EFFECT OF CAPPING PROTEIN ON THE KINETICS OF ACTIN POLYMERIZATION
EFFECT OF CAPPING PROTEIN ON THE KINETICS OF ACTIN POLYMERIZATION
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DOI：
10.1021/bi00324a039
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发表时间：
1985-01-01
期刊：
影响因子：
2.9
通讯作者：
POLLARD, TD
中科院分区：
文献类型：
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作者：
COOPER, JA;POLLARD, TD
阿米巴加帽蛋白增加了肌动蛋白聚合的速度，从单体有和没有钙。在不存在Ca的情况下，加帽蛋白也增加了聚合的临界浓度。各种模型进行了评估，他们的能力来预测的加帽蛋白的肌动蛋白聚合的动力学曲线的临界浓度不变的条件下的效果。几个模型，这可能会解释从单体的聚合速率增加，进行了测试。两个模型对实验数据的预测较差：加帽蛋白，类似于肌动蛋白丝（绕过成核）;和加帽蛋白片段。三个模型中，加帽蛋白加速，但没有绕过，成核预测的数据很好。在最好的一个，加帽蛋白类似于一个不可解离的肌动蛋白二聚体。几条证据支持这样的观点，即加帽蛋白阻断了肌动蛋白丝的倒刺末端，阻止了单体的添加和丢失。这一机制也支持在这里的影响，加帽蛋白的肌动蛋白聚合的动力学，这是成核的预制肌动蛋白丝。低的加帽蛋白浓度减缓有核聚合，大概是因为加帽蛋白阻止了长丝倒刺末端的伸长。高加帽蛋白浓度加速成核聚合，因为加帽蛋白与单体相互作用并加速成核的能力。
Acanthamoeba capping protein increased the rate of actin polymerization from monomers with and without Ca. In the absence of Ca, capping protein also increased the critical concentration for polymerization. Various models were evaluated for their ability to predict the effect of capping protein on kinetic curves for actin polymerization under conditions where the critical concentration was not changed. Several models, which might explain the increased rate of polymerization from monomers, were tested. Two models which predicted the experimental data poorly were capping protein, similar to an actin filament, (bypassing nucleation); and capping protein fragments. Three models in which capping protein accelerated, but did not bypass, nucleation predicted the data well. In the best one, capping protein resembled a nondissociable actin dimer. Several lines of evidence supported the idea that capping protein blocks the barbed end of actin filaments, preventing the addition and loss of monomers. This mechanism was also supported here by the effect of capping protein on the kinetics of actin polymerization which was nucleated by preformed actin filaments. Low capping protein concentrations slowed nucleated polymerization, presumably because capping protein blocked elongation at barbed ends of filaments. High capping protein concentrations accelerated nucleated polymerization because of capping protein''s ability to interact with monomers and accelerate nucleation.