Figure 4.
Actin-activated product release. Sequential mix single-turnover experiments were performed by mixing MV with ATP, aging the reaction to form the M.ADP.Pi state (0.45 μm), and then mixing with different concentrations of actin in the presence of MDCC-PBP (5 μm). A, the fluorescence transients were fit to a single-exponential function (phosphate burst) followed by a linear or slow exponential rise. B, the phosphate release rate constants were plotted as a function of actin concentration and fit to a hyperbolic function to estimate the maximum rate of phosphate release. C, acto-MV (0.25 μm) in presence mantADP (5 μm) was mixed with saturating ATP (1 mm) at 25 °C to determine the ADP release rate constant. D, the mantADP release rate constant was examined as a function of temperature, and the associated Eyring plot (natural log of the ADP release rate constant as a function of inverse temperature) was fit to a linear regression. Fluorescence is reported in arbitrary units (AU).