Janmey P A, Lind S E, Yin H L, Stossel T P
Biochim Biophys Acta. 1985 Aug 16;841(2):151-8. doi: 10.1016/0304-4165(85)90016-9.
Low concentrations of actin filaments (F-actin) inhibit the rate and extent of turbidity developed during polymerization of purified fibrinogen by thrombin. Actin incorporates into the fibrin clot in a concentration-dependent manner that does not reach saturation, indicating nonspecific trapping of actin filaments in the fibrin network. Actin does not retard activation of fibrinogen by thrombin, but rather the alignment of fibrin protofibrils into bundles which constitute the coarse clot. In contrast, equivalent F-actin concentrations have little or no effect on the turbidity of plasma clots. The difference is attributed to the presence of a plasma protein, gelsolin, that severs actin filaments. Purified gelsolin greatly reduces the effect of F-actin on the turbidity of a pure fibrin clot and decreases the fraction of actin incorporated by the clot. A calculation of the extent to which the gelsolin concentrations used in these experiments reduce the fraction of actin filaments which are long enough to impede each other's rotational diffusion indicates that it is the overlapping actin filaments which retard the association of fibrin protofibrils. The findings suggest that one role for the F-actin depolymerizing and particularly actin severing activities in blood is to prevent actin filaments released by tissue injury from interfering with the formation of coarse fibrin clots.
低浓度的肌动蛋白丝（F-肌动蛋白）会抑制凝血酶使纯化的纤维蛋白原聚合过程中浊度产生的速率和程度。肌动蛋白以浓度依赖的方式掺入纤维蛋白凝块中，且不会达到饱和，这表明肌动蛋白丝在纤维蛋白网络中是非特异性截留。肌动蛋白不会阻碍凝血酶对纤维蛋白原的激活，而是会阻碍纤维蛋白原纤维排列成束，这些束构成了粗糙的凝块。相比之下，同等浓度的F-肌动蛋白对血浆凝块的浊度几乎没有影响。这种差异归因于血浆中存在一种名为凝溶胶蛋白的蛋白质，它能切断肌动蛋白丝。纯化的凝溶胶蛋白能大大降低F-肌动蛋白对纯纤维蛋白凝块浊度的影响，并减少凝块掺入的肌动蛋白比例。对这些实验中使用的凝溶胶蛋白浓度降低足够长以相互阻碍旋转扩散的肌动蛋白丝比例程度的计算表明，阻碍纤维蛋白原纤维缔合的是相互重叠的肌动蛋白丝。这些发现表明，血液中F-肌动蛋白解聚尤其是肌动蛋白切断活性的一个作用是防止组织损伤释放的肌动蛋白丝干扰粗糙纤维蛋白凝块的形成。
