title: Direct measurements of the coordination of lever arm swing and the catalytic cycle in myosin V.
abstract: Myosins use a conserved structural mechanism to convert the energy from ATP hydrolysis into a large swing of the force-generating lever arm. The precise timing of the lever arm movement with respect to the steps in the actomyosin ATPase cycle has not been determined. We have developed a FRET system in myosin V that uses three donor-acceptor pairs to examine the kinetics of lever arm swing during the recovery and power stroke phases of the ATPase cycle. During the recovery stroke the lever arm swing is tightly coupled to priming the active site for ATP hydrolysis. The lever arm swing during the power stroke occurs in two steps, a fast step that occurs before phosphate release and a slow step that occurs before ADP release. Time-resolved FRET demonstrates a 20-Å change in distance between the pre- and postpower stroke states and shows that the lever arm is more dynamic in the postpower stroke state. Our results suggest myosin binding to actin in the ADP.Pi complex triggers a rapid power stroke that gates the release of phosphate, whereas a second slower power stroke may be important for mediating strain sensitivity.
authors.affiliation: Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA 17033;
authors.forename: Darshan V
authors.initials: DV
authors.lastname: Trivedi
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, School of Medicine, University of Minnesota, Minneapolis, MN 55455;
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Muretta
authors.affiliation: Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA 17033;
authors.forename: Anja M
authors.initials: AM
authors.lastname: Swenson
authors.affiliation: Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210.
authors.forename: Jonathon P
authors.initials: JP
authors.lastname: Davis
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, School of Medicine, University of Minnesota, Minneapolis, MN 55455;
authors.forename: David D
authors.initials: DD
authors.lastname: Thomas
authors.affiliation: Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA 17033; cmy11@psu.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Yengo
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D031541:Fluorescence Resonance Energy Transfer; D024701:Myosin Type V / Q000737:chemistry*
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D024701:Myosin Type V
keywords: FRET; actin; force generation; kinetics; myosin