Kaldor G, DiBattista W J, Schroder R L, Hamilton S
Physiol Chem Phys. 1979;11(4):327-55.
Ca2+ "free" actomyosin suspensions as well as actin heavy meromyosin (HMM) solutions in the presence of Ca2+ showed no contractile response (superprecipitation) and had low steady-state Mg2+-ATPase activity. Under the same experimental conditions both the enzymatic activity increased and contractile response was restored if the solubility of the proteins was depressed by the addition of polyethylene glycol 4000 (PEG-4000). The stability of the enzymatically active actomyosin or actin HMM complexes was 10 times lower in cleared solutions than in the insoluble actomyosin or actin HMM suspensions. It was concluded that soluble actomyosin or actin HMM solutions are inadequate test tube models for studying muscular contraction.
在不存在Ca2+的情况下，肌动球蛋白悬浮液以及在Ca2+存在下的肌动蛋白重酶解肌球蛋白（HMM）溶液均未表现出收缩反应（超沉淀），且稳态Mg2+-ATP酶活性较低。在相同实验条件下，如果通过添加聚乙二醇4000（PEG-4000）降低蛋白质的溶解度，酶活性会增加，收缩反应也会恢复。在澄清溶液中，具有酶活性的肌动球蛋白或肌动蛋白HMM复合物的稳定性比不溶性肌动球蛋白或肌动蛋白HMM悬浮液低10倍。由此得出结论，可溶性肌动球蛋白或肌动蛋白HMM溶液并非用于研究肌肉收缩的合适试管模型。
