Abstract
Actin filaments are the most abundant components of the cellular cytoskeleton,and they play critical roles in various cellular functions,including migration,division,and shape control.During these activities,mechanical tension causes structural changes in the double-helical structure of an actin filament,which is a key modulator of cytoskeletal reorganization.In this study,we performed large-scale molecular dynamics(MD),and steered MD simulations to quantitatively analyze the effects of tensile force on the mechanical behavior of an actin filament.These results revealed that when a tensile force of 200 pN was applied to a filament comprising 14 actin subunits,the filament twist angle decreased by approximately 20°,which corresponded to a rotation of approximately -2° per subunit,indicating a critical structural change in the actin filament.Based on these structural changes,the variation in the filament length and twist angle decreased,resulting in increased extensional and torsional stiffness.Torsional stiffness significantly increased under these tensile conditions,and the ratio of filament stiffness under a tensile force to that under no external force increased significantly at longer temporal scales.These results will contribute to understanding the mechanochemical interactions involved in actin dynamics by showing that increased tensile force in the actin filament prevents actin regulatory proteins from binding to the filament.
