The limiting rate of the ATP-mediated dissociation of actin from rabbit skeletal muscle myosin subfragment 1.

The ATP-induced dissociation of actoS1 has been studied at temperatures between -10 degrees C and +30 degrees C in a stopped-flow apparatus using ethylene glycol as antifreeze. At temperatures at and below 0 degrees C the observed rate of the dissociation of actin shows a hyperbolic dependence on ATP concentration. This is interpreted in terms of a rapid binding of ATP followed by an isomerisation of the ternary complex which results in actin dissociation. Ethylene glycol weakens ATP binding but the rate of the isomerisation is unaffected. The second order rate constant for the dissociation shows a break in the Arrhenius plot.