The Origin of Minus-end Directionality and Mechanochemistry of Ncd Motors
Figure 6
Mechanochemical cycle for Ncd motor.
In solution, Ncd exists in (i) symmetric and two asymmetric states (either (ii) or (ii)’). On the MTs, Ncd in φ-ADP state exists predominantly in (iii) symmetric plus-end directed conformer. ATP binding stabilizes (iv) asymmetric conformer, which gives rise to minus-end-directed stroke. Finally, the ATP hydrolysis returns the Ncd to the ADP-ADP state that has weak MT-binding affinity; thus Ncd dissociates from MT to the solution. The free energy (F(z)) profile of the power stroke step which is calculated by taking stalk tip position (z) on MT as order parameter is also shown in the same figure.