KINETIC-ANALYSIS OF MICROTUBULE SELF-ASSEMBLY INVITRO
KINETIC-ANALYSIS OF MICROTUBULE SELF-ASSEMBLY INVITRO
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DOI：
10.1016/0022-2836(77)90020-1
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发表时间：
1977-01-01
影响因子：
5.6
通讯作者：
BORISY, GG
中科院分区：
文献类型：
--
作者：
JOHNSON, KA;BORISY, GG
[猪脑]微管组装的动力学进行了研究，通过监测浊度的变化，这是由于入射光的散射的聚合物。组装可能通过涉及成核阶段的途径发生，随后是伸长阶段，如聚合动力学中的滞后所证明的，随后是浊度的伪一阶指数增加。聚合至平衡的溶液的分析超离心表明，6 S微管蛋白是与微管平衡的唯一可检测的物种。6 S微管蛋白和微管片段混合物中的延伸反应表明，组装的净速率是聚合和解聚速率的总和;聚合速率与微管数浓度和6 S微管蛋白浓度的乘积成正比;解聚速率与微管数浓度成正比。微管组装可能是通过由不同的成核和伸长步骤组成的缩聚机制发生的。微管在一系列蛋白质缔合反应中起始，其途径尚未完全阐明。通过6S微管蛋白亚基在现有微管末端的连续结合进行延伸。解聚通过6个S亚基从微管末端解离而发生。在30 ℃下测量聚合和解聚的速率常数。C为4倍。106 M-1 s-1和7 s-1。
The kinetics of [porcine brain] microtubule assembly were investigated by monitoring changes in turbidity which result from the scattering of incident light by the polymer. Assembly probably occurred by a pathway involving a nucleation phase, followed by an elongation phase as evidenced by a lag in the polymerization kinetics, followed by a psuedo 1st order exponential increase in turbidity. Analytical ultracentrifugation of solutions polymerized to equilibrium showed that 6 S tubulin was the only species detectable in equilibrium with microtubules. The elongation reaction in mixtures of 6 S tubulin and microtubule fragments demonstrated that the net rate of assembly was the sum of the rates of polymerization and depolymerization; the rate of polymerization was proportional to the product of the microtubule number concentration and the 6 S tubulin concentration; and the rate of depolymerization was proportional to the number concentration of microtubules. Microtubule assembly probably occurs by a condensation polymerization mechanism consisting of distinct nucleation and elongation steps. Microtubules are initiated in a series of protein association reactions in a pathway that was not fully elucidated. Elongation proceeds by the consecutive association of 6 S tubulin subunits onto the ends of existing microtubules. Depolymerization occurs by dissociation of 6 S subunits from the ends of microtubules. The rate constants measured for polymerization and depolymerization at 30.degree. C were 4 .times. 106 M-1 s-1 and 7 s-1, respectively.