Cardiac myosin activation with 2-deoxy-ATP via increased electrostatic interactions with actin

The development of several small-molecule myosin activators to rescue cardiac contractility of failing hearts is underway, but understanding the multiscale structure-function consequences of these inotropes remains a major challenge. Using 2'-deoxy-adenosine 5'-triphosphate (dATP; a myosin-binding nucleotide) as a molecular probe, we show that a restructuring of prepowerstroke myosin in the presence of 2-deoxy-adenosine 5'-diphosphate and inorganic phosphate (dADP.Pi) (versus ADP.Pi) increases actin-myosin electrostatic interactions and binding kinetics. X-ray diffraction revealed myosin structure with dATP in relaxed myofilament is similar to the activated state with ATP, with S1 head movement toward actin and stabilization, resulting in an improved probability of strong cross-bridge formation upon activation. Thus, the alterations induced by dATP may provide clues to a more optimal structure of cardiac myosin to be attained by myosin-targeted therapies for heart failure.