The forward and backward stepping processes of kinesin are gated by ATP binding.

The kinesin motor converts the chemical energy from ATP turnover into mechanical work, which produces successive 8-nm steps in the forward and backward direction along a microtubule. A key problem for kinesin mechanochemistry is explaining how ATP turnover is coordinated with mechanical work. We investigated this by measuring the ATP dependent properties of kinesin forward and backward steps using optical trapping nanometry. The results showed that the rate for both forward and backward steps are ATP-dependent, indicating that ATP binding to kinesin triggers both forward and backward steps. This suggests that ATP turnover in kinesin is not rigidly coupled to total mechanical work at high load.