Interaction of actomyosin with adenosine triphosphate at low ionic strength. II. Factors influencing clearing and superprecipitation: adenosine triphosphatase and birefringence of flow studies.

The clearing of actomyosin at p = 0.15 to 0.16 and pH 7.0 brought about by adenosine triphosphate in the presence of added magnesium was interpreted in the preceding paper in terms of the dissociation of actomyosin into its components (2). This report deals with various factors influencing the clearing reaction and the accompanying changes in adenosine triphosphatase activity. Adenosine triphosphate was found to be most effective among the various nucleoside triphosphates and magnesium to be specific among the divalent metals tested. At p < 0.1, adenosine triphosphate and magnesium alone cannot produce clearing: chelating reagents or the relaxing factor of muscle are necessary. The possible physiological meaning of these findings is briefly discussed.