FIGURE 8.

Mg²⁺-dependent phosphate release in MV 1IQ. The phosphate release rate constants at 0.3 mm free Mg²⁺ (open red circles) and 9.0 mm free Mg²⁺ (open blue squares) were monitored by change in fluorescence of the phosphate-binding protein. MV 1IQ and sub-stoichiometric ATP were mixed and allowed to age for 10 s followed by the addition of actin in the presence of phosphate-binding protein (final reaction conditions: 0.25 μm MV 1IQ, 0.2 μm ATP, 4 μm phosphate-binding protein, and varying actin concentrations).