A myosin motor protein binds to a molecule of ATP, and releases the energy it contains by splitting it into an ADP molecule and a phosphate ion (Pi). After binding to a filament of actin (shown in green), the motor protein then uses this energy to ‘walk’ along the filament. Repeating this cycle generates a pulling force that can cause a muscle cell to contract—however, this effort, as well as other stresses within the muscle cell, can promote misfolding and a loss of motor function. The accumulation of misfolded ‘dead’ myosin can lead to the formation of protein aggregates, which can have potentially toxic effects. Radke, Taft et al. show that when EMD 57033 (not shown) binds to cardiac β-myosin it increases the rate of ATP binding and energy release (blue circular arrow), which accelerates the motor proteins progression along the actin filament. Remarkably, EMD 57033 can also refold some forms of misfolded myosin back to a properly folded and functional state (purple arrow)—an activity that has not been observed before for similar small molecules.