title: Molecular mechanisms underlying deoxy-ADP.Pi activation of pre-powerstroke myosin.
abstract: Myosin activation is a viable approach to treat systolic heart failure. We previously demonstrated that striated muscle myosin is a promiscuous ATPase that can use most nucleoside triphosphates as energy substrates for contraction. When 2-deoxy ATP (dATP) is used, it acts as a myosin activator, enhancing cross-bridge binding and cycling. In vivo, we have demonstrated that elevated dATP levels increase basal cardiac function and rescues function of infarcted rodent and pig hearts. Here we investigate the molecular mechanism underlying this physiological effect. We show with molecular dynamics simulations that the binding of dADP.Pi (dATP hydrolysis products) to myosin alters the structure and dynamics of the nucleotide binding pocket, myosin cleft conformation, and actin binding sites, which collectively yield a myosin conformation that we predict favors weak, electrostatic binding to actin. In vitro motility assays at high ionic strength were conducted to test this prediction and we found that dATP increased motility. These results highlight alterations to myosin that enhance cross-bridge formation and reveal a potential mechanism that may underlie dATP-induced improvements in cardiac function.
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, 98195-5013.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Nowakowski
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, 98195-5013.|Center for Cardiovascular Biology, University of Washington, Seattle, Washington, 98195-5013.
authors.forename: Michael
authors.initials: M
authors.lastname: Regnier
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, 98195-5013.
authors.forename: Valerie
authors.initials: V
authors.lastname: Daggett
mesh_terms: D000494:Allosteric Regulation; D001665:Binding Sites; D024722:Cardiac Myosins / Q000737:chemistry*; D003838:Deoxyadenine Nucleotides / Q000737:chemistry*; D006801:Humans; D056004:Molecular Dynamics Simulation; D013329:Structure-Activity Relationship
chemical_list: D003838:Deoxyadenine Nucleotides; D024722:Cardiac Myosins
keywords: acto-myosin interaction; allosteric modification; molecular dynamics simulations; pre-powerstroke