Phenomenological analysis of ATP dependence of motor protein

TL;DR

This paper presents a phenomenological analysis of motor protein velocity dependence on ATP concentration, proposing a Michaelis-Menten like model that fits experimental data across various load conditions, revealing differences in ATP affinity.

Contribution

It introduces a new phenomenological model for motor protein velocity that accounts for ATP dependence and load conditions, validated by experimental data fitting.

Findings

Velocity ratio is invariant across load types.

Motor velocity follows a Michaelis-Menten like formula.

ATP affinity varies with load conditions.

Abstract

In this study, through phenomenological comparison of the velocity-force data of processive motor proteins, including conventional kinesin, cytoplasmic dynein and myosin V, we 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 motor can be well approximated by a Michaelis-Menten like formula $V=\atp k(F)L/(\atp +K_M)$, with $L$ the step size, and $k(F)$ the external load $F$ dependent rate of one mechanochemical cycle of motor motion in saturated ATP solution. The difference of Michaelis-Menten constant $K_M$ for substall, superstall and negative external load indicates, the ATP molecule affinity of motor head for these three cases are different, though the expression of $k(F)$ as a function of $F$ might be unchanged for any external load $F$. Verifications of this Michaelis-Menten like formula has also been done by fitting to the recent experimental data.