Mechanical Characterization of Myosin II, Actin and Their Complexes by Molecular Mechanics Approach

The knowledge of the mechanical properties of myosin and actin is of a crucial importance in order to better understand the molecular mechanism of sliding force generation in muscle contraction. The aim of our work was to realize a mechanical characterization of myosin II and actin monomer using the molecular mechanics approach, by assessing the elastic properties of the two proteins, and by establishing the interaction forces between the two monomers of the actomyosin complex, and between myosin’s scissure and adenine nucleotides (ATP and ADP). A restraining method was used in order to modify the axial length of the proteins or the intermolecular distances. The interaction force and the stiffness were calculated as first and second order derivative of the potential energy with respect to the applied elongation and intermolecular distance respectively. According to our results, the values of elastic modulus of myosin motor domain and actin are 0.48 GPa, and 0.13 GPa respectively, and myosin-ATP complex is characterized by an attraction force of 130 pN which is twofold greater than the interaction force between myosin and ADP. As for the actomyosin complex, the interaction force has a maximum value of 180 pN. The results of our simulations comply with theoretical and experimental remarks about mechanical properties of myosin II, actin, and their complex.