dATP induces an allosteric restructuring of the actin-binding surface on myosin, increasing electrostatic interactions and repositioning myosin motors toward the thin filament before activation.
Understanding the structural basis of dATP-mediated increased cardiac contractility provides mechanistic insights that could guide the design of novel small-molecule therapeutics for systolic dysfunction.
The naturally occurring nucleotide 2-deoxy-adenosine 5'-triphosphate (dATP) can be used by cardiac muscle as an alternative energy substrate for myosin chemomechanical activity. We and others have previously shown that dATP increases contractile force in normal hearts and models of depressed systolic function, but the structural basis of these effects has remained unresolved. In this work, we combine multiple techniques to provide structural and functional information at the angstrom-nanometer and millisecond time scales, demonstrating the ability to make both structural measurements and quantitative kinetic estimates of weak actin-myosin interactions that underpin sarcomere dynamics. Exploiting dATP as a molecular probe, we assess how small changes in myosin structure translate to electrostatic-based changes in sarcomere function to augment contractility in cardiac muscle. Through Brownian dynamics simulation and computational structural analysis, we found that deoxy-hydrolysis products 2-deoxy-adenosine 5'-diphosphate (dADP) and inorganic phosphate (Pi) bound to prepowerstroke myosin induce an allosteric restructuring of the actin-binding surface on myosin to increase the rate of cross-bridge formation. We then show experimentally that this predicted effect translates into increased electrostatic interactions between actin and cardiac myosin in vitro. Finally, using small-angle X-ray diffraction analysis of sarcomere structure, we demonstrate that the proposed increased electrostatic affinity of myosin for actin causes a disruption of the resting conformation of myosin motors, resulting in their repositioning toward the thin filament before activation. The dATP-mediated structural alterations in myosin reported here may provide insight into an improved criterion for the design or selection of small molecules to be developed as therapeutic agents to treat systolic dysfunction.
Powers et al. (2019) studied Systolic dysfunction. 2-deoxy-adenosine 5'-triphosphate (dATP) was evaluated on Structural and functional changes in actin-myosin interactions. dATP induces an allosteric restructuring of the actin-binding surface on myosin, increasing electrostatic interactions and repositioning myosin motors toward the thin filament before activation.