Novel intermolecular surface force unveils the driving force of the actomyosin system

Abstract

In this chapter, we discuss the role of water in actomyosin-force generation. We have been investigating the hydration properties of ions, organic molecules, and proteins. These studies revealed that actin filaments (F-actin) are surrounded by a hyper-mobile water (HMW) layer and restrained water layer, while myosin subfragment 1 (S1) has only a typical restrained hydration layer. The understanding of the physicochemical properties of HMW has been greatly advanced by recent theoretical studies on statistical mechanics and solution chemistry. To explain the mechanism of force generation of actomyosin using ATP hydrolysis, we propose a driving force hypothesis based on novel intermolecular surface force. This hypothesis is consistent with the reported biochemical kinetics and thermodynamic parameters for the primary reaction steps. The gradient field of solvation free energy of S1 is generated in close proximity to F-actin.