Oxford Molecular Motors

Abstract:

The torque generated by the power stroke of Escherichia coli F(1)-ATPase was determined as a function of the load from measurements of the velocity of the gamma-subunit obtained using a 0.25 micros time resolution and direct measurements of the drag from 45 to 91 nm gold nanorods. This result was compared to values of torque calculated using four different drag models. Although the gamma-subunit was able to rotate with a 20x increase in viscosity, the transition time decreased from 0.4 ms to 5.26 ms. The torque was measured to be 63+/-8 pN nm, independent of the load on the enzyme.

Abstract:

Bacterial motility is arrested when a protein that acts as a clutch disables rotation of the flagellar motor.

Abstract:

We report a novel method to detect angular conformational changes of a molecular motor in a manner sensitive enough to achieve acquisition rates with a time resolution of 2.5mus (equivalent to 400,000fps). We show that this method has sufficient sensitivity to resolve the velocity of the F(1)-ATPase gamma-subunit as it travels from one conformational state to another (transition time). Rotation is detected via a gold nanorod attached to the rotating gamma-subunit of an immobilized F(1)-ATPase. Variations in scattered light intensity allow precise measurement of changes in angular position of the rod below the diffraction limit of light.