title: Direct real-time detection of the structural and biochemical events in the myosin power stroke.
abstract: A principal goal of molecular biophysics is to show how protein structural transitions explain physiology. We have developed a strategic tool, transient time-resolved FRET [(TR)(2)FRET], for this purpose and use it here to measure directly, with millisecond resolution, the structural and biochemical kinetics of muscle myosin and to determine directly how myosin's power stroke is coupled to the thermodynamic drive for force generation, actin-activated phosphate release, and the weak-to-strong actin-binding transition. We find that actin initiates the power stroke before phosphate dissociation and not after, as many models propose. This result supports a model for muscle contraction in which power output and efficiency are tuned by the distribution of myosin structural states. This technology should have wide application to other systems in which questions about the temporal coupling of allosteric structural and biochemical transitions remain unanswered.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455 muret003@umn.edu ddt@umn.edu.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Muretta
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: John A
authors.initials: JA
authors.lastname: Rohde
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Johnsrud
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Sinziana
authors.initials: S
authors.lastname: Cornea
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455 muret003@umn.edu ddt@umn.edu.
authors.forename: David D
authors.initials: DD
authors.lastname: Thomas
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D030161:Avian Proteins / Q000737:chemistry* / Q000378:metabolism; D002645:Chickens; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008956:Models, Chemical; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism; D011817:Rabbits
chemical_list: D030161:Avian Proteins; D009218:Myosins
keywords: FRET; myosin; phosphate release; power stroke; structural kinetics