixed on a glass surface through histidine tags engineered at the N terminus.  To the putative rotor subunit γ, a μm-sized actin filament was attached through streptavidin.  When ATP was added, the actin filament rotated continuously clockwise (movie).  Note that, in this movie, the rotation occurs around the middle of the filament.  If you hold an end of a long rod, you could make a fake rotation by twisting your wrist.  If you hold the middle, however, you have to rotate yourself to keep the rod rotating.  Thus, the propeller rotation in this movie shows that the γ subunit really slides against the surrounding α3β3 subunits over infinite angles.
                                                            Noji, H. et al., Nature 386, 299-302 (1997).