title: Dynamic polymorphism of single actin molecules in the actin filament.
abstract: Actin filament dynamics are critical in cell motility. The structure of actin filament changes spontaneously and can also be regulated by actin-binding proteins, allowing actin to readily function in response to external stimuli. The interaction with the motor protein myosin changes the dynamic nature of actin filaments. However, the molecular bases for the dynamic processes of actin filaments are not well understood. Here, we observed the dynamics of rabbit skeletal-muscle actin conformation by monitoring individual molecules in the actin filaments using single-molecule fluorescence resonance energy transfer (FRET) imaging with total internal reflection fluorescence microscopy (TIRFM). The time trajectories of FRET show that actin switches between low- and high-FRET efficiency states on a timescale of seconds. If actin filaments are chemically cross-linked, a state that inhibits myosin motility, the equilibrium shifts to the low-FRET conformation, whereas when the actin filament is interacting with myosin, the high-FRET conformation is favored. This dynamic equilibrium suggests that actin can switch between active and inactive conformations in response to external signals.
authors.affiliation: Formation of Soft Nanomachines, Core Research for Evolution Science and Technology, Japan Science and Technology Agency, Suita, Osaka, 563-0871, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kozuka
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yokota
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Arai
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ishii
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins / Q000737:chemistry*; D000818:Animals; D031541:Fluorescence Resonance Energy Transfer; D051379:Mice; D008856:Microscopy, Fluorescence; D018482:Muscle, Skeletal; D024701:Myosin Type V / Q000737:chemistry; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D000199:Actins; D024701:Myosin Type V