title: Dynamic polymorphism of actin as activation mechanism for cell motility.
abstract: Actin filament dynamics are crucial in cell motility. Actin filaments, and their bundles, networks, and gels assemble and disassemble spontaneously according to thermodynamic rules. These dynamically changing structures of actin are harnessed for some of its functions in cells. The actin systems respond to external signals, forces, or environments by biasing the fluctuation of actin assembly structures. In this study, dynamic conformation of actin molecules was studied by monitoring conformational dynamics of actin molecules at the single molecule level in real time. Actin conformation spontaneously fluctuates between multiple conformational states. Regarding myosin motility, the dynamic equilibrium of actin conformation was interpreted as between states that activates and inhibits the motility. The binding of myosin to actin filaments activates myosin motility by shifting the conformational fluctuation of actin towards the state that activates the motility. Thus, the activation mechanism based on thermal fluctuation is suggested at molecular level as well as at cellular level.
authors.affiliation: Formation of Soft Nanomachines Project, Core Research for Evolution Science and Technology, Japan Science and Technology Agency, Suita, Osaka 565-0871, Japan. kozuka@phys1.med.osaka-u.ac.jp
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: D000199:Actins / Q000737:chemistry* / Q000502:physiology*; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002465:Cell Movement / Q000502:physiology*; D031541:Fluorescence Resonance Energy Transfer; D066298:In Vitro Techniques; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000502:physiology; D046912:Multiprotein Complexes; D009218:Myosins / Q000737:chemistry / Q000502:physiology; D011487:Protein Conformation; D011817:Rabbits; D049490:Systems Biology; D013816:Thermodynamics
chemical_list: D000199:Actins; D020409:Molecular Motor Proteins; D046912:Multiprotein Complexes; D009218:Myosins