Fig. 5. Inhibition of actin/tropomyosin-activated HMM ATPase by CaD39 and CaD39-AB. Rates of HMM ATPase were measured at 29°C in 20 mM imidazole buffer (pH 7.0), 2 mM MgCl₂, 50 mM KCl, 0.1 mM EGTA and 1 mM DTT. 12 µM F-actin, 2.5 µM hTM5 and 0.04 µM HMM were incubated in the absence or presence of 2.8 µM CaD39 or CaD39-AB. The reversal of CaD inhibition was measured in the presence of 2.5 µM CaM and 2 mM CaCl₂. The actin/tropomyosin-activated HMM ATPase activity (4.58 nmole phosphate released per minute per mg of HMM) obtained under this assay condition was used as 100%. Abbreviations: A, actin; TM, tropomyosin.