Myosin molecules contacting an actin filament in the presence of ATP w
ere found to regulate the filamental fluctuations due to ATP hydrolysi
s in a communicative manner alone the filament. As an evidence of the
occurrence of the communication, ATP-activated fluctuating displacemen
ts of the filament in the direction perpendicular to its longitudinal
axis were identified to propagate at a finite velocity not less than a
bout 0.2 mu m/s unidirectionally along the filament.