title: Dynamic exchange of myosin molecules between thick filaments.
abstract: To examine thick filament assembly and myosin exchange, a fluorescence energy transfer assay has been established. Assembly-competent myosin molecules labeled with the sulfhydryl-specific fluorochromes 5-(2-[(iodoacetyl)-amino]ethyl)aminonaphthalene-1-sulfonic acids (IAEDANS) or 5-iodoacetamidofluorescein (IAF) were prepared. Using IAEDANS-labeled myosin as fluorescence donor and IAF-labeled myosin as acceptor, thick filament formation was followed by the decrease in donor fluorescence at 0.1 M KCl/10 mM potassium phosphate, pH 6.9. The critical concentration of myosin--i.e., that concentration that remained unassembled at equilibrium with fully formed filaments--was 40 nM. In FET and 125I-labeled myosin incorporation assays, extensive exchange of myosin between thick filaments was observed. The presence of a critical concentration and the measurements of extensive exchange suggest a dynamic equilibrium between fully polymerized myosin and a small pool of soluble myosin.
authors.forename: A D
authors.initials: AD
authors.lastname: Saad
authors.forename: J D
authors.initials: JD
authors.lastname: Pardee
authors.forename: D A
authors.initials: DA
authors.lastname: Fischman
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology*; D000818:Animals; D000911:Antibodies, Monoclonal; D002645:Chickens; D003599:Cytoskeleton / Q000502:physiology*; D004735:Energy Transfer; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D009130:Muscle, Smooth / Q000502:physiology; D009132:Muscles / Q000502:physiology; D009218:Myosins / Q000502:physiology*; D011485:Protein Binding
chemical_list: D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D009218:Myosins