Studies on the Interaction of Actin with Myosin. III. Effect of Polyethylene Glycol on Heavy Meromyosin, Light Meromyosin and Acto-Heavy Meromyosin

The effect of PEG on synthetic actomyosin, acto-heavy meromyosin, heavy meromyosin and light meromyosin prepared from rabbit skeletal muscle was studied and the following results were obtained. 1) Mg++ -ATPase activity of acto-heavy meromyosin was not significantly influenced by 10 to 50 mg/m? PEG. On the other hand, Mg++ -ATPase activity of synthetic actomyosin was markedly activated by 30 mg/m? PEG or over. 2) Mg++ -ATPase activity of acto-heavy meromyosin was markedly activated by PEG at lower concentrations of KCl. The curve of KCl concentration dependence of Mg++ -ATPase activity of acto-heavy meromyosin was slightly shifted to a higher KCl concentration by PEG. 3) ATPase activity of heavy meromyosin was not influenced by PEG in the presence of various concentrations of MgCｌ2. 4) In the presence and absence of PEG, superprecipitation was not observed in acto-heavy meromyosin. On the other hand, superprecipitation of synthetic actomyosin was accelerated by PEG. 5) Turbidity of light meromyosin was increased by PEG and this was slightly decreased by an addition of ATP. 6) The increase of turbidity was observed in actin plus light meromyosin only in the presence of PEG. The increase of turbidity which may be considered as a superprecipitation-like phenomenon was observed in acto-heavy meromyosin plus light meromyosin in the presence of PEG, while it was not observed in the absence of PEG. From these results, it is suggested that PEG mainly exerts its effect on myosin, especially light meromyosin