Actin–actin bond strength and the conformational change of F -actin 1

Abstract

Experimental data on the elastic modulus for bending of F-actin are summarized and the microscopic elastic constant of the actin-actin bond is estimated. The elastic modulus for bending is ca. 2 × 10⁻¹⁷ dyne cm² and the microscopic elastic constant is ca. 2 × 10⁴ dyne cm 1 in the physiological salt condition at room temperature. A profile of the interaction free energy is given as a function of the distance between actin monomers, and the thermodynamic property of the bond is discussed. Then, data are presented to show the conformational change of F-actin in the thin filament induced by Ca ion and by interaction with myosin or heavy meromyosin. Finally, the possibility that the conformations change of F-actin is involved in muscle contraction or cellular movement and its regulation is suggested.