Effect of dinitrophenol on the interaction between myosin and nucleotides

Abstract

1. 1. The effects of 2,4-dinitrophenol (DNP) on the interaction of several nucleoside triphosphates with myosin B and glycerol-treated psoas fibers have been studied at 0.3 M KCl, 10-3 M Ca++, pH 7.0, 25.5 [deg]C.2. 2. The sequence of reciprocal Michaelis-Menten constants, , is (. The sequence of maximal splitting velocities, V, is V (ITP, GTP) > V (UTP) > V (ATP) > V (CTP). These sequences are unchanged by DNP.3. 3. For ATP, CTP, and UTP, DNP raises V and lowers a nearly compensatory way.4. 4. DNP reduces the inhibition of ITPase activity by ADP, decreases the activation of ATPase activity by EDTA, and inhibits the rate of splitting of tripolyphosphate.5. 5. The non-enzymic alkaline hydrolysis rates of ATP, UTP, GTP, CTP, and ITP are about equal at pH 8.5, 0.3 M KCl, 100 [deg]C. The addition of Mg++ slightly increases the rate. Ca++ approximately doubles the rate. DNP has no effect. Decreasing the salt concentration increases the rate.6. 6. DNP decreases the amount of shortening of unloaded psoas fibers.7. 7. The results have been discussed in terms of a kinetic scheme which assumes that the rate of desorption of the nucleoside diphosphate product of the reaction may be rate limiting under certain conditions.