title: Nanometric features of myosin filaments extracted from a single muscle fiber to uncover the mechanisms underlying organized motility.
abstract: The single muscle fiber in vitro motility assay (SF-IVMA) is characterized by organized linear motility of actin filaments, i.e., actin filaments motility showing a parallel or anti-parallel direction with similar speed independent of direction in the central part of the flow-cell where density of myosin is high. In contrast, the low myosin density region in the flow-cell exhibits random filament movements, but the mechanisms underlying the organized motility remain unknown. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) imaging techniques have been combined to investigate the morphological features of myosin extracted from single muscle fiber segments in the flow cell. Nanometric scale imaging of myosin filaments in the SF-IVMA showed intact spatial distances between myosin heads being essential for myosin filament function. However, angular spectrum analyses of myosin filaments in the high myosin density region showed organized myosin filament orientation only in small areas, while unorganized filament orientation were dominantly presented when larger areas were analyzed. Thus, parallel myosin filament organization is a less likely mechanism underlying the organized motility of actin filaments and the high myosin density per se is therefore forwarded as the primary "driver" that promotes organized linear motility.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Meishan
authors.initials: M
authors.lastname: Li
authors.affiliation: Laboratory of Biophysics and Medicity Research Laboratory, University of Turku, Tykistökatu 6A, FI-20520 Turku, Finland.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Deguchi
authors.affiliation: Laboratory of Biophysics and Medicity Research Laboratory, University of Turku, Tykistökatu 6A, FI-20520 Turku, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Näreoja
authors.affiliation: Department of Physiology, School of Medicine, Wayne State University, 540 E. Canfield, Detroit, MI 48201, USA.
authors.forename: Bhanu P
authors.initials: BP
authors.lastname: Jena
authors.affiliation: Laboratory of Biophysics and Medicity Research Laboratory, University of Turku, Tykistökatu 6A, FI-20520 Turku, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Hänninen
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden. Electronic address: lars.larssoon@ki.se.
authors.forename: Lars
authors.initials: L
authors.lastname: Larsson
mesh_terms: D000818:Animals; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D018485:Muscle Fibers, Skeletal / Q000502:physiology* / Q000648:ultrastructure; D009218:Myosins / Q000502:physiology*; D036103:Nanotechnology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009218:Myosins
keywords: Atomic force microscopy; In vitro motility assay; Myosin filament; Single fiber; Transmission electron microscopy