Modification of the interactions of myosin with actin and 5'-adenylyl imidodiphosphate by substitution of ethylene glycol for water.

We studied the effect of replacing water by ethylene glycol as solvent on the properties of skeletal muscle myosin, myosin subfragment-1 (S1) and heavy meromyosin. Ethylene glycol (50%, v/v) had no detectable effect on the affinity of myosin or actomyosin for the substrate analogue 5'-adenylyl imidodiphosphate (AMPPNP). However, the rate constants for formation and dissociation of the myosin X MgAMPPNP complex were reduced 200-fold; the logarithm of the dissociation rate was roughly proportional to the fractional concentration of ethylene glycol. Nucleotide dissociation was accelerated at least 300-fold by pure actin but remained slow with regulated actin in the absence of Ca2+. Ethylene glycol substitution reduced the affinity of S1 and the S1 X MgAMPPNP complex for actin equally (100-fold at 50% ethylene glycol). These results show that ethylene glycol has specific effects on myosin's enzymic mechanism, which can account for its effect on the tension and stiffness of glycerinated muscle fibres.