Initial Rapid Proton Liberation During Hydrolysis of Adenosine Triphosphate by Myosin Subfragment 1

Abstract

Abstract The rate of hydrogen ion liberation during the hydrolysis of ATP by Subfragment I was followed in a stopped flow spectrophotometer. At pH 8, 20°, and in the presence of MgCl2 the initial rate of hydrogen ion liberation was greater than the steady state rate and the approach to a steady state rate could be described by a single exponential term. The rate constant characterizing the exponential term increased with MgATP concentration from 0.01 to 0.1 mm above which an average limiting value of 128 s-1 was reached. It was confirmed that two exponential terms are required to describe the course of the reaction for myosin. These results can be interpreted as indicating interaction between the two ATPase sites on intact myosin.