Separation of subfragment-1 of H-meromyosin into two equimolar fractions with and without formation of the reactive enzyme-phosphate-ADP complex.

H-Meromyosin (HMM) was digested with insoluble papain EC 3.4.22.2]. Neither the size of the initial burst of Pi liberation (0.5 mole/mole of myosin head) nor the Mg2+-ATPase EC 3.6.1.3] activity of HMM in the steady state was affected by this treatment. Acto-S-1 was obtained by mixing F-actin with HMM digested with insoluble papain (HMM-S-1). The size of the initial burst of Pi liberation of acto-S-1 was 0.35 mole/mole of S-l at an ATP concentration of 0.5 mole/mole of S-1, and 0.5 mole/moleof S-1 at ATP concentrations above 1 mole/mole of S-1...