Davies P J, Wallach D, Willingham M C, Pastan I, Yamaguchi M, Robson R M
J Biol Chem. 1978 Jun 10;253(11):4036-42.
Chicken gizzard filamin has been digested with purified Ca2+-activated protease. The subunits of (Mr = 250,000) of the protein are cleaved asymmetrically into two fragments, heavy merofilamin, Mr = 240,000, and light merofilamin, Mr = 9,500. Digestion is complete at substrate to enzyme ratios of 100:1 and requires Ca2+ concentrations in excess of 0.3 mM. Heavy merofilamin binds to F-actin as evidenced by cosedimentation with F-actin, by direct observation under the electron microscope, and by its ability to inhibit actin activation of heavy meromyosin ATPase. Heavy merofilamin does not form a gel when mixed with actin, except at very low concentrations of KCl. Thus, actin binding and gelation are separable activities of filamin. We speculate that Ca2+-stimulated proteolysis may play a role in the regulation of actin-filamin interactions.
鸡胗细丝蛋白已用纯化的Ca2+激活蛋白酶进行消化。该蛋白质（Mr = 250,000）的亚基被不对称地切割成两个片段，重肌动蛋白丝蛋白，Mr = 240,000，和轻肌动蛋白丝蛋白，Mr = 9,500。在底物与酶的比例为100:1时消化完成，并且需要Ca2+浓度超过0.3 mM。重肌动蛋白丝蛋白与F-肌动蛋白结合，这通过与F-肌动蛋白的共沉降、电子显微镜下的直接观察以及其抑制重酶解肌球蛋白ATP酶的肌动蛋白激活的能力得以证明。重肌动蛋白丝蛋白与肌动蛋白混合时不会形成凝胶，除非在非常低的KCl浓度下。因此，肌动蛋白结合和凝胶形成是细丝蛋白可分离的活性。我们推测Ca2+刺激的蛋白水解可能在肌动蛋白-细丝蛋白相互作用的调节中起作用。
