title: The role of structural dynamics of actin in class-specific myosin motility.
abstract: The structural dynamics of actin, including the tilting motion between the small and large domains, are essential for proper interactions with actin-binding proteins. Gly146 is situated at the hinge between the two domains, and we previously showed that a G146V mutation leads to severe motility defects in skeletal myosin but has no effect on motility of myosin V. The present study tested the hypothesis that G146V mutation impaired rotation between the two domains, leading to such functional defects. First, our study showed that depolymerization of G146V filaments was slower than that of wild-type filaments. This result is consistent with the distinction of structural states of G146V filaments from those of the wild type, considering the recent report that stabilization of actin filaments involves rotation of the two domains. Next, we measured intramolecular FRET efficiencies between two fluorophores in the two domains with or without skeletal muscle heavy meromyosin or the heavy meromyosin equivalent of myosin V in the presence of ATP. Single-molecule FRET measurements showed that the conformations of actin subunits of control and G146V actin filaments were different in the presence of skeletal muscle heavy meromyosin. This altered conformation of G146V subunits may lead to motility defects in myosin II. In contrast, distributions of FRET efficiencies of control and G146V subunits were similar in the presence of myosin V, consistent with the lack of motility defects in G146V actin with myosin V. The distribution of FRET efficiencies in the presence of myosin V was different from that in the presence of skeletal muscle heavy meromyosin, implying that the roles of actin conformation in myosin motility depend on the type of myosin.
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan; Department of Chemical Science and Engineering, National Institute of Technology, Miyakonojo College, Miyakonojo, Miyazaki, Japan.
authors.forename: Taro Q P
authors.initials: TQ
authors.lastname: Noguchi
authors.affiliation: Nanobiology Laboratories, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Morimatsu
authors.affiliation: Nanobiology Laboratories, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan; Quantitative Biology Center (QBiC), RIKEN, Suita, Osaka, Japan.
authors.forename: Atsuko H
authors.initials: AH
authors.lastname: Iwane
authors.affiliation: Nanobiology Laboratories, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan; Quantitative Biology Center (QBiC), RIKEN, Suita, Osaka, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan; Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Taro Q P
authors.initials: TQ
authors.lastname: Uyeda
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D000199:Actins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D004023:Dictyostelium / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009068:Movement; D016297:Mutagenesis, Site-Directed; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism; D024462:Myosin Type II / Q000737:chemistry / Q000378:metabolism; D024701:Myosin Type V / Q000737:chemistry / Q000378:metabolism; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D020409:Molecular Motor Proteins; D015879:Myosin Subfragments; D015800:Protozoan Proteins; D024462:Myosin Type II; D024701:Myosin Type V; D009218:Myosins