Hydrolysis of ATP by polymerized actin depends on the bound divalent cation but not profilin
Hydrolysis of ATP by polymerized actin depends on the bound divalent cation but not profilin
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DOI：
10.1021/bi011214b
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发表时间：
2002-01-15
期刊：
影响因子：
2.9
通讯作者：
Pollard, TD
中科院分区：
文献类型：
--
作者：
Blanchoin, L;Pollard, TD
越来越多的证据表明，与肌动蛋白丝结合的核苷酸充当计时器以控制细胞运动期间的肌动蛋白丝更新（Pollard，T. D、布朗钦湖和Mullins，R. D.（2000）Annu.生物物理学生物分子Struct.29，545-576）。我们重新研究了ATP的水解聚合肌动蛋白使用机械淬灭流的方法，以提高时间分辨率。聚合镁肌动蛋白水解ATP的速率常数为0.3 s（-1），比人工测定的速率快3倍。当Mg ATP肌动蛋白延长细丝的尖端或倒刺端时，ATP水解速率相似。聚合的Ca肌动蛋白在0.05 s（-1）时水解ATP。用profilin饱和的Mg ATP肌动蛋白可以在>60 s（-1）时伸长倒刺末端，比ATP水解（0.3 s（-1））快2个数量级。考虑到profilin结合到肌动蛋白表面，而肌动蛋白表面被掩埋在肌动蛋白细丝的Holmes模型中，我们预计profilin将阻止细丝倒刺末端的亚基添加。Profilin必须以比它从单体上解离的速度（4 s（-1））更快的速度从这个位点移动。这种运动不需要ATP水解。
Growing evidence suggests that the nucleotide bound to actin filaments serves as a timer to control actin filament turnover during cell motility (Pollard, T. D., Blanchoin, L., and Mullins, R. D. (2000) Annu. Rev. Biophys. Biomol. Struct. 29, 545-576). We re-examined the hydrolysis of ATP by polymerized actin using mechanical quenched-flow methods to improve temporal resolution. The rate constant for ATP hydrolysis by polymerized Mg actin is 0.3 s(-1), 3-fold faster than that measured manually. The ATP hydrolysis rate is similar when Mg ATP actin elongates either the pointed end or the barbed end of filaments. Polymerized Ca actin hydrolyzes ATP at 0.05 s(-1). Mg ATP actin saturated with profilin can elongate barbed ends at >60 s(-1), 2 orders of magnitude faster than ATP hydrolysis (0.3 s(-1)). Given that profilin binds to a surface on actin that is buried in the Holmes model of the actin filament, we expect that profilin will block subunit addition at the barbed end of a filament. Profilin must move from this site at rates much faster than it dissociates from monomers (4 s(-1)). ATP hydrolysis is not required for this movement.