Hozumi T, Hotta K
J Biochem. 1977 Apr;81(4):1141-6. doi: 10.1093/oxfordjournals.jbchem.a131539.
The interaction of actin with myosin was studied in the presence of ATP at low ionic strength by means of measurements of the actin-activated ATPase activity of myosin and superprecipitation of actomyosin. At high ATP concentrations the ATPase activities of myosin, heavy meromyosin (HMM) and myosin subfragment 1 (S-1) were activated by actin in the same extent. At low ATP concentrations the myosin ATPase activity was activated about 30-fold by actin, whereas those of HMM and S-1 were stimulated only several-fold. This high actin activation of myosin ATPase was coupled with the occurrence of superprecipitation. The activation of HMM or S-1 ATPase by actin shows a simple hyperbolic dependence on actin concentration, but the myosin ATPase was maximally activated by actin at a 2:1 molar ratio of actin to myosin, and a further increase in the actin concentration had no effect on the activation. These results suggest the presence of a unit for actin-myosin interaction, composed of two actin monomers and one myosin molecule in the filaments.
在低离子强度且存在ATP的情况下，通过测量肌球蛋白的肌动蛋白激活的ATP酶活性以及肌动球蛋白的超沉淀，研究了肌动蛋白与肌球蛋白的相互作用。在高ATP浓度下，肌球蛋白、重酶解肌球蛋白（HMM）和肌球蛋白亚片段1（S-1）的ATP酶活性被肌动蛋白以相同程度激活。在低ATP浓度下，肌球蛋白的ATP酶活性被肌动蛋白激活约30倍，而HMM和S-1的活性仅被刺激几倍。肌球蛋白ATP酶的这种高肌动蛋白激活与超沉淀的发生相关。肌动蛋白对HMM或S-1 ATP酶的激活表现出对肌动蛋白浓度的简单双曲线依赖性，但肌球蛋白ATP酶在肌动蛋白与肌球蛋白的摩尔比为2:1时被肌动蛋白最大程度地激活，肌动蛋白浓度的进一步增加对激活没有影响。这些结果表明在细丝中存在由两个肌动蛋白单体和一个肌球蛋白分子组成的肌动蛋白 - 肌球蛋白相互作用单元。
