紧密结合的二价阳离子调节肌动蛋白聚合。

The tightly bound divalent cation regulates actin polymerization.

作者信息

Selden L A, Estes J E, Gershman L C

出版信息

Biochem Biophys Res Commun. 1983 Oct 31;116(2):478-85. doi: 10.1016/0006-291x(83)90548-x.

Abstract

The polymerization characteristics of Ca++-actin and Mg++-actin were studied by measuring initial rates of polymerization upon addition of phalloidin-stabilized nuclei and neutral salt. Under conditions where the effects of divalent cation exchange were minimized, CaCl2 and MgCl2 were found to be equally effective in polymerizing actin. Mg++-actin was found to nucleate and polymerize more readily than Ca++-actin, having a forward rate constant about twice that of Ca++-actin under a variety of polymerizing conditions. The critical concentration for Ca++-actin is approximately 20 times that for Mg++-actin under equivalent conditions. These data imply that the polymer of Mg++-actin must be more stable than that of Ca++-actin, having a depolymerization rate constant about 10 fold lower. Since Mg++ is probably the tightly-bound cation in vivo, whereas Ca++-actin has been more widely studied in vitro, it would appear that actin in its physiological state is probably more polymerizable and more stable in the polymer form than previously considered.

摘要

通过测量添加鬼笔环肽稳定的核和中性盐后肌动蛋白的初始聚合速率，研究了Ca++-肌动蛋白和Mg++-肌动蛋白的聚合特性。在二价阳离子交换影响最小的条件下，发现CaCl2和MgCl2在使肌动蛋白聚合方面同样有效。发现Mg++-肌动蛋白比Ca++-肌动蛋白更容易成核和聚合，在各种聚合条件下，其正向速率常数约为Ca++-肌动蛋白的两倍。在同等条件下，Ca++-肌动蛋白的临界浓度约为Mg++-肌动蛋白的20倍。这些数据表明，Mg++-肌动蛋白的聚合物一定比Ca++-肌动蛋白的聚合物更稳定，其解聚速率常数约低10倍。由于Mg++可能是体内紧密结合的阳离子，而Ca++-肌动蛋白在体外得到了更广泛的研究，因此似乎肌动蛋白在其生理状态下可能比以前认为的更易于聚合，并且以聚合物形式更稳定。