Figure 1.

Kinetic race scheme from Mickolajczyk and Hancock (1), providing a model for how long kinesin can walk before falling off the microtubule. (A) Shown here is a schematic of a microtubule-bound kinesin dimer, highlighting key architectural elements including the neck linkers as well as the gold nanoparticle label used for iSCAT tracking (see text). (B) By localizing the gold nanoparticle with high spatial and temporal resolution, iSCAT can discriminate between bound and unbound states of the labeled kinesin motor domain. (C) Shown here is a schematic of the stepping cycle of kinesin, highlighting the key findings of Mickolajczyk and Hancock (1). Kinetic race: the one-head-bound ADP•P_i state is identified as a vulnerable state, from which either 1) a successful forward step is made or 2) the motor detaches to end the processive run. First passage ADP release: when the ADP-bound, tethered head of kinesin initially steps forward, it hangs onto the microtubule long enough for ADP release to lock it into place—thus minimizing reversions to the vulnerable state. To see this figure in color, go online