Lind S E, Smith D B, Janmey P A, Stossel T P
J Clin Invest. 1986 Sep;78(3):736-42. doi: 10.1172/JCI112634.
We determined the plasma kinetics of both actin and complexes of actin with the two high affinity actin-binding proteins of plasma, gelsolin, and vitamin D-binding protein (DBP). Actin is cleared rapidly from the plasma by the liver (half-disappearance time, 0.5 h). Using radiolabeled actin-binding proteins, we found that actin accelerated the clearance of both plasma gelsolin and the vitamin D-binding protein. In separate experiments we found that DBP-actin complexes were cleared more quickly than gelsolin-actin complexes, at a rate comparable to the clearance of actin from the blood. A low affinity interaction (dissociation constant, 2.9 X 10(-4) M) between actin and fibronectin was found, suggesting that little actin will bind to fibronectin in plasma. We conclude that while plasma gelsolin and DBP may both clear actin from the circulation, DBP appears to play a more important role. By so doing, DBP may conserve the filament-severing activity of plasma gelsolin.
我们测定了肌动蛋白以及肌动蛋白与血浆中两种高亲和力肌动蛋白结合蛋白（凝溶胶蛋白和维生素D结合蛋白，即DBP）形成的复合物在血浆中的动力学。肝脏可迅速清除血浆中的肌动蛋白（半衰期为0.5小时）。利用放射性标记的肌动蛋白结合蛋白，我们发现肌动蛋白可加速血浆凝溶胶蛋白和维生素D结合蛋白的清除。在单独的实验中我们发现，DBP-肌动蛋白复合物的清除速度比凝溶胶蛋白-肌动蛋白复合物更快，其清除速率与肌动蛋白从血液中的清除速率相当。我们发现肌动蛋白与纤连蛋白之间存在低亲和力相互作用（解离常数为2.9×10⁻⁴ M），这表明血浆中很少有肌动蛋白会与纤连蛋白结合。我们得出结论，虽然血浆凝溶胶蛋白和DBP都可能从循环中清除肌动蛋白，但DBP似乎发挥着更重要的作用。通过这样做，DBP可能会保留血浆凝溶胶蛋白的丝切活性。
