The two-headed motor protein kinesin hydrolyzes nucleotide to move uni
directionally along its microtubule track at speeds up to 1000 nm/s (S
axton et al., 1988) and develops forces in excess of 5 pN (Hunt et al.
, 1994; Svoboda et al., 1994a). Individual kinesin molecules have been
studied recently in vitro, and their behavior has been characterized
in terms of force-velocity curves and variance measurements (Svoboda a
nd Block, 1994a; Svoboda et al., 1994b). We present a model for force
generation in kinesin in which the ATP hydrolysis reactions are coordi
nated with the relative positions of the two heads. The model explains
the experimental data and permits us to study the relative roles of B
rownian motion and elastic deformation in the motor mechanism of kines
in.