ATP-Driven Mechanical Work Performed by Molecular Motors

Synonyms

Molecular motors

Introduction

Most biological molecular motors perform work by utilizing the free energy released in the turnover of adenosine triphosphate (ATP). The free energy, ΔG_ATP “(conveniently expressed per molecule in units of kT, where k is the Boltzmann constant and T is the absolute temperature),” is attributed to the instability of the γ-phosphate bond and varies with the concentrations of substrate (ATP; or rather MgATP) and product (ADP and inorganic phosphate, P_i) as follows:

$$ \Delta {\mathrm{G}}_{\mathrm{ATP}}=\Delta {{\mathrm{G}}_{\mathrm{ATP}}}^{{}^{\circ}}+\mathrm{kT}\ \ln \frac{\left[\mathrm{ADP}\right]\left[{\mathrm{P}}_{\mathrm{i}}\right]}{\left[\mathrm{ATP}\right]} $$

where ΔG_ATP° ≈ −14 kT is the standard free energy. Under physiological conditions, [ATP] ≈ 1–10 mM, [ADP] ≈ 10 μM, and [P_i] ≈ 1 mM, that is, the concentrations are far from equilibrium (due to oxidation of food components), a precondition for the high power output and efficiency of...