Actin polymerization. The mechanism of action of cytochalasin D.
Actin polymerization. The mechanism of action of cytochalasin D.
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DOI：
10.1016/s0021-9258(18)66662-1
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发表时间：
1986-12
期刊：
影响因子：
--
通讯作者：
D. Goddette;Carl Frieden
中科院分区：
文献类型：
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作者：
D. Goddette;Carl Frieden
荧光的变化，使用肌动蛋白共价标记的N-（1-芘基）碘乙酰胺已被用来确定细胞松弛素D对肌动蛋白聚合的影响。细胞松弛素D对肌动蛋白聚合的影响的机制，这解释了实验观察的细胞松弛素D诱导的聚合的初始速率的增加和反应的最终程度的减少。该机制的核心是细胞松弛素D诱导的二聚体的Mg 2+依赖性形成。二聚体充当核以提高聚合速率。Mg 2+与二聚体上的低亲和力位点的结合诱导构象变化，其可以作为快速荧光增加来观察。随后的时间依赖性荧光减少聚合前观察到的ATP水解，导致二聚体的解离和释放的肌动蛋白单体含有ADP。我们假设，一个缓慢的速率交换ATP结合ADP相对于水解的结果在积累的单体含有ADP。由于这些单体具有高临界浓度，聚合的最终程度显著降低。在细胞松弛素D的存在下，聚合的最终程度的Mg 2+依赖性也解释了这种机制的上下文中。
Fluorescence changes using actin covalently labeled with N-(1-pyrenyl)iodoacetamide have been used to determine the effect of cytochalasin D on actin polymerization. A mechanism for the effect of cytochalasin D on actin polymerization is presented, which explains the experimental observation of a cytochalasin D-induced increase in the initial rate of polymerization and a decrease in the final extent of the reaction. Central to this mechanism is the Mg2+-dependent formation of cytochalasin D-induced dimers. The dimers serve as nuclei to enhance the polymerization rate. Binding of Mg2+ to a low affinity site on the dimer induces a conformational change which can be observed as a rapid fluorescence increase. A subsequent time-dependent fluorescence decrease observed prior to polymerization appears to represent ATP hydrolysis resulting in dissociation of the dimer and release of actin monomers containing ADP. We postulate that a slow rate of exchange of ATP for bound ADP relative to hydrolysis results in the accumulation of monomers containing ADP. As these monomers have a high critical concentration, the final extent of polymerization is reduced dramatically. The Mg2+ dependence of the final extent of polymerization in the presence of cytochalasin D is also explained in the context of this mechanism.