PERSISTING IN-VITRO MOTILITY OF ACTIN-FILAMENTS AT NANOMOLAR ATP CONCENTRATIONS AFTER ATP PRETREATMENT

Muscle contraction is driven by the relative sliding of actin- and myo sin-containing filaments. This process can be reconstituted in in vitr o motility assays, where fluorescent actin filaments travel over a law n of myosin heads. The velocity of the traveling actin filaments has b een shown to depend strongly on the free adenosine triphosphate (ATP) concentration, but below 2-4 mu M ATP, filament movement is consistent ly abolished. Here we report that after a brief exposure of actomyosin to 1 mM ATP, actin filament motility persists down to nanomolar ATP c oncentrations.