Myosin ATPase course

The time course of the labeling of myosin by Co-(phen)-ATP (Fig. 1) occurs in two phases at first ATPase activity (Ca +-, EDTA-, and actin-dependent activities) are enhanced, and in the second phase the activities are abolished in a pseudo-first-order process. In the cases of the myosin subfragments— double-headed heavy meromyosin (HMM) and single-headed subfragment 1 (S-1)—no enhancement phase is observed and the labeling occurs as a pseudo-first-order inactivation process. The kinetic parameters of the Co-(phen)-ATP affinity labeling of myosin and its subfragments are summarized in Table II. 

Figure 5.5 Time course of the burst of Pj formation during a single turnover of the myosin(Sl) ATPase reaction in 40% ethylene glycol at —15 C. The complete reaction shown in (a) and the initial acceleration is shown in (b). The time constants for the acceleration and the burst reaction are t, = 34.5 s and =333 s respectively (from Tesi et al., 1991).

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