Phenomenological Analysis of ATP Dependence of Motor Proteins

In this study, through phenomenological comparison of the velocity-force data of processive motor proteins, including conventional kinesin, cytoplasmic dynein and myosin V, I found that, the ratio between motor velocities of two different ATP concentrations is almost invariant for any substall, superstall or negative external loads. Therefore, the velocity of motors can be well approximated by a Michaelis-Menten like formula [Image: see text], with [Image: see text] the step size, and [Image: see text] the external load [Image: see text] dependent rate of one mechanochemical cycle of motor motion in saturated ATP solution. The difference of Michaelis-Menten constant [Image: see text] for substall, superstall and negative external load indicates, the configurations at which ATP molecule can bind to motor heads for these three cases might be different, though the expression of [Image: see text] as a function of [Image: see text] might be unchanged for any external load [Image: see text]. Verifications of this Michaelis-Menten like formula has also been done by fitting to the recent experimental data.