Fig. 1.

Mechanical activation of the ADP-inhibited F₁ with magnetic tweezers. (a) Side and top views of the manipulation system with magnetic tweezers. The ≈0.6-μm magnetic beads were attached to the γ-subunit in the F₁ immobilized on the slide glass. The magnetic tweezers were mounted on the microscope 10 mm above the specimen stage to generate a magnetic field parallel to the stage. (b) Time course of the mechanical activation by pushing in the forward direction. After a 120° stepping rotation that can be seen as an oscillating trace, the F₁ spontaneously lapsed into the ADP-inhibited form at 280°. The F₁ was stalled and released at +10°, +20°, +30°, and +40° from the angle for inhibition with magnetic tweezers. After a +40° stalling, the F₁ regained active rotation. Red areas indicate the manipulation time by using the magnetic tweezers. (c) Trial of the mechanical activation by pulling in the backward direction. The F₁ was not activated when stalled and released at –20°, –40°, and –80° with magnetic tweezers. To confirm that it was alive, it was activated by being pushed >+80°.