Davies P J, Wallach D, Willingham M, Pastan I, Lewis M S
Biochemistry. 1980 Apr 1;19(7):1366-72. doi: 10.1021/bi00548a015.
Filamin is a high molecular weight (subunit Mr 250 000) actin-binding protein isolated from smooth muscle. The protein forms a gel when mixed with solutions of F-actin. A proteolytic fragment of filamin, heavy merofilamin (subunit Mr 240 000), generated by the action of Ca2+-activated protease binds to actin but does not produce gelation. We have studied the self-association properties of filamin and heavy merofilamin by direct examination in the electron microscope and by equilibrium sedimentation distribution studies in the ultracentrifuge. Filamin self-associates reversibly to form dimers; the free energy of dimerization is approximately 7 kcal/mol. Further association to form tetramer and multimer appears to be irreversible. Warming of filamin solutions accelerates aggregation. Heavy merofilamin does not appear to self-associate but is entirely monomeric. These studies suggest that filamin produces gelation of F-actin by binding to actin and then self-associating to cross-link actin filaments into a gel.
细丝蛋白是一种从平滑肌中分离出来的高分子量（亚基分子量为250 000）肌动蛋白结合蛋白。该蛋白与F-肌动蛋白溶液混合时会形成凝胶。由Ca2+激活的蛋白酶作用产生的细丝蛋白的蛋白水解片段，即重酶解肌动蛋白（亚基分子量为240 000），能与肌动蛋白结合，但不会产生凝胶化。我们通过电子显微镜直接观察以及超速离心机中的平衡沉降分布研究，对细丝蛋白和重酶解肌动蛋白的自缔合特性进行了研究。细丝蛋白可逆地自缔合形成二聚体；二聚化的自由能约为7千卡/摩尔。进一步缔合形成四聚体和多聚体似乎是不可逆的。细丝蛋白溶液升温会加速聚集。重酶解肌动蛋白似乎不会自缔合，完全以单体形式存在。这些研究表明，细丝蛋白通过与肌动蛋白结合，然后自缔合将肌动蛋白丝交联成凝胶，从而使F-肌动蛋白产生凝胶化。
