Kinetics of ATP and Inorganic Phosphate Release During Hydrolysis of ATP by Rabbit Skeletal Actomyosin Subfragment 1. Oxygen Exchange Between Water and ATP or Phosphate
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We have used the technique of phosphate: water oxygen exchange to measure the rate of ATP and Pi release and Pi binding to myosin subfragment 1 and actomyosin subfragment 1 from rabbit skeletal muscle. The oxygen exchange distributions for ATP and Pi release fit a simple kinetic model with a single set of rate constants for each step. For actomyosin subfragment 1 (20 degrees C, pH 7.0, I = 50 mM), the rate constant governing ATP release is approximately 8 s-1, Pi release is at approximately 60 s-1 and Pi rebinds to an ADP state at greater than 120 M-1 s-1. These rate constants are similar to those that may occur for undistorted cross-bridges within glycerinated rabbit psoas fibers (Bowater, R., Webb, M. R., and Ferenczi, M. A. (1989) J. Biol. Chem. 264, 7193-7201.
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