Key Points
- Investigate the pre-steady state kinetics of ATP hydrolysis by myosin and characterize the functional interaction between F-actin and myosin intermediates.
- Treated myosin with NTP and reconstituted actomyosin complexes with F-actin under varying ionic strengths and MgCl2 concentrations.
- Measured pre-steady state inorganic phosphate and hydrogen ion liberation alongside actomyosin light-scattering intensity and superprecipitation rates.
- NTP treatment abolished the initial burst of phosphate liberation and inhibited actomyosin ATPase activity, preventing superprecipitation and clearing responses.
- High ionic strength and low Mg2+ produced an extra phosphate burst exceeding 1 mole per 4×10^5 g myosin, which coincided quantitatively with hydrogen ion liberation and light-scattering decreases.
- Actomyosin ATPase activity reached a peak at 5 μM MgCl2 before declining at higher concentrations, and delayed addition of F-actin eliminated the initial rapid ATP cleavage burst.
Structured PICO
PPopulationMyosin-Adenosine Triphosphate (ATP) system
IInterventionTreatment of myosin with NTP
OOutcomeRate of ATP-hydrolysis and P1-liberationsurrogate
Treatment of myosin with NTP inhibits the actomyosin type of ATPase activity and abolishes the initial burst of P1-liberation, providing insights into the reaction mechanism of the myosin-ATP system.