Kinesin Processivity

Conventional kinesin is a highly processive motor that can take >100 steps along a microtubule before dissociating. Various lines of evidence have led to a model of hand over hand processive motion, in which the trailing head detaches and rebinds to the next open tubulin dimer site on the same protofilament, leading to an 8-nm movement of the center of mass (Svoboda and Block 1994; Hancock and Howard 1998). Biochemical evidence for an alternating mechanism in which the ATPase cycles on the two heads are out of phase (Hackney 1994; Ma and Taylor 1997; Gilbert et al. 1998) supports the hand over hand mechanism. Processivity is a competition between the detachment and rebinding of one head in order to take a step, and the rate of dissociation of the complex while only...