Abstract
The effect of three polymerized phosphates [sodium pyrophosphate (PPi), sodium tripoly-phosphate (TPi), and sodium polyphosphate (PolyPi)] on biochemical properties of carp myosin B was studied in the presence of MgCl2. When 1 mM PPi or TPi, or 0.03% PolyPi was added to myosin B in a medium consisting of 0.5M KCl, 40mM Tris-buffer (pH 7.O) and 1mM MgCl2, a decrease in viscosity and an enhanced liberation of inorganic phosphate (Pi) occurred. The mode of inactivation of Ca-ATPase changed from a single first order to a biphasic first order process. The change, however, was fully re-covered on addition of rabbit F-actin. On the other hand, determination of the liberation rate of Pi from those polymerized phosphates by myosin triphosphatase indicated that the conversion of TPi and PolyPi to PPi proceeded gradually. These results suggested that a large portion of F-actin in myosin B was rapidly denatured and the myosin-binding ability was lost upon the addition of PPi and MgCl2, and that the gradual production of PPi from TPi (or PolyPi) caused slow denaturation of F-actin in myosin B.
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